The interaction of questions in evolutionary ecology

Throughout the book several issues have been raised in more than one chapter, implying that understanding one topic in evolutionary ecology can enhance understanding of another. This occurs for two reasons. First, the topics are biologically interdependent. Second, the techniques we can use to aid understanding are often general. These connections have also led many notable evolutionary ecologists to move from one subject to the next. Let us now recap the connections illustrated by the book (Figure 16.1).

Macroecology Major evolutionary

Macroecology Major evolutionary

Evolution of specialization

Evolution of population dynamics

Fig. 16.1 The interactions between different subject areas in evolutionary ecology mentioned in this book.

Evolution of specialization

Evolution of population dynamics

Fig. 16.1 The interactions between different subject areas in evolutionary ecology mentioned in this book.

In the last chapter, we saw that understanding macroecological patterns is sometimes helped by an understanding of life history evolution. For example, one macroecological pattern, the body size frequency distribution, involves variation in a life history trait. Macroevolutionary forces, such as rates of speciation and extinction, also affect many of these patterns, such as why there are more species in the tropics. Macroevolutionary patterns are also sometimes the result of major ecological or evolutionary transitions, such as the evolution of sex or flight. They are often explicable by reference to speciation and extinction theory, such as in the haplochromine cichlids of Lake Victoria. Extinction is often the result of variation in life histories, such as fecundity, ecological specialization, with specialists being more extinction prone, or co-evolutionary forces, such that invasive species can cause extinction of species that they have not co-evolved with. The theory of extinction suggests that species that have small ranges are at risk of extinction, and this explains some macroevolutionary observations on extinction rates across taxa.

Speciation can be enhanced by rapid evolutionary forces, such as sexual selection, as in haplochromine cichlids, or conflict between evolutionary entities, as in cytoplasmic male sterility, or changes in ecological specialization, as in apple maggot fly, or co-evolutionary forces, as in diversifying co-evolution. Co-evolution characteristically results in changes in antagonism, changes in specialization, changes in population dynamics. Changes in antagonism have resulted in many of the major evolutionary transitions, can affect specialization through expansion or contraction of the ecological niche, can affect life history evolution through trade-offs with virulence, population dynamics through its influence on vital rates, and can result in extinction as a co-evolutionary process. Evolutionary changes in population dynamics can be caused by adaptive changes in behaviour, as in many bird and mammal species, can cause speciation through evolutionary branching and extinction through adaptive suicide.

Plastic phenotypic responses can cause speciation, such as through mate choice or conflict between entities. Dispersal and dormancy affect the degree of antagonism between species and among species, and sex allocation through determining population structure, and life history evolution through trade-offs, and speciation, and extinction rates. Sex allocation is affected by co-evolution and conflict of interest among entities and can cause speciation. The major transitions in ecology are recognized by their macroevolutionary effects, and some, such as the evolution of flowers and of animal phyla, may have been the result of co-evolutionary forces. Others, such as flight, have affected dispersal ability in many taxa.

Are any of these topics particularly pervasive? Cooperation and conflict, dispersal, and life history evolution permeate many areas of evolutionary ecology and might be considered central. Macroevolution is a force contributing to phenotypic distribution of many of the traits of interest.

In addition to this web of interactions between the topics is a web of mutually useful methods and tools. Optimization theory, evolutionary stable strategies, adaptive dynamics, and population genetics are theoretical tools that are broadly applicable in evolutionary ecology. Similarly, empirical tools such as phylogenies and the comparative method, unmanipulated observations, and controlled experiments are useful in nearly all areas. Thus, the tools of evolutionary ecology as well as the concepts are mutually supporting.

The picture provided by Figure 16.1 is a picture of evolutionary ecology, it also describes an evolving biosphere and the forces that shape it. It is the message of this book.

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