A riverine biodiversity hotspot in northern Myanmar supports three new and narrowly endemic freshwater mussel species

Abstract

1. The Western Indochina Subregion (Myanmar) represents a freshwater biodiversity hotspot of worldwide significance and houses a plethora of endemic freshwater species, among which are amphibians, fish, and various aquatic invertebrates.2. The freshwater mussel (Bivalvia: Unionidae) fauna of western Indochina is characterized by high taxonomic richness, with almost all species and several genera being endemic to the subregion. Furthermore, there are a number of species endemic to a single basin or even to a single tributary of a larger river system (the so-called intra-basin endemic taxa). 3. Here, the discovery of three new, narrowly endemic freshwater mussel species from northern Myanmar is presented: Radiatula kachinensis sp. nov., Trapezidens mogaungensis sp. nov. (upper Ayeyarwady basin), and Lamellidens chindwinensis sp. nov. (upper Chindwin basin). All the new species are upland river specialists, which are under high human pressure as a result of habitat degradation, deforestation, oil palm expansion, river damming, and biological invasions. 4. A nearly complete lack of data on the life cycles and fish hosts should be considered the most striking gap in recent knowledge of tropical Asian freshwater mussels. Here, available data on 27 species belonging to the genera Radiatula, Trapezidens, and Lamellidens are revised. It is shown that certain fish hosts are known for two species only. 5. Further spread of the alien Chinese pond mussels (Sinanodonta woodiana species complex) in Indochina may be considered one of the significant threats to native freshwater mussel populations. Here, it is shown that the temperate invasive lineage of S. woodiana is established in at least three non-native populations in the Ayeyarwady and Salween basins. Moreover, the first arrival of the tropical invasive lineage of S. woodiana to Myanmar is announced, although it has been predicted previously. This lineage was found at two sites on the Shan Plateau (Ayeyarwady basin) close to the Chinese border.

Pleistocene Glacial Refugia in the Don River Basin: Witness from the Endangered Depressed River Mussel

“…Recently it has been shown that multiple freshwater taxa penetrated river systems of Northeastern Europe using the Volga River as a migration corridor [45]. Considering the complex hydrological periglacial network during the LGM [46,47] and reconstructed A. anatina distribution during the Late Quarternary [8], we can speculate that multiple connections between rivers across Europe also occurred. Extremely low genetic differentiation between groups of populations within panEUR lineage indicates high gene flow and supports our suggestion about migration flows across the species range.…”

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

“…Modern homogenization of freshwater faunas is a global phenomenon, of course (Rahel, 2002), but invasions of freshwater mussels beyond their native ranges are usually supported by more or less comparable environmental conditions (Bolotov et al, 2016; Kondakov et al, 2020). Hence, the establishment of non‐native populations of temperate species in tropical water systems (or vice versa) is hardly expected, although a few exceptions may occur (Bolotov, Konopleva, et al, 2022; Vikhrev et al, 2017). Moreover, we argue that at least one taxonomic expert should check freshwater mussel‐focused manuscripts received by non‐taxonomic journals to avoid possible misidentification of target species.…”

“…Many species of freshwater mussels may be distinguished based on conchological features, but there are complexes of cryptic species that do not share clear diagnostic characters and cannot be divided using the morphological characters alone. The genera Sinanodonta , Lamellidens , Lens and Yaukthwa are good examples of such taxonomically complicated clades (Bolotov et al, 2020; Bolotov, Konopleva, et al, 2022; Konopleva et al, 2019; Lopes‐Lima et al, 2020; Pfeiffer et al, 2021). The best way to identify freshwater mussel species from these groups is the DNA‐based approach supplemented with morphological data and biogeographical evidence (Konopleva et al, 2017).…”

Diversity, morphology, and phylogeny of freshwater mussels of the genus Nodularia (Bivalvia: Unionidae) from China, with descriptions of four new species

“…Specifically, some cryptic species may face endangerment or extinction before they are discovered (Cheng et al, 2024). Nowadays, many researchers recognize the significance of cryptic species for biodiversity conservation and acknowledge that these species may be more susceptible to threats in the current complex environment (Bolotov et al, 2024;Nair et al, 2012;Niemiller et al, 2013;Sano et al, 2022). Our research is focused on an understudied group of Nodularia in order to unveil further insights into this taxon.…”