Journal Article

Evolution and species boundaries of the portieria-complex (Rhodophyta: Gigartinales)

Verbruggen, H, Leliaert, F, Calumpong, H, De Clerck, O, Payo, DA

2009

Overview

Portieria hornemannii is a common and widespread Indo-Pacific red seaweed. Our studies suggest, however, that P. hornemannii does not represent a single species. Extremely high levels of diversity, based on mitochondrial (cox1, cox2-3 spacer) and chloroplast (rbcL, rbcL-S spacer) markers, are encountered among isolates spanning the entire geographical range of the 'species'. Model based species delineation based on lineage through time plots reveal at least 27 species. These results are corroborated by assessments of DNA barcoding gaps. In the Philippines, these individual lineages possess a near exclusive distribution pattern in the Central Visayas region, with most species restricted to one or a few localities. These observations are in stark contrast with the diversity pattern observed in the northern Batan Island, Batanes where a high sympatric diversity is encountered. Given the high diversity encountered at small geographical scales, we used low-copy nuclear genes (EF2 and Actin) to assess for reproductive isolation among the various lineages encountered in the Philippines. Gene trees of nuclear markers are in full concordance with the phylogenies based on organelle genes, suggesting complete reproductive isolation under natural conditions. Current efforts are dedicated at understanding the causes of this unexpected diversification, which apparently has not been accompanied by significant morphological differentiation. Ecological modes of speciation driven by herbivore interactions are investigated. The algae in question are grazed upon by Aplysia sea hares and are known to produce a wide variety of halogenated monoterpenes which probably act as antigrazing defense mechanisms.

• Subject: Aplysia / Gigartinales / Marine / Portieria hornemannii / Rhodophyta