Meeting Abstract
16.2 Jan. 4 Phylogeography of Pericharax heteroraphis (Porifera) from the Great Barrier Reef BENTLAGE, Bastian*; W�RHEIDE, Gert; Geoscience Centre of the University of G�ttingen, Germany; Geoscience Centre of the University of G�ttingen, Germany b_bentlage@gmx.net
Resolving the biogeographic histories of tropical marine invertebrates remains a challenge. Sponges (Phylum Porifera) are well-suited models for such studies due to the restricted dispersal capabilities of their short-lived larvae and thus the high probability of preservation of past population genetic structures. We employed two unlinked nuclear markers to uncover the phylogeographic patterns of the common coral reef sponge Pericharax heteroraphis from the SW Pacific, focussing on the Great Barrier Reef (GBR). A new marker system for sponges was developed, the second intron of the ATP synthethase beta subunit-gene, and analysed together with nuclear rDNA internal transcribed spacer sequences (ITS1-5.8S-ITS2 region plus flanking gene sequences). We used Single-Stranded Conformation Polymorphism (SSCP) analysis to phase alleles and investigated its applicability to aid poriferan phylogeographic and population genetic studies. We discovered very low variation among rDNA sequences (0.3% to 1%) and the phylogeographic patterns derived from these sequences appear to be the result of persistent ancient polymorphisms rather than population history. The intron, in contrast, provided better resolution of population genetic structures. SSCP analysis proved to be an effective tool for phasing alleles of about 400bp length. Our analyses suggest a past population subdivision between the northern and central GBR followed by a subsequent range expansion of subpopulations. The patterns uncovered differ from those of previous studies on Leucetta chagosensis, a close relative of P. heteroraphis. These discrepancies might be attributed to different responses of both taxa to environmental changes, like small sea-level oscillations. Our hypothesis awaits corroboration using an extended geographic sampling scheme.
