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Abstract Detail

Bryological and Lichenological Section/ABLS

Lucking, Robert [1], Dal-Forno, Manuela [2], Lawrey, James [2].

Last but not least: Witnessing the 'birth' of lichenization in the Basidiomycota.

The known species of Ascomycota outnumber those of Basidiomycota by a ratio of roughly 2:1, which results in higher estimates of diversification rates in the Ascomycota, since both phyla are sister groups. One could therefore assume that the higher species richness of Ascomycota is one reason why this phylum includes more lichenized species, but the number of lichenized Ascomycota outnumbers lichenized Basidiomycota by a much higher ratio of about 300:1. Here we present a relaxed molecular clock dating study of higher Fungi focusing on lichenized clades, with the aim to compare diversification rates of lichenized Ascomycota and Basidiomycota. We used a selection of 154 taxa plus one species of Glomus as outgroup. Sequences of the 28S nuclear large subunit rDNA (nuLSU) were downloaded from GenBank and assembled in BioEdit 7.09. A relaxed, uncorrelated lognormal molecular clock model was employed to date the evolutionary origin of stem and crown nodes of major lineages in BEAST 1.6.1. The basal ingroup node was calibrated at 550 mya, following recent studies estimation for the split of Ascomycota-Basidiomycota. We used the R package GEIGER 1.3.1 to estimate gross and net diversification rates, measured in species per million years, based on node age estimates and estimates of species richness for nine lichenized clades present in the dataset: Arthoniales, Lecanoromycetes, Pyrenulales, Trypetheliales, and Verrucariales (Ascomycota), as well as Dictyonema, Lepidostroma, Lichenomphalia, and Multiclavula (Basidiomycota). We found no significant difference between diversification rates when grouped according to phylum, regardless of the assumptions of the model. However, we found a significant positive correlation between diversification rates and node ages, suggesting that phylogenetically younger clades tend to have higher diversification rates, even if the number of species is substantially lower than in phylogenetically older clades. Four of the five phylogenetically youngest lichenized clades are in the Basidiomycota; two of these, Multiclavula (crown age 7 mya) and Dictyonema (crown age 41 mya) are substantially younger than all other lichenized clades. We argue that their high diversification rates represent a geologically recent 'birth' of lichenization in Basidiomycota compared with Ascomycota, and provide a snapshot of the conditions under which lichen diversification might have taken place in ancient Ascomycota, specifically the largest lichenized class Lecanoromycetes.

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1 - Field Museum of Natural History, Department of Botany, 1400 South Lake Shore Drive, Chicago, IL, 60605-2496, USA
2 - George Mason University, Environmental Science and Policy MSN 5F2 , 4400 University Drive, Fairfax, VA, 22030-4444, USA

molecular dating

Presentation Type: Poster:Posters for Sections
Session: P
Location: Grand Salon A - D/Riverside Hilton
Date: Monday, July 29th, 2013
Time: 5:30 PM
Number: PBR005
Abstract ID:777
Candidate for Awards:None

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