Abstract
Dietary characteristics and environmental variables are important selective factors directing ecological diversification in rodents. On Madagascar, the introductions and spread of the commensal black rat (Rattus rattus) can be seen as example cases to study dietary niche occupation and dietary adaptation in an insular environment. We investigate how tooth wear as a measure of dietary adaptation of black rats differs between four distinct habitats (village, manioc fields, spiny forest, and rainforest) with different dietary resources. We use the 3D surface texture analysis (3DST, using 30 parameters according to ISO 25178) as a measure of dietary abrasiveness. 3DST is applied on the occlusal surface of the upper first molar of 37 black rat specimens. The rainforest sample displays less rough and less voluminous surface textures compared to the village samples as indicated by smaller values for height parameters (Sa, Sp, Sq), inverse areal material ratio (Smc), and volume parameters (Vm, Vmc, Vmp, Vv, and Vvc). We therefore rank sampling areas from highest to lowest abrasiveness (village>manioc fields/spiny forest>rainforest). The rats from villages and rainforest differ to such an extent that one could have interpreted them to belong to different species. This indicates a high degree of variability in terms of ingesta abrasiveness. Furthermore, the pronounced difference between rats from human habitations compared to rats from associated fields or natural vegetation is interpreted to clearly indicate shifts in dietary niche occupation in relation to human impact.
Highlights
Dietary characteristics and environmental variables are important selective factors directing ecological diversification in small mammals
Ecology and Evolution published by John Wiley & Sons Ltd
Black rats from the rainforest have significantly different surface textures compared to black rats from the villages, a 2016 The Authors
Summary
Dietary characteristics and environmental variables are important selective factors directing ecological diversification in small mammals. Mechanical characteristics of the diet, that is hard vs soft foods, have been found to influence mandible shape in experimental set-ups in domestic house mice (Renaud and Auffray 2010), and rats (Yamada and Kimmel 1991; Maki et al 2002; Levrini et al 2003). Such experimentally obtained phenotypic plasticity suggests the possibility of rapid evolution in natural populations under increased selective pressure.
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