Variação geográfica e dimorfismo sexual de Philander frenatus (Olfers, 1818), (Mammalia, Didelphimorphia: Didelphidae) através de morfometria geométrica craniana

• Autor(a) principal: González, Camilo Arias
• Data de Publicação: 2014
• Tipo de documento: Dissertação
• Idioma: por
• Título da fonte: LOCUS Repositório Institucional da UFV
• Texto Completo: http://locus.ufv.br/handle/123456789/2289
• topic: Didelphimorphia; Marsupial; Morfologia craniana; Variação geográfica; Dimorfismo sexual; Didelphimorphia; Marsupial; Cranial morphology; Geographic variation; Sexual dimorphism; CNPQ::CIENCIAS BIOLOGICAS::ZOOLOGIA

This study analyzes the morphological variation in the skull in Philander frenatus with regard to sexual size and sexual shape dimorphism of the skull, and to the geographic variation of Brazilian Atlantic Forest populations. A total of 290 adult individuals, consisting of 169 males and 120 females, were analyzed by geometric morphometric techniques using two- dimensional skull anatomical landmarks and Procrustes superimposition. Standardized photographs of the skull were taken in dorsal, ventral and lateral view, where 33, 34 and 29 anatomical landmarks were respectively digitized. Sexual size dimorphism was assessed by using centroid size as measurement. The values from the three views of the skull were compared by the t-test and all showed males as having larger skulls than females on average. Principal Component Analysis (PCA) and Discriminant Analysis (DA) were used to evaluate sexual shape dimorphism in the population with the largest number of individuals from the same locality and in the entire sample. Both analyses indicated similar results when assessed intrapopulationally and intraspecifically. Although the skull shape in males and females showed a great overlap in analyses of the three views, different variation trends were found for each sex. In general, male skulls had a shorter rostrum, higher zygomatic arch with a more prominent frontal process of the jugal bone, more developed sagittal crest and postorbital process, and a slightly narrower braincase. Two analyses were carried out for geographic variation. In one analysis individuals were grouped into four geographic clusters (Macrolocalities1): A - Atlantic Forest Central Corridor; B - Cerrado-Zona da Mata Corridor; C - Serra do Mar Corridor; and D - Cities of São Paulo (SP) State, and south of Goiás (GO) State and Paraná (PR) State. In the other analysis, they were grouped into eight subdivided geographic clusters (Macrolocalities2): A (A1, A2), B (B1, B2) and C (C1, C2, C3). Skull shape variation was evaluated separately for males and females by PCA in the three views and by Canonical Variate Analyses (CVA) in the three views for males, and in lateral view for females. No geographic morphological variation pattern was revealed in the three views evaluated or in the matrix of the three views pooled together in males or females using PCA. The CVA of ventral view was uninformative, but dorsal and lateral views showed similar trends of separation and overlap between geographical clusters in the CV axes. Both clustering typesindicated similar results and revealed a geographic pattern of skull morphological variation. An overlap was observed among geographical clusters of Serra do Mar Corridor (cluster C), Cerrado-Zona da Mata Corridor (cluster B) and Atlantic Forest Central Corridor (cluster A). The Cluster including the cities of SP, PR and south of GO (cluster D) showed a partial overlapping with cluster C, but demonstrated morphological variations that characterized it as far from the reference shape and discriminated it from cluster A. The CVA of the dorsal view indicated that main variations in the average skull shape of individuals from cluster D, as compared with the reference shape, were associated with premaxillary anteroposterior constriction, maxillary anterior expansion, slightly expanded zygomatic arch, and a posterior displacement of the parietal bones. The lateral-view analysis indicated that variations in the average skull shape from cluster D, constant in males and females, as compared with the average shape of the sample, were maxillary and pre-maxillary compression, indicating a slightly shorter rostrum. The divergence in morphological variation displayed by samples from the cities of SP, PR and south of GO might be due to some degree of isolation of populations, with them being far from the populations of the Serra do Mar, Cerrado-Zona da Mata and Atlantic Forest Central Corridors as well as different environmental pressures to the environmental heterogeneity of the biome.