PARENT SESSION
Contributed Oral Session 99: Populations and Genetics: Diversity and Population Dynamics
Wednesday, August 10, 1:30 PM - 5:00 PM, Meeting Room 519 A, Level 5, Palais des congrès de Montréal

Cryptic speciation in the cosmopolitan Epiphanes senta complex (Monogononta, Rotifera) I: Diapause, mating behavior and reproductive isolation among species from temporary and permanent habitats.

Schroeder, Thomas ^{*,1, 2}, Walsh, Elizabeth¹, ¹ University of Texas at El Paso, El Paso, TX, USA² Academy of Natural Sciences of Philadelphia, Philadelphia, PA, USA

ABSTRACT- Many species of the phylum Rotifera are considered to be cosmopolitan euryecious species with a worldwide distribution. Epiphanes senta has been found on all continents except Africa and Antarctica in eutrophic ponds, lakes, floodplains and rivers, and temporary desert pools. We studied populations in a permanent tropical alpine lake on Hawaii, in temporary rock pools of the Chihuahuan Desert (North America) and in temporary floodplain habitats of the Oder River (Europe). Populations differ in diapause induction and in their mating behavior. Sexual reproduction which leads to diapause is induced through high population density in the floodplain and the Chihuahuan Desert populations, but not in the Hawaiian population. Males of the European and the Chihuahuan Desert populations display mate guarding behavior, attending the female eggs and mating with the hatching female. In mate choice experiments males of the floodplain population were able to distinguish between female eggs from their own and from other populations, attending almost exclusively those from their own population (99.9% of the mate guarding behavior displayed in 20 tests was directed towards eggs of their own population). Males of the Chihuahuan Desert population did not differentiate between eggs from different populations. They spent 53% of the time attending eggs from their own population and 47% of the time attending eggs from the other population. In cross mating experiments Chihuahuan Desert males mated with hatching females from the floodplain population. However, juvenile mortality among these fertilized females reached 41% and was significantly higher than juvenile mortality after intrapopulational mating (2%). Surviving females did not produce viable diapausing eggs. Hawaiian males, although not attending eggs, readily mated with newborn females from the Chihuahuan Desert which then produced viable offspring. Partial reproductive isolation among the studied populations demonstrates that the cosmopolitan Epiphanes senta is actually a species complex. Yet ecological and behavioral differences do not correlate with reproductive isolation as in these respects the floodplain and Chihuahuan Desert population are much more similar to each other.

Key words: cryptic speciation, rotifers, mating behavior, diapause