Research
Psiadia callocephala (photo by C.Thébaud, 2006)
The Madagascar and Indian Ocean Islands hotspot (MIOI) is renowned for its exceptionally high levels of endemicity and unparalleled habitat diversity. The breakup of East Gondwana and the isolation of Madagascar (120-160Mya) have had a major influence on the evolutionary history of the flora and fauna of the region. Several archipelagoes surround Madagascar, consisting mostly of young, volcanic islands. These islands hold a surprisingly high number of endemic lineages, given their recent origin and limited surface area. The origin, biogeographic history and causes for evolutionary diversification of insular biota, as well as the relationships with taxa on Madagascar, are far from understood.
In contrast to lineages characterized by single island endemic species, there are also many genera that consist of one or a few widespread species, occurring throughout the hotspot. It is unclear whether this disparity in richness and patterns of diversification is due to factors relating to timing of colonization, variation in diversification rates or life history traits.
Aim
The aim of my project is to understand what causes are underlying disparity in diversity and and patterns of diversification between plant lineages in the MIOI hotspot. I have selected a set of genera that show extensive diversification within the hotspot (Psiadia -Asteraceae; Monimia/Tambourissa – Monimiaceae; Badula/Oncostemum – Myrsinaceae; Diospyros – Ebenaceae; Gaertnera – Rubiaceae). A second set of taxa consists of widespread species (Aphloia – Aphloiaceae; Dodonaea – Sapindaceae; Securinega – Euphorbiaceae). I am using a set of eight molecular markers to reconstruct and compare the evolutionary history of these lineages by studying and comparing patterns of dispersal and diversification, and by analyzing diversification rates and rate shifts.
Key Results
Preliminary results indicate that diversification of major species rich clades has occurred in recent times within the hotspot, and taxa have repeatedly radiated on separate islands following dispersal. Analyses show significant shifts in diversification rates in some lineages, but more continuous stable rates in others. Patterns of dispersal and colonization throughout the region appear to be mostly simple (i.e. following the unidirectional Progression Rule type), but point to an older age for the Mascarene island of Rodrigues, supporting recent suggestions of it being the oldest island in the chain.
Genotypic and phenotypic variation in three lineages across a common distributional range. (J.S.Strijk, 2006)
Different scenarios of colonization and evolutionary diversification in an archipelago setting. (J.S.Strijk, 2006)
Talks and Dissemination of Results
PhD-project presentation, Workshop Advanced Methods in Reconstructing Molecular Phylogenetic Relationships, European Molecular Biology Organization, Rio de Janeiro Botanical Garden, Rio de Janeiro, Brazil. March 2008.
Poster presentation: Evolution of the genus Badula (Myrsinaceae): endemic rare trees of the Mascarene Islands. International Symposium “Evolutionary Islands 150 Years After Darwin”, Leiden, the Netherlands. February 2009.
Curriculum Vitae
2006-present PhD-student and Marie-Curie Early Stage Researcher, Laboratoire d’Evolution et Diversité Biologique, Université Paul Sabatier, Toulouse, France.
2005-2006 Biodiversity Data Technician, National Herbarium of the Netherlands, Wageningen University, Wageningen, Netherlands.
1998-2005 Biology, Wageningen University, Wageningen, the Netherlands.
2004-2005 Internship Molecular Plant Systematics: The quest for phylogenetically informative nuclear markers: Utility of ncpGS in resolving phylogenetic relations in Duguetia (Annonaceae).
2003-2004 MSc. thesis Plant Systematics: Vascular epiphytes of Gabon: a taxonomic and ecological comparison of occurrence, composition and diversity on different phorophytes in the Minkébé and Monts de Cristal-regions, Gabon.
2002-2003 MSc. thesis Animal Ecology: Effects of forest fragmentation on avian diversity, abundance and community structure in the Northern Sierra Madre Mountain region, Philippines.
2000-2004 Student Assistant Course ‘Flora of the Netherlands’, National Herbarium of the Netherlands, Wageningen University, Wageningen, Netherlands.