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United States Department of Agriculture

Agricultural Research Service

Research Project: Develop Stress-Resistant Dry Bean Germplasm and Sustainable Pest Management Strategies for Edible Legumes Title: Complex patterns of speciation in cosmopolitan "rock posy" lichens - an integrative approach to discovering and delimiting fungal species in the lichen-forming rhizoplaca melanophthalma speciescomplex

Authors
item Leavitt, Steven -
item Fankhauser, Johnathon -
item Leavitt, Dean -
item Porter, Lyndon
item Johnson, Leigh -
item St. Clair, Larry -

Submitted to: Molecular Phylogenetics and Evolution
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: March 17, 2011
Publication Date: May 12, 2011
Citation: Leavitt, S., Fankhauser, J., Leavitt, D., Porter, L., Johnson, L., St. Clair, L. 2011. Complex patterns of speciation in cosmopolitan "rock posy" lichens - an integrative approach to discovering and delimiting fungal species in the lichen-forming Rhizoplaca melanophthalma speciescomplex. Molecular Phylogenetics and Evolution. 59:587-602.

Interpretive Summary: Properly identifying the number of different species that make up a specific population can be challenging, especially when the individuals comprising the population may be very similar in physical appearance. The characteristics used to distinguish between species such as physical characteristics, chemistry and genetics can greatly influence the total number of species determined to comprise a population. Currently there are discrepancies regarding the total number of species that comprise the Rhizoplaca melanophthalma species complex. Rhizoplaca melanophthalma is a lichen consisting of a symbiotic relationship between a fungus and a cyanobacterium. The present study examined the lichen-forming fungi that comprise the Rhizoplaca melanophthalma species-complex. Combinations of fungal DNA, physical characteristics, and biochemistry determined that this species complex consists of ten prospective species, six of which were not previously recognized as species. We determined that physical characteristics were not the best indicator of species diversity. Our study of the R. melanophthalma complex indicates that the genus Rhizoplaca, as presently described, is more diverse in western North American than originally considered.

Technical Abstract: A growing body of evidence indicates that morphology-based species circumspection of lichenized ascomycetes greatly misrepresents the number of existing species. Recently it has been demonstrated that population-level processes operating within diverging populations can facilitate the identification of lineages in the early stages of species divergence. The cosmopolitan "rock posy" lichen (Rhizoplaca melanophthalma) species-complex includes a number of morphologically distinct species that are both geographically and ecologically widespread, providing a model system to evaluate speciation in lichen-forming ascomycetes. In this study, we assembled multiple lines of evidence from ribosomal and nuclear DNA sequence data, morphology, and biochemistry for species delimitation in the Rhizoplaca melanophthalma speciescomplex. Using multiple analytic approaches, we recover a total of ten candidate species in this study, four of which were previously recognized as distinct taxa and six previously unrecognized lineages found within what has been thus far considered a single species. Multiple instances of sympatry support the view that these lineages merit recognition as distinct taxa. Generally, we found little corroboration between morphological and chemical characters and previously unidentified lineages defined in this study, as most candidate species were morphologically polymorphic. However, secondary metabolite data supported one cryptic saxicolous lineage, characterized by orsellinicderived gyrophoric and lecanoric acids, which we consider to be taxonomically significant. Our study of the R. melanophthalma species-complex indicates that the genus Rhizoplaca, as presently circumscribed, is more diverse in western North American than originally perceived, and we present our analyses as a working example of species delimitation in morphologically cryptic and recently diverged lichenized fungi.

Last Modified: 11/28/2014