Phylogeography of giant wood spider Nephila maculata in the West Pacific.
Currently in Taiwan, most phylogeographic studies of terrestrial animals focus on vertebrates. Results from most studies show that many terrestrial vertebrates can be divided into eastern and western groups according to their population genetic structure. It is suggested that the common phylogeographic pattern exhibited by so many taxa results from the following factors: 1) the formation of land bridge during glacial periods of the Pleistocene, which enhanced migrations between mainland China and Taiwan, and 2) the isolation resulting from the upheaval of the Central Mountain Range, which led to differentiation of eastern and western populations. However, this traditional view might not be applicable to arthropods inhabiting low-elevated tropical or subtropical areas, shch as giant wood spider Nephila maculata. In this study, we examine if the phylogeographic pattern of the widely-distributed N. maculata is more congruent with recent regional ocean currents than with ancient glacial geographic events. Isozyme electrophoresis (20 loci from 17 enzymes) and mitochondrial partial sequence (COI-Leucine tRNA-COII region, 950 bp) will be used to evaluate the following hypotheses: 1) existing N. maculata invaded Taiwan during the last interglacial period by dispersing through the sea (about 15,000 years ago), and 2) N. maculata entered Taiwan via land bridge formed during the glacial periods of Pleistocene (about 2,000,000 years ago). A prediction derived from hypothesis 1 is that no significant variation exists between eastern and western populations, and Taiwanese and West Pacific populations exhibit similar genetic structuring. According to hypothesis 2, it can be expected that the genetic structure of western populations differs markedly from that of eastern populations, but shares certain common feature with that of mainland populations.
Updated: Mar-10-2014 01:22:51 (Taiwan, GMT+08:00).