Andean and California condors possess dissimilar genetic composition but exhibit similar demographic histories

Abstract

While genetic diversity of threatened species is a major concern of conservation biologists, historic patterns of genetic variation are often unknown. A powerful approach to assess patterns and processes of genetic erosion is via ancient DNA techniques. Herein, we analyzed mtDNA from historical samples (1800s to present) of Andean Condors (Vultur gryphus) to investigate whether contemporary low genetic variability is the result of recent human expansion and persecution, and compared this genetic history to that of California condors (Gymnogyps californianus).We then explored historic demographies for both species via coalescent simulations. We found that Andean condors have lost at least 17% of their genetic variation in the early 20th century. Unlike California condors, however, low mtDNA diversity in the Andean condor was mostly ancient, before European arrival. However, we found that both condor species shared similar demographies in that population bottlenecks were recent and co-occurred with the introduction of livestock to the Americas and the global collapse of marine mammals. Given the combined information on genetic and demographic processes, we suggest that the protection of key habitats should be targeted for conserving extant genetic diversity and facilitate the natural recolonization of lost territories, while nuclear genomic data should be used to inform translocation plans.

Keywords: ancient DNA; bottleneck; genetic diversity; museum; scavenger; vulture.

Figure 1

Continental distribution of historical (1884–1946) and contemporary (1961–2013) mtDNA haplotypes of Vultur gryphus (a). Divisions of putative populations from northern, central, and southern Andes are marked (»; * denote significant geographic differentiation). Temporal network (b) is represented in two chronological time layers linked by haplotype continuity (empty circles symbolize missing haplotypes for that time period while numerals denote sample size). Spatial network (c) depicts the proportion of haplotypes present in each region (roman numbers denote haplogroups). Scatter plot (d) of isolation by distance of 73 individuals sampled across South America

Figure 2

Diagram of four demographic scenarios modeled for California and Andean condors, using Approximate Bayesian Computation. General model parameters: Nef_x denotes the female effective population size and t _x stands for the timing of demographic events

Figure 3

Prior (dash line) and posterior distribution (solid line) of historic effective population size and timing of bottleneck (Anno Domini; assuming a 7‐year generation time) for California condors (a, d) and Andean condors from north (b, e) and central‐south of South America (c, f)