Fourth International Marine Connectivity (Imarco) Conference in Heraklion, Crete, Greece
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Fourth International Marine Connectivity (iMarCo) Conference in Heraklion, Crete, Greece - 8 to 9th October 2018 1 The challenge of asexuality in population genetics: how wrong can we be? Sophie Arnaud-Haond Ifremer, UMR MARBEC (Marine Biodiversity, Exploitation and Conservation), France In the marine realm, species structuring habitat (corals, seagrasses...) and many invertebrates often exhibit a dual reproductive system, partial asexuality. The theoretical framework in population genetics is however developed only for pure asexuals or pure sexual species and interpreting genetic data on partial asexuals is a challenge. Through mathematical development and simulations, we provide new expectations as to the genotypic and genetic composition of natural populations under an increasing range of clonality. These result call for a serious revision of the interpretation of molecular data in the literature on population genetics of partial asexual in general, and seagrasses in particular. 2 Does genomics of parasitic sea lamprey populations provide insights to the connectivity of marine hosts? Miguel Baltazar-Soares Bournemouth University The sea lamprey (Petromyzon marinus) is an ancient anadromous species and is among the last living representatives of jawless vertebrates. The life cycle is complex and includes development stages tightly linked to specific habitat needs. While adults are obligatory parasites that feed on the blood and flesh of marine or other anadromous fish species, the larvae (ammocoetes) live as free organisms in the silt-depositing zone of river banks. The migration to tidal/saltwater areas occurs progressively - from sediment bank to sediment bank - along a 7-8-year period. Full development into sexually mature parasitic individuals occurs relatively rapid, upon which attachment to potential hosts is an essential need. The intrinsic relationship between obligatory parasitism and marine-dwelling hosts allow us to test for a relationship between structure among sea-lamprey locations and a) marine fish’s biodiversity or b) population structure of predominant possible hosts as alternative hypotheses to that of complete panmixia. Here I will present first insights of a double digest RAD-seq study that screened 8 freshwater streams across the species distribution range in Europe. Approximately 200 000 loci were obtained and used to estimate genome-wide differentiation as well as preliminary correlations with biological diversity of potential hosts. 3 The hybrid zone theory, a universal framework for marine population genomics Nicolas Bierne Université de Montpellier - CNRS Most species are subdivided by hybrid zones. Overwhelming evidences support this simple claim and the analysis of genome sequences mainly strengthened and broadens it as being a universal result of population genetics. Surprisingly, however, the consequences for the interpretation of population genetics data remains mainly ignored. In this paper I intend to highlight the importance and generality of the hybrid zone framework for population genomics. First, I will argue that hybrid zones of the pre-genomic era, studied with a few markers, represented only one small fraction at the extreme of the gradient of genomic differentiation between interacting genetic backgrounds. Genome analysis has mainly identified new cryptic hybrid zones between more loosely differentiated lineages (younger) or more loosely isolated genetic backgrounds (maintained by less efficient genetic barriers). Refraining to call them hybrid zones might unfortunately distracts us from interpreting them with the help of the hybrid zone theory. Second, I will recall two important predictions of the hybrid zone framework that well explains how genetic diversity is structured in space and within genomes. (i) Hybrid zones are expected to be trapped by barriers to dispersal or by ecotones. This explains genetic-environment associations, even when past vicariance and/or partial reproductive isolation best explain the genetic differentiation. (ii) Hybrid zones are expected to act as semi-permeable barrier to gene flow. This explains the usually much higher observed variance of differentiation than the neutral expectation, and the correlation with recombination rates. Finally, I will argue that introgression tails emanating from hybrid zones should be accounted for to interpret population genomic data within apparently well- mixed biogeographic regions. There are good reasons why introgression gradients should better correlate with ecological variables or with least cost path connectivity maps than with geographic distance. My hope is that the universality of the hybrid zone framework will be recognized and better considered when interpreting genome scans and landscape genomics analyses. 4 Genomic approaches and targeted genetic markers can identify fine-scale structuring in marine fish populations. Alessia Cariani and Fausto Tinti GenoDREAM Lab, University of Bologna, Italy The eco-compatible management of marine bio-resources requires multidisciplinary and integrated scientific data, to which the genetic contribute is essential. The development of advanced tools (genomics and bioinformatic) for the analysis of complex data targets the identification and description of the evolutionary and environmental drivers of biodiversity in marine taxa and their application to the sustainable management of fishery resources. Weak signals of population structure are generally reported for most marine fish using neutral genetic markers as a consequence of high dispersal, connectivity and large population size. Recently, genome-wide studies and analysis of markers linked to functional gene regions have suggested that divergence might occur even when neutral markers provide genetic homogeneity, revealing patterns of fine-scale populations structuring in marine species. Significant correlation of allele frequencies at specific loci with environmental variables supports the hypothesis of local adaptation, often found to be in a delicate balance with gene flow. Seascape statistical analyses are useful tools to uncover the genetic basis of fine-scale genetic structuring across marine populations. Such findings highlight the importance of integrating information from multiple and independent disciplines, in order to develop explicit spatial models for defining management units and stock boundaries. 5 Abundance and distribution of the deep-sea blue and red Aristeus antennatus larvae in the North-western Mediterranean Marta Carretón, Guiomar Rotllant, Joan B. Company Institute of Marine Sciences (ICM-CSIC, Barcelona) The deep-sea blue and red shrimp Aristeus antennatus (Risso, 1816) is one of the most valuable fishing resources in the Northwestern Mediterranean, currently under a local co- management plan in the port of Palamós (Spain). Gathering information about its larval distribution is a key step for the progress of its fishing stock assessment and the establishment of well-dimensioned management measures. We here present the spatial distribution of A. antennatus larvae at the peak of the species’ spawning period (July-August) along the Spanish Mediterranean coast. Zooplankton sampling was carried out in surface waters (0.5 to 1 m depth) in the summer 2016 with a 1 m-mouth neustonic sledge (mesh size: 300 µm) over bottoms of 82 to 1840 m. Samples were rinsed in distilled water, preserved in 96% ethanol and sorted in the laboratory under a stereomicroscope. Identification of the larvae was done according to the available descriptions. Over 1000 A. antennatus larvae of all known stages were found in our samples, the first protozoea representing almost 90% of the total. Results show aggregations of larvae in the Ibiza Channel and in the northern submarine canyons, concurrent with hydrographic conditions. No larvae were found below the Ibiza Channel. These data will be useful to assess the species’ larval dispersal and validate a biohydrodynamic model of the study area. Keywords: Aristeus antennatus, larvae, ecology, fisheries 6 New insight on the population structure of Calanus finmarchicus in the North Atlantic using next-generation sequencing technologies Marvin Choquet, Irina Smolina, Galice Hoarau Faculty of Biosciences and Aquaculture, Nord University, 8049 Bodø, Norway Calanus finmarchicus is a key species for the North Atlantic Ocean food web. Dramatic demographic reduction in Calanus has been reported in Northern Oceans, as well as large- scale northward shifts, and this might likely be associated to global warming inducing perturbations in sea temperatures and in global currents functioning. Such changes among planktonic communities are expected to have a strong impact on the higher levels of the food web. Despite a well-documented life cycle, very little is known about the population genetics of this crustacean. Such knowledge is critical to understand the dynamics of C. finmarchicus populations and their ability to cope with environmental changes. In order to better understand C. finmarchicus population connectivity, we used recently developed molecular tools to investigate genome wide genetic variation for individuals from 9 locations spanning the entire range of the species. Based on a transcriptome reference available for C. finmarchicus, we selected a set of ca. 2,000 genes for which we designed short adapter sequences. Used as baits and fixed on magnetic beads, these probes were used to sequence these particular genes in a large number of individuals. Preliminary results suggest limited