Sexual Allometric Monomorphism in Araucan Pig from Colombia: Preliminary Results

Abstract

This study aimed to evaluate the allometric growth of the Araucan pig breed, a creole breed from Arauca, East Colombia, locally known as “Sabaneros”, in relation to different quantitative traits and considering genders separately. To do this, a total of 31 male and 27 female Araucan pigs, ranging from 4 to 48 months of age, were studied in order to evaluate their growth patterns, using a multivariate approach. Animals belonged to different farms (“fincas”) of the Department of Arauca, Colombia. From each individual, 10 quantitative traits were obtained: face width, croup height, croup length, croup width, tail base height, hock height, loin height, cannon length, and length and width of ear. Our results, which must be interpreted as preliminary, showed that the Araucan pig is allometrically monomorphic as sexual differences do not increase with body size. We suggest that although males and females have evidently different reproductive roles, during growth they shift the allocation of energy to structures linked to environmental adaptation rather than those linked to reproduction.

Beyond facial width-to-height ratios: bizygomatic width is highly sexually dimorphic when adjusting for allometry

“…Nakagawa et al [26] advised that researchers avoid anatomical ratio measurements for both statistical and theoretical reasons and that, instead of dividing two measurements to adjust for allometry, 'raw measurements or their direct transformations should be used to control for confounding effects' [26]. Future research might wish to use univariate measures such as body size and height or, more preferably, multivariate approaches [10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][43][44][45][46][47]. This includes shape analyses, which often adjust for allometry by scaling units to their centroid size [43][44][45][46][47].…”

“…Briefly, our models explicitly follow the recommendations of Nakagawa et al [26]. In line with previous guidelines [10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25], size measurements were calculated using PCAs, with these major sources of allometric variation (represented by PCs) being modelled as follows: (i) as an interaction term with sex to estimate the allometric scaling component [26]; (ii) covariates in regression models to estimate size-adjusted sexual dimorphism [26]. We direct interested readers to the electronic supplementary material where we conduct and perform additional analytical considerations, as discussed in [26], which exhibit the same pattern of results.…”

“…Facial morphology is defined by complex interactions among suites of correlated traits [4]. This scaling relationship between the size of a morphological feature and overall body size is termed allometry, routinely captured using principal components analyses (PCAs) [10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25]. The resultant components of major morphological variation represent allometry, often simply termed size [10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25] and recent research has recommended that these size measurements should be modelled as covariates to adjust for allometry rather than using a ratio method [26].…”

“…This scaling relationship between the size of a morphological feature and overall body size is termed allometry, routinely captured using principal components analyses (PCAs) [10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25]. The resultant components of major morphological variation represent allometry, often simply termed size [10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25] and recent research has recommended that these size measurements should be modelled as covariates to adjust for allometry rather than using a ratio method [26]. It is important to account for allometric effects in facial morphology research because it otherwise remains unknown whether the morphological feature is merely a by-product of an overarching developmental system responsible for the combined growth of all morphological features [9].…”

“…This represents the largest and most comprehensive study to date examining sexual dimorphism in fWHR and bizygomatic width with allometric scaling (for comparison, see the meta-analysis by Geniole et al [1]). In line with the recommendations of recent research [26], we accounted for allometric scaling by using bizygomatic width and controlling for 92 anatomical measurements, including facial height measurements, represented by principal components (for more detailed discussion of PCAs in allometry, see [10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25]). We then sought to confirm whether fWHR exhibits malebiased sexual dimorphism (i.e.…”