Original Research ARTICLE
Increased adaptive variation despite reduced overall genetic diversity in a rapidly adapting invader
- 1School of Life and Environmental Sciences, University of Sydney, Australia
- 2Evolution & Ecology Research Centre, The University of New South Wales, Australia
- 3Deakin Genomics Centre, School of Life and Environmental Sciences, Deakin University, Australia
- 4Centre for Integrative Ecology, Deakin University, Australia
- 5Evolution & Ecology Research Centre, The University of New South Wales, Australia
Invasive species often evolve rapidly following introduction despite genetic bottlenecks that may result from small numbers of founders; however, some invasions may not fit this “genetic paradox.” The invasive cane toad (Rhinella marina) displays high phenotypic variation across its introduced Australian range. Here, we used three genome-wide datasets to characterize their population structure and genetic diversity. We found that toads form three genetic clusters: (1) native range toads, (2) toads from the source population in Hawai’i and long-established areas near introduction sites in Australia, and (3) toads from more recently established northern Australian sites. Although we find an overall reduction in genetic diversity following introduction, we do not see this reduction in loci putatively under selection, suggesting that genetic diversity may have been maintained at ecologically relevant traits, or that mutation rates were high enough to maintain adaptive potential. Nonetheless, toads encounter novel environmental challenges in Australia, and the transition between genetic clusters occurs at a point along the invasion transect where temperature rises and rainfall decreases. We identify environmentally-associated loci known to be involved in resistance to heat and dehydration. This study highlights that natural selection occurs rapidly and plays a vital role in shaping the structure of invasive populations.
Keywords: Bufo marinus, Rhinella marina, evolution, invasive species, RNA-Seq, genetic paradox of invasions
Received: 09 Apr 2019;
Accepted: 05 Nov 2019.
Copyright: © 2019 Selechnik, Richardson, Shine, DeVore, Ducatez and Rollins. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.
* Correspondence: Mx. Daniel Selechnik, School of Life and Environmental Sciences, University of Sydney, Sydney, Australia, firstname.lastname@example.org