Models of evolutionary ecology
Moss cushions or lichens are microhabitats for anhydrobiotic invertebrates or may be considered (Ellenberg 1973) as „nanoecosystems” (part of bigger ecosystems) inhabited by a community dominated by nematodes, rotifers and tardigrades. In mosses and lichens, with their wet and dry cycles, tardigrades, nematodes and rotifers have found their ecological niches. They are the main taxonomic groups with holo – anhydrobiotic animals.
Lichens or moss cushions including their oldest metazoan inhabitants, the tardigrades, the rotifers and the nematodes in a certain environment are possibly ideal models for a system of „living fossils“. „Living fossils“ are organisms with an unusually slow rate of evolution (bradytely) which results when species avoid environmental selection pressures. It may be suggested a parallel evolution between desiccation tolerant cryprogams (algae, lichens and mosses) and tardigrades, rotifers and nematodes from marine habitats invading limno-terrestrial environments very early in the Paleozoic Era. The ancestors of tardigrades probably first appeared during the Cambrian explosion. Poikilohydry in mosses and anhydrobiosis in tardigrades, rotifers and nematodes would have evolved in parallel (convergent evolution). Such models of „living fossils“ allow studies on whole systems living today (perhaps) in a similar way as hundreds of million years before. Unlike the life of Dinosaurs (not „living fossils“) we can study the ecophysiological aspects of evolution of that time today on living systems.
Evolutionary ecology asks why natural selection favoured such a bryophilous community with the tardigrades.
Functional ecology asks how such a system works.