A new genus and two new, rare freshwater mussel (Bivalvia: Unionidae) species endemic to Borneo are threatened by ongoing habitat destruction

Abstract

1. Most of the Bornean endemic freshwater mussel (Unionida) species known to date have not been recorded by science for the past 50 years or more, owing to a lack of research effort and presumed population losses.2. This study assessed current patterns and recent changes in the diversity and distribution of freshwater mussels in north-eastern Borneo. Physical surveys and interviews were conducted at 24 sites, and anecdotal evidence for current or historical presence of mussels was collected for a further 13 sites. 3. Native species, i.e. Schepmania sp. and Khairuloconcha sahanae gen. & sp. nov., were only found in one small stream of the Kinabatangan River basin within the Gomantong Forest Reserve, whereas the non-native Sinanodonta cf. woodiana was common across the study area. 4. Molecular phylogenetics (five genes) of the native taxa, including comparative material from West Kalimantan and Sarawak, revealed: (i) the presence of a new genus with two new, rare species: Khairuloconcha lunbawangorum sp. nov. in the Limbang River basin and K. sahanae in the Kinabatangan River basin; (ii) that Khairuloconcha and Ctenodesma form the Bornean endemic tribe Ctenodesmini trib. nov.; and (iii) that Schepmania represents another Bornean endemic tribe Schepmaniini trib. nov. 5. Both Khairuloconcha gen. nov. species are known from a single stream each and are apparently restricted to forest stream habitats where they occur at very low densities. Schepmania appears to have a severely contracted range in the Kinabatangan and adjacent basins. We urgently call for full protection of the currently known sites of K. lunbawangorum and K. sahanae, and development of an action plan to save the Bornean freshwater mussel fauna.

An alarming tendency towards freshwater mussel misidentification in scientific works may bias endangered and invasive species management

“…This country harbours a taxonomically rich fauna of freshwater mussels, containing representatives of the families Unionidae and Hyriidae (McMichael & Hiscock, 1958;Sahidin et al, 2021). Two larger islands, Borneo and New Guinea, are exceptional evolutionary hotspots of these animals, characterized by high levels of endemism and housing ancient phylogenetic relicts (Walker et al, 2001(Walker et al, , 2014Zieritz et al, 2021). The tropical lineage of Sinanodonta woodiana (Unionidae) was introduced to Indonesia in the 1970s and now is widespread throughout the country's islands from Sumatra and Java to the Lesser Sundas and New Guinea (Bolotov et al, 2016;Djajasasmita, 1982;Sahidin et al, 2021).…”

DNA metabarcoding unravels unknown diversity and distribution patterns of tropical freshwater invertebrates

“…For most of these taxa, we lack even the most basic data, such as numbers and identities of species, as well as identification tools (Morse et al, 2007). New freshwater invertebrate species are described from Southeast Asia every year (Jeratthitikul et al, 2021;Mendoza & Yeo, 2014;Zieritz, Jainih, et al, 2021a), but morphological descriptive work is time-intensive and will not be completed before many of these species will have become extinct (Morse et al, 2007). In recent decades, however, molecular tools have emerged as an alternative for detecting and identifying species, particularly for morphologically variable or cryptic, poorly studied, or yet undescribed taxa.…”

Disappearance or overlooked or untouched? - A brief history of aquatic gastropods of Malaysian Borneo

“…Institutions, governments, universities, and conservation organizations both locally and internationally are increasingly concentrating their attention on the discovery of more species and the sustainable management of those species in Malaysian Borneo [21][22][23]. Although the number of publications are rising, Hamli & Al-Asif [7] proposed the publishing trends of bivalve study might rise in the following decade, while investigations continued.…”