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Urban versus forest ecotypes are not explained by divergent reproductive selection
Aude E Caizergues1, Arnaud Grégoire2, Anne Charmantier2
1CEFE, CNRS, Université de Montpellier, Université Paul Valery Montpelliers, EPHE, IRD, Montpellier, France aude.caizergues@cefe.cnrs.fr.
Proceedings. Biological Sciences
|July 28, 2018
Summary
Urbanization causes great tits (Parus major) to diverge in morphology and life history. However, differing natural selection pressures between urban and forest environments do not fully explain these phenotypic changes.
Area of Science:
- Ecology
- Evolutionary Biology
- Urban Ecology
Background:
- Urbanization drives rapid environmental change, prompting adaptive responses in wildlife.
- Phenotypic divergence between urban and rural populations is well-documented, but comparative selection analyses are rare.
Purpose of the Study:
- To compare phenotypic divergence and natural selection pressures on great tits (Parus major) in urban versus forest habitats.
- To investigate whether contemporary reproductive selection explains observed trait differences.
Main Methods:
- Seven years of monitoring of great tits in Montpellier city and a nearby oak forest.
- Measurement of morphological and life-history traits.
- Analysis of reproductive selection gradients for divergent traits between habitats.
Main Results:
- Urban great tits exhibited smaller morphological features (tarsus, body mass, wing/tail length) and earlier laying dates/smaller clutches compared to forest birds.
- Selection gradients differed significantly between habitats only for body mass.
- Selection favored earlier laying in forests but not cities, and larger clutch sizes in cities but not forests.
Conclusions:
- Contemporary reproductive selection does not fully explain the observed phenotypic divergence between urban and forest great tits.
- Further experimental studies are needed to confirm if divergence is maladaptive and identify environmental drivers.
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