Research overview: pollination, restoration and invasive alien plant species. Sjirk Geerts Department of Conservation, and Marine Sciences, Cape Peninsula University of Technology, PO Box 652, Cape Town 8000, South Africa.
Introduction My aim is to explore the unknowns of the natural word at the scale of species interaction webs and I see this as an essential return to natural history science; biological science is currently focused on continental- and global-scale ideas, but we’re largely missing the radical ecological changes happening in our own backyards. My personal research agenda has been, simply put, focused on the “plant–animal interactions in novel ecosystems in the Cape and beyond”. On this foundation, I have built (and continue to build) my research consisting of two pillars 1) pollination and plant reproduction, and 2) alien plant invasive processes and management. These pillars are crowned with a link focused on bridging the research between them; for example, the sometimes unexpected pollinators in the novel range of alien plants (Geerts and Pauw 2009b) and the role of pollinators during plant invasions (Moodley et al., 2016; Adedoja et al., 2021; Geerts and Adedoja, 2021). With the current global decline in pollinators, and the concurrent decline in plant species, pollination research is becoming increasingly important. However, studies outside Europe and North-America, and on groups beyond insects, are largely lacking. I study how pollination configures plant and bird communities in a biodiversity hotspot, the Cape Floristic Region of South Africa. I focus primarily on nectar feeding birds due to their disproportional importance in maintaining high plant diversity (more than 350 plant species dependent on only a few nectar feeding birds). Built on the understanding of plant-bird communities, I established how bird communities may disassemble in response to different pressures. For example, the effect of habitat fragmentation is becoming increasingly important as our urban areas expand. Fragmentation results in species-poor communities with specific nectar feeding birds lost in small urban fragments (Geerts and Pauw 2012 SAJB), including specialised pollinators in particular (Geerts and Pauw 2009a SAJB). Short-billed sunbirds are not substitutes, and fruit production could be increased by 35% in transformed landscapes if long-billed sunbirds are encouraged to return (and there are ways to do this!) (Geerts 2016). In other research, I demonstrated that certain nectar feeding bird species avoid roads, and this challenges the idea that roadside verges act as biodiversity refugia and corridors in otherwise transformed landscapes (Geerts, 2011; Geerts and Pauw 2011a; Geerts et al. 2020; Mnisi et al., 2021; Geerts and Pauw, 2013). 1