Female-biased sex ratios in subarctic common frogs

J. S. Alho, G. Herczeg, J. Merilä

Research output: Contribution to journalArticle

29 Citations (Scopus)

Abstract

In vertebrates with genetic sex determination, large deviations from the 1:1 sex ratio at the population level are rare and demand an explanation. We investigated adult sex-ratio variation of common frogs Rana temporaria in two subarctic breeding ponds over a 6-year (1999-2004) period using capture-mark-recapture (CMR) methods. Using the same data, we also tested for the occurrence of the biannual breeding cycle in female common frogs and sought evidence for population size decline. Sex ratios were highly female biased in both populations: on average, only about 30% of breeding individuals were males. CMR analyses further suggested that the female-biased sex ratio was not explainable by higher adult mortality among males as the survival probabilities over years were similar (c. 70%) for both sexes. Alternative explanations for these highly female-biased sex ratios include sex-specific mortality at earlier life stages and environmental influences on the sex determination system. While further studies are required to differentiate between the alternatives, the observed sex-ratio bias is among the strongest reported in any amphibian population so far, and also in the direction opposite to that usually observed (males>females). Our analyses found no support for the contention that female common frogs in northern populations may reproduce only in every second year. However, both study populations were declining during the study period.

Original languageEnglish
Pages (from-to)57-63
Number of pages7
JournalJournal of Zoology
Volume275
Issue number1
DOIs
Publication statusPublished - May 2008

Fingerprint

frog
sex ratio
frogs
sex determination
gender
breeding
mark-recapture method
mortality
Rana temporaria
reproductive cycle
amphibian
amphibians
population size
vertebrate
pond
vertebrates

Keywords

  • Arctic
  • CMR analysis
  • Population decline
  • Reproduction
  • Sex ratio
  • Survival

ASJC Scopus subject areas

  • Animal Science and Zoology

Cite this

Female-biased sex ratios in subarctic common frogs. / Alho, J. S.; Herczeg, G.; Merilä, J.

In: Journal of Zoology, Vol. 275, No. 1, 05.2008, p. 57-63.

Research output: Contribution to journalArticle

Alho, J. S. ; Herczeg, G. ; Merilä, J. / Female-biased sex ratios in subarctic common frogs. In: Journal of Zoology. 2008 ; Vol. 275, No. 1. pp. 57-63.
@article{02c97c9ae19b409b880237605d322b44,
title = "Female-biased sex ratios in subarctic common frogs",
abstract = "In vertebrates with genetic sex determination, large deviations from the 1:1 sex ratio at the population level are rare and demand an explanation. We investigated adult sex-ratio variation of common frogs Rana temporaria in two subarctic breeding ponds over a 6-year (1999-2004) period using capture-mark-recapture (CMR) methods. Using the same data, we also tested for the occurrence of the biannual breeding cycle in female common frogs and sought evidence for population size decline. Sex ratios were highly female biased in both populations: on average, only about 30{\%} of breeding individuals were males. CMR analyses further suggested that the female-biased sex ratio was not explainable by higher adult mortality among males as the survival probabilities over years were similar (c. 70{\%}) for both sexes. Alternative explanations for these highly female-biased sex ratios include sex-specific mortality at earlier life stages and environmental influences on the sex determination system. While further studies are required to differentiate between the alternatives, the observed sex-ratio bias is among the strongest reported in any amphibian population so far, and also in the direction opposite to that usually observed (males>females). Our analyses found no support for the contention that female common frogs in northern populations may reproduce only in every second year. However, both study populations were declining during the study period.",
keywords = "Arctic, CMR analysis, Population decline, Reproduction, Sex ratio, Survival",
author = "Alho, {J. S.} and G. Herczeg and J. Meril{\"a}",
year = "2008",
month = "5",
doi = "10.1111/j.1469-7998.2007.00409.x",
language = "English",
volume = "275",
pages = "57--63",
journal = "Journal of Zoology",
issn = "0952-8369",
publisher = "Wiley-Blackwell",
number = "1",

}

TY - JOUR

T1 - Female-biased sex ratios in subarctic common frogs

AU - Alho, J. S.

AU - Herczeg, G.

AU - Merilä, J.

PY - 2008/5

Y1 - 2008/5

N2 - In vertebrates with genetic sex determination, large deviations from the 1:1 sex ratio at the population level are rare and demand an explanation. We investigated adult sex-ratio variation of common frogs Rana temporaria in two subarctic breeding ponds over a 6-year (1999-2004) period using capture-mark-recapture (CMR) methods. Using the same data, we also tested for the occurrence of the biannual breeding cycle in female common frogs and sought evidence for population size decline. Sex ratios were highly female biased in both populations: on average, only about 30% of breeding individuals were males. CMR analyses further suggested that the female-biased sex ratio was not explainable by higher adult mortality among males as the survival probabilities over years were similar (c. 70%) for both sexes. Alternative explanations for these highly female-biased sex ratios include sex-specific mortality at earlier life stages and environmental influences on the sex determination system. While further studies are required to differentiate between the alternatives, the observed sex-ratio bias is among the strongest reported in any amphibian population so far, and also in the direction opposite to that usually observed (males>females). Our analyses found no support for the contention that female common frogs in northern populations may reproduce only in every second year. However, both study populations were declining during the study period.

AB - In vertebrates with genetic sex determination, large deviations from the 1:1 sex ratio at the population level are rare and demand an explanation. We investigated adult sex-ratio variation of common frogs Rana temporaria in two subarctic breeding ponds over a 6-year (1999-2004) period using capture-mark-recapture (CMR) methods. Using the same data, we also tested for the occurrence of the biannual breeding cycle in female common frogs and sought evidence for population size decline. Sex ratios were highly female biased in both populations: on average, only about 30% of breeding individuals were males. CMR analyses further suggested that the female-biased sex ratio was not explainable by higher adult mortality among males as the survival probabilities over years were similar (c. 70%) for both sexes. Alternative explanations for these highly female-biased sex ratios include sex-specific mortality at earlier life stages and environmental influences on the sex determination system. While further studies are required to differentiate between the alternatives, the observed sex-ratio bias is among the strongest reported in any amphibian population so far, and also in the direction opposite to that usually observed (males>females). Our analyses found no support for the contention that female common frogs in northern populations may reproduce only in every second year. However, both study populations were declining during the study period.

KW - Arctic

KW - CMR analysis

KW - Population decline

KW - Reproduction

KW - Sex ratio

KW - Survival

UR - http://www.scopus.com/inward/record.url?scp=42549133905&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=42549133905&partnerID=8YFLogxK

U2 - 10.1111/j.1469-7998.2007.00409.x

DO - 10.1111/j.1469-7998.2007.00409.x

M3 - Article

AN - SCOPUS:42549133905

VL - 275

SP - 57

EP - 63

JO - Journal of Zoology

JF - Journal of Zoology

SN - 0952-8369

IS - 1

ER -