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EVOLUTION OF THE MATING SEASON IN THE PITVIPERS OF NORTH AMERICA

EVOLUTION OF THE MATING SEASON IN THE PITVIPERS OF NORTH AMERICA In the majority of temperate zone snakes, the mating season is temporally dissociated from the time of fertilization. Similarly, in males, the mating season is often temporally dissociated from spermatogenesis. In temperate zone pitvipers of North America, estrus, the time when females signal that they are receptive to males, occurs at some time during vitellogenesis. In these pitvipers, vitellogenesis is initiated in the late summer or fall. The vitellogenic follicles overwinter at an intermediate size, resume development in the spring, and culminate with ovulation in the spring. The seasonal patterns of estrus (late summer/fall or spring or both seasons) vary among species and rarely among populations within a species. In our model, we assume (i) that females determine the mating season, (ii) that there are significant costs to females during estrus, and (iii) that males adapt their mating season to the combined time when females enter estrus. We propose that the vitellogenic cycle of temperate zone pitvipers is simply a modification of the vitellogenic cycle seen in tropical pitvipers. The major difference being the interruption of vitellogenesis in temperate species by cold temperatures. In tropical pitvipers the vitellogenic cycle is continuous (no winter pause) and the mating season occurs at some time during vitellogenesis. As populations of pitvipers evolved into temperate climates, due to range expansion into temperate regions or climate change in existing ranges, the seasonal vitellogenic cycle was interrupted by winter. Since the mating season occurs during vitellogenesis, having a summer/fall and spring mating season is consistent with the tropical pattern. The different mating patterns we see today reflect a loss of either the summer/fall or the spring mating season. The reason for the loss may be due to the success of one mating season (all the females being fertilized) and the costs associated with having a redundant mating season. Since males also have significant costs associated with being prepared to mate, the loss of the female mating season would result in a corresponding loss of that season in males. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Herpetological Monographs Allen Press

EVOLUTION OF THE MATING SEASON IN THE PITVIPERS OF NORTH AMERICA

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Publisher
Allen Press
Copyright
The Herpetologists' League
Subject
CONTENTS
ISSN
0733-1347
eISSN
1938-5137
DOI
10.1655/0733-1347%282002%29016%5B0001:EOTMSI%5D2.0.CO%3B2
Publisher site
See Article on Publisher Site

Abstract

In the majority of temperate zone snakes, the mating season is temporally dissociated from the time of fertilization. Similarly, in males, the mating season is often temporally dissociated from spermatogenesis. In temperate zone pitvipers of North America, estrus, the time when females signal that they are receptive to males, occurs at some time during vitellogenesis. In these pitvipers, vitellogenesis is initiated in the late summer or fall. The vitellogenic follicles overwinter at an intermediate size, resume development in the spring, and culminate with ovulation in the spring. The seasonal patterns of estrus (late summer/fall or spring or both seasons) vary among species and rarely among populations within a species. In our model, we assume (i) that females determine the mating season, (ii) that there are significant costs to females during estrus, and (iii) that males adapt their mating season to the combined time when females enter estrus. We propose that the vitellogenic cycle of temperate zone pitvipers is simply a modification of the vitellogenic cycle seen in tropical pitvipers. The major difference being the interruption of vitellogenesis in temperate species by cold temperatures. In tropical pitvipers the vitellogenic cycle is continuous (no winter pause) and the mating season occurs at some time during vitellogenesis. As populations of pitvipers evolved into temperate climates, due to range expansion into temperate regions or climate change in existing ranges, the seasonal vitellogenic cycle was interrupted by winter. Since the mating season occurs during vitellogenesis, having a summer/fall and spring mating season is consistent with the tropical pattern. The different mating patterns we see today reflect a loss of either the summer/fall or the spring mating season. The reason for the loss may be due to the success of one mating season (all the females being fertilized) and the costs associated with having a redundant mating season. Since males also have significant costs associated with being prepared to mate, the loss of the female mating season would result in a corresponding loss of that season in males.

Journal

Herpetological Monographs – Allen Press

Published: Aug 1, 2002

Keywords: Agkistrodon ; Crotalus ; Sistrurus ; Male-male combat ; Mating season ; Reproductive cycles ; Denning ; Estrus

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