Ecological Genetics

Abstract

Ecological genetics is the study of how ecologically relevant traits evolve in natural populations. Early research in ecological genetics demonstrated that natural selection often is strong enough to generate rapid adaptive changes in nature. Current work has expanded our understanding of the temporal and spatial scales at which natural selection can operate in nature. Modern ecological geneticists combine field observations, laboratory experiments and rapidly improving laboratory techniques to further our understanding about how traits evolve in nature. Genomic techniques are rapidly providing tools to identify regions under selection or that have changed through evolution. Ecological geneticists increasingly explore how evolutionary dynamics shape ecological properties. Consequently, ecological genetics is highly relevant to practical questions that lie at the interface of ecology and evolution.

Key Concepts

  • Ecological genetics is concerned with how traits evolve in natural populations.
  • Ecological geneticists apply a combination of natural surveys and experiments in the laboratory and in the field to discern genetic from plastic phenotypic variation and the agents of natural selection that determine this variation.
  • The ecological geneticist seeks to determine the dominant agents of selection in an environment and associate genetic variation to these selective agents and random drift.
  • Ecological genetics is concerned both with the spatial and temporal scales over which evolution can occur in nature and the constraints that prevent it.
  • Genomic methods provide new tools to gain a more complete understanding of genetic variation in nature as well as the agents of natural selection; genomics has so permeated ecological genetics that ecological genomics increasingly is used in place of ecological genetics.
  • Recent research has revealed evidence for adaptations in natural populations over rapid timescales and fine spatial scales.
  • This evidence for rapid or microgeographic adaptation argues for an increasing understanding of how evolution in nature affects ecological dynamics and patterns.
  • Most natural populations exchange genes and many habitats undergo recurrent extinction and colonisation dynamics, arguing for a metapopulation approach that incorporates a spatial perspective.
  • Species interactions often create strong selection on traits, and when two or more species adapt reciprocally to the other's evolving traits, coevolution occurs.
  • Ecological genetics can inform applied questions such as when natural pests or pathogens interact with agriculture or adaptation determines the dynamics of fisheries, thus making it relevant to human economy and welfare.

Keywords: adaptation; evolutionary ecology; metapopulation genetics; gene flow; coevolution

Figure 1. Ecological geneticists often use common garden experiments to understand the potential determinants of phenotypic variation in natural populations. Here, I assume two populations of tadpoles. Population A lives in a habitat devoid of predators and Population B lives in a habitat with predaceous dragonflies, creating a potential landscape mosaic of heterogeneous selection. The two tadpoles differ in their phenotypes such that the ones living with the predaceous dragonflies have larger tailfins than the other population. A common garden experiment is performed in which eggs from each population are collected from the two natural populations and raised in a controlled environment with and without dragonflies (with each combination replicated many times). Three divergent phenotypic outcomes that might characterise tadpoles raised in the common garden are depicted. If individuals from both populations have bigger tailfins when grown with predaceous dragonflies, but otherwise, the populations have similar phenotypes, then nongenetic phenotypic plasticity likely underlies the observed variation. However, if Population B consistently has larger tailfins regardless of treatment and Population A does not (second row), then this finding suggests that bigger tailfins might have evolved in Population B. Two caveats are worth mentioning here. First, we would need to confirm that bigger tailfins are associated with higher fitness under attack by predaceous dragonflies through a natural selection experiment. If tailfins do not give rise to higher fitness, they might have evolved due to random drift. Second, maternal effects, the nongenetic inheritance of traits from mothers (e.g. bigger mothers have bigger offspring) could confound results; whenever possible, several generations should be raised in the common garden to eliminate maternal effects. In the topmost row, Population B shows a plastic reaction to dragonflies, whereas Population A does not. This result suggests the evolution of plasticity (a gene by environment interaction) in Population A.
Figure 2. Adaptive evolution can occur quite quickly, demonstrating substantial changes in trait evolution over the course of just a few generations. Here, the median rates of adaptation (in standard deviations of phenotypic change per generation, the ‘Haldane’) compiled from published studies are arranged by geometrically distributed bins. Each bin estimates the evolutionary rates from published studies analysed over the number of generations greater than the prior bin up to and including the value of the bin. Note that no data were available for the 1–2 generations bin. Evolutionary rates are high at first but decline when analysed over longer time spans, possibly because optima are quickly reached or because natural selection gradients rapidly reverse, leading to less overall long‐term phenotypic change. Data from Kinnison and Hendry (2001).
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Further Reading

Conner JK and Hartl DL (2004) A Primer of Ecological Genetics. Sunderland, MA: Sinauer Associates, Inc.

Falconer DS and Mackay TFC (1996) Introduction to Quantitative Genetics, 4th edn. Essex: Longman.

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Roff DA (2002) Life History Evolution. Sunderland, MA: Sinauer Assoc., Inc.

Thompson JN (1999) The evolution of species interactions. Science 284: 2116–2118.

Urban MC (2011) The evolution of species interactions across natural landscapes. Ecology Letters 14 (7): 723–732.

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How to Cite close
Urban, Mark C(Sep 2016) Ecological Genetics. In: eLS. John Wiley & Sons Ltd, Chichester. http://www.els.net [doi: 10.1002/9780470015902.a0021214.pub2]