Final Report Summary - REVOL (Spatially explicit mechanisms of Recent EVOLution in an African biodiversity hotspot)
Biodiversity hotspots are regions where exceptionally high concentrations of endemic species face extraordinary levels of habitat loss. REVOL uses spatially explicit genomic data in two important plant species radiations in the Cape Floristic Region (CFR), an African biodiversity hotspot with extreme environmental heterogeneity (Figure 1), to identify the drivers underlying the recent evolution of new species and their maintenance in sympatry. The elucidation of neutral and adaptive evolutionary processes with unprecedented depth in selected species of the Restionaceae and Proteaceae families provides critical information for the design of effective strategies for the long-term conservation of the hyperdiverse ecosystem of the Cape Flora in the face of global change, and its sustainable use, enabling socio-economic benefits.
Restriction-site associated DNA markers and plastid DNA markers have been assayed in natural populations of selected Restionaceae and Proteaceae (Figure 2) species. The geographic structure of genetic diversity informed on past range dynamics as well as contact zones between differentiated gene pools. Bayesian analysis was used to detect outlier genes with particularly high or low differentiation among populations. These genes are candidates for directional or stabilising selection, respectively. Generalized mixed linear modelling was used to relate genetic patterns to environmental, floristic as well as geographic data.
We have studied the earliest stages of evolutionary divergence in the widespread CFR endemic Restio capensis (L.) H.P. Linder & C.R. Hardy (Restionaceae). W examined diverging populations of this morphotaxon for plastid DNA sequences and >14 400 nuclear RAD sequencing markers. Population divergence across the extreme environmental mosaic of the CFR is mostly driven by isolation by environment (IBE) in this taxon rather than isolation by distance (IBD) for both neutral and non-neutral markers. This result is consistent with genome hitchhiking processes or coupling effects during early stages of divergence. Mixed modelling of plastid DNA and single divergent RAD outlier loci confirmed the predominant role of climate and pointed to additional drivers of divergence, such as drift and ecological agents of selection captured by phytogeographic zones. Our study, published in Molecular Ecology (Lexer et al, 2014, Mol Ecol 23: 4373–4386), demonstrates the usefulness of population genomics for disentangling the effects of IBD and IBE along the divergence continuum often found in species radiations across heterogeneous ecological landscapes.
Data on additional species at more advanced stages of divergence will complete the picture of evolutionary processes at stake, and a functional exploration of outlier genes may, in some cases, give additional information on evolutionary drivers. Our results so far highlight that conserving a high environmental heterogeneity across the CFR is fundamental for the conservation of the evolutionary potential in this biodiversity hotspot.
This project created opportunities to initiate and strengthen collaborative research in the European Research Area and beyond. Its results have been presented and discussed at the AETFAT conference (Association for the study of the flora of tropical Africa, Stellenbosch 2014) in South Africa, where local stakeholders were present. Outreach activities of this project have targeted the general public through radio broadcasts. A science workshop for school children (Figure 3) has presented concepts of evolutionary biology and nature conservation.
Restriction-site associated DNA markers and plastid DNA markers have been assayed in natural populations of selected Restionaceae and Proteaceae (Figure 2) species. The geographic structure of genetic diversity informed on past range dynamics as well as contact zones between differentiated gene pools. Bayesian analysis was used to detect outlier genes with particularly high or low differentiation among populations. These genes are candidates for directional or stabilising selection, respectively. Generalized mixed linear modelling was used to relate genetic patterns to environmental, floristic as well as geographic data.
We have studied the earliest stages of evolutionary divergence in the widespread CFR endemic Restio capensis (L.) H.P. Linder & C.R. Hardy (Restionaceae). W examined diverging populations of this morphotaxon for plastid DNA sequences and >14 400 nuclear RAD sequencing markers. Population divergence across the extreme environmental mosaic of the CFR is mostly driven by isolation by environment (IBE) in this taxon rather than isolation by distance (IBD) for both neutral and non-neutral markers. This result is consistent with genome hitchhiking processes or coupling effects during early stages of divergence. Mixed modelling of plastid DNA and single divergent RAD outlier loci confirmed the predominant role of climate and pointed to additional drivers of divergence, such as drift and ecological agents of selection captured by phytogeographic zones. Our study, published in Molecular Ecology (Lexer et al, 2014, Mol Ecol 23: 4373–4386), demonstrates the usefulness of population genomics for disentangling the effects of IBD and IBE along the divergence continuum often found in species radiations across heterogeneous ecological landscapes.
Data on additional species at more advanced stages of divergence will complete the picture of evolutionary processes at stake, and a functional exploration of outlier genes may, in some cases, give additional information on evolutionary drivers. Our results so far highlight that conserving a high environmental heterogeneity across the CFR is fundamental for the conservation of the evolutionary potential in this biodiversity hotspot.
This project created opportunities to initiate and strengthen collaborative research in the European Research Area and beyond. Its results have been presented and discussed at the AETFAT conference (Association for the study of the flora of tropical Africa, Stellenbosch 2014) in South Africa, where local stakeholders were present. Outreach activities of this project have targeted the general public through radio broadcasts. A science workshop for school children (Figure 3) has presented concepts of evolutionary biology and nature conservation.