Brown banded bamboo shark (Chiloscyllium punctatum) shows high genetic diversity and differentiation in Malaysian waters

Abstract

The demersal brown banded bamboo shark Chiloscyllium punctatum is a major component of sharks landed in Malaysia. However, little is known about their population structure and the effect of high fishing pressure on these weak swimming sharks. Both mitochondrial DNA control region (1072 bp) and NADH dehydrogenase subunit 2 (1044 bp) were used to elucidate the genetic structure and connectivity of C. punctatum among five major areas within the Sundaland region. Our findings revealed (i) strong genetic structure with little present day mixing between the major areas, (ii) high intra-population genetic diversity with unique haplotypes, (iii) significant correlation between genetic differentiation and geographical distance coupled with detectable presence of fine scale geographical barriers (i.e. the South China Sea), (iv) historical directional gene flow from the east coast of Peninsular Malaysia towards the west coast and Borneo, and (v) no detectable genetic differentiation along the coastline of east Peninsular Malaysia. Genetic patterns inferred from the mitochondrial DNA loci were consistent with the strong coastal shelf association in this species, the presence of contemporary barriers shaped by benthic features, and limited current-driven egg dispersal. Fine scale population structure of C. punctatum highlights the need to improve genetic understanding for fishery management and conservation of other small-sized sharks.

Integrated Taxonomy Revealed Genetic Differences in Morphologically Similar and Non-Sympatric Scoliodon macrorhynchos and S. laticaudus

“…Notably, the presence and taxonomic status of Scoliodon in the Indonesian region, especially along Eastern Sumatra and along the Kalimantan coastline (Figure 6), needs to be investigated using an integrative approach, i.e., molecular and morphological analyses. It was hypothesized that animals along Eastern Sumatra are S. laticaudus, while those in Kalimantan waters are S. macrorhynchos, with the Karimata Strait acting as a physical and/or genetic barrier-this is consistent with evidence presented for the genetic structure seen for C. punctatum [11].…”

“…The Malay Peninsula appears to serve as a contemporary physical barrier between the two species. This pattern has been seen for a number of coastal-associated species with limited dispersal abilities, such as bamboosharks [11], guitarfishes [50], groupers [51], sea snails [52], and a number of mangrove species [53]. The molecular differences between morphologically similar but non-sympatric S. macrorhynchos and S. laticaudus suggest a relatively recent divergence due to geographical isolation with limited mixing that drove allopatric speciation, which is feasible given the complexity of the past geological history of the Sundaland region [54].…”

“…A strong coastal affiliation [7] and limited dispersal due to small size are traits that likely promote genetic differentiation and, thus, increase their vulnerability to localized fishing impacts. A similar pattern of a fine-scale population structure has been revealed for a similar small-sized benthic coastal shark, Chiloscyllium punctatum, that is subject to high fishing pressure in the Southeast Asian region [11,57]. Further investigation into the genetic structure of Scoliodon in Southeast Asia and Indian waters is warranted given the high fishing pressure exerted [58].…”

“…Nearshore elasmobranchs generally have limited dispersal capabilities [4]. For instance, the bambooshark Chiloscyllium punctatum [11] and the stingray Neotrygon species [12], both of which are small, show regional population subdivisions with limited genetic mixing throughout the Indo-West Pacific. When geographic barriers and the lack of suitable contiguous habitats are combined with a proclivity not to disperse, allopatric speciation becomes more likely.…”

Environmental and geographical factors structure cauliflower coral's algal symbioses across the Indo‐Pacific

“…Prior studies on the factors structuring marine invertebrate communities suggest that despite high potential for long‐distance dispersal with oceanic currents, regional differentiation can often arise in response to local environmental conditions (e.g. Cineas & Dolédec, 2022; Coppard et al, 2021; Hirschfeld et al, 2021; Lessios et al, 2003; Lim et al, 2021; Lopes da Silva Ferrette et al, 2021; Pappalardo et al, 2015; van der Ven et al, 2021; Wepfer et al, 2020). In particular, the Indo‐Pacific has served as a key area of study for understanding how current species distributions can be structured by the complex interplay between contemporary environmental pressures and historical patterns of gene flow (see Benzie, 1999; Crandall et al, 2019; Lessios et al, 2001).…”