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Knowledge of Didelphidae taxonomy and diversity has increased steadily over the last decades, mainly due to increasing collection efforts and revisionary works. Yet, especially for mouse opossums, a proper appraisal of morphological variation is still incipient. Thylamys karimii occurs in the Brazilian biomes of Caatinga and Cerrado, and specimens with two different shades of dorsal coloration (brown and gray) were recently documented in sympatry in the Parque Nacional (PARNA) do Catimbau (Caatinga biome). We used qualitative and morphometric data from skulls and skins (n = 7 from PARNA Catimbau and n = 26 from other localities) to compare these two coat color morphotypes and characterize the morphological diversity and taxonomic status of the Caatinga populations. We used Student's t-tests to compare sexes and morphotypes' measurements. We found at least three well-defined coat color morphotypes distinguishable by dorsal and ventral coloration and not restricted to PARNA Catimbau. Variation of the other morphological traits suggests that these morphotypes are more likely a case of intraspecific variation in the Brazilian northeastern region. Morphometric differences, particularly between coat color morphotypes, might be better elucidated in larger samples. Additionally, these specimens represent an important extension of the species' known distribution reaching the Atlantic Forest borders. [ABSTRACT FROM AUTHOR]

Opossums (marsupials of the Didelphidae family) retain a generalized masticatory apparatus and tribosphenic molars, often used as models to understand the evolution of mastication in early therian mammals. Like all marsupials, their growth goes through a stage when pups complete their development while permanently attached to the mother's teats before weaning and starting feeding on their own. Yet, while the masticatory muscles of adults are known, as is the ontogeny of the cranium and mandible, the ontogenetic changes in the masticatory muscles remain unknown. Here we describe for the first time the changes in the masticatory muscles observed in lactating pups, and weaned juveniles, subadults, and adults in the White‐eared opossum, Didelphis albiventris, through dissection of 25 specimens and quantification of relative muscle masses, lines of actions and mechanical advantages whenever possible. We also assessed the scaling patterns of muscle masses and mechanical advantages through ontogeny. The main changes, as expected, were found between suckling and weaned specimens, although some changes still occurred from juveniles to adults. The adult adductor musculature is similar to the other Didelphis species already known, with a dominant m. temporalis that originates on the lateral wall of the skull, up to the sagittal and nuchal crests, and fills the zygomatic arch when inserting into the lateral and medial surfaces of the coronoid process, respectively through the pars superficialis and pars profunda. The m. masseter is also subdivided in superficial and deep bundles which originate posteriorly in the maxilla and zygomatic arch, and insert into the angular process and masseteric fossa in the mandible. The m. pterygoideus medialis originates from the palatine, the pterygoid bone and the alisphenoid, and it inserts on the angular process medially. Suckling pups showed muscles with more restricted attachments, reduced muscle lines of action, and less diversity in the fiber orientation. The absence of the postorbital constriction also resulted in a distinct morphology of the m. temporalis pars profunda, through two bundles, one anterior and one posterior, which insert more inferiorly into the mandible. These major changes can be related to the onset of mastication and to size‐related changes in growing weaned age classes. In general, all adductor muscles grew with positive allometry, and increased their fixation areas through, in part, the development of specific regions of the cranium and mandible. Their lines of action also increase and diversify along ontogeny. These changes can be related to the functional requirements for fixation during lactation, which shift to adduction and mastication movements after weaning. [ABSTRACT FROM AUTHOR]

Environmental pressures challenge the survivorship of wildlife, and adaptive ability is key to their success and establishment. However, it remains unclear how changes in environmental conditions affect the phenotypic plasticity of some species. Studies that consider the effect of the environment (e.g., climate changes) on species morphology are essential to better understand his potential resilience. Thus, Diptera species appear as an excellent model. Here we investigated the effect of environmental conditions on wing size and shape within and between one native and one invasive blowfly species populations, along an ecoregional gradient in Brazil. For native species, wing size was affected by almost all environmental variables, while wing shape was unaffected. For invasive species, humidity best explained both wing size and wing shape variation. Our results show a differentiation between populations for both species, but a transversal comparison reveals that invasive species do not seem to be affected in the same way as the native species by climatic variations in the field. Temperature and humidity are the most significant environmental variables associated with differences in wing size and shape for invasive species, indicating an elevated climate tolerance of this species, which may be associated with its invasive characteristics and adaptive potential. Thus, our findings shed light on the importance of assessing the individual and compound effect of environmental variation and biological invasion on the adaptation of native species, since it is expected to increase 3 °C with a 20% overall reduction in the amount of rainfall in the tropical region of Brazil by 2100. [ABSTRACT FROM AUTHOR]

Adoption by an alloparent of an offspring or a litter occurs in at least eight mammal orders, but is rare in marsupials, and was never confirmed in opossums. Here we report the first unequivocal and documented successful event of alloparental adoption of two distinct litters by a single captive female Southern Black-eared Opossum Didelphis aurita (Didelphimorphia, Didelphidae). The female, still nursing her biological litter, accepted and nursed the two offered litters. All three litters were raised simultaneously, and the female cared for and displayed protective behaviour indistinctively of the biological or adopted pups. She was kept captive until released along with her biological litter, which was weaned and fled independently, and the two adoptive litters clinging on her back. This event sheds additional light on the little known social and maternal behaviour of opossums, suggesting it is possibly more complex than originally thought. [ABSTRACT FROM AUTHOR]

Didelphid marsupials are considered a morphologically unspecialized group with a generalist diet that includes vertebrates, invertebrates, and plant matter. While cranium and scapula variation has already been examined within Didelphidae, variation in mandible shape, usually associated with diet or phylogeny in other mammalian groups, has not yet been properly assessed in the family. We evaluated the variation in mandible shape and size of didelphids (2470 specimens belonging to 94 species) using 2D geometric morphometrics. We classified the diet of the didelphids into four broad categories to assess whether morphospace ordination relates to dietary habits. We also provided the most comprehensive phylogeny for the family (123 out of the 126 living species) using 10 nuclear and mitochondrial genes. We then mapped mandible size and shape onto that phylogeny for 93 selected taxa and ancestral size and shapes were reconstructed by parsimony. We found phylogenetically structured variation in mandible morphology between didelphid groups, and our results indicate that they have a significant phylogenetic signal. The main axis of shape variation is poorly related to size, but the second is strongly allometric, indicating that allometry is not the main factor in shaping morphological diversity on their mandibles. Our results indicate that the shape and size of the ancestral mandible of didelphids would be similar to that of the current species of the genus Marmosa. [ABSTRACT FROM AUTHOR]

Usually considered a morphologically conservative group, didelphid marsupials present considerable variation in ecology and body size, some of which were shown to relate to morphological structures. Thus, changes on orbit morphology are likely and could be related to that variation. We calculated orbit orientation in 873 specimens of 16 Didelphidae genera yielding estimates of orbits convergence (their position relative to midsagittal line) and verticality (their position relative to frontal plane). We then compared similarities in these variables across taxa to ecological, morphological and phylogenetic data to evaluate the influencing factors on orbit orientation in didelphids. We found an inverse relation between convergence and verticality. Didelphids orbits have low verticality but are highly convergent, yet orbit orientation differs significantly between taxa, and that variation is related to morphological aspects of the cranium. Rostral variables are the only morphological features correlated with orbit orientation: increasing snout length yields more convergent orbits, whereas increase on snout breadth imply in more vertical orbits. Size and encephalization quotients are uncorrelated with orbit orientation. Among ecological data, diet showed significant correlation whereas locomotion is the factor that less affects the position of orbits. Phylogeny is uncorrelated to any orbital parameters measured. Ecological factors seemingly play a more important role on orbit orientation than previously expected, and differentiation on orbit orientation seems to be more functional than inherited. Thus, despite the apparent homogeneity on didelphid morphology, there is subtle morphological variability that may be directly related to feeding behavior. [ABSTRACT FROM AUTHOR]

The Water Opossum, Chironectes minimus (Didelphimorphia, Didelphidae), is the only semi-aquatic marsupial and can be easily identified for its uniquely patterned water resistant pelage and webbed hind-feet. The species is distributed along the Neotropical region (from Southern Mexico to Northwestern Argentina) and is currently divided on four subspecies ( C.   m. argyrodytes, C. m. panamensis, C. m. minimus, C. m. paraguensis ), based on its geographical distribution. We evaluated the geographic variation in C. minimus , using traditional and geometric morphometrics techniques to capture the size and shape of the skull to identify differences between the populations that could relate to existing subpsecies or populations that and would merit particular taxonomic attention. We took 13 skull measurements, and digitized 37, 18, and 23 2D landmarks on the dorsal and lateral view of the cranium and on the lateral view of the mandible, respectively. The sample consisted on 135 individuals from 66 localities. Analyses of both datasets showed that the Southern South America and Northern Central America animals differ from the other populations. Geometric morphometrics shows on the three views that the Amazon animals differ from the others probably due to existing geographical barriers. These morphological differences among populations of the Water Opossum support the need for a proper phylogenetic assessment of these populations, in order to clarify their taxonomic status. [ABSTRACT FROM AUTHOR]

We analyzed the geographic variations in the shape and size of the cranium and mandible of two woolly opossums, Caluromys derbianus and Caluromys lanatus. Using geometric morphometrics we analyzed 202 specimens of C. derbianus and 123 specimens of C. lanatus, grouped in 7 and 9 populations, respectively. We found sexual dimorphism in shape variables only in the dorsal view of the cranium of Caluromys derbianus, which is not associated with geographical origin. We detected geographic variation in the size of the mandible in two populations (Nicaragua and Northern Panama), but no geographic variation in shape. The size of the cranium of C. lanatus varies significantly, with clinal variation in peri-Amazon populations, with a break between two populations, Bolivia and Paraguay. Shape analyses also revealed some separation between the Paraná population and all other populations. Our results suggest that the available name, Caluromys derbianus, should be maintained for all individuals throughout the geographic range of the species. The same is true for Caluromys lanatus, which can be separated into two distinct morphologic units, Caluromys lanatus ochropus, from the Amazon and Cerrado, and Caluromys lanatus lanatus, from the Atlantic forest. [ABSTRACT FROM AUTHOR]

This study assessed the occurrence of sexual size dimorphism (SSD) and sexual shape dimorphism (SShD) in the skull and mandible of representatives of most species within the 3 orders of living New World opossums, Didelphimorphia, Paucituberculata, and Microbiotheria, using geometric morphometrics. Centroid sizes and partial warps were extracted from landmarks set on images of the dorsal, ventral, and lateral views of the skull and lateral view of the mandible, and were compared between sexes to estimate SSD and SShD. Specimens totaling 2,932 from 71 species of Didelphidae, 5 species of Caenolestidae, and 1 species of Microbiotheriidae were analyzed. SSD was variable in the Didelphimorphia and the Paucituberculata and absent in Microbiotheria. Similar results were found for SShD, but SSD and SShD are not clearly coupled. I also evaluated the validity of Rensch's rule--the widely observed phenomenon of correlated increases in SSD and body size for male-biased sexual dimorphism, or correlated decreases in SSD in body size for female-biased sexual dimorphism--in the Didelphidae. Didelphids span 2 orders of magnitude in body size, and, when present, sexual dimorphism is male-biased. Regressions of SSD and SShD estimators onto size, using phylogenetic independent contrasts, showed either no significant relationship between SSD or SShD with size in any of the structures and views analyzed, or a trend contrary to Rensch's rule (smaller species more dimorphic, but with male-biased dimorphism). Lack of adherence to Rensch's rule in Didelphimorphia may relate to a lack of social interactions and male territoriality, usually associated with such a trend via sexual selection. If the trend contrary to Rensch's rule is real, an explanation may lie in the increasing amount of smallbodied species that recently have been found to be semelparous and thus subject to stronger selection for larger males. [ABSTRACT FROM AUTHOR]

No abstract available [ABSTRACT FROM AUTHOR]

Caluromysiops irrupta Sanborn, 1951 is a poorly known didelphid marsupial species, currently known from nine localities in south-central and western Amazonia. Only two records of C. irrupta were known from Brazil. Here we report the third record, in Rondônia state, northwestern Brazil. The specimen was sighted in a well-preserved forest area, in the Parque Estadual Guajará Mirim, Guajará Mirim, Rondônia. Although this record does not represent a distribution extension, it represents an additional record for a very poorly known species. [ABSTRACT FROM AUTHOR]

The New World family Didelphidae, the basal lineage within marsupials, is commonly viewed as morphologically conservative, yet includes aquatic, terrestrial, scansorial, and arboreal species. Here, I quantitatively estimated the existing variability in size and shape of the Didelphidae scapula (1076 specimens from 56 species) using geometric morphometrics, and compared size and shape differences to evolutionary and ecologic distances. I found considerable variation in the scapula morphology, most of it related to size differences between species. This results in morphologic divergence between different locomotor habits in larger species (resulting from increased mechanical loads), but most smaller species present similarly shaped scapulae. The only exceptions are the water opossum and the short-tailed opossums, and the functional explanations for these differences remain unclear. Scapula size and shape were mapped onto a molecular phylogeny for 32 selected taxa and ancestral size and shapes were reconstructed using squared-changed parsimony. Results indicate that the Didelphidae evolved from a medium- to small-sized ancestor with a generalized scapula, slightly more similar to arboreal ones, but strikingly different from big-bodied present arboreal species, suggesting that the ancestral Didelphidae was a small scansorial animal with no particular adaptations for arboreal or terrestrial habits, and these specializations evolved only in larger-bodied clades. [ABSTRACT FROM AUTHOR]

The sequence of molar eruption, along with the timing of replacement of the 3rd deciduous premolar by a permanent premolar, has been documented in several species in the family Didelphidae, and routinely used to establish age classes. We documented the dental eruption and replacement patterns in the 3 species of the neotropical marsupial genus Caluromys, which constitute one of the most basal groups within the Didelphidae. We examined 258 specimens of Caluromys derbianus, 54 specimens of C. lanatus, and 386 specimens of C. philander. These species have a dental eruption pattern that is similar to that of Marmosops, with replacement of the 3rd deciduous premolar after eruption of the 4th molar. However, we sometimes found incompletely erupted P3 and M4 occurring simultaneously as part of a M4-P3 eruption sequence. We suggest that the occurrence of this intermediate pattern in other taxa should be verified by examination of large series of specimens. Because teeth erupting in sequence can be erroneously considered as fitting an intermediate pattern, eruption sequence and time of completion of development should be used separately when using dental eruption in phylogenetic analyses. Because of the high degree of intraspecific variation observed in several taxa in Didelphidae, a system of age classes based solely on eruption of upper molars may be more useful than those that combine information on molar eruption sequence and timing of premolar replacement. [ABSTRACT FROM AUTHOR]

Bite force is a key trait for understanding aspects of vertebrate ecology and evolution, as it relates directly to different evolutionary pressures, like diet and behaviour. Sexual dimorphism in bite force (SDBF) is an underexplored condition that may shed light on niche divergence between sexes and the effects of sexual selection in species. Here we evaluated differences in modelled bite forces between sexes within Canidae (33 species and two subspecies) and assessed their possible correlations with diet, sociality, hunting strategies, and size dimorphism. We calculated SDBF and bite force quotients through indexes and compared them among different diets, hunting strategies, and sociality groups. Furthermore, we correlated the indexes and size sexual dimorphism using phylogenetic independent contrasts. Only two species showed significant SDBF: the Cape fox (Vulpes chama) and the Ethiopian wolf (Canis simensis). We found no significant differences in bite force dimorphism intensity between sociality levels, dietary levels, or hunting strategies. We found a relationship between bite force sexual dimorphism and size sexual dimorphism, and a correlation between bite force and the bite force quotient dimorphism. However, we found no association between sexual dimorphism in bite force quotient and sexual size dimorphism. Our findings show that Canidae do not have bite force dimorphism, possibly due to the widespread social monogamy in the family, when compared to other Carnivora. This implies possible restrictions that constraint the range of bite strength in adults, especially in females. [ABSTRACT FROM AUTHOR]

Here we present an extensive survey for non-volant mammals along the margins of the Jequitinhonha River, which represents a contact area between the Cerrado and Atlantic Forest biomes. Our data were obtained after 13 trapping expeditions (from 2005 to 2012) on both banks of the river, from its source to its mouth, enriched by data obtained from a literature review and voucher specimens deposited in six mammal collections. All collected specimens were identified through their karyotypes and/or morphology. We obtained data for 75 localities (34 at the rigth margin, 42 at the left margin; 30 in the Cerrado and 45 in the Atlantic Forest). We obtained voucher records for 91 species, ca. 17% of all known Brazilian terrestrial non-volant mammals. Our results include range extensions for six species (Monodelphis scalops, Thylamys velutinus, Calomys mattevii, Wiedomys pyrrhorhinos, Galea spixii, Kerodon rupestris), and karyotype information for 26 species (11 marsupials and 15 rodents), with four new karyotypes. While most species have wide geographical range in both biomes, 26 were recorded only in the Cerrado and 19 were recorded only in the Atlantic Forest. Recorded species represent 28.7% (6.3% endemic) of the species known from the Cerrado and 21.5% (22.2% endemic) of those from the Atlantic Forest. The richness of the fauna recorded in this region supports its importance for the understanding of mammal biogeography, diversity and evolution. [ABSTRACT FROM AUTHOR]

We employed landmark-based 3D geometric morphometrics to assess cranial size and shape diversification in Trichechus manatus and T. inunguis to compare it with patterns among all manatee taxa ( T. manatus latirostris, T. m. manatus, T. inunguis and T. senegalensis), and to analyse geographic variation within American manatee populations, using a sample of 189 skulls. Chromosome G- and C-banding techniques were performed in T. m. manatus from Brazil. All taxa were statistically discriminated by skull shape. Trichechus m. manatus and T. m. latirostris have larger skulls than T. inunguis. A morphological discontinuity was noted within T. m. manatus, with the Brazilian population south of the Amazon discriminated from the T. m. manatus Caribbean and T. m. latirostris USA populations. Specimens from Suriname and Guyana had a skull shape more similar to the one from the Caribbean population. The Brazil Antillean manatee population exhibited morphological differences similar in magnitude to those found between the Amazonian and African species. Additionally, structural chromosome differences were detected between that population (chromosome pair 4 is metacentric and 10 is submetacentric) and manatees from Puerto Rico and Florida. Based on such morphological discontinuity and chromosomal divergence, we hypothesize that the Amazon River mouth may be acting as a reproductive barrier for the T. m. manatus population in Brazil, thus indicating that its taxonomic status and conservation strategies need an urgent reassessment. [ABSTRACT FROM AUTHOR]

We report the results of a terrestrial small mammal survey at one National Park in the northeastern Brazil, in the state of Pernambuco. The Catimbau National Park is located within the Caatinga domain with the characteristic thorn scrub vegetation. Our sampling encompasses several different vegetation/habitat types within the park area. All specimens collected were prepared as vouchers to be deposited in the Museu de Zoologia da Universidade de São Paulo. Karyotypes were obtained for all representative purported species collected. We report here the results of this first survey - two species of marsupials and seven of rodents - and added new occurrence localities for several small mammal species of this region, provide karyotypic information and register an undescribed species of arboreal rat of the genus Rhipidomys. This survey illustrates the need for extensive and planned sampling of the Caatinga domain. [ABSTRACT FROM AUTHOR]

Local abundance results from the interaction between populational and environmental processes. The abundance of the species in a community is also one of the most basic descriptors of its structure. Despite its importance, information about species abundances is fragmentary, creating a knowledge gap about species abundances known as the Prestonian Shortfall. Here we present a comprehensive data set of small mammal abundance in the Atlantic Forest. Data were extracted from 114 published sources and from unpublished data collected by our research groups spanning from 1943 to 2017. The data set includes 1,902 records of at least 111 species in 155 localities, totaling 42,617 individuals represented. We selected studies that (1) were conducted in forested habitats of the Atlantic Forest, (2) had a minimum sampling effort of at least 500 trap-nights, and (3) contained species abundance data in detail. For each study, we recorded (1) latitude and longitude, (2) name of the locality, (3) employed sampling effort, (4) type of traps used, (5) study year, (6) country, and (7) species name with (8) its respective abundances. For every locality, we also obtained information regarding its (9) ecoregion, (10) predominant vegetation type, and (11) biogeographic subdivision. Whenever necessary, we also (12) updated the species names as new species were described and some genera suffered taxonomic revision since the publication. The localities are spread across the Atlantic Forest and most of the small mammal species known to occur in Atlantic Forest are present in the data set, making it representative of communities of the entire biome. This data set can be used to address various patterns in community ecology and geographical ecology, as the relation between local abundance and environmental suitability, hypothesis regarding local and regional factors on community structuring, species abundance distributions ( SAD), functional and phylogenetic mechanisms on community assembling. [ABSTRACT FROM AUTHOR]