Impacts of forest fragmentation on small mammals in the southern Amazonia : A geometric morphometric approach

• Autor(a) principal: Castilheiro, Welvis Felipe Fernandes
• Data de Publicação: 2019
• Idioma: eng
• Título da fonte: Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos)
• Texto Completo: http://hdl.handle.net/10451/48533
• topic: Amazonia; pequenos mamiferos; morfometria geometrica; mandibula; alterações morfológicas; small mammals; mandible; morphological alterations; geometric morphometrics; Domínio/Área Científica::Ciências Naturais::Ciências Biológicas

Habitat loss and fragmentation have long been recognized as major drivers of biodiversity depletion. In Amazonia, forest fragmentation constitutes a major cause of environmental stress for many organisms. Here, we addressed the effects of differential fragment sizes on the mandible phenotype of four species of small mammals (Proechymis longicaudatus, Necromys lasiurus, Micoureus demerarae and Monodelphis glirina) using a geometric morphometry approach. This technique allowed to address: i) the symmetrical component, assessing population variation in shape and size; ii) fluctuating asymmetry, inferring disturbance during embryonic development; iii) morphological integration and modularity, allowing to identify deviations in the mandible’s morphological structure. The study area encompasses a hyper-fragmented area in southern Amazonia, characterised by forest landscape surrounded by pasture, with some highly isolated patches. Sampling and data collection were performed in 17 forest fragments grouped according to size: ten small fragments (4-26 hectares), seven large fragments (106-1763 hectares), and two surrounding areas of continuous forest (C≥30,000 hectares). Our results reveal that morphometric distances between groups of animals inhabiting different sized fragments are significantly higher when pairwise comparison involve small fragments. Fluctuating asymmetry was also significantly higher in small fragments but only for both species of larger body size (long- tailed spiny rat, P. longicaudatus, and woolly mouse opossum, M. demerarae). More isolated fragments were positively correlated with higher fluctuating asymmetry levels, although not significantly. Finally, in small fragments, changes in the expected pattern of modularity and morphological integration were also detected for all but one study species (M. demerarae), with putative consequences for the structure and morphological functionality of individuals. Based on empirical morphological data, we highlight the need for the maintenance of large forest patches as repositories of somewhat similar levels of morphological diversity and functionality in contrast with small fragments, where most deleterious effects were detected.