Do size and age matter? Exploring the origins and drivers of plant diversity on islands

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Orchidaceae and Myrtaceae are two characteristic and diverse floristic elements of the Caribbean region in general, as well as Hispaniol. Recent studies indicate that both groups might have originated in continental Neotropical biogeographical regions. In particular, the Tropical Andes and southeastern South America were an important source area of migrants for Orchidaceae and Myrtaceae. The Caribbean flora is thought to be derived from a mix of consistent in-situ diversification but with important contributions from mainland South America. However, the detailed macro-evolutionary dynamics and origins of these key Caribbean elements are still poorly understood. To address such knowledge gaps, more phylogenomic data is required to reconstruct evolutionary patterns in island systems with different geological histories and current pressures. Logical study-groups with which to disentangle influences of putative drivers of endemism on islands are lineages with wide ecological niches and high species diversity, such as Orchidaceae and Myrtaceae. The overarching aims of this project are to generate robust and well sampled phylogenomic frameworks for the Orchidaceae and Myrtaceae using highthroughput sequencing datasets that can enable the tracing in time and space the origin and diversification of these two groups in Hispaniola. Specifically, we ask the following questions: A) where is the source of species diversity in these groups? B) How does geological isolation vs biological exchange with other island or continental systems influence island endemism? C) How does island size and age influence the mode and tempo of island flora evolution? The study will test the following hypotheses: H1: Most endemic species found on the island of Hispaniola are the result of in-situ diversification of pre-adapted migrants. H2: Island age and size differences are not significant relative to levels of species endemism in island systems. H3: Niche heterogeneity resulting from mountain formation and/or variations in climate or geological variables had a greater influence in rates of diversification of Orchidaceae and Myrtaceae in Hispaniola than the pace at which these niches evolved. Fieldwork in Hispaniola will be undertaken to collect Orchidaceae and Myrtaceae tissue samples for DNA extraction. Dated super-trees of the study groups will be then produced using field-collected samples supplemented with DNA from herbarium specimens and existing DNA sequence data. Comparative phylogenetic analyses such as ancestral area and diversification rate estimation will be conducted on resulting tree inferences. Ancestral climatic niches of Orchidaceae and Myrtaceae will be estimated from bioclimatic variables. Such analyses coupled with diversification rates analysis will allow comparison of lineages diversification and extinction vs rate of climatic niches change in Hispaniola and will allow the evolution of species-rich groups with differing life histories to be reconstructed and examined in the context of the evolution of an island flora.