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- Non-indigenous seaweeds in the Northeast Atlantic Ocean, the Mediterranean Sea and Macaronesia: a critical synthesis of diversity, spatial and temporal patternsPublication . van der Loos, Luna M.; Bafort, Quinten; Bosch, Samuel; Ballesteros, Enric; Bárbara, Ignacio; Berecibar, Estibaliz; Blanfuné, Aurélie; Bogaert, Kenny; Bouckenooghe, Silke; Boudouresque, Charles-François; Brodie, Juliet; Cecere, Ester; Díaz-Tapia, Pilar; Engelen, Aschwin; Gunnarson, Karl; Shabaka, Soha Hamdy; Hoffman, Razy; Husa, Vivian; Israel, Álvaro; Karremans, Mart; Knoop, Jessica; Le Gall, Line; Maggs, Christine A.; Mineur, Frédéric; Parente, Manuela; Perk, Frank; Petrocelli, Antonella; Rodríguez-Prieto, Conxi; Ruitton, Sandrine; Sansón, Marta; A Serrao, Ester; Sfriso, Adriano; Sjøtun, Kjersti; Stiger-Pouvreau, Valérie; Surget, Gwladys; Taşkin, Ergün; Thibaut, Thierry; Tsiamis, Konstantinos; Van De Weghe, Lotte; Verlaque, Marc; Viard, Frédérique; Vranken, Sofie; Leliaert, Frederik; De Clerck, OlivierEffective monitoring of non-indigenous seaweeds and combatting their effects relies on a solid confirmation of the non-indigenous status of the respective species. We critically analysed the status of presumed non-indigenous seaweed species reported from the Mediterranean Sea, the Northeast Atlantic Ocean and Macaronesia, resulting in a list of 140 species whose non-indigenous nature is undisputed. For an additional 87 species it is unclear if they are native or non-indigenous (cryptogenic species) or their identity requires confirmation (data deficient species). We discuss the factors underlying both taxonomic and biogeographic uncertainties and outline recommendations to reduce uncertainty about the non-indigenous status of seaweeds. Our dataset consisted of over 19,000 distribution records, half of which can be attributed to only five species (Sargassum muticum, Bonnemaisonia hamifera, Asparagopsis armata, Caulerpa cylindracea and Colpomenia peregrina), while 56 species (40%) are recorded no more than once or twice. In addition, our analyses revealed considerable variation in the diversity of non-indigenous species between the geographic regions. The Eastern Mediterranean Sea is home to the largest fraction of non-indigenous seaweed species, the majority of which have a Red Sea or Indo-Pacific origin and have entered the Mediterranean Sea mostly via the Suez Canal. Non-indigenous seaweeds with native ranges situated in the Northwest Pacific make up a large fraction of the total in the Western Mediterranean Sea, Lusitania and Northern Europe, followed by non-indigenous species with a presumed Australasian origin. Uncertainty remains, however, regarding the native range of a substantial fraction of non-indigenous seaweeds in the study area. In so far as analyses of first detections can serve as a proxy for the introduction rate of non-indigenous seaweeds, these do not reveal a decrease in the introduction rate, indicating that the current measures and policies are insufficient to battle the introduction and spread of non-indigenous species in the study area.
- Diversity and origin of the genus Lobophora in the Mediterranean Sea including the description of two new speciesPublication . Vieira, Christophe; Aharonov, Andre; Paz, Guy; Engelen, Aschwin; Tsiamis, Konstantinos; Einav, Rachel; De Clerck, OlivierThe brown algal genus Lobophora is widely reported from the Mediterranean Sea. Contrary to studies in the Indo-Pacific and Caribbean regions, little attention has been given to Lobophora in the Mediterranean Sea, at least using molecular tools. To address this knowledge gap, we sampled specimens across the Mediterranean Sea (Spanish coast, Balearic Islands, Greece and Israel), with an exhaustive effort in the Balearic Islands. Molecular analyses disclosed the presence of three species, none of them conspecific with the name L. variegata, as they were recorded up to now in the Mediterranean Sea. The most common species in the Mediterranean Sea is L. delicata. We here describe L. schneideri sp. nov., so far found only in Haifa Bay (Israel), where it forms large and dense populations. Similar to L. delicata, L. schneideri occurs across the North Atlantic Ocean. Though a recent range expansion or introduction cannot be ruled out, we regard the North Atlantic Ocean, including the Greater Caribbean and the Mediterranean Sea, as the natural range of both L. schneideri and L. delicata. A third species, described here as L. lessepsiana sp. nov., is found along the Israeli coast as well as in the Red Sea and is most probably a recent introduction through the Suez Canal. Further exploration along the North African coast, the Levantine Sea and the Aegean Sea, would probably increase the currently known species diversity for this group in the Mediterranean Sea.
- Marine forests of the Mediterranean-Atlantic Cystoseira tamariscifolia complex show a southern Iberian genetic hotspot and no reproductive isolation in parapatryPublication . Bermejo, Ricardo; Chefaoui, Rosa M.; Engelen, Aschwin H.; Buonomo, Roberto; Neiva, J.; Ferreira-Costa, Joana; Pearson, Gareth; Marba, Nuria; Duarte, Carlos M.; Airoldi, Laura; Hernandez, Ignacio; Guiry, Michael D.; Serrao, Ester A.Climate-driven range-shifts create evolutionary opportunities for allopatric divergence and subsequent contact, leading to genetic structuration and hybrid zones. We investigate how these processes influenced the evolution of a complex of three closely related Cystoseira spp., which are a key component of the Mediterranean-Atlantic seaweed forests that are undergoing population declines. The C. tamariscifolia complex, composed of C. tamariscifolia s.s., C. amentacea and C. mediterranea, have indistinct boundaries and natural hybridization is suspected. Our aims are to (1) infer the genetic structure and diversity of these species throughout their distribution ranges using microsatellite markers to identify ancient versus recent geographical populations, contact zones and reproductive barriers, and (2) hindcast past distributions using niche models to investigate the influence of past range shifts on genetic divergence at multiple spatial scales. Results supported a single, morphologically plastic species the genetic structure of which was incongruent with a priori species assignments. The low diversity and low singularity in northern European populations suggest recent colonization after the LGM. The southern Iberian genetic hotspot most likely results from the role of this area as a climatic refugium or a secondary contact zone between differentiated populations or both. We hypothesize that life-history traits (selfing, low dispersal) and prior colonization effects, rather than reproductive barriers, might explain the observed genetic discontinuities.
- A new method to quantify and compare the multiple components of fitness-A study case with kelp niche partition by divergent microstage adaptations to TemperaturePublication . Vieira, Vasco M. N. C. S.; Oppliger, Luz Valeria; Engelen, Aschwin H.; Correa, Juan A.Point 1 Management of crops, commercialized or protected species, plagues or life-cycle evolution are subjects requiring comparisons among different demographic strategies. The simpler methods fail in relating changes in vital rates with changes in population viability whereas more complex methods lack accuracy by neglecting interactions among vital rates. Point 2 The difference between the fitness (evaluated by the population growth rate.) of two alternative demographies is decomposed into the contributions of the differences between the pair-wised vital rates and their interactions. This is achieved through a full Taylor expansion (i.e. remainder = 0) of the demographic model. The significance of each term is determined by permutation tests under the null hypothesis that all demographies come from the same pool. Point 3 An example is given with periodic demographic matrices of the microscopic haploid phase of two kelp cryptic species observed to partition their niche occupation along the Chilean coast. The method provided clear and synthetic results showing conditional differentiation of reproduction is an important driver for their differences in fitness along the latitudinal temperature gradient. But it also demonstrated that interactions among vital rates cannot be neglected as they compose a significant part of the differences between demographies. Point 4 This method allows researchers to access the effects of multiple effective changes in a life-cycle from only two experiments. Evolutionists can determine with confidence the effective causes for changes in fitness whereas population managers can determine best strategies from simpler experimental designs.
- Temperature effects on gametophyte life-history traits and geographic distribution of two cryptic kelp speciesPublication . Valeria Oppliger, L.; Correa, Juan A.; Engelen, Aschwin H.; Tellier, Florence; Vieira, Vasco; Faugeron, Sylvain; Valero, Myriam; Gomez, Gonzalo; Destombe, ChristopheA major determinant of the geographic distribution of a species is expected to be its physiological response to changing abiotic variables over its range. The range of a species often corresponds to the geographic extent of temperature regimes the organism can physiologically tolerate. Many species have very distinct life history stages that may exhibit different responses to environmental factors. In this study we emphasized the critical role of the haploid microscopic stage (gametophyte) of the life cycle to explain the difference of edge distribution of two related kelp species. Lessonia nigrescens was recently identified as two cryptic species occurring in parapatry along the Chilean coast: one located north and the other south of a biogeographic boundary at latitude 29-30 degrees S. Six life history traits from microscopic stages were identified and estimated under five treatments of temperature in eight locations distributed along the Chilean coast in order to (1) estimate the role of temperature in the present distribution of the two cryptic L. nigrescens species, (2) compare marginal populations to central populations of the two cryptic species. In addition, we created a periodic matrix model to estimate the population growth rate (lambda) at the five temperature treatments. Differential tolerance to temperature was demonstrated between the two species, with the gametophytes of the Northern species being more tolerant to higher temperatures than gametophytes from the south. Second, the two species exhibited different life history strategies with a shorter haploid phase in the Northern species contrasted with considerable vegetative growth in the Southern species haploid stage. These results provide strong ecological evidence for the differentiation process of the two cryptic species and show local adaptation of the life cycle at the range limits of the distribution. Ecological and evolutionary implications of these findings are discussed.