Does population size affect genetic diversity? A test with sympatric lizard species

Abstract

Genetic diversity is a fundamental requirement for evolution and adaptation. Nonetheless, the forces that maintain patterns of genetic variation in wild populations are not completely understood. Neutral theory posits that genetic diversity will increase with a larger effective population size and the decreasing effects of drift. However, the lack of compelling evidence for a relationship between genetic diversity and population size in comparative studies has generated some skepticism over the degree that neutral sequence evolution drives overall patterns of diversity. The goal of this study was to measure genetic diversity among sympatric populations of related lizard species that differ in population size and other ecological factors. By sampling related species from a single geographic location, we aimed to reduce nuisance variance in genetic diversity owing to species differences, for example, in mutation rates or historical biogeography. We compared populations of zebra-tailed lizards and western banded geckos, which are abundant and short-lived, to chuckwallas and desert iguanas, which are less common and long-lived. We assessed population genetic diversity at three protein-coding loci for each species. Our results were consistent with the predictions of neutral theory, as the abundant species almost always had higher levels of haplotype diversity than the less common species. Higher population genetic diversity in the abundant species is likely due to a combination of demographic factors, including larger local population sizes (and presumably effective population sizes), faster generation times and high rates of gene flow with other populations.

Chronic radiation exposure at Chernobyl shows no effect on genetic diversity in the freshwater crustacean, Asellus aquaticus thirty years on

“…Under neutral theory, a given population's genetic diversity is dependent on both the effective population size and the mutation rate (Kimura, ). Larger effective populations typically show greater genetic diversity than smaller populations (Hague & Routman, ), though some comparative studies have questioned this relationship (Bazin, Glémin, & Galtier, ). The conclusions of the present study are therefore based on the assumption of similar effective population sizes at these locations.…”

Is genomic diversity a useful proxy for census population size? Evidence from a species‐rich community of desert lizards

“…Previous studies have found positive relationships between heterozygosity and proxies for species abundance, including population size estimated from calculations of density and acreage (Patton & Yang, ), extrapolations calculated from active social groups (Stangel, Lennartz, & Smith, ), categorical estimates (“large,” “small”) of population size (Godt, Johnson, & Hamrick, ; Hague & Routman, ) and museum occurrence records (Singhal, Huang, et al, ). Studies that more directly compare intraspecific genetic diversity and abundance have reported positive associations, but these studies have generally focused on single species or paired species comparisons (Devillard, Santin‐Janin, Say, & Pontier, ; Lozier, ; Ortego, Aparicio, Cordero, & Calabuig, ; Sun, ), or on many species sampled at a broad geographical scale (Bazin, Glémin, & Galtier, ; Leimu, Mutikainen, Koricheva, & Fischer, ; McCusker & Bentzen, ; Pinsky & Palumbi, ).…”

“…"small") of population size (Godt, Johnson, & Hamrick, 1996;Hague & Routman, 2016) and museum occurrence records (Singhal, Huang, et al, 2017). Studies that more directly compare intraspecific genetic diversity and abundance have reported positive associations, but these studies have generally focused on single species or paired species comparisons (Devillard, Santin-Janin, Say, & Pontier, 2011;Lozier, 2014;Ortego, Aparicio, Cordero, & Calabuig, 2008;Sun, 1996), or on many species sampled at a broad geographical scale (Bazin, Glémin, & Galtier, 2006;Leimu, Mutikainen, Koricheva, & Fischer, 2006;McCusker & Bentzen, 2010;Pinsky & Palumbi, 2014).…”

Quantifying the individual impact of artificial barriers in freshwaters: A standardized and absolute genetic index of fragmentation

“…He was then averaged over 195 the two populations and further considered as a proxy for effective population sizes. Both theoretical 196 and empirical works indeed indicate that genetic diversity should increase with the increase in 197 effective population sizes(Hague & Routman, 2016;Kimura, 1983; see also Appendix S4). We here 198 focused on mean heterozygosity because, unlike metrics such as allelic richness, heterozygosity values 199 are bounded between 0 and 1, which facilitates comparison between case studies.…”