MSA - Systematics/Evolution
Jenkinson, Thomas S. , Wannathes, Nopparat , Tan, Yee-Shin , Perry, Brian A. , Desjardin, Dennis E. .
Phylogenetic relationships within the genus Marasmius sensu stricto inferred from two ribosomal encoding loci.
Current infrageneric classifications of Marasmius based on cellular morphology and histological architecture are historically controversial. While several molecular studies have demonstrated that fungal genera based on homoplastic morphological characters are artificial in the phylogenetic sense, the degree of infrageneric paraphyly within the genus Marasmius has never been appropriately addressed. Previous studies addressing the monophyly of infrageneric circumscription in this large genus based on a single rapidly evolving locus have fallen short due to apparent mutational saturation. We present the first study examining phylogenetic relationships within the genus Marasmius sensu stricto based on two loci known to be evolving at significantly different rates with high probability of phylogenetic resolution. Two ribosomal-RNA encoding loci (ITS and nuLSU) were sequenced from approximately one-tenth of the described biodiversity of Marasmius sensu stricto worldwide, including representatives of all current subgeneric divisions. Molecular sequence data were evaluated using multiple phylogenetic approaches, with members of the genus Crinipellis as outgroup taxa. Preliminary results show that the current infrageneric classifications are paraphyletic, with members of sections Sicci and Globulares interspersed within one lineage. Pilipellis anatomy in species of Marasmius appear to have convergently evolved, and do not represent a phylogenetically informative character. Members of section Marasmius fall into polyphyletic clades indicating multiple evolutionary origins of the collarium in this genus. By plotting morphological characters used in taxonomic delimitation on this phylogenetic hypothesis, we begin to assess the evolutionary plasticity of the characters currently used to circumscribe infrageneric groupings, and determine suitable morphological characters to inform classification. This study is presented to stimulate discussion on the reevaluation of current subgeneric circumscriptions within the genus Marasmius.
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1 - San Francisco State University, Department of Biology, 1600 Holloway Ave., San Francisco, CA, 94132, USA
2 - Chiang Mai University, Department of Biology, Faculty of Science, Chiang Mai, 50200, Thailand
3 - University of Malaya, Institute of Biological Sciences, Faculty of Sciences, Kuala Lumpur, 50603, Malaysia
Presentation Type: Poster:Posters for Topics
Location: Event Tent/Cliff Lodge
Date: Tuesday, July 28th, 2009
Time: 5:30 PM