Applied conservation research of the wēkiu bug in Hawai΄i: life table analysis, population genetics, and phylogenetics create a holistic view of a rare and unique species

Abstract

The wekiu bug (Nysius wekiuicola Ashlock and Gagné 1983) is a flightless carnivore endemic to the dormant Mauna Kea volcano, on the Big Island of Hawaii. Wekiu bugs only occur between 3,350m (11,500ft) and the summit at 4,205m (13,796ft) in an environment described as high alpine desert. Remarkably, the main nutrient input to the summit comes from aeolian deposition of arthropods blown in from lower elevations. The wekiu bug‟s habitat is subject to dramatic temperature extremes, with daily fluctuations in their microhabitat caused by solar daytime heating and rapid evening cooling. The wekiu bug was, until fall 2011, a candidate for listing under the Endangered Species Act. Detailed ecological data of the wekiu bug are necessary for informed management decisions. I briefly present an overview of insect conservation research and the field‟s current status in Hawaii as a primer to the research conducted for this dissertation. I investigated unknown aspects of the wekiu bug‟s life history using life table experiments and degree day modeling, showing how the wekiu bug can develop in its harsh natural environment. They have a low reproductive output in captivity, develop most quickly at 30-32°C, exhibit an intrinsic rate of increase (r) of 0.045 in field simulations, and require 622 degree days for one generation. This developmental requirement is only achieved for a maximum of 8.5 hours of solar heating on Mauna Kea. This lab-based study helped explain field observations and trapping patterns. Also, using population genetic analyses of mtDNA haplotype diversity, I describe the potential impacts of habitat disturbance and ecosystem alteration in two distinct populations. Finally, I investigated the evolution of the wekiu bug within the Nysius lineage using DNA sequence from 29 Nysius species. Its closest relatives are seed feeding Nysius, on Maui and Hawaii islands, and there is considerable taxonomic revision needed in the genus. In the appendices of this dissertation, I present a pictorial key of the Hawaiian Nysius for identifying the Nysius in Hawaii, and I provide a summary of the technical reports of wekiu bug monitoring from 2005-2011, with maps for resource managers‟ use.