Neotropical birds show a humped distribution of within-population genetic diversity along a latitudinal transect.
The latitudinal gradient in species richness is a nearly universal ecological phenomenon. Similarly, conspecific genetic diversity often increases towards the equator - usually explained as the consequence of post-glacial range expansion or due to the shared response of genetic diversity to processes that promote species richness. However, no study has yet examined the relationship between latitude and within-population genetic diversity in exclusively tropical species. We surveyed genetic variation in nine resident bird species co-occurring in tropical lowlands between southern Mexico and western Ecuador, where avian species richness increases with decreasing latitude. Within-population genetic variation was always highest at mid-range latitudes, and not in the most equatorial populations. Differences in demography and gene flow across species' ranges may explain some of our observations; however, much of the pattern may be due simply to geometric constraints. Our findings have implications for conservation planning and for understanding how biodiversity scales from genes to communities.
Miller
Matthew J
MJ
University of Alaska Museum, 907 Yukon Drive, Fairbanks, AK 99775, USA. millerma@si.edu
Bermingham
Eldredge
E
Klicka
John
J
Escalante
Patricia
P
Winker
Kevin
K
D000818:Animals; D001717:Birds / Q000235:genetics*; D051456:Gene Flow; D014644:Genetic Variation; D013045:Species Specificity; D014329:Tropical Climate