Post provided by ROB LEWIS & MEELIS PÄRTEL
Our understanding of how biological diversity works has been advanced by a long history of observing species and linking patterns to ecological processes. However, we generally don’t focus as much on those species that aren’t observed, or in other words ‘absent species’. But, can absent species provide valuable information?
Dark diversity – a set of species absent from a particular site but which belong to its species pool – has the potential to be as ecologically meaningful as observed diversity. Part of the species pool concept, understanding dark diversity is relatively straightforward.
The Basic Theory of Dark Diversity
To begin learning about dark diversity, there are two important terms that we need to define: ‘species pool’ and ‘focal community’. A ‘species pool’ is a set of species present in a particular region or landscape that can potentially inhabit a particular observed community because of suitable local ecological conditions.
A ‘focal community’ is the set of species that have been observed in a particular region or landscape (this is the ‘observed community’ and can also be referred to as alpha diversity). For a given focal community to become established, the species within it must have overcome dispersal pressures as well as environmental and biotic filters.