Geographic variation in gorilla limb bones

Phylogenetic and environmental effects on limb bone structure in gorillas

“…Postcranial morphological differences between gorilla species and subspecies have been described by a number of authors (Dunn et al, ; Groves, ; Groves & Stott, ; Inouye, ; Jabbour & Pearman, ; Jungers & Susman, ; Knigge et al, ; Ruff, ; Sarmiento, ; Schultz, ; Taylor, ; Tocheri et al, ). Several of the distinctions between G. gorilla and G. beringei , particularly in the foot (functionally shorter digits, less abducted hallux, less inverted set in G. b. beringei ), have been interpreted as adaptations to greater terrestriality in G. beringei (Dunn et al, ; Knigge et al, ; Sarmiento, ; Schultz, ; Tocheri et al, ).…”

“…A later morphometric study of virtually the same sample found more evidence for ecological rather than taxonomic groupings, with talar morphology varying between low and high elevation grauer gorillas in a manner similar to that between western lowland and mountain gorillas (Knigge et al, ). Variable results for long bone linear dimensions have also been reported, with one study finding very little difference between grauer and mountain gorillas (Jabbour & Pearman, ), and other studies finding some distinctions in length proportions, with grauer gorillas grouping with western lowland gorillas in certain respects (Groves, ; Groves & Stott, ). Comparisons of long bone dimensions between low and high elevation grauer gorillas have also yielded conflicting results, with evidence for (Jabbour & Pearman, ) or against (Groves, ; Groves & Stott, ) differences between them.…”

“…Current geographic ranges of the four subspecies are shown in Figure . Because of the rarity of G. g. diehli (Cross River gorilla) skeletal material and the apparent lack of postcranial differences between it and G. g. gorilla (Jabbour & Pearman, ; Sarmiento & Oates, ), it is not further considered here (no specimens were included in this study). Estimates of genetic divergence times between Gorilla taxa have varied somewhat depending on methodology.…”

“…Some earlier comparisons are complicated by uncertainty regarding taxonomic assignments, or simply grouping together of eastern subgroups, i.e., G. b. beringei and G. b. graueri . When specifically evaluated, the postcranial morphology of G. b. graueri has sometimes but not always been reported as intermediate between that of G. b. beringei and G. g. gorilla , depending on the type of characteristic examined and geographic sampling of specimens (Dunn et al, ; Groves, ; Jabbour & Pearman, ; Knigge et al, ; Tocheri et al, ). Thus, for example, aspects of medial cuneiform shape that reflect relative hallucial abduction ability, and that differ between G. g. gorilla and G. b. beringei , were similar in G. b. graueri and G. b. beringei (Tocheri et al, ).…”

“…Because of their relatively recent diversification and documented genetic and ecological relationships, gorillas have often been invoked as a model for early hominin evolution and adaptation (Albrecht, Gelvin, & Miller, ; Dunn et al, ; Jabbour & Pearman, ; Knigge et al, ; Pilbrow, ; Scally et al, ), and for the process of speciation in general (Albrecht et al, ; Leigh, Relethford, Park, & Konigsberg, ; Taylor, ). Genetic and ecological/behavioral variation among different gorilla subgroups is summarized schematically in Figure .…”