Deep segregation in the open ocean: Macaronesia as an evolutionary hotspot for low dispersal marine invertebrates.

Diversification and speciation of terrestrial organisms are anticipated in oceanic islands such as Macaronesia, a group of Atlantic islands that have remained unconnected to continental landmasses. Hitherto, the diversification of marine organisms in oceanic islands, especially those with low vagility, has received little direct empirical analysis using molecular markers. Here, we focus on such a case study, through applying a multilocus molecular approach to investigate the diversity and evolution of a group that lacks a planktonic larval stage, the isopod genus Dynamene, in Macaronesia and Northeast Atlantic. Sequences of two mitochondrial (cytochrome c oxidase subunit I and 16S rRNA) and two nuclear (18S rRNA and 28S rRNA) loci were obtained from specimens of Dynamene edwardsi (Lucas, 1849), Dynamene magnitorata Holdich, 1968 and Dynamene bidentata (Adams, 1800) collected along the Northeast Atlantic and Macaronesia. Although no major phylogeographic structure was detected in D. bidentata and D. magnitorata, from five to nine deeply divergent lineages were evident within D. edwardsi. The divergent lineages displayed genetic distances comparable to those found among established species of peracarids. D. edwardsi exhibits a long, rich and complex phylogeographic history in Macaronesia, where the geodynamics of the islands possibly associated with founder effects and subsequent lack of gene flow among populations confounds patterns based on geographic proximity of targeted populations. Our findings collectively suggest a much larger role of oceanic islands in the diversification of marine invertebrates than previously anticipated. The work provides insights into the origins and dynamics of ongoing geographic segregation and associated deep divergence among sister evolutionary lineages in Macaronesia.

Distribution and species identification in the crustacean isopod genus Dynamene Leach, 1814 along the North East Atlantic-Black Sea axis.

Sphaeromatid isopods, such as Dynamene, are common and abundant members of the invertebrate fauna of littoral and shallow sublittoral substrates. Six species of Dynamene occur in the northern hemisphere. Only two species exist outside this range, in Australia. The distribution of the various species in the NE Atlantic-Black Sea axis has been controversial due to the difficulty in the identification of the different species. This has led to inaccurate records of their distribution, ultimately generating uncertain or faulty assessments on the biodiversity of these habitats. An update and a clarification about the distribution of this genus is therefore in order. In this study, we describe the distribution of Dynamene species in the light of new records from the NE Atlantic Ocean and its associated islands, and the Mediterranean, Black and Red Seas, and from re-examination of museum and several authors' personal collections. Based on these observations, we extend the northern and southern limits of Dynamene bidentata (Adams); the western and southern limits of Dynamene magnitorata Holdich; the northern, eastern and western limits of Dynamene edwardsi (Lucas); and the eastern and western limits of Dynamene bifida Torelli. The range of Dynamene tubicauda Holdich is extended, but is still only known from the eastern Mediterranean. We also clarify the synonymy of Dynamene torelliae Holdich with Dynamene bicolor (Rathke), and the occurrence of Dynamene bicolor in the Black Sea. New distribution maps of the six Dynamene species are presented. Illustrated keys to the adult males and females of the northern hemisphere species are provided.

Multiple drivers of decline in the global status of freshwater crayfish (Decapoda: Astacidea).

Rates of biodiversity loss are higher in freshwater ecosystems than in most terrestrial or marine ecosystems, making freshwater conservation a priority. However, prioritization methods are impeded by insufficient knowledge on the distribution and conservation status of freshwater taxa, particularly invertebrates. We evaluated the extinction risk of the world's 590 freshwater crayfish species using the IUCN Categories and Criteria and found 32% of all species are threatened with extinction. The level of extinction risk differed between families, with proportionally more threatened species in the Parastacidae and Astacidae than in the Cambaridae. Four described species were Extinct and 21% were assessed as Data Deficient. There was geographical variation in the dominant threats affecting the main centres of crayfish diversity. The majority of threatened US and Mexican species face threats associated with urban development, pollution, damming and water management. Conversely, the majority of Australian threatened species are affected by climate change, harvesting, agriculture and invasive species. Only a small proportion of crayfish are found within the boundaries of protected areas, suggesting that alternative means of long-term protection will be required. Our study highlights many of the significant challenges yet to come for freshwater biodiversity unless conservation planning shifts from a reactive to proactive approach.