Natural history and population ecology of a rare pierid butterfly, Euchloe ausonides insulanus Guppy and Shepard (Pieridae).

摘要

The island marble butterfly, Euchloe ausonides insulanus Guppy and Shepard 2001(Pieridae) is one of the most restricted butterfly endemics in the continental United States. While much research has been devoted to understanding the species level biology of the large marble, Euchloe ausonides Lucas 1852 (Pieridae), relatively little is known about the biology of the subspecies, E. ausonides insulanus. This thesis focuses on the biology, natural history and population ecology of E. ausonides insulanus. Conservation and management issues related to the biology and population ecology of E. ausonides insulanus are discussed in the context of my research findings.;Chapter 1 summarizes the first comprehensive field study of the biology, morphology and behavior of each immature stage (egg, larva and pupa) of Euchloe ausonides insulanus.;In Chapter 2, I investigate the relationship between egg-laying patterns and host plants Brassica rapa L. var. rapa, Sisymbrium altissimum L., and Lepidium virginicum var. menziesii (DC) Hitchc. I have two overall research objectives; (1) I explore how adult biology may influence egg-laying patterns using descriptive studies that focus on adult phenology, mating behavior, egg phenology and egg dispersion and (2) I further explore egg-laying patterns related to host plant traits, density and patch size. This study aims to help researchers predict the occurrence of eggs and larvae among host plants and host plant patches and design host plant habitat that maximizes oviposition site selection by E. ausonides insulanus.;In Chapter 3 I quantify larval survival and mortality that may contribute to the rarity of E. ausonides insulanus. This study is the first to provide insights into the key role of immature stages in the demography of E. ausonides insulanus. The objectives of this study were to (1) assess whether survivorship differed among the three host plant species (one native and two non-native host plant species), (2) assess which factors cause mortality (e.g., predation and deer herbivory) of immature stages and (3) determine which immature stages (egg, instars I-V larval stages) are most vulnerable to different sources of mortality. This study also showed that the only known native host plant, L. virginicum var. menziesii supported the highest percent survivorship from the egg stage to larval instar IV but that L. virginicum var. menziesii habitat was susceptible to offshore storms and tidal flooding that likely contributed to an observed local population extinction of E. ausonides insulanus from one research site over the course of the four year study.;In Chapter 4, I explore the use of an alternative native host plant in an effort to enhance prairie remnants to support rare butterfly populations. Turritis glabra L., tower mustard, a potential native host plant, was selected for research. This study experimentally tested restoration treatments to foster establishment of T. glabra in introduced grasslands, compared plant traits of T. glabra and B. rapa as they related to E. ausonides insulanus oviposition site selection (based on research described in Chapter 2), tested whether E. ausonides insulanus would oviposit on T. glabra and tested whether T. glabra could support egg and larvae development.;Finally, in Chapter 5, I discuss key ecological issues related to the conservation and management of E. ausonides insulanus. My findings show that a combination of factors likely influence overall low population numbers and local population extinctions related to patch dynamics in E. ausonides insulanus. Thus, managers should consider multiple management strategies to maintain and increase abundance of E. ausonides insulanus at American Camp including further experimental research to better understand the ecological mechanisms that contribute to overall population abundance. (Abstract shortened by UMI.)