Morphological variability of the cranium of Lontra longicaudis (Carnivora: Mustelidae): a morphometric and geographic analysis

Abstract

Background: Studies of morphometric variation make it possible to delimit species and geographic intraspecific variation, mainly in species with wide distribution ranges. In the Neotropical otter, Lontra longicaudis, variation in the shape of the rhinarium of three potential subspecies has been described but it is not known whether there is a pattern to the morphometric variation in the skull throughout the distribution of this species. We analyzed morphological variation in the cranium (ventral view) and the mandible (lateral view) of the Neotropical otter, comparing male and female specimens and evaluating the differences between specified geographic units utilizing methods from geometric morphometrics. Specimens from the entire distribution of the species were analyzed. Between sexes, variability in the shape was determined by calculating the Procrustes distances and using Goodall's F test. Geographic variation was analyzed using a discriminant analysis, an analysis of variance (ANOVA) on a matrix of partial warp scores, and a cluster analysis with Mahalanobis distances, allowing for similarities in shape to be identified between different geographic units. Variation in the size of the two structures was calculated based on the values for centroid size using a one-way ANOVA with a Bonferroni correction and a 95 % confidence interval. Results: There was sexual dimorphism in shape for both views, with males the largest. In general, there was geographic variation in the shape and size of both the cranium and the mandible in the Neotropical otter, exhibiting a pattern that resembled Bergmann's rule. Variation in shape between geographic units could result from the presence of geographic barriers, the spatial configuration of hydrological regions, and/or the large distances between populations throughout this species' distribution. Conclusions: The Neotropical otter exhibits dimorphism in the size, but not in the shape of the skull. There is geographic variation between geographic units, and our results suggest that L. longicaudis could be a group of species. An integrative study using molecular and morphological data could elucidate its taxonomy.

The Neotropical otter Lontra longicaudis: a comprehensive update on the current knowledge and conservation status of this semiaquatic carnivore

“…Hernández‐Romero et al. () conducted the first study focused on the Neotropical otter's morphological traits. By using a geometric morphometric approach, they evaluated variation in the cranium and mandible of museum specimens representative of a large portion of the species’ range.…”

“…According to Hernández‐Romero et al. (), the observed morphological variation may be a reflection of different selective pressures acting on both structures in distinct landscapes, influenced by a wide variety of ecological factors. Moreover, their results could be explained by the presence of different evolutionary units delimited by geographic barriers, as is the case with differences in size and shape in Neotropical otter skulls and mandibles from the western Andes and adjacent regions of Orinoco and the Amazon.…”

“…, Luna‐Aranguré ), as well as on morphological variation in the Neotropical otter throughout its range (Hernández‐Romero et al. ). There is a spatial bias towards areas where most studies have been conducted.…”

Wing Geometric Morphometrics of Workers and Drones and Single Nucleotide Polymorphisms Provide Similar Genetic Structure in the Iberian Honey Bee (Apis mellifera iberiensis)

“…The landmark-based geometric morphometrics is acknowledge as the most rigorous and powerful morphometric technique currently available. It has been applied to a variety of structures (e.g., wings, shells, cranial bones, mandibles, premaxilla) and organisms (from insects to mammals) to describe interand intra-specific variation and underlying evolutionary processes [70][71][72][73][74][75][76][77][78]. In A. mellifera, geometric morphometrics of wing vein junctions has been used to discriminate amongst evolutionary lineages and subspecies [2,16,18,19,21], but not to detect genetic structure within subspecies.…”

Geographic variation of craniodental morphology of the Eurasian otter (<i>Lutra lutra</i>) in East Asia

“…Hernadez-Romero et al . [ 8 ] have analyzed geographical variation in Lontra longicaudis (neotropical otter) using geometric morphometrics. The study has included species distributed across South America and found craniodental changes that could be partly due to geographical separation and distance.…”