Exploring the relationship between sampling efficiency and short‐range endemism for groundwater fauna in the Pilbara region, Western Australia

Abstract

SUMMARY1. Identifying the existence of short or narrow range endemic species is an important issue when planning for conservation of groundwater fauna in the face of threats to groundwater quantity and quality. 2. Fourteen bores were sampled six times over 3 or 4 years to assess the reliability of nethauling sampling in broad-scale survey to collect the groundwater fauna present at a site and to identify short-range endemic (SRE) species. 3. Species accumulation curves suggested that one sample from a bore collected 23% and 46% of species occurring in low and high abundance, respectively, and two samples collected 38% and 65% of such species. False-negative rates provided a slightly higher estimate of the collection probability of species with low abundances. 4. The frequent failure to collect species present at a site means that some apparent shortrange endemism was probably an artefact of low sampling effort. Nevertheless, as is typical for subterranean fauna, a high proportion of the known species in the Pilbara region appeared to be SREs. About 55% had probable ranges <10 000 km 2 , the criterion proposed by Harvey (2002) for short-range endemism. 5. Consideration of species occurrence patterns, natural barriers and the scale of most disturbances suggest that 1000 km 2 is a more satisfactory threshold for short-range endemism than 10 000 km 2 but, as the threshold is reduced, more intensive sampling is required to determine whether a species qualifies as an SRE. 6. Extrapolation of the results of regional sampling suggested the Pilbara contains about 500-550 species of groundwater fauna, with the density of species being relatively uniform across the region. Attempts to use a T-S curve approach (sensu Ugland & Gray, 2004) highlighted the lack of information about within-population dispersal of these species and the area of an aquifer that is effectively sampled by a bore.

Protecting the innocent: studying short-range endemic taxa enhances conservation outcomes

“…data), bringing considerable insight to a poorly known group of arachnids. Many species are known to be endemic to individual geological formations, such as pisolitic mesas only a few hundred hectares in area , and no species are known from an area greater than 500 km 2 , clearly conforming to current definitions of short-range endemism (Harvey 2002;Eberhard et al 2009;Environmental Protection Authority 2009). Knowledge of the taxonomy and distribution of different species and genera has been refined with each new discovery, and recent molecular phylogeographic research has highlighted the evolutionary inter-relationships among species ) and the remarkable subterranean biogeography of the region (summarised in Guzik et al 2011a).…”

“…These factors can all lead to evolutionary diversification over time and to highly restricted modern distributions. Harvey (2002) suggested a nominal range of less than 10 000 km 2 as a working definition of short-range endemism, but Eberhard et al (2009), considering stygofauna, recommended a reduced area of less than 1000 km 2 . Even this may need further refinement as, for example, groundwater calcrete aquifers of the southern Western Shield (Yilgarn) each have unique faunas largely comprising endemic species (Humphreys 2008;Guzik et al 2011a;and references therein).…”

VIEWPOINT. Is the Australian subterranean fauna uniquely diverse?

“…Marmonier (2002, 2003), Karanovic (2003aKaranovic ( , 2003bKaranovic ( , 2004Karanovic ( , 2005aKaranovic ( , 2005bKaranovic ( , 2007) Copepoda Karanovic, T. Pesce and De Laurentiis (1996), Pesce et al (1996aPesce et al ( , 1996b, Karanovic et al (2001), Karanovic and Pesce (2002), Karanovic (2003Karanovic ( , 2004aKaranovic ( , 2004bKaranovic ( , 2005Karanovic ( , 2006 (1998) points (bores or caves). In this case, extrapolation of richness estimates was based on accumulation curves as outlined by Eberhard et al (2009). Second, in the Yilgarn region, since subterranean taxa are restricted to calcretes, and each sampled calcrete was found to have a unique fauna, extrapolation of the data from sampled to unsampled calcretes was warranted.…”

“…In that study, 560 stygofauna species were estimated from the Western Shield and this area comprises~50% of the area examined in this study, thus clearly representing an underestimate of species richness based on the data presented here. Just for the Pilbara region, which represents an even smaller area of the Western Shield, Eberhard et al (2009) estimated 500-550 undescribed species using species accumulation curves. Our results show that much of the subterranean taxa in the western half of Australia remain undiscovered and the potential for new species discovery is extremely high.…”

“…Government and privately funded research in the past five years has primarily focussed on the fauna of the Yilgarn and Pilbara regions of WA and aquifers in SA, in particular utilising boreholes and drill holes installed for exploration and exploitation of water, minerals and monitoring of groundwater levels and salinity, rather than fauna. This work has revealed a diverse subterranean fauna inhabiting both aquatic and terrestrial habitats found in a wide range of substrates, including alluvium, calcretes, fractured rock, karst in soft and hard rock, pisolites and pseudokarst in lava and sandstone Humphreys 1998, 2003;Finston and Johnson 2004;Eberhard et al 2005;Harvey et al 2008;Humphreys 2008;Eberhard et al 2009). Many of the resultant data are unavailable publicly during the EIA process but many become public after formal environmental approvals occur.…”