Sporormiellaand the late Holocene extinctions in Madagascar

Abstract

Fossil spores of the dung fungus Sporormiella spp. in sediment cores from throughout Madagascar provide new information concerning megafaunal extinction and the introduction of livestock. Sporormiella percentages are very high in prehuman southwest Madagascar, but at the site with best stratigraphic resolution the spore declines sharply by Ϸ1,720 yr B.P. (radiocarbon years ago). Within a few centuries there is a concomitant rise in microscopic charcoal that probably represents human transformation of the local environment. Reduced megaherbivore biomass in wooded savannas may have resulted in increased plant biomass and more severe fires. Some now-extinct taxa persisted locally for a millennium or more after the inferred megafaunal decline. Sites in closed humid forests of northwest Madagascar and a montane ericoid formation of the central highlands show only low to moderate Sporormiella percentages before humans. A subsequent rise in spore concentrations, thought to be evidence for livestock proliferation, occurs earliest at Amparihibe in the northwest at Ϸ1,130 yr B.P. F ossil spores of the dung fungus Sporormiella spp. have been shown in western North America to serve as a reliable proxy for megafaunal biomass in late Pleistocene sediments. These spores decline rapidly at the end of the Pleistocene at the approximate time of megafaunal extinctions and increase again in sediments of recent centuries after livestock introduction (1, 2). We present here application of the technique described in refs. 1 and 2 to the study of late Holocene extinctions on the island of Madagascar. Sediment cores from throughout the island contain these spores, and stratigraphic trends offer a way to produce a chronology for megafaunal decline and livestock introductions.Research over the last two decades has clarified many aspects of this remarkable ecological catastrophe (3-5), which eliminated virtually the entire endemic megafauna including the giant lemurs, elephant birds, pygmy hippopotami, and giant tortoises. Four independent lines of stratigraphic evidence are consistent with the beginning of a human presence on the island at least by Ϸ2,000 radiocarbon years before present (yr B.P.): (i) dates on humanmodified bones of extinct animals (6); (ii) pollen of prehistorically introduced plants (7); (iii) a large spike of charcoal particles in lake and bog sediments (5); and (iv) pollen evidence for a decline in forest and increase in grasses and ruderal herbs (8). Studies of the Malagasy language also show a separation from its closest surviving linguistic relatives in the highlands of Borneo approximately two millennia ago, although divergence could have begun before protoMalagasy speakers departed from Indonesia (9). Integrated multidisciplinary analyses of rich late Holocene fossil sites with accelerator mass spectrometry dating and close stratigraphic control show that, whereas some megafaunal taxa seem to decline rapidly after human arrival, others persisted at some sites for a millennium or more after first evidence for hum...

The primate semicircular canal system and locomotion

“…These latter species have only become extinct very recently and can be regarded as part of the same ecological community as living lemurs (31,32). Most of the subfossil lemurs were much larger than their living relatives and so extend the size range of strepsirrhines to that of large anthropoids.…”

Combining paleo-data and modern exclosure experiments to assess the impact of megafauna extinctions on woody vegetation

“…Increased fire activity immediately after the Pleistocene extinctions (73)(74)(75)(76)78) and so can be used to provide the ecological context of functional large herbivore collapse (73)(74)(75)(76)(77). Several pollen records from eastern North America show an increase in hardwood deciduous taxa immediately after the Sporormiella-indicated megafaunal decline, including increases in palatable and shade-tolerant woody species (74,75,78), and a more closed vegetation, consistent with release from browsing pressure.…”

An old adaptive radiation of forest dung beetles in Madagascar

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