Canopy-forming seaweeds, especially fucoids (Fucales, Phaeophyceae), constitute marine forests in the Mediterranean Sea that deliver key ecosystem services. However, escalating human pressures in coastal areas have led to habitat fragmentation, significantly impacting the dynamics of gene flow and evolutionary trajectories. In this study, we investigated population connectivity among 43 sites with Ericaria amentacea in the northwestern Mediterranean Sea. By integrating microsatellite genotyping and biophysical modelling, we aimed to evaluate the hypothesis that population connectivity is approximated by oceanographic connectivity, rather than coastal distance. While traditional approaches to oceanographic connectivity had focused on single-generation dispersal models, we adopted a multi-generation perspective. This involves employing a biophysical model that considers gene flow through multiple stepping-stone populations across the E. amentacea distribution and over distinct generations of dispersal. Using distance-based redundancy analysis (dbRDA), we found that multi-generation dispersal significantly contributes to genetic differentiation, surpassing the influence of coastal distance. Even so, genetic differentiation remained significant among all population pairs, suggesting that gene flow may be hindered by differential selection acting against migrants and/or obscured by the effects of local genetic drift. The latter is likely, given the species' low dispersal potential and self-compatibility, both of which promote small, spatially restricted breeding units. In addition, our results emphasized that oceanographic connectivity promoted long-distance dispersal across northern Corsica and Eastern Provence over a single generation through the drifting of fertile thalli, which might have contributed to moderate differentiation between local populations. Overall, this framework highlights the value of considering multi-generation dispersal across numerous intermediate stepping-stones for informing management strategies aimed at enhancing population connectivity and safeguarding genetic diversity in seaweeds.

Within individuals and/or species of trees, the structure and gas exchange of sun-exposed leaves from the outer part of the canopy have been found to relate to sampling height. Across species, the gas exchange of such leaves has been shown to relate to their structure and biochemical composition, but not to canopy height. Why are leaf traits related to height within tree species but not across a broader range of species? And what are the components of leaf structure involved in leaf-level carbon, water and nitrogen economies? Plant height, leaf mass per area (LMA) and its underlying components, gas exchange, leaf nitrogen and carbon isotopic discrimination were assessed for 60 species from different life and growth forms growing in the Mediterranean, spanning a wide range of height and LMA values. Contrary to previous comparisons across species, our study shows that leaves of tall plants had a high LMA, a high leaf dry matter content (LDMC) and were slightly thicker; their stomatal conductance and photosynthetic rate were low, while their intrinsic water-use efficiency (iWUE) was high. LMA was related to all gas exchange variables as well as to leaf nitrogen. These effects were mostly mediated through LDMC, with limited effects of leaf thickness. These conclusions were hardly modified when phylogeny was account for. Across species of varying life and growth forms, leaf functioning relates to both plant height and leaf structure. These results provide a generalization of previous conclusions found in trees at the intra-individual and/or intraspecific levels. Inconsistencies among previous studies with respect to plant height are likely an issue of context-dependency, which should be explicitly taken into account for a better understanding of plant form and function.Read the free Plain Language Summary for this article on the Journal blog. Au sein des individus et/ou des esp & egrave;ces d'arbres, il a & eacute;t & eacute; montr & eacute; que la structure et les & eacute;changes gazeux des feuilles expos & eacute;es au soleil dans la partie ext & eacute;rieure de la canop & eacute;e & eacute;taient li & eacute;s & agrave; la hauteur d'& eacute;chantillonnage. Entre esp & egrave;ces, il a & eacute;t & eacute; d & eacute;montr & eacute; que les & eacute;changes gazeux de ces feuilles & eacute;taient li & eacute;s & agrave; leur structure et & agrave; leur composition chimique, mais pas & agrave; la hauteur de la plante. Pourquoi les caract & eacute;ristiques des feuilles sont-elles li & eacute;es & agrave; la hauteur au sein d'une m & ecirc;me esp & egrave;ce d'arbre, alors que ce n'est pas le cas lorsque l'on compare des esp & egrave;ces diff & eacute;rentes ? Et quelles sont les composantes de la structure foliaire impliqu & eacute;es dans les & eacute;conomies du carbone, de l'eau et de l'azote des feuilles ? La hauteur des plantes, la masse surfacique des feuilles (MSF) et ses composantes sous-jacentes, les & eacute;changes gazeux, la teneur en azote et la discrimination isotopique du carbone des feuilles ont & eacute;t & eacute; & eacute;valu & eacute;s pour 60 esp & egrave;ces de diff & eacute;rentes formes de vie et de croissance se trouvant dans la r & eacute;gion m & eacute;diterran & eacute;enne, et couvrant une large gamme de valeurs de hauteur et de MSF. Contrairement aux comparaisons pr & eacute;c & eacute;dentes effectu & eacute;es entre esp & egrave;ces, notre & eacute;tude montre que les feuilles des plantes de haute stature ont une MSF & eacute;lev & eacute;e, une teneur en mati & egrave;re s & egrave;che foliaire & eacute;lev & eacute;e et sont l & eacute;g & egrave;rement plus & eacute;paisses ; leur conductance stomatique et leur vitesse de photosynth & egrave;se sont faibles, alors que leur efficacit & eacute; intrins & egrave;que d'utilisation de l'eau est & eacute;lev & eacute;e. La MSF est reli & eacute;e & agrave; toutes les variables relatives aux & eacute;changes gazeux ainsi qu'& agrave; l'azote foliaire. Ces effets sont principalement expliqu & eacute;s par des diff & eacute;rences de teneur en mati & egrave;re s & egrave;che, avec des effets limit & eacute;s de l'& eacute;paisseur des feuilles. Ces conclusions ne sont pas significativement modifi & eacute;es lorsque la phylog & eacute;nie est prise en compte. Pour des esp & egrave;ces appartenant & agrave; diff & eacute;rentes formes de vie et de croissance, nous avons montr & eacute; que le fonctionnement des feuilles & eacute;tait reli & eacute; & agrave; la fois & agrave; la structure de celles-ci et & agrave; hauteur de la plante. Ces r & eacute;sultats constituent une g & eacute;n & eacute;ralisation des conclusions obtenues sur des arbres aux niveaux intra-individuel et/ou intrasp & eacute;cifique, mais contrastent avec les & eacute;tudes pr & eacute;c & eacute;dentes conduites entre esp & egrave;ces pour ce qui est de la hauteur. Ces diff & eacute;rences pourraient s'expliquer par des effets de d & eacute;pendance au contexte, qui devraient & ecirc;tre explicitement pris en compte pour une meilleure compr & eacute;hension de la forme et de la fonction des plantes.

Cystoseira sensu lato (Class Phaeophyceae, Order Fucales, Family Sargassaceae) forests play a central role in marine Mediterranean ecosystems. Over the last decades, Cystoseira s.l. suffered from a severe loss as a result of multiple anthropogenic stressors. In particular, Gongolaria barbata has faced multiple human-induced threats, and, despite its ecological importance in structuring rocky communities and hosting a large number of species, the natural recovery of G. barbata depleted populations is uncertain. Here, we used nine microsatellite loci specifically developed for G. barbata to assess the genetic diversity of this species and its genetic connectivity among fifteen sites located in the Ionian, the Adriatic and the Black Seas. In line with strong and significant heterozygosity deficiencies across loci, likely explained by Wahlund effect, high genetic structure was observed among the three seas (ENA corrected F ST = 0.355, IC = [0.283, 0.440]), with an estimated dispersal distance per generation smaller than 600 m, both in the Adriatic and Black Sea. This strong genetic structure likely results from restricted gene flow driven by geographic distances and limited dispersal abilities, along with genetic drift within isolated populations. The presence of genetically disconnected populations at small spatial scales (< 10 km) has important implications for the identification of relevant conservation and management measures for G. barbata : each population should be considered as separated evolutionary units with dedicated conservation efforts.

The brown alga Cystoseira amentacea (Phaeophyceae, kingdom Stramenopiles) constitutes an extensive belt in the shallowest horizon of the infralittoral (the infralittoral fringe), in the Mediterranean Sea. Hydrodynamic modelling was used to infer connectivity between populations of C. amentacea of the Bay of Marseille (Provence, France, NW Mediterranean) and to test the correlation between genetic and hydrodynamic connectivity. We genotyped 183 individuals from six populations at six microsatellite loci. Current fields were computed at a fine resolution by a 3D numerical model simultaneously utilizing the local winds, the Rhone River inputs and offshore circulation. The Lagrangian trajectories of the propagules (zygotes, or rafts) were computed with the ICHTHYOP software, for both NW and SE strong wind forcing (11-12 m.s(-1)). Cystoseira amentacea displayed a strong and significant genetic structure, not correlated with the geographic distance, i.e. a lack of isolation by distance (IBD). The pairs of sites with the lowest F-ST were those connected by the current patterns. The time needed for a zygote or a raft to travel from one location to another ranged from 4 to 18 h (i.e. within the survival time of a zygote) and for distances of up to 23 km. Despite the very low dispersal capability of the zygotes, long-distance dispersal is therefore possible. Several non-exclusive processes can account for the genetic structure of C. amentacea populations, such as step-by-step local dispersal, long-distance dispersal of zygotes and rafts by currents, during storms, and the "priority effect", i. e. the importance of the timing of arrival of the propagules.

This volume contains the main results of the EC FP7 “The Ocean of Tomorrow” Project CoCoNet, divided in two sections: 1) a set of guidelines to design networks of Marine Protected Areas in the Mediterranean and the Black Seas; 2) a smart wind chart that will allow evaluating the possibility of installing Offshore Wind Farms in both seas. The concept of Cells of Ecosystem Functioning, based on connectivity, is introduced to define natural units of management and conservation. The definition of Good Environmental Status, as defined in the Marine Strategy Framework Directive, is fully embraced to set the objectives of the project, by adopting a holistic approach that integrates a full set of disciplines, ranging from physics to bio-ecology, economics, engineering and many sub-disciplines. The CoCoNet Consortium involved scientist sfrom 22 states, based in Africa, Asia, and Europe, contributing to build a coherent scientific community.

Cystoseira amentacea is a Mediterranean endemic alga thriving on very shallow rocky substrates. It has been considered as a threatened species, having experienced a steady decline and is therefore protected by international conventions. The historical distribution of the species has been assessed along the French Mediterranean coast, on the basis of 467 articles and herbarium vouchers. We have produced an accurate map of its current distribution and abundance along 1832 km of coastline, through in situ surveys. C. amentacea was observed along 1125 km of shoreline, including 33% of almost continuous or continuous belt. In most of its range, there is no evidence of loss, except in 4 areas of Provence, French Riviera and Corsica. A significant relation was found between the absence or low abundance of C. amentacea and the vicinity of ports and large sewage outfalls. The status of conservation of the species should therefore be reassessed.

Cystoseira amentacea var. stricta (Sargassaceae) is an endemic alga of the Mediterranean Sea. It grows in the upper sublittoral wave-exposed zone and is submitted to various anthropogenic pressures resulting in population fragmentation. In order to assess the genetic diversity and structure of these populations, we developed eight microsatellite markers and validated them on 57 individuals from two populations. With 4–9 alleles per locus, the observed heterozygosity varied between 0.033 and 0.852. We tested cross-amplification of the eight primers on Cystoseira mediterranea, and it was successful for seven of these primers.

Genomic libraries of Arenaria grandiflora enriched for di- and trinucleotide repeats were used for the development of novel microsatellite markers. The subset of 13 polymorphic markers was characterized on 40 individuals of A. grandiflora originating from lowland locations in France. The loci amplified 3 to 10 alleles per locus and expected heterozygosities ranged from 0.46 to 0.83. The newly developed markers will be used for population genetic studies and for assessing genetic composition of a restoration experiment of lowland A. grandiflora populations that are protected in France.

We have tried to elucidate the origin of phytochemical variation in trees by studying concomitantly the chemical and microsatellite variations in Santalum austrocaledonicum. Eight natural populations were sampled in the New-Caledonian archipelago, a total of 157 individuals being analyzed. The main components, as revealed by gas chromatography (GC), were alpha- and beta-santalol (as in other sandalwood species), although the level of (Z)-lanceol was particularly high. Most of the chemical variation was observed within populations (83.7%). With microsatellites, the variation between populations was more pronounced (32% of the total variation). Although the chemical variation between populations was small, we investigated the effects of genetic drift and migration by comparing the chemical- and molecular-differentiation patterns. The poor congruence between neighbor-joining trees, confirmed by the non-significant Mantel test between the molecular and chemical distance matrices (R = 0.26, P = 0.12). showed that genetic drift and migration are not the main evolutionary forces acting on chemical differentiation between populations. We could not find any effect of soil and rainfall conditions neither.Although the impact of drift and migration cannot be discounted in rationalizing between-population differentiation, the low variation among populations could result from a stabilizing selection caused by the same phytopathogen charge across the natural range.

Abstract The successful restoration of plant species in the wild depends on knowledge of the species' habitat requirements and genetic, demographic, and ecological traits that may increase vulnerability to stochastic extinction processes. A few studies have reported experimental projects that attempted to re-establish populations of endangered plants; however, their experimental designs often led to ambiguous results. This paper reviews the common practices in plant restoration and re-establishment programs and reports on an experiment that we performed on an endangered plant Arenaria grandiflora) in the Parisian region. Our aim is to provide advice on how a restoration experiment should be conducted in order to maximize its success.

Various approaches have been developed to define conservation units for plant and animal species. In this study we combined nuclear microsatellites (from a previous published study) and chloroplast microsatellites (assessed in the present study), leaf and seed morphology traits and abiotic variables (climate and soil) to define evolutionary significant units (ESU) of Santalum austrocaledonicum, a tree species growing in New Caledonia. Results for chloroplast microsatellites showed that the total population heterozygosity was␣high, (H cp = 0.84) but varied between islands. Differentiation was strong in the total population (F stcp = 0.66) but also within the main island Grande Terre (F stcp = 0.73) and within Iles Loyauté (F stcp = 0.52), highlighting a limited gene flow between populations. These results confirmed those obtained with nuclear microsatellites. The cluster analysis on molecular markers discriminated two main groups constituted by the populations of Grande Terre and the populations of Iles Loyauté. A principal component analysis of leaf and seed morphology traits singled out the populations of Iles Loyauté and the western populations of Grande Terre. Quantitative genetic analyses showed that the variation between populations was under genetic control (broad sense heritability close to 80%). A high correlation between rainfall and morphological traits suggested an impact of climate on this variation. The integration of these results allows to define two ESUs, one corresponding to Grande Terre and Ile des Pins and the other the Iles Loyauté archipelago. This study stresses the need to restore some populations of Grande Terre that are currently threatened by their small size.