Ecological fitting

Abstract: In this text, Thompson advances a new conceptual approach to the evolution of species interactions - the geographic mosaic theory of coevolution. Thompson demonstrates how an integrated study of life histories, genetics and the geographic structure of populations yields a broader understanding of coevolution, or the development of reciprocal adaptations and specializations in interdependent species. Using examples of species interaction from a range of taxa, Thompson examines how and when extreme specialization evolves in interdependent species and how geographic differences in specialization, adaptation and the outcomes of interactions shape coevolution. Through the geographic mosaic theory, Thompson creates connections between the study of specialization and coevolution in local communities and the study of broader patterns seen in comparisons of the phylogenies of interacting species.

Abstract: Coevolution - reciprocal evolutionary change in interacting species driven by natural selection - is one of the most important ecological and genetic processes organizing the earth's biodiversity: most plants and animals require coevolved interactions with other species to survive and reproduce. The Geographic Mosaic of Coevolution analyzes how the biology of species provides the raw material for long-term coevolution, evaluates how local coadaptation forms the basic module of coevolutionary change, and explores how the coevolutionary process reshapes locally coevolving interactions across the earth's constantly changing landscapes. Picking up where his influential The Coevolutionary Process left off, John N. Thompson synthesizes the state of a rapidly developing science that integrates approaches from evolutionary ecology, population genetics, phylogeography, systematics, evolutionary biochemistry and physiology, and molecular biology. Using models, data, and hypotheses to develop a complete conceptual framework, Thompson also draws on examples from a wide range of taxa and environments, illustrating the expanding breadth and depth of research in coevolutionary biology.

Abstract: 'Coevolution' may be usefully defined as an evolutionary change in a trait of the individuals in one population in response to a trait of the individuals of a second population, followed by an evolutionary response by the second population to the change in the first. 'Diffuse coevolution' occurs when either or both populations in the above definition are represented by an array of populations that generate a selective pressure as a group. Ehrlich and Raven's (1964) classic paper on the interactions of butterflies and plants was the first essay explicitly focused on coevolution. However, they did not define coevolution, and butterflies were neither stated nor implied to have been the single populations or array of herbivores that have generated the plant traits that they discuss as causing butterfly distributions on host plants. I believe that the lack of an original definition of 'coevolution,' the inapplicability of the example chosen by the original advocates of the use of the term, and the obvious commonplace nature of coevolutionary events in the history of plant-animal interactions have led to misleading uses of the term in contemporary evolutionary thought and studies. Here, I wish to call for more careful attention to the use of 'coevolution' as a word and concept. There are three conspicuous misuses at present: 1) It is commonly assumed that a pair of species whose traits are mutualistically congruent have coevolved. For example, it is quite possible that the fruit traits of a mammal-dispersed seed coevolved with the mammal's dietary needs. However, it is also quite possible that the mammal entered the plant's habitat with its dietary preferences already established and simply began feeding on the fruits of the species that fulfilled them. When this occurs, it is those species that are most exactly congruent which will appear most coevolved yet are likely to be the least coevolved. Are the hard seeds of those aridland trees dispersed by passage through a contemporary mammal gut coevolved with the mammal? Not necessarily. 2) In similar manner, a herbivore parasitic on a plant is often thought of as coevolved with the defense timing, chemistry, morphology, etc. However, when a parasite arrives in a new habitat, it will feed on those species whose defense traits it can circumvent because of the abilities it carries at the time. Such a parasite cannot be distinguished from one that evolved the ability to circumvent a defense while in trophic contact with its host. 3) When other evidence makes it clear that a parasite has evolved traits to circumvent the defenses of its host, it is frequently automatically assumed that coevolution has occurred. However, it is not necessary to conclude that the defense trait circumvented was evolutionarily produced in response to the parasite in question. In fact, it is likely that many defense traits of plants were produced through coevolution with animals no longer present in their habitat or no longer parasitizing them if present. Strongly coevolved parasite-host systems probably as often proceed to ecological independence of the participants as to relatively benign parasitism. In summary, I plead for the retention of the usefulness of 'coevolution' by removing it from synonymy of usage with 'interaction, '"symbiosis, '"mutualism,' and 'animal-plant interaction.' A bee is not necessarily coevolved with the flower it pollinates, a caterpillar is not necessarily

Abstract: The evolutionary interactions between plants and phytophagous insects are asymmetric: the biochemical and structural diversity of the angiosperms provide a profusion of niches for the evolutionary radiation (cladogenesis) of the insects, while the insects do not affect plant evolution or, at most, may cause anagenic changes in the plants. (Figwasps and figs may represent a rare case of coevolution sensu stricto.) Thus, the evolution of insects generally follows that of the plants ("sequential evolution"). Because the selection pressure exerted by insect attacks is weak or lacking, they could not have been the main cause of the appearance and maintenance of allelochemicals in plants. Nevertheless, these compounds basically determine the plants' "biochemical profile" by which the insects distinguish between host and nonhost plants. Interspecific competition is largely lacking among phytophagous insects in natural communities, so it could not have evoked stenophagy (i.e., resource partitioning) in the insect...