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Determining the range of suitable environmental conditions under which a plant species can persist and thrive (its “ecological niche") is the key for understanding species' geographic distributions and forecasting their responses to ongoing global change. However, it is difficult to quantify these 'ecological niches' and, until recently, it remained completely unknown how these niches may relate to variation in major plant organs (leaf, architectural and seed traits) that affect persistence. A recent study led by Dr Martina Treurnicht (Treurnicht et al. 2020) addressed these aims using 26 Fynbos Proteaceae species with fire-driven life cycles from the Cape Floristic Region (South Africa). The authors notably found that the niches of these species were particularly well-defined by only a few of the eleven leaf, architectural and seed traits included in their study. The study also found stronger effects between plant traits and species' niches than any previous investigation because Proteaceae are exceptionally well-suited for direct measurements of reproduction and survival rates in many populations across species' entire geographical ranges. Current forecasts of global change impacts on biodiversity often assume that species can survive in the long term under those environmental conditions in which they currently occur. Hence, another investigation by the same authors, led by Dr Joern Pagel (Pagel et al. 2020), examined how large-scale variation in climate, fire frequency and soil conditions determine the reproduction and mortality of these Proteaceae study species. Based on these analyses, the authors were able to determine the range of environmental conditions under which populations of the study species can grow. When comparing these suitable environmental conditions (the “ecological niche") with the current geographical distributions of species, the researchers found distinct mismatches between the ecological niche and the geographical distribution of many of the Fynbos study species. In particular, less mobile species were often found to be absent at suitable locations with environmental conditions within their ecological niche, whereas disturbance-tolerant species were often found at currently unsuitable locations. This means that current estimates of the impacts of climate change and changing fire regimes on Fynbos Proteaceae, which assume that geographical distributions directly reflect species niches, are therefore problematic for species with these characteristics (i.e., less mobile and disturbance-tolerant species). Hence, forecasts of global change impacts on the future distribution and survival of these species can often be too optimistic and need to better account for current niche-distribution mismatches. Together, both studies highlight the importance of demographic and trait-based approaches to study the ecological niches of species to better understand the large-scale threats to biodiversity.

The overarching aim of the cross-continental collaboration between South African (Stellenbosch University & the South African Environmental Observation Network, SAEON Fynbos Node) and German researchers (University of Hohenheim) is to study the processes that underlie the ecological diversity of Fynbos Proteaceae and to improve forecasts of global change impacts in this fire-driven Mediterranean ecosystem. These aims, in particular the establishment of long-term monitoring of Fynbos Proteaceae populations in the Cape Floristic Region, form part of the ongoing Claude Leon Foundation postdoctoral fellowship of Dr Martina Treurnicht which is jointly based at SAEON Fynbos Node and Stellenbosch University.

​Full citations to the research articles (open access): 

- Pagel, J., Treurnicht, M., Bond, W., Kraaij, T., Nottebrock, H., Schutte-Vlok, A., Tonnabel, J., Esler, K.J. & Schurr, F.M. (2020). Mismatches between demographic niches and geographic distributions are strongest in poorly dispersed and highly persistent plant species. PNAS, DOI: https://doi.org/10.1073/pnas.1908684117.

- Treurnicht, M., Pagel, J., Tonnabel, J., Esler, K.J., Slingsby, J.A. & Schurr, F.M. (2020). Functional traits explain the Hutchinsonian niches of plant species. Global Ecology & Biogeography, 29: 534–545. DOI: 10.1111/geb.13048.