Endemism and ecological islands: the ostracods from Jamaican bromeliads

Abstract

1. The inhabitants of ecological islands, such as the phytolemata of bromeliad plants, provide an opportunity to examine the genetic patterns resulting from island radiations and draw inferences about modes of speciation.2. Allozyme electrophoresis, as well as mitochondrial DNA and morphological analyses, were employed to delimit species boundaries and assess the population genetic structure of the ostracods from bromeliads on the island of Jamaica.3. Nine species from the genus Elpidium were both sexually reproducing and endemic to the island. The other commonly encountered ostracod genus, Candonopsis, was represented by at least two sexually reproducing species.4. Most Elpidium species showed very restricted distributions, low heterozygosity, and marked gene pool fragmentation, suggesting that population bottlenecks have occurred frequently. Whether founder events played a causal role in the diversification of these ostracods remains uncertain, but bromeliad habitats seem to be a source of high biodiversity, and may represent an ideal setting for extensive allopatric speciation.