Toward Propagation of Host Plants for Endangered Butterflies: Effect of Temperature on Germination Rates in Viola papilionacea

DeRosa University Center, Ballroom

Effective restoration and management of herbivorous insect populations requires knowledge of both insect and host. Speyeria callippe and Speyeria adiaste are butterfly species of conservation concern in California that depend on specific violet hosts (Viola pedunculata and Viola purpurea respectively). Perturbation of violet host plants has been implicated in playing a role in declines of Speyeria butterfly species generally, and studies are needed to increase basic understanding of larval ecology as well as for management and restoration of particular species. Our lab has been using a widely available eastern species, V. papilionacea to advance understanding of larval ecology in S. callippe and S. adiaste because the hosts of these two butterflies are not commercially available. An important next step is to establish greenhouse stocks from seed or transplants to confirm our findings using native host plants. Accordingly this study focuses on appropriate techniques for breaking winter dormancy in the commercially available Viola papilionacea. We focused on addressing two questions to pave the way for future research on coast range Viola-Speyeria interactions: 1) what is the most effective way to break dormancy and achieve germination in Viola papilionacea?; 2) does germination rate differ between dried seeds from the previous spring compared with dried seeds from the previous fall? To answer these questions, three temperature treatments were used (4ËsC; -20ËsC; and ambient greenhouse). Our results show a range of germination rates from 34-53% for 4ËsC and greenhouse treatments compared with ~10% germination for -20ËsC treatments, indicating greenhouse conditions are sufficient for germination.