Investigations on Reproductive Affinities in Red Algae

Abstract

Allopatric speciation is the most widely accepted model proposed for speciation: once a population is divided by extrinsic barriers, genetic flow is interrupted between these disjunct subpopulations, and reproductive isolation is established as a by-product of the accumulation of genetic changes in these isolated populations. According to the biological species concept (Mayr, 1942), the evolution of reproductive isolation is a defining characteristic of speciation, and reproductive isolation contributes to the diversification of species by creating genetically independent lineages. It had been generally thought that isolation is more difficult in marine populations, with fre- quent gene flow over large distances (Hoffmann, 1987; van den Hoek, 1987; Norton, 1992; Shanks et al., 2003), as there seem to be far fewer extrinsic barriers in marine environments than in terrestrial ones (Palumbi, 1994). Such attributes are considered to limit the isolation of a species into allopatric populations less frequently, making allopatric speciation rarer (Mayr, 1954). However, recent molecular analyses have revealed great genetic divergences among/within populations in various marine organisms, including macroalgae, and thus, the generalization that speciation must be rare in marine habitats appears to be incorrect.