Indonesian freshwater bivalves: a meta-analysis of endemicity, ecoregion distributions, and conservation status

Biological information on Indonesian freshwater bivalves is scattered across publications. Thus, to assemble comprehensive data on their diversity, origin, ecoregion distributions, and conservation status, we conducted a meta-analysis of data from 521 scientific references published between 1838 and early 2021. A total of 57 valid species of 119 freshwater bivalves were documented in the reference sources, reflecting 4.8% of the world's freshwater bivalve species, with 29 (50.9%) being endemic species. Lake Toba, Singkarak, Poso, Malili system river, Sentani, river of Indragiri, Kapuas, Digul and Merauke are the endemicity hotspots of freshwater bivalve in Indonesia. The geographic distribution of species diversity is discussed both in terms of bivalve characteristics and ancient rivers analysis, so it is made that Indonesian's freshwater bivalves were distributed across three ecoregions: 1) Sundaland, comprising the main islands of Sumatra, Java, and Kalimantan (part of Borneo), dominated by the Unionidae; 2) Wallacea, which comprises Sulawesi only, dominated by the Cyrenidae; and 3) the Sahul region, which comprises only Papua and is a hotspot of the Hyriidae. Unfortunately, 43 (75.4%) of the species recorded were not listed in the IUCN directory, and only 12 (21.1%) were recognized by the Indonesian government as protected species. Research on freshwater bivalve species diversity and conservation actions are urgently warranted; neglect of this ecologically and economically important group could cause species declines, more species being categorized as historical species, and, at worst, the unexpected extinction of species. In addition, adequate funding, solid research teams, research continuity, and inter-institutional solid collaboration are needed to strengthen the conservation of freshwater bivalve diversity in Indonesia.