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Title: Resolution of paraphyly in caesalpinioid legumes
Author: Clark, Ruth P.
ISNI:       0000 0004 7971 7388
Awarding Body: Oxford Brookes University
Current Institution: Oxford Brookes University
Date of Award: 2017
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The exceptionally large, diverse, and economically important plant family Leguminosae has traditionally comprised three subfamilies, the Caesalpinioideae, Mimosoideae and Papilionoideae. Following a large-scale molecular based phylogenetic analysis in which subfamily Caesalpinioideae was demonstrated to be highly paraphyletic, the number of subfamilies recognised was increased to six, with four new subfamilies being segregated from within the Caesalpinioideae, and the Mimosoideae being subsumed into the redefined Caesalpinioideae (as the mimosoid clade). The Caesalpinioideae, and delimitation of genera therein, has therefore been a key focus of the international legume taxonomic community in recent years. Two of the largest genera in the Caesalpinioideae sensu traditional are Bauhinia and Caesalpinia; the former comprises part of the newly created subfamily Cercidoideae, whilst the latter is retained within the Caesalpinioideae sensu novo. Both Bauhinia and Caesalpinia have historically been most commonly treated as large, pantropical and polymorphic genera, but have in the light of molecular phylogenetic evidence been revealed to paraphyletic. A number of generic segregates have been consequently delineated from within each of them, but polymorphism has persisted, suggesting the existence of further paraphyly. The aim of this study is to address this remaining paraphyly, using a combined morphological, molecular and biogeographical approach to investigate generic limits and define segregate genera. The work herein creates a new segregate genus from within Bauhinia s.l., based upon morphological, molecular, palynological, and biogeographical evidence. Details of the composition of two further generic segregates of Bauhinia s.l. are presented, their geographical distributions described, and the relevance of this to the generic limits explored. The status of the putative segregate genus Lasiobema is examined, with novel data on a poorly known species of the genus presented. The monophyly of Mezoneuron, a segregate genus of Caesalpinia s.l., is demonstrated with morphological and molecular data, and infrageneric relationships are explained. Preliminary findings reconstructing the evolutionary and biogeographical history of the genus are discussed. This study represents substantial progress towards resolving generic limits within two of the major groups of the Caesalpinioideae (sensu traditional), and provides data upon which further such studies can be built, setting the framework for identification and resolution of the remaining paraphyly.
Supervisor: Lack, Andrew Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral