Browsing by Subject "molecular phylogenetics"

Now showing 1 - 3 of 3

Open Access
Guyanagaster, a New Wood-Decaying Sequestrate Fungal Genus Related to Armillaria (Physalacriaceae, Agaricales, Basidiomycota)
(2010) Henkel, TW; Smith, ME; Aime, MC
Premise of the study : Sequestrate basidiomycete fungi (e. g. "gasteromycetes") have foregone ballistospory and evolved alternative, often elaborate mechanisms of basidiospore dispersal with highly altered basidioma morphology. Sequestrate fungi have independently evolved in numerous Agaricomycete lineages, confounding taxonomic arrangements of these fungi for decades. Understanding the multiple origins and taxonomic affinities of sequestrate fungi provides insight into the evolutionary forces that can drastically alter basidioma morphology. In the neotropical rainforests of the Guiana Shield, we encountered a remarkable sequestrate fungus fruiting directly on decaying hardwood roots. The fungus 'singular combination of traits include a wood-decaying habit; black, verrucose peridium; reduced stipe; and gelatinized basidiospore mass. Methods : Guyanagaster necrorhiza gen. et sp. nov. is described. Macro-and micromorphological characters were assessed and compared to most similar taxa. To determine the phylogenetic affinities of the fungus, DNA sequence data were obtained for the 18S, ITS, and 28S rDNA, RBP2, and EF1 alpha regions and subjected to single-and multi-gene analyses. DNA sequences from fungal vegetative organs growing on decaying woody roots confirmed the wood-inhabiting lifestyle of Guyanagaster. Key results : Guyanagaster is morphologically unique among sequestrate fungi worldwide. Phylogenetic evidence places Guyanagaster in close relation to the wood-decaying mushroom genus Armillaria in the Physalacriaceae (Agaricales, Agaricomycetes, Basidiomycota). Conclusions : Guyanagaster represents an independently evolved sequestrate form within the Physalacriaceae. Although molecular data confirm that Guyanagaster is closely related to Armillaria, the unusual features of this fungus suggest a case of radically divergent morphological evolution.
Open Access
Systematics of the Lichen Family Verrucariaceae and Evolution of the Rock-inhabiting Habit within a Group of Ecologically Diverse Fungi (Chaetothyriomycetidae, Ascomycota)
(2007-12-04) Gueidan, Cecile
Verrucariaceae are a family including mostly lichenized species (Verrucariales, Ascomycota). Its current generic classification, which mainly relies on three morphological characters (spore septation, thallus structure, and hymenial algae), has never been subjected to molecular data. Because these characters were suspected to be homoplastic, the monophyly of the genera as currently delimited based on morphology need to be assessed. A three-gene phylogenetic analysis was carried out using three methods (Maximum Parsimony, Maximum Likelihood, and a Bayesian approach) on 83 taxa, selected from 15 genera in Verrucariaceae. Ancestral state reconstructions were undertaken for four characters (spore septation, thallus structure, hymenial algae, and upper cortex structure). The results confirmed that most of the genera were not monophyletic, and that the most recent common ancestor of Verrucariaceae was most likely crustose, lacking hymenial algae, and with simple spores and a pseudocortex. The use of symplesiomorphic traits to define Verrucaria, the largest and type genus for the Verrucariaceae, as well as the non monophyly of the genera Polyblastia, Staurothele and Thelidium, explain most of the discrepancies between the current classification and a classification using monophyly as a grouping criterion. In order to accommodate newly inferred monophyletic groups, existing genera were re-delimited and three new genera were proposed. Recent broad-scale phylogenetic analyses have shown that Verrucariales was sister to Chaetothyriales, an order first known as including mostly saprophytes and opportunistic animal and human parasites. Investigations of fungal communities colonizing rocks in extreme environments have shown that some slow-growing melanized fungi inhabiting bare rock surfaces belonged to the Chaetothyriales. Multigene phylogenetic analyses were carried out using Maximum Likelihood and a Bayesian approach in order to confirm the affiliation of 25 of these rock isolates. Ancestral state reconstructions were then undertaken on two different datasets to look at the evolutionary history of lichenization within Pezizomycotina, and the rock-inhabiting habit within Eurotiomycetes. Results suggest that the ancestor of the lineage including Verrucariales and Chaetothyriales was likely to be an extremotolerant non-lichenized, rock-inhabiting fungus. Virulence factors of opportunistic parasites within Chaetothyriales, such as melanization and meristematic growth, might have primary been adaptations for life in extreme habitats.
Open Access
Toward a monophyletic Notholaena (Pteridaceae): Resolving patterns of evolutionary convergence in xeric-adapted ferns
(Taxon, 2008-01-01) Rothfels, CJ; Windham, MD; Grusz, AL; Gastony, GJ; Pryer, KM
Cheilanthoid ferns (Pteridaceae) are a diverse and ecologically important clade, unusual among ferns for their ability to colonize and diversify within xeric habitats. These extreme habitats are thought to drive the extensive evolutionary convergence, and thus morphological homoplasy, that has long thwarted a natural classification of cheilanthoid ferns. Here we present the first multigene phylogeny to focus on taxa traditionally assigned to the large genus Notholaena. New World taxa (Notholaena sensu Tryon) are only distantly related to species occurring in the Old World (Notholaena sensu Pichi Sermolli). The circumscription of Notholaena adopted in recent American floras is shown to be paraphyletic, with species usually assigned to Cheilanthes and Cheiloplecton nested within it. The position of Cheiloplecton is particularly surprising - given its well-developed false indusium and non-farinose blade, it is morphologically anomalous within the "notholaenoids". In addition to clarifying natural relationships, the phylogenetic hypothesis presented here helps to resolve outstanding nomenclatural issues and provides a basis for examining character evolution within this diverse, desert-adapted clade.