Naturally rare versus newly rare: demographic inferences on two timescales inform conservation of Galápagos giant tortoises
Ryan C. Garrick, Brittney Kajdacsi, Michael A. Russello, Edgar Benavides, Chaz Hyseni, James P. Gibbs, Washington Tapia and Adalgisa Caccone
Article first published online: 13 JAN 2015 | DOI: 10.1002/ece3.1388
From a conservation perspective, there is considerable value in making a distinction between a recently bottlenecked population that was previously large and stable, versus one that has always been small or had a long history of repeated size reductions. We develop and apply an analytical framework for reconstructing demographic history of Galápagos giant tortoises on two timescales. For 15 populations of Galápagos giant tortoises (Chelonoidis sp.) we used 12 microsatellite loci, and DNA sequences from the mitochondrial control region and a nuclear intron, to reconstruct demographic history on shallow (past ~100 generations, ~2500 years) and deep (pre-Holocene, >10 thousand years ago) timescales. Overall, our data suggest that idiosyncratic and geographically localized forces shaped the demographic history of tortoise populations, and permitted the identification of naturally rare vs. newly rare populations. This should facilitate prioritization of management action.