Population genetic analysis of Caiman crocodilus (Linnaeus, 1758) from South America

Abstract

The genetic structure of Caiman crocodilus was investigated using a 1085 bp mtDNA fragment of the cytochrome b gene. Inferences were based on 125 individuals from nine localities in Peru, Brazil and French Guiana. With the exception of Mamirauá Lake, Anavilhanas Archipelago and the Tapará Community which show a signal of demographic expansion, the sampled localities are in a mutation-drift genetic equilibrium. Divergence between the Amazon basin and extra-Amazon basin localities is significant; however, inference from Nested Clade Analysis cannot distinguish between continuous range expansion, long distance colonization or past fragmentation; however, past fragmentation is unlikely due to low number of mutational steps separating these two regions. The divergence is probably maintained by the reduced ability of C. crocodilus to cross salt water barriers. Within the Amazon basin, continuous range expansion without isolation-by-distance is the most likely process causing genetic structuring. The observed genetic patterns are compatible with the ecology of C. crocodilus, and history of human exploitation. As commercial hunting depleted more valuable species, C. crocodilus expanded its range and ecological niche, prompting hunters to harvest it. Following a period of intense hunting, C. crocodilus is now experiencing recovery and a second population expansion especially in protected areas.

Phylogeographic and conservation genetic analysis of the black caiman (Melanosuchus niger)

“…Thus, these two areas are hydrologically separated, and their respective M. niger populations appear to be genetically differentiated. Genetic differentiation observed between localities from Atlantic drainages and those from the Amazon River Basin corroborates a hypothesis of vicariant differentiation previously proposed by Vasconcelos et al (2006) for C. crocodilus. The salt water of the Atlantic Ocean is inferred to function as a physical barrier for the dispersal for this species in a similar way that salt water is a barrier to dispersal for other alligatorids owing to their inability to excrete excess salt (Taplin and Grigg,'89).…”

“…Ray et al, 2004). A similar geographic sampling of the spectacled caiman also does not show significant correlation between geographic and genetic distance even across 3,070 km sampling range (r 5 0.4621, P 5 0.058; Vasconcelos et al, 2006). However, even for the black caiman, significant correlation between genetic and geographic distances is observed only at large geographic distances; the correlation does not exist among localities within the Amazon Basin.…”

Conservation strategies for Arapaima gigas (Schinz, 1822) and the Amazonian várzea ecosystem

“…Wagler 1830) also form an important and conspicuous component of the várzea ecosystem as does the Amazonian manatee (Trichechus inunguis (Natterer, 1883)). As far as examined (Farias et al, 2004;Cantanhede et al, 2005;Pearse et al, 2006;Vasconcelos et al, 2006;Santos et al, 2007) all of these large and economically important species have a genetic structure similar to that of Arapaima gigas. Therefore the designation of várzea reserves on the scale suggested for Arapaima is likely to benefit other important members of the várzea ecosystem of the Amazon basin.…”

Poblaciones de babillas (caiman crocodilus) y caimán negro (melanosuchus niger) en la reserva biológica del abufari, amazonas, Brasil

“…The PPSDR could become the "sink" for the ABR "source" of caimans, given that the areas are adjacent and gene flow is possible between them (FARIAS et al, 2004;VASCONCELOS et al, 2006). Therefore, we suggest that a detailed study be undertaken in the Abufari Biological Reserve and the PPSDR, and that an integrated committee discuss the management program of caimans in the lower Purus River.…”