Ecological fitting
Ecological fitting is "the process whereby organisms colonize and persist in novel environments, use novel resources or form novel associations with other species as a result of the suites of traits that they carry at the time they encounter the novel condition".
In this framework, the organism occupies a multidimensional operative environment defined by the conditions in which it can persist, similar to the idea of the Hutchinsonian niche.
He expanded this idea in a 1985 paper[9] written while visiting Santa Rosa National Park in Costa Rica.
He described the cyclical life history pattern he believed responsible for this pattern: a species begins as a small population occupying a small area with little genetic variation, but then over the course of a few generations grows to occupy a large area, either because of the emergence of a genotype successful over a wider range, or because of the removal of a geographic barrier.
He stated that it would be difficult to distinguish between coevolution and ecological fitting, leading ecologists to potentially spurious explanations of current species associations.
[11] When trying to determine which process is at work in a particular interaction, species can only come into contact through biotic expansion and ecological fitting, followed by adaptation or coevolution.
[2][21][22] Phylogenetic conservatism is the latent retention of genetic changes from past conditions: for instance, historical exposure to a certain host may predispose it to colonization in the future.
[2][11][17][19] Finally, fixed traits such as body size may lead to entirely different biotic interactions in different environments; for example, pollinators visiting different sets of flowers.
[24] Additionally, phylogenetic studies show evidence for ecological fitting when lineages of the associated species do not correlate over evolutionary time; that is, if host–parasite or other interactions are as tightly coevolved as was previously believed, parasites should not be switching to unrelated hosts.
[28] Another study examined the time required for sugarcane, Saccharum officinarum, to accumulate diverse arthropod pest communities.
[29] The human-made cloud forest on Green Mountain, Ascension Island, represents an example of how unrelated and unassociated plant species can form a functioning ecosystem without a shared evolutionary history.
[30] Ecological fitting can influence species diversity either by promoting diversification through genetic drift, or by maintaining evolutionary stasis through gene flow.
[33] Finally, a more dramatic form involves the creation of new evolutionary arenas, requiring morphological or ecological changes to gain fitness under new conditions.
[14] Host-plant or other specialized relationships have been previously regarded as an evolutionary 'dead-end' because they seem to limit diversity, but they can actually promote it according to coevolutionary theory.
[15] It is another mechanism, in addition to coevolution and in-situ evolution (in which new phenotypes evolve and travel sympatrically), that can explain the creation and maintenance of species associations within a community.
[30][38] These views of community assembly prompt questions, such as whether species continue stable relationships over time, or if all individuals represent "asymmetrical pegs in square holes".
[9][38] Some of these questions can be answered through phylogenetic studies, which can determine when certain traits arose, and thus whether species interactions and community assembly occurs primarily through coevolution or through dispersal and ecological fitting.
