How can mutualism evolve

Living together is not always so convivial, and mutualism works in much the same way as its evil twin — parasitism. Like mutualism, parasitism is a type of symbiosis between two species. In the eyes of natural selection, these two systems differ only in the fitness payoffs to the players in the game. By sheer weight of numbers, most symbioses are asymmetric with one winner and one loser — think of intestinal parasites, flukes that create zombie fish or viruses such as Ebola.

Yet when the interests of different species are the same, beautiful things can happen. Forget stars aligning; the wondrous sight of the softly-glowing Vibrio bacteria housed inside the mantle of the sepiolid squid might lead us to change that old saying. In the world of mutualisms, our squids have aligned! Edition: Available editions United Kingdom. Become an author Sign up as a reader Sign in. The bobtail squid and bioluminscent bacteria are just one of hundreds of examples of mutualism.

Alex Jordan , University of Texas at Austin. Comprehensive review of the genetic and genomic underpinnings of mutualism evolution. Starts from pollination, the best-understood mutualism from a genetic perspective, and extends to other, less heavily studied mutualisms.

Highlights exciting directions for future investigation. Bronstein, J. The only recent volume on mutualism as a unified phenomenon, and a useful entry for readers seeking a general introduction to the field. Several chapters address issues surrounding mutualism evolution. All chapters highlight open questions for future research. Darwin, C. On the various contrivances by which British and foreign orchids are fertilised by insects. New York: D. Darwin dove deep into understanding orchid adaptations to attract pollinators and how pollinator movements on flowers lead to pollination.

A pioneering demonstration of how empirical studies, including small-scale experiments, can illuminate evolutionary patterns and processes. Reprinted Chicago: Univ. Grant, V. Flower pollination in the phlox family.

New York: Columbia Univ. A trailblazing treatment of pollination in a single plant family, and explicitly evolutionary in its consideration of the origin and diversification of key traits, particularly adaptations to attract and reward pollinators. Verne and Karen Grant build a strong link among floral traits, life histories, and breeding systems.

Takes a strongly plant-centric approach. Janzen, D. Co-evolution of mutualism between ants and acacias in Central America. Evolution Lays out a convincing case, using diverse forms of evidence, that obligate associations between ants and Central American acacia plants are mutually beneficial, and that this mutualism is a product of cycles of evolution.

Margulis, L. Origin of eukaryotic cells. Lynn Margulis here lays out a blazingly original interpretation of how eukaryotic cells evolved, including the successive incorporation of bacteria, which may have been mutualistic symbionts, into cell physiology and function as mitochondria and chloroplasts.

Roughgarden, J. Evolution of marine symbiosis—a simple cost-benefit model. Ecology An early, highly influential evolutionary model of a mutualism the anemone-clownfish interaction. Frames the problem in terms of costs and benefits of the interaction to each partner, a perspective that only much later was adopted in empirical studies of mutualism. Sapp, J. Evolution by association: A history of symbiosis. A useful historical overview of the study of symbiosis, with a particular focus on early work on mutualism.

Yucca moths and yucca plants have a reciprocal obligate relationship- the plants cannot make seeds without the yucca moth, and the moth larvae only reach maturity if they eat developing yucca seeds Pellmyr However, mutualist partners do not necessarily rely on each other equally.

For example, many dioecious plant species rely completely on animal pollinators for reproductive success, so from the plant perspective, the interaction is obligate. However, the pollinator species that visit the flowers may or may not require pollen or nectar from that plant species in order to survive and reproduce, so from the pollinator perspective, the interaction could range from obligate to facultative.

Similarly, most bees rely on floral resources for all their needs nectar, pollen, waxes, etc. However, most bee species can utilize resources from a number of flowering plants, so they do not necessarily have obligate relationships with individual plant species. In contrast, some hermaphroditic plant species are self-compatible and also capable of self-pollination, so they can make seeds whether or not their flowers are visited by pollinators.

The mutualism is facultative from the perspective of these plants, although the quality of seeds produced through self-pollination is often reduced relative to the quality of seeds produced through outcross pollination Barrett , so these plants still benefit from mutualistic interactions with pollinators.

Mutualisms can also be characterized based on the degree of physical association that occurs between the species. Most plant-pollinator interactions are exhabitational because pollinators live separately from the plants they interact with. However, some pollinators live inside the plants they pollinate for a portion of their lives, which is an inhabitational relationship.

Characterizations of the most exclusive mutualistic interactions are correlated, in that inhabitational relationships also tend to be highly specific and obligate. However, exhabitational relationships are not necessarily facultative or diffuse. Pollination mutualisms can affect the outcomes of other kinds of species interactions.

Consider a simple example, with two animal-pollinated plant species and one animal pollinator species Figure 3. If the two plant species flower simultaneously, then they will compete with one another for pollination services. If the pollinator prefers one plant species over the other, then the preferred plant species has a competitive advantage over the second plant species.

Both of the plant species have a mutualistic relationship with the pollinator, but the relative fidelity of each mutualism affects the outcome of the competitive interaction between the two plant species. Most communities include many more flowering plants and animal pollinators than are represented in this example, resulting in a network of mutualistic interactions between plants and pollinators. Figure 3: Plant species competing for pollination services Visual representation of two plants species Plant species A and B competing for pollination services from a pollinator species.

Humans rely on insect pollinators for approximately one third of the food we eat, and a single species provides most of the necessary pollination services — the European honey bee Apis mellifera Klein et al. These insects are often considered to be an invasive species by ecologists because they have been broadly introduced by humans, and they are able to collect and utilize enormous quantities of floral resources Buchmann While biologists continue to search for solutions to the problems plaguing European honey bee colonies, pollination ecologists are also investigating the potential of wild bees to pollinate agricultural crops Richards Barrett, S.

Mating strategies in flowering plants: the outcrossing-selfing paradigm and beyond. Bascompte, J. Plant-animal mutualistic networks: the architecture of biodiversity.

Annual Review of Ecology, Evolution, and Systematics 38 , Bronstein, J. Our current understanding of mutualism. The Quarterly Review of Biology 69 , Buchmann, S. Competition between honey bees and native bees in the Sonoran Desert and global bee conservation issues. In The Conservation of Bees. Matheson, A.

San Diego: Academic Press, Cook, J. Mutualists with attitude: coevolving fig wasps and figs. Crepet, W. The fossil record of angiosperms: requiem or renaissance?

Annals of the Missouri Botanical Garden 95 , Darwin, C. On the Origin of species , 1st ed. Complete and Unabridged Reproduction. Gaskett, A. Orchid sexual deceit provokes ejaculation. The American Naturalist , EE Hu, S. Early steps of angiosperm-pollinator coevolution. Janzen, D. Coevolution of mutualism between ants and acacias in Central America. Evolution 20 , Klein, A. Importance of pollinators in changing landscapes for world crops. Proceedings of the Royal Society B.

Biological Sciences , Landry, C. Flower visitors to white mangrove: a comparison between three Bahamian islands and Florida. Buckner, S. Michener, C. The Bees of the World , 2 nd ed. Mitchell, R. Ecology and evolution of plant-pollinator interactions. Annals of Botany , , National Research Council. Status of Pollinators in North America. Pellmyr, O.