Skewed sex ratio in a forest salamander: artefact of the different capture probabilities between sexes or actual ecological trait?

in Amphibia-Reptilia
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Sex ratio is an essential demographic parameter and distortions from a balanced sex ratio may have contrasting effects on the population dynamics. However, observation of distorted sex ratio using counts or captures may reflect an actual ecological trait of the studied population but may also be an artefact due to different capture probabilities of males and females. We compared results obtained from Counts and Capture-Marking-Recapture (CMR) on both sexes in a population of a forest dwelling salamander, Salamandrina perspicillata, and we investigated if males and females had different capture probabilities. We surveyed available literature to compare information on sex ratio from other populations of S. perspicillata. The sex ratio from our counts was 0.65 and was significantly male-biased as reported in other studies. The estimated sex ratio from CMR data was 0.57. Although males showed higher recapture rates than females in every capture session, these differences were not statistically significant. Therefore, the skewed sex ratio towards males is not only an artefact due to different capture probabilities between males and females but reflects an actual demographic trait, although the magnitude of the skeweness was overestimated by counts.

Skewed sex ratio in a forest salamander: artefact of the different capture probabilities between sexes or actual ecological trait?

in Amphibia-Reptilia

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Figures

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    Percentage of individual captures (1) and recaptures (2-4) of males (n = 194) and females (n = 103) during six sampling occasions in a population of Salamandrina perspicillata in the Montedimezzo Nature Reserve (Central Italy).

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    Mean capture probabilities (and 95% C.I.) of males and females during six sampling occasions in a population of Salamandrina perspicillata in the Montedimezzo Nature Reserve (Central Italy).

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    Estimated effect sizes from studies reporting skewed sex ratio in Salamandrina. The prism shows the overall estimated incidence rate, from random effect model.

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