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Abstract Detail

MSA Presidential Address

Musings on what types of non-molecular characters are concordant with molecular phylogenies in Agaricomycetes and why so few are synapomorphic.

The lecture will begin with my collaborative adventures in surveying basidiomycete fungi in the Caribbean Basin and the US Great Smoky Mountain National Park. Collections of Hygrophoraceae from these expeditions plus those from collaborators around the world were analyzed molecularly and morphologically for a higher-level revision of the family (Lodge & 33 others, 2013). Sharon Cantrell and I selected at least one basal and one distal species per clade for analyses to determine if the characters used to define genera and subgenera occurred throughout the group. Biotrophic lifestyles (e.g., ectomycorrhiza-formation in Hygrophorus, lichen-formation in Lichenomophalia) likely represent adaptive radiations, the traits were found throughout the lineages including basal species and were synapomorphic (no reversions), which is typical in ectomycorrhizal lineages. Not all novel symbioses, however, originate at the base of a taxonomic group (e.g., basal Amanita species are non-mycorrhizal). Several pigments were concordant with lineages inferred from molecular phylogenies (betalains and carotinoids). The multi-step synthesis pathways responsible for pigment formation cannot be readily altered to produce unrelated pigment types, and several pigments and bioactive non-pigmented compounds have demonstrated antimicrobial properties and are thus likely adaptive. Labile adaptive traits, however, such as macromorphology (fruitbody types), have been shown by Hibbett and others to have evolved multiple times in different lineages, either independently through convergence or via reversion to an ancestral state. In contrast, micromorphological traits of lamellar trama and hymenial types in Hygrophoraceae are completely or nearly concordant with molecular phylogenies, though reversion to ancestral states is sometimes observed; such traits might be morphogenetically conservative rather than conserved through selection. Traits can become fixed via stochastic events such as founder effects and genetic drift rather than from selection pressure. It appears there are two general classes of phylogenetically informative non-molecular traits: 1. adaptive traits that are complex so they rarely arise de novo, and 2. micromorphological traits that might be adaptive but are possibly retained in developmental pathways by stochastic events or inertia. There is no particular reason why these traits, especially the latter ones, should initially coincide with the point of divergence of a clade, which may help explain why synapomorphies that are completely concordant with taxonomic groups are infrequent. An adaptive trait that gives rise to an adaptive radiation might coincide with the point of divergence over time if species basal to it lacking the adaptive trait are differentially lost through selection pressure, increasing their frequency.

1 - Center for Forest Mycology Research, PO Box 1377, Luquillo, PR, 00773-1377, USA

Keywords:
Evolution
systematics
Hygrophoraceae
molecular phylogeny
morphology.

Presentation Type: Special Presentation
Session: S02
Location: Salon 8/The Shaw Conference Centre
Date: Monday, July 27th, 2015
Time: 8:00 AM
Number: S02001
Abstract ID:1120
Candidate for Awards:None