WP4

WP4: Global Change, functional traits and phylogeography

15 researchers

COORDINATORS Claudine Ah-Peng (Botany Department, University of Cape Town), Kristal Tolley ( South African National Biodiversity Institute, Cape Town ) and Dominique Strasberg (UMR C53, University of La Réunion)

Project 1: Dynamics of biodiversity in Southern African ecosystems and sustainable use in the context of global change: processes and mechanisms involved.

Participants: Dominique Strasberg, Erwann Lagabrielle (Université de la Réunion), Claudine Ah-Peng (University of Réunion / University of Cape Town), Mathieu Rouget (South African National Biodiversity Institute, University of Pretoria), Ian MacDonald, Terry Hedderson (University of Cape Town), Dave Richardson (University of Stellenbosch), Richard Cowling (Nelson Mandela Metropolitan University, Port-Elizabeth)

  In the global and regional context of biodiversity loss, our aim is to identify both processes that maintain biodiversity and the role of threats affecting biodiversity. We focus on understanding ecological and historical factors that explain species diversity in plant communities integrating new phylogenetics and biogeography concepts. One main issue is to explain species richness variation across latitude and altitude.

At the ecosystem level and island scale, we still poorly understand the consequences of biological invasions, habitat transformation and climate change on biodiversity. In combining GIS tools, distribution database and plant traits, we aim at predicting changes in species distribution and identifying priority areas for conservation.

Project 2 : Can lizards beat the heat? Thermal optima, niche, performance and adaptation to a changing environment

Participants: Anthony Herrel (MNHN, Paris), Krystal Tolley, John Measey, Danni Guo (South African National Biodiversity Institute, Cape Town)

We seek to make detailed measures of morphological adaptations and their ecologically related performance traits in a selected southern African lizards in order to explain their evolutionary radiations. This will be combined with detailed measures of ecologically related field data (niche requirements, physiology and performance) as well as estimates of gene flow obtained with molecular methods, to assess dispersal capability. This information will be used to construct accurate Species Distribution Models (SDMs), under different climatic scenarios).

Small changes in morphology can result in significant changes in performance which could help explain the radiation of species into different habitats in southern Africa. Combining field measurements in South Africa with detailed investigations using equipment in the Muséum National d’Histoire Naturelle, Paris will quantify how the morphology is expressed in terms of biomechanics and performance. These results will be combined with ongoing molecular studies to precise both mode and tempo of evolutionary radiations in southern African lizards, and the rates of gene flow. This project would represent a major advance in our understanding of how climate change affects species communities using a multi-disciplinary approach to build the next generation of SDMs incorporating physiological, niche data and molecular information.

Project 3: Colonisation, speciation and community assemblages of bryophytes in islands

Participants: Claudine Ah-Peng (University of Cape Town/ University of Réunion), Nicholas Wilding (University of Cape Town), Terry Hedderson (University of Cape Town), Dominique Strasberg (University of Réunion)

While living resources and biodiversity are irreversibly vanishing at the global scale, we remain unable to explain species diversity patterns or to propose hypotheses on key factors that underlie the origination of biological diversity. This proposal aims at understanding the geographic pattern of gene flow between populations of bryophytes on islands in the West Indian Ocean and to determine the timeline and tempo of colonisation of the volcanic islands. The system provides an ideal evolutionary laboratory within which processes affecting the accumulation of biodiversity can be assessed.

Given current global environmental change, the dispersal ability of living organisms is a key process in understanding the maintenance and diversification of organisms. Especially in small territories like islands, the possibility of extending or changing of geographical distribution is limited. High diversity areas may originate from two mechanisms: species accumulation ie sink-source effects or species diversification following a colonisation event.

This project aims at conducting research on phylogeography and processes of diversification within a major group of early land plant lineages (bryophytes) in a hot spot of biodiversity. This project will focus on: (i) understanding the geographic pattern of gene flow between populations of bryophytes in the West Indian Ocean area, (ii) determining the timeline and tempo of colonization of the volcanic islands, (iii) reconstructing phylogenetic relationships of key bryophyte groups.

Project 4 : Niche evolution and the assembly of tropical bryophyte communities along an elevational gradient

Participants: Claudine Ah-Peng (University of Cape Town/University of Réunion) , Jasper Slingsby (SEON), Terry Hedderson (University of Cape Town), Dominique Strasberg (University of Réunion)

The maintenance of high species diversity in a community requires mechanisms by which the species may co-exist. Two current theories for the maintenance of high diversity are that the interactions between species are negligible, diversity being dependent on dispersal processes alone, or that competition is minimized by each species having specialized habitat preferences segregated along environmental niche axes. Recent studies have demonstrated niche specialization and segregation indirectly by identifying structured patterns of functional similarity and phylogenetic relatedness among species within and between communities.

The aim of this project is to examine the importance of niche specialization as a determinant of the diversity of bryophyte (Bryophyta and Marchantiophyta) assemblages along an elevational gradient on the Piton des Neiges volcano, Réunion. 

Pix: Piton des Neiges volcano (C. Ah-Peng)

Changes in elevation are often strongly correlated with changes in climatic variables such as temperature and rainfall, and thus provide a useful niche axis for the investigation of habitat specialization. Species were sampled from corticolous, terricolous, epiphyllous, lignicolous and rupicolous habitats at each elevation, allowing identification of niche segregation between habitats within elevational zones. Firstly, we want to test if species are specialized to particular elevational zones and habitat types. If this is the case we want to examine the pattern of niche evolution and test whether habitat preference has evolved in a conservative manner. We will then test whether communities are phylogenetically structured, providing evidence for the influence of competition or habitat filtering. Finally we will examine patterns of phylogenetic turnover along the elevational gradient and between habitat types in an attempt to identify thresholds along niche axes which limit the occurrence of particular lineages.

We aim to develop a dated phylogenetic hypothesis for all species in the study based on molecular sequence data. This will allow us to explicitly examine niche evolution and test if niche preference has evolved in a conservative manner; to test whether communities are phylogenetically structured, and thus influenced by competition or habitat filtering; and to examine patterns of phylogenetic turnover along the elevational gradient and between habitat types.