title: Diversification and coevolution in brood pollination mutualisms: Windows into the role of biotic interactions in generating biological diversity.
abstract: Brood pollination mutualisms-interactions in which specialized insects are both the pollinators (as adults) and seed predators (as larvae) of their host plants-have been influential study systems for coevolutionary biology. These mutualisms include those between figs and fig wasps, yuccas and yucca moths, leafflowers and leafflower moths, globeflowers and globeflower flies, Silene plants and Hadena and Perizoma moths, saxifrages and Greya moths, and senita cacti and senita moths. The high reciprocal diversity and species-specificity of some of these mutualisms have been cited as evidence that coevolution between plants and pollinators drives their mutual diversification. However, the mechanisms by which these mutualisms diversify have received less attention. In this paper, we review key hypotheses about how these mutualisms diversify and what role coevolution between plants and pollinators may play in this process. We find that most species-rich brood pollination mutualisms show significant phylogenetic congruence at high taxonomic scales, but there is limited evidence for the processes of both cospeciation and duplication, and there are no unambiguous examples known of strict-sense contemporaneous cospeciation. Allopatric speciation appears important across multiple systems, particularly in the insects. Host-shifts appear to be common, and widespread host-shifts by pollinators may displace other pollinator lineages. There is relatively little evidence for a "coevolution through cospeciation" model or that coevolution promotes speciation in these systems. Although we have made great progress in understanding the mechanisms by which brood pollination mutualisms diversify, many opportunities remain to use these intriguing symbioses to understand the role of biotic interactions in generating biological diversity.
authors.affiliation: Department of Ecology and Evolutionary Biology, University of Arizona, P. O. Box 210088, Tucson, Arizona 85721 USA hembry@email.arizona.edu.
authors.forename: David H
authors.initials: DH
authors.lastname: Hembry
authors.affiliation: Department of Biology, Syracuse University, 107 College Place, Syracuse, New York, 13244 USA.
authors.forename: David M
authors.initials: DM
authors.lastname: Althoff
mesh_terms: D000818:Animals; D044822:Biodiversity; D007313:Insecta / Q000254:growth & development / Q000502:physiology*; D007814:Larva / Q000254:growth & development / Q000502:physiology; D019684:Magnoliopsida / Q000502:physiology*; D054817:Pollination; D013045:Species Specificity; D013559:Symbiosis
keywords: Ficus; Phyllanthus; Yucca; brood pollination; coevolutionary diversification; obligate pollination mutualism; pollinating seed parasite; seed predator; speciation