Abstract:
Colophon is an understudied, rare and endangered
stag beetle genus with all species endemic to isolated mountain
peaks in South Africa’s Western Cape. Geometric morphometrics
was used to analyse intersexual and interspecific
variation of size and shape in the mandibles, heads, pronota
and elytra of two sympatric species: Colophon haughtoni and
Colophon kawaii. All measured structures showed significant
sexual dimorphism, which may result from male-male competition
for females. Female mandibles were too small and
featureless for analysis, but male Colophon beetles possess
large, ornate mandibles for fighting. Males had significantly
larger heads and pronota that demonstrated shape changes
which may relate to resource diversion to the mandibles and
their supporting structures. Females are indistinguishable
across species, but males were accurately identified using
mandibles, heads and pronota. Male C. kawaii were significantly
larger than C. haughtoni for all structures. These results
support the species status of C. kawaii, which is currently in
doubt due to its hybridisation with C. haughtoni. We also
demonstrate the value of geometric morphometrics as a tool
which may aid Colophon conservation by providing biological and phylogenetic insights and enabling species
identification.
