Acidophilic Collembola: living fossils?

The existence of two groups of acidophilic (mostly present in soils at pH less than 5) and acidintolerant Collembolan species has been demonstrated concurrently by several authors in the course of biocoenotic studies. The examination of morphological features points to a strong relationship between acidophily and hypothetical phyletic relationships between both groups. In the light of Earth history I postulate that acidophilic springtails are relicts from the time when adaptive radiation took place within Collembola, i.e. before the Carboniferous age. At this time soils were poor in nutrients, vegetation was of the acidifying type, and the atmosphere was richer than now in carbon dioxide. Thus Paleozoic environmental conditions were quite similar to those now prevailing in the most acid soils.