Abstract
Sexual dimorphism (SD) is a main source of intraspecific morphological
variation, however sexual shape dimorphism (SShD) was long time
neglected in evolutionary research. Especially in cold-blooded animal
groups only subtle shape differences are expressed between males and
females and the selective forces behind it are poorly understood.
Crocodile newts of the genera Echinotriton andTylototriton are highly polymorphic in their reproductive ecology
and hence, are a highly suitable model system to investigate potential
evolutionary forces leading to SShD differences. We applied 3D geometric
morphometrics to the cranial and humerus morphology of nine species of
crocodile newts to investigate patterns of SShD in relation to the
different mating modes. Trajectories of shape differences between males
and females differ in both, cranium and humerus but mating mode does
explain differences in SShD trajectories between species only in cranial
morphology. Nevertheless, cranial morphology shape differed between the
amplecting and circle dancing species. Hence, other selective forces
must act here. Variable interspecific allometric trajectories are a
potential source of shape differences whereas these trajectories are
quite stable for the sexes irrespective of the species.
Key words: Tylototriton , geometric morphometrics,Echinotriton , reproductive biology, ecology, sexual selection