Geographic varition, diet and temperature in cranial morphology of South American human populations: an approach based on spatial regression and rate test

PEREZ S.I.; LEMA V ; FELIZOLA DINIZ-FILHO JA; BERNAL V.; GONZALEZ P.; GOBBO D; PUCCIARELLI H.

JOURNAL OF BIOGEOGRAPHY

WILEY-BLACKWELL PUBLISHING, INC

Año: 2011 vol. 38 p. 148 - 163

0305-0270

Understanding the importance of ecological factors in the origin andmaintenance of patterns of phenotypic variation among populations, in anexplicit geographical context, is one of the main goals of human biology, ecologyand evolutionary biology. Here we study the ecological factors responsible forcraniofacial variation among human populations from South America.Location South America.Methods We studied a dataset of 718 males from 40 South Americanpopulations, coming from groups that inhabited different geographical andecological regions. Cranial size and shape variation were studied using 30 cranialmeasurements. We first used spatial correlograms and interpolated maps toaddress spatial patterns. We then regressed the shape (principal component scores)and size variables against ecology (mean annual temperature and diet) usingmultiple and multivariate spatial regression. Finally, the expected magnitudes ofshape and size divergence under the influence of genetic drift and mutations alonewere evaluated using neutral expectation for the divergence rate.Results The spatial correlograms showed a cline affecting the entire SouthAmerican distribution. Interpolated maps showed that size and allometric shapevary from south-east to north-west. Multiple and multivariate regression analysessuggested that diet has the largest and most significant effect on this pattern ofsize and allometric shape variation. Finally, the results of the divergence rate testsuggested that random processes alone cannot account for the morphologicaldivergence exhibited by cranial size and allometric shape scores amongsouthernmost populations.Main conclusions Correlograms, spatial regression and divergence rate analysesshowed that although local factors (neutral processes or local environmentalconditions) are important to explain spatial interpopulation differentiation incranial characteristics among these populations, there is significant correlation ofcranial size and allometric shape variation with diet. Gene flow among humanpopulations, or local environmental conditions, could explain spatial variationmainly at smaller spatial scales, whereas the large-scale pattern of the SouthAmerican dataset is mainly related to the high proportion of carbohydrates andlow proportion of proteins consumed.