Animals

Litter louts

The darker and deeper leaf litter would have opened up opportunities both for existing species, but also the development of new ones. More life in soil, meant more opportunities for surface predators, and we have first example of small burrowing mammal ancestors. Ground insects were also eating more soil animals.

Dispersal would have been essential for terrestrial arthropods living in leaf litter. However, acquiring dispersal features, like wings, may have significant costs. Wings are great in the air but wouldn’t be much use foraging in confined microhabitats, like leaf litter and soil. But the ability to run and spring would help dispersal.

Creatures that would make the most of this newly developing leaf litter layer – with bigger holes - would be the fast and slightly larger soil creatures. That along with the fungal growth in the litter would encourage springtails, symphylans and diplurans, all fast movers. Some fo these would have colonised the new leaf litter, others may have evolved into new forms, as we will see. Springtails (Collembola) respond quickly to environmental change, and can move fast, Leaf litter can influence springtail community structure through their physical habitat and resource-driven effects. There is increasing interest in how soil communities respond to planting non-native trees, a common habit across the world (Raymond-Leonard et al 2018)

In most insects, these conflicting requirements have been met through ontogenetic partitioning and the acquisition of holometaboly as we saw that allowed for soil-dwelling larvae, whereas dispersal is performed by the winged adults. For wingless arthropods, the adaptive challenge of reaching new microhabitats is even greater and has led to phoretic (hitching a ride) adaptations, particularly in some arachnid groups like mites and pseudoscorpions.