Biologically representative and well-connected marine reserves enhance biodiversity persistence in conservation planning

Current methods in conservation planning for promoting the persistence of biodiversity typically focus on either representing species geographic distributions or maintaining connectivity between reserves, but rarely both, and take a focal species, rather than a multispecies, approach. Here, we link prioritization methods with population models to explore the impact of integrating both representation and connectivity into conservation planning for species persistence. Using data on 288 Mediterranean fish species with varying conservation requirements, we show that: (1) considering both representation and connectivity objectives provides the best strategy for enhanced biodiversity persistence and (2) connectivity objectives were fundamental to enhancing persistence of small-ranged species, which are most in need of conservation, while the representation objective benefited only wide-ranging species. Our approach provides a more comprehensive appraisal of planning applications than approaches focusing on either representation or connectivity, and will hopefully contribute to build more effective reserve networks for the persistence of biodiversity

Geographic distance, water circulation and environmental conditions shape the biodiversity of Mediterranean rocky coasts

11 páginas, 2 tablas, 3 figuras.Ecological connectivity is important for effective marine planning and biodiversity conservation. Our aim was to identify factors important in influencing variation in benthic community structure on shallow rocky reefs in 2 regions of the Mediterranean Sea with contrasting oceanographic regimes. We assessed beta (β) diversity at 146 sites in the littoral and shallow sublittoral from the Adriatic/Ionian Seas (eastern region) and Ligurian/Tyrrhenian Seas (western region) using a null modelling approach to account for variation in species richness. The distance decay relationship between species turnover within each region and geographic distance by sea was determined using generalised linear models. Mantel tests were used to examine correlations between β diversity and connectivity by ocean currents, estimated from Lagrangian dispersal simulations. Variation in β diversity between sites was partitioned according to environmental and spatial components using a distance-based redundancy approach. Species turnover along a gradient of geographic distance was greater by a factor of 3 to 5 in the western region than the eastern region, suggesting lower connectivity between sites. β diversity was correlated with connectivity by ocean currents at both depths in the eastern region but not in the western region. The influOPEN ACCESS ence of spatial and environmental predictors of β diversity varied considerably between regions, but was similar between depths. Our results highlight the interaction of oceanographic, spatial and environmental processes influencing benthic marine β diversity. Persistent currents in the eastern region may be responsible for lower observed β diversity compared to the western region, where patterns of water circulation are more variable.This work was supported by the European Community’s 7th Framework Programme (FP7/ 2007−2013) under Grant Agreement No. 287844 for the project ‘Towards COast to COast NETworks of marine protected areas (from the shore to the high and deep sea), coupled with sea-based wind energy potential (CoCoNet)’.Peer reviewe

New insights on the population genetic structure of the great scallop (Pecten maximus) in the English Channel coupling microsatellite data and demogenetic simulations.

International audienceThe great scallop (Pecten maximus) is a commercially important bivalve in Europe, particularly in the English Channel, where fisheries are managed at regional and local scales through the regulation of fishing effort. In the long term, knowledge about larval dispersal and gene flow between populations is essential to ensure proper stock management. Yet, previous population genetic studies have reported contradictory results. In this study, scallop samples collected across the main fishing grounds along the French and English coasts of the English Channel (20 samples with temporal replicates for three sites,n= 1059 individuals), and the population genetic structure was analysed using 13 microsatellite loci. Coupling empirical genetic data with demogenetic modelling based on a biophysical model simulating larval exchanges among scallop beds revealed a subtle genetic differentiation between south-west English populations and the rest of the English Channel, which was consistent with larval dispersal simulations. The present study provides a step forward in the understanding of great scallop population biology in the English Channel, underlining the fact that even in a context of potentially high gene flow and recent divergence times since the end of the last glacial maximum, weak but significant spatial genetic structure can be identified at a regional scale

Overview and progress of consortium research related to the biology, ecology and aquaculture of rabbitfish

editorial reviewedCoastal habitats support global fisheries by ensuring the survival of juvenile fishes. These habitats constitute one of the fishing areas targeted by small-scale fishermen in the least developed countries, including Madagascar. The accessibility of these habitats at low tides makes it an ideal fishing area for mosquito seine nets as observed for instance in SW Madagascar and beach seining in Kenya. However, this practice negatively impacts fisheries production due to catches of high numbers of juveniles, in Madagascar and Kenya mostly composed of shoemaker spinefoot rabbitfish (Siganus sutor). Despite Malagasy laws that forbid the deployment of mosquito seine nets, fishermen continue with their use. In Kenya, the beach seines have been outlawed but enforcement remains a challenge. This context highlights the need for management measures and alternative sources of income for a sustainable use of marine resources and for improving the fishermen livelihood. The ongoing consortium research entitled “Fish juvenile recruitment in coastal habitats of western Indian Ocean” was funded by MASMA program administered by WIOMSA. It is an interdisciplinary research program intending to understand recruitment patterns of shoemaker spinefoot rabbitfish (Siganus sutor) in coastal habitats of Kenya and Madagascar. It explores evidence-based solutions for improving the welfare of coastal communities and sustainable use of marine resources. Research activities were divided into four work packages. In WP1, Siganus sutor recruitment patterns in coastal habitats were targeted to identify the nursery ground and recruitment periods. It is based on juvenile fish sampling at four coastal habitats (mangroves, seagrass meadows, intermediate areas and seagrass associated with the coral reef) in Madagascar during twelve months. In WP2, sampling for the analysis of the population connectivity of S. sutor for detecting the sources of juveniles in the coastal habitats at five sites along the western coast of Madagascar was completed. In WP3, ecological models for predicting the arrival of newly settled S. sutor will be based on historical and newly collected data (WP1) using the random forests algorithm. Predictors are composed of remotely sensed oceanic conditions and a post-larval supply index calculated from post-larval sampling in the coastal habitats using light-traps. Like juvenile sampling, post-larval sampling was performed three nights per month which will cover all the juvenile sampling periods. In WP4, fish feeding behavior is studied and experiments on capture-based juvenile fish grow-out are ongoing at the Belaza aquaculture facilities (Toliara, Madagascar). Eight fish grow-out treatments focusing on three stocking densities, three fish diets, and pond dimensions are being tested. In WP1, about 5,720 juvenile individuals were obtained from 120 juvenile fish samples. The standard length of each of these individuals were measured for analyzing the spatial distribution of S. sutor. The nursery ground and recruitment seasons for S. sutor emerged from our research. The findings will be presented orally by PhD student Helga Berjulie Ravelohasina during the symposium. In addition, about 360 epifaunal community samples were obtained between July 2021 and April 2022. The spatial distribution of abundance, diversity and richness of epifauna associated with seagrass will be presented in a poster by MSc student Mory Justino. In WP2, at each location, 45 individuals were sampled, for a total of 225 adults for Madagascar and 180 from Kenya. Genotyping is in progress. In WP3, monitoring of the newly settled fish, in parallel with post-larval sampling, is in progress and should be completed by June 2022. In meantime, the extraction of remotely sensed oceanic conditions covering the sampling periods is being processed with R programming for the period. In WP4, preliminary results on fish grow-out identified the best fish diet and the most optimal stocking density at the smallest size (about 2 cm of standard length). More details related to these findings will be presented in a poster by master student Nandrianina Maminantenaina. In addition, the gut content and stage isotopes of three ontogenetic stages (i.e. post-larvae, juvenile, and adult) of S. sutor were analysed the natural trophodynamics. The findings are based on 1160 gut contents and muscle tissue samples collected during the warm (October 2021 to February 2022) and cool season (May to August 2022). The potential nursery areas and the main recruitment seasons of Siganus sutor were identified. The oral presentation entitled “The potential nursery areas and recruitment season of S. sutor in Madagascar” by Helga Berjulie Ravelohasina will provide further details of our findings. The variability of food availability related to epifauna concentration will be known in the poster on Mory Justino. The most optimal fish diet as well as the optimal stocking density will be presented in a separate poster entitled “Density and fish diet effect on rabbitfish growth in controlled systems” presented by Nandrianina Maminantenaina.Biology, ecology and aquaculture of rabbitfish14. Life below water2. Zero hunger11. Sustainable cities and communitie

Cross-ocean patterns and processes in fish biodiversity on coral reefs through the lens of eDNA metabarcoding

Increasing speed and magnitude of global change threaten the world's biodiversity and particularly coral reef fishes. A better understanding of large-scale patterns and processes on coral reefs is essential to prevent fish biodiversity decline but it requires new monitoring approaches. Here, we use environmental DNA metabarcoding to reconstruct well-known patterns of fish biodiversity on coral reefs and uncover hidden patterns on these highly diverse and threatened ecosystems. We analysed 226 environmental DNA (eDNA) seawater samples from 100 stations in five tropical regions (Caribbean, Central and Southwest Pacific, Coral Triangle and Western Indian Ocean) and compared those to 2047 underwater visual censuses from the Reef Life Survey in 1224 stations. Environmental DNA reveals a higher (16%) fish biodiversity, with 2650 taxa, and 25% more families than underwater visual surveys. By identifying more pelagic, reef-associated and crypto-benthic species, eDNA offers a fresh view on assembly rules across spatial scales. Nevertheless, the reef life survey identified more species than eDNA in 47 shared families, which can be due to incomplete sequence assignment, possibly combined with incomplete detection in the environment, for some species. Combining eDNA metabarcoding and extensive visual census offers novel insights on the spatial organization of the richest marine ecosystems

Estimation et analyse de la taille efficace de populations structurées en classes d'âge ou en stades

Effective population size Ne is a central parameter in evolutionary and conservation biology and can be estimated with demographic- and genetic-based methods. The objective of this thesis was to analyze the effects of life-history on Ne in species with overlapping generations using demographic models. One demographic and two genetic estimators were used to derive Ne in the endangered perennial plant Eryngium alpinum. The three methods gave considerably different estimates. The differences could be attributed to the difficulty in obtaining al the necessary data needed in the demographic model, but also to the reduced precision of genetic estimators when dealing with small genetic sample sizes. Demographic models nonetheless permitted identifying the effect of lifehistory on Ne through elasticity and sensitivity analyses. Numerical elasticity was employed to study the effect of stage-specific vital rates on Ne in E. alpinum and the endangered perennial plant Dracocephalum austriacum. The derived elasticity patterns were often, but not always, similar in populations with comparable demography. One demographic model was then analysed in detail to derive analytically an expression for the sensitivity of Ne/N to age-specific vital rates. This expression was used to study Ne/N in three species differing in their survivorship curves (humans, sparrows and barnacles). In this way, the differences in the sensitivity patterns among the three species could be attributed to specific components of the life-cycle. This thesis demonstrates that demographic models are powerful methods to understand the effects of the life-history on Ne and could be useful tools to complement genetic estimators when sufficient ecological and demographic data are available. The next step will be to generalize the observed elasticity and sensitivity patterns using a comparative approach on a large number of populations, which will be possible thanks to the quick accumulation of large amounts of demographic and genetic data on a great number of species.La taille efficace des populations, Ne, est un paramètre central en biologie de la conservation et en biologie évolutive et peut être estimée avec des méthodes démographiques et génétiques. L'objectif de cette thèse a été l'analyse des effets de l'histoire de vie sur Ne dans des espèces à générations chevauchantes en utilisant des modèles démographiques. Un modèle démographique et deux estimateurs génétiques ont été utilisés pour dériver Ne dans des population d' Eryngium alpinum, une plante pérenne et menacée. Les trois méthodes ont donné des estimations considérablement différentes. Les différences ont pu être attribuées à la difficulté d'obtenir toutes les données nécessaires au modèle démographique, mais aussi à la faible précision des estimateurs génétiques quand ils sont appliqués à des jeux de données limités. Les modèles démographiques ont cependant permis l'identification des effets de l'histoire de vie sur Ne à travers des analyses de sensibilité et d'élasticité. L'élasticité numérique a été utilisée pour étudier les effets sur Ne de taux vitaux stadespécifiques dans E. alpinum et dans Dracocephalum austriacum, une plante alpine pérenne et menacée. Les patrons d'élasticité dérivés étaient souvent, mais pas toujours, similaires dans des populations à démographie comparable. Ensuite, un modèle démographique a été analysé en détail pour dériver analytiquement une expression pour la sensibilité de Ne/N aux taux vitaux âgespécifiques. Cette expression a été utilisée pour étudier Ne/N dans trois espèces qui diffèrent dans leur patron de courbe de survie (humains, bruants et balanes). Les différences des patrons de sensibilité entre ces trois espèces ont pu être ainsi attribuées à des composantes spécifiques du cycle de vie. Cette thèse montre que les modèles démographiques sont des méthodes utiles pour comprendre les effets de l'histoire de vie sur Ne et qu'ils pourraient être des outils puissants pour complémenter les estimateurs génétiques quand des données écologiques et démographiques sont disponibles en quantité suffisante. L'étape suivante sera la généralisation des patrons de sensibilité et d'élasticité observés en utilisant une approche comparative sur un grande nombre de populations, ce qui sera possible grâce à la rapide accumulation de grandes quantités des données démographiques et génétiques sur un grand nombre d'espèces

Demography of natural populations of A. alpina across an elevational gradient

International audienc