Reproductive protein evolution within and between species: maintenance of divergent ZP3 alleles in Peromyscus.
In a variety of animal taxa, proteins involved in reproduction evolve more rapidly than nonreproductive proteins. Most studies of reproductive protein evolution, however, focus on divergence between species, and little is known about differentiation among populations within a species. Here we investigate the molecular population genetics of the protein ZP3 within two Peromyscus species. ZP3 is an egg coat protein involved in primary binding of egg and sperm and is essential for fertilization. We find that amino acid polymorphism in the sperm-combining region of ZP3 is high relative to silent polymorphism in both species of Peromyscus. In addition, while there is geographical structure at a mitochondrial gene (Cytb), a nuclear gene (Lcat) and eight microsatellite loci, we find no evidence for geographical structure at Zp3 in Peromyscus truei. These patterns are consistent with the maintenance of ZP3 alleles by balancing selection, possibly due to sexual conflict or pathogen resistance. However, we do not find evidence that reinforcement promotes ZP3 diversification; allelic variation in P. truei is similar among populations, including populations allopatric and sympatric with sibling species. In fact, most alleles are present in all populations sampled across P. truei's range. While additional data are needed to identify the precise evolutionary forces responsible for sequence variation in ZP3, our results suggest that in Peromyscus, selection to maintain divergent alleles within species contributes to the pattern of rapid amino acid substitution observed among species.
Turner
Leslie M
LM
Division of Biological Sciences, University of California at San Diego, La Jolla, CA 92093, USA. turner@evolbio.mpg.de
Hoekstra
Hopi E
HE
D000483:Alleles; D000818:Animals; D004272:DNA, Mitochondrial / Q000235:genetics; D004527:Egg Proteins / Q000235:genetics*; D019143:Evolution, Molecular; D014644:Genetic Variation; D005838:Genotype; D008562:Membrane Glycoproteins / Q000235:genetics*; D008800:Mexico; D018895:Microsatellite Repeats / Q000235:genetics; D008969:Molecular Sequence Data; D010542:Peromyscus / Q000235:genetics*; D011956:Receptors, Cell Surface / Q000235:genetics*; D012098:Reproduction / Q000235:genetics*; D017422:Sequence Analysis, DNA; D014481:United States; D000072216:Zona Pellucida Glycoproteins
D004272:DNA, Mitochondrial; D004527:Egg Proteins; D008562:Membrane Glycoproteins; D011956:Receptors, Cell Surface; D000072216:Zona Pellucida Glycoproteins