An alternative hypothesis for the origin of Amazonian bird diversity

Abstract

AimTo determine the origin of the high diversity of birds and other animals and plants in Amazonia. Previous hypotheses are: palaeogeography hypothesis, river hypothesis, riverrefuge hypothesis, refuge hypothesis, disturbance-vicariance hypothesis, gradient hypothesis, pest-pressure hypothesis, intermediate disturbance hypothesis, riverine disturbance hypothesis, models of fine-scale habitat heterogeneity, lake hypothesis, and museum hypothesis.Methods At present there is agreement between areas of high species diversity and sites located over 100 m. As these sites would have been islands during a sea-level rise of this value, it was important to determine the probable distribution of these islands in Amazonia during a marine transgression. For that purpose, I traced the 100 m contour line from topographic maps.Results Two broad marine transgressions would have been produced from the Atlantic Ocean via the Amazon and Orinoco rivers. Two very large islands would have been formed to the north of the Amazon River, and other islands and archipelagos would have been formed along the coastal lowlands of Guiana, and at the periphery of the Amazon basin. The area located between the Solimões and Negro rivers and in the lower Branco would have been completely covered by the sea.Main conclusions A substantial part of the high diversity of forest and nonforest birds in lowland Amazonia can be hypothetysed to have originated during sea-level rises of about 100 m in the Quaternary and late Tertiary. These transgressions would have fragmented the Amazonian lowland into a large number of true islands and archipelagos, thus favouring active allopatric speciation. Values appreciably higher than 100 m above the present sealevel during previous periods of the Tertiary would have produced segregation of the biota earlier than the Tertiary-Quaternary boundary. Sea-level rises and vegetational changes (by aridity or cooling) would thus have driven the speciation pump, and local disturbances and other processes, would maintain the diversity.

The Phylogeography of Amazonia Revisited: New Evidence From Riodinid Butterflies

“…Nores (1999) has suggested that the high levels of Amazonian bird diversity might be explained by Quaternary and upper Tertiary sea-level rises of up to 100 m that would have fragmented the lower Amazonian environment into numerous islands. Although such sea-level rises may also in part explain the high diversity of the C. cleonus group in the lower Amazon, perhaps the repeated confinement of lower Amazon species to very small areas of higher ground during sea-level rises, and the resulting habitat instability, led to their small current range sizes.…”

“…Hypotheses that have been developed to explain these patterns differ in treating speciation as having occurred in sympatry, parapatry, or allopatry and in their emphasis on which physical or ecological barriers were most important in controlling interbreeding and dispersal. They include the gradient hypothesis (steep environmental gradients; Endler 1977Endler , 1982Mallet 1993), palaeogeography hypothesis (tectonic movements and sea-level rises ;Chapman 1917;Emsley 1965;Frailey et al 1988;Räsänen et al 1995;Webb 1995;Nores * At the request of the authors, publication of this manuscript was postponed to July 2002. 1999), river hypothesis (rivers and their floodplains; Wallace 1852; Capparella 1988Capparella , 1991Ayres and Clutton-Brock 1992), disturbance-vicariance hypothesis (climatic cooling causing ecologically unsuitable habitat; Colinvaux 1993Colinvaux , 1996Colinvaux et al 1996), and refuge hypothesis (reduced precipitation causing forest fragmentation ;Haffer 1969;Simpson and Haffer 1978;Prance 1982a;Whitmore and Prance 1987).…”

Molecular systematics and phylogeography of Amazonian poison frogs of the genus Dendrobates

“…2. The Refuge Hypothesis has been investigated by a number of researchers and has been the focus of considerable debate (Brown, 1982;Froehlich et al, 1991;Nores, 1999;Prance, 1982;Prance, 1973;R€ a as€ a anen et al, 1991;Vanzolini, 1970). Duellman (1982) proposed a hypothesis similar to HafferÕs (1969) Refuge Hypothesis, but specific to anurans.…”

The historical biogeography of Pteroglossus aracaris (Aves, Piciformes, Ramphastidae) based on Bayesian analysis of mitochondrial DNA sequences

“…The above geological events we put forward as major vicariant forces driving the speciation among Pteroglossus aracaris are likely to have influenced the evolution of the Neotropical biota with comparable geographic distribution in tropical America (Bush, 1994;Nores, 1999Nores, , 2004Wesselingh and Salo, 2006). Similar patterns of temporal divergence have been independently suggested from molecular data for a growing number of congeneric species, including curassows and piping-guans (Grau et al, 2005;Pereira and Baker, 2004), parrots (Ribas et al, 2007), trogons (Moyle, 2005), monkeys (Collins and Dubach, 2001;Cortes-Ortiz et al, 2003), vesper mice and spiny rats (Galewski et al, 2005;Salazar-Bravo et al, 2001), bats (Lim, 2007;Stadelmann et al, 2007), catfishes (MontoyaBurgos, 2003), and geckos (Gamble et al, 2008).…”