Contrasting evolutionary patterns between Mediterranean floristic regions
Wilkinson supervised by Dr Pablo Vargas
Royal Botanic Garden Madrid (CSIC), Department of Biodiversity and Conservation
There are five geographical regions that have Mediterranean-type climates with warm, dry summers and cool, wet winters. These regions by agricultural standards have infertile soils, geologically speaking are fairly recent, and occupy less than 5% of the Earth. Yet they harbour roughly 20% of known vascular plant species, many of which are locally endemic plants.
The aim of my PhD project is to investigate evolutionary patterns of plant diversity responsible for speciation in two phytogeographic regions, the Mediterranean floristic region and the Cape floristic region of South Africa. We chose two of the few species-rich groups between the two floristic regions: Dianthus, which occurs in high numbers in the Mediterranean Basin (c. 200 species) with low numbers in the Cape (c. 10), and Gladiolus with a contrary distribution (6 vs. 150). These two groups were chosen based on (i) levels of diversity, (ii) distributional patterns, (iii) lack of phylogenetic analysis at the genus level, and (iv) flower morphology constraints. Different flower syndromes are described for both genera, including hawkmoth (Sphingidae) species as main pollinator in particular groups. Phylogenetic inferences of hawkmoth species are intended to be performed to link groups of pollinators and flower syndromes in both Dianthus and Gladiolus.
The first objective is to build evolutionary trees of the two genera using several nuclear and plastid markers. Phylogenetic analyses will be then performed to determine times of divergence by means of constructing chronograms. Additionally, to understand and explain the present observed diversity, pollination and breeding systems will be investigated. Both of the plant groups have a wide range of different pollinators and using floral morphology and syndromes one can infer pollination changes through time. The origin and maintenance of different modes of reproduction can affect the diversification of groups.