Geographic variation in Caluromys derbianus and Caluromys lanatus (Didelphimorphia: Didelphidae)

Abstract

ABSTRACT. 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.

Mammalian Diversity and Matses Ethnomammalogy in Amazonian Peru Part 3: Marsupials (Didelphimorphia)

“…Cranial size and shape differences among the specimens we examined do not suggest anything more than individual and ontogenetic variation. In effect, we concur with Fonseca and Astúa's (2015) suggestion that only a single phenotypically distinguishable taxon, which they called C. lanatus ochropus, occurs in the Amazon and Cerrado.…”

“…Metrical comparisons (table 2) indicate that these Paraguayan specimens are smaller than western Amazonian material in several dimensions (e.g., condylobasal length), but both of them are young adults, and measurements of age-invariant struc-tures (e.g., LM, WM3) are within the observed range of western Amazonian variation. With just two Paraguayan examples at hand, and in the absence of any relevant molecular data, it is hard to assess the taxonomic significance of such comparisons, or to properly evaluate Fonseca and Astúa's (2015) suggestion that C. l. ochropus is really distinct from the nominotypical form.…”

Geographic variation in cranial morphology of the Water Opossum Chironectes minimus (Didelphimorphia, Didelphidae)

“…The Black-eared opossums of the genus Didelphis, formerly believed to be a single species, are now divided in two species, just as the White-eared opossums of the same genus, in which a single previously recognized species is currently divided in three species (Cerqueira, 1985;Cerqueira and Lemos, 2000). More recently, a disjunct population of Lutreolina crassicaudata was also considered to constitute a distinct species (Martínez-Lanfranco et al, 2014), and a study investigating geographic variation in Caluromys lanatus showed marked differences between populations from Amazonia-Cerrado and Atlantic forest (Fonseca and Astúa, 2015). It is thus possible that a similar situation could be occurring in Chironectes minimus.…”

“…Although traditional linear morphometrics have routinely been used in mammalogy, the use of geometric morphometric tools to quantify and understand morphological variation in mammals and its relation to current taxonomic arrangements in a variety of mammal groups (e.g. Beolchini and Corti, 2004;Evin et al, 2008;Fonseca and Astúa, 2015;Prevosti et al, 2013).…”

“…Geometric morphometrics were applied in addition to the traditional approach, as geometric morphometrics allow for a better visualization of shape variation, as seen in Fonseca & Astúa (2015), for example. 2D landmarks were digitized on two views of the skull and one of the mandible; 37 on the dorsal view; 18 in the lateral view; and 23 on the mandible (Fig.…”