Shrinking before our isles: the rapid expression of insular dwarfism in two invasive populations of guttural toad (Sclerophrys gutturalis)

James Baxter-Gilbert*, Julia L. Riley, Carla Wagener, Nitya P. Mohanty, John Measey

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

Abstract

Island ecosystems have traditionally been hailed as natural laboratories for examining phenotypic change, including dramatic shifts in body size. Similarly, biological invasions can drive rapid localized adaptations within modern timeframes. Here, we compare the morphology of two invasive guttural toad (Sclerophrys gutturalis) populations in Mauritius and Réunion with their source population from South Africa. We found that female toads on both islands were significantly smaller than mainland counterparts (33.9% and 25.9% reduction, respectively), as were males in Mauritius (22.4%). We also discovered a significant reduction in the relative hindlimb length of both sexes, on both islands, compared with mainland toads (ranging from 3.4 to 9.0%). If our findings are a result of natural selection, then this would suggest that the dramatic reshaping of an amphibian's morphology-leading to insular dwarfism-can result in less than 100 years; however, further research is required to elucidate the mechanism driving this change (e.g. heritable adaptation, phenotypic plasticity, or an interaction between them).

Original languageEnglish
Article number20200651
Number of pages6
JournalBiology Letters
Volume16
Issue number11
DOIs
Publication statusPublished - Nov 2020
Externally publishedYes

Keywords

  • amphibian
  • body size
  • invasive species
  • island biology
  • morphology

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