Patterns of reproduction in four Washington State populations of Taylor’s checkerspot (Euphydryas editha taylori) during the spring of 2010

As little as 50 years ago, Taylor’s checkerspot (Euphydryas editha taylori), a subspecies of Edith’s checkerspot (E. e. editha), could be frequently encountered in forest openings, remnant prairies, and balds from the southern Willamette Valley of western Oregon, north through the Puget Trough and Olympic Peninsula, and as far north as Vancouver Island, British Columbia (Dornfeld 1980, Guppy and Shepard 2001, Pyle 1974, 2002). In Oregon, Taylor’s checkerspot butterflies flew in such great numbers as to be described by Ernst Dornfeld (1980) as to “fairly swarm by the thousands”. However, changes in land usage, habitat degradation, and succession have conspired to limit butterfly occurrence to isolated and notably disjunct populations throughout western Oregon, Washington, and British Columbia.

In Oregon, Taylor’s checkerspot populations appear to have fallen to the advance and dominance of tall, exotic grasses (Arrhenatherum elatius, Brachypodium sylvaticum, Festuca arundinacea) which out-compete the shorter, native bunch-grasses (Wilson and Clark 2001). When these grass species dominate Taylor’s checkerspot habitat, they reduce the abundance of larval and adult butterfly resources (Severns and Warren 2008) and appear to interfere with fitness related behaviors (Severns 2010), restricting high quality reproductive habitat to relatively small areas in a comparably larger degraded
prairie landscape (Severns and Warren 2008, Severns 2009). Extant Taylor’s checkerspot populations in Washington State appear to occupy floristically higher quality remnant prairies when compared to Oregon sites (Severns personal observation) and appear to have substantially larger areas of what appear to be high quality reproductive habitat. Yet, biologists working with this species in Washington report local clustering of adults and oviposition sites (M. Linders, A. Potter pers. com.). These observations suggest there are habitat characteristics, even within a larger landscape of ostensibly overall, higher quality habitat, that are associated with the selection of reproductive habitat and adult presence. For the conservation of Taylor’s checkerspot, it is important to identify and quantify habitat conditions that are associated with, as well as, conditions that discourage butterfly oviposition. Identification of reproductive habitat and characterization of the conditions will aid site-specific management, habitat restoration, assessment of reintroduction site suitability, and provide a reference point to which
changes in habitat conditions from exotic species invasions, succession, land management activities, and climate change can be compared.