|
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. |