FLUCTUATING ASYMMETRY IN GORILLA CANINES - A SENSITIVE INDICATOR OF ENVIRONMENTAL-STRESS

Populations of the western lowland gorilla (Gorilla gorilla gorilla) h ave decreased markedly as a result of human encroachment. The species is therefore likely to have been exposed to substantial environmental stress. Fluctuating asymmetry (FA) is one measure of environmental str ess. We examined the expression of FA in the canines and second premol ars of the upper jaw of western lowland gorillas. The canines had patt erns of FA typical of secondary sexual characters, whereas the express ion of premolar FA was typical of non-sexually selected traits. We fou nd that FA in male canines was positively correlated with year of coll ection (YOC) or year of collection and acquisition (YOCA) Of the speci men. This suggested a sustained environmental deterioration. However, there was no relation between FA and YOC, or FA and YOCA, in female ca nines. There was a correlation between FA and YOC in male premolars, b ut this was relatively weak and disappeared when FA and YOCA Were cons idered. There was no correlation between FA. and YOC or YOCA in the pr emolars of females. We conclude that these patterns of FA support the argument that sexually selected structures are sensitive to environmen tal stress but non-sexually selected structures are not.