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SQUAMATE REPTILES AS MODEL ORGANISMS FOR THE EVOLUTION OF VIVIPARITY

SQUAMATE REPTILES AS MODEL ORGANISMS FOR THE EVOLUTION OF VIVIPARITY For over a century, research has been conducted on squamates in order to reveal how viviparity has evolved in mammals and other vertebrates. The recent proliferation of studies has yielded much information on anatomical, physiological, ecological, and evolutionary aspects, allowing a reassessment of squamates as model organisms for the study of viviparity. Strong support for the “squamate model” comes from phylogenetic analyses that have shown that squamates have evolved viviparity with great frequency (> 108 origins), at low taxonomic levels, and in geologically recent times. However, available data also indicate that viviparity has evolved by different chronologies and mechanisms in squamates, fishes, and mammals. Further, generalizations about squamates are difficult to make, given the diverse mechanisms by which they achieve viviparity. Thus, similarities between squamates must be demonstrated empirically, and generalizations should be based on quantitative, phylogenetic analyses of multiple lineages. Explanations for similarities between squamate clades can invoke such concepts as evolutionary constraints, exaptations, and selection pressures, and should distinguish between adaptations, correlated attributes, and features that predate viviparity. However, homocentric assumptions of an orthogenetic transformation towards the eutherian condition should be abandoned, along with untested assumptions that viviparity squamates and mammals is similar. The value of the squamate model ultimately may lie in insights it provides into physiological problems rather than in universality of specific mechanisms that have evolved to meet those problems. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Herpetological Monographs Allen Press

SQUAMATE REPTILES AS MODEL ORGANISMS FOR THE EVOLUTION OF VIVIPARITY

Herpetological Monographs , Volume 20 (1) – Dec 29, 2006

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Publisher
Allen Press
Copyright
The Herpetologists' League, Inc.
Subject
EVOLUTION OF VIVIPARITY IN REPTILES
ISSN
0733-1347
eISSN
1938-5137
DOI
10.1655/0733-1347%282007%2920%5B131:SRAMOF%5D2.0.CO%3B2
Publisher site
See Article on Publisher Site

Abstract

For over a century, research has been conducted on squamates in order to reveal how viviparity has evolved in mammals and other vertebrates. The recent proliferation of studies has yielded much information on anatomical, physiological, ecological, and evolutionary aspects, allowing a reassessment of squamates as model organisms for the study of viviparity. Strong support for the “squamate model” comes from phylogenetic analyses that have shown that squamates have evolved viviparity with great frequency (> 108 origins), at low taxonomic levels, and in geologically recent times. However, available data also indicate that viviparity has evolved by different chronologies and mechanisms in squamates, fishes, and mammals. Further, generalizations about squamates are difficult to make, given the diverse mechanisms by which they achieve viviparity. Thus, similarities between squamates must be demonstrated empirically, and generalizations should be based on quantitative, phylogenetic analyses of multiple lineages. Explanations for similarities between squamate clades can invoke such concepts as evolutionary constraints, exaptations, and selection pressures, and should distinguish between adaptations, correlated attributes, and features that predate viviparity. However, homocentric assumptions of an orthogenetic transformation towards the eutherian condition should be abandoned, along with untested assumptions that viviparity squamates and mammals is similar. The value of the squamate model ultimately may lie in insights it provides into physiological problems rather than in universality of specific mechanisms that have evolved to meet those problems.

Journal

Herpetological MonographsAllen Press

Published: Dec 29, 2006

Keywords: Animal models ; Evolution ; Mammals ; Placentation ; Reproduction ; Squamates ; Viviparity

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