Abstract
Little is known about the genetic structure and phylogeography of Asian arowana (Scleropages spp.). Natural variation in body color has led to the informal distinction of chromatic varieties, but previous studies that attempted to genetically characterize these varieties did not comprehensively cover their geographical distribution. In Malaysia, about 10 drainage-restricted populations of Asian arowana are known that are currently classified into 2 species and 3 color varieties. In this study, we used 3 molecular markers to test 2 hypotheses explaining the relationships among 9 of these populations. The first hypothesis postulates that each color variety forms a monophyletic group, whereas the second hypothesis assumes that Pleistocene paleodrainages shaped the distribution of these populations. We found that the overall genetic variability is low within Asian arowana and that the green variety is non-monophyletic, with other varieties nested within. Instead, the populations of Malaysia belong to 3 genetic lineages that are allopatrically distributed. The ages and distribution of 2 of these lineages are consistent with past connections through paleodrainages, whereas the last lineage is restricted to Central Sarawak. Overall, our results reject the first hypothesis, demonstrating that the geographic origin of specimens is a better phylogenetic indicator than their body color. This study highlights the importance of Malaysia in the conservation of Asian arowana, because it is the only country in which populations of all 3 main genetic lineages occur.
Highlights
Scleropages formosus and S. inscriptus (Teleostei; Osteoglossidae), collectively known as Asian arowana, are among the most endangered freshwater fish in Southeast Asia because of the inexorablePublisher: Inter-Research · www.int-res.comEndang Species Res 46: 205–214, 2021 few lentic or slow-moving lotic habitats scattered tions, and their putative functions have not been throughout Malaysia
In contrast to recent molecular studies which focused on the distinctiveness of the main color varieties of S. formosus but without looking at possible geographical variability within each color variety (Mohd-Shamsudin et al 2011), we considered geographical variability by including specimens originating from as many localities as possible covering most of the natural distribution of S. formosus, and by including S. inscriptus
We found that the distributions of Malaysian populations of Asian arowana are generally congruent with the configuration of these paleodrainages
Summary
Scleropages formosus and S. inscriptus (Teleostei; Osteoglossidae), collectively known as Asian arowana, are among the most endangered freshwater fish in Southeast Asia because of the inexorablePublisher: Inter-Research · www.int-res.comEndang Species Res 46: 205–214, 2021 few lentic or slow-moving lotic habitats scattered tions, and their putative functions have not been throughout Malaysia Scleropages formosus and S. inscriptus (Teleostei; Osteoglossidae), collectively known as Asian arowana, are among the most endangered freshwater fish in Southeast Asia because of the inexorable. Two possible reasons exwak), Indonesia (Sumatra and Kalimantan, i.e. the plain this situation: (1) museum specimens lose most. Bornean region of Indonesia), south Myanmar and of their chromatic pigments once they are preserved, south Cambodia (Fig. 1). S. formosus is listed as and (2) Asian arowana are rare in their natural. Threatened Species (Larson & Vidthayanon 2019), trade broadly recognizes 3 main varieties within S. whereas S. inscriptus is only assessed as Data Defi- formosus One. As expensive aquarium fish (Voight 2016), Asian question that arises is whether the color varieties arowana have been the object of significant genetic within S. formosus represent valid species.
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