Geographic Variation, Speciation and Clines

by John A. Endler

Overview

Geographic Variation, Speciation and Clines explores the origins and development of geographic variation, divergence, and speciation. In particular it is concerned with genetic divergence as it is usually found on continents, among groups of populations isolated only by distance. Although earlier writers on this topic considered the effects of geography and dispersal, intense geographic differentiation and speciation were thought to require complete isolation. Professor Endler shows how geographic differentiation and speciation may develop in spite of continuous gene flow.


Following a review of the diverse and scattered literature on gene flow and population differentiation, the author discusses the relationships among gene flow, dispersal, and migration. He then summarizes the factors which limit the geographic extent of gene flow, and those which allow steep clines to develop in the absence of barriers to gene flow. His analysis draws on examples from the field, experiments, and single- and multiple-locus models.


The mechanism and conditions for parapatric speciation are presented: steepening clines, development into hybrid zones, and the evolution of sexual isolation. In the final chapter the author considers the interpretation of natural clines and the associated geographic patterns of subspecies and species.

Product Details

ISBN-13:	9780691081922
Publisher:	Princeton University Press
Publication date:	09/21/1977
Series:	Monographs in Population Biology , #10
Pages:	262
Product dimensions:	5.50(w) x 8.50(h) x (d)

Table of Contents

	Preface	vii
1.	Introduction	3
2.	On gene flow	20
3.	Properties of clines	30
3.1.	Measurement of differentiation	30
3.2.	Genetic sampling drift	33
3.3.	Environmental gradients	53
3.4.	Spatially abrupt environmental changes	80
3.5.	The gradient and stepped environment models	88
3.6.	Secondary contact	89
3.7.	Summary	93
4.	Experimental clines and the effects of interaction among different loci	97
4.1.	Introduction	97
4.2.	Models of coadaptation	98
4.3.	A Drosophila experiment	108
4.4.	The effect of linkage	136
4.5.	Summary	139
5.	Parapatric speciation	142
6.	Secondary or primary intergradation?	152
	Glossary	179
	Literature Cited	185
	Subject Index	241
	Author Index	244