Ecogeographical Variation in Skull Shape of South-American Canids: Abiotic or Biotic Processes?

Abstract

Species morphological changes can be mutually influenced by environmental or biotic factors, such as competition. South American canids represent a quite recent radiation of taxa that evolved forms very disparate in phenotype, ecology and behaviour. Today, in the central part of South America there is one dominant large species (the maned wolf, Chrysocyon brachyurus) that directly influence sympatric smaller taxa via interspecific killing. Further south, three species of similar sized foxes (Lycalopex spp.) share the same habitats. Such unique combination of taxa and geographic distribution makes South American dogs an ideal group to test for the simultaneous impact of climate and competition on phenotypic variation. Using geometric morphometrics, we quantified skull size and shape of 431 specimens belonging to the eight extant South American canid species: Atelocynus microtis, Cerdocyon thous, Ch. brachyurus, Lycalopex culpaeus, L. griseus, L. gymnocercus, L. vetulus and Speothos venaticus. South American canids are significantly different in both skull size and shape. The hypercarnivorous bush dog is mostly distinct in shape from all the other taxa while a degree of overlap in shape—but not size—occurs between species of the genus Lycalopex. Both climate and competition impacts interspecific morphological variation. We identified climatic adaptations as the main driving force of diversification for the South American canids. Competition has a lower degree of impact on their skull morphology although it might have played a role in the past, when canid community was richer in morphotypes.Electronic supplementary materialThe online version of this article (doi:10.1007/s11692-015-9362-3) contains supplementary material, which is available to authorized users.

Anatomical and morphometric evaluation of the orbit, eye tunics, eyelids and orbital glands of the captive females of the South African painted dog (Lycaon pictus pictus Temminck, 1820) (Caniformia: Canidae)

“…An example is the study by Neto et al [62], who qualified the skull type as mesocephalic in the crab-eating fox based on the skull measurements. Numerous studies on craniometry or skull morphology carried out by scientists significantly focused on the cranial ontogenesis and the relationship between the skull form and the developmental, ecological, and evolutionary aspects, although skull types have not been categorized in other Canidae [63][64][65][66][67][68][69][70][71][72][73][74]. This significantly limits correlation studies of the skull mophometry and the orbit morphometry performed by veterinarians specialized in veterinary ophthalmology of wild or captive animals.…”

Geographic variation in the skull morphology of the lesser grison (Galictis cuja: Carnivora, Mustelidae) from two Brazilian ecoregions

“…The wide geographical distribution of the lesser grison and the range of habitats this mustelid occurs in offer the opportunity to evaluate morphological variations, by testing the existence of ecotypes ( Turesson, 1922 ). Morphometric analyses of several mammalian craniums suggest that patterns of morphological variation in species with large distribution areas might be adaptations to a range of environmental conditions ( Gay & Best, 1996 ), availability of resources ( Mcnab, 2010 ; Schiaffini, 2016a ), or to reduce competition with ecologically similar species occurring in sympatry ( Bubadué et al, 2015 ). Thus, we hypothesize that there should be a variation in the size and/or shape of the skull of the lesser grison among populations of different ecoregions throughout the distribution of the species in Brazil, leading to the existence of ecotypes adapted to their respective environments.…”

Comparative genomics uncovers the evolutionary history, demography, and molecular adaptations of South American canids

“…3 D ). Moreover, interspecific gene flow during the radiation of Lycalopex foxes possibly augmented their adaptive potential through the introduction of new alleles, facilitating their rapid ecological diversification ( 74 , 75 , 77 – 81 ), as in other species ( 82 – 84 ).…”