Federal Register: June 17, 2009 (Volume 74, Number 115)
DOCID: fr17jn09-15 FR Doc E9-13800
DEPARTMENT OF THE INTERIOR
U.S. Immigration and Customs Enforcement
CFR Citation: 50 CFR Part 17
Docket ID: [Docket No. FWS-R8-ES-2008-0006; 92210-1117-0000-B4]
RIN ID: RIN 1018-AV23
NOTICE: Part II
DOCID: fr17jn09-15
DOCUMENT ACTION: Final rule.
SUBJECT CATEGORY:
Endangered and Threatened Wildlife and Plants; Revised Designation of Critical Habitat for the Quino Checkerspot butterfly (Euphydryas editha quino)
DATES: This rule becomes effective on July 17, 2009.
DOCUMENT SUMMARY:
We, the U.S. Fish and Wildlife Service (Service), are designating final revised critical habitat for the Quino checkerspot butterfly (Euphydryas editha quino) under the Endangered Species Act of 1973, as amended (Act). Approximately 62,125 acres (ac) (25,141 hectares (ha)) of habitat in San Diego and Riverside Counties, California, are being designated as critical habitat for the Quino checkerspot butterfly. This final revised designation constitutes a reduction of approximately 109,479 ac (44,299 ha) from the 2002 designation of critical habitat for the Quino checkerspot butterfly.
SUMMARY:
Interior Department, Fish and Wildlife Service
SUPPLEMENTAL INFORMATION
Background
We intend to discuss only those topics directly relevant to the
designation of critical habitat for the Quino checkerspot butterfly
under the Endangered Species Act, as amended (16 U.S.C. 1531 et seq.),
in this final revised critical habitat designation. For more
information on the taxonomy, biology, and ecology of the Quino
checkerspot butterfly, refer to the final listing rule published in the
Federal Register on January 16, 1997 (62 FR 2313), the original final
critical habitat rule published in the Federal Register on April 15,
2002 (67 FR 18356); the Recovery Plan for the Quino Checkerspot
Butterfly (Euphydryas editha quino) (Service 2003a); and the proposed
revised critical habitat designation published in the Federal Register on January 17, 2008 (73 FR 3328).
New Information on Subspecies' Description, Life History, Ecology, Habitat, and Range
We received little new information pertaining to the description, life history, distribution, ecology, or habitat of the Quino checkerspot butterfly following the 2008 proposed rule to revise critical habitat for this subspecies. The following paragraphs discuss the new information that we received, including recent information about another host plant species brought to our attention, and clarification regarding the subspecies' likely expanded range and larval diapause. Please refer to the final listing rule published in the Federal Register on January 16, 1997 (62 FR 2313), and the proposed revised critical habitat designation published in the Federal Register on January 17, 2008 (72 FR 3328), for an indepth discussion of the subspecies' biology.
In 2008, oviposition and larval development of the Quino checkerspot butterfly were recorded for the first time on a native host plant, Collinsia concolor (Chinese houses). The Quino checkerspot butterfly was observed using numerous individual C. concolor plants at multiple locations in Riverside County (Pratt 2008a, p. 1; 2008b, p. 1; 2008c, p. 1; 2008e, p. 1). Although C. concolor commonly occurs in habitats with Plantago erecta (erect plantain), P. patagonica (Patagonian plantain), and Anterrhinum coulterianum (Coulter's snapdragon) (Pratt 2001, pp. 4243; Anderson 2008, pp. 2, 3), this plant is typically found on northfacing slopes in cooler and moister microclimates than where the other host plant species occur (Pratt 2001, p. 40: Pratt 2008b, p. 1). Quino checkerspot butterflies readily oviposit on C. concolor in captivity (Pratt 2001, p. 40). Relatively heavy but previously undocumented use of C. concolor at multiple high elevation locations suggests that this host plant may become increasingly important for maintaining the Quino checkerspot butterfly population resilience as habitat conditions become warmer and drier (see below and the ``Summary of Comments and Recommendations'' section for additional discussion regarding climate change). If C. concolor is a novel host plant important for maintaining the resilience of established populations, it should also facilitate the subspecies' adaptation to environmental change that may result from climate change, including range shift (Pimm et al. 2001, p. 531; Thomas et al. 2001, pp. 577581; Parmesan 2006, pp. 644, 645, 647). For example, increased preference for a novel host plant allowed the brown argus butterfly (Aricia agestis) to use habitats that were too cool for the host plants it already used, thus permitting the butterfly species to cross previously large geographic gaps in its distribution that lacked its formerly preferred host plant (Pimm et al. 2001, p. 531; Thomas et al. 2001, pp. 577581).
Next, we did not discuss repeated diapause (the lowmetabolic rate resting stage of the life cycle) in our January 17, 2008 (72 FR 3328) proposed revision to critical habitat. One peer reviewer suggested this was an important aspect of the subspecies' biology (see comment 9 below); therefore, we are adding discussion here. Diapause occurs during the larval stage, primarily during summer and fall (Service 2003a, pp. 78). Captive rearing and observation of Quino checkerspot butterfly larvae indicate repeated diapause is relatively common (over 50 percent likelihood for the first year; Pratt 2006, p. 10) and larvae can reenter diapause up to three times (four diapause periods), but more than three diapause periods during an individual's life span is unusual (Pratt 2007a, pp. 1013).
Finally, the discussion of Edith's checkerspot butterfly
(Euphydryas editha; the Quino checkerspot butterfly is a subspecies of
Edith's checkerspot) range shift in our January 17, 2008 (72 FR 33808),
proposed revision to critical habitat requires clarification. Although
locally adapted subspecies may shift their distribution within the
middle of a greater species distribution (which appears to be occurring
with the Quino checkerspot butterfly's elevation range), the northward
latitudinal range expansion of subspecies of Edith's checkerspot
butterfly implied by Parmesan's (1996) study does not apply to the
Quino checkerspot butterfly. Because the subspecies' current northern
range edge is approximately 26 miles (mi) (42 kilometers (km)) south of
the historical range edge, any northward expansion of the Quino checkerspot butterfly's current range would
[[Page 28777]]
constitute recolonization within the subspecies' historical latitudinal
range (San Bernardino and Ventura counties; see Service 2003a, pp. 1 3).
Behavior and Population Structure
The best available scientific data indicate that most Quino checkerspot butterfly populations have some degree of metapopulation structure (Service 2003a, p. 22) and display metapopulation dynamics characterized by highly variable habitat occupancy patterns and detectability, similar to most subspecies of Edith's checkerspot butterfly (Mattoni et al. 1997, p. 111; Service 2003a, pp. 2127). Edith's checkerspot butterfly metapopulation structure is described by Ehrlich and Murphy (1987, p. 123) as the subdivision of a population into subpopulations that occupy clusters of habitat patches and interact extensively. Harrison et al. (1988, p. 360) described Edith's checkerspot butterfly metapopulation structure as: ``a set of [subpopulations] that are interdependent over ecological time.'' Although subpopulations within a metapopulation may change in size independently, the probability of a subpopulation existing at a given time is not independent, because they are linked by an extirpation and mutual recolonization process that occurs every 10 to 100 generations (Harrison et al. 1988, p. 360).
Rare highdensity events and dispersal behavior are thought to be key elements of Edith's checkerspot butterfly population dynamics that structure populations. Harrison (1989, p. 1241) found that although dispersal direction from habitat patches seemed to be random in the bay checkerspot butterfly (Euphydryas editha bayensis), dispersing butterflies were most likely to move into habitat patches when they passed within approximately 163 feet (ft) (50 meters (m)) of those habitat patches. Dispersing bay checkerspot butterflies tended to remain in habitat patches where existing butterfly density was low (Harrison 1989, p. 1241). Bay checkerspot butterfly occupancy patterns also suggested that unoccupied habitat separated from occupied habitat by hilly terrain was less likely to be colonized than habitat separated by flat ground (Harrison 1989, p. 1241).
Harrison (1989, pp. 1241, 1242) concluded that the longterm habitat recolonization pattern of her study population was likely due to relatively large numbers of bay checkerspot butterflies having dispersed from persistent ``source'' subpopulations. Harrison (1989, p. 1239) found bay checkerspot butterfly habitat within 0.6 mi (1 km) of a source subpopulation is 100 percent likely to be colonized by immigrants from the source subpopulation. Harrison (1989, p. 1239) also recaptured a significant number of individuals in habitat 0.6 mi (1 km) from their release point. Over a 5day period, 5 percent of butterflies released at a single location were recaptured in an isolated ``target habitat patch'' 0.6 mi (1 km) away (Harrison 1989, p. 1239). Assuming mostly random initial movement direction from the release location at such a great release distance from the recapture site (Harrison 1989, p. 1241), many individuals likely traveled similar or further distances outside the study area.
High habitat colonization rates probably only occur during rare outbreak years, when relatively high local densities combine with favorable establishment conditions in unoccupied habitat (Harrison 1989, p. 1242). These rare outbreak events are also thought to play a crucial role in Quino checkerspot butterfly metapopulation resilience and the subspecies' survival (Murphy and White 1984, p. 353; Ehrlich and Murphy 1987, p. 127). Therefore, protection and management of source subpopulations likely to provide immigrants to unoccupied habitat are required for conservation of the Quino checkerspot butterfly (Service 2003a, pp. 22, 2526, 35, 94).
Longdistance dispersal has been documented in the Edith's checkerspot butterfly, and dispersal propensity is affected by local environmental conditions and subspecies' adaptation. White and Levin (1981, pp. 348357) conducted the only markrecapture movement study that included the Quino checkerspot butterfly. White and Levin (1981, pp. 348357) studied withinhabitat patch movement of the Quino and bay checkerspot butterfly subspecies in southern San Diego County (male bay checkerspots were released into Quino checkerspot butterfly habitat late in the flight season when offspring survival was not considered possible). They concluded that patterns of dispersal changed ``dramatically'' from year to year (White and Levin 1981, p. 348), and the Quino checkerspot butterfly was less sedentary than the more heavily studied bay checkerspot butterfly (White and Levin 1981, p. 105). Although the average markrecapture distance traveled by a Quino checkerspot butterfly in White and Levin's (1981, p. 349) study was only 305 ft (93 m), movement records were limited to the local study area. White and Levin (1981, p. 349) stated, ``It seems likely from the lower rate of return in 1972 and from the observed pattern of out dispersal that many marked animals dispersed beyond the area covered by our efforts that year. This outdispersal might make the value for average distance [traveled] in 1972 an underestimate of significant magnitude.'' Longdistance movement in the bay checkerspot butterfly has been documented as far as 4 mi (6.4 km) (Murphy and Ehrlich 1980, p. 319) and 3.5 mi (5.6 km) (Harrison 1989, p. 1239).
The above information indicates that, although Edith's checkerspot butterflies appear to be capable of longdistance dispersal, their movement propensity is variable and driven by external environmental factors. By extension, contiguous habitat between two butterflies observed 1.2 mi (2 km) from each other is within reasonable flight distance of both individuals and should be considered part of a shared home range. Therefore, based on typical longdistance recapture records, we conclude that Quino checkerspot butterflies observed within approximately 1.2 mi (2 km) of each other in contiguous habitat belong to the same population, and contiguous habitat within at least 1.2 mi (2 km) of an observed Quino checkerspot butterfly is part of that individual's population distribution.
Delineating Population Distributions
The best scientific data available to us for use in delineating
Quino checkerspot butterfly population distributions consist of
geographic information system (GIS)based habitat information,
subspecies observation locations, and subspecies movement data from
markreleaserecapture studies. Populationscale occupancy (a
population distribution) is defined as all areas used by adults during
the persistence time of a population (years to decades; Service 2003a,
p. 24). Focused distribution studies over multiple years are required
to quantify Quino checkerspot butterfly population distributions.
Therefore, the Recovery Plan described Quino checkerspot butterfly
population locations in terms of ``occurrence complexes'' (Service
2003a, p. 35), which were simple nonhabitatbased estimators of
population distributions (wellmixed or metapopulation structure) and
population membership of observed butterflies. Occurrence complexes are
mapped in the Recovery Plan using a 0.6mi (1km) movement radius from
each butterfly observation and may be based on the observation of a
single individual. Occurrence locations within at least 1.2 mi (2 km)
of each other are considered to be part of the same occurrence complex, as these occurrences are proximal enough that
[[Page 28778]]
the observed butterflies were likely to have come from the same population (Service 2003a, p. 35).
Occurrence complexes may expand due to new butterfly observations, or contract due to habitat loss (for example, mapped occurrence complexes were limited by development, see Service 2003a p. 78). According to recorded Edith's checkerspot butterfly movement distances (Gilbert and Singer 1973, pp. 65, 66; Harrison et al. 1988, pp. 367 380; Harrison 1989, pp. 1239, 1240), occurrence complexes appropriately describe the area within which a significant proportion of the habitat patch associated with individual observed butterflies is likely to occur (see above discussion and Service 2003a, p. 35).
Some occurrence complexes were identified in the Recovery Plan
(Service 2003a, p. 35) as ``core.'' Core occurrence complexes are those
that appear to be centers of population density based on geographic
size, number of reported individuals, repeated observations, and
evidence of reproduction. Such population density centers are likely to
contain ``source'' subpopulations for a Quino checkerspot butterfly
metapopulation (Murphy and White 1984, p. 353; Ehrlich and Murphy 1987,
p. 125; Mattoni et al. 1997, p. 111; Service 2003a pp. 2526), or
``source'' populations for megapopulations (a group of populations also
dependent on one another, but on a time scale greater than that of
subpopulations; Service 2003a, pp. 21, 24, 2526). A source
subpopulation is one in which the emigration rate typically exceeds the
immigration rate, and is thus a source of colonists for unoccupied
habitat patches (Service 2003a, p. 166). Therefore, for the purposes of
critical habitat designation, we defined a core occurrence complex as
an area where at least two of the following criteria apply: (1)
Surveyors reported 50 or more adults during a single survey at least
once; (2) immature life stages were recorded; or (3) the geographic
area within the occurrence complex (within 0.6 mi (1 km) of subspecies
occurrences) is greater than 1,290 ac (522 ha; the size of the smallest
Core Occurrence Complex where reproduction has been documented on
multiple occasions and there are historical collection records indicating longterm resilience).
Status and Local Distribution of Populations in Riverside County
Occurrence data collected in Riverside County since publication of the Recovery Plan in 2003 resulted in expansion of all core occurrence complexes and merging of some core occurrence complexes with noncore occurrence complexes (see discussion below). In particular, occurrence data collections in Riverside County since listing (62 FR 2313; January 16, 1997) have continued almost annually to expand the known elevation limit of the subspecies' range (Pratt et al. 2001, pp. 169171; Service 2003a, p. 44; Goldberg 2005, pp. 8, 9; Pratt and Pierce 2005, pp. 45, 1112; Pratt 2005, p. 1; San Bernardino National Forest (SBNF) GIS database). The Bautista Road Occurrence Complex (described as noncore in the Recovery Plan) is in a relatively highelevation valley east of Temecula and north of the community of Anza, California. Multiple new observations have occurred within and around the Bautista Road Occurrence Complex (AMEC 2004, p. 6; Mooney Jones and Stokes 2005, p. 10). Consistent with criteria outlined in the Recovery Plan (Service 2003a, p. 35) and above, we now consider the Bautista Road Occurrence Complex to be a Core Occurrence Complex.
From 2004 to 2006, multiple new occurrence locations were also reported in the community of Anza, and north and northwest of the Bautista Road Core Occurrence Complex, Pine Grove Noncore Occurrence Complex, and Lookout Mountain Noncore Occurrence Complex. These new Noncore Occurrence Complexes are: (1) Cave Rocks within the community of Anza, just north of the intersection of Bautista Road and State Route (SR) 371 (AMEC 2004, p. 9); (2) Quinn Flat located between Fobes Ranch Road and Morris Ranch Road northeast of Quinn Flat and SR 74 (Pratt and Pierce 2005, pp. 45, 1112; Pratt 2005, p. 1; SBNF GIS database); (3) Horse Creek adjacent to Bautista Road, southeast of Bautista Spring (AMEC 2004, p. 6; Malisch 2006, p. 1); and (4) North Rouse Ridge located on Rouse Ridge in the hills east of Bautista Canyon, near where Bautista Road exits the foothills (Goldberg 2005, pp. 8, 9; SBNF GIS database ). None of these new observation locations met two or more of the criteria needed to categorize them as a core occurrence complex. However, these new Noncore Occurrence Complexes resulted in: (1) An increased number of known occupied areas near the community of Anza; (2) an expansion of the subspecies' known geographic range at its northeastern extreme (where it had not been previously recorded, but within historical latitudinal limits of the subspecies' distribution); and (3) an increase in the subspecies' known elevation range (Service Geographic Information Systems (GIS) database).
Recent monitoring information indicates the Tule Peak and Silverado Core Occurrence Complexes described in the Recovery Plan (Service 2003a, p. 44) are part of a single highdensity population distribution supporting periodic density increases, similar to historical outbreak events (Service 2003a, p. 29), such as the 1977 outbreak in San Diego County reported by Murphy and White (1984, p. 351) (see also Ehrlich and Murphy 1987, p. 127; Carlsbad Fish and Wildlife Office (CFWO) 2004; Pratt 2004, p. 17). Occupancy in the Silverado Core Occurrence Complex was first documented in 1998 (Pratt 2001, p. 17), followed by the discovery of hundreds of Quino checkerspot adults in 2001 within the Tule Peak Core Occurrence Complex (TeraCor 2002, p. 14). Such reports of hundreds of adults in the Tule Peak Core Occurrence Complex were unprecedented since the 1970s, because, typically, five or fewer individuals are reported during projectbased surveys (Service GIS database).
In 2004, following a year of aboveaverage host plant density in the Anza area (CFWO 2004), another Quino checkerspot butterfly outbreak event occurred with even higher abundance than was reported in 2001. An estimated 500 to 1000 adult Quino checkerspot butterflies were reported from the Silverado Core Occurrence Complex in a single day in 2004 (Anderson 2007, p. 1; CFWO 2004; Pratt 2004, pp. 16, 17). Additionally, more than 30 new occurrence locations with high adult densities were reported in 2004 in the vicinity of Tule Peak Road (92 to more than 100 observations in a single day) south of the Cahuilla Band of Mission Indians of the Cahuilla Reservation, California (Cahuilla Band of Indians), and the community of Anza (Osborne 2004, pp. 16, 810; Anderson 2007, p. 5; CFWO 2004; Osborne 2007, pp. 1316). Based on these new observations, it is appropriate to merge the Tule Peak (core), Silverado (core), and Southwest Cahuilla (noncore) occurrence complexes to form a single, expanded Tule Peak/Silverado Core Occurrence Complex. This population contains higher densities and likely produces more emigrants than any other population within the subspecies' range.
The best available scientific data (including recent outbreaks in
the closest core occurrence complex) suggest the new Bautista Road Core
Occurrence Complex supports ongoing range shift for the Quino
checkerspot butterfly upslope in elevation, and other noncore
occurrence complexes north of the community of Anza may be the result of recent colonization events.
[[Page 28779]]
Parmesan (1996, pp. 765766) concluded that the average (not actual)
position of known Edith's checkerspot butterfly populations had shifted
north and up in elevation, likely due to a warming, drying climate
(conclusion supported by the technical recovery team, Service 2003a,
pp. 64, 65). Parmesan (1996, pp. 765766) compared the distribution of
the Edith's checkerspot butterfly in the early part of the 20th century
to its distribution from 1994 to 1996 using historical records and
field surveys. This study identified a rangewide pattern of local
Edith's checkerspot butterfly extirpations and noted that 80 percent of
historically recorded populations in the southern part of the range
were extinct at the time of the recensus in the mid1990s (with the
majority being Quino checkerspot butterfly populations). In contrast,
historically recorded Edith's checkerspot butterfly populations in the
midlatitude part of the species' range experienced only 40 percent
extirpations, and the extirpation rate in the northern part was as low
as 20 percent (Parmesan 1996, pp. 765766). Fewer than 15 percent of
the Edith's checkerspot butterfly extirpations occurred in the highest
elevation band (above 7,874 ft (2,400 m)) (Parmesan 1996, pp. 765766).
Parmesan (1996, pp. 765766) concluded that this pattern of extirpation indicates contraction of the southern boundary of the Quino checkerspot butterfly's overall distribution by almost 100 mi (160 km) and a shift in the average location of an Edith's checkerspot butterfly occurrence northward by 57 mi (92 km). A parallel elevation gradient in extirpations shifted the mean location of Edith's checkerspot butterfly populations upward by 407 ft (124 m). A breakpoint in the pattern of extirpations occurred at approximately 7,874 ft (2,400 m), with about 40 percent of all populations below the breakpoint recorded as extirpated in suitable habitats, while less than 15 percent were extirpated above the breakpoint. This pattern matched trends in snowpack dynamics in the Sierra Nevada (where the highelevation populations are found) over the same period as the butterfly study, with significant trends toward lighter snowpack and earlier melt date below 7,874 ft (2400 m), and heavier snowpack and a (nonsignificant) trend toward later melt date above 7,874 ft (2400 m) (Johnson et al. 1999, pp. 6370). This range shift closely matched shifts in mean yearly temperature (Parmesan 1996, pp. 765766; Karl et al. 1996, pp. 279292). Parmesan's study found extirpations to be most common at lower elevations and latitudes, and the Quino checkerspot butterfly's range includes both the lower elevation and lower latitude range extremes for Edith's checkerspot butterfly. Therefore, the Quino checkerspot butterfly may be the subspecies of Edith's checkerspot experiencing the greatest effects associated with changes in climate.
Studies have demonstrated a correlation of population distribution and phenology changes with climate change for many other butterfly and insect species in California and around the world (Parmesan et al. 1999, p. 580; Forister and Shapiro 2003, p. 1130; Parmesan and Yohe 2003, pp. 38, 39; Karban and Strauss 2004, pp. 251254; Thomas et al. 2004, pp. 146147; Osborne and Ballmer 2006, p. 1; Parmesan 2006, pp. 646647; Thomas et al. 2006, pp. 415416). Metapopulation viability analyses of other endangered nymphalid butterfly species indicate that current climate trends pose a major threat to butterfly metapopulations by reducing butterfly growth rates and increasing subpopulation extirpation rates (Schtickzelle and Baguette 2004, p. 277; Schtickzelle et al. 2005, p. 89). Most recently, Preston et al. (2008, p. 2506) incorporated biotic interactions into niche models to predict suitable habitat for species under the range of climate conditions predicted for southern California in recent climate change models (see also Hayhoe et al. 2004, pp. 1242212427; IPCC 2007, p. 9).
Preston et al. (2008, p. 2508) found that Quino checkerspot butterfly habitat decreased and became fragmented under altered climate conditions based on the climateonly model. For increasing temperatures and 110 percent precipitation, there was a shift in habitat to the eastern portion of the currently occupied range corresponding with an upslope movement of the species to higher elevations in adjacent mountains (Preston et al. 2008, p. 2508). The abioticbiotic model (betterperforming model) predicted 98 to 100 percent loss of suitable Quino checkerspot butterfly habitat when the temperature increased 1.7 and 2.8 [deg]C (1.5 and 2.5 [deg]F) and when the precipitation was 50 percent or 150 percent of current levels (Preston et al. 2008, p. 2508). An increase of less than 1 [deg]C (1.1 [deg]F) with no change in current precipitation resulted in no predicted habitat shift, although there was an eastward (upslope) shift within the current distributional footprint at 110 percent precipitation (Preston et al. 2008, p. 2508). Similar climate response patterns in modeled habitat and related and cooccurring insect species further support the validity of Parmesan's (1996, pp. 765766) Quino checkerspot butterfly observations and conclusions (Preston et al. 2008, pp. 2511, 2512). Therefore, the hypothesis of range shift driven by changing climate and precipitation patterns occurring in the foothills north of the community of Anza is well supported by the best available scientific information.
Documented environmental changes that have already occurred in California (Ehrlich and Murphy 1987, p. 124; Croke et al. 1998, pp. 2128, 2130; Davis et al. 2002, p. 820; Breshears et al. 2005, p. 15144), future drought predictions for the state (such as Field et al. 1999, pp. 810; Brunell and Anderson 2003, p. 21; Lenihen et al. 2003, p. 1667; Hayhoe et al. 2004, p. 12422; Breshears et al. 2005, p. 15144; Seager et al. 2007, p. 1181) and North America (IPCC 2007, p. 9), and extirpation of Edith's checkerspot butterfly populations following extreme climatic events (Ehrlich et al. 1980, pp. 101105; Singer and Ehrlich 1979, pp. 5360; Singer and Thomas 1996, pp. 939) model and predict that prolonged drought and other environmental changes related to changing climate patterns will continue into the near future, and these changes may affect Quino checkerspot butterfly populations. Thomas et al. (2004, p. 147) estimated that 29 percent of species in scrublands (habitat for the Quino checkerspot butterfly) face eventual extinction, and 7 (with dispersal) to 9 (without dispersal) percent of butterfly species in Mexico will become extinct (midrange climate predictions; Thomas et al. 2004, p. 146). During drought conditions in 2007, surveyors noted that, for the first time since the subspecies was listed, no Quino checkerspot butterflies were observed during Riverside County surveys or core occurrence complex monitoring (CFWO 2007). Therefore, recent subspecies field evidence corresponds with the hypothesis that changing environmental conditions throughout the subspecies' range is resulting in reduced densities at lower elevations.
Maintenance of the Tule Peak/Silverado and Bautista Road core
occurrence complexes and habitat connectivity to higher elevation non
core occurrence complexes is needed to prevent an increase in the
subspecies' extinction probability and support range shift resulting
from environmental changes due to changing climate patterns (Service
2003a, pp. 46, 47; Osborne 2007, pp. 910). The Anza/Mount San Jacinto
foothills area (in and adjacent to the Bautista Road Core Occurrence Complex) is proximal to what is likely the highest density
[[Page 28780]]
population that produces the most emigrants within the subspecies'
range (Tule Peak/Silverado Core Occurrence Complex) and supports the
greatest elevation gradient within the extant range of the Quino
checkerspot butterfly. Regardless of rangeshift dynamics, this area
likely supports the most resilient populations within the subspecies'
current range (see above discussion of recent observations in this
area). As discussed above, evidence of range shift resulting from
environmental changes due to changing climate patterns includes the
following: (1) Parmesan's (1996) subspeciesspecific study; (2) Preston
et al.'s (2008, pp. 25012505) subspeciesspecific habitat model
predictions; (3) recent documented Quino checkerspot butterfly outbreak
events (discussed above); (4) the complete lack of Quino checkerspot
butterfly observations in Riverside County during 2007 monitoring; (5)
documented drought conditions and the likelihood that recurrent drought
conditions will persist into the near future (see above discussion);
and (6) the discovery of new noncore occurrence complexes in the most
northern, highest elevation habitat areas (see above discussion of
recent observations in this area). Parmesan's (1996, pp. 765766)
rangeshift statistics and Preston et al.'s habitat models (2008, pp.
25012505) predict the following Quino checkerspot butterfly population
changes: (1) Declines in, and loss of, the southernmost and lowest
elevation populations (lowest elevation range edge already retracted
likely due to a combination of development and the 1980s drought),
especially in drier areas where rainfall is most variable (such as
southwest Riverside County; Anderson 2000, pp. 3, 6); (2) increases in
the density in the highest elevation populations, especially in wetter
areas (such as the Anza area; Service 2003a, p. 44); and (3)
establishment of new populations higher in elevation where range shift
is least impeded by habitat loss due to landuse changes (such as the
Mount San Jacinto foothills; Service GIS database and satellite imagery).
The highest elevation core occurrence complexes (Tule Peak/ Silverado and Bautista Road) also support the highest (cooccurring) diversity of host plant species (Plantago patagonica, Antirrhinum coulterianum, Collinsia concolor, Cordylanthus rigidus (rigid bird's beak), and Castilleja exserta (purple owl'sclover)) within the range of the Quino checkerspot butterfly, a factor known to increase population resilience (Service 2003a, p. 17) and mitigate the effects of climate extremes on Edith's checkerspot butterfly populations (Hellman 2002, p. 925). Therefore, prudent design of reserves and other managed habitats near the community of Anza, where the subspecies' range is likely expanding upslope in elevation, should include landscape connectivity to other habitat patches and ecological connectivity (habitat patches linked by dispersal areas; Service 2003a, p. 162) to accommodate such range shift (Service 2003a, p. 64). Status and Local Distribution of Populations in San Diego County
New Quino checkerspot butterfly observations (Service GIS database) between occurrence complexes identified in the Recovery Plan have resulted in merging of the Otay Valley (core), West Otay Mountain (core), Otay Lakes (core), Proctor Valley (noncore), Dulzura (non core), and Honey Springs (noncore) occurrence complexes into a single, expanded Otay Mountain Core Occurrence Complex. This merging of occurrence complexes in the Otay area was anticipated in the Recovery Plan, as authors noted that occupied habitat in the vicinity of Otay Lakes and Rancho Jamul appeared to be an area of key landscape connectivity for all subpopulations in southwest San Diego County (Service 2003a, pp. 53, 54).
Several widely distributed new observation locations have been reported since 2002 in central San Diego County (Dudek 2005, p. 1; Faulkner 2005, p. 1; Tierra Environmental Services 2005, p. 4), and between Interstate 8 and State Route 94 (TRC 2008, pp. 3338) resulting in four new San Diego County noncore occurrence complexes (Fanita Ranch, Sycamore Canyon, and Mission Trails Park, and Barrett Lake). The proximity of these occurrence complexes to historical collection locations (compare abovecited documents to Service 2003a, p. 3) indicates recent detections may reflect shortterm increases in population densities; however, it is not likely that increasing densities will persist, given observed and predicted environmental shifts associated with changing climate patterns (see above discussion), increasing nonnative plant invasion, and the relative isolation of these noncore occurrence complexes from core occurrence complexes. Therefore, the best available data indicate that these new observation locations may be the result of surveys in areas not previously searched and likely represent residual, relatively low density populations experiencing a longterm trend of decreasing abundance.
Multiple new Quino checkerspot butterfly observation locations have been reported in southcentral San Diego County since 2002 east of the community of Campo (Dicus 2005a, pp. 12; b, p. 1; PSBS 2005a, p. 18; 2005b, p. 26; O'Conner 2006, pp. 24). This cluster of occurrence complexes near Campo is over 7 mi (11 km) from the closest previously identified core occurrence complex near the community of Jacumba (Service 2003a, p. 52; Service GIS satellite imagery and database) and over 12 mi (19 km) from the Tecate (noncore) Occurrence Complex (Service 2003a, p. 47; Service GIS satellite imagery and database). We believe the Quino checkerspot butterfly distribution east of the community of Campo is underdocumented because of: (1) The small number of surveys conducted in this area (Service survey report files); (2) the existence of contiguous habitat between observation locations (Service GIS vegetation database and satellite imagery); and (3) the presence of relatively high densities of Antirrhinum coulterianum and Collinsia cocolor host plants in occupied habitat (Bureau of Indian Affairs 1992, p. c5; Allen and Kurnow 2005, pp. 10, 1316; Dicus 2005a, pp. 12; b, p. 1; PSBS 2005a, p. 18; 2005b, p. 26; O'Conner 2006, pp. 14, Science Applications International Corporation 2006, pp. 33, 34, 37).
Methods used in the Recovery Plan (Service 2003a, p. 35) to determine membership of occurrence locations in an occurrence complex using the sparse available occurrence data would likely underestimate the population distribution associated with this obviously independent population near the communities of La Posta and Campo. Therefore, although not quite proximal enough to be considered a single occurrence complex based on overlapping 0.6mi (1km) movement distances (Service 2003a, p. 35), we consider this cluster of new observations near Campo to belong to a single new La Posta/Campo Core Occurrence Complex.
Quino checkerspot butterflies were recently observed in a new
location in southeast San Diego County that resulted in expansion of
the Jacumba Occurrence Complex (Essex and Osborne 2005, p. 82).
Additionally, data collected from the Jacumba Occurrence Complex since
publication of the Recovery Plan led us to reclassify the Jacumba
complex as a core occurrence complex. The Jacumba Occurrence Complex
was not classified as a core occurrence complex in the Recovery Plan
(Service 2003a, p. 52) due to its relatively small geographic size. [[Page 28781]]
However, adult Quino checkerspot butterflies are consistently observed
in the area, even during drought years and under difficult survey
conditions (high winds) (CFWO 20022007; Klein 2007, p. 1). An
estimated 50 individuals were observed in a single day near Jacumba
Peak (Pratt 2007b, p. 1). Furthermore, reproduction was documented in
the Jacumba Occurrence Complex in 1998 and again in 2004 (Pratt 2007c,
p. 1). Therefore, given ongoing documentation of occupancy (Service
2004, 2005, 2008), documented reproduction over multiple years (Pratt
2007c, p. 1), reported observations of large numbers of individuals
(50; Pratt 2007b, p. 1), and an increased occurrence complex area
(approximately 522 ac (1,290 ha)), we now consider the Jacumba
Occurrence Complex to be a core occurrence complex associated with what appears to be a relatively resilient population.
The prediction that drought conditions are likely to continue into the near future (Service 2003a, pp. 63, 64; see above discussion) highlights the importance of conserving populations locally adapted to drier climates and diverse habitat types (Service 2003a, p. 76). The La Posta/Campo and Jacumba core occurrence complex habitats are warmer and drier than the Otay Mountain Core Occurrence Complex and differ substantially in other habitat characteristics (Service 2003a, pp. 36 54; O'Conner 2006, p. 4). Therefore, maintenance of these core occurrence complexes is essential for recovery and survival of the Quino checkerspot butterfly in San Diego County. These new core occurrence complexes were also the only complexes in the subspecies' southern range not affected by the 2003 and 2005 fires. Therefore, new information indicates the La Posta/Campo and Jacumba Core Occurrence Complexes contribute significantly to reducing the subspecies' extinction probability.
Previous Federal Actions
The Homebuilders Association of Northern California, et al., filed suit against the Service in March 2005 challenging the merits of the final critical habitat designations for several taxonomic entities, including the Quino checkerspot butterfly. A settlement was reached in March 2006 that required the Service to reevaluate five final critical habitat designations, including the Quino checkerspot butterfly. The settlement stipulated that proposed revisions to the Quino checkerspot butterfly designation would be submitted for publication to the Federal Register by December 7, 2007, and final revisions would be submitted by December 7, 2008. In accordance with a courtapproved amendment to the settlement agreement, dated December 5, 2007, the proposed revisions were published in the Federal Register on January 17, 2008 (73 FR 3328). Subsequently, a courtapproved amendment to the settlement agreement dated November 6, 2008, stipulated the Service deliver the final revised critical habitat designation to the Federal Register by June 6, 2009. For more information on previous Federal actions concerning the Quino checkerspot butterfly, refer to the proposed revisions to critical habitat published in the Federal Register on January 17, 2008 (73 FR 3328).
Summary of Comments and Recommendations
We requested written comments from the public on the proposed rule to revise critical habitat for the Quino checkerspot butterfly during two comment periods. The first comment period opened with the publication of the proposed rule in the Federal Register on January 17, 2008 (73 FR 3328), and closed on March 17, 2008. The second comment period opened with the publication of the notice of availability of the Draft Economic Analysis (DEA) in the Federal Register on December 19, 2008 (73 FR 77568) and closed on January 20, 2009. During both public comment periods, we contacted appropriate Federal, State, and local agencies; scientific organizations; and other interested parties and invited them to comment on the proposed rule to revise critical habitat for this subspecies and the associated DEA. During the comment periods, we requested all interested parties submit comments or information related to the proposed revisions to critical habitat, including (but not limited to) the following: unit boundaries; species occurrence information and distribution; land use designations that may affect critical habitat; potential economic effects of the proposed designation; benefits associated with critical habitat designation; areas proposed for designation and associated rationale for the non inclusion or considered exclusion of these areas; and methods used to designate critical habitat.
During the first comment period, we received 17 comment letters (15 letters addressing the proposed revision of critical habitat, and 2 letters from a single commenter that were not related to proposed revisions to critical habitat): two from peer reviewers, three from Federal agencies, six from representatives of five Native American tribes, and six from public organizations or individuals. During the second comment period, we received nine comments addressing the proposed critical habitat designation and the DEA. Of these latter comments, two were from peer reviewers, two from Federal agencies, two from Native American tribes, and three from public organizations or individuals. We did not receive any requests for a public hearing. Peer Review
In accordance with our Policy for Peer Review in Endangered Species Act Activities, published on July 1, 1994 (59 FR 34270), we solicited expert opinions from 10 knowledgeable individuals with scientific expertise that included familiarity with the subspecies, the geographic region in which it occurs, and conservation biology principles. Four peer reviewers submitted responses. They provided additional information, clarifications, and suggestions that we incorporated into the rule to improve the final revised critical habitat rule.
We reviewed all comments received from the peer reviewers and the public for substantive issues and new information regarding the designation of critical habitat for the Quino checkerspot butterfly. All comments are addressed in the following summary and incorporated into the final rule as appropriate.
Peer Reviewer Comments
Comment 1: One peer reviewer stated they had recently communicated with residents in and around the community of Anza and concluded that residents moved to this area based on an appreciation of nature and the outdoors. The peer reviewer suggested the Service should inform residents on how to improve Quino checkerspot butterfly habitat. The peer reviewer also asserted that residents of Anza are suspicious of government intervention and value their personal freedom more than endangered species preservation. The peer reviewer expressed willingness to help organize a meeting that would provide private landowners from Anza with information on how to preserve the subspecies. The peer reviewer concluded that, because of their appreciation for nature, Anza residents would be willing to improve Quino checkerspot butterfly habitat on their lands, but that willingness would be decreased by critical habitat designation; therefore, we should exclude any lands in the vicinity of Anza from our revised critical habitat designation.
[[Page 28782]]
Our Response: We agree that species conservation benefits provided by landowner partnerships to conserve federally listed species may minimize the conservation benefits of designating privately owned lands as critical habitat, and we appreciate the peer reviewer's interest in participating in such an endeavor. We encourage the peer reviewer to continue to communicate and work with residents of Anza (Units 6 and 7) to conserve the Quino checkerspot butterfly, within and outside of areas that meet the definition of critical habitat. Should residents of Anza or surrounding areas be interested in developing a partnership to conserve the Quino checkerspot butterfly, Service biologists are available to participate and provide information on such partnership programs as Safe Harbor Agreements for private landowners. Safe Harbor Agreements provide assurances to landowners under the Act that no additional future regulatory restrictions will be imposed if conservation practices on their land attract or perpetuate federally listed species. At this time, there is no formal partnership between the peer reviewer, residents of Anza, or the Service to conserve the Quino checkerspot butterfly or its habitat, other than the Western Riverside County Multiple Species Habitat Conservation Plan (Western Riverside County MSHCP; Dudek and Associates, Inc. 2003), under which some areas south of the community of Anza are already excluded (see ``Application of Section 4(b)(2) Other Relevant Impacts
Conservation Partnerships'' section below).
Comment 2: One peer reviewer observed Quino checkerspot butterflies ``by the 100s'' near the community of Anza during a subspecies ``outbreak.'' The peer reviewer observed several unique behaviors in the Anza area in 2004 (they stated 2006 but our records indicate 2004), including a female deep within a stand of Adenostoma sparsifolium (redshank), likely searching for sites to deposit eggs. Despite extensive survey efforts prior to this 2004 observation, the peer reviewer had never observed Quino checkerspot butterflies in dense A. sparsifolium, and previously assumed the subspecies never went into such areas.
The peer reviewer asserted that Quino checkerspot butterflies move many more miles during periods of high subspecies density than observed during average density years. The peer reviewer hypothesized that, under certain environmental conditions, hormonal changes could be responsible for the behavioral changes he observed. The peer reviewer also noted that, during historical ``outbreaks,'' Quino checkerspot butterflies were observed in downtown San Diego. The peer reviewer hypothesized this movement behavior may be unique to the Quino checkerspot butterfly among Edith's checkerspot subspecies, and movement between populations may be important for replacing extirpated populations and maintaining gene flow between extant populations. Finally, the peer reviewer stated a lack of conserved ``intermediate habitat'' between populations may cause extirpation of populations and, eventually, subspecies extinction.
Our Response: We were aware of the peer reviewers' observations and had incorporated those observations into our analysis (for example, inclusion of closedwoody canopy areas in Primary Constituent Element (PCE) 2; see ``Primary Constituent Elements'' section below). We appreciate the peer reviewers' insights and contributions to our knowledge of the subspecies' biology.
Although we are not aware of any recorded longdistance movements for the Quino checkerspot butterfly, the one withinhabitat patch movement study completed at Otay Lakes (White and Levin 1981, pp. 350, 355) concluded that Quino checkerspot butterflies were ``less sedentary'' than bay checkerspot butterflies and may disperse greater distances. Plasticity and variability of movement behavior is typical among Euphydryas spp. (Service 2003a, pp. 1013), as demonstrated by the historical observations of Quino checkerspot butterflies in downtown San Diego that were cited by the peer reviewer. These observations indicate that, when many individuals were dispersing during at least one unusually highdensity historical event, developed areas did not prevent such movement. Therefore, because the best available scientific information supports the need for within population movement areas, but does not support the necessity or identification of ``intermediate habitat'' for dispersal between populations, we included only movement areas within habitatbased population distributions in our critical habitat designation (see ``Criteria Used To Identify Critical Habitat'' section below).
Comment 3: Based on personal experience maintaining captive populations, the peer reviewer asserted that Quino checkerspot butterfly populations are more susceptible to inbreeding depression than most other butterfly species. The peer reviewer stated that, when closely related Quino checkerspot butterfly individuals are bred ``for some time'' without outcrossing, they observe greater egg and larval mortality than generally observed in butterfly species in the family Lycaenidae (coppers and blues). The peer reviewer concluded the Service should consider assisting genetic exchange between populations that appear to be losing genetic variability, such as the small population in Unit 1 (Warm Springs Creek Core Occurrence Complex). The peer reviewer stated they suspected low genetic diversity was a primary cause of the Gavilan Hills/Lake Mathews population extirpation.
Our Response: We recognize that the increased mortality observed during captive rearing could be indicative of inbreeding depression; however, we have no basis upon which to determine whether or not populations of the Quino checkerspot butterfly outside of a laboratory setting experience inbreeding depression. We agree with the commenter's recommendation that an evaluation of the population genetics of this butterfly could assist its recovery, and we discussed the possible effects of genetic drift and inbreeding depression in the listing rule for the Quino checkerspot butterfly (Service 1997, pp. 23192320). We appreciate this information; however, we do not believe it is relevant to our final revised critical habitat designation.
Comment 4: One peer reviewer stated that populations in Units 6 and 7 near the community of Anza are ``continuous and not actually separate.'' The peer reviewer indicated that extensive suitable habitat exists between these two units (especially in Terwilliger Valley), which is probably occupied by the Quino checkerspot butterfly. Additionally, the peer reviewer noted there are multiple public land parcels in the area and some have extensive stands of the food plant Antirrhinum coulterianum.
Our Response: While landscape connectivity does exist between Units
6 and 7 in the Anza area, and some occupied habitat exists in the area
that was not included in our proposed revised critical habitat units
(Cave Rocks and Cahuilla Creek noncore occurrence complexes), habitat
within the community of Anza is fragmented, and large areas of
landscape connectivity occur outside our mapped habitatbased
population distributions (that is, not occupied). Our habitatbased
population distributions are the best estimate of population occupancy
based on the best available scientific data. Because the habitatbased
population distributions are not continuous, we must assume the
Bautista Road and Tule Peak/Silverado core occurrence complexes and the Cave Rocks and Cahuilla Creek noncore
[[Page 28783]]
occurrence complexes are not part of a single population. We determined
that habitat captured by the core occurrence complex habitatbased
population distributions in Units 6 and 7 provide the PCEs laid out in
the appropriate quantity and spatial arrangement essential to the
conservation of the subspecies. Our criteria used to identify critical
habitat focused on core occurrence complex habitatbased population
distributions designed to capture all habitats likely to support
resilient metapopulations, including those likely to support local
source or mainland populations (also called subpopulations) and
movement areas between habitat patches required for metapopulation
resilience (see Service 2003a pp. 163, 165166 for term definitions).
Finally, Terwilliger Valley is not located between Units 6 and 7, it is
located east of Unit 6 (Unit 7 is north). Please see ``Criteria Used To
Identify Critical Habitat'' section below for further discussion.
Comment 5: Two peer reviewers stated the Bautista Road Core Occurrence Complex was probably occupied at the time of listing, but occupancy was not documented because that area was not adequately surveyed at that time. The second peer reviewer asserted that, prior to 1998, butterfly experts did not know much about habitats near the community of Anza, and all highelevation observations were thought to be dispersing individuals because the only known primary host plant, Plantago erecta, did not occur above 3,000 ft (914 m) in elevation. The second peer reviewer noted that Dr. John Emmel observed a Quino checkerspot butterfly [near the community of Anza] along Bautista Road in the 1970s. The second peer reviewer also suggested that surveys be conducted in higher elevation areas where the Quino checkerspot butterfly may eventually colonize to determine if the subspecies is absent and to document possible establishment of new populations in the future. Finally, the second peer reviewer asserted that movement of this subspecies into new areas will not be easy because of inbreeding depression (see Comment 3 above), and suggested the subspecies may move by local and gradual movements and eventually expand into higher elevation sites.
Our Response: We agree that it is possible that the Bautista Road Core Occurrence Complex was occupied at the time of listing; however, we have insufficient documentation to support that assertion. We received subsequent confirmation of Dr. Emmel's historical Quino checkerspot butterfly observation referenced by the peer reviewer. Dr. Emmel (2008, p. 1) stated that, on March 26, 1988, he observed what appeared to be a single female Quino checkerspot butterfly at the intersection of Bautista Road and Tripp Flats Road at 3,840 ft (1,170 m) elevation. Dr. Emmel (2008, p. 1) further stated that this historical observation within the Bautista Road Core Occurrence Complex may have been of a dispersing individual from a more southern population, and the subspecies may have almost exclusively used Plantago spp. in the 1970s and 1980s. Therefore, we are uncertain when the Bautista Road Core Occurrence Complex was initially colonized; however (as stated above in the ``Background'' section), we believe it currently provides colonists to higher elevations and, through this mechanism, likely facilitates range shift resulting from environmental changes that degrade suitable habitat conditions.
Inbreeding depression may slow colonization of new areas. However, when gene flow is restricted (for example, by mountainous terrain; Service 2003a, p. 13), local adaptation can occur quickly because peripheral populations are not swamped by genes adapted to environmental conditions specific to the range core (Zakharov and Hellman 2008, p. 199). Higher rates of local adaptation at a species' range edge may counteract any negative effects of inbreeding depression on colonization rate. Therefore, we did not base any of our conclusions on the hypothesis that inbreeding depression slows colonization of new areas in this subspecies.
Comment 6: One peer reviewer asserted the use of host plant species other than Plantago spp. and Antirrhinum coulterianum in Riverside County should be investigated before assuming they are not used. The peer reviewer stated that the western San Diego County populations may also use many undocumented host plants, including Castilleja affinis (coast Indian paintbrush), Castilleja foliolosa (woolly paintbrush), Collinsia heterophylla, and Antirrhinum nuttallianum (Nuttall's snapdragon).
Finally, the peer reviewer expressed the opinion that Penstemon centranthifolius (scarlet bugler) may also be an important Quino checkerspot host plant near the community of Anza. The peer reviewer stated that they observed Quino checkerspot butterflies in early spring near the community of Anza and that subspecies' presence appears to be positively correlated with relatively heavy feeding damage on P. centranthifolius by an asyetundetected herbivore. The peer reviewer hypothesized the feeding damage on P. centranthifolius could be caused by lateinstar Quino checkerspot butterfly larvae because they had difficulty detecting Quino checkerspot butterfly larvae on host plants other than Plantago spp. The peer reviewer concluded that P. centranthifolius might be important for postdiapause larval feeding because it is the only potential host plant species available for adult egg deposition and postdiapause larval feeding during periods of drought. Therefore, the peer reviewer believes P. centranthifolius may be an important food source for the Quino checkerspot butterfly larvae in highelevation sites during drought.
Our Response: We agree the Quino checkerspot butterfly may use different host plant species across its range. We provided a list of all host plant species where egg deposition has been documented in our ``Primary Constituent Elements'' section below, including Collinsia concolor, documented in 2008 to be used in the field by the Quino checkerspot. We appreciate information on potential use of Penstemon centranthifolius as a host plant; however, Quino checkerspot butterfly use of this potential hostplant species has not been documented, and any related changes to this final revised critical habitat designation would not be appropriate.
Comment 7: One peer reviewer noted that, based on his experience, Eriodictyon spp. (yerba santa), Chaenactis glabriuscula (pinchusion flower), and Ericameria linearifolia (narrowleaf goldenbush) are important nectar sources for Quino checkerspot butterfly survival. The peer reviewer stated some of the nectar sources on page 3335 of the proposed revised critical habitat rule (73 FR 3328; January 17, 2008) are not important because they are rarely visited by females and, therefore, do not contribute to increased production of eggs or subspecies survival.
Our Response: We appreciate this information based on the peer reviewer's experience and have revised our list of nectar source examples in the PCEs to include the species named by the peer reviewer. The peer reviewer did not specify which nectar sources on the existing PCE list they did not believe were important. Our list of nectar sources is not exhaustive, and nectar source importance can be site specific. Therefore, we believe our current PCE nectar source list is appropriate (see ``Primary Constituent Elements'' section below).
Comment 8: One peer reviewer stated that overcollection did not play a role in
[[Page 28784]]
the loss of Quino checkerspot butterfly populations.
Our Response: The listing rule (62 FR 2313; January 16, 1997) identified overcollection as a threat to the Quino checkerspot butterfly. The Service has initiated a 5year review on this subspecies and is reevaluating the magnitude and extent of all threats. We appreciate this information; however, we do not believe it is relevant to our final revised critical habitat designation.
Comment 9: One peer reviewer stated that they believe all areas containing low shrubs should be included in the PCEs because diapause constitutes the majority of the Quino checkerspot butterfly's annual life cycle, and larvae diapause in low shrubs such as Eriogonum fasciculatum (California buckwheat).
Our Response: This critical habitat designation includes all habitatbased population distributions associated with core occurrence complexes (see ``Criteria Used To Identify Critical Habitat'' section below), and the PCEs include all vegetation with an open woody canopy, including shrublands (see ``Primary Constituent Elements'' section below). Therefore, habitat containing low shrubs essential to the conservation of the subspecies, such as Eriogonum fasciculatum, is included in this final revised critical habitat designation.
Comment 10: One peer reviewer maintained that the availability of prominent hilltops should be ``weighed carefully in any decision relating to the possible exclusion of critical habitat and associated conservation plans'' because the loss of such courtship areas could result in the loss of populations even if other PCEs are present in designated critical habitat.
Our Response: This peer reviewer is apparently concerned that exclusion of areas from critical habitat will result in the loss of the excluded habitat, especially habitat containing hilltops. Section 4(b)(2) of the Act authorizes the Secretary to designate critical habitat after taking into consideration the economic impacts, national security impacts, and any other relevant impacts of specifying any particular area as critical habitat. An area may be excluded from critical habitat if it is determined that the benefits of exclusion outweigh the benefits of designating a particular area as critical habitat, unless the failure to designate will result in the extinction of the species. We believe the exclusions made in this final revised rule are legally supported under section 4(b)(2) of the Act and scientifically justified. The peer reviewer specifically commented on exclusions where conservation plans are in place. Areas excluded under section 4(b)(2) based on completed habitat conservation plans (HCPs) or other Serviceapproved management plans receive longterm protection and conservation; therefore, areas excluded from critical habitat designation should not result in the loss of the excluded habitat,. As discussed below, we fully considered and weighed the benefits to the conservation of the subspecies from including the specific areas we determined contain the physical and biological features essential to the conservation of the Quino checkerspot butterfly (including prominent hilltops used for mating) within the habitat conservation plan areas, in light of our determination that these areas will be adequately protected on lands covered by the Western Riverside County MSHCP and the San Diego County Multiple Species Conservation Program (MSCP), City of Chula Vista Subarea Plan (see ``Application of Section 4(b)(2) Other Relevant Impacts Conservation Partnerships'' section below).
Comment 11: One peer reviewer stated, ``Although annual surveys for the presence of [Quino checkerspot] butterfly adults are important * * * a population can be represented for several consecutive bad years by diapausing larval clusters that have been shown to survive for at least 4 years.'' The peer reviewer added that other butterfly and moth species have adapted to drought conditions in the western United States and are capable of diapausing for up to 30 years.
Our Response: We are aware Quino checkerspot butterflies can diapause for multiple years (Service 2003a, pp. 89), and under extreme drought conditions, no larvae in a surveyed area may have metamorphosed into adults. We are also aware that captive rearing and observations of the Quino checkerspot butterfly larvae indicate that repeated diapause is relatively common (over 50 percent likelihood for the first year; Pratt 2006, p. 10). Larvae can reenter diapause up to three times (four diapause periods), but more than three diapause periods during an individual's lifespan is unusual (Pratt 2007a, pp. 1013). Captive rearing and field data indicate that larvae typically undergo extended diapause when environmental conditions are not favorable for growth (Pratt 2007a, pp. 1013). Negative surveys are not considered credible if unfavorable weather, such as drought, limits Quino checkerspot butterfly detectability (Service 2002, p. 6). Therefore, we have confidence in the quality of surveys conducted by individuals with recovery permits under section 10 (a)(1)(A) of the Act and the relative rarity of spurious results. We did not base any of our criteria on negative surveys, and included contiguous habitat within 1.2 mi (2 km) of all documented observations within a core occurrence complex (see ``Criteria Used To Identify Critical Habitat'' section below), therefore we believe the apparent concerns of this peer reviewer have been adequately addressed in this rule.
Comment 12: One peer reviewer suggested the analysis of Quino checkerspot butterfly nectar resources in the proposed revisions to critical habitat was not sufficient. The peer reviewer maintained that nectar plant availability can vary to a large degree among occupied areas, and the relative importance of nectar plant species will change over the flight period of the butterfly and from yeartoyear. The peer reviewer emphasized that it is important to consider the contribution of nectar to increased female longevity and egg production.
Our Response: We agree that a more detailed nectarresourceneeds analysis would be desirable. However, we are not aware of any quantitative nectaruse data specific to the Quino checkerspot butterfly that would further inform our analysis. Consequently, we determined that the peerreviewed scientific publications that characterize Quino checkerspot butterfly nectar resources are the best scientific and commercial information available. Furthermore, variability in nectar source availability is not relevant to this final revised critical habitat designation because the PCE description relevant to nectar resources is not dependent on temporal variability (for example, many herbaceous plants are not detectable or identifiable durin
FOR FURTHER INFORMATION CONTACT
Field Supervisor, U.S. Fish and Wildlife Service, Carlsbad Fish and Wildlife Office (see ADDRESSES section). If you use a telecommunications device for the deaf (TDD), call the Federal Information Relay Service (FIRS) at 8008778339.