Abstract:
Specificity at different stages in the interaction was studied in a common neotropical fig, Ficus pertusa, particularly in relation to its sympatric congener F. tuerckheimii. 99% of pollinators arriving at sticky traps on flowering figs were the specialist species. Foreign pollinators virtually never entered F. pertusa syconia to oviposit or emerged from mature fruits. Pollinators arrive at F. pertusa trees in a one-day burst that is well timed with the presence of unpollinated syconia, providing evidence for the existence of a species-specific volatile attractant. Some nonpollinating wasps associated with F. pertusa appear to use the same attractant to locate the tree.-from Author
PMID: 11958708;PMCID: PMC1690960;Abstract:
Interspecific mutualisms have been playing a central role in the functioning of all ecosystems since the early history of life. Yet the theory of coevolution of mutualists is virtually nonexistent, by contrast with well-developed coevolutionary theories of competition, predator-prey and host-parasite interactions. This has prevented resolution of a basic puzzle posed by mutualisms: their persistence in spite of apparent evolutionary instability. The selective advantage of 'cheating', that is, reaping mutualistic benefits while providing fewer commodities to the partner species, is commonly believed to erode a mutualistic interaction, leading to its dissolution or reciprocal extinction. However, recent empirical findings indicate that stable associations of mutualists and cheaters have existed over long evolutionary periods. Here, we show that asymmetrical competition within species for the commodities offered by mutualistic partners provides a simple and testable ecological mechanism that can account for the long-term persistence of mutualisms. Cheating, in effect, establishes a background against which better mutualists can display any competitive superiority. This can lead to the coexistence and divergence of mutualist and cheater phenotypes, as well as to the coexistence of ecologically similar, but unrelated mutualists and cheaters.
Abstract:
It is widely believed that mutualisms, interspecific interactions that benefit both species, have been grossly neglected relative to their true importance in nature. I have reviewed the recent primary literature in order to assess quantitatively the frequency of studies of mutualism, the types of questions they address, and their general scientific approach. All articles appearing from 1986 to 1990 in nine major journals that publish ecological and evolutionary research were examined. It is clear that mutualism research is not in fact rare. Studies of interspecific interactions made up about 22 % of the over 4500 articles published during this period; of these, about one-quarter investigated some form of mutualism. Over 90 % of them investigated plant-animal interactions, primarily pollination (52 %) and seed dispersal (31 %), a bias probably related in part to the particular journals examined. The diversity of questions addressed in these articles was surprisingly low. The majority (63 %) focused simply on identifying the mutualists of some species of interest. Furthermore, almost all studies were unilateral, that is, they focused on only one of the interacting species, plants being studied much more frequently than their animal partners. Mutualism studies do not appear to have focused on mutualism as a form of interaction in the same way as studies of competition and predation. Rather, researchers have treated mutualism primarily as a life history attribute of one of the two partners. Consequently, although an impressive amount of information has accumulated about these interactions, we are still far from achieving an overall picture that transcends the boundaries of particular taxa or combinations of taxa. Three other obstacles have prevented data on mutualisms from being brought together: the historical isolation of studies of different kinds of mutualism, a nearly total disconnection between mutualism theories and empirical studies, and the unilateral approach almost always used to study these bilateral interactions. I identify eight research questions whose answers have the potential to reveal broad-based generalizations about the evolution and ecology of mutualism.
PMID: 22583047;Abstract:
Mutualisms are interspecific interactions that yield reciprocal benefits. Here, by adopting a consumer-resource perspective, we show how considering competition is necessary in order to understand the evolutionary and ecological dynamics of mutualism. We first review the ways in which competition shapes the ecology of mutualisms, using a graphical framework based on resource flows rather than net effects to highlight the opportunities for competition. We then describe the known mechanisms of competition and show how it is a critical driver of the evolutionary dynamics, persistence, and diversification of mutualism. We argue that empirical and theoretical research on the ecology and evolution of mutualisms will jointly progress by addressing four key points: (i) the existence and shape of physiological trade-offs among cooperation, competition, and other life-history and functional traits; (ii) the capacity for individuals to express conditional responses to variation in their mutualistic and competitive environment; (iii) the existence of heritable variation for mutualistic and competitive traits and their potentially conditional expression; and (iv) the structure of the network of consumer-resource interactions in which individuals are embedded. © 2012 New York Academy of Sciences.
