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Alien Plant Invasion in Southern Africa and Robben island: The Role of Phylogeny, Functional traits and
Climate Change
Kowiyou Yessoufou
University of South Africa
[email protected]@gmail.com
Summary Vegetation types
Diversity of Vegetation types Biodiversity hotspots
Southern Africa as hot spots of diversity
Fynbos
Namib Desert
Grassland
Savanna
Coastal Belt
Miombo Woodland
Southern Africa as hot spots of diversity…
Wilson et al. 2013 S Afr J Sci. 109(5/6)
One Threat to native diversity in Southern Africa
1935
Robben Island: ~ half of the island is covered by alien plants
Rouget et al. 2015. South Afr J. Bot. doi: 10.1016/j.sajb.2015.04.009
Biome specificity in geographic pattern of alien
Hypotheses
Thuiller et al. 2010. Divers. Distr. 16, 461–475
Contradicting patterns reported in literature
Documenting alien and native flora in Southern Africa
6-year data collection across Southern Africa
6-year Lab works: DNA data for Southern Africa’s flora
1178 natives
232 exotics 169 invasives
63 non-invasives
o 584 genera
o 131 families
• 1410 taxa
Sampled taxa in figures
Bezeng et al. 2015, J. Ecol. 103, 871–879
In-Nat Non_Inv-NatIn-Non_Inv
Nat Non_InvInv
Mann–Whitney U-test, W = 303 208, P < 0.001
Comparing phylogenetic relatedness
Comparing phylogenetic relatedness on Robben Island
Similar pattern observed for random communities
Discounting Darwin’s Nat. Hypothesis
Johnson 2010, Phil. Trans. R. Soc. B 365, 499–516
Documenting functional traits of alien and native flora
Comparing functional traits
Comparing functional traits…
Comparing functional traits…
Chytrý et al. 2008. Ecology 89: 1541–1553.
Role of climate change
MaxEnt projection
Role of climate change…
Role of climate change…
Exclude species of less than 20 (a), 30 (b) and 50 occurrence points (c)
a
b
c
Sensitivity of predictions to number of occurrence points
Model sensitivity to dates of introduction
Species–climate equilibrium assumption of SDMs
• Differences in functional traits between native and non-natives BUT NOT between invasive and non-native species
• These differences translate into a pattern that matches the predictions of Darwin’s Naturalization Hypothesis
• Climate change could contribute to fighting/limiting geographic ranges in the region
Conclusion
Acknowledgement