Patterns of diversity in the tribe meliceae (gramineae: pooideae)

Mejia Saulés, Maria Teresa (1999) Patterns of diversity in the tribe meliceae (gramineae: pooideae). University of Southampton, Doctoral Thesis.

Abstract

The tribe Meliceae is a group of grasses of temperate regions that is widely distributed around the world, except in Australia and Antarctica. I considered two hypotheses: the 'Minimal hypothesis' which includes 8 genera (Anthochloa, Glyceria, Lycochloa, Melica, Pleuropogon, Schizachne, Streblochaete and Triniochloa) and the 'Maximal hypothesis' which includes the 8 genera listed before plus Briza, Brylkinia, Catabrosa and Neostapfia.

Melica is one of the largest genera within the tribe, with approximately 84 species and several authors consider Bromelica genus as a segregate of Melica.

The objectives for this study were 1) to examine in more detail the patterns of diversity in and around the Meliceae and to resolve the uncertainties in definition of the tribe and 2) circumscribing and/or subdividing the largest genus Melica.

To resolve these uncertainties detailed surveys were carried out for morphology (including 62 characters from vegetative and floral parts of the plant) and anatomy (including 24 characters from the lemma epidermis and 39 characters from the leaf-epidermis and transverse section of the leaf). The surveys provided a better characterisation of the variation and a firmer basis from which to examine the phylogeny in the tribe and in the Melica genus. The first steps towards a molecular analysis are described as well.

My results from phenetic and cladistic analyses support rejection of the minimal and maximal hypotheses. A new taxonomic delimitation in the Meliceae tribe is proposed with 9 genera: Anthochloa, Catabrosa, Glyceria, Pleuropogon, Melica, Lycochloa, Schizachne, Streblochaete and Triniochloa. The inclusion of Briza within this delimitation remains controversial. Cladistic analyses showed Meliceae as a monophyletic group. A monophyletic group including Anthochloa, Catabrosa, Glyceria, Pleuropogon and probably Briza corresponds to a possible Glyceriinae clade.

The simple segregation of Bromelica from Melica to form two genera is rejected. Melica is not a coherent taxonomic grouping. It appears to be a polyphyletic group.

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