 | Shefferson, R.P., C.C. Cowden, M.K. McCormick, T. Yukawa, Y. Ogura-Tsujita, | |
| and T. Hashimoto. 2010. Evolution of host breadth in broad interactions: mycorrhizal specificity in East Asian and North American rattlesnake plantains (Goodyera spp.) and their fungal hosts. Molecular Ecology 19:3008-3017. |
Abstract Host breadth is often assumed to have no evolutionary significance in broad
interactions because of the lack of cophylogenetic patterns between interacting
species. Nonetheless, the breadth and suite of hosts utilized by one species may
have adaptive value, particularly if it underlies a common ecological niche among
hosts. Here, we present a preliminary assessment of the evolution of mycorrhizal
specificity in 12 closely related orchid species (genera Goodyera and Hetaeria) using
DNA-based methods. We mapped specificity onto a plant phylogeny that we
estimated to infer the evolutionary history of the mycorrhiza from the plant perspective,
and hypothesized that phylogeny would explain a significant portion of the variance in
specificity of plants on their host fungi. Sampled plants overwhelmingly associated
with genus Ceratobasidium, but also occasionally with some ascomycetes. Ancestral
mycorrhizal specificity was narrow in the orchids, and broadened rarely as Goodyera
speciated. Statistical tests of phylogenetic inertia suggested some support for
specificity varying with increasing phylogenetic distance, though only when the
phylogenetic distance between suites of fungi interacting with each plant taxon were
taken into account. These patterns suggest a role for phylogenetic conservatism in
maintaining suits of fungal hosts among plants. We stress the evolutionary
importance of host breadth in these organisms, and suggest that even generalists
are likely to be constrained evolutionarily to maintaining associations with their
symbionts.
Copyright 2010 Richard P. Shefferson. All rights reserved.
Shefferson et al 2010
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