Studies in panellus stypticus and the genus panellus complex

Author

Jiankang Jin

Date of Award

5-2000

Degree Type

Dissertation

Degree Name

Doctor of Philosophy

Major

Botany

Major Professor

Karen W. Hughes

Committee Members

Robert Trigiano, Sally Horn

Abstract

This research examined the biogeography, phylogeny and speciation processes within Panellus stypticus, and tried to resolve the systematics of the Panellus complex that includes Panellus stypticus, P. mitis, P. serotinus (Sarcomyxa serotina), P. ringens, P. violaceofulvus, Tectella patellaris (P. patellaris), P. pusillus (Dictyopanus pusillus) and Pleurotopsis longinqua (P. longinquus). Exemplars of those eight species and geographically diverse collections of P. stypticus were examined using isozyme analyses, morphological comparison, mating studies and molecular analyses. In the Panellus complex, circumscription based on morphological characters was not well defined. Species in the complex were well separated and unique species characters made this complex morphologically diverse. Based on morphological and molecular analyses, circumscription of the genus Panellus included P. stypticus and D. pusillus only, with other species in the complex assigned to separate genera. Probably additional intersterility groups exist within poroid Dictyopanus. Under this concept, the genus Panellus was defined morphologically by a panelloid stature, a lateral stipitate pileus and smooth amyloid spores. I propose that the following five genera be used to describe this complex: Panellus for the Panellus stypticus - Dictyopanus pusillus clade, Pleurotopsis for the Pleurotopsis longinqua - P. ringens clade, Tectella for Tectella patellaris, Sarcomyxa for P. serotinus and a new genus status for P. mitis. Thus, some species in this study should be named as follows: Panellus pusillus for D. pusillus; Sarcomyxa serotina for P. serotinus; Pleurotopsis ringens for Panellus ringens; and Pleurotopsis longinqua for Panellus longinquus. However, the designation of Panellus violaceofulvus to Pleurotopsis violaceofulvum needs further verification. Within Panellus stypticus, Eastern and Pacific North American regions were clearly differentiated from each other based on the distribution of extracellular laccase (ECLl), esterase (ESTl-1) and alcohol dehydrogenase (ADH3) alleles. A connection between Pacific North America, Asia and Europe may be inferred based on the presence of the ADH3 allele in these populations. The distribution of ECL and EST alleles did not clearly separate Northern and Southern Hemisphere populations. A bimodal distribution for ECL alleles in Oceanian areas suggests local differentiation within this region. In this species, mating studies made clear that there is single intersterility group in this species though antagonistic reactions were observed between Northern Hemisphere collections and Southern Hemisphere collections, and within Oceanian collections. Spore shape and the ratio between spore length and width remained as stable and conserved characters in this species; however, many characters such as lamella height and spore size were differentiated among five geographical areas, even between neighboring areas. More diversity including basidioma general stature and lamella anastomoses was observed in Oceanian areas for those characters. In Panellus stypticus, RFLP data revealed that there were seven geographical areas (populations). Sequence data for the ITS region and for the group I intron supported a separation of Northern and Southern Hemisphere populations with the New South Wales population being most closely related to Northern Hemisphere populations. Among Northern Hemisphere populations, Eastern North America was clearly unique, separated from both Eurasian and the Pacific Northwest populations. In Panellus stypticus, RFLP data do not show gene flow between geographical regions. Based on ITS sequences, it is more likely that Northern Hemisphere collections were ancestral to the Southern Hemisphere collections. Tasmanian and New Zealand collections were believed to be from Australian continent. In North America, these studies suggested that allopatry produced by the Rocky Mountains may have played an important role in the early evolution and differentiation of the species. Within the Northern Hemisphere, Eurasia or Eastern North America is the possible center of origin. The time frame for evolution and dispersal for the species is discussed.