Meeting Abstract

15.2  Friday, Jan. 4  Do shifts in host use or larval development drive speciation in the sea? A comparative study of herbivorous sea slugs. KRUG, P.J.*; VENDETTI, J.E.; TROWBRIDGE, C.D.; California State University, Los Angeles; California State University, Los Angeles; Oregon Institute of Marine Biology pkrug@calstatela.edu

Marine biodiversity presents a challenge to current theory of allopatric speciation, given the lack of physical barriers to gene flow and the high dispersal potential of many organisms, either as pelagic adults or as planktonic larvae. Recent studies of invertebrates, fish and marine mammals suggest ecological speciation can proceed in sympatry, but this remains controversial. For specialized consumers or epibionts, disruptive selection on host or habitat choice may drive speciation. Alternatively, life-history shifts from dispersive larvae to short-lived, non-feeding larvae may reduce gene flow among populations, and shrink the scale at which populations diverge in allopatry. Non-dispersive life histories could also act synergistically with selection, together increasing local adaptation to newly colonized niches. Sea slugs in clade Sacoglossa, the most host-specialized marine herbivores, are an excellent system with which to explore how shifts in host or life history alter patterns and rates of speciation. We present a comparative analysis of this group, using a molecular phylogenetic framework of 200 taxa to identify traits that influence the geographic and temporal mode of speciation. Bayesian and maximum likelihood methods of ancestral character state reconstruction and correlated trait evolution will be used to test the evidence for sympatric speciation by host shift, and determine whether clades with frequent host shifts have accelerated rates of evolution or speciation. We will also test the hypothesis that larval type influences rates of (a) molecular evolution, (b) speciation, and (c) gene flow estimated from population genetic data.