Abstracts (first author)

Talk 

Quantifying the demographic cost of selection in a changing environment

Author(s): Reed TE, Gienapp P, Visser ME

Summary:

The lag load, or reduction in mean fitness caused by incomplete adaptive tracking of a moving phenotypic optimum, is a key quantity in models of evolution in changing environments. Despite its central theoretical importance, empirical studies quantifying the lag load and the factors affecting it are lacking. Here we explore these issues in a Dutch population of great tits Parus major, where warming springs have generated a mismatch between annual breeding time and the timing of an important food resource, providing an ideal opportunity to examine how the resulting directional selection for earlier breeding time impacts population mean fitness and related demographic parameters. First, we show that interannual variation in mismatch over almost four decades has surprisingly not affected population growth, despite it having led to intensified directional selection. We demonstrate an important mechanism contributing to this uncoupling, whereby fitness losses associated with mismatch are counteracted by fitness gains due to relaxed competition. Next, we parameterised a quantitative genetic model to predict the theoretical ‘critical rate of environmental change’, beyond which increased maladaptation leads to population extinction. Results imply that even ‘mild’ rates of climate change would be close to the critical rate. However, individual-based simulations that account for both evolutionary processes and density dependence revealed that the expected time to extinction, although highly uncertain, is on the order or centuries, rather than decades. These findings imply that microevolution would only rescue the population from mild rates of sustained climate change. On the other hand, they also illustrate that considerable maladaptation can be demographically tolerated in the short term through density dependence, without immediate population declines, effectively ‘buying time’ for microevolution to restore adaptation until the environment (climate) stabilises.


Video


Abstracts (coauthor)

Summary:

Continuous environmental change can lead to selection on the reaction norm slope if it alters the relationship between the optimal phenotype and environmental cues that determine the actual phenotype. For example, breeding time in small insectivorous birds, as e.g. great tits or flycatchers, is determined by temperatures in early spring while their reproductive success depends on insect phenology determined by temperatures in late spring. Differential changes of these two temperatures could alter the relationship between the cues used by the birds and the insect phenology and lead to selection on the slope of the birds’ breeding time reaction norm. There are however a number of factors that could additionally affect the strength of this selection: It has been argued that in long-lived organisms plasticity would be more adaptive than in short-lived organisms because long-lived organisms experience a larger range of environments. Another relevant factor is temporal autocorrelation of environments: positive or negative autocorrelation will lead to environments experienced by an individual being more or less similar, which would affect the strength of selection on plasticity. The correlation between cues and optimal phenotypes also affects the strength of selection on plasticity as a low ‘cue reliability’ would select for less plasticity. Using simulation models we explored these effects in a scenario of a directionally changing environment focusing on phenological traits under climate change. Phenological traits are heritable but most genetic variation is present in the intercept of the reaction norm rather than the slope. Since the evolutionary potential of plasticity hence seems to be limited, strong selection on it would have negative demographic consequences. Consequently, it is important to know whether and how strongly environmental change would lead to selection on plasticity to better assess potential extinction risk caused by environmental change.

Contacts

Chairman: Octávio S. Paulo
Tel: 00 351 217500614 direct
Tel: 00 351 217500000 ext22359
Fax: 00 351 217500028
email: mail@eseb2013.com

Address

XIV Congress of the European Society for Evolutionary Biology

Organization Team
Department of Animal Biology (DBA)
Faculty of Sciences of the University of Lisbon
P-1749-016 Lisbon
Portugal

Website

Computational Biology & Population Genomics Group 
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