Evolution & Habitat: Amphibians (frogs and salamanders) evolved as a bridge species between aquatic and terrestrial animals, situated in the Great Chain of Being between lungfish and amniotes (a group that includes reptiles, birds, and mammals). Our best guess as to their evolution is that they evolved from fish that hunted invertebrates and smaller fish in the shallows. Amphibians evolved towards the end of the Devonian Period (420-360 million years ago) when forests were wet and the climate warmer. There is a wonderfully extensive fossil record illustrating the transition from the ancestral fish to modern amphbians. Acanthostega is the earliest known ancestor. It had 8-toes per foot, had limbs that couldn’t support it on land, and still had gills. Early amphibians were the dominant land predator, feeding on large insects and fish. After the Permian extinction (252 mya), they were dethroned by reptiles as most dominant predator and now are found only in freshwater environments.
I don’t much write about deep time here – though I think and read about it all the time – so I’ll leave the preamble at that and shift to how their evolution from aquatic fish to in-betweeners shapes where on the land we find them. And that’s simple, in all bodies of freshwater. Of course, there has to be an exception, and in this case it’s the red-backed salamander, which is entirely terrestrial. We still need a little more information
Vernal Pools: Vernal pools
Marshes
Floodplains: In grad school, Liz Thompson, co-author of Wetland Woodland Wildland, took our Field Botany class to Ethan Allen homestead. As we were there, we looked at the shift in soil type from the bank adjacent to the . For some reason
Retention Ponds: Retention ponds make great breeding habitat for amphibians. They’re often inaccessible to fish because of inflow and outflow pipes that cut off access
Dead logs: We have only one species of salamander that does not require water for breeding. Red-backed salamanders will lay their eggs under or inside rotting logs.
