Browsing by Subject "Malagasy rodents"

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Habitat use and morphological adaptations of endemic rodents (Muroidea: Nesomyinae) of East Madagascar
(2014) Marquart, Kathrin; Steidle, Johannes
In an adaptive radiation, Madagascar’s endemic rodents colonised a variety of different habitats. In this thesis, ecological and morphological aspects of the frequently sympatric nesomyines of East Madagascar were analysed. In the first part of the study, vegetation analyses were conducted in a model rainforest in East Madagascar and compared with species distribution to describe the species ecology. The results represent a preliminary ecological classification of the habitat use of nesomyines. In the second part of the study, the morphology of the hands and feet (chiridia) was correlated with ecological parameters and habitat use for the first time. Adaptive differentiations of the chiridia give evidence of a species’ ecological niche. Certain patterns of the volar integument, epidermal structures as well as length and area ratios are discussed in respect of their functional and ecological adaptive value. Seven endemic rodent species (Eliurus grandidieri, E. minor, E. tanala, E. webbi, Nesomys rufus, Gymnuromys roberti, Brachytarsomys albicauda) were trapped with live traps in different microhabitats. Ecological data and information on habitat structures were collected along five 1 km long trails. The specialised rodents were found in different ecological niches: on trees, lianas, underneath wood and thick roots, in dead wood or rotten logs. Some were found close to small rivers, some in humid valleys, whereas others seemed to prefer the higher mountain slopes or misty ridges, up to 1200 m a.s.l. Microhabitat analyses were conducted and trails where a species was significantly more abundant were compared with those where it was rare. The presence of an endemic rodent species was strongly connected with forest type, forest structure and vegetation density. In contrast, the deforested and cleared areas were species-poor. For the morphological studies, detailed microscopic drawings of the hands and feet were prepared of voucher specimens to be compared between the species. The chiridian structures differed clearly between the seven species. Slender hind feet with small thenar pads were significantly correlated with a terrestrial locomotion and a ground-dwelling ecology. Species with a predominantly arboreal locomotion exhibit large and prominent pads, covering a great area of the chiridian surface. Large-tree-climbers have larger pads in relation to foot size than bamboo-grass and small-branch-climbers which possess relatively longer feet with longer toes. Climbing on large trees needs good adhesive properties and climbing on grass or thin branches needs good grasping abilities. In conclusion, certain morphological structures of the rodents chiridia are evidence of a special way of life and foot-pad morphology in particular mirrors special adaptations to a species habitat. These adaptations are regarded as important to understand niche occupation, certain ecological aspects and locomotion forms of sympatric species. Thus, habitat preferences and special habitat requirements of the endemic nesomyines of East Madagascar could be analysed in details. In this thesis, it could be documented for the first time by the combination of these ecological and morphological results that the chiridian morphology allows to differentiate nesomyine taxa on ecological level.