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Vol. 54, 2015
Morphological variability of the cranium of Lontra longicaudis (Carnivora: Mustelidae): a morphometric and geographic analysis
Pablo César Hernández-Romero1*, José Antonio Guerrero2 and Carolina Valdespino1
1Instituto
de Ecología A.C., Red de Biología y Conservación de Vertebrados, CP
91070, Carretera antigua a Coatepec 351, Xalapa, Mexico
2Facultad de Ciencias Biológicas, Universidad Autónoma del Estado de Morelos, C. P. 62210 Cuernavaca, Morelos, Mexico
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.
Key words: Geographic variation; Geometric morphometrics; Lontra longicaudis; Sexual dimorphism.
*Correspondence: E-mail: pabloecologico@yahoo.com.mx
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