Contents lists available at ScienceDirect Biological Conservation journal homepage: www.elsevier.com/locate/biocon Changes and drivers of freshwater mussel diversity and distribution in northern Borneo Alexandra Zieritz a, ⁎ , Arthur E. Bogan b , Khairul Adha A. Rahim c , Ronaldo Sousa d , Leonardo Jainih e , Sahana Harun e , Nabilah Fatin Abd Razak a , Belinda Gallardo f , Suzanne McGowan g , Ruhana Hassan c , Manuel Lopes-Lima h a School of Environmental and Geographical Sciences, University of Nottingham Malaysia Campus, Jalan Broga, 43500 Semenyih, Malaysia b Research Laboratory, North Carolina State Museum of Natural Sciences, 11 West Jones Street, Raleigh, NC 27601, USA c Department of Aquatic Science, Faculty of Resource Science & Technology, Universiti Malaysia Sarawak, 94300 Kota Samarahan, Sarawak, Malaysia d CBMA - Centre of Molecular and Environmental Biology, Department of Biology, University of Minho, Campus Gualtar, 4710-057 Braga, Portugal e Institute for Tropical Biology and Conservation, Universiti Malaysia Sabah (UMS), 88400, Jalan Maktab Sabah, 88100 Kota Kinabalu, Sabah, Malaysia f Department of Biodiversity Conservation and Ecosystem Restoration, Pyrenean Institute of Ecology – Spanish National Research Council (IPE-CSIC), Avda. Montañana 1005, 50059 Zaragoza, Spain g School of Geography, University Park, University of Nottingham, Nottingham, NG72RD, UK h CIBIO/InBIO - Research Center in Biodiversity and Genetic Resources, Universidade do Porto, Campus Agrário de Vairão, Rua Padre Armando Quintas, 4485-661 Vairão, Portugal ARTICLE INFO Keywords: Extinction Deforestation Endemic species Invertebrates Sundaland Unionidae ABSTRACT Human activities are threatening Borneo's unique biodiversity, but little is known on the status of freshwater invertebrates. We assessed changes in diversity and distribution of freshwater mussels (Bivalvia: Unionida) in northern Borneo, and identified drivers of present distribution and threats. Past distribution data were collected from literature and museum resources. Present distribution data were collected from 21 river basins, and 47 water quality, climatic, landscape and human variables explored as potential predictors of species presence/ absence. Species delimitations were identified by morphology and COI barcoding, and haplotype networks generated. Our data indicate that over the past 50 years, four of originally five native species have become very rare or possibly locally extirpated. Since these four species are endemic to Borneo, other Bornean river basins should urgently be surveyed to identify any remaining populations. In the same time span, the non-native Sinanodonta woodiana has become the most widespread freshwater mussel in northern Borneo. The fifth native species was identified as Rectidens sumatrensis and found in four Sarawakian river basins, thus contradicting previous assumptions of an endemic Bornean Rectidens species. Although a number of stable R. sumatrensis populations are retained across Sarawak, the species' strong spatial contraction in mainland Sundaland and apparent low tolerance to eutrophication suggest that it is vulnerable to further habitat alteration. Our results indicate that Borneo's (endemic) freshwater invertebrate biodiversity is declining rapidly. Comprehensive sur- veys targeting an array of invertebrate and vertebrate taxa are needed to identify Borneo's freshwater biodi- versity hotspots, where conservation efforts should be concentrated. 1. Introduction Freshwater biodiversity is declining at a rate far greater than ter- restrial or marine ecosystems (Sala et al., 2000; Dudgeon et al., 2006; Strayer and Dudgeon, 2010). Meaningful conservation efforts, at the minimum, require knowledge on the diversity, distribution and habitat requirements of species. However, data on freshwater biodiversity is poor, so that undetected species extinctions are common, particularly for invertebrate taxa and in tropical habitats (Harrison and Stiassny, 1999; Dudgeon et al., 2006). At the same time, available data indicate that freshwater species-richness and levels of endemism peak in the tropics (Dudgeon et al., 2006 and references therein). Nevertheless, in https://doi.org/10.1016/j.biocon.2018.01.012 Received 10 June 2017; Received in revised form 22 December 2017; Accepted 12 January 2018 ⁎ Corresponding author at: School of Environmental and Geographical Sciences, Faculty of Science, University of Nottingham Malaysia Campus, Jalan Broga, 43500 Semenyih, Malaysia. E-mail addresses: Alexandra.zieritz@nottingham.edu.my (A. Zieritz), arthur.bogan@naturalsciences.org (A.E. Bogan), akhairul@frst.unimas.my (K.A.A. Rahim), sahana@ums.edu.my (S. Harun), belinda@ipe.csic.es (B. Gallardo), suzanne.mcgowan@nottingham.ac.uk (S. McGowan), hruhana@unimas.my (R. Hassan), mlopeslima@cibio.up.pt (M. Lopes-Lima). Biological Conservation 219 (2018) 126–137 0006-3207/ © 2018 Published by Elsevier Ltd. T