Comparisons to the Century Before: The Legacy of R. C. L. Perkins and Fauna Hawaiiensis as the Basis for a Long-Term Ecological Monitoring Program

Date
1997-10
Authors
Liebherr, James K.
Polhemus, Dan A.
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Publisher
University of Hawaii Press
Abstract
As one means of assessing the impact of the past 100 yr of development and biological alteration in Hawai'i, the damselfly (Odonata: Coenagrionidae) and carabid beetle (Coleoptera: Carabidae) collections of R. C. L. Perkins made in the l890s are compared with similar collections made one century later during the 1990s. Two islands that have experienced very different histories of development are compared: O'ahu and Moloka'i. Of eight native damselfly species originally inhabiting O'ahu, one has been extirpated from the island, another is now reduced to a single population, and three more are at risk. Of the eight species originally found on Moloka'i, by contrast, there is only one species that has not been rediscovered, although there is reasonable probability that it has simply eluded capture because of inherent rarity, whereas the remaining species retain large and stable populations. Capture frequencies (based on specimens collected per decade) are lower now than in the preceding century for most species on O'ahu, even allowing for modem collectors retaining fewer specimens. The only species on O'ahu for which captures have increased between the l890s and the 1990s are those that breed away from lotic and lentic habitats, indicating a severe negative impact from introduced aquatic biota for species that breed in such freshwater situations. On Moloka'i, all damselfly species except one have higher capture rates now than in the l890s, explainable in large part to improved access to previously remote terrain. Among the Carabidae studied, 1990s surveys on Moloka'i have found 12 of 15 species Perkins sampled in the 1890s. Overall, recent surveys have failed to rediscover five species, all of which have been relatively rarely encountered over all decades of the past century. Recent surveys on O'ahu have recollected 17 of the 21 species Perkins found in the 1890s. The most dramatic change in the O'ahu carabid fauna over the past 100 yr is the extinction of the most common O'ahu species of the 1890s, Colpocaccus tantalus (Blackburn). This species was broadly distributed across the island, possessed a well-developed flight apparatus, and accounted for 39% of the specimens captured in the 1890s. It has not been collected since 1940 in spite of intensive collecting during the 1950s and 1990s. The elevational preference of C. tantalus was lower than that for the aggregate balance of the O'ahu carabid fauna, suggesting an altitudinally associated factor in the extinction: most likely ants such as Pheidole megacephala (F.). The loss of a previously dominant generalist species is viewed as an ecological catastrophe, substantially different in quality from extinction of geographically restricted island specialists.
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Citation
Liebherr JK, Polhemus DA. 1997. Comparisons to the century before: the legacy of R. C. L. Perkins and Fauna Hawaiiensis as the basis for a long-term ecological monitoring program. Pac Sci 51(4): 490-504.
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