Human-mediated extirpation of lowland native insects in Hawaii
Date:2013 to 2016
The Hawaiian Islands support the greatest levels of biodiversity per unit area in the World. The geological history of the archipelago has allowed certain early colonizing groups to undergo adaptive radiations on successively emergent volcanic islands. I have been studying all of the estimated 425 native species of the beetle family Carabidae (predaceous carabid beetles), and have studied the patterns of extinction in various groups based on historical and present-day collections from the field. Recent collaboration with Dr. Nick Porch, Deakin University, Melbourne, has allowed the study of the prehistoric distributions of these native species on the island of Kauai. Makauwahi Cave in southern Kauai was previously a paleolake that developed within a limestone formation, and has strata documented to span 10,000 years b.p. It contains organic material derived from the neighboring slopes of Haupu, a small prominence 445 m high. Dr. Porch has taken samples from pre-Polynesian strata in the cave’s floor and sorted out subfossil fragments of all the insects and other arthropods. Based on my comprehensive knowledge of the carabid beetles, I am identifying the various fragments and establishing the presence of the various species in the various strata. We have recovered both fragments of extant species, and also fragments that represent species previously unknown to science. For the present-day species, the cave deposit specimens universally represent the lowest elevations that these species have been collected. In one case—the beetle species Tachys oahuensis—the species is known from other Hawaiian islands but was never collected on Kauai. The specimens of extinct species include a number of heads, pronota, and elytra that can be assigned to the genus Blackburnia, a genus of 133 native Hawaiian species that I revised 14 years ago with Dr. Elwood Zimmerman, CSIRO, Canberra. Dr. Porch and I are in the process of re-associating these body parts to determine the actual number of species known only from the fossil deposits. This re-association involves two major approaches. First the specimens must be of appropriate relative sizes to have been parts of one beetle; i.e. comprise a functional individual. Second, the individual parts will be entered into a phylogenetic analysis previously completed for all extant species. The results of this exercise will be two-fold: 1, we will re-associate separate body parts because they will group together in the phylogenetic analysis; and 2, we will learn the phylogenetic relationships of the extinct species. This will confirm their association as different body parts characterizing a single species, and we will learn more about the relatives of those species remaining in Kauai today. We have preliminary data re-associating one head and one pronotum.
This project is part of a larger project headed by Dr. Porch that is investigating patterns of extinction across many Pacific islands in French Polynesia and Micronesia. The ultimate goal of the project is to illustrate the impact of human colonization and land use on native biodiversity. Even though many of the species discovered in fossil deposits are extinct, they still add valuable information toward our understanding of the species that remain. This information will aid efforts to conserve native biodiversity by focusing on the human impacts of native populations.
This work is ongoing. Evantual audience will be the general public of Hawaii and other Pacific nations.
This work is ongoing.
- United States of America
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