Early evolution of bee/angiosperm relationships

Bees and angiosperms have had an intimate and ancient relationship at least since the Cretaceous. Bees are currently the most important pollinators of many angiosperms, and bees rely exclusively on angiosperms for adult and larval nutrition. Animal pollination in general has been hypothesized to be a significant factor promoting angiosperm diversification. In spite of the obvious relationship between bees and flowering plants, and the potential significance of bee pollination on flowering plant diversity, the historical interactions between bees and angiosperms in the earliest stages of bee evolution have not been investigated in detail. This is primarily because the bee fossil record is fragmentary (making accurate dating of bee origins difficult), and the higher level phylogenetic relationships within bees have not been well established. Our project has three main objectives:

photo credit Bryan Danforth

(1) We are reconstructing the phylogeny for the primitive (short-tongued) bee families, subfamilies, and tribes, and to establish the relationships of the long-tongued bee clade to the short-tongued bees. We will combine both morphological data, and molecular data from three slowly evolving, single copy nuclear genes: EF-1, wingless, and PEPCK. All three genes have shown promise for recovering Mesozoic age divergences in insects.

(2) Using recently developed methods for estimating the ages of lineages from DNA sequence data, we will estimate the date of bee origin as well as important nodes in the phylogeny of the bees (ages of families, age of long-tongued bee clade, time of major radiation events, etc).

(3) We will relate the time of origin of the bees and major events in bee evolution to temporal patterns of angiosperm evolution (as determined by the angiosperm fossil record and current phylogenetic estimates of angiosperm relationships). Using such estimates we will address questions related to the temporal patterns of bee and angiosperm diversification. For example, the radiation of bees has often been correlated with the appearance of "bee syndrome" floral characters such as tubular corollas, bilateral symmetry, and hidden nectaries. However, we predict that these characters are more likely to be associated with the radiation of certain derived members of the long-tongued bee clade, rather than earlier radiations of short-tongued bee lineages.

Collaborators:

Bryan N. Danforth, Dept. of Entomology, Cornell University, Ithaca NY.

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