Informations et ressources scientifiques
sur le développement des zones arides et semi-arides

Accueil du site → Doctorat → Royaume-Uni → 2022 → The evolution, ecology and conservation of Conophytum N.E.Br. (Aizoaceae) – a diverse genus of dwarf succulent plants in an arid biodiversity hotspot in southern Africa

Liverpool John Moores University. (2022)

The evolution, ecology and conservation of Conophytum N.E.Br. (Aizoaceae) – a diverse genus of dwarf succulent plants in an arid biodiversity hotspot in southern Africa

Bentley, L

Titre : The evolution, ecology and conservation of Conophytum N.E.Br. (Aizoaceae) – a diverse genus of dwarf succulent plants in an arid biodiversity hotspot in southern Africa

Auteur : Bentley, L

Etablissement de soutenance : Liverpool John Moores University.

Grade : Doctor of Philosophy (PhD) 2022

Résumé partiel
Conophytum N.E.Br. (Aizoaceae) is a genus of dwarf succulent plants endemic to western South Africa and southern Namibia. It is highly diverse, with 106 constituent species and is considered a model genus for the Succulent Karoo Biome, an arid region with uniquely high desiccation-tolerant (succulent) plant diversity, based on its variety of distribution types and growth forms. The aim of this project was twofold : to provide a clearer understanding of the patterns and drivers of speciation in the genus, and to identify conservation strategies that maximise the likely survival of these species, based on spatial ecological analyses of their current distributions. The biodiversity of the Succulent Karoo biome is increasingly vulnerable to a multitude of threats, mostly as a consequence of growing levels of human activity. The current and future conservation of Conophytum is dependent on evidence-based interventions that, in particular, help mitigate the effects of a changing climate and illegal collecting. First, an updated phylogeny was produced providing the foundation to many of the analyses undertaken in this thesis, beginning with an assessment of the drivers of diversification. For the first time, nuclear gene regions and sequences from almost all species in the genus (102 of 106) were included in the development of phylogenetic hypotheses. From there, a selection of 12 pertinent characters was mapped over the phylogeny and phylogenetic signal was calculated in a univariate and multivariate manner. This, along with correlations in character evolution, was used to infer potential drivers of diversification. Nocturnal flowering was found to characterise certain clades and was correlated with pollen type D and flower structure A2, suggesting an influence of pollinator specialisation on evolution, while windowed leaves characterised one particularly large, strongly supported clade in the phylogeny, and, through correlated evolution with other traits such as the presence of bladder cells, suggested a key influence of the abiotic environment in this clade’s formation. This abiotic influence on speciation was further investigated using spatial environmental data to determine differences in the abiotic preferences of individual Conophytum species and five large, strongly supported clades in the phylogeny. Geological, topographical and climatic variables were mapped onto the phylogeny, while differences in clade and species’ environmental preferences were assessed. Associations between environmental variables and the evolution of certain traits were also analysed.

Présentation

Version intégrale (364 Mb)

Page publiée le 19 janvier 2023