Ring distributions leading to species formation: a global topographic analysis of geographic barriers associated with ring species
<p>Abstract</p> <p>Background</p> <p>In the mid 20<sup>th </sup>century, Ernst Mayr and Theodosius Dobzhansky championed the significance of circular overlaps or ring species as the perfect demonstration of speciation, yet in the over 50 years since, only a...
| Main Authors: | , , |
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| Format: | Article |
| Language: | English |
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BMC
2012-03-01
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| Series: | BMC Biology |
| Online Access: | http://www.biomedcentral.com/1741-7007/10/20 |
| _version_ | 1818113551392309248 |
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| author | Monahan William B Pereira Ricardo J Wake David B |
| author_facet | Monahan William B Pereira Ricardo J Wake David B |
| author_sort | Monahan William B |
| collection | DOAJ |
| description | <p>Abstract</p> <p>Background</p> <p>In the mid 20<sup>th </sup>century, Ernst Mayr and Theodosius Dobzhansky championed the significance of circular overlaps or ring species as the perfect demonstration of speciation, yet in the over 50 years since, only a handful of such taxa are known. We developed a topographic model to evaluate whether the geographic barriers that favor processes leading to ring species are common or rare, and to predict where other candidate ring barriers might be found.</p> <p>Results</p> <p>Of the 952,147 geographic barriers identified on the planet, only about 1% are topographically similar to barriers associated with known ring taxa, with most of the likely candidates occurring in under-studied parts of the world (for example, marine environments, tropical latitudes). Predicted barriers separate into two distinct categories: (i) single cohesive barriers (< 50,000 km<sup>2</sup>), associated with taxa that differentiate at smaller spatial scales (salamander: <it>Ensatina eschscholtzii</it>; tree: <it>Acacia karroo</it>); and (ii) composite barriers - formed by groups of barriers (each 184,000 to 1.7 million km<sup>2</sup>) in close geographic proximity (totaling 1.9 to 2.3 million km<sup>2</sup>) - associated with taxa that differentiate at larger spatial scales (birds: <it>Phylloscopus trochiloide</it>s and <it>Larus </it>(sp. <it>argentatus </it>and <it>fuscus</it>)). When evaluated globally, we find a large number of cohesive barriers that are topographically similar to those associated with known ring taxa. Yet, compared to cohesive barriers, an order of magnitude fewer composite barriers are similar to those that favor ring divergence in species with higher dispersal.</p> <p>Conclusions</p> <p>While these findings confirm that the topographic conditions that favor evolutionary processes leading to ring speciation are, in fact, rare, they also suggest that many understudied natural systems could provide valuable demonstrations of continuous divergence towards the formation of new species. Distinct advantages of the model are that it (i) requires no <it>a priori </it>information on the relative importance of features that define barriers, (ii) can be replicated using any kind of continuously distributed environmental variable, and (iii) generates spatially explicit hypotheses of geographic species formation. The methods developed here - combined with study of the geographical ecology and genetics of taxa in their environments - should enable recognition of ring species phenomena throughout the world.</p> |
| first_indexed | 2024-12-11T03:36:38Z |
| format | Article |
| id | doaj.art-597fb8b7a53843f9b377bee80b02b07a |
| institution | Directory Open Access Journal |
| issn | 1741-7007 |
| language | English |
| last_indexed | 2024-12-11T03:36:38Z |
| publishDate | 2012-03-01 |
| publisher | BMC |
| record_format | Article |
| series | BMC Biology |
| spelling | doaj.art-597fb8b7a53843f9b377bee80b02b07a2022-12-22T01:22:13ZengBMCBMC Biology1741-70072012-03-011012010.1186/1741-7007-10-20Ring distributions leading to species formation: a global topographic analysis of geographic barriers associated with ring speciesMonahan William BPereira Ricardo JWake David B<p>Abstract</p> <p>Background</p> <p>In the mid 20<sup>th </sup>century, Ernst Mayr and Theodosius Dobzhansky championed the significance of circular overlaps or ring species as the perfect demonstration of speciation, yet in the over 50 years since, only a handful of such taxa are known. We developed a topographic model to evaluate whether the geographic barriers that favor processes leading to ring species are common or rare, and to predict where other candidate ring barriers might be found.</p> <p>Results</p> <p>Of the 952,147 geographic barriers identified on the planet, only about 1% are topographically similar to barriers associated with known ring taxa, with most of the likely candidates occurring in under-studied parts of the world (for example, marine environments, tropical latitudes). Predicted barriers separate into two distinct categories: (i) single cohesive barriers (< 50,000 km<sup>2</sup>), associated with taxa that differentiate at smaller spatial scales (salamander: <it>Ensatina eschscholtzii</it>; tree: <it>Acacia karroo</it>); and (ii) composite barriers - formed by groups of barriers (each 184,000 to 1.7 million km<sup>2</sup>) in close geographic proximity (totaling 1.9 to 2.3 million km<sup>2</sup>) - associated with taxa that differentiate at larger spatial scales (birds: <it>Phylloscopus trochiloide</it>s and <it>Larus </it>(sp. <it>argentatus </it>and <it>fuscus</it>)). When evaluated globally, we find a large number of cohesive barriers that are topographically similar to those associated with known ring taxa. Yet, compared to cohesive barriers, an order of magnitude fewer composite barriers are similar to those that favor ring divergence in species with higher dispersal.</p> <p>Conclusions</p> <p>While these findings confirm that the topographic conditions that favor evolutionary processes leading to ring speciation are, in fact, rare, they also suggest that many understudied natural systems could provide valuable demonstrations of continuous divergence towards the formation of new species. Distinct advantages of the model are that it (i) requires no <it>a priori </it>information on the relative importance of features that define barriers, (ii) can be replicated using any kind of continuously distributed environmental variable, and (iii) generates spatially explicit hypotheses of geographic species formation. The methods developed here - combined with study of the geographical ecology and genetics of taxa in their environments - should enable recognition of ring species phenomena throughout the world.</p>http://www.biomedcentral.com/1741-7007/10/20 |
| spellingShingle | Monahan William B Pereira Ricardo J Wake David B Ring distributions leading to species formation: a global topographic analysis of geographic barriers associated with ring species BMC Biology |
| title | Ring distributions leading to species formation: a global topographic analysis of geographic barriers associated with ring species |
| title_full | Ring distributions leading to species formation: a global topographic analysis of geographic barriers associated with ring species |
| title_fullStr | Ring distributions leading to species formation: a global topographic analysis of geographic barriers associated with ring species |
| title_full_unstemmed | Ring distributions leading to species formation: a global topographic analysis of geographic barriers associated with ring species |
| title_short | Ring distributions leading to species formation: a global topographic analysis of geographic barriers associated with ring species |
| title_sort | ring distributions leading to species formation a global topographic analysis of geographic barriers associated with ring species |
| url | http://www.biomedcentral.com/1741-7007/10/20 |
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