Meeting Abstract

16.2  Saturday, Jan. 4 10:30  Genetic diversification in Rotifera: Successful Dispersal and Colonization or Local Adaptation WALSH, E.J.*; REYES, D.E.; HAMDAN, L.; RAMOS CHAVEZ, J.; KORDBACHEH, A.; Univ. of Texas at El Paso ewalsh@utep.edu

Advances in molecular systematics have uncovered cryptic species in a wide variety of aquatic microinvertebrates. Here we examine genetic diversification of four cosmopolitan rotifers (Epiphanes senta complex, Philodina megalotrocha, Euchlanis dilatata, Lecane bulla) using COI mtDNA sequences. We found high levels of sequence divergence (≤24%) in all taxa. These levels are comparable to those typically found in morphological species and exceed the 4X rule used to delineate species based on sequence data. We also found evidence of widespread haplotypes: Phylogenetic analyses based on Bayesian inference distinguish a monophyletic clade of E. chihuahuaensis with sequence divergence of 0-1.6% among populations at one site. While at the other site, no E. chihuahuaensis isolates were found but individuals representing two other members of the E. senta complex were detected. Several isolates showed no sequence divergence from E. hawaiiensis. E. chihuahuaensis may be a rock pool specialist, adapted to these ephemeral habitats while E. hawaiiensis may be widely dispersed among more permanent habitats. Similarly, phylogenetic and Isolation by Distance analyses of the other taxa showed three distinct patterns: isolates with low geographic and genetic distances, isolates with high degrees of genetic divergence at nearby sites, along with a large group of widely dispersed isolates with low genetic distances. Our results indicate that a complex pattern of dispersal, colonization, and local adaptation contribute to the biogeography of these microinvertebrates.