Algae. 2011; 26(1): 21-32.
[Review] Insights into evolution and speciation in the red alga Bostrychia: 15 years of research
Giuseppe C. Zuccarello1,* and John A. West2
1School of Biological Sciences, Victoria University of Wellington, P. O. Box 600, Wellington, New Zealand 2School of Botany, University of Melbourne, Parkville VIC 3010, Australia
Studies of the red algal genus Bostrychia over the last 15 years have made it a model system for many evolutionary processes within red algal species. The combination of newly developed, or first employed methods, in red algal species studies has made Bostrychia a pioneer genus in intraspecific studies. Bostrychia was the first genus in which a mitochondrial marker was used for intraspecific red algal phylogeny, and the first for which a 3-genome phylogeny was undertaken. The genus was the first red alga used to genetically show maternal plastid and mitochondria inheritance, and also to show correlation between cryptic species (genetically divergent intraspecific lineages) and reproductive incompatibility. The chemotaxonomic use, and physiological function of osmolytes, has also been extensively studied in Bostrychia. Our continuous studies of Bostrychia also highlight important aspects in algal species studies. Our worldwide sampling, and resampling in certain areas, show that intensive sampling is needed to accurately assess the genetic diversity and therefore phylogeographic history of algal species, with increased sampling altering evolutionary hypotheses. Our studies have also shown that long-term morphological character stability (stasis) and character convergence can only be correctly assessed with wide geographic sampling of morphological species. While reproductive incompatibility of divergent lineages supports the biological species nature of these lineages, reproductive incompatibility is also seen between isolates with little genetic divergence. It seems that reproductive incompatibility may evolve quickly in red algae and the unique early stages of fertilization (e.g., gametes covered by walls, active movement of spermatium nuclei to the distant egg nucleus), also well investigated in Bostrychia,? may be key to our understanding of this process.
Keywords : evolution; molecular marker; organelle inheritance; osmolyte; phylogeny; phylogeography reproductive compatibility; speciation