Divergent Gene Copies in the Asexual Class Bdelloidea (Rotifera) Separated Before the Bdelloid Radiation or Within Bdelloid Families

TitleDivergent Gene Copies in the Asexual Class Bdelloidea (Rotifera) Separated Before the Bdelloid Radiation or Within Bdelloid Families
Publication TypeJournal Articles
Year of Publication2004
AuthorsWelch DBMark, Cummings MP, Hillis DM, Meselson M
JournalProceedings of the National Academy of Sciences of the United States of AmericaPNASProceedings of the National Academy of Sciences of the United States of AmericaPNAS
Volume101
Type of Article10.1073/pnas.2136686100
ISBN Number0027-8424, 1091-6490
Abstract

Rotifers of the asexual class Bdelloidea are unusual in possessing two or more divergent copies of every gene that has been examined. Phylogenetic analysis of the heat-shock gene hsp82 and the TATA-box-binding protein gene tbp in multiple bdelloid species suggested that for each gene, each copy belonged to one of two lineages that began to diverge before the bdelloid radiation. Such gene trees are consistent with the two lineages having descended from former alleles that began to diverge after meiotic segregation ceased or from subgenomes of an alloploid ancestor of the bdelloids. However, the original analyses of bdelloid gene-copy divergence used only a single outgroup species and were based on parsimony and neighbor joining. We have now used maximum likelihood and Bayesian inference methods and, for hsp82, multiple outgroups in an attempt to produce more robust gene trees. Here we report that the available data do not unambiguously discriminate between gene trees that root the origin of hsp82 and tbp copy divergence before the bdelloid radiation and those which indicate that the gene copies began to diverge within bdelloid families. The remarkable presence of multiple diverged gene copies in individual genomes is nevertheless consistent with the loss of sex in an ancient ancestor of bdelloids.