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Environmental correlates of geographic divergence in a phenotypic trait: A case study using bat echolocation
Tinyiko Maluleke1, David S Jacobs1, Henning Winker2
1Department of Biological Sciences Animal Evolution and Systematics Group (AES) University of Cape Town Cape Town South Africa.
Ecology and Evolution
|September 26, 2017
Summary
Isolation by environment drives echolocation frequency divergence in horseshoe bats. Environmental discontinuities, not genetic drift or body size, correlate with resting frequency changes in Rhinolophus damarensis.
Area of Science:
- Evolutionary biology
- Bioacoustics
- Animal behavior
Background:
- Phenotypic divergence arises from evolutionary forces like selection, genetic drift, and plasticity.
- Sensory systems are crucial for survival and reproduction, and their divergence can lead to lineage diversification.
- Isolation by environment (IbE) is a key factor influencing diversification through selection in different environments.
Purpose of the Study:
- To investigate the role of isolation by environment (IbE) in the divergence of resting echolocation frequency (RF) in the horseshoe bat species, Rhinolophus damarensis.
- To test hypotheses including James' Rule, IbE, and isolation by distance (genetic drift) on RF variation.
- To understand how environmental factors and geographic distance influence sensory trait evolution.
Main Methods:
- Sampling of Rhinolophus damarensis bats along a latitudinal gradient in southern Africa (16°S to 32°S).
- Measurement of body size and peak resting echolocation frequencies (RF) from individual bats.
- Statistical analysis to test correlations between RF, body size, geographic distance, and climatic variables (annual mean temperature).
Main Results:
- No support for genetic drift (isolation by distance) as RF variation did not correlate with geographic distance.
- James' Rule was not supported; no significant relationships were found between geographic distance and RF, body size and RF, or body size and climate.
- Support for isolation by environment (IbE) was found, with RF correlating with region and annual mean temperature, indicating environmental discontinuities drive divergence.
Conclusions:
- Environmental discontinuities, particularly temperature gradients, appear to be the primary driver of resting echolocation frequency divergence in Rhinolophus damarensis.
- These environmental factors, coupled with potential directed dispersal, restrict gene flow and promote lineage diversification, aligning with IbE.
- While IbE is supported, the potential contribution of phenotypic plasticity to observed phenotypic variation cannot be excluded.
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