HART, M. W.*; PODOLSKY, R. D.; Dalhousie Univ.; Univ. of North Carolina, Chapel Hill: Phylogeny and life history evolution of Macrophiothrix brittlestars

Macrophiothrix are a species-rich group of geographically widespread tropical brittlestars. Eighteen taxonomically well-characterized species are known from Australia. We inferred phylogenetic relationships among 12 Australian Macrophiothrix species using mitochondrial DNA sequences. Duplicate haplotypes from six species always formed monophyletic groups (though in some cases with large genetic distances between conspecific haplotypes). Preliminary analysis of the mtDNA data suggested the following rooted phylogeny: (((((caenosa, longipeda (leucosticha, megapoma)) koehleri) ((belli, demessa) nereidina)) (lorioli (rhabdota, paucispina))) propinqua), but with weak support for some nodes. Macrophiothrix caenosa was only recently distinguished from M. longipeda, but the two species are not strongly identified as sister taxa. Macrophiothrix belli and M. demessa appear to be sister taxa, though they have the largest and smallest eggs of the Macrophiothrix species included in our study. We discuss the congruence between the mtDNA characters and the morphological and allozyme characters previously analyzed by A.K. Hoggett. We also discuss some preliminary inferences on life history evolution from the best supported phylogeny.