American Society of Naturalists

A membership society whose goal is to advance and to diffuse knowledge of organic evolution and other broad biological principles so as to enhance the conceptual unification of the biological sciences.

“Climate effects on growth, body condition and survival depend on the genetic characteristics of the population”

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Cristina Romero-Diaz, Merel C. Breedveld, and Patrick S. Fitze

Climate effects on populations are context dependent; Age and sex structures and genetic characteristics matter

A new experiment with lizards exposes the interplay between ecology and evolution, a process that can affect our predictions of population responses to climate change

Adult male common lizard (<i>Zootoca vivipara</i>) in one of the semi-natural populations of the study.<br />(Credit: C. Romero-Diaz)
Adult male common lizard (Zootoca vivipara) in one of the semi-natural populations of the study.
(Credit: C. Romero-Diaz)

Predicting how changes in the environmental conditions will affect the size and structure (e.g. age composition, sex ratio) of natural populations over time, and thus their chances of persistence/extinction, may prove to be more complicated than we thought. Why? The reason behind this complexity is a process known as eco-evolutionary dynamics; that is, the ongoing feedbacks between ecological change and evolutionary change. Experimental support for this idea comes from a new population study with lizards, carried out by researchers from the National Museum of Natural Sciences in Madrid, Spain (MNCN-CSIC), showing that trait responses to environmental conditions depend on the genetic characteristics of the population.

Eco-evolutionary feedbacks can occur between natural selection and population dynamics, when a demographic trait (e.g. survival, reproductive success) responds to ecological selective pressures determined by the environmental conditions, and the resulting change in population density and/or composition modifies the environment, thereby changing the nature of selection. Understanding the role of population dynamics in shaping selection pressures is thus key in order to predict population responses under novel climates.

Adult male common lizard (<i>Z. vivipara</i>).<br />(Credit: C. Romero-Diaz)
Adult male common lizard (Z. vivipara).
(Credit: C. Romero-Diaz)

The researchers at the MNCN have been studying population dynamics of the color polymorphic common lizard (Zootoca vivipara) in the Spanish Pyrenees for years. In this year-long experiment with semi-natural populations, focusing on the interactive effects of abiotic conditions and genetic characteristics of the population, they reveal that individual responses in growth, body condition, survival, and reproduction to habitat humidity depend on the (genetic) color morph frequencies of the population. Moreover, individual responses are age-class- and sex-dependent, suggesting different susceptibilities to environmental conditions among juveniles, yearlings and adults, and between males and females. Taken together, their results suggest that changes in the demographic characteristics of populations, genetic or otherwise, alter the level of intra- and inter-age class competition experienced by their individuals and thus the ecological selective pressures shaping fitness-related traits.

This study is one of the few empirical evidences to date supporting the idea that ecology can influence evolution, and vice versa, on short/ecological time-scales. Read the Article