Flood-induced Endemism in Amazonian Floodplain Trees Florian Wittmann Ethan Householder, Jochen Schöngart, Maria T. F. Piedade, Rafael L. de Assis, Pia Parolin & Wolfgang J. Junk Max-Planck-Institute for Monitoring of Amazonian Instituto Nacional de Chemistry Wetlands - MAUA Pesquisas da Amazônia _____________________________________________ Monomodal flood pulse _______Methods ! m 2 . 0 1 : e d u t i l p m a n a e M Aquatic phase Terrestrial phase February - July August - January Photographs:J. Schöngart Trees establish where annual inundations average < 7.5 m (white- water) or < 9.0 m (black water), which correponds to a waterlogged or submersed period of 230 and 270 days year-1 (forest border) Inundation reduces oxygen availability to trees by the factor 104 Jackson & Drew (2002): Ann Bot Amazonian floodplain tree species combine several adaptive strategies to tolerate the anaerobic site conditions: • Morpho-anatomical adaptations: Increase of root surfaces, hypertrophic lenticels, aerenquimatic tissues; • Physiological adaptations: leaf shedding during high-water periods, reduction of photosynthesys, switch to anaerobic respiration, elevated production of anti- oxidant compounds = reduction of metabolism = cambial dormancy. Leaf shedding Lenticels Aerenquimatic tissue Adventitious roots Tree species diversity in white-water floodplains > Floristic inventories in várzea forests totaling 60 ha across the Amazon basin Total number of trees: 39.497 Total number of morphotypes: 1.900 Total number of identified species: 918 Total number of genera: 320 Total number of families: 73 Várzea forest are the most species-rich floodplain forests worldwide: -20 x higher than in the European temperate zone (Schnitzler et al. 2005) -10 x higher than in subtropical bottomland forests of N-America (Johnson & Little 1967, Clark & Benforado 1981) -10 x higher than in neotropical savannas and SE-Asian floodplains (Junk et al. 2006, Campbell et al. 2006) Wittmann et al. (2006): J Biogeography Tree species richness and diversity along the flooding gradient n=83 plots totaling 5.24 ha; 2.631 individuals, 306 species (Wittmann et al. 2002: J Trop Ecol) 180 160 1- 140 a h 120 s e 100 ic e 80 p s e 60 e r 40 T 20 0 7.0 6.5 6.0 5.5 5.0 4.5 4.0 3.5 3.0 2.5 1.5 1.0 Mean flood height (m) n=44 plots totaling 62.3 ha; 39.497 individuals, 918 species (Wittmann et al. 2006: J Biogeography) 100 n = 25, R2 = 0.4717 t n 80 e i c if 60 f e o c 40 - a h p 20 lA 0 0 1 2 3 4 5 6 Mean flood height (m) Tree species richness and diversity along the flooding gradient n=83 plots totaling 5.24 ha; 2.631 individuals, 306 species (Wittmann et al. 2002: J Trop Ecol) Low várzea High várzea 180 160 1- 140 a h 120 s e 100 ic e 80 p s e 60 e r 40 T 20 0 7.0 6.5 6.0 5.5 5.0 4.5 4.0 3.5 3.0 2.5 1.5 1.0 Mean flood height (m) n=44 plots totaling 62.3 ha; 39.497 individuals, 918 species (Wittmann et al. 2006: J Biogeography) 100 High várzea n = 25, R2 = 0.4717 t n 80 e Low várzea i c if 60 f e o c 40 - a h p 20 lA 0 0 1 2 3 4 5 6 Mean flood height (m) Floristic similarity between Amazonian várzea and upland forests Terra firme (non-flooded uplands) 9.8 30.1 25-32 Low várzea 26 High várzea > 3 m < 3 m Floodplain data resumed in: Wittmann et al. (2006): J Biogeography Terra firme data resumed in: Oliveira & Nelson (2001), Pitman et al. (2002), Ter Steege et al. (2006) From where came the várzea tree species? Are there endemic tree species? 1. Taxonomic-evolutionary hypothesys: Floodplain genotypes originate from adjacent upland forests (Kubitzki 1989) 2. Physiological hypothesys: Several Amazonian floodplain genera and species originate from ecosystems/biomes with climatologically and/or edaphically aridity = neotropical savannas (Prance 1979, Worbes et al. 1992). 3. Endemism: Due to the exceptional high inundations, and the high number of adaptive strategies of trees to flooding, Amazonian floodplains are rich in endemic tree species (Kubitzki 1989, This is in contrast to other neotropical wetlands, where endemic tree species Junk 1989). are rare, or even absent (Junk et al. 2006, Veneklaas et al. 2005, Wittmann et al. 2010) Prance (1979): Brittonia; Junk (1989): Academic Press, London; Kubitzki (1989): Plant Syst Evol; Worbes et al. (1992): J Veg Sci; Veneklaas et al. (2005): Ecography; Junk et al. (2006): Aquatic Sci; Wittmann et al. (2010): Springer , New York Evolution of Amazonian Wetlands The existence of tropical forests within the Amazon basin is evident since the upper Eocene (approx. 30 Ma B.P.) (Burnham & Johnson 2004: Phil Trans R Soc Lond) 83-67 Ma 61-60 Ma Repeated marine ingressions in the pre-Andean depression 12-10 Ma 43-40 Ma Formation of Lago Pozo (alluvial, Andean sediment) 20-12 Ma Formation of Lago Pebas (alluvial, Andean sediment) 13.5 Ma Fossil of fruit-feeding fish (Colossoma macropomum) indicate no changes to recent diet 8 Ma Amazon starts to drain eastwards Behling et al. (2001): Palaeogeo Plaeoclima < 1 Ma Pleistocene and Holocene climate changes strongly Palaeoeco influence the Sea level and thus the Amazon River system.