Repeated evolution of amphibious behavior in fish and its implications for the colonization of novel environments

Abstract

We know little about on how frequently transitions into new habitats occur, especially the colonization of novel environments that are the most likely to instigate adaptive evolution. One of the most extreme ecological transitions has been the shift in habitat associated with the move from water to land by amphibious fish. We provide the first phylogenetic investigation of these transitions for living fish. Thirty-three families have species reported to be amphibious and these are likely independent evolutionary origins of fish emerging onto land. Phylogenetic reconstructions of closely related taxa within one of these families, the Blenniidae, inferred as many as seven convergences on a highly amphibious lifestyle. Taken together, there appear to be few constraints on fish emerging onto land given amphibious behavior has evolved repeatedly many times across ecologically diverse families. The colonization of novel habitats by other taxa resulting in less dramatic changes in environment should be equally, if not, more frequent in nature, providing an important prerequisite for subsequent adaptive differentiation.

Evolutionary and cardio‐respiratory physiology of air‐breathing and amphibious fishes

“…4,[12][13][14] There are >200 species of extant amphibious fishes across 93 genera, 41 families and 19 orders. 4,15 This diversity matches the wide variation in life histories, phenotypes and geographic distribution. Some species are emerged (out of water) only in the embryo stage (eg, California grunion, Leuresthes tenuis 16 ), while others may transition as adults between water and air multiple times a day (eg, giant mudskipper, Periophthalmodon schlosseri 17 ).…”

“…Amphibious fishes are a sub‐category of air‐breathing fishes that are defined as fishes that naturally spend part of their life out of the water, and so considered “amphibious” . There are >200 species of extant amphibious fishes across 93 genera, 41 families and 19 orders . This diversity matches the wide variation in life histories, phenotypes and geographic distribution.…”

“…Poor water quality (eg hypoxia, hypercapnia, elevated H 2 S) stimulates many amphibious fishes to emerge . Biotic factors, such as competition, predation, terrestrial feeding and reproduction can also be important . Abiotic and biotic factors can interact to alter emersion behaviour in the mangrove rivulus, Kryptolebias marmoratus .…”

“…18 Biotic factors, such as competition, predation, terrestrial feeding and reproduction can also be important. 15,18 Abiotic and biotic factors can interact to alter emersion behaviour in the mangrove rivulus, Kryptolebias marmoratus. This amphibious fish delays emersion as the water temperature rises if they detect a conspecific nearby compared to fish on their own.…”

Opsin gene evolution in amphibious and terrestrial combtooth blennies (Blenniidae)

“…They comprise one of the most diverse percomorph families 97 consisting of 400 described species (58 genera; fishbase.org) that fall into 13 phylogenetic 98 clades (Hundt et al 2014a, Hundt andSimons 2018). Within the Salariini division of 99 blennies, amphibious behaviour is common, and more than twenty species in at least three 100 genera exhibit a highly terrestrial lifestyle (Ord and Cooke 2016). In these species, post-101 settlement larvae (~30 days from hatching; Platt and Ord 2015) are believed to transition to a terrestrial lifestyle within the supralittoral splash zone and do not voluntarily return to the 103 aquatic environment (Ord et al 2017).…”