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Free keywords:
scales; body shape; lateral line;
hybrid intermediacy; convergent evolution
Abstract:
Despite their deeply conserved function among vertebrates, ectodysplasin
(Eda) signalling genes are involved in microevolutionary change in
humans and sticklebacks. If such a dual role is common, Eda signalling
genes constitute hotspots for morphological evolution. Variation in sculpin
(Cottus) skin prickling and body shape resembles patterns caused by variation
in Eda signalling in sticklebacks. We mapped Eda signalling genes
and performed quantitative trait locus mapping in crosses between Cottus
rhenanus and Cottus perifretum. A genomic region containing the Eda receptor
(Edar) was strongly associated with prickling and contributed to shape.
The expression of Edar in developing prickles and skeletal elements in Cottus
was confirmed by in situ hybridization. Coding sequence changes between
Edar alleles in C. rhenanus and C. perifretum exceeded sequence differentiation
in other vertebrates. However, it is likely that additional genetic
elements besides coding changes affect the phenotypic variation. Although
the phenotype in a natural hybrid lineage between C. rhenanus and
C. perifretum resembles C. perifretum, the respective coding Edar alleles are
not fully fixed (88.6%). Hence, our results support an involvement of Eda signalling
in microevolutionary changes, but imply that the Edar gene is affected
by multiple evolutionary processes that vary among freshwater sculpins.
