Genomic Analyses Suggest Strong Population Connectivity Over Large Spatial Scales of the Commercially Important Baitworm, Australonuphis Teres (Onuphidae)
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CSIRO PUBLISHING Marine and Freshwater Research Short Communication https://doi.org/10.1071/MF20044 Genomic analyses suggest strong population connectivity over large spatial scales of the commercially important baitworm, Australonuphis teres (Onuphidae) Amanda Padovan A,B,I, Rowan C. ChickC, Victoria J. ColeC, Ludovic DutoitD, Patricia A. HutchingsE,F, Cameron JackG and Ceridwen I. FraserA,H AFenner School of Environment and Society, Building 44, Australian National University, Canberra, ACT 2601, Australia. BCSIRO, Black Mountain Science and Innovation Park, Clunies Ross Street, Canberra, ACT 2601, Australia. CNew South Wales Department of Primary Industries, Port Stephens Fisheries Institute, Taylors Beach, NSW 2316, Australia. DDepartment of Zoology, University of Otago, 340 Great King Street, Dunedin, 9016, New Zealand. EAustralian Museum Research Institute, Australian Museum, 1 William Street, Sydney, NSW 2010, Australia. FDepartment of Biological Sciences, Macquarie University, North Ryde, NSW 2109, Australia. GANU Bioinformatics Consultancy, John Curtin School of Medical Research, Australian National University, Acton, ACT 2601, Australia. HDepartment of Marine Science, University of Otago, PO Box 56, Dunedin, 9054, New Zealand. ICorresponding author. Email: amanda.padovan@csiro.au Abstract. Barriers to dispersal can disrupt gene flow between populations, resulting in genetically distinct populations. Although many marine animals have potential for long-distance dispersal via a planktonic stage, gene flow among populations separated by large geographic distances is not always evident. Polychaetes are ecologically important and have been used as biological surrogates for marine biodiversity. Some polychaete species are used as bait for recreational fisheries, with this demand supporting commercial fisheries for polychaetes to service the retail bait market. However, despite their ecological and economic importance, very little is known about the life history or population dynamics of polychaetes, and few studies have used genetic or genomic approaches to understand polychaete population connectivity. Here, we investigate the population structure of one commonly collected beachworm species used for bait on the eastern coast of Australia, namely, Australonuphis teres, by using genome-wide single-nucleotide polymorphism data. We sampled A. teres from hierarchical nested spatial scales along 900 km of the coast in New South Wales. We identified six genetic groups, but there was no clear geographic pattern of distribution. Our results suggest that there is considerable gene flow among the sampled populations. These high-resolution genomic data support the findings of previous studies, and we infer that oceanographic processes promote genetic exchange among polychaete populations in south-eastern Australia. Additional keywords: admixture, fisheries, genotype-by-sequencing, management, polychaete, population structure, SNP. Received 11 February 2020, accepted 27 April 2020, published online 21 May 2020 Introduction larval duration along with physical and ecological processes Life history, particularly the larval stage, and environmental can greatly affect the likelihood of successful dispersal and influences govern biodiversity and population structure in the population connectivity for marine species (Thiel and Gutow marine environment (Thorrold 2006; Chan et al. 2018). 2005a, 2005b; Cowen and Sponaugle 2009; Riginos et al. Understanding population connectivity, size and structure is 2011; Kinlan and Gaines 2003). Despite evidence of strong critical for effective management of marine resources. Pelagic population connectivity in some species (Shulman and Journal compilation Ó CSIRO 2020 Open Access CC BY www.publish.csiro.au/journals/mfr 2 Marine and Freshwater Research A. Padovan et al. Bermingham 1995; Roberts 1997; Cowen et al. 2007), many 2015). However, this latter research was based only on small other marine taxa, even those with apparently high dispersal fragments of mitochondrial and nuclear loci, which were not of potential, show surprisingly little evidence for gene flow a high-enough resolution to enable assessment of whether among disjunct populations (Dibacco et al. 2006; Purcell et al. population connectivity was ongoing or merely recent. The 2006; Froukh and Kochzius 2007; Marko et al. 2007; Temby connectivity of populations of polychaetes along Australian et al. 2007; Miller et al. 2009, 2014; Xuereb et al. 2018). There coasts, thus, remains largely unknown, yet, such knowledge is is, thus, a growing recognition that marine systems are not all of considerable importance for managing the sustainable open and interconnected (Dennis and Hellberg 2010; Karsenti harvest of beachworms and other polychaete bait species. et al. 2011; Iacchei et al. 2013).Definingthescaleofcon- Here, we use genomic approaches to investigate population nectivity and determining the factors that influence gene flow structure of the polychaete worm A. teres at multiple nested are critical for understanding population dynamics and genetic spatial scales (i.e. sites separated by kilometres, beaches sepa- structure of marine species, and for developing effective rated by tens of kilometres, and regions separated by hundreds of management strategies to mitigate anthropogenic effects on kilometres) along 900 km of the New South Wales (NSW) coast populations and ecosystems (Giangrande et al. 2005; Waples in Australia. We generated a single-nucleotide polymorphism and Punt 2008). (SNP) dataset via genotype-by-sequencing. The three possible Polychaete worms are common in intertidal ecosystems findings are as follows: (1) genetic homogeneity in all A. teres (Cole et al. 2007, 2017), and are good indicators of species samples across spatial scales, which would indicate a single richness and community patterns in benthic invertebrate assem- panmictic population and considerable gene flow along the blages (Olsgard and Somerfield 2000; Giangrande et al. 2005). coast, (2) genetically distinct populations of A. teres, indicating Indeed, polychaetes have been used as biological surrogates for negligible gene flow among populations, or (3) a mixed result, marine biodiversity (Olsgard et al. 2003; Shokri et al. 2009). with both similarities and differences among populations, Among benthic groups, polychaetes are one of the best indica- indicating some gene flow. This study is one of the first to tors of environmental disturbance, because there are both use large-scale genomic data to assess population connectivity sensitive and tolerant species across pristine and heavily dis- in polychaetes. turbed habitats (Olsgard and Somerfield 2000). Polychaetes are important members of the marine food chain; they can act as Materials and methods predators, scavengers and grazers of diverse other organisms, or Field methods for sampling Australonuphis teres as prey for a variety of bird, fish and crustacean species (Fauchald and Jumars 1979; Jumars et al. 2015). Populations of A. teres were sampled in the Eastern Warm In addition to their ecological importance, many species of Temperate biogeographic zone of the NSW coast. Three bior- polychaetes are an important bait resource for recreational egions were selected and we designated them as North, Central fishers (Cole et al. 2018). As with any fisheries resource, and South, corresponding to the Tweed–Moreton (288S– management relies on information about stock size and popula- 30.58S), Manning (30.58S–30.758S) and Batemans (34.68S– tion connectivity (Cowen et al. 2007; Fogarty and Botsford 36.68S) bioregions respectively. A fully nested design was used 2007). In Australia, recreational and commercial fishers target to obtain samples of A. teres. In each of the three regions beachworms directly for bait or for sale into the bait market (separated by hundreds of kilometres), two beaches (separated respectively. Beachworms, including the ‘kingworm’ or by tens of kilometres), each with two randomly chosen sites ‘stumpy’ Australonuphis teres (Onuphidae), inhabit high- (separated by kilometres), 45 individuals were collected. The energy sandy beaches from Maroochydore, Queensland to posterior end (the last 20 mm of the body) was removed and Lakes Entrance, Victoria (Paxton 1979). Although little is placed in 98% ethanol and stored below À188C for subsequent known about their population biology, they are thought to be analysis. Beaches were selected as those where commercial À1 broadcast spawners, have been recorded to be sexually mature harvesting of beachworms occurs (.0.6 t year commercial at 420 mm in length (Paxton 1979), and are suspected to catch over the previous 2 years). Samples of the population of breed multiple times a year (Paxton 1986). As adults, dispersal A. teres were obtained through beach sampling, whereby a mesh of A. teres is relatively limited (Paxton 1979), with large bag containing a fish frame was dragged along the sand in the topographic structures (e.g. headlands and river mouths) that swash zone to entice the worms to emerge, and any worms that separate sandy beaches acting as physical barriers to dispersal. surfaced were collected by hand. Despite their ecological and economic importance, few population genetic (and fewer population genomic) studies DNA extraction, library preparation and sequencing have yet been conducted for polychaetes. In one genetic Tissue samples were removed from ethanol, dried and sub- study from the USA, the baitworm Glycera dibranchiata sampled. DNA was extracted