Quartz Islands II - Cross-scale determinants of plant diversity and endemism in quartz island archipelagos in southern Africa

• Applicants: Professor Dr. Severin Irl; Privatdozentin Dr. Ute Schmiedel
• Subject Area: Ecology and Biodiversity of Plants and Ecosystems ; Physical Geography
• Term: since 2018
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 404519812

In the arid western parts of southern Africa, soil types that are densely covered by white quartz gravel appear as distinct terrestrial “islands”, which are surrounded by the zonal vegetation. The vegetation of the quartz islands is rich in habitat specialists, dominated by compact miniature shrubs with large succulent leaves. The quartz islands in southern Africa are clustered into six groups (“archipelagos”) that are subject to different climates along the western coast. Each of the quartz island archipelagos has its own flora of (quartz) habitat-specialised species that evolved locally (endemism). Yet, the quartz island vegetation in the region reveals strong structural similarities in terms of the species’ physiognomy and spatial patterns. The overarching research objective of the proposed project is therefore to understand the processes that generate and maintain habitat specialisation, endemism, biodiversity and functional adaptation on terrestrial quartz islands. For this aim, we will upscale our work from one of the archipelagos (Quartz Islands I) to all six archipelagos of southern Africa and shift our research focus to combine local with large-scale drivers of plant diversity and endemism. Quartz islands and their archipelagos present highly suited model systems that offer clear boundaries, unique floras and a vegetation with spectacular, yet vulnerable life forms. In the five work packages (WP) of the project, we will apply state-of-the-art sampling, plant functional trait analysis, germination experiments and remote sensing techniques and closely collaborate with our collaborating partners from southern Africa and Germany. We will assess the spatial patterns of island distribution and compile a trait database of the quartz island flora for all archipelagos in southern Africa (WP1). Based on WP1 we will apply island biogeographical theories to test for drivers of taxonomic and functional diversity and endemism of quartz island floras (WP2). We will explore the drivers of species and trait filtering along edaphic gradients on the quartz islands of the six archipelagos in the region (WP3). In WP4 we will further study the ecological processes that are responsible for the strong selection for special plant trait and species composition on quartz islands and between quartz islands and the surrounding zonal vegetation. We will apply germination experiments on different substrates, mimicking the dominant soil gradients as well as testing the adaptive advantage (drought tolerance) of the dominant plant life-form types on quartz islands (WP4). In WP5 the data and findings of the project finally will be used under consideration of the edaphism-concept to identify how diversity is generated on islands across scales – with edaphism linking unique soil conditions with endemism and functional adaptation.

• DFG Programme: Research Grants