Browsing by Author "Maggs, Christine A."
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- Evaluating signatures of glacial refugia for North Atlantic benthic marine taxaPublication . Maggs, Christine A.; Castilho, Rita; Foltz, David; Henzler, Christy; Jolly, Marc Taimour; Kelly, John; Olsen, Jeanine; Perez, Kathryn E.; Stam, Wytze; Vainola, Risto; Viard, Frederique; Wares, JohnA goal of phylogeography is to relate patterns of genetic differentiation to potential historical geographic isolating events. Quaternary glaciations, particularly the one culminating in the Last Glacial Maximum similar to 21 ka (thousands of years ago), greatly affected the distributions and population sizes of temperate marine species as their ranges retreated southward to escape ice sheets. Traditional genetic models of glacial refugia and routes of recolonization include these predictions: low genetic diversity in formerly glaciated areas, with a small number of alleles/haplotypes dominating disproportionately large areas, and high diversity including "private'' alleles in glacial refugia. In the Northern Hemisphere, low diversity in the north and high diversity in the south are expected. This simple model does not account for the possibility of populations surviving in relatively small northern periglacial refugia. If these periglacial populations experienced extreme bottlenecks, they could have the low genetic diversity expected in recolonized areas with no refugia, but should have more endemic diversity (private alleles) than recently recolonized areas. This review examines evidence of putative glacial refugia for eight benthic marine taxa in the temperate North Atlantic. All data sets were reanalyzed to allow direct comparisons between geographic patterns of genetic diversity and distribution of particular clades and haplotypes including private alleles. We contend that for marine organisms the genetic signatures of northern periglacial and southern refugia can be distinguished from one another. There is evidence for several periglacial refugia in northern latitudes, giving credence to recent climatic reconstructions with less extensive glaciation.
- 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.