Effect of island geological age on the arthropod species richness of Azorean pa...

• Author(s): Borges, Paulo A. V. ; Brown, Valerie K.
• Date: 1999
• Persistent ID: http://hdl.handle.net/10400.3/1411
• Origin: Repositório da Universidade dos Açores
• Subject(s): Ecology; Patterns of Diversity; Island Age; Island Biogeography; Pasture Arthropods; Standard Area Sampling; Species Richness; Time Hypothesis
• Document Type: Article
• Language: English

Description

Copyright © 1999 The Linnean Society of London. Species richness of six pasture arthropod assemblages (total arthropod species, total herbivore species, sucking and chewing herbivores, total predatory species and spiders) were regressed against several geographical variables (area, distance from the nearest mainland, maximum elevation and geological age of the islands) of three Azorean islands (S. Maria, Terceira and Pico). The species were sampled by the fixed-quadrate size sampling method and the results obtained are consistent with the geological age hypothesis, i.e. the species richness of the six indigenous arthropod assemblage’s increases with the geological age of the islands, both at local and regional scales. Higher values of indigenous and endemic species richness were consistently found on the older island (S. Maria), and the lowest values on the most recent island (Pico). Moreover, when considering the age of Faial (an older island probably once connected with Pico) as a estimate of the age of Pico, correlations between species richness and island age were improved, thereby strengthening the relationship. The older island (S. Maria) has more specialized herbivores and a greater proportion of herbivores in relation to predatory arthropods. Ecological and biogeographical studies in the Azores should take into account the effects of the time each island has been available for colonization and evolution.