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PATTERNS OF NUCLEOTIDE DIVERSITY IN TWO SPECIES OF MIMULUS ARE AFFECTED BY MATING SYSTEM AND ASYMMETRIC INTROGRESSION
Author(s) -
Sweigart Andrea L.,
Willis John H.
Publication year - 2003
Publication title -
evolution
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.84
H-Index - 199
eISSN - 1558-5646
pISSN - 0014-3820
DOI - 10.1111/j.0014-3820.2003.tb01494.x
Subject(s) - biology , introgression , selfing , outcrossing , reproductive isolation , genetic diversity , evolutionary biology , nucleotide diversity , genetic variation , ecology , genetics , population , haplotype , allele , gene , pollen , demography , sociology
The evolutionary transition from outcrossing to self‐fertilization has far‐reaching implications for patterns of intraspecific genetic diversity and the potential for speciation. Using DNA sequence variation at two nuclear loci, we examined the divergence history of two closely related species ofMimulus. To investigate the effects of mating system and introgressive hybridization on the outcrossing M. guttatus and the selfing M. nasutus, we inspected nucleotide diversity within and between natural populations spanning the species—geographic ranges. High sequence similarity among populations of the selfing M. nasutus points to a single evolutionary origin for the species. Consistent with their distinct mating systems, all genetic variation in M. nasutus is distributed among populations, whereas M. guttatus exhibits appreciable levels of nucleotide diversity within populations. Silent genetic diversity is extensive in M. guttatus (mean θ sil /site = 0.077) and greatly exceeds the predicted twofold elevation in neutral variation for outcrossers relative to selfers. The finding of several M. guttatus sequences that share complete identity with sequences from M. nasutus suggests that recent asymmetric introgression may have occurred. We argue that exceptionally high nucleotide diversity in M. guttatus is consistent with a long‐term history of directional introgression from M. nasutus to M. guttatus throughout the divergence of these two species.