Peart CR, Tusso S, Pophaly SD, Botero-Castro F, Wu CC, Aurioles-Gamboa D, Baird AB, Bickham JW, Forcada J, Galimberti F, Gemmell NJ, Hoffman JI, Kovacs KM, Kunnasranta M, Lydersen C, Nyman T, de Oliveira LR, Orr AJ, Sanvito S, Valtonen M, Shafer ABA, Wolf JBW
Nat Ecol Evol 4 (8) 1095-1104 [2020-08-00; online 2020-06-08]
The effective size of a population (Ne), which determines its level of neutral variability, is a key evolutionary parameter. Ne can substantially depart from census sizes of present-day breeding populations (NC) as a result of past demographic changes, variation in life-history traits and selection at linked sites. Using genome-wide data we estimated the long-term coalescent Ne for 17 pinniped species represented by 36 population samples (total n = 458 individuals). Ne estimates ranged from 8,936 to 91,178, were highly consistent within (sub)species and showed a strong positive correlation with NC ([Formula: see text] = 0.59; P = 0.0002). Ne/NC ratios were low (mean, 0.31; median, 0.13) and co-varied strongly with demographic history and, to a lesser degree, with species' ecological and life-history variables such as breeding habitat. Residual variation in Ne/NC, after controlling for past demographic fluctuations, contained information about recent population size changes during the Anthropocene. Specifically, species of conservation concern typically had positive residuals indicative of a smaller contemporary NC than would be expected from their long-term Ne. This study highlights the value of comparative population genomic analyses for gauging the evolutionary processes governing genetic variation in natural populations, and provides a framework for identifying populations deserving closer conservation attention.