Stygobiotic crustacean species richness: a question of numbers, a matter of scale

Abstract

Species richness in ground water is still largely underestimated, and this situation stems from two different impediments: the Linnaean (i.e. the taxonomic) and the Wallacean (i.e. the biogeographical) shortfalls. Within this fragmented frame of knowledge of subterranean biodiversity, this review was aimed at (i) assessing species richness in ground water at different spatial scales, and its contribution to overall freshwater species richness at the continental scale; (ii) analysing the contribution of historical and ecological determinants in shaping spatial patterns of stygobiotic species richness across multiple spatial scales; (iii) analysing the role of b-diversity in shaping patterns of species richness at each scale analysed. From data of the present study, a nested hierarchy of environmental factors appeared to determine stygobiotic species richness. At the broad European scale, historical factors were the major determinants in explaining species richness patterns in ground water. In particular, Quaternary glaciations have strongly affected stygobiotic species richness, leading to a marked latitudinal gradient across Europe, whereas little effects were observed in surface fresh water. Most surface-dwelling fauna is of recent origin, and colonized this realm by means of post-glacial dispersal. Historical factors seemed to have also operated at the smaller stygoregional and regional scales, where different karstic and porous aquifers showed different values of species richness. Species richness at the small, local scale was more difficult to be explained, because the analyses revealed that point-diversity in ground water was rather low, and at increasing values of regional species richness, reached a plateau. This observation supports the coarse-grained role of truncated food webs and oligotrophy, potentially reflected in competition for food resources among co-occurring species, in shaping groundwater species diversity at the local scale. Alpha-diversity resulted decoupled from c-diversity, suggesting that b-diversity accounted for the highest values of total species richness at the spatial scales analysed.

VIEWPOINT. Is the Australian subterranean fauna uniquely diverse?

“…Compared with other regions of the world, we consider the Australian subterranean fauna to be unique in its diversity for three key reasons: (1) the range and diversity of subterranean habitats where fauna have been discovered are both extensive and novel compared with the northern hemisphere; (2) direct faunal links to Gondwana are found in Australia's west, emphasising its early biogeographic history; and (3) tertiary events, particularly developing aridity in the late Miocene/Pliocene (14-2 Mya), appear to have dominated the diversification of Australia's subterranean fauna, unlike much of the northern hemisphere (Stoch and Galassi 2010), where the fauna was not greatly modified during Pleistocene glaciations.…”

“…Globally, the northern hemisphere dominates as a region of subterranean biodiversity hotspots, in particular temperate midlatitude locations (Culver et al 2006;Stoch and Galassi 2010) such as the Balkan Peninsula, the USA (Culver and Sket 2000), Mexico (Reddell 1981) and, most recently, caves of south-east Asia (Deharveng 2005). Subterranean faunal diversity is generally concentrated in karst and pseudokarst areas (Juberthie and Decu 1994;Culver et al 2001;Christman et al 2005;Deharveng 2005).…”

A New Threat to Groundwater Ecosystems: First Occurrences of the Invasive Crayfish Procambarus clarkii (Girard, 1852) in European Caves

“…This species is recognized as one of the most invasive crayfish in Europe and, thanks to its plasticity, it can prey on many endemic cave species, since it feeds on diverse items in proportion to their availability. The European groundwater fauna comprises more than 1,800 stygobitic species (Stoch and Galassi, 2010), most of them endemic to restricted areas or single karstic massifs in southern countries. At least sixty-seven groundwater-dwelling species are endemic to Portugal (Reboleira et al, 2011(Reboleira et al, , 2013, and P. clarkii could be an important threat to some of these species, such as asellid isopods like Proasellus lusitanicus (Frade, 1938), as well as amphipods belonging to the genus Pseudoniphargus Chevreux, 1901.…”

Interação rio-aquífero e a meiofauna do ambiente hiporreico

“…O que pode se afirmar é que a zona hiporreica é um ambiente importante para a fauna de invertebrados (BRET-SCHKO, 1992;STOCH & GALASSI, 2010;DOLE-OLIVIER, 2011).…”