Endangered Populations Growing in Size But Still at Risk
The Little Spotted Kiwi (Apteryx owenii) is a near threatened bird species that once inhabited forests throughout New Zealand, but is now constricted to near shore islands devoid of introduced predators. Each of the eight islands the birds now inhabit was founded by a different number of individuals. This paper investigates the genetic diversity and fledgling survival between a site founded by two individuals (Long Island) and a site founded by 40 individuals (Zealandia Sanctuary). Populations on both islands are growing indicating a conservation success! However, the population founded by two individuals lost 25% of the genetic diversity of the source population that founded it by the 2nd generation (with increasing losses expected into the future), where no alleles were lost from the larger founding population. Further, the Long Island population put more effort into reproduction yet had fewer eggs hatch, and had more late-stage embryonic failure (with malformations) than the Zealandia population. Taken together this study cautions that number of individuals alone cannot be a sole metric of managed reintroduction success for threatened species. It also shows the value of genetic monitoring of populations and how that data can inform future conservation decision making.
Side photo of a little spotted kiwi by Geoff Moon via ARKive.
Black Rhino Genetic Diversity
I have no pithy titles for this paper, it’s just so sad. The authors used contemporary and museum samples to calculate changes in genetic diversity over time throughout the range of the black rhinoceros (Diceros bicornis), a critically endangered species. While sample sizes are limited for both temporal datasets, the authors show the extent of genetic diversity loss in all four subspecies of black rhinos. Specifically, many populations throughout the range were stable or increasing until ~150 years ago when populations began to steadily decline, due to overhunting. The authors note that many populations have been extirpated along with unique mitochondrial haplotypes and nuclear alleles not found in the few remaining populations. Further, the remaining populations have themselves had genetic diversity losses, thereby limiting the ability of each population to respond to changing environments.