Population genomics of the endangered Chinese crocodile lizard
Hongxin Xie, PhD candidate in Prof. Weiguo Du’s lab (Group of Ecological Adaptation and Conservation Biology) at Institute of Zoology, Chinese Academy of Sciences. His research focuses on using genomic tools to study the evolution, conservation, and ecological adaptation of squamate reptiles.
Genomic data helps to resolve the population history of Chinese crocodile lizards and provides insights into how genetic purging works in small wild populations.
The purging of deleterious alleles has been hypothesized to mitigate inbreeding depression, but its effectiveness in endangered species remains debatable. To understand how deleterious alleles are purged during population contractions, we analyzed genomes of the endangered Chinese crocodile lizard (Shinisaurus crocodilurus), which is the only surviving species of its family and currently isolated into small populations. Population genomic analyses revealed four genetically distinct conservation units and sharp declines in both effective population size and genetic diversity. By comparing the relative genetic load across populations and conducting genomic simulations, we discovered that seriously deleterious alleles were effectively purged during population contractions in this relict species, although inbreeding generally enhanced the genetic burden. However, despite with the initial purging, our simulations also predicted that seriously deleterious alleles will gradually accumulate under prolonged bottlenecking. Therefore, we emphasize the importance of maintaining a minimum population capacity and increasing the functional genetic diversity in conservation efforts to preserve populations of the crocodile lizard and other endangered species.