A new late Pleistocene subfossil site (Tsaramody, Sambaina basin, central Madagascar) with implications for the chronology of habitat and megafaunal community change on Madagascar's Central Highlands

Abstract

Madagascar is a complex ‘biodiversity hotspot’ with a rapidly dwindling biota. The Late Quaternary subfossil record includes many extinct species whose loss is attributed to natural climate change and human impacts. Investigation of the chronology of these events is challenging because few localities document pre‐Holocene communities not impacted by humans. Caves with extinct lemurs of large body size comprise some of Madagascar's richest subfossil sites, but provide only a limited window into the island's past. Open highland sites may have fewer primates, but may better document other megafauna, and allow the analysis of the role of the Central Highlands as refugia and as corridors for the dispersal of vertebrates before and after human arrival. Here we present a new subfossil site, Tsaramody (Sambaina basin, Central Madagascar), a high‐altitude wetland area that preserves a diverse late glacial and postglacial vertebrate community. Tsaramody bears testimony to fluctuations in the highland flora during the transition from glacial to postglacial conditions, and the composition of a highland vertebrate community before humans arrived. We compare its biota to those of other sites to begin to document the decline and disappearance of megafauna from some of Madagascar's open ecosystems – wetlands dominated by hippopotamuses and crocodylians. © 2019 John Wiley & Sons, Ltd.

Madagascan highlands: originally woodland and forest containing endemic grasses, not grazing-adapted grassland

“…The evolutionary inconsistency presented by all single-lineage Madagascan endemic vertebrates is problematic if highland grassland is ancient, but easily explained by grassland recently replacing a wooded ecosystem with limited and ephemeral grass patches. were predominant C 3 feeders, with a single mixed-feeder [1,17]. In other words, to date there is no evidence for an obligate Madagascan C 4 grazer able to exert top-down effects on a vast grassland system.…”

“…Figure 2. Multisource[2,4,13,17,18,23,24] synthesis of events impacting Madagascan highland ecology. (Online version in colour.…”

Late Miocene origin and recent population collapse of the Malagasy savanna olive tree (Noronhia lowryi)

“…Fossil records also suggest that a few extinct endemic grazers -giant tortoises, pygmee hippopotamuses, and giant lemurs -may have played a role in the dynamic of Malagasy savannas (e.g. Burney et al, 2004;Virah-Sawmy et al, 2010;Pedrono et al, 2013;Goodman and Jungers, 2014;Samonds et al, 2019. Their demise in the last millennia and the rise of pastoralism ca.…”

Seeing the forest for the trees—and the grasses: revisiting the evidence for grazer-maintained grasslands in Madagascar's Central Highlands

“…[13] note, published isotope data for Madagascar's Central Highlands are taxonomically limited (favouring lemurs) and scattered across multiple sources and sites [14][15][16][17][18][19]. We seek to help rectify this gap by summarizing existing radiocarbon and δ 13 C data and providing new data for lemurs, hippos and a euplerid carnivoran from the ecoregion (figure 1; electronic supplementary material, table S1).…”

“…We seek to help rectify this gap by summarizing existing radiocarbon and δ 13 C data and providing new data for lemurs, hippos and a euplerid carnivoran from the ecoregion (figure 1; electronic supplementary material, table S1). Sample preparation and analysis followed [18]. Raw isotope data were normalized using internal reference materials following [20].…”