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.
University of Alaska Museum, 907 Yukon Drive, Fairbanks, AK 99775, USA. millerma@si.edu
Matthew J
MJ
Miller
Eldredge
E
Bermingham
John
J
Klicka
Patricia
P
Escalante
Kevin
K
Winker
D000818:Animals; D001717:Birds / Q000235:genetics*; D051456:Gene Flow; D014644:Genetic Variation; D013045:Species Specificity; D014329:Tropical Climate