Short-range endemic invertebrates

Short-range endemic (SRE) invertebrates are animals that display restricted geographic distributions, nominally less than 10,000 km2, that may also be disjunct and highly localised. The most appropriate analogy is that of an island, where the movement of fauna is restricted by the surrounding marine waters, therefore isolating the fauna from other terrestrial populations. Isolating mechanisms and features such as roads, urban infrastructure, large creek lines and ridges can act to prevent the dispersal and gene flow of the less mobile invertebrate species. Subterranean fauna, which include stygofauna and troglofauna, typically comprise short-range endemics.
Representative examples.
Several animal groups studied in Australia consist largely of short-range endemics, including freshwater and terrestrial gastropods (snails and slugs), earthworms, velvet worms, mygalomorph spiders, schizomids, millipedes, phreatoicidean crustaceans, and freshwater crayfish.
Categories of short-range endemism.
Currently, there is no accepted system to define the varying probabilities of a species to be an SRE. The uncertainty in categorising a specimen as SRE originates in a number of factors including:
Life stages of species that cannot be identified at the species level, e.g. some females and juveniles, are assessed based on the knowledge of the higher taxon they belong to, i.e. family or genus. For example, all juvenile or female "Antichiropus" millipedes would be classified as 'confirmed SRE' as all but two of the 120+ known species in this genus are considered SREs.
Although the different categories of 'SRE-likelihood' may help to set conservation priorities, SRE taxa of all categories should be assessed on their merit, in order to determine appropriate conservation measures that adhere to the Precautionary Principle within environmental impact assessments. That is, "where there are threats of serious or irreversible environmental damage, lack of full scientific certainty should not be used as a reason to postpone measures to prevent environmental degradation."