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How important is geographical isolation in speciation?

Date:
May 1, 2010
Source:
Public Library of Science
Summary:
A genetic study of island lizards shows that even those that have been geographically isolated for many millions of years have not evolved into separate species as predicted by conventional evolutionary theory.
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Precursor island regions, lineages, transects, and ecotone on Martinique.
Credit: Thorpe RS, Surget-Groba Y, Johansson H. Genetic Tests for Ecological and Allopatric Speciation in Anoles on an Island Archipelago. PLoS Genetics, 2010; 6(4): e1000929 DOI: 10.1371/journal.pgen.1000929

A genetic study of island lizards shows that even those that have been geographically isolated for many millions of years have not evolved into separate species as predicted by conventional evolutionary theory.

Professor Roger Thorpe and colleagues Yann Surget-Groba and Helena Johansson, at Bangor University, UK, reveal their findings April 29 in the open-access journal PLoS Genetics.

Since Darwin's study of the Galapagos Islands, archipelagos have played a central role in understanding how new species evolve from existing ones (speciation). Islands epitomize allopatric speciation, where geographic isolation causes individuals of an original species to accumulate sufficient genetic differences to prevent them breeding with each other when they are reunited.

Current day Martinique in the Lesser Antilles is composed of several ancient islands that have only recently coalesced into a single entity. The phylogeny and geology show that these ancient islands have had their own tree lizard (anole) species for about six to eight million years.

Capitalizing on the islands' meeting, the authors genetically tested the lizards for reproductive isolation from one another. In using selectively neutral genetic markers, the authors saw that these anoles are freely exchanging genes and therefore not behaving as separate species. Indeed, there is more genetic isolation between conspecifics from different habitats than between those lizards originating from separate ancient islands.

The findings reject allopatric speciation in a case study from a system thought to exemplify it, and suggest the potential importance of speciation due to differences in ecological conditions (ecological speciation). "The next step is to identify the genes controlling the traits influencing the process of speciation," said Roger Thorpe.


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The above post is reprinted from materials provided by Public Library of Science. Note: Materials may be edited for content and length.


Journal Reference:

  1. Thorpe RS, Surget-Groba Y, Johansson H. Genetic Tests for Ecological and Allopatric Speciation in Anoles on an Island Archipelago. PLoS Genetics, 2010; 6(4): e1000929 DOI: 10.1371/journal.pgen.1000929

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Public Library of Science. "How important is geographical isolation in speciation?." ScienceDaily. ScienceDaily, 1 May 2010. <www.sciencedaily.com/releases/2010/04/100429172956.htm>.
Public Library of Science. (2010, May 1). How important is geographical isolation in speciation?. ScienceDaily. Retrieved July 6, 2015 from www.sciencedaily.com/releases/2010/04/100429172956.htm
Public Library of Science. "How important is geographical isolation in speciation?." ScienceDaily. www.sciencedaily.com/releases/2010/04/100429172956.htm (accessed July 6, 2015).

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