Exploring the savanna and grassland biomes of Madagascar: an African perspective William Bond, Joel Ratsirarson, Tristan Charles- Dominique, Lesego Khomo, Muthama Muasya, Jeannin Ranaivonasy Dept of Biological Sciences, UCT and Departement des Eaux et Forets, Univ. Antananarivo Madagascar

• Mini-continent –world’s 4th largest island ~0.75 million km2 • Currently 400 km of sea between Africa, Madagascar • Separated from Africa >100 Ma, and India from ~89 Ma+ Thickets of southern Madagascar Global biodiversity hotspot: >60 spp of lemurs, 12000 plant spp, >90% endemic A very different fauna mostly extinct

Several spp of giant tortoises

2-3 spp of Hippos One a grazer related to H. amphibius One (2?) browsers

~ 7 spp of elephant birds

Grasslands are the most extensive vegetation in both Africa and Madagascar

Humans settled Madagascar <2000 y BP. Through burning, they converted forest to grasslands and savannas Most extreme example of fire-induced biome switch on earth?

80% of island = fire-maintained grassland or savanna The real vegetation map The formation of the prairies [of Madagascar] is totally artificial and the result of fire. Perrier de la Baˆthie (1921, pp. 9– 13). • If grasslands <2000 y old then – Very low grass diversity and species turnover? – No endemics? • No shade-intolerant forbs, trees, shrubs in grasslands • No grassland-dependent birds, mammals, reptiles, insects Biogeographic clues – C4 grasses

– Very low plant diversity and species turnover? – No endemics?

C4 grass genera in Madagascar

ENDEMICENDEMIC SHAREDSHARED WITH WITH SOUTH SOUTH AFRICA AFRICA & RESTREST OF OF AFRICA/ASIA AFRICA Camusiella Acrachne Enneapogon Perotis Crypsis Decaryella Alloteropsis Enteropogon Pogonarthria Dimeria Isalus Andropogon Eragrostis Rhytachne Euclasta Lasiorrachis Aristida Eriochloa Rottboellia Garnotia Neostapfiella Arthraxon Eulalia Schizachyrium Halopyrum Sclerodactylon Arundinella Hackelochloa Schoenefeldia Heteropholis Viguierella Axonopus Harpochloa Setaria Neyraudia Yvesia Bothriochloa Hemarthria Sorghastrum Redfieldia Brachiaria Heteropogon Sorghum Saccharum Cenchrus Hyparrhenia Sporobolus Thuarea Chloris Hyperthelia Stenotaphrum Tripsacum Chrysopogon Imperata Themeda Zoysia Coix Ischaemum Trachypogon Craspedorhachis Leptocarydion Tragus Ctenium Leptochloa Tricholaena Cymbopogon Lepturus Trichopteryx Cymbosetaria Loudetia Tripogon Cynodon Melinis Tristachya Dactyloctenium Microchloa Urelytrum Dichanthium Monocymbium Urochloa Digitaria Oxyrhachis Vetiveria Dinebra Panicum Diplachne Paratheria 94 genera Echinochloa Paspalidium Eleusine Paspalum 8 endemic C4 genera Elionurus Pennisetum >200 endemic grass spp Relative to South Africa

• Madagascar has about 12 000 plant species, nearly 600 grass spp (5% of the flora) • South Africa has 22000 spp, about 910 grass spp (4 % of the flora!!) • Species:genus ratio 4.3 Madagascar • Species:genus ratio 5.1 South Africa

• THIS IS NOT A NEW GRASS INVASION Some key questions for grassland conservation biology • How old are grasslands? • How diverse are grasslands – Plants – Animals • What do grasslands contribute to biodiversity of forest/grassland mosaics • What are the major threats to grassland conservation? • Can grassland loss be reversed? Can grasslands be restored?

Are these forest/grassland mosaics a result of deforestation? Or are these alternative stable states with ancient origins? Mosaics caused by deforestation? Or ancient alternative biome states? • We explored – Grassland spp and functional diversity – Woody plant habitat specialization – Soil isotopic composition The deforestation hypothesis The deforestation hypothesis

Burning (some felling?) destroys forest. Trees in 20 grassland resist fire by pre-adaptations The alternative biome state hypothesis

Trees, shrubs in forest interior differ from forest margins which differ from grassland sites Forest margin Savanna

Forest interior

We sampled transects in each habitat type counting individuals of woody plant species and frequency of grassland plants Methods

• Sampled in transects in the three habitat types • Density, size of woody plants as measure of importance • Common spp of each habitat scored for functional traits – Bud location, bark thickness, architecture, regeneration mode (sprouting) • Frequency of grassland plants

Forest interior Forest margin Savanna Uapaca bojeri savanna What we found for woody plants

• Distinct spp assemblages in forest, margin, savanna • Functional trait differences in each of the three habitats

Ankazobe grasslands NW of Tana

Aristida Central highlands rufescens Loudetia

Themeda

Hyparhenia rufa

Schizachyrium

Aristida sp.

Grasslands dominated by just two species: Aristida rufescens, Loudetia simplex These are branched grasses able to grow through large piles of dead litter. These very low diversity grasslands were the norm for central highlands grasslands Why such low grass diversity?

• Grasses new? Island isolation? • Long fire suppression killing high light- requiring grasses (decreasers, increaser II)? Themeda triandra declines to negligible cover if burnt at intervals longer than ~ 3 years in KZN midlands

Uys et al. 2004 Biol Cons Anzarabe grasslands unburnt for 10 years! Non-grass component of grasslands • Quite diverse with 9-14 species/transect • Erica spp common with up to 3 spp/transect • Asteraceous sub-shrubs (Helichrysum) were also common with up to 5 spp/transect • These woody spp can penetrate the dense dead litter layers as they do in old fire-suppressed SA grasslands • Forbs with USOs were very rare in Central Highlands grasslands (2-3 spp) • This is in striking contrast to South African highveld grasslands where forbs with USOs are abundant and diverse •S. African coastal grassland. 305 plant spp of which 201 forb spp • in 64 x 5m radius plots. Zaloumis, Bond Austral Ecol 2011.

Without burning, these forbs disappear. They are very slow to recolonise an area and tropical grassland restoration has proven very difficult compared to forests. Forbs in Madagascar: low diversity, very few with USOs Why such low forb diversity?

• Grasslands new? Island isolation? • Long fire suppression killing high light- requiring forbs? • In South Africa, fire suppression in high rainfall grasslands for >8 years eliminates forbs with USOs but favours woody shrubs and sub-shrubs

Forb spp composition after 35y burning experiment

BURNT UNBURNT

Fire treatments (1-5y intervals) had completely different spp composition from plots unburnt for 10y+. Uys et al. 2004,Biol Cons Where are Madagascar’s hotspots of grassland diversity? • Where are those 600 spp of grass? • Fire suppression (by law) may have eliminated grass and forb species requiring frequent fires • Are there parts of Madagascar, remote from government, where grasslands burn frequently enough to support diversity? • Or is low diversity an island phenomenon? • Or an indicator of anthropogenic origins? Summary

• Madagascar\s C4 grassy biomes neglected until very recently • Fascinating analogue to African mainland c4 grassy systems • Novel questions e.g. – forest margin spp in RSA? – Origin and antiquity of our grassland biota – Coevolution of grasses, browse plants with an entirely different suite of herbivores – Megafaunal fruit dispersal: do elephants matter? Summary

• Where are the grassland diversity hotspots and how should they be managed? • How transferable is knowledge from Africa to an insular biota? Thanks to

• John Silander, U.Conn for initiating the Madagascar connection • The MacArthur Foundation for funding • The 11 brave Malagasy students for participating in our grassland ecology field work • The University of Antananarivo for hosting us