Search

Different mating systems are expected to affect the extent and direction of hybridization. Due to the different levels of sexual conflict, the weak inbreeder/strong outbreeder (WISO) hypothesis predicts that gametes from self-incompatible (SI) species should outcompete gametes from self-compatible (SC) ones. However, other factors such as timing of selfing and unilateral incompatibilities may also play a role on the direction of hybridization. In addition, differential mating opportunities provided by different mating systems are also expected to affect the direction of introgression in hybrid zones involving outcrossers and selfers. Here, we explored these hypotheses with a unique case of recent hybridization between two mangrove killifish species with different mating systems, Kryptolebias ocellatus (obligately outcrossing) and K. hermaphroditus (predominantly self-fertilizing) in two hybrid zones in southeast Brazil. Hybridization rates were relatively high (~20%), representing the first example of natural hybridization between species with different mating systems in vertebrates. All F1 individuals were sired by the selfing species. Backcrossing was small, but mostly asymmetrical with the SI parental species, suggesting pattern commonly observed in plant hybrid zones with different mating systems. Our findings shed light on how contrasting mating systems may affect the direction and extent of gene flow between sympatric species, ultimately affecting the evolution and maintenance of hybrid zones.

Climatic changes are disrupting distribution patterns of populations through shifts in species abiotic niches and habitat loss. The abiotic niche of marine benthic taxa such as skates, however, may be more climatically stable compared with the upper layers of the water column, which are more exposed to immediate impacts of warming. Here, we estimate climate change impacts in Riorajini, a tribe of four skates, as a proxy to evaluate the vulnerability of a temperate coastal zone in the Southwest Atlantic, and study niche dynamics in a scenario of environmental changes on this group of threatened species. We modelled the abiotic niche of each species under present climatic conditions (2000-2014), projected them to the future (2100), then measured distributional stability, expansion, and unfilling. Our results revealed abiotic stability between the scenarios modelled despite the advancement of climate change, suggesting that the benthic layers where these skates occur may be a refuge from the increasing thermal stress. However, the exposure of shallow waters to climate change may be detrimental to nursery habitats. Thus, although their abiotic niche may remain stable in the future, the loss of extension of occurrence might be a peril for them with climate change. Key words: global warming, skates, Riorajini, RCP 8.5, elasmobranchs, marine ecosystem. Les changements climatiques perturbent les motifs demographiques de differentes especes en modifiant leurs niches abiotiques et en detruisant leurs habitats. La stabilite climatique des niches abiotiques de taxons marins benthiques comme les raies pourrait etre plus grande que celle de taxons des couches superieures de la colonne d'eau, plus exposees aux impacts immediats du rechauffement. Nous estimons les impacts des changements climatiques sur les Riorajini, une tribu de quatre raies, comme temoins de la vulnerabilite d'une zone cotiere temperee du sud-ouest de l'ocean Atlantique et etudions la dynamique des niches dans un scenario de changements des conditions ambiantes pour ce groupe d'especes menacees. Nous modelisons la niche abiotique de chacune des especes dans les conditions climatiques actuelles (2000-2014), en etablissons des projections futures (2100), puis mesurons la stabilite et l'expansion de leur repartition, ainsi que la disparition de conditions propices. Nous resultats revelent une stabilite abiotique entre les scenarios modelises, malgre la poursuite des changements climatiques, ce qui indiquerait que les couches benthiques ou se trouvent les raies pourraient constituer un refuge contre le stress thermique croissant. Toutefois, l'exposition des eaux peu profondes aux changements climatiques pourrait etre nefaste pour les habitats de croissance des juveniles. Ainsi, si leur niche abiotique pourrait demeurer stable a l'avenir, les raies pourraient etre menacees par la diminution de l'aire ou elles sont presentes decoulant des changements climatiques. [Traduit par la Redaction] Mots-cles : rechauffement planetaire, raies, Riorajini, RCP 8.5, elasmobranches, ecosysteme marin., Introduction Long-term analyses show that global warming resulting from the continuous increase in emission of greenhouse gases is likely an effect of anthropogenic activities (Houghton 1996; Mann et al. 1999; [...]

We use extensive geographical sampling and surveys of nuclear microsatellite and mitochondrial DNA loci to investigate the phylogeographic structure of the only recognized self-fertilizing vertebrates, the mangrove killifishes, currently thought to comprise two cryptic species, Kryptolebias marmoratus and Kryptolebias hermaphroditus. All genetic markers revealed three concordant main clades. The Northern clade includes populations from Florida, northern Cuba, Bahamas, Belize and Honduras and corresponds to K. marmoratus. The Southern clade encompasses populations from Brazil and corresponds to K. hermaphroditus. This species was considered endemic to southeastern Brazil, but molecular data corroborate its occurrence in northeastern Brazil. The Central clade, not previously resolved with genetic data, includes populations from Panama and Antilles. Despite the geographic proximity of the Northern and Central clades, the latter is genetically closer to the Southern clade. The discovery of the Central clade raises some taxonomic issues - it can either be considered a distinct species or united with the Southern clade into a single species with two subspecies. Another possible taxonomic solution is a single selfing species, K. marmoratus, with three subspecies. We show that the Central and Southern clades are highly selfing (97-100%), whereas selfing rates of the Northern clade populations vary geographically (39-99%). Genetic patterns indicate that populations in SE Brazil are recent, contrary to expectations based on the known distributions of related species.

Paleo-drainage connections and headwater stream-captures are two main historical processes shaping the distribution of strictly freshwater fishes. Recently, bathymetric-based methods of paleo-drainage reconstruction have opened new possibilities to investigate how these processes have shaped the genetic structure of freshwater organisms. In this context, the present study used paleo-drainage reconstructions and single-locus cluster delimitation analyses to examine genetic structure on the whole distribution of Pareiorhaphis garbei, a 'near threatened' armored catfish from the Fluminense freshwater ecoregion in Southeastern Brazil. Sequences of two mitochondrial genes (cytochrome b and cytochrome c oxidase subunit 1) were obtained from five sampling sites in four coastal drainages: Macaé (KAE), São João (SJO), Guapi-Macacu [sub-basins Guapiaçu (GAC) and Guapimirim (GMI)], and Santo Aleixo (SAL). Pronounced genetic structure was found, involving 10 haplotypes for cytB and 6 for coi, with no haplotypes shared between localities. Coalescent-based delineation methods as well as distance-based methods revealed genetic clusters corresponding to each sample site. Paleo-drainage reconstructions showed two putative paleo-rivers: an eastern one connecting KAE and SJO; and a western one merging in the Guanabara Bay (GAC, GMI, and SAL). A disagreement was uncovered between the inferred past riverine connections and current population genetic structure. Although KAE and SJO belong to the same paleo-river, the latter is more closely related to specimens from the Guanabara paleo-river. This discordance between paleo-drainage connections and phylogenetic structure may indicate an ancient stream-capture event in headwaters of this region. Furthermore, all analyses showed high divergence between KAE and the other lineages, suggesting at least one cryptic species in the latter, and that the nominal species should be restricted to the Macaé river basin, its type locality. In this drainage, impacts such as the invasive species and habitat loss can be especially threatening for such species with a narrow range. Our results also suggest that freshwater fishes from headwaters in the Serra do Mar mountains might have different biogeographical patterns than those from the lowlands, indicating a complex and dynamic climatic and geomorphological history.

As the world aims to address the UN Sustainable Development Goals (SDGs), it is becoming more urgent for heavy transportation sectors, such as shipping and aviation, to decarbonise in an economically feasible way. This review paper investigates the potential fuels of the future and their capability to mitigate the carbon footprint when other technologies fail to do so. This review looks at the technologies available today, including, primarily, transesterification, hydrocracking, and selective deoxygenation. It also investigates the potential of fish waste from the salmon industry as a fuel blend stock. From this, various kinetic models are investigated to find a suitable base for simulating the production and economics of biodiesel (i.e., fatty acid alkyl esters) and renewable diesel production from fish waste. Whilst most waste-oil-derived biofuels are traditionally produced using transesterification, hydrotreating looks to be a promising method to produce drop-in biofuels, which can be blended with conventional petroleum fuels without any volume percentage limitation. Using hydrotreatment, it is possible to produce renewable diesel in a few steps, and the final liquid product mixture includes paraffins, i.e., linear, branched, and cyclo-alkanes, with fuel properties in compliance with international fuel standards. There is a wide range of theoretical models based on the hydrodeoxygenation of fatty acids as well as a clear economic analysis that a model could be based on. [ABSTRACT FROM AUTHOR]

Hypostomus is the most species-rich genus within the family Loricariidae and is widely distributed throughout the Neotropical region. Nonetheless, the diversity and distribution of these species have still large knowledge gaps. This scenario is more significant in some regions, such as the northeast of Brazil. In this region, the first species of the genus, H. pusarum , was described in the Northeast Caatinga and Costal Drainages ecoregion. Six congeners were subsequently described in the same ecoregion, all sharing the same colour pattern making them difficult to distinguish. All of them are collectively referred to as the H. pusarum complex. The present work seeks to clarify the diversity that constitutes the H. pusarum complex through an integrative study using molecular and morphological data. The results indicate that H. carvalhoi , H. jaguribensis , H. nudiventris , H. papariae , and H. salgadae are all junior synonyms of H. pusarum. However, one of the morphotypes that occurs in the Parnaíba River is a new species that differs from the others by the absence of a developed medial buccal papilla and the presence of a pre-anal plate. The data provided here highlight the importance of integrative taxonomy for assessing diversity in complex and diverse groups in the Neotropics. [ABSTRACT FROM AUTHOR]