Range-wide population status of the Appalachian Grizzled Skipper and the factors that may influence its population persistence
Dates
Start Date
2020-10-01
End Date
2023-12-31
Summary
The FWS considers the Appalachian grizzled skipper (AGS, Pyrgus wyandot) a Species of Concern and is requesting key information on this species for a status review. According to the RFP, FWS has given AGS full species status, however, AGS’s taxonomic status is considered controversial. Some lepidopterists recognize P. wyandot as a full species whereas others consider it a subspecies, P. centaureae wyandot (pers. comm. B. Leppo, PA Natural Heritage Program; in Chazal et al., 2004). Regardless, FWS can still list AGS as threatened or endangered at the species or subspecies level. In this proposal, AGS will be treated as P. c. wyandot for simplicity during genetic analysis (Objective 4). The AGS is a small butterfly that once occupied [...]
Summary
The FWS considers the Appalachian grizzled skipper (AGS, Pyrgus wyandot) a Species of Concern and is requesting key information on this species for a status review. According to the RFP, FWS has given AGS full species status, however, AGS’s taxonomic status is considered controversial. Some lepidopterists recognize P. wyandot as a full species whereas others consider it a subspecies, P. centaureae wyandot (pers. comm. B. Leppo, PA Natural Heritage Program; in Chazal et al., 2004). Regardless, FWS can still list AGS as threatened or endangered at the species or subspecies level. In this proposal, AGS will be treated as P. c. wyandot for simplicity during genetic analysis (Objective 4).
The AGS is a small butterfly that once occupied nine states (MD, MI, NC NJ, NY, OH, PA, VA, and WV) and the District of Columbia. Now only a few known AGS colonies remain and AGS has not been observed in more than a decade in most of its former range (pers. comm.: B. Leppo; S. Olcott, WV Department of Natural Resources; S.M. Roble, VA Department of Conservation & Recreation; J. Selfridge, MD Department of Natural Resources; D.F. Schweitzer, NJ Department of Environmental Protection, retired; M. Schlesinger and E. White, NY Natural Heritage Program; D. Cuthrell MI Natural Features Inventory; J. Radcliffe, NC Natural Heritage Program). Presently, known AGS colonies are small and scattered across its historical range, often isolated by considerable distances. The largest known colony in the mid-Atlantic states is estimated at <30 individuals (pers. comm.: S. Olcott). The precipitous decline of AGS is primarily attributed to ecological succession that shades out the AGS’s primary host plant, Canada cinquefoil (Potentilla canadensis), and aerial insecticide applications (Parshall, 2002; Chazal et al., 2004; Allen, 2009; Schweitzer et al., 2011). Furthermore, the genetic relationships between colonies is unknown, making it difficult to define distinct populations that may require separate management. For example, it is only suspected that a colony in Virginia and a colony in West Virginia are from the same population based on their proximity to each other (pers. comm.: S. Olcott; S.M. Roble). Although not seen in recent years, populations in MI differ from those in the Appalachian region in larval characteristics, genitalia and habitat (Cuthrell, 2007). The small number of known colonies, the small number of individuals per colony (Chazal et al., 2004) and the lack of information on the genetic relationships among the colonies, populations, and metapopulations render AGS vulnerable to extinction (Saccheri et al., 1998).
In general, AGS occupy patchy habitats with Canada cinquefoil and nectaring plants on the south slopes of shale, in open habitat with nearby trees. However, the Michigan populations differ from typical AGS in larval food plant (wild strawberry, Fragaria virginiana), habitat (limestone glades and alvars), and in larval appearance (pinkish brown, Cuthrell, 2007; Schweiter et al., 2011). Whereas the basic biology of AGS has been studied (Parshall, 2002; Chazal et al., 2004; Allen, 2009; Schweitzer et al., 2011), considerable knowledge gaps remain about the current status of AGS populations. For example, it is not known why most of the seemingly ideal habitat remains unoccupied by AGS (pers comm: J. Selfridge; S. Olcott; S.M. Roble; B. Leppo). Genetic relationships among the three recognized P. centaureae subspecies that occur in North America are also unclear. Besides P. c. wyandot, there is a widespread subspecies in Canada (P. c. freija), as well as a Rocky Mountain subspecies, P.c. loki. In recent years, full genome sequences for numerous species of skippers (Family Hesperiidae) have revealed cases of convergence in wing patterns that have mis-lead earlier classification efforts based on morphology, highlighting the utility of genomic approaches to gain rapid insights into this biodiverse group (Li et al., 2019). These knowledge gaps hamper the implementation of management strategies for mitigating threats to the AGS.
A comprehensive study to assess the status of AGS across its range and the factors that control AGS population persistence involves research and monitoring at the colony, population, metapopulation, and species scales. Therefore, this study will utilize a multi-scale approach, combined with population genomic characterization, to inform conservation and management efforts to protect the AGS. Whereas research at the colony scale can produce valuable information about that colony, a metapopulation approach is needed to ensure the regional persistence of the species (Akçakaya et al., 2007). At the colony scale, for example, locating previously undocumented colonies can lead to establishing insecticide-free zones and controlling ecological succession. At the population and metapopulation scales, conservation management may include establishing habitat corridors between populations to facilitate gene flow and maintenance of genetic diversity. Furthermore, clarification of the phylogenetic relationships among the AGS subspecies in this study will help guide FWS conservation strategies at the species or subspecies scale.
Objectives:
Analyze spatial habitat data to identify possible locations that appear suitable for undocumented AGS colonies.
Conduct surveys for AGS at current and historical colonies and at sites selected in objective 1.
Measure AGS habitat characteristics at each survey location selected in Objective 2.
Determine the genetic structure and relationship among the AGS colonies across the species range and among the three North American P. centaureae subspecies: P. c. wyandot, P.c. freija and P. c. loki.
