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Extrinsic Modification of Vertebrate Sex Ratios by Climatic Variation
The American Naturalist
|March 27, 2018
Summary
Climate change, specifically warmer and snowy winters, influences red deer sex ratios, leading to more male offspring. This challenges existing theories on maternal control of offspring sex allocation.
Area of Science:
- Ecology
- Climate Change Biology
- Reproductive Biology
Background:
- Climate influences vertebrate development and offspring viability.
- Climate change may alter offspring sex ratios in terrestrial vertebrates.
- The North Atlantic Oscillation (NAO) is a significant driver of global climatic variation.
Purpose of the Study:
- To investigate the influence of climatic variation (NAO) on red deer offspring sex ratios in Norway.
- To examine how maternal condition and offspring sex are affected by climate during fetal development.
- To explore the long-term effects of climate on sex allocation strategies in red deer.
Main Methods:
- Utilized long-term individual and population-level data for red deer in Norway.
- Analyzed the correlation between North Atlantic Oscillation (NAO) phases and offspring sex ratios.
- Assessed the impact of winter climate conditions (temperature, snowfall) on maternal and offspring characteristics.
Main Results:
- Warmer, snowier winters correlated with male-biased offspring sex ratios in red deer.
- NAO state during fetal development affected male offspring mass, not female offspring mass.
- Hinds born in warmer, snowier winters produced lighter sons and had a tendency towards more male offspring.
Conclusions:
- Offspring sex ratios in red deer are influenced by extrinsic climatic factors, not solely maternal strategies.
- Presents the 'extrinsic modification hypothesis' to explain sex ratio evolution in variable environments.
- Suggests natural selection can shape sex ratios independently of maternal sex allocation in response to climate change.
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