Data from: Structure and evolution of the sea star egg receptor for sperm bindin

Selection on coevolving sperm- and egg-recognition molecules is a potent
engine of population divergence leading to reproductive isolation and
speciation. The study of receptor–ligand pairs can reveal co-evolution of
male- and female-expressed genes or differences between their evolution in
response to selective factors such as sperm competition and sexual
conflict. Phylogeographical studies of these patterns have been limited by
targeted gene methods that favour short protein-coding sequences
amplifiable by PCR. Here, I use high-throughput transcriptomic methods to
characterize the structure and divergence of full-length coding sequences
for the gene encoding the protein component of a large complex egg surface
glycopeptide receptor for the sperm acrosomal protein bindin from the sea
star Patiria miniata. I used a simple but effective method for resolving
nucleotide polymorphisms into haplotypes for phylogeny-based analyses of
selection. The protein domain organization of sea star egg bindin receptor
(EBR1) was similar to sea urchins and included a pair of
protein-recognition domains plus a series of tandem repeat domains of two
types. Two populations separated by a well-characterized phylogeographical
break included lineages of EBR1 alleles under positive selection at
several codons (similar to selection on sperm bindin in the same
populations). However, these populations shared the same alleles that were
under selection for amino acid differences at multiple codons (unlike the
pattern of selection for population divergence in sperm bindin). The
significance of positively selected EBR1 domains and alleles could be
tested in functional analyses of fertilization rates associated with EBR1
(and bindin) polymorphisms.