Geographic variation of wing morphology of great fruit-eating bats (Artibeus lituratus): environmental, genetic and spatial correlates of phenotypic differences

Wings of fringed fruit-eating bats (Artibeus fimbriatus) are highly integrated biological aerofoils from perspectives of secondary sexual dimorphism, allometry and modularity

Phenotypic variability is ubiquitous. This is especially true in bats, where families such as Phyllostomidae encompass as much phenotypic variability as some entire orders of mammals. Typically, phenotypic variability is characterized based on cranial morphology, with studies of other functionally important aspects of the phenotype, such as legs, feet and wings, being less frequent. We examined patterns of secondary sexual dimorphism and allometry of wing elements of the fringed fruit-eating bat (Artibeus fimbriatus) and examined, for the first time, the modularity of bat wings. Patterns were based on 13 wing measurements taken from 21 females and 15 males from eastern Paraguay. From a multivariate perspective, A. fimbriatus exhibited significant secondary sexual dimorphism. Females were larger than males for all 13 wing characteristics, with significant differences involving the last phalanx of the fourth and fifth digits. Female wings were also relatively larger than male wings from a multivariate perspective, as was the last phalanx of the fourth and fifth digits, after adjusting for wing size based on forearm length. Wing elements were highly variable regarding allometric relationships, with some exhibiting no allometric patterns and others exhibiting isometry or hyperallometry, depending on the element. Wings exhibited significant modularity, with metacarpals, proximal phalanges and distal phalanges each representing a discrete module. The wings of A. fimbriatus exhibit substantive patterns of dimorphism, allometry and modularity. Although the big mother hypothesis is a strong theoretical construct to explain wing dimorphism, there is not yet any sound theoretical basis for the patterns of allometry and modularity of the wing. Further investigation is required to understand the determinants of variation in wing morphology.

The interplay of spatial scale and landscape transformation modulates the abundance and intraspecific variation in the ecomorphological traits of a phyllostomid bat

Land use intensification imposes selective pressures that systematically change the frequency of wild population phenotypes. Growing evidence is biased towards the comparison of populations from discrete categories of land uses, ignoring the role of landscape emerging properties on the phenotype selection of wild fauna. Across the largest urban–rural gradient of the Colombian Orinoquia, we measured ecomorphological traits of 216 individuals of the flat-faced fruit-eating bat Artibeus planirostris. We did this to evaluate the scale of effect at which landscape transformation better predicts changes in phenotype and abundance of an urban-tolerant species. Forest percentage at 1.25 km was the main predictor affecting negatively bat abundance and positively its wing aspect ratio and body mass. Landscape variables affected forearm length at all spatial scales, this effect appeared to be sex-dependent, and the most important predictor, forest percentage at 0.5 km, had a negative effect on this trait. Our results indicate that landscape elements and spatial scale interact to shape ecomorphological traits and the abundance of A. planirostris. Interestingly, the scale of effect coincided at 1.25 km among all biological responses, suggesting that species’ abundance can be linked to the variation on phenotype under different environmental filters across landscape scenarios.

Inter- and intraspecific variation in the Artibeus species complex demonstrates size and shape partitioning among species

Neotropical leaf-nosed bats (family Phyllostomidae) are one of the most diverse mammalian families and Artibeus spp. is one of the most speciose phyllostomid genera. In spite of their species diversity, previous work on Artibeus crania using linear morphometrics has uncovered limited interspecific variation. This dearth of shape variation suggests that differences in cranial morphology are not contributing to niche partitioning across species, many of which are often found in sympatry. Using two-dimensional geometric morphometric methods on crania from eleven species from the Artibeus species complex, the current study demonstrates substantial cranial interspecific variation, sexual size and shape dimorphism, and intraspecific geographic variation. The majority of species were shown to have a unique size and shape, which suggests that each species may be taking advantage of slightly different ecological resources. Further, both sexual size and shape dimorphism were significant in the Artibeus species complex. Male and female Artibeus are known to have sex specific foraging strategies, with males eating near their roosts and females feeding further from their roosts. The presence of cranial sexual dimorphism in the Artibeus species complex, combined with previous work showing that different fruit size and hardness is correlated with different cranial shapes in phyllostomids, indicates that the males and females may be utilizing different food resources, leading to divergent cranial morphotypes. Additional field studies will be required to confirm this emergent hypothesis. Finally, significant geographical shape variation was found in a large intraspecific sample of Artibeus lituratus crania. However, this variation was not correlated with latitude and instead may be linked to local environmental factors. Additional work on ecology and behavior in the Artibeus species complex underlying the morphological variation uncovered in this study will allow for a better understanding of how the group has reached its present diversity.