Meeting Abstract

55.5  Thursday, Jan. 6  Recently established populations of Botryllus schlosseri (Ascidiacea) show high diversity at the fusion/histocompatibility locus WANG, V.H.*; COHEN, C.S.; Romberg Tiburon Center for Environmental Studies, Department of Biology, San Francisco State University vhwang@rtc.sfsu.edu

Studies of invasive populations are most often conducted with neutral loci, which may not have enough variation to examine new populations. Here, we study the globally invasive colonial ascidian Botryllus schlosseri, and compare variation at a fragment of the functional nuclear fusion/histocompatibility (FuHC) locus to mitochondrial COI, which has been used in previous studies of B. schlosseri populations, and is common for invasion genetics across many taxa. We compare populations in Sitka, Alaska, where B. schlosseri was first reported in 2001, to those in San Francisco Bay, California, where B. schlosseri has been present since the 1940s, to see how diversity differs with time since establishment. By direct genotyping of FuHC, we also hope to elucidate what role colony fusions may play in the establishment of invasive B. schlosseri populations. We expect higher genetic resolution with FuHC than with COI, but still anticipate lower diversity in Alaska. We found very low COI diversity in both regions, although diversity was slightly higher in SF Bay (AK: Nh = 2, Hd = 0.4637, π = 0.0068; SF: Nh = 4, Hd = 0.6600, π = 0.0155). FuHC diversity was much higher (AK: Nh = 11, Hd = 0.8295, π = 0.0538; SF: Nh = 10, Hd = 0.8506, π = 0.0260), and FuHC nucleotide diversity was elevated in Alaskan populations. We found no evidence of a bottleneck in Alaska. FuHC data has shown that Alaskan populations are equally or more diverse when compared to the older SF Bay populations, and indicate the possibility of multiple sources for the invasion into Alaska. This was not detected in COI, but whether this is due to increased variation or selective pressures on FuHC remains unknown.