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Prof. Geerts

img bio geerts

Within the ecological field of plant-animal interactions, I am interested in pollination and the change and breakdown of pollination communities due to anthropogenic impact.

Another main research area involves alien invasive plants, and in particular emerging invasive plant species. I also have an interest in the long term impact of reduced pollination on plants. This is the case for some species in fragmented habitat. Whether these populations are heading for extinction, I try to answer with a demographic modelling approach.

Current projects include assessing the reproduction strategies of invasive plant species in South Africa with currently restricted distributions and determine whether there is a lag phase because plants are self-incompatible. This work is done in conjunction with the Early Detection and Rapid Response unit (EDRR) of SANBI. Other research projects involve the restoration of pollinator migration routes by creating stepping stones in urban environments.

Selected publications

Geerts, S., Mashele, B.V., Visser, V. and Wilson, J.R.U.  2016. Lack of human assisted dispersal means Pueraria montana var. lobata (kudzu vine) could still be eradicated from South Africa. Biological Invasions DOI 10.1007/s10530-016-1226-y

Geerts, S., 2016.Can short-billed nectar thieving sunbirds replace long-billed sunbird pollinators in transformed landscapes? Plant Biology doi:10.1111/plb.12474.

Geerts, S.,van der Linden, J., van der Linden, E. 2016. The ecology and foraging behaviour of the harvester termite, Baucaliotermes hainesi in semi-arid grasslands in the northwestern interior of South Africa. Insectes Sociaux, 63(3), 457-465.

Moodley, D.,  Geerts, S., Richardson, D. M. and Wilson, J.R.U.  2016. The importance of pollinators and autonomous self-fertilization in the early stages of plant invasions: Banksia and Hakea (Proteaceae) as case studies. Plant Biology 18(1): 124–131. 

Heystek A., Geerts, S., Barnard, P., Pauw, A. 2014. Pink flower preference in sunbirds does not translate into plant fitness differences in a polymorphic Erica species. Evolutionary Ecology 28: 457-470.

Moodley, D., Geerts, S., Rebelo, T., Richardson, D. M. and Wilson, J.R.U. 2014. Site-specific conditions influence plant naturalization: The case of alien Proteaceae in South Africa. Acta Oecologia 59: 62-71.

Moodley, D., Geerts, S., Richardson, D. M. and Wilson, J.R.U. 2013. Different traits determine introduction, naturalization and invasion success in woody plants: Proteaceae as a test case. PLoS ONE 8(9): e75078. doi:10.1371/journal.pone.0075078

Geerts, S., Botha, P.W., Visser, V., Richardson, D. M. and Wilson, J.R.U. 2013. Montpellier broom (Genista monspessulana) and Spanish broom (Spartium junceum) in South Africa: an assessment of invasiveness and options for management. South African Journal of Botany, 87: 134-145.

Geerts, S., Moodley, D., Gaertner, M., Le Roux, J. J., McGeoch, M., Muofhe, C., Richardson, D. M. and Wilson, J.R.U. 2013. The absence of fire can cause a lag phase—the invasion dynamics of Banksia ericifolia (Proteaceae). Austral Ecology 38, 931–941.

Ollerton, J., Watts, S., Connerty, S., Lock, J., Morgan, L., Wilson, I., Schueller, S., Nattero, J., Cocucci, A.A., Izhaki, I., Geerts, S., Pauw, A. and Stout, J.C. 2012 Pollination ecology of the invasive tree tobacco Nicotiana glauca: comparisons across native and non-native ranges. Journal of Pollination Ecology, 9(12): 85-95.

Geerts, S., and A. Pauw. 2012. The cost of being specialised: pollinator limitation in the endangered geophyte Brunsvigia litoralis (Amaryllidaceae) in the Cape Floristic Region of South Africa. South African Journal of Botany 78: 159–164.

Geerts, S., Malherbe. T, A. Pauw. 2012. Reduced flower visitation by nectar-feeding birds in response to fire in Cape fynbos vegetation, South Africa. Journal of Ornithology 153 (2): 297-301.

Geerts, S., and A. Pauw. 2011 Farming with native bees (Apis mellifera subsp. capensis) has varied effects on nectar-feeding bird communities in South African fynbos vegetation. Population Ecology 53:333–339.

Geerts, S., and A. Pauw. 2011 Easy technique for assessing pollination rates in the genus Erica reveals road impact on bird pollination in the Cape fynbos, South Africa. Austral Ecology 36, 656–662.

JJ Le Roux, S Geerts, P Ivey, S Krausse, DM Richardson, J. Suda, JRU Wilson 2010. Molecular systematics and ecology of invasive Kangaroo Paws in South Africa: management implications for a horticultural important genus. Biological invasions 12:3989–4002.

Geerts, S., and A. Pauw. 2009. Hyper-specialization for long-billed bird pollination in a guild of South African plants: the Malachite Sunbird pollination syndrome. South African Journal of Botany 75:699-706.

Geerts, S., and A. Pauw. 2009. African sunbirds hover to pollinate an invasive hummingbird-pollinated plant. Oikos 118:573-579.