Molecular Evidence of Distinct Evolutionary Units in the Sandhopper Talorchestia Capensis (Amphipoda, Talitridae) Along South African Coasts
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Hydrobiologia (2016) 779:35–46 DOI 10.1007/s10750-016-2797-4 PRIMARY RESEARCH PAPER Molecular evidence of distinct evolutionary units in the sandhopper Talorchestia capensis (Amphipoda, Talitridae) along South African coasts Simone Baldanzi . Gavin Gouws . Nigel P. Barker . Sara Fratini Received: 22 January 2016 / Revised: 20 April 2016 / Accepted: 21 April 2016 / Published online: 12 May 2016 Ó Springer International Publishing Switzerland 2016 Abstract Marine geographical and ecological bar- Talitridae) represents the most abundant species of riers often reflect intraspecific genetic discontinuities sandhoppers along the South African coasts. To define among populations which may experience different population structure of T. capensis, we used a selective pressures and undergo evolutionary diver- mitochondrial marker (the cytochrome oxidase sub- gence. While the phylogeography of marine intertidal unit I gene, COX1). T. capensis showed a clean invertebrates across the Atlantic/Indian Ocean transi- population structure with three main haplogroups tion received more attention, the population genetic genetically well separated, although this separation is structures of supralittoral direct developers across not perfectly in line with geographical boundaries such transition area have been poorly investigated. described for this area. The presence of separate Sandhoppers are supralittoral invertebrates charac- evolutionary significant units is also confirmed by the terised by a direct developmental mode (low dispersal shape of mismatch distribution, as well as the p ability), and Talorchestia capensis (Amphipoda, distance values among groups. The overall results confirm the importance of mtDNA to retrieve infor- mation on the evolutionary history of species. This Handling editor: Diego Fontaneto study suggests the evidence of a complex-species for this sandhoppers, which have never been considered S. Baldanzi before, providing fundamental basis for further Estacio´n Costera de Investigaciones Marinas, Pontificia Universidad Catolica de Chile, Osvaldo Marin 1672, studies. Las Cruces Comuna El Tabo, Chile Keywords mtDNA marker Á COX1 Á Cryptic & S. Baldanzi ( ) Á G. Gouws species Á Population genetics Á Sandy-beach ecology South African Institute for Aquatic Biodiversity (SAIAB), Somerset Street, Grahamstown, South Africa e-mail: [email protected] N. P. Barker Introduction Molecular Ecology and Systematics Group, Botany Department, Rhodes University, Lucas Avenue, Grahamstown, South Africa In marine systems, geographical discontinuities are often mirrored by intraspecific genetic discontinuities S. Fratini among populations (Benzie, 1999), occurring where Department of Biology, Universita` degli Studi di Firenze, Via Madonna del Piano 6, Sesto Fiorentino, Florence, past or present-day barriers to dispersal allow for Italy genetic differentiation and prevent homogenisation 123 36 Hydrobiologia (2016) 779:35–46 due to gene flow within a species (Teske et al., 2011). coincide with the disjunctions between these four In the marine realm, oceanographical conditions are provinces (Fig. 1; Teske et al., 2007; Zardi et al., the major drivers of phylogeographical breaks (Collin, 2007; Von der Heyden et al., 2008; Teske et al., 2009, 2001; Sanford et al., 2003; Tellier et al., 2009; Zakas 2011). Despite this general pattern, differences in the et al., 2009), although differences in abundance, positions of phylogeographical discontinuities are timing of reproduction, life history traits, population common among South African marine invertebrates and recruitment dynamics, and physiological traits can (Teske et al., 2011), especially between planktonic and also regulate such discontinuities (Broitman et al., direct developers (Teske et al., 2007). Such disconti- 2001; Rivadeneira et al., 2002; Ragionieri et al., 2009; nuities may also reflect different Evolutionary Signif- Carson et al., 2010; Kelly & Palumbi, 2010; McQuaid, icant Units (ESU’s sensu Moritz, 1994), as well as 2010). cryptic species. For example, Teske et al. (2009), In coastal areas, phylogeographical breaks in investigating the phylogeography of the sand prawn marine organisms have mostly been associated with Callianassa krausii along the South African coast, coastal currents and eddies, river discharge and suggested the existence of distinct ESUs, possibly upwelling cells, which all interfere with along-shore related to environmental discontinuity between the dispersal (Pelc et al., 2009; Teske et al., 2011; Brante tropical and subtropical regions. et al., 2012). In South Africa, coastal species are often Sandhoppers, supralittoral amphipods of the family divided into genetic lineages distributions of which are Talitridae, are direct developers (i.e. no free-swim- linked to the marine biogeographical provinces of ming larval form, eggs are brooded and hatch as southern Africa (the cool temperate, warm temperate, juveniles with an adult-like form), showing low active subtropical and tropical provinces, see Teske et al., dispersal ability (Dahl, 1946; Wildish, 1970). Due to 2011). The major phylogeographical breaks have been the absence of a dispersive stage, through which active identified at three main localities that, in most cases, dispersal occurs or by which passive dispersal is Fig. 1 The South African coast, showing model organism, sites between the Atlantic and Indian Oceans, Cape Bioregion; Algoa of collection, current systems, bioregions and transition zones. Bay to Wild Coast in the Agulhas Bioregion and St Lucia, in the PN Port Nolloth, BB Betty’s Bay, GB Gansbaai, SB Still Bay, Subtropical Bioregion. Bioregions are reported in the grey scale GOU Gouritzmond, GLE Glentana, PA Port Alfred, PSJ Port St. bar at the bottom of the figure. CT cool-temperate bioregion, Johns. Black-dashed circles represent the phylogeographical C Cape Bioregion, WT warm-temperate bioregion, ST subtrop- transition zones (Teske et al., 2011): Agulhas, at the transition ical bioregion 123 Hydrobiologia (2016) 779:35–46 37 facilitated by oceanographical conditions, direct et al., 2011). PSJ is the only location within the developers generally show low levels of population subtropical region and it represents the eastern limit connectivity, reduced mixing among local populations of the spatial distribution of T. capensis. Locations and, consequently, clear population genetic structure were chosen on the basis of accessibility and the (Pavesi et al., 2013; Fanini & Lowry, 2014). Notwith- presence of animals. Figure 1 shows the locations, standing, direct-developing species can potentially bioregions and the South African current systems, rely on rafting as the main long distance dispersal the Agulhas and Benguela Currents, which dominate mechanism (Thiel & Gutow, 2005a, b). However, such the south-east and the south-west coasts, respec- a mechanism has rarely been demonstrated for talitrids tively. Between 6 and 15 individuals per location (Persson, 2001); in fact, Platorchestia platensis were collected by hand and stored in 100% ethanol (Krøyer, 1845) is the only talitrid with strong evidence (Table 1). of rafting as a dispersal mechanism (Simpson, 2011). Talorchestia capensis (Dana, 1853) is a talitrid DNA extraction, amplification and sequencing species showing a widespread distribution along the South African coast (Baldanzi et al., 2013), encom- DNA was extracted from the telson of the animals passing four South African bioregions (Lombard, following a CTAB (cetyltrimethyl ammonium bro- 2004) characterised by differing environments. Fur- mide) method (Doyle & Doyle, 1987). A portion of the thermore, individuals of T. capensis from locations mitochondrial cytochrome c oxidase subunit I gene found within this range showed different thermal (mtDNA COX1) was amplified using polymerase tolerances, likely shaped by local environmental chain reaction (PCR). The forward primer CrustCOIF conditions (Baldanzi et al., 2015). Both these biogeo- 50 and reverse primer PeracCOIR 50 (Teske et al., graphical and ecophysiological characteristics of T. 2007) were used to amplify all the specimens for all capensis suggest potential genetic differentiation populations. The PCR profile comprised an initial among separated populations. Given that, we investi- denaturation step of 3 min at 94°C, followed by 35 gated the population genetic structure and demo- cycles of denaturation (30 s at 94°C), annealing (45 s graphical history of T. capensis using mitochondrial at 48–50°C) and extension (75 s at 72°C); and a final DNA as a molecular marker. We expected that T. extension step of 10 min at 72°C. PCR products were capensis should show clear population structure, as purified and cleaned with a DNA clean up kit (MSBÒ reported for many other sandhoppers (Pavesi et al., Spin PCRapace, StratecÒ), cycle sequenced both in the 2011, 2012, 2013). We envisage that Talorchestia forward and reverse direction using the BigDye capensis should show an intraspecific phylogeny Terminator v.3.1 Cycle Sequencing kit (Applied associated with defined geographical areas, but, Biosystems) and sequenced on an ABI 3100 genetic nonetheless, such genetic breaks would not coincide analyser. The sequences were edited using the soft- with South Africa’s bioregions, in agreement with ware SEQUENCHER v4.8 (Gene Code Corporation, Teske et al. (2011) assertion for local species with low Ann Arbor, MI, USA), and edited sequences were dispersal ability. aligned using the MUSCLE algorithm in MEGA v5.05 (Tamura et al., 2011). Materials and methods Data