Doctoral Dissertations

A. David Sime

Date of Award

12-2000

Degree Type

Dissertation

Degree Name

Doctor of Philosophy

Major

Botany

Major Professor

Ronald H. Petersen

Committee Members

Mark Windham, David K. Smith, Robert Trigiano

Abstract

The genus Melanotus represents a heterogeneous assemblage of brown to purple-brown-spored pleurotoid mushrooms that are either lignicolous or graminicolous, and which exhibit a primarily amphi-mesothermal, temperate forest distribution with a secondarily circumtropical range distribution. In traditional literature, systematics of the genus were based primarily on macro- and micromorphological characters of basidiomata. Reliance on a relatively small set of morphological characters in the circumscription of taxa within Melanotus has resulted in a species concept that does not reflect genetically similar units.

In order to develop a better understanding of the genetic relationships within Melanotus, this study has: 1) re-examined traditional morphological characters; 2) analyzed previously unexamined morphological characters; 3) determined the mating systems operating within and between selected taxa; 4) identified discrete intersterility groups; 5) incorporated the use of an arbitrary PCR fingerprinting technique (DAF) to discriminate among and between selected taxa; and 6) included examination of type specimens in order to determine the correct application of names.

A phenetic analysis of the morphological data indicates that the circumscription of morphological variation within Melanotus is limited to a few previously unreported macro- and micromorphological characteristics. Most morphological characters traditionally used to segregate infrageneric taxa into discrete units were found to significantly overlap. The application of a singular morphospecies concept alone is not advocated within Melanotus.

Mating systems were determined for 23 collections within Melanotus, revealing a mixture of mating systems. Three intersterility groups to which names could be applied were identified. The use of a biological species concept in the systematics of the genus Melanotus is considered taxonomically informative, and advocated.

DNA-amplification fingerprinting data confirm that taxa within Melanotus appear to be separable based on; 1) placement within a common intersterility group; and to a lesser degree; 2) geographic proximity of collections; and 3) substratum preference. The use of DAT may be of limited value in the interspecific taxonomy of the genus, and is recommended only for placement of isolates that have been previously identified using a biological species concept. The results of this study indicate that only through the use of multiple data sets (i.e., morphology, mating, molecular) can natural groups W\X\v\n Melanotus be identified. Several names previously used within these identified natural groups of Melanotus are considered synonyms of the priorable names within two groups: M. alpiniae and M. horizontal!s, while collections of M. defraudatus also appear to represent a natural group.

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