Riddles in the dark: Assessing diversity patterns for cryptic subterranean fauna of the Pilbara

Aim: Spatial modelling can provide new understanding of patterns in biodiversity and help inform policy, planning and management decisions. However, for many taxa, in many regions, issues with currently available biological data curtail the application of spatial biodiversity models. Here we develop techniques to model spatial patterns of diverse subterranean invertebrate fauna (troglofauna and stygofauna) in the Pilbara region, to better inform biodiversity planning and management for these groups. In this context, the available data are highly biased in their distribution, with specimens often identified only at coarse taxonomic resolution, and individual community surveys sampling a relatively small proportion of the total assemblage at a location. Location: Pilbara bioregion, NW Australia. Methods: To overcome the challenges presented by the subterranean fauna data sets, we developed a community-level spatial biodiversity modelling framework, and applied this to model and project patterns in species richness and compositional turnover, for both troglofauna and stygofauna, using fine-resolution (similar to 30 m) environmental layers. Results: While there was a large amount of inherent noise in the collated data, our spatial models detected potential environmental drivers of community diversity that align with existing knowledge. For troglofauna, species richness was associated with iron-bearing geologies, while community compositional turnover was most strongly related to geographic distance. For stygofauna, groundwater depth was the primary predictor for richness and turnover, alongside other physicochemical groundwater attributes. We identified areas of high biodiversity significance by combining richness and turnover predictions. Main Conclusions: The spatial projections from our biodiversity models indicate the importance of the central Hamersley Range in harbouring unique and diverse subterranean assemblages. These models and projections provide an advanced platform for various biodiversity assessments, including identifying priorities for new surveys, and assessing the likely impacts of proposed development activities on the long-term persistence of subterranean species in the Pilbara.