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Extreme climate changes during the Cenozoic Era strengthened different biogeographical barriers that decreased the connectivity among populations, triggering lineage diversification of different species worldwide.The mitochondrial DNA control region was employed to explore the phylogeography of Sphyrna zygaena, a globally distributed species threatened by unsustainable, illegal, unreported and unregulated fisheries triggered by the international shark fin trade. It is listed as 'Vulnerable' by the IUCN Red List and its trade is regulated by CITES Appendix II.Only 13 haplotypes were found with low genetic diversity levels (hd = 0.686 ± 0.014; π = 0.00206 ± 0.00004) compared with other species of the Sphyrnidae family. The species has a very strong phylogeographic population structure among the Atlantic, Indian and Pacific Oceans (ΦST = 0.79132). Worldwide, there are six distinct populations with some haplotype sharing.These populations are probably connected by a stepping‐stone dispersal of a small number of migrants per generation from the Indo‐Pacific towards the Atlantic. Modelling suggests that S. zygaena diverged into two lineages around 6.96 million years ago which have been isolated in glacial refuges in the Atlantic and Indo‐Pacific oceans; and after deglaciation, a population expansion probably permitted secondary contact.Conservation plans to establish differentiated management units should be adopted in each of the identified populations. Among these, the Eastern Central Atlantic and West Indo‐Pacific are the most important areas for the species considering the historical migration routes that act as a bridge connecting the Atlantic and Indo‐Pacific Oceans while the Gulf of Guinea connects the Atlantic populations. Still, further studies are required to know if these populations are also linked with nursery areas for the species.The results herein can help to delimit the main evolutionarily significant units to implement effective policies to establish differentiated management units as starting points to genetic monitoring programmes for Sphyrna zygaena. [ABSTRACT FROM AUTHOR]

There is broad consensus that the diversity of functional traits within species assemblages drives several ecological processes. It is also widely recognized that rare species are the first to become extinct following human-induced disturbances. Surprisingly, however, the functional importance of rare species is still poorly understood, particularly in tropical species-rich assemblages where the majority of species are rare, and the rate of species extinction can be high. Here, we investigated the consequences of local and regional extinctions on the functional structure of species assemblages. We used three extensive datasets (stream fish from the Brazilian Amazon, rainforest trees from French Guiana, and birds from the Australian Wet Tropics) and built an integrative measure of species rarity versus commonness, combining local abundance, geographical range, and habitat breadth. Using different scenarios of species loss, we found a disproportionate impact of rare species extinction for the three groups, with significant reductions in levels of functional richness, specialization, and originality of assemblages, which may severely undermine the integrity of ecological processes. The whole breadth of functional abilities within species assemblages, which is disproportionately supported by rare species, is certainly critical in maintaining ecosystems particularly under the ongoing rapid environmental transitions. [ABSTRACT FROM AUTHOR]

Today, elasmobranchs are one the most threatened vertebrate groups worldwide. In fact, at least 90% of elasmobranch species are listed in the International Union for Conservation of Nature (IUCN) Red List, while more than 40% are data-deficient. Although these vertebrates are mainly affected by unsustainable fishery activities, bycatch is also one of the major threats to sharks and batoids worldwide, and represents a challenge for both sustainable fishery management and for biodiversity and conservational efforts. Thus, in this study, DNA barcode methodology was used to identify the bycatch composition of batoid species from small-scale industrial fisheries in the southwest Atlantic and artisanal fisheries from southeast Brazil. A total of 228 individuals belonging to four Chondrichthyes orders, seven families, and at least 17 distinct batoid species were sequenced; among these individuals, 131 belonged to species protected in Brazil, 101 to globally threatened species, and some to species with trade restrictions provided by Appendix II of the Convention on International Trade in Endangered Species (CITES). These results highlight the impacts on marine biodiversity of bycatch by small-scale industrial and unmanaged artisanal fisheries from the southwest Atlantic, and support the implementation of DNA-based methodologies for species-specific identification in data-poor fisheries as a powerful tool for improving the quality of fisheries' catch statistics and for keeping precise bycatch records. [ABSTRACT FROM AUTHOR]

Morphological identification in the field can be extremely difficult considering fragmentation of species for trade or high similarity between congeneric species. In this context, the shark group belonging to the genus Squatina is composed of three species distributed in the southern part of the western Atlantic. These three species are classified in the IUCN Red List as endangered, and they are currently protected under Brazilian law, which prohibits fishing and trade. Molecular genetic tools are now used for practical taxonomic identification, particularly in cases where morphological observation is prevented, e.g., during fish processing. Consequently, DNA barcoding was used in the present study to track potential crimes against the landing and trade of endangered species along the São Paulo coastline, in particular Squatina guggenheim (n = 75) and S. occulta (n = 5), as well as the Brazilian guitarfish Pseudobatos horkelii (n = 5). DNA barcoding revealed the continuous fishing and trafficking of these protected species, thus giving clear evidence that the current conservation models and methods of monitoring are not working. [ABSTRACT FROM AUTHOR]