Introduction

Classic analyses of gorilla systematics by Coolidge (1929) and Groves (1970) form a vital foundation for virtually all contemporary studies of gorillas (see also important morphological studies by Albrecht et al., this volume; Groves, this volume; Haddow and Ross, 1951; Vogel, 1961; Sarmiento et al., 1996; Stumpf et al., 1998, this volume). Investigations of Gorilla subspecies diversity also inform many other fields such as paleoanthropology (cf. Albrecht et al., this volume; Lieberman et al., 1988). Despite a good understanding of variation within this species, theoretical advances and new analytical techniques point to a need to reassess our current understanding of gorilla variation. Measures of subspecific variation have important implications for studies of microevolution, ecomorphology, population dynamics, and evolutionary history. Concomitantly, increasing pressures on wild populations underscore the need for a clearer understanding of the structure of subspecific variability in a conservation context (Suter and Oates, 2000).

Therefore, the goal of this analysis is to investigate morphological diversity in gorillas through new measures of variation below the species level. More specifically, this analysis evaluates overall levels of variation within the Gorilla species through application of Wright's Fst to craniometric data (Wright, 1951; 1969; Relethford, 1994). This approach, typically used to measure genetic microdifferentiation, calibrates the degree to which subdivision within populations or species departs from a quantitative expectation of no substructure.