Which Factors Determine Spatial Segregation in the South American Opossums (Didelphis aurita and D. albiventris)? An Ecological Niche Modelling and Geometric Morphometrics Approach

Didelphis albiventris and D. aurita are Neotropical marsupials that share a unique evolutionary history and both are largely distributed throughout South America, being primarily allopatric throughout their ranges. In the Araucaria moist forest of Southern Brazil these species are sympatric and they might potentially compete having similar ecology. For this reason, they are ideal biological models to address questions about ecological character displacement and how closely related species might share their geographic space. Little is known about how two morphologically similar species of marsupials may affect each other through competition, if by competitive exclusion and competitive release. We combined ecological niche modeling and geometric morphometrics to explore the possible effects of competition on their distributional ranges and skull morphology. Ecological niche modeling was used to predict their potential distribution and this method enabled us to identify a case of biotic exclusion where the habit generalist D. albiventris is excluded by the presence of the specialist D. aurita. The morphometric analyses show that a degree of shape discrimination occurs between the species, strengthened by allometric differences, which possibly allowed them to occupy marginally different feeding niches supplemented by behavioral shift in contact areas. Overlap in skull morphology is shown between sympatric and allopatric specimens and a significant, but weak, shift in shape occurs only in D. aurita in sympatric areas. This could be a residual evidence of a higher past competition between both species, when contact zones were possibly larger than today. Therefore, the specialist D. aurita acts a biotic barrier to D. albiventris when niche diversity is not available for coexistence. On the other hand, when there is niche diversification (e.g. habitat mosaic), both species are capable to coexist with a minimal competitive effect on the morphology of D. aurita

Unveiling the neuroanatomy of Josephoartigasia monesi and the evolution of encephalization in caviomorph rodents

Abstract Caviomorph rodents are an exceptional model for studying the effects of ecological factors and size relations on brain evolution. These mammals are not only speciose and ecologically diverse but also present wide body size disparity, especially when considering their fossil relatives. Here, we described the brain anatomy of the largest known rodent, Josephoartigasia monesi, uncovering distinctive features within this species regarding other taxa. Albeit resembling extant pacarana Dinomys branickii, J. monesi stands out due to its longer olfactory tract and well-developed sagittal sinus. Challenging the previous hypothesis that giant rodents possessed comparatively smaller brains, we found that J. monesi and another giant extinct rodent, Neoepiblema acreensis, are within the encephalization range of extant caviomorphs. This was unraveled while developing the a Phylogenetic Encephalization Quotient (PEQ) for Caviomorpha. With PEQ, we were able to trace brainsize predictions more accurately, accounting for species-shared ancestry while adding the extinct taxa phenotypic diversity into the prediction model. According to our results, caviomorphs encephalization patterns are not the product of ecological adaptations, and brain allometry is highly conservative within the clade. We challenge future studies to investigate caviomorphs encephalization within different taxonomic ranks while increasing the sampled taxa diversity, especially of extinct forms, in order to fully comprehend the magnitude of this evolutionary stasis. Keywords Adaptive regimes · Allometric trends · Brain evolution · Cranial endocast · South Americ

Procrustes ANOVA results analyzing the skull shape variation in Didelphis according to: species (<i>D</i>. <i>albiventris</i> and <i>D</i>. <i>aurita</i>), sex, geography (allopatric and sympatric) and size (natural logarithm of centroid size).

<p>Procrustes ANOVA results analyzing the skull shape variation in Didelphis according to: species (<i>D</i>. <i>albiventris</i> and <i>D</i>. <i>aurita</i>), sex, geography (allopatric and sympatric) and size (natural logarithm of centroid size).</p

Boxplot showing the difference in natural log centroid size (lnCS) between males and females of <i>Didelphis albiventris</i> and <i>D</i>. <i>aurita</i>.

<p>Boxplot showing the difference in natural log centroid size (lnCS) between males and females of <i>Didelphis albiventris</i> and <i>D</i>. <i>aurita</i>.</p

Scatter plot of RW1 versus RW2.

<p>Transformation grids visualize shape deformations relative to the mean at the positive and negative extremes of Relative Warps axes. Males and females from each species are labeled according to different colors within minimum convex hull superimposed. Allopatric and sympatric specimens are discriminated with unfilled and filled symbols respectively.</p

Schematic depiction of the factors analyzed in variation partition meant to illustrate both their individual contribution to <i>Didelphis</i> shape and their interaction components.

<p>A) <i>Didelphis</i> genera; B) <i>D</i>. <i>aurita</i>; C) <i>D</i>. <i>albiventris</i>.</p

Disposition of 25 landmarks on a skull of <i>Didelphis albiventris</i> specimen.

<p>1 = midpoint of central incisors; 2 = posterior-most point of lateral incisor alveolus; 3–5 = canine area; 5–7 = pre-molar series length; 6–8 = first molar area; 9–11 = second molar area; 12–14 = third molar area; 15–17 = fourth molar area; 18–21 = temporal muscle insertion area; 22 = most posterior tip of the palatine; 23–25 = occipital condyle area.</p

NEOTROPICAL CARNIVORES: a data set on carnivore distribution in the Neotropics

Mammalian carnivores are considered a key group in maintaining ecological health and can indicate potential ecological integrity in landscapes where they occur. Carnivores also hold high conservation value and their habitat requirements can guide management and conservation plans. The order Carnivora has 84 species from 8 families in the Neotropical region: Canidae; Felidae; Mephitidae; Mustelidae; Otariidae; Phocidae; Procyonidae; and Ursidae. Herein, we include published and unpublished data on native terrestrial Neotropical carnivores (Canidae; Felidae; Mephitidae; Mustelidae; Procyonidae; and Ursidae). NEOTROPICAL CARNIVORES is a publicly available data set that includes 99,605 data entries from 35,511 unique georeferenced coordinates. Detection/non-detection and quantitative data were obtained from 1818 to 2018 by researchers, governmental agencies, non-governmental organizations, and private consultants. Data were collected using several methods including camera trapping, museum collections, roadkill, line transect, and opportunistic records. Literature (peer-reviewed and grey literature) from Portuguese, Spanish and English were incorporated in this compilation. Most of the data set consists of detection data entries (n = 79,343; 79.7%) but also includes non-detection data (n = 20,262; 20.3%). Of those, 43.3% also include count data (n = 43,151). The information available in NEOTROPICAL CARNIVORES will contribute to macroecological, ecological, and conservation questions in multiple spatio-temporal perspectives. As carnivores play key roles in trophic interactions, a better understanding of their distribution and habitat requirements are essential to establish conservation management plans and safeguard the future ecological health of Neotropical ecosystems. Our data paper, combined with other large-scale data sets, has great potential to clarify species distribution and related ecological processes within the Neotropics. There are no copyright restrictions and no restriction for using data from this data paper, as long as the data paper is cited as the source of the information used. We also request that users inform us of how they intend to use the data