Geography Reference
In-Depth Information
tacean, insect (Coleoptera and Trichoptera), and arachnid taxa (Crother and Guy-
er 1996) showed the close relationship between the Cuba, Hispaniola, and Puerto
Rico provinces. The Northwestern South American dominion comprises eleven
provinces: Chocó, Maracaibo, Venezuelan Coast, Trinidad and Tobago, Mag-
dalena, Venezuelan Llanos, Cauca, Western Ecuador, Arid Ecuador, Tumbes-
Piura, and Galápagos Islands.
The Amazonian is the largest subregion of the Neotropical region, extending
to Brazil, the Guyanas, Venezuela, Colombia, Ecuador, Peru, Bolivia, Paraguay,
and Argentina. Thirteen provinces are assigned to the Amazonian subregion:
Napo,Imeri,Guyana, HumidGuyana, Roraima,Amapa, Varzea,Ucayali,Madeira,
Tapajos-Xingu, Para, Pantanal, and Yungas. Several PAEs and cladistic biogeo-
graphic analyses have reconstructed the relationships between Amazonian
provinces (Amorim and Pires 1996; Cracraft and Prum 1988; Hall and Harvey
2002; Patton et al. 2000; Racheli and Racheli 2004; Ron 2000; da Silva and Oren
1996), but there is little agreement between the alternative hypotheses. A recent
cladistic biogeographic analysis (Nihei and Carvalho 2007) suggested that the
Amazonian subregion may be a composite area.
The Chacoan subregion occupies northern and central Argentina, southern
Bolivia, western and central Paraguay, Uruguay, and central and northeastern
Brazil. Evidence of a “savanna corridor” or “diagonal of open formations” (Prado
and Gibbs 1993) led to the hypothesis that the Cerrado province, formerly as-
signed to the Amazonian domain, connected the Caatinga with the other Chacoan
provinces. The Chacoan subregion is closely related to the Amazonian and
Parana subregions. The development of the Chacoan subregion during the Ter-
tiary split the former continuous Amazonian-Parana forest, representing an ex-
ample of dynamic vicariance (Zunino 2003). Some insect taxa show the Amazo-
nian-Parana disjunction, whereas others, which probably belong to a more recent
cenocron, are found in both the Chacoan and Parana subregions. A phylogeo-
graphic analysis of small mammal species (Costa 2003) showed that the central
Braziliangalleryanddryforestsplayanimportantroleaspresentandpasthabitats
for forest species from the Amazonian and Parana subregions. Populations of
Chacoan mammals have their closest relatives in the Amazonian subregion or
in the Parana subregion or are basal to both subregions. Four provinces are as-
signed to the Chacoan subregion: Caatinga, Cerrado, Chaco, and Pampa.
The Parana subregion is situated in northeastern Argentina, eastern Paraguay,
and southern and eastern Brazil. In addition to its relationships with the other
Neotropical subregions, several authors have discussed its relationships with the
Subantarctic subregion. Paleontological, paleoclimatological, and geological evid-
ence indicates that a temperate climate prevailed in southern South America dur-
ing the Tertiary, allowing the existence of a continuous cloud forest that extended
further south than today. Cooling and aridification began in the Oligocene and Mio-
cene, and later the forest fragmented simultaneously with the climatic changes in-
 
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