Max Planck Institute for Chemistry National Institute for Amazon Research Tree species distribution, endemism, and oligarchy in Amazonian floodplain forests: A species colonization concept for Amazonian white-water floodplains Florian Wittmann

Rio Negro Rio Solimões Manaus Landsat TM, bds 5,4,3 29/11/2005 (INPE) 50 km Manaus Floodplains: km 2 Várzea: km 2 Igapó: km 2 Junk (1997)

____________________________________________________ Methods aquatic phase Monomodal `flood pulse´ m asl terrestrial phase February - JulyAugust - January Daily water-level records of the Manaus harbour Mean amplitude: 10.2 m !

Trees establish where annual inundations average < 7.5 m, which correponds to a waterlogged or submersed period of 270 days year -1 (forest border) Inundation reduces oxygen availability to trees by the factor 10 4 Wittmann et al. (2004): For Ecol Manag Jackson & Colmer (2005): 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 tissue; Physiological adaptations: leaf shedding during high water periods, reduction of photosynthesys, switch to anaerobic respiration = reduction of metabolism = cambial dormancy. Lenticels Adventitious rootsAerenquimatic tissue Leaf shedding

Amazonian várzea forest Várzea forests are the most species-rich floodplain forest worldwide: Inventories with an area of ha scattered over the Amazon basin: Total number of trees: Total number of morphotypes: Total number of identified species: 918 Total number of genera: 320 Total number of families: 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 tropical SE-Asian floodplains (Campbell et al. 2006) -3 x higher than in the Brazilian Pantanal (Junk et al. 2006) Wittmann et al. (2006): J Biogeography

Mean flood height (m) R 2 = 0.68 n=83 plots totalling 5.24 ha; individuals, 306 species (Wittmann et al. 2002: J Trop Ecol) n=44 forest plots totalling 62.3 ha; individuals, 918 species (Wittmann et al. 2006: J Biogeography) Alpha-coefficient (Fisher) 7 0 km 1000 Flooding gradient R 2 = 0.92 low várzea high várzea

Ter Steege et al. (2003, 2006) modeled tree species alpha-diversity across the Amazon basin and concluded that diversity tends to increase from eastern to western Amazonia …. …. the model holds true for upland and high-várzea forests, but not for low-várzea forests, where alpha-diversity is nearly constant across the Amazon basin. Ter Steege et al. (2003): Biodiv & Conservation Ter Steege et al. (2006): Nature

Geographic gradient Floodplain data resumed in: Wittmann et al. (2006): J Biogeography Terra firme data resumed in: Oliveira & Mori (1999), Ribeiro et al. (1999), Harms et al. (2001), Pitman et al. (2001), Duque et al. (2003), Ter Steege et al. (2003), Condit et al. (2004), Oliveira & Amaral (2004), Penaherrera & Asanza (2004), Valencia et al. (2004)

24.7% 9.9% Geographic gradient

Floodplain data resumed in: Wittmann et al. (2006): J Biogeography Terra firme data resumed in: Oliveira & Mori (1999), Ribeiro et al. (1999), Harms et al. (2001), Pitman et al. (2001), Duque et al. (2003), Ter Steege et al. (2003), Condit et al. (2004), Oliveira & Amaral (2004), Penaherrera & Asanza (2004), Valencia et al. (2004) Floristic similarity between Amazonian várzea and upland forests Terra firme (non-flooded uplands) Low várzea > 3 m High várzea < 3 m

Where do the várzea species came from? 1. Taxonomically-evolutionary explanation: Kubitzki (1989) stated that the floodplain genotypes originate from the surrounding uplands. 2. Physiological explanation: Prance (1979) and Worbes et al. (1992) stated that floristic similarities are especially high between floodplains and neotropical biomes with climatically or edaphically induced aridity (Campinas, Cerrado, Caatinga, Llanos). Kubitzki (1989): Plant Syst Evol Prance (1979): Britt Worbes et al. (1992): J Veg Sci

Couroupita subsessilis Pilg. Hura crepitans L. Determining the occurrence and distribution of the 300 most common (= abundant & frequent) várzea tree species: In revised species lists and Floras published in literature (more than 700 ha containing up to individuals across the Neotropis), In herbaria (e.g., Missouri Botanical Garden, New York Botanical Garden, Royal Botanical Gardens Kew, National Herbarium Utrecht, Botanical Garden Rio de Janeiro, INPA-Herbarium, Manaus) In digital databases (e.g., Flora Brasiliensis [Martius ], International Legume Database, etc.)

 Database -Own study sites: 16 permanent sample plots -Review of 28 forest inventories compiled by other authors Authors: Black et al. (1950) Pires & Koury (1959) Balslev et al. (1987) Revilla (1991) Campbell et al. (1992) Worbes et al. (1992) Ayres (1993) Queiroz (1995) Dallmeier et al. (1996) Klinge et al. (1996) Urrego (1997) Nebel et al. (2001) Cattanio et al. (2002) Wittmann et al. (2002) Schöngart (2003) J.C. Monteiro (unpubl.) 62.3 ha, individuals, 918 species 0° 10° S 60° W70° W50° W80° W 10° N North Ecuador Peru Colombia Brazil RDSM Bolivia Manaus Pando km

Defining the most common várzea tree species In each inventory, the Importance Value Index (IVI) was calculated: IVI = rAb + rDom + rFr (Curtis & McIntosh 1951) Overall species importance across the Amazon basin was determined by the Overall Importance Value (OIV): OIV = Σ 1-44 (rIVI) + rF (44 inventories)

Species occurrence (% out of 300 species) Endemism in Amazonian várzea

Species occurrence (% out of 300 species) Occurrence in other Neotropical floodplains

Species occurrence (% out of 300 species) Occurrence in non-flooded moist uplands

Species occurrence (% out of 300 species) Occurrence in non-flooded semi-arid uplands

várzea 24 3 Shared species between várzea & other ecosystems floodplains / riparian forest moist uplands (non-flooded) semi-arid uplands (non-flooded) Shared species (%)

Low-várzea forests highly resemble each other, even when separated over large distances, but show low floristic similarity to the terra firme = many endemic species that occur over thousands of Km = lateral species exchange High-várzea forests represent increasing floristic dissimilarity with increasing distance, but show generally high floristic resemblance to the neighbouring terra firme, with many singletons = vertical species exchange to adjacent uplands. Conclusions

Low-várzea forests highly resemble each other, even when separated over large distances, but show low floristic similarity to the terra firme = many endemic species that occur over thousands of Km = lateral species exchange High-várzea forests represent increasing floristic dissimilarity with increasing distance, but show generally high floristic resemblance to the neighbouring terra firme, with many singletons = vertical species exchange to adjacent uplands. Conclusions Expected reasons: 1) High connectivity of low várzea by means of hydrochoric and ichthyochoric dispersal (Gottsberger 1978, Goulding 1980, Ziburski 1991) 2) Low várzea was less affected by paleoclimatic induced water-level changes than the high várzea (Irion 1984, Junk 1989, Wittmann et al. 2006) = even with postulated dryer conditions during glacial periods, várzea forests persisted (as linear habitats along the main-river channels)

Species immigration, radiation, and species exchange terra firme high várzea low várzea Time forest border lowest flood level highest flood level Point of `no return´ (species dependent) Altitude endemism increasing selection pressure increasing species dominance decreasing species richness pre-formation of adaptations in episodically flooded river margins Tree species colonization concept in Amazonian floodplains Wittmann et al. (in press): Phytogeography, species diversity, community structure, and dynamics of Amazonian floodplain forests. Springer Verlag, Berlin.

The species colonization concept implies that the floodplains acted as linear refuges for moist- sensitive terra firme species during glacial periods (Sioli 1957, Irion 1984, Pires 1984, Sternberg 1986). As orographic or tectonical barriers within the Amazon basin are absent, the continuous disturbance regime imposed by the flood-pulse and the alluvial dynamism especially in the white- waters is the most probable factor influencing speciation processes in equatorial Amazonia, thus contributing to the elevated biodiversity also in upland forests. Conclusions

Paleovárzea The species colonization concept implies that the floodplains acted as linear refuges for moist- sensitive terra firme species during glacial periods (Sioli 1957, Irion 1984, Pires 1984, Sternberg 1986). As orographic or tectonical barriers within the Amazon basin are absent, the continuous disturbance regime imposed by the flood-pulse and the alluvial dynamism especially in the white- waters is therefore the most probable factor influencing speciation processes in equatorial Amazonia, thus contributing to elevated biodiversity also in equatorial upland forests. Conclusions