You may submit your comments and materials concerning this proposed rule by one of the methods listed in the ADDRESSES section. We will not accept comments you send by email or fax. Please note that we may not consider comments we receive after the date specified in the DATES section in our final determination.

Before including your address, phone number, email address, or other personal identifying information in your comment, you should be aware that we will post your entire commentincluding your personal identifying informationon http://www.regulations.gov. While you can ask us in your comment to withhold your personal identifying information from
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public review, we cannot guarantee that we will be able to do so.

Comments and materials we receive, as well as supporting documentation we used in preparing this proposed rule, will be available for public inspection on http://www.regulations.gov, or by appointment, during normal business hours, at the U.S. Fish and Wildlife Service Carlsbad Fish and Wildlife Office, 6010 Hidden Valley Road, Carlsbad, CA 92011; telephone 7604319440.

Background

We intend to discuss only those topics directly relevant to the designation of critical habitat in this proposed rule. For more information on the Quino checkerspot butterfly, refer to the final listing rule published in the Federal Register on January 16, 1997 (62 FR 2313), the final rule designating critical habitat published in the Federal Register on April 15, 2002 (67 FR 18356), and the Recovery Plan for the Quino Checkerspot Butterfly (Euphydryas editha quino) (recovery plan; Service 2003a). The recovery plan was coauthored by a Technical Recovery Team of seven expert biologists and ecologists (Service 2003a, p. ii), and provides a comprehensive scientific review and analysis of published and nonpublished information through 2002 relevant to conservation of the Quino checkerspot butterfly. While an extensive amount of peerreviewed, published scientific information is available on the species Euphydryas editha (Edith's checkerspot butterfly), such information specific to the Quino checkerspot butterfly subspecies is relatively sparse. Therefore, much of the information used in the final listing rule (62 FR 2313, January 16, 1997), the previous final rule designating critical habitat (67 FR 18356, April 15, 2002), and the recovery plan (Service 2003a) has been based on research on other subspecies of Edith's checkerspot. A number of biological and ecological similarities exist among subspecies of Edith's checkerspot (Service 2003a, p. 7), including similar life histories, shared or related host plant species, and similar movement behavior. We believe that extrapolation of data collected on other Edith's checkerspot butterfly subspecies, particularly the federally endangered bay checkerspot butterfly (Euphydryas editha bayensis), to the Quino checkerspot butterfly is justified in most cases (67 FR 18356, April 15, 2002).

Taxonomy and Biology

The Quino checkerspot butterfly is a member of the family Nymphalidae (brushfooted butterflies) and the subfamily Melitaeinae (checkerspots and fritillaries). The life cycle of the Quino checkerspot butterfly includes four distinct life stages: Egg, larva (caterpillar), pupa (chrysalis), and adult, with the larval stage divided into 5 to 7 instars (periods between molts, or shedding skin) (Service 2003a, p. 157). Typically there is one generation of adults per year, although larvae may remain in diapause (summer dormancy) for multiple years prior to maturation (Service 2003a, p. 8).

Distribution

The Quino checkerspot butterfly was historically distributed throughout the coastal portion of southern California (Los Angeles, Orange, western Riverside, San Diego, and southwestern San Bernardino Counties; Service 2003a, p. 32), and northern Baja California, Mexico (Mattoni, et al. 1997, p. 105). The historical distribution of the Quino checkerspot butterfly included the westernmost slopes of the Santa Monica Mountains, Los Angeles Plain and Transverse Ranges to the edge of the upper AnzaBorrego Desert, and south to El Rosario in Baja California, Mexico (Mattoni, et al. 1997, pp. 104105). Extant U.S. populations are apparently restricted to southwest Riverside and southern San Diego Counties (Service 2003a, p. 3; see further discussion below under Status and Local Distribution of Populations). Behavior and Population Structure

Scientific information indicates that Quino checkerspot butterfly populations display metapopulation dynamics characterized by highly variable habitat occupancy patterns, 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 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, their probabilities of existing at a given time are 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). Ehrlich and Murphy (1987, p. 127) noted that the minimum viable population approach favored by many conservation biologists may not be appropriate for the Edith's checkerspot butterfly; instead, focus should be shifted toward ``minimum viable metapopulations.'' Minimum viable metapopulation size is the minimum number of interacting local populations (and available habitat patches) required to balance subpopulation extirpations and recolonizations, and therefore required for longterm persistence (Hanski, et al. 1996, p. 527). No minimum viable metapopulation sizes have been assessed for the Quino checkerspot butterfly. Metapopulation viability analyses have been conducted for other species of nymphalid butterflies (Schtickzelle and Baguette 2004, p. 277; Schtickzelle, et al. 2005, p. 89) and one species within the genus Euphydryas (Wahlberg, et al. 2002, p. 224); however, these analyses are not applicable to Quino checkerspot butterfly as these studies all examined species that occur in other types of habitats (e.g., forest clear cuts, bogs, and marshes).

Harrison (1989, p. 1241) found that, although dispersal direction from habitat patches seemed to be random in the bay checkerspot butterfly, dispersing butterflies were likely to move into habitat patches when they passed within approximately 163 feet (ft) (50 meters (m)) of those habitat patches. Dispersing butterflies were most likely to remain in habitat patches where existing bay checkerspot 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 consistently occupied ``source'' habitat. High habitat colonization rates probably only occur during rare outbreak years, when 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 subspecies' survival (Murphy and White 1984, p. 353; Ehrlich and Murphy 1987, p. 127).

Delineating Population Footprints (Distribution)

Our ability to delineate individual population footprints (distribution) for
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the Quino checkerspot butterfly is limited to correlating presence absence survey observations with mapped habitat components. Quino checkerspot butterfly habitat patches are defined in any given year by adult movement within annually shifting host plant and nectar source distributions. Geographic population footprints have not been quantified for the Quino checkerspot butterfly. Therefore, the recovery plan discusses Quino checkerspot butterfly population locations in terms of ``occurrence complexes'' (Service 2007, p. 35), which are our best estimators based on recorded movement distances (see below discussion). Occurrence complexes are mapped in the recovery plan using a 0.6 mile (mi) (1 kilometer (km)) movement radius from each butterfly observation, and may be based on the observation of a single individual. Occurrences within approximately 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 the observed butterflies were likely to have come from the same population (Service 2003a, p. 35). All postlisting butterfly observations are classified as occurrence complexes, and the only one considered extirpated is Harford Springs. Occurrence complexes may expand due to new observation locations, or contract due to habitat loss (e.g. occurrence complexes defined in part by development, see Service 2003a, p. 78). Information regarding habitat within and contiguous with an occurrence complex must be used to estimate population distributions associated with occurrence complexes (Service 2003a, p. 35).

Longdistance movement in bay checkerspot butterflies has been documented as far as 4 mi (6.4 km; 1 male) (Murphy and Ehrlich 1980, p. 319), 3.5 mi (5.6 km; 1 male), and 2 mi (3 km; 1 female) (Harrison 1989, p. 1239). White and Levin (1981) conducted the only mark recapture movement study including Quino checkerspot butterflies. White and Levin (1981) studied withinhabitat patch movement of the Quino and bay checkerspot butterfly subspecies. They concluded that patterns of dispersal changed ``dramatically'' from year to year (White and Levin 1981, p. 348), and Quino checkerspot butterflies were less sedentary than the more heavily studied bay checkerspot butterflies (White and Levin 1981, p. 105). The high rate of dispersal observed by White and Levin (1981, p. 348), when it occurs during outbreak events, would result in expansion of existing population distributions, and recolonization of habitat patches where subpopulations have been extirpated within a metapopulation distribution, as hypothesized by Murphy and White (1984, p. 353).

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), recorded movement distances were limited by 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 outdispersal 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'' (1981, p. 353). According to recorded Edith's checkerspot butterfly movement distances (Gilbert and Singer 1973, pp. 65, 66; Harrison, et al. 1988, pp. 367380; 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 (Service 2003a, p. 35). The size of occurrence complexes is defined as the total area encompassed by all 1.2 mi (2 km) movement radii from individual butterfly observation locations. New occurrence information since 2002 supports expanding some occurrence complexes and/or merging some separate occurrence complexes that were previously described in the Quino checkerspot butterfly recovery plan.

Some occurrence complexes were identified in the recovery plan (Service 2003a, p. 35) as ``core.'' Core occurrence complexes are those that, based on geographic size, number of reported individuals, and repeated observations, appear to be centers of population density. Such population density centers are likely to contain ``source'' habitat (supporting ``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), 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). A source population is one in which the emigration rate typically exceeds the immigration rate (therefore a source of colonists for unoccupied habitat patches within a population footprint), although they are not necessarily more stable than nonsource populations (Service 2003a, p. 166).
Status and Local Distribution of Populations in Riverside County

The recovery plan identified 7 core and 18 noncore occurrence complexes in western Riverside County: Harford Springs (noncore); Canyon Lake (noncore); Warm Springs Creek (core); Warm Springs Creek North (noncore); Skinner/Johnson (core); Domenigoni Valley (noncore); Sage (core); Black Hills (noncore); San Ignaciao (noncore); Rocky Ridge (noncore); Wilson Valley (core); Vail Lake (core); Butterflied/ Radec (noncore); Aguanga (noncore); Dameron Valley (noncore); Billy Goat Mountain (noncore); Brown Canyon (noncore); Southwest Cahuilla (noncore); Tule Peak (core); Silverado (core); Spring Canyon (non core); Cahuilla Creek (noncore); Bautista Road (noncore); Pine Meadow (noncore); and Lookout Mountain (noncore) (Service 2003a, pp. 39, 41, 44). Occurrence data collected in Riverside County since the recovery plan was published in 2003 has resulted in expansion of all core occurrence complexes, and merging of some core occurrence complexes with noncore occurrence complexes (see discussion below). Quino checkerspot butterflies have not been observed in the Harford Springs (noncore) Occurrence Complex or other proximal historic locations since 1986, and therefore are no longer considered extant in that area.

Development has reduced the quality, connectivity, and amount of associated habitat in the Warm Springs Creek Core Occurrence Complex since the recovery plan was published in 2003 (Allen and Preston 2006, p. 7). Although habitat associated with this core occurrence complex may support a declining population, the Quino checkerspot butterfly captive rearing facility is also located within this area, and it is likely to be a site of focused population management and augmentation in the future. Despite concern for the viability of this population, several experts have expressed the opinion that this core occurrence complex represents an important Quino checkerspot butterfly population that has potential to persist indefinitely if the remaining habitat is conserved and managed (Ballmer, et al. 2003, p. 2; Ballmer and Osborne 2005, pp. 12; Allen and Preston 2006, pp. 1012). Because the Warm Springs Creek Core Occurrence Complex has been isolated from other core occurrence complexes (Service 2003a, p. 41) and recent development has reduced and fragmented habitat in this area (Allen and Preston 2006, p. 7),
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remaining contiguous habitat, including habitat more than one km distant from observation locations (outside of the mapped occurrence complexes), is likely the minimum area needed to support a viable managed population. Therefore, we have determined that the Warm Springs Creek North (noncore) Occurrence Complex (Service 2003a, p. 39) and habitat contiguous with the Warm Springs Creek Core Occurrence Complex habitat should be considered a single population footprint and merged with the Warm Springs Creek Core Occurrence Complex identified in the recovery plan (Service 2003a) into a single, expanded Warm Springs Creek Core Occurrence Complex. The expanded Warm Springs Creek Core Occurrence Complex is a constrained population distribution defined by remaining undeveloped, connected habitat associated with Quino checkerspot butterfly observations in this area.

Occurrence data collected in Riverside County since listing (62 FR 2313, January 16, 1997) has continued almost annually to expand the known northeastern limits of the subspecies' range (Pratt, et al. 2001, pp. 169171; Service 2003a, p. 44; Poopatanapong 2008, pp. 2, 4). The recovery plan identified four noncore occurrence complexes east of Temecula in the foothills and valleys south of Mount San Jacinto: Brown Canyon (Service 2003a, p. 41), Bautista Road, Pine Meadow, and Lookout Mountain (Service 2003a, p. 44). The Bautista Road (described as non core in the recovery plan) Occurrence Complex is in a valley east of Temecula and north of the town of Anza. Multiple new observations have occurred within and around the Bautista Road Occurrence Complex (AMEC 2004, p. 6; Mooney Jones & Stokes 2005, p. 10). Consistent with criteria outlined in the recovery plan (Service 2003a, p. 35), we now consider the Bautista Road Occurrence Complex to be a core occurrence complex. As described below, from 2004 to 2006, multiple new observation locations were also reported in the town of Anza, and north and northwest of the Bautista Road (core), Pine Grove (noncore), and Lookout Mountain (noncore) occurrence complexes, resulting in new non core occurrence complexes and expansion of the subspecies' known range (Service Geographic Information Systems (GIS) database). The new non core occurrence complexes are: the Cave Rocks Occurrence Complex within the town of Anza, just north of the intersection of Bautista Road and State Route (SR) 371 (AMEC 2004, p. 9); the Quinn Flat Occurrence Complex located between Forbes Ranch Road and Morris Ranch Road northeast of Quinn Flat and SR 74 (Pratt 2005, p. 1; Toth 2005, p. 1; San Bernardino National Forest (SBNF) GIS database); the Horse Creek Occurrence Complex adjacent to Bautista Road, southeast of Bautista Spring (AMEC 2004, p. 6; Malisch 2006, p. 1); and the North Rouse Ridge Occurrence Complex located on Rouse Ridge in the hills east of Bautista Canyon, near where Bautista Road exits the foothills (Toth 2005, p. 1; Poopatanapong 2007, pp. 2, 4; SBNF GIS database).

Recent monitoring information indicates that the Tule Peak and Silverado core occurrence complexes described in the recovery plan (Service 2003a, p. 44) are part of a single highdensity population footprint supporting periodic outbreak events, similar to historic events (Service 2003a, p. 29) such as the 1977 outbreak reported by Murphy and White (1984, p. 351; Ehrlich and Murphy 1987, p. 127) in San Diego County (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). The hundreds of adults observed during surveys in the Tule Peak Core Occurrence Complex in 2001 were unprecedented, 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 2007a, p. 1; CFWO 2004; Pratt 2004, pp. 16, 17). Moreover, over 30 new occurrence locations with high adult densities were reported in 2004 in the vicinity of Tule Peak Road (92 to over 100 observations in a single day) south of the Cahuilla Band of Indians Tribal lands and the town of Anza (Osborne 2004, pp. 16, 810; Anderson 2007a, p. 5; CFWO 2004; Osborne 2007, pp. 1316). These new observations prompted us 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.

Available scientific information (including recent outbreaks in the closest core occurrence complexes) suggests the new Bautista Core Occurrence Complex and other noncore occurrence complexes north of the town of Anza are the result of recent colonization events and an ongoing range shift for this subspecies northward and upward in elevation. Parmesan (1996, pp. 765766) concluded that the average position of known Edith's checkerspot butterfly populations (including the Quino checkerspot butterfly) has shifted northward and upward in elevation, apparently due to a warming, drying climate, and the recovery plan confirms this (Service 2003a, p. 64). Parmesan (1996, pp. 765766) compared the distribution of 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 rangewide patterns of local extirpations of Edith's checkerspot butterflies, and noted that populations in the southern part of the range (primarily the Quino checkerspot butterfly) experienced 80 percent of all recorded local extirpations (Parmesan 1996, pp. 765 766). Parmesan (1996, pp. 765766) concluded that this pattern of extirpations indicated contraction of the southern boundary of the subspecies' overall distribution by almost 100 mi (160 km), and a shift in the average location of a Edith's checkerspot butterfly occurrence northward by 57 mi (92 km). This shift in range closely matched shifts in mean yearly temperature (Parmesan 1996, pp. 765766). Studies have demonstrated a correlation of population distribution and phenology changes with climate changes 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; Thomas, et al. 2006, pp. 146147, 251; 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 also 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). Such similar climate response patterns in related and cooccurring insect species further support the validity of Parmesan's (1996, pp. 765766) Quino
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checkerspot butterfly observations and conclusions.

Documentation of climaterelated 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; Brashears, et al. 2005, p. 15144), and future drought predictions for California (e.g., Field, et al. 1999, pp. 810; Brunell and Anderson 2003, p. 21; Lenihen, et al. 2003, p. 1667; Hayhoe, et al. 2004, p. 12422; Brashears, et al. 2005, p. 15144; Seager, et al. 2007, p. 1181) and North America (IPCC 2007, p. 9) indicate prolonged drought and other climaterelated changes will continue into the foreseeable future, and we anticipate these changes will affect Quino checkerspot butterfly habitat and populations. Thomas, et al. (2004, p. 147) estimated 29 percent of species in scrublands (habitat for 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). The mostrecent subspecies specific evidence corresponds with the hypothesis that drought conditions at the northern edge of the subspecies' range is resulting in ongoing range shift at the northern edge of the range to more northern and higher elevation areas that experience higher precipitation: Surveyors noted that during drought conditions in 2007, 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).

The Anza/Mount San Jacinto foothills area (Bautista care occurrence complex) is the northern extent of the range of the Quino checkerspot butterfly and supports the greatest elevational gradient within the extant range of the butterfly. Indications that maintenance of the Tule Peak/Silverado and Bautista Road core occurrence complexes, and maintenance of habitat connectivity to higher elevation noncore occurrence complexes, is needed to prevent a significant increase in the subspecies' extinction probability (Service 2003a, pp. 46, 47; Osborne 2007, pp. 910) include the following: Parmesan's subspecies specific study (Parmesan 1996); recent documented Quino checkerspot butterfly outbreak events (discussed above); the complete lack of Quino checkerspot butterfly observations in Riverside County during 2007 monitoring; documented drought conditions and the likelihood that recurrent drought conditions will persist into the foreseeable future; and the likelihood that the new noncore occurrence complexes in the most northern, highest elevation habitat areas (Pine Grove, Lookout Mountain, Quinn Flat, Horse Creek, Cave Rocks, and the North Rouse Ridge) are a result of colonization from lower elevation populations over the past 1015 years (such as the Bautista Road and Tule Peak/ Silverado core occurrence complexes). Parmesan's (1996, pp. 765766) rangeshift statistics predict the following Quino checkerspot butterfly population changes: (1) Declines in, and losses of, the southernmost and/or lowest elevation populations, especially in drier areas where rainfall is most variable (such as southwest Riverside County; Anderson 2000, pp. 3, 6); (2) increases in the density and resilience of the most northern and/or highest elevation populations, especially in wetter areas (such as the Anza area; Service 2003a, p. 44); and (3) establishment of new populations, or expansion of existing populations, northward and upward in elevation where range shift is the least impeded by habitat loss due to landuse changes (such as the Mount San Jacinto foothills; Service GIS database and satellite imagery). Anza area core occurrence complexes (Tule Peak/Silverado and Bautista Road) also support the highest (cooccurring) diversity of host plant species (Plantago patagonica, Antirrhinum coulterianum, Cordylanthus rigidus, and Castilleja exserta) within the range of the Quino checkerspot butterfly, a factor known to mitigate the effects of climate extremes on Edith's checkerspot butterfly populations (Hellman 2002, p. 925). In light of the recent warming and drying trends (see above discussion), prudent design of reserves and other managed habitats in the Anza area, where the subspecies range is expanding northward and upward in elevation should include landscape connectivity to other habitat patches and ecological connectivity (habitat patches linked by dispersal areas; Service 2003a, p. 162) in order to accommodate range shifts northward and upward in elevation (Service 2003a, p. 64). Although habitat quality may be changing throughout the subspecies range, suitable habitat north and upward in elevation of the southernmost populations is already occupied, and colonization events associated with climate change are likely only occurring in the Anza area.
Status and Local Distribution of Populations in San Diego County

The recovery plan identifies 4 core and 10 noncore occurrence complexes in southwest San Diego County surrounding Otay Mountain and Otay Lakes: West Otay Mesa (noncore), Otay Valley (core); West Otay Mountain (core); Otay Lakes/Rancho Jamul (core); Proctor Valley (non core); Jamul (noncore); Hidden Valley (noncore); Rancho San Diego (noncore); Los Monta[ntilde]as (noncore); Honey Springs (noncore); Dulzura (noncore); Marron Valley (core); Barrett Junction (noncore), and Tecate (noncore) occurrence complexes (Service 2003a, pp. 39, 41, 44). 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 is further supported by the recovery plan, which noted that occupied habitat in the vicinity of Otay Lakes and Rancho Jamul is an area of key landscape connectivity for all subpopulations in southwest San Diego County (Service 2003a, pp. 53, 54).

Following publication of the recovery plan in 2003, the Otay Fire severely burned habitats where the majority of Quino checkerspot butterflies had been observed within southwest San Diego County (IBAERT 2003, pp. 8990), including most of the Otay Mountain Core Occurrence Complex. In 2005, the smaller Border 50 Fire burned most habitat within the Marron Valley Core Occurrence Complex west of Otay Mountain that was not burned in the 2003 Otay Fire (Service GIS database). Although postfire monitoring surveys indicated no populations were completely extirpated by the 2003 and 2005 fires (CFWO 2004, 2005, 2006; Anderson 2007b, p. 2), Quino checkerspot butterfly densities and the extent of occupied habitat appeared to be reduced, and surveyors reported an apparent increased rate of exotic plant species invasion (Anderson 2007b, pp. 23). An indirect threat exacerbated by fire damage is increased invasion of habitat by nonnative plant species, resulting in reduction of Quino checkerspot butterfly host plants through competition (Service 2003a, pp. 5758, 6061). Catastrophic fire has been implicated in the final extirpation of the Quino checkerspot butterfly from Orange County (Service 2003a, pp. 30, 6061), therefore widespread catastrophic fire impacts to Quino checkerspot butterfly habitat within this core occurrence complex, are likely to
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affect the survival probability of the subspecies in southwest San Diego County (Service 2003a, pp. 6061).

The effects of fire on Quino checkerspot butterfly populations in southwest San Diego County were evident in 2007. The northernmost occupied areas within the Otay Mountain Core Occurrence Complex (Honey Springs and Dulzura noncore occurrence complexes as identified in the recovery plan) had the highest densities of adult butterflies and supported the most reproduction (observed larvae) of any known occupied areas in 2007 (CFWO 2007). These areas were not affected by the 2003 Otay and 2005 Border 50 fires. Therefore, observed relatively high Quino checkerspot butterfly abundance in 2007 in the Honey Springs and Dulzura areas (CFWO 2002, 2003, 2004, 2005, 2006, 2007) was primarily due to the lack of recent fire impacts (Anderson 2007b, p. 3). In 2007, the Harris Fire perimeter encompassed approximately 72% of the new Otay Mountain Core Occurrence Complex, including the northern areas that were not affected by fire in 2003 or 2005 (Service GIS database). Habitat damage within the 2007 fire perimeter is still being assessed.

Several widely distributed new observation locations have been reported in central San Diego County since 2002 (Dudek 2005, p. 1; Faulkner 2005, p. 1; Tierra Environmental Services 2005, p. 4), resulting in three new San Diego County noncore occurrence complexes (Fanita Ranch, Sycamore Canyon, and Mission Trails Park). Although these Quino checkerspot butterfly populations may contribute to the subspecies' recovery (Service 2003a, pp. 8688), we cannot determine whether these new noncore occurrence complexes represent: (1) Residual, lowdensity populations decreasing in abundance; (2) resilient, lowdensity populations increasing in abundance; or (3) recent colonization events. Given the proximity of these occurrence complexes to historical collection locations (Service 2003a, p. 3), observed and predicted climate trends and associated population dynamic/range changes (see above discussion), and the relative isolation of these occurrence complexes from areas known to be occupied at the time of listing, it is likely they represent residual, low density populations decreasing in 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 2005, pp. 12; 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 core occurrence complex, 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). Although not quite proximal enough to be considered a single occurrence complex based on overlapping movement distances (Service 2003a, p. 35), we consider this cluster of new observations near Campo to belong to a new, independent La Posta/Campo Core Occurrence Complex that we believe represents a population density center likely to contain source habitat (i.e., core occurrence complex) based on: (1) Recent documentation of these occupied habitats; (2) the small number of surveys conducted in this area in the past (Service survey report files) resulting in a low likelihood of detection; (3) contiguous habitat linked by short dispersal areas (e.g., a stream butterflies can fly over) between observation locations (Service GIS vegetation database and satellite imagery); and (4) the presence of Antirrhinum coulterianum (white snapdragon) host plants in occupied habitat (O'Connor 2006, pp. 24). White snapdragon had not been previously recorded in occupied Quino checkerspot butterfly habitat in San Diego County (Service survey report files). White snapdragon densities recorded in the vicinity of Campo (O'Connor 2006, pp. 24) were relatively high, and similar to those observed in the Tule Peak/ Silverado Core Occurrence Complex in Riverside County, the only core occurrence complex where recent Quino checkerspot butterfly ``outbreak events'' have been recorded (see above discussion).

Quino checkerspot butterflies have recently been observed in two new locations in southeast San Diego County near Jacumba (identified as the Jacumba East and Jacumba West occurrence complexes) (Essex and Osborne 2005, p. 82; Klein 2007, p. 1). Additionally, data collected from the Jacumba Occurrence Complex since publication of the recovery plan has 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 and small number of observed individuals. 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). As many as 50 individuals are estimated to have been observed in one day near Jacumba Peak (Pratt 2007c, p. 1). Furthermore, reproduction was documented in the Jacumba Occurrence Complex in 1998 and again in 2004 (Pratt 2007a, p. 1). Therefore, we now consider Jacumba to be a core occurrence complex representing what appears to be a small, but resilient, population.

The prediction that drought conditions are likely to continue into the foreseeable 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 complexes are warmer and drier than the Otay Mountain Core Occurrence Complex, and differ substantially in other habitat characteristics (Service 2003a, pp. 3654; O'Conner 2006, p. 4). Therefore, maintenance of these core occurrence complexes likely is important for recovery and survival of the Quino checkerspot butterfly in San Diego County. These new core occurrence complexes were also the only core occurrence complexes in San Diego County (the subspecies' southern range) not affected by the fires in 2003 and 2005 (see above discussion). Therefore, new information indicates the La Posta/Campo and Jacumba core occurrence complexes contribute significantly to reducing the subspecies' extinction probability.

Previous Federal Actions

For more information on previous Federal actions concerning the Quino checkerspot butterfly, refer to the final critical habitat rule published in the Federal Register on April 15, 2002 (67 FR 18356) and the final listing rule published in the Federal Register on January 16, 1997 (62 FR 2313). In March 2005, the Homebuilders Association of Northern California, et al., filed suit against the Service challenging the merits of the final critical habitat designations for several species, including the Quino checkerspot butterfly. In March 2006, a settlement was reached that required the Service to reevaluate five final critical habitat designations, including critical habitat designated for the Quino checkerspot butterfly. The settlement stipulated that any proposed revisions to the Quino checkerspot butterfly designation would be submitted for publication to the [[Page 3334]]
Federal Register on or before December 7, 2007. A courtapproved amendment to the settlement agreement extended this deadline for submission to the Federal Register to January 8, 2008.

Critical Habitat

Critical habitat is defined in section 3 of the Act as: (1) The specific areas within the geographical area occupied by a species, at the time it is listed in accordance with the Act, on which are found those physical or biological features
(a) Essential to the conservation of the species and
(b) Which may require special management considerations or protection; and
(2) Specific areas outside the geographical area occupied by a species at the time it is listed, upon a determination that such areas are essential for the conservation of the species.

Conservation, as defined under section 3 of the Act, means the use of all methods and procedures that are necessary to bring any endangered species or threatened species to the point at which the measures provided under the Act are no longer necessary.

Critical habitat receives protection under section 7 of the Act through the prohibition against Federal agencies carrying out, funding, or authorizing the destruction or adverse modification of critical habitat. Section 7(a)(2) of the Act requires consultation on Federal actions that may affect critical habitat. The designation of critical habitat does not affect land ownership or establish a refuge, wilderness, reserve, preserve, or other conservation area. Such designation does not allow government or public access to private lands. Such designation does not require implementation of restoration, recovery, or enhancement measures by private landowners. Where a landowner requests federal agency funding or authorization for an action that may affect a listed species or critical habitat, the consultation requirements of section 7(a)(2) may apply, but even in the event of a destruction or adverse modification finding, the Federal action agency's and the applicant's obligation is not to restore or recover the species, but to implement reasonable and prudent alternatives to avoid destruction or adverse modification of critical habitat.

To be included in a critical habitat designation, habitat within the geographical area occupied by the species at the time it was listed must contain physical and biological features that are essential to the conservation of the species. Consistent with this requirement, the Service identifies, to the extent known using the best scientific data available, habitat areas on which are found primary constituent elements (PCEs), as defined at 50 CFR 424.12(b), and identifies the quantity and spatial arrangement of such areas to ensure that the areas designated as critical habitat are essential for the conservation of the species. To be included in the designation, the features at issue must also be ones that may require special management considerations or protection.

Under the Act, we can designate areas outside the geographical area occupied by the species at the time it is listed as critical habitat only when we determine that those areas are essential for the conservation of the species.

Section 4 of the Act requires that we designate critical habitat on the basis of the best scientific and commercial data available. Further, our Policy on Information Standards Under the Endangered Species Act (published in the Federal Register on July 1, 1994 (59 FR 34271)), the Information Quality Act (section 515 of the Treasury and General Government Appropriations Act for Fiscal Year 2001 (Pub. L. 106554; H.R. 5658)), and our associated Information Quality Guidelines provide criteria, establish procedures, and provide guidance to ensure that our decisions are based on the best scientific data available. They require our biologists, to the extent consistent with the Act and with the use of the best scientific data available, to use primary and original sources of information as the basis for recommendations to designate critical habitat.

When we are determining which areas should be proposed as critical habitat, our primary source of information is generally the information developed during the listing process for the species. Additional information sources may include the recovery plan for the species, articles in peerreviewed journals, conservation plans developed by States and Counties, scientific status surveys and studies, biological assessments, other unpublished materials, and expert opinion or personal knowledge.

Habitat is often dynamic, and species may move from one area to another over time. Furthermore, we recognize that critical habitat designated at a particular point in time may not include all of the habitat areas that we may later determine, based on scientific data not now available to the Service, are essential for the conservation of the species. For these reasons, a critical habitat designation does not signal that habitat outside the designated area is unimportant or may not be required for recovery of the species.

Areas that are important to the conservation of the species, but are outside the critical habitat designation, will continue to be subject to conservation actions implemented by the Service and other Federal agencies under section 7(a)(1) of the Act. Areas that support populations are also subject to the regulatory protections afforded by the section 7(a)(2) jeopardy standard, as determined on the basis of the best available scientific information at the time of the agency action. Federally funded or permitted projects affecting listed species outside their designated critical habitat areas may still result in jeopardy findings in some cases. Similarly, critical habitat designations made on the basis of the best available information at the time of designation will not control the direction and substance of future recovery plans, habitat conservation plans (HCPs), or other species conservation planning efforts if new information available at the time of these planning efforts calls for a different outcome. Methods

As required by section 4(b) of the Act, we used the best scientific data available to determine areas within the geographical area occupied at the time of listing that contain physical or biological features essential to the conservation of the Quino checkerspot butterfly, and areas outside of the geographical area occupied at the time of listing that are essential for the conservation of the butterfly. We have also reviewed available information that pertains to the habitat requirements of this subspecies. These sources included, but were not limited to, the final rule to list this subspecies (62 FR 2313; January 16, 1997); data and information published in peerreviewed articles; data and information contained in the recovery plan (Service 2003); survey and research reports submitted to the Service, including reports required by 10(a)(1)(A) recovery permits; information provided by subspecies experts, including the subspecies' recovery team; data submitted during section 7 consultations; and regional GIS data. Primary Constituent Elements

In accordance with section 3(5)(A)(i) of the Act and regulations at 50 CFR 424.12, in determining which areas within the geographical area occupied at the time of listing to propose as critical habitat, we identify the physical or biological features essential to the conservation of the Quino checkerspot
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butterfly based on its biological needs. We consider the physical or biological features essential to the conservation of the species to be the primary constituent elements (PCEs) laid out in the appropriate quantity and spatial arrangement for conservation of the species. As described at 50 CFR 424.12, the physical and biological features that are essential to the conservation of a species, and that may require special management considerations or protection, include, but are not limited to:
(1) Space for individual and population growth and for normal behavior;
(2) Food, water, air, light, minerals, or other nutritional or physiological requirements;
(3) Cover or shelter;
(4) Sites for breeding, reproduction, rearing, or development of offspring; and
(5) Habitats that are protected from disturbance or are representative of the historical, geographical, and ecological distributions of a species.
Space for Individual and Population Growth and for Normal Behavior

Habitat for the Quino checkerspot butterfly is characterized by patchy shrub or small tree landscapes with openings of several meters between large plants, or a landscape of open swales alternating with dense patches of shrubs (Mattoni, et al. 1007, p. 112), habitats often collectively termed ``scrublands.'' Quino checkerspot butterflies will frequently perch on vegetation or other substrates to mate or bask, and require open areas to facilitate movement (Service 2003, pp. 1011). White and Levin (1981, pp. 350, 351) found that adult Quino checkerspot butterfly's withinhabitat patch movement distances from larval host plant patches to adult nectar sources often exceeded 656 ft (200 m). Food, Water, Air, Light, Minerals, or Other Nutritional or Physiological Requirements

Because of their exothermic (coldblooded) metabolism (Service 2003a, p. 18) and need to complete their life cycle in as short a time as possible (Service 2003a, p. 20), larval and adult Quino checkerspot butterflies require an open, woody canopy that allows sun to penetrate and speed their metabolic rate.

Within open, woodycanopy communities, larvae seek microclimates with high solar exposure (Weiss, et al. 1987, p. 161; Weiss, et al. 1988, p. 1487; Osborne and Redak 2000, p. 113). Like most butterflies, adult Quino checkerspot butterflies frequently bask and remain in open canopy areas, using air temperature and sunshine to increase their body temperature to the level required for normal active behavior (Service 2003a, p. 18).

Quino checkerspot butterfly oviposition (egg deposition) has most often been documented on dwarf plantain (Plantago erecta), woolly plantain (Plantago patagonica), and white snapdragon (Anterrhinum coulterianum) (Service 2003a, p. 1418). Egg clusters and/or pre diapause larval clusters (proof of adult oviposition) have also been documented in the field on threadleaved bird's beak (Cordylanthus rigidus) and purple owl'sclover (Castilleja exserta) (Service 2003a, pp. 1418). Cordylanthus rigidus and Castilleja exserta alone are not believed to be sufficient to support Quino checkerspot butterfly breeding; therefore, other species of host plant must coexist within approximately 328 ft (100 m) of these species of host plant for habitat to support breeding (Service 2003, pp. 1617).

During the first two instars, prediapause larvae cannot move more than a few centimeters and feed on the host plant on which the adult female butterfly deposited eggs (primary host plant species). Third instar larvae usually wander independently in search of food and may switch to feeding on a secondary host plant species (Service 2003, p. 7). All known species of host plant (see species listed above) may serve as primary or secondary host plants, depending on location and environmental conditions (Service 2003, p. 17). Although Plantago erecta densities required for larval development have been estimated (Service 2003, pp. 2223), it is not always possible any given year to determine typical host plant densities because germinating host plants may be entirely consumed by larvae, or when precipitation levels have been belowaverage, seeds may not germinate and larvae may remain in diapause (Service 2003, p. 23).

Adult checkerspot butterflies of the genus Euphydryas have a short tongue, approximately 0.43 inches (in) (11 millimeters (mm)) in length (Pratt 2007b, p. 1), and typically cannot feed on flowers that have deep corolla tubes or flowers evolved to be opened by bees (Service 2003a, p. 19). Edith's checkerspot butterflies prefer flowers with a platformlike surface on which they can remain upright while feeding (Service 2003a, p. 19). Examples of flowers Quino checkerspot butterflies frequently take nectar from include lomatium (Lomatium spp.), goldenstar (Muilla spp.), fiddleneck (Amsinckia spp.), goldfields (Lasthenia spp.), and popcorn flowers (Plagiobothrys and Cryptantha spp.) (Service 2003a, p. 19). Adults may nectar on flowers with a corolla length nearly a centimeter longer than their proboscis (0.591.10 in (1528 mm)), like Linanthus androsaceus (Murphy 1984, p. 114; Hickman 1993, p. 842), but they are not likely to prefer such species (Murphy 1984, p. 114).

Cover or Shelter

Quino checkerspot butterfly larvae require sheltered sites for diapause (Service 2003a, p. 8), and adults typically roost in or below shrubs overnight and during adverse weather conditions (Service 2003a, p. 10). A pilot laboratory study (Pratt 2006, p. 9) and larval distribution observations (Osborne and Redak 2000, p. 113) indicate Quino checkerspot butterfly larvae prefer to diapause in or near the base of native shrubs, such as California buckwheat (Eriogonum fasciculatum).
Sites for Breeding, Reproduction, or Rearing (or Development) of Offspring

Male Quino checkerspot butterflies, and to a lesser extent females, are frequently observed on hilltops and ridgelines (CFWO GIS Quino checkerspot butterfly database, Osborne 2001, pp. 12; Pratt 2001, p. 59). In Edith's checkerspot butterflies, this tendency of females to move upwards in elevation and of males to defend hilltops
(``hilltopping behavior'') increases the likelihood of male and female butterflies finding each other to mate during years of low adult density (Baughman and Murphy 1988, p. 119; Ehrlich and Wheye 1988, pp. 460461). On hilltops where males are likely to encounter virgin females, the males will defend their territory from other males; therefore, higher ground can serve as a ``visual beacon'' to enhance mating success (Baughman and Murphy 1988, p. 119; Ehrlich and Wheye 1988, pp. 460461; Mattoni, et al. 1997, p. 109). Hilltopping has been observed in Quino checkerspot butterflies (Mattoni et al. 1997, p. 110, Osborne 2001, pp. 12). Like other subspecies of Edith's checkerspot, adult Quino checkerspot butterflies are reliably observed on hilltops in occupied habitat (Service GIS database), even in the absence of larval host plants (Osborne 2001, pp. 12; Pratt 2001, p. 59); therefore, hilltops and ridgelines provide features essential for breeding in local populations.
Primary Constituent Elements for the Quino Checkerspot Butterfly

For areas within the geographical area occupied by the Quino checkerspot
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butterfly at the time of listing, we must identify the primary constituent elements (PCEs) that may require special management considerations or protection. Based on the above needs and our current knowledge of the life history, biology, and ecology of the subspecies, we have determined the Quino checkerspot butterfly's PCEs are: (1) Open areas within scrublands at least 21.5 square feet (ft) (2 square meters (m)) in size that:
(A) Contain no woody canopy cover; and
(B) Contain one or more of the host plants Plantago erecta, Plantago patagonica, or Antirrhinum coulterianum; or
(C) Contain one or more of the host plants Cordylanthus rigidus or Castilleja exserta that are within 328 ft (100 m) of the host plants Plantago erecta, Plantago patagonica, or Antirrhinum coulterianum; or (D) Contain flowering plants with a corolla tube less than or equal to 0.43 inches (11 millimeters) used for Quino checkerspot butterfly growth, reproduction, and feeding;
(2) Open scrubland areas and vegetation within 656 ft (200 m) of the open canopy areas (PCE 1) used for movement and basking; and (3) Hilltops or ridges within scrublands, linked by open areas and natural vegetation (PCE 2) to open canopy areas (PCE 1) containing an open, woodycanopy area at least 21.5 square ft (2 square m) in size used for Quino checkerspot butterfly mating (hilltopping behavior). Special Management Considerations or Protection

When designating critical habitat, we assess whether the areas within the geographical area occupied by the species at the time of listing contain features that are essential to the conservation of the species and may require special management considerations or protection.

When the Quino checkerspot butterfly was listed on January 16, 1997 (62 FR 2313), the primary threats to the subspecies thought to be responsible for its decline were reduction and fragmentation of habitat by urban and agricultural development and recreational activities, overcollection, vandalism, fire, and drought. Threats described in the listing rule, as well as trash dumping, nitrogen deposition, elevated atmospheric carbon dioxide concentrations, and climate change, were listed as active or probable threats in the final designation of critical habitat (67 FR 18356) published April 15, 2002. Current threats to the subspecies and management needs were described in detail in the recovery plan (Service 2003a, pp. 5565). They are: (1) Loss and fragmentation of habitat and landscape connectivity; (2) invasion by nonnative plants; (3) offroad vehicle activity; (4) grazing; (5) fire; (6) enhanced soil nitrogen; (7) increasing atmospheric carbon dioxide concentration; and (8) climate change. Scientific research indicates all threats individually, and interactively, cause loss or reduced availability of Quino checkerspot butterfly host plants, nectar sources, and suitable areas for necessary behaviors (e.g., mating, basking, hilltopping, etc.) (Service 2003a, pp. 5565). This results in a loss of PCEs. For example, increased atmospheric carbon dioxide concentration resulted in an approximate 30 percent loss in seed production of Plantago lanceolata (Jablonski, et al. 2002, p. 14), and increased temperatures caused an approximate 5 percent reduction in reproductive duration (Sherry, et al. 2007, p. 200), indicating reduced host plant density and phenological availability under current and predicted climate conditions (Service 2003a, pp. 6265; see Background section above). In addition, development activities can result in the loss of open, woodycanopy native scrublands and hilltops (space for normal behavior and larval diapausing sites) and fragmentation of habitat and landscape connectivity.

Management needs and actions recommended by the recovery plan that may be required to protect and maintain the PCEs for the Quino checkerspot butterfly include: (1) Reestablishment and maintenance of habitat and landscape connectivity within and between populations (Service 2003a, pp. 57, 96101); (2) habitat restoration and control of invasive nonnative species (Service 2003a, pp. 58, 96101, 146159); (3) monitoring of ongoing habitat loss and nonnative plant invasion (Service 2003a, p. 106); (4) phased replacement of grazing with nonnative invasive plant control (Service 2003a, pp. 60, 101102); (5) carefully controlled burn experiments to assess effectiveness for control of nonnative plant invasion and protection of PCEs from wildfire destruction (Service 2003a, p. 61); (6) reduction of local nitrogen emissions from sources such as hightraffic roads (Service 2003a, p. 62); (7) management of offroad vehicle activity (Service 2003a, pp. 59, 146159), including outreach and partnerships with local offroad vehicle clubs and organizations (Service 2003a, p. 105); (8) reduction of firearm use and trash dumping in habitat (Service 2003a, p. 109); and (9) prudent design of managed habitats to include landscape connectivity (habitat) and ecological connectivity (wildlands that may not currently include habitat) (Service 2003a, pp. 65, 96). Criteria Used to Identify Critical Habitat

There is a lack of specific knowledge regarding distribution of occupancy within the greater historical range of the Quino checkerspot butterfly, and Edith's checkerspot butterfly subspecies' occupancy within population distributions is generally shifting and ephemeral (see Background Section above). Therefore, the appropriate scale for determining Quino checkerspot butterfly occupancy at the time of listing is the population distribution level, and criteria for determining habitat required to support a population should incorporate longterm occupancy data as well as movement distances in order to include all habitat necessary to support continued occupancy by the population. The process we used is described below.

To delineate proposed revised critical habitat, we first determined occupancy within the extant range of the Quino checkerspot butterfly. Occupancy status was determined using occurrence data from the Carlsbad Fish and Wildlife Office GIS database and associated survey reports. Areas containing occurrence records from 1999 or later were considered currently occupied. We then determined which areas were occupied at the time of listing by comparing survey and collection information to descriptions of occupied areas in the final listing rule published in the Federal Register on January 16, 1997 (62 FR 2313). Core occurrence complexes recorded within 4 years of listing that contained repeated observations of a large number of individuals (relative to all known occupied locations), and were more than 4 mi (6.4 km; the maximum recorded Edith's checkerspot dispersal distance) from other occurrence complexes known to be occupied at the time of listing were also considered to be occupied at the time of listing on the basis that these parameters indicate such areas were not colonized postlisting.

Once we determined the extant range of the subspecies and identified all occupied habitat, we used the following rule set to identify areas for inclusion in this proposed revision to designated critical habitat. As described further in the Background section above, core occurrence complexes appear to be population density centers likely to contain source habitat based on
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geographic size, number of reported individuals, repeated observations, and/or documented reproduction. Therefore, we believe that core occurrence complexes are the most likely to persist into the future and provide emigrants to other populations, and, as such, are essential to the recovery of this subspecies. We first identified seven core occurrence complexes that were known to be occupied at the time of listing (Warm Springs Creek, Skinner/ Johnson, Vail Lake, Sage, Wilson Valley, Tule Peak/Silverado, Otay Mountain). Furthermore, we identified two new core occurrence complexes (Bautista Road and La Posta/Campo) that were not known to have been occupied at the time of listing (see Background section above).

Within the geographical area occupied by the subspecies at the time of listing, to delineate all the core occurrence complexes we grouped occurrence records together that were within 0.6 mi (1 km) of each other as one core occurrence (as described furthe

FOR FURTHER INFORMATION CONTACT Jim Bartel, Field Supervisor, U.S. Fish and Wildlife Service, Carlsbad Fish and Wildlife Office, 6010 Hidden Valley Road, Carlsbad, CA 92011; telephone 7604319440; facsimile 7604315901. If you use a telecommunications device for the deaf (TDD), call the Federal Information Relay Service (FIRS) at 800 8778339.