Seed Germination InViola pedunculataandViola purpureaSUBSP.Quercetorum(Violaceae), Critical Food Plants For Two Rare Butterflies

Abstract

Viola L. are the larval food plants for a charismatic group of butterflies in Speyeria Scudder, 1872, which contains several rare and declining taxa in California and across North America. A current impediment to restoring Viola in California is a lack of knowledge of germination requirements. In this study we focused on determining conditions for successful germination of V. pedunculata Torr. & A. Gray, the food plant of the federally listed endangered Speyeria callippe (Boisduval, 1852) subsp. callippe, and V. purpurea Kellogg subsp. quercetorum (M.S. Baker & J.C. Clausen) R.J. Little, the food plant of the imperiled southern Coast Range butterfly, S. adiaste (Edwards, 1864) subsp. clemencei (Comstock, 1925). We examined the effects of gibberellic acid, seed color, elaiosome removal, and duration of stratification on germination success. We found that both taxa germinate exceptionally well (73–100%) after a prolonged period of after-ripening and 6–10 wk of stratification. Gibberellic acid and elaiosome removal did not have strong effects on germination of V. pedunculata, and both dark and mottled V. purpurea subsp. quercetorum seeds germinated equally well. We make recommendations for successful lab germination of these two native violets, setting the stage for additional research to help restore their populations as well as their herbivores.