Naturally rare versus newly rare: demographic inferences on two timescales inform conservation of Galápagos giant tortoises

• DOI: 10.1002/ece3.1388
• Publication Date: 2015-01-13T07:13:21Z
• Authors: Ryan C. Garrick; Brittney Kajdacsi; Michael A. Russello; Edgar Benavides; Chaz Hyseni; James P. Gibbs; Washington Tapia; Adalgisa Caccone
• Keywords: Population bottleneck; Demographic history; Effective population size; Archipelago; Tortoise; Life History Theory

Abstract Long‐term population history can influence the genetic effects of recent bottlenecks. Therefore, for threatened or endangered species, an understanding past is relevant when formulating conservation strategies. Levels variation at neutral markers have been useful estimating local effective sizes ( N e ) and inferring whether increased decreased over time. Furthermore, analyses genotypic, allelic frequency, phylogenetic information potentially be used to separate historical from demographic changes. For 15 populations Galápagos giant tortoises Chelonoidis sp.), we 12 microsatellite loci DNA sequences mitochondrial control region a nuclear intron, reconstruct on shallow (past ~100 generations, ~2500 years) deep (pre‐Holocene, >10 thousand years ago) timescales. At timescale, three showed strong signals growth, but with different magnitudes timing, indicating underlying causes. estimated across archipelago no correlation island age size, underscoring complexity predicting priori . all carried some signature bottleneck, populations, point estimates contemporary were very small (i.e., < 50). On basis comparison these published census size data, generally represented ~0.16 size. However, variance in this ratio was considerable. Overall, our data suggest that idiosyncratic geographically localized forces shaped tortoise populations. perspective, separation events occurring versus timescales permits identification naturally rare newly populations; distinction should facilitate prioritization management action.