Conclusions:
Much progress has been made in recent years towards understanding
chondrichthyan evolution and ecology. However, it is undeniable that
many major knowledge gaps remain, and in particular our understanding of
trait evolution in this clade is less robust than in many other
vertebrate radiations. I argue that the key driver of this uncertainty
is a lack of integration between genetic, morphological, and behavioural
studies. Failure to integrate these key areas of organismal biology
fundamentally constrains our understanding of phenotypic evolution, both
past and present. Most significantly, this impedes study of the genetic
architectures underlying phenotype and how selection acts upon them.
Despite this, the necessary tools to overcome this major limitation
already exist and have been applied to other taxa (Figure 1). Future
studies should focus on increasing the taxonomic breadth of existing
studies of chondrichthyan genetics, morphology, and behaviour, as well
as the implementation of more quantitative genetic approaches. Only
though this will we truly be able to understand trait evolution in
Chondrichthyes to a comparable extent to other major vertebrate
radiations, and its implications for past evolution and vulnerability in
the face of climate change.