Populations Of Marine Species Research Articles

Genomic survey of edible cockle (Cerastoderma edule) in the Northeast Atlantic: A baseline for sustainable management of its wild resources.

Knowledge on correlations between environmental factors and genome divergence between populations of marine species is crucial for sustainable management of fisheries and wild populations. The edible cockle (Cerastoderma edule) is a marine bivalve distributed along the Northeast Atlantic coast of Europe and is an important resource from both commercial and ecological perspectives. We performed a population genomics screening using 2b‐RAD genotyping on 9309 SNPs localized in the cockle's genome on a sample of 536 specimens pertaining to 14 beds in the Northeast Atlantic Ocean to analyse the genetic structure with regard to environmental variables. Larval dispersal modelling considering species behaviour and interannual/interseasonal variation in ocean conditions was carried out as an essential background to which compare genetic information. Cockle populations in the Northeast Atlantic displayed low but significant geographical differentiation between populations (F ST = 0.0240; p < 0.001), albeit not across generations. We identified 742 and 36 outlier SNPs related to divergent and balancing selection in all the geographical scenarios inspected, and sea temperature and salinity were the main environmental correlates suggested. Highly significant linkage disequilibrium was detected at specific genomic regions against the very low values observed across the whole genome. Two main genetic groups were identified, northwards and southwards of French Brittany. Larval dispersal modelling suggested a barrier for larval dispersal linked to the Ushant front that could explain these two genetic clusters. Further genetic subdivision was observed using outlier loci and considering larval advection. The northern group was divided into the Irish/Celtic Seas and the English Channel/North Sea, while the southern group was divided into three subgroups. This information represents the baseline for the management of cockles, designing conservation strategies, founding broodstock for depleted beds and producing suitable seed for aquaculture production.

Will life find a way? Evolution of marine species under global change.

Projections of marine biodiversity and implementation of effective actions for its maintenance in the face of current rapid global environmental change are constrained by our limited understanding of species’ adaptive responses, including transgenerational plasticity, epigenetics and natural selection. This special issue presents 13 novel studies, which employ experimental and modelling approaches to (i) investigate plastic and evolutionary responses of marine species to major global change drivers; (ii) ask relevant broad eco‐evolutionary questions, implementing multiple species and populations studies; (iii) show the advantages of using advanced experimental designs and tools; (iv) construct novel model organisms for marine evolution; (v) help identifying future challenges for the field; and (vi) highlight the importance of incorporating existing evolutionary theory into management solutions for the marine realm. What emerges is that at least some populations of marine species have the ability to adapt to future global change conditions. However, marine organisms’ capacity for adaptation appears finite, due to evolutionary trade‐offs and possible rapid losses in genetic diversity. This further corroborates the idea that acquiring an evolutionary perspective on how marine life will respond to the selective pressure of future global changes will guide us in better identifying which conservation efforts will be most needed and most effective.

Quantification of larval traits driving connectivity: the case of Corallium rubrum (L. 1758)

Larval dispersal is the process enabling connectivity between populations of marine species with a sedentary adult stage. This transportation results from the coupling between flow and larval biological traits. This experimental study aims to quantify these larval biological traits, namely pelagic larval duration (PLD), buoyancy and larval vertical motility behavior, for Corallium rubrum. Larval vertical motility behavior was split into active behavior (swimming) and passive behavior (free fall). A particle-tracking routine was applied to video recordings of the active and passive motility behavior of C. rubrum larvae to quantify their free fall speeds, swimming activity frequency and swimming speeds. The experiment was repeated under different light conditions and at different larval ages. PLD ranged from 16 days (95 % survival) to 42 days (5 % survival). Larvae exhibited negative buoyancy with a free fall speed decreasing linearly with age, at a velocity varying from −0.09 ± 0.026 cm s−1 on day 1 to −0.05 ± 0.026 cm s−1 on day 10. No significant difference was found either in the activity frequency or in the mean swim velocities during active periods for age (up to 12 days old) or under different light conditions. C. rubrum larvae maintained active swimming behavior for 82 % of the time. This activity frequency was combined with age-varying free fall periods in the motility behavior model extrapolated up to 15 days old, resulting in a mean upward speed that increased from 0.045 cm s−1 (day 1) to 0.056 cm s−1 (day 15). This larval motility behavior, combined with the extended PLD, confers on C. rubrum larvae an unsuspectedly high dispersive potential in open waters.

Theoretical limits to the correlation between pelagic larval duration and population genetic structure

Increasing dispersal duration should result in increasing dispersal distance, facilitating higher gene flow among populations. As such, it has long been predicted that genetic structure (e.g. F(ST) ) among populations of marine species should be strongly correlated with pelagic larval duration (PLD). However, previous studies have repeatedly shown a surprisingly poor correspondence. This result has been frequently interpreted as evidence for larval behaviours or physical oceanographic processes that result in larvae failing to reach their dispersal potential, or error inherent in estimating PLD and F(ST) . This study employed a computer modelling approach to explore the impacts of various uncertainties on the correlation between measures of genetic differentiation such as F(ST) and PLD. Results indicate that variation resulting from PLD estimation error had minor impacts on the correlation between genetic structure and PLD. However, variation in effective population size between species, errors in F(ST) estimation and non-equilibrium F(ST) values all had major impacts, resulting in dramatically weaker correlations between PLD and F(ST) . These results suggest that poor correlations between PLD and F(ST) may result from variation and uncertainty in the terms associated with the calculation of F(ST) values. As such, PLD may be a much stronger determinant of realized larval dispersal than suggested by the weak-to-moderate correlations between PLD and F(ST) reported in empirical studies.

Imprints from genetic drift and mutation imply relative divergence times across marine transition zones in a pan-European small pelagic fish (Sprattus sprattus).

Geographic distributions of most temperate marine fishes are affected by postglacial recolonisation events, which have left complex genetic imprints on populations of marine species. This study investigated population structure and demographic history of European sprat (Sprattus sprattus L.) by combining inference from both mtDNA and microsatellite genetic markers throughout the species' distribution. We compared effects from genetic drift and mutation for both genetic markers in shaping genetic differentiation across four transition zones. Microsatellite markers revealed significant isolation by distance and a complex population structure across the species' distribution (overall θ(ST)=0.038, P<0.01). Across transition zones markers indicated larger effects of genetic drift over mutations in the northern distribution of sprat contrasting a stronger relative impact of mutation in the species' southern distribution in the Mediterranean region. These results were interpreted to reflect more recent divergence times between northern populations in accordance with previous findings. This study demonstrates the usefulness of comparing inference from different markers and estimators of divergence for phylogeographic and population genetic studies in species with weak genetic structure, as is the case in many marine species.

Fine-scale genetic structure and inferences on population biology in the threatened Mediterranean red coral, Corallium rubrum

Identifying microevolutionary processes acting in populations of marine species with larval dispersal is a challenging but crucial task because of its conservation implications. In this context, recent improvements in the study of spatial genetic structure (SGS) are particularly promising because they allow accurate insights into the demographic and evolutionary processes at stake. Using an exhaustive sampling and a combination of image processing and population genetics, we highlighted significant SGS between colonies of Corallium rubrum over an area of half a square metre, which sheds light on a number of aspects of its population biology. Based on this SGS, we found the mean dispersal range within sites to be between 22.6 and 32.1 cm, suggesting that the surveyed area approximately corresponded to a breeding unit. We then conducted a kinship analysis, which revealed a complex half-sib family structure and allowed us to quantify the level of self-recruitment and to characterize aspects of the mating system of this species. Furthermore, significant temporal variations in allele frequencies were observed, suggesting low genetic drift. These results have important conservation implications for the red coral and further our understanding of the microevolutionary processes acting within populations of sessile marine species with a larval phase.

Panmictic population structure in the migratory marine sparid Acanthopagrus australis despite its close association with estuaries

Recent studies have revealed surprising levels of genetic structuring within populations of marine species that were previously thought to be widely dispersed. Such subdivision may reflect unexpected physical or biological barriers to dispersal, including philopatric behaviour. Here we investigate the genetic structure of the eastern Australian yellowfin bream Acanthopagrus australis—a widely distributed species that is thought to be highly dispersive but is also known to spawn in close association with estuaries. Our data from surveys of allele frequencies at 6 microsatel- lite DNA loci for 350 fish revealed high levels of genetic diversity within all sites but no genetic dif- ferentiation of groups of recruits collected from sites separated by a distance of up to 50 km (allele fre- quency differentiation: FST = 0.002, p > 0.05). Moreover, there was no differentiation of adults spread across the distributional range of the species (several 100s of kilometers, FST = 0.002). We conclude that A. australis spawning is opportunistically associated with estuaries in general, and that the spe- cies essentially forms a panmictic population with a genetic homogeneity reflecting the predicted active northwards dispersal of adults and the southwards dispersal of larvae as affected by the East- ern Australian Current.

SURVIVAL IN A CHANGING WORLD

![Figure][1] In August 2009, the International Union of Physiological Sciences (IUPS) held its 36th Congress in Kyoto in the same convention centre where the historic Kyoto Protocol was drawn up 12 years earlier. The symbolism of this coincidence was not missed by Malcolm Gordon, the Chair of