NEOTROPICAL XENARTHRANS: a data set of occurrence of xenarthran species in the Neotropics

Xenarthrans – anteaters, sloths, and armadillos – have essential functions for ecosystem maintenance, such as insect control and nutrient cycling, playing key roles as ecosystem engineers. Because of habitat loss and fragmentation, hunting pressure, and conflicts with 24 domestic dogs, these species have been threatened locally, regionally, or even across their full distribution ranges. The Neotropics harbor 21 species of armadillos, ten anteaters, and six sloths. Our dataset includes the families Chlamyphoridae (13), Dasypodidae (7), Myrmecophagidae (3), Bradypodidae (4), and Megalonychidae (2). We have no occurrence data on Dasypus pilosus (Dasypodidae). Regarding Cyclopedidae, until recently, only one species was recognized, but new genetic studies have revealed that the group is represented by seven species. In this data-paper, we compiled a total of 42,528 records of 31 species, represented by occurrence and quantitative data, totaling 24,847 unique georeferenced records. The geographic range is from the south of the USA, Mexico, and Caribbean countries at the northern portion of the Neotropics, to its austral distribution in Argentina, Paraguay, Chile, and Uruguay. Regarding anteaters, Myrmecophaga tridactyla has the most records (n=5,941), and Cyclopes sp. has the fewest (n=240). The armadillo species with the most data is Dasypus novemcinctus (n=11,588), and the least recorded for Calyptophractus retusus (n=33). With regards to sloth species, Bradypus variegatus has the most records (n=962), and Bradypus pygmaeus has the fewest (n=12). Our main objective with Neotropical Xenarthrans is to make occurrence and quantitative data available to facilitate more ecological research, particularly if we integrate the xenarthran data with other datasets of Neotropical Series which will become available very soon (i.e. Neotropical Carnivores, Neotropical Invasive Mammals, and Neotropical Hunters and Dogs). Therefore, studies on trophic cascades, hunting pressure, habitat loss, fragmentation effects, species invasion, and climate change effects will be possible with the Neotropical Xenarthrans dataset

A geometric morphometric analysis of cranial and mandibular shape variation of didelphid marsupials

<strong>Abstract</strong> The New World marsupial family Didelphidae is one of the oldest among mammals and is usually regarded as a morphologically conservative group. We analyzed cranial shape variation among six species of the six largest living genera of the family using two-dimensional landmark data. We captured and digitized video images of the skull and mandible for the following species: <em>Caluromys philander</em> (n = 65), <em>Chironectes minimus</em> (n = 30), <em>Didelphis aurita</em> (n = 70), <em>Lutreolina crassicaudata</em> (n = 37), <em>Metachirus nudicaudatus</em> (n = 77) and <em>Philander frenata</em> (n = 62). Fourteen landmarks were defined for the lateral, 25 for the ventral, 23 for the dorsal views of the skull, and nine on the mandibular lateral view. Sex, species, and interaction effects were analyzed with a two-way MANOVA on the matrices of coordinates aligned by general least squares. All four views had significant interactions. Canonical Variates Analysis was performed on sexes and species, and shape was regressed on the canonical variate scores for each species. <em>Caluromys philander</em> was clearly the most distinct species, with paedomorphic features that can be related to its arboreal habits. A conspicuous shortening of the rostrum distinguishes the highly carnivorous <em>Lutreolina crassicaudata</em>. <em>Didelphis aurita</em> and <em>Philander frenata</em> overlapped somewhat, reflecting shape similarities associated with their phylogenetic affinities, while the few differences observed are probably allometric consequences of size differences. <em>Philander frenata</em> and <em>Chironectes minimus</em> showed similar cranial shapes, while <em>Metachirus nudicaudatus</em> was distinctive with a broad and elongated rostrum. In spite of an overall similar shape, the geometric morphometric approach revealed several marked differences among species that can be related to their phylogenetic origin and their adaptive zone

Peramorphic males and extreme sexual dimorphism in Monodelphis dimidiata (Didelphidae)

The southern short-tailed opossum, Monodelphisdimidiata, is a species known not only for its semelparouslife cycle, but also for the extreme sexualdimorphism of adults, where males are not only larger, butalso have distinctive morphological characters in theirskull. Using geometric morphometrics and a suite of statisticaltests, I analyzed the postweaning ontogeneticdevelopment of this species in order to evaluate the ageclasswhere sexual dimorphism becomes significant and theamount of change exhibited by both sexes. My resultsshowed that M. dimidiata partly follows the ontogeneticpattern described for didelphids by previous authors. Thecharacter that escapes the general pattern is rostral length,which becomes shorter instead of lengthening throughoutthe development. This change could be related to anincrement in the bite force in the anterior part of the dentition.The amount of sexual dimorphism found for thisspecies is larger than the reported previously for otherAmerican marsupials, and I also found a higher rate ofgrowth in males at the attaining of sexual maturity. Basedon my results and the information available for otherdidelphids, I can suggest that M. dimidiata males undergothrough a process of hypermorphosis, resulting in aperamorphic condition. It is possible that the extremesexual dimorphism present in this species is related toreproductive success, specially taking into account theirsemelparous life cycle.Fil: Chemisquy, Maria Amelia. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales "Bernardino Rivadavia"; Argentin

Diet of the gracile mouse opossum Gracilinanus agilis (Didelphimorphia: Didelphidae) in a neotropical savanna: intraspecific variation and resource selection.

Investigation of the effect of endogenous and exogenous factors on the diet of animals is necessary for a better understanding of their feeding habits. This approach can provide relevant information on the autoecology of a species and its ecological interactions. We investigated the composition and intraspecific variation in the diet of the marsupial Gracilinanus agilis in areas of dry woodland forests (i.e., cerradão) in the Cerrado of Central Brazil, taking into consideration the availability of prey (arthropods) in the environment. We found insects, spiders, birds, and fruits in the scats of G. agilis. Insects (orders Hymenoptera, Isoptera, Hemiptera, and Coleoptera) and fruits were the most frequently consumed resources. Males fed more heavily on insects than females did, whereas during the warm?wet season (October to April), the reproductive females fed on insects more than the nonreproductive females did. On the other hand, the consumption of fruits and vertebrates did not vary between seasons, sexes, or according to female reproductive condition. Moreover, reproductive females fed more frequently on ants and beetles than nonreproductive females did. We also detected both positive (for Isoptera and Hemiptera) and negative (for Hymenoptera) selection of insects during the cool?dry season, whereas in the warm?wet season, these resources were consumed according to their availability in the environment. Our study revealed that G. agilis is an insectivore?omnivore species, but fruits also are a relevant part of its diet. This marsupial seemed to select their prey qualitatively according to its energy demands and nutritional requirements