Molecular ecology of rotifers: from population differentiation to speciation

A. Gómez

Abstract:

The advent of cost-effective molecular tools allowing the amplification of minute amounts of DNA has opened the field of Molecular Ecology for rotifers. The few studies performed to date have yielded unexpected and exciting results. Here I will review these studies and discuss their importance for the investigation of sibling species complexes, clonal structure, population structure, and phylogeography in rotifers. In the past few years I have been involved in the analysis of genetic diversification and speciation in zooplanktonic faunas focusing in the rotifer species complex Brachionus plicatilis. The species in this complex reproduce through cyclical parthenogenesis and disperce passively through long-lived resting eggs. The use of sequence and microsatellite variation to investigate the population genetics, phylogeographic paterns and phylogenetic relationahips in this complex, in the context of a good background knowledge of its ecological characteristics, mating behaviour, and temporal population dynamics have yielded surprising insights into the processes shaping its genetic diversity. Rotifers display strong population differentiation for natural markers, and, contrary to the perceived wisdom, deep phylogeographic structure. Persistent founding effects, but also at a local scale the impact of gene flow (Monopolisation hypothesis), are responsible for these patterns. Instances of recent long-distance transcontinental migration have been also revealed. Our data indicates that the history and chance might play a major role in the genetic differentiation and speciation processes of these organisms and that migration is not as pervasive as previously thought.

(Department of Biological Sciences, Univeristy of Hull, Hull, HU6 7RX, U.K., e-mail: a.gomez@hull.ac.uk)

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