I am working on invertebrate marine population genetics, connectivity and phylogeography. My main interest stands in understanding the evolutionnary processes driving genetic diversity and speciation in coral reef associate bivalves. To answer these questions I combine field work, observation studies, molecular biology and genetic statistics.

Patterns of lineage diversification in rabbitfishes

This project was conducted at the IRD research center of Noumea (New Caledonia)  in 2006 under the supervision of Dr. Philippe Borsa.
Fishes of the tropical Indo-Pacific family Siganidae comprise 28 species, characterized by their body proportions and their colour patterns. A mitochondrial phylogeny of 20 Siganidae species was produced to infer their evolutionary history. Three distinct, major clades were found, that also correspond to the early radiation of the family into three major ecological types: fusiform species that also live in schools on the inshore reef flats (S. canaliculatus, S. fuscescens, S. luridus, S. rivulatus, S. spinus, S. sutor); deep-bodied species including brightly coloured ones whose adults live in pairs on the reef front (S. corallinus, S. doliatus, S. puellus, S. punctatus, S. virgatus, S. vulpinus), and species that live in small schools in mangroves, estuaries, and estuarine lakes (S. guttatus, S. javus, S. lineatus, S. randalli, S. vermiculatus); and a third clade including a cosmopolitan species, S. argenteus, the only species of the family known to possess a pelagic, prejuvenile stage and S. woodlandi, a recently described species from New Caledonia and morphologically close to S. argenteus. The partition of the genus into two sub-genera, Lo (erected for S. vulpinus and 4 related species possessing a tubular snout) and Siganus (all the other species), had no phylogenetic rationale. The present results indicate that the tubular snout, which apparently results from ecological specialization, is a recent acquisition within the deep-body clade. The western Indian Ocean endemic S. sutor appeared as the sister-species of the Red Sea endemic S. rivulatus within a well-supported sub-clade that also included S. canaliculatus and S. fuscescens. S. spinus did not appear as sister-species to S. luridus. S. lineatus haplotypes formed a paraphyletic group with S. guttatus, and an early isolation of Maldives S. lineatus was suggested. Unexpectedly, S. randalli did not appear as the sister-species of S. vermiculatus, but its haplotypes instead were embedded within the West Pacific S. lineatus haplogroup, suggesting recent introgression. Among currently-recognized  sister-species with parapatric distribution, S. doliatus and S. virgatus haplotypes formed a single, unresolved haplogroup, as did S. unimaculatus and S. vulpinus. Conversely, the occurrence of two distinct clades within S. fuscescens was confirmed. 



sarah.lemer@gmail.com
sarahlemer@oeb.harvard.edu
Dept. of Prganismic and Evolutionary Biology
Museum of Comparative Zoology
Harvard University
26 Oxford St.
Cambridge MA, 02138
USA
Phone: 1 617 496-5308
Fax: 1 617 496-5854