Data from: Adaptation for crypsis versus conspicuous social signalling following transitions across an extreme ecotone

A key selection pressure in most habitats is predation, and a common
strategy adopted by prey is crypsis through background matching. Many
marine blenny fishes are in the process of a dramatic transition across
one of the world’s most extreme ecotones: the invasion of land across the
intertidal zone. We investigated the impact of this transition on body
crypsis versus the conspicuousness of visual signals across 56 blenny taxa
relative to 59 biologically relevant backgrounds, and as viewed by
conspecifics and four representative fish and avian predators. We computed
33 colour and 23 pattern indices from standardised digital photographs of
six individuals for each taxa (median sample). Six of these indices were
selected for detailed analysis following phylogenetic Principal Component
Analysis. While phylogenetic regressions revealed some aspects of body
crypsis appeared to have changed adaptively with the progressive
transition to land (specifically a reduction in body colour saturation),
colonisation was primarily facilitated by a generalist form of crypsis.
That is, the colours and patterns of aquatic blennies were already well
matched to the range of terrestrial backgrounds where amphibious and
terrestrial species were observed out of water. Predation appears to have
been an important selection pressure constraining the colour and pattern
of the dorsal fins used in social communication, which also matched visual
backgrounds. Our data implies anti-predator strategies that translate well
across habitats and different predator regimes will facilitate
colonisation by either reducing predation risk or allowing species to
persist long enough to respond adaptively to environmental change.