Ecological and Evolutionary Responses to Climate Change (July 2017): The Biological Effects of Climate Change

As traditionally considered, ecology and evolution are complementary but distinct branches of the biological sciences. Ecology typically focuses on interactions among species and with the environment, while evolution focuses on changes over time, often as driven by differential survival in response to ecological and/or environmental conditions.

The rapidity and severity of contemporary climate change has the potential to blur the distinction between ecological and evolutionary responses. In some cases, ecological features of a given organism can strongly shape opportunities for evolution in response to climate change. For example, species that typically exist in very large populations will, on average, have greater genetic diversity and therefore greater potential for rapid evolutionary responses to altered climate conditions than do species with smaller population sizes. As a result, readers who do not have a strong background in ecology and/or evolution benefit from reading about fundamental concepts in these areas.

Ecology, by Robert E. Ricklefs, provides a sweeping, textbook-style introduction to the field. For background on population genetics and evolution, it is suggested that one pair Carl Zimmer’s Tangled Bank: An Introduction to Evolution with Daniel L. Hartl’s classic Principles of Population Genetics.

Plasticity, the ability of an organism to shift its behavior and/or physiology in the absence of genetic change, can further blur the distinction between ecological and evolutionary responses. For example, in some cases, plastic responses may “buy time,” enabling a species to persist by buffering against the differential survival of individuals with disparate genetic features, slowing the pace of evolution while preserving populations at sizes more responsive to selective pressures. Moreover, the extent of plasticity is itself subject to evolutionary pressures. Patrick Bateson and Peter Gluckman’s Plasticity, Robustness, Development and Evolution provides an extensive explanation of plasticity producing phenotypic variation and alteration in the absence (at least at first) of evolutionary change. Editors Christian Landry and Nadia Aubin-Horth address the ecological/evolutionary distinction, as well as its limitations, even more directly through a series of case studies in Ecological Genomics: Ecology and the Evolution of Genes and Genomes.

Phenology describes the set of processes that determine when during a season or a year a given organism will undergo some process. For annual plants, phenology includes the timing of the spring bloom; for migratory animals, it includes the date of arrival in winter breeding grounds. Phenological shifts in response to a change in climate can be either plastic, in the sense that they can occur in the absence of genetic change, or evolutionary, arising through higher rates of survival and reproduction for individuals that carry specific genetic variants.

One of the primary challenges in assessing the phenological responses to climate change is that there is only limited information on the phenology of species under present climate conditions. Loren Gilbert’s Phenology and Climate Change compiles a large set of phenological observations, providing a valuable benchmark for studies of shifting timing. Phenology of Ecosystem Processes: Applications in Global Change Research, edited by Asko Noormets, has a broadly similar goal, with an additional focus on how mathematical modeling can be used to make predictions from existing phenological data—especially those collected for populations across a temperature gradient.

In Walden Warming: Climate Change Comes to Thoreau’s Woods, Richard Primack compares the first-blooming dates of wildflowers compiled by Thoreau in the mid-19th century with his own observations of many of the same species some 150 years later. Journal articles, including “Phylogenetic Patterns of Species Loss in Thoreau’s Woods Are Driven by Climate Change,” by Charles G. Willis, Brad Ruhfel, Richard B. Primack, Abraham J. Miller-Rushing, and Charles C. Davis, have provided additional evidence of phenological changes, primarily in plants, while pointing out that data sets suitable for comparison are lacking in many groups of organisms.