Alien Plant Invasion in Southern Africa and Robben island: The Role of Phylogeny, Functional traits and

Climate Change

Kowiyou Yessoufou

University of South Africa

yessok@unisa.ac.zakowiyouyessoufou1@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