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The porpoise family (Phocoenidae) has seven species that inhabit mostly temperate waters and display a textbook example of anti-tropical distribution. Their evolutionary history remained poorly known, and some species face major conservation issues (e.g., critically endangered vaquita and Yangzte finless porpoises). Here, we used a comparative genomic approach to reconstruct the evolutionary history of porpoises across the entire speciation continuum, from the intraspecific level to species divergence in relation to past climatic changes. We assembled the mitochondrial genomes and resequenced at low coverage the entire nuclear genome of 63 porpoises. Phylogenetic reconstructions suggest that, like other toothed whales, porpoises radiated during the late Miocene-Pliocene but their current intraspecific subdivisions were shaped by environmental variations during the Quaternary Glaciations. We highlighted a parallel evolution in both hemispheres associated with symmetric adaptations to different environments (coastal versus pelagic) exhibiting convergent patterns of coloration and genetic diversity. This result suggests that the mechanism driving diversification of the well-known species of the Northern Hemisphere may apply also to the poorly-known southern species. In contrast to previous results, our results showed that spectacled and Burmeister’s porpoises share a more recent common ancestor than with the vaquita. The vaquita diverged from southern species during the Pliocene but has low diversity, possibly due to long-term small population size, population bottleneck(s), or small founding population in the Gulf of California. We also observed divergent lineages within Dall’s, spectacled and North Pacific harbor porpoises, suggesting a richer evolutionary history than previously thought. Genetic inferences of demographic trends from mitochondrial and nuclear genomes for each species and sub-species shed light on the dynamics of population size fluctuations and subdivisions. These results provide a new perspective on the divergence, adaptation and speciation processes of the porpoises. We will discuss how this knowledge can provide an evolutionary context for their conservation.

Potential range and seasonal movements of whale species. Table with mean (±SD) δ15N and δ13C values of potential prey. Estimates of the mean and standard deviation (SD) δ15N and δ13C values of regions used in Bayesian stable isotope mixing models run for blue, fin and sei whales. Summary of results of one-way ANOVAs and Student's t-test assessing differences in δ15N and δ13C values among whale species (blue, fin and sei whales) and among sexes, seasons and years for fin and sei whales. Plot of Mean and standard deviation (SD) δ15N and δ13C values of potential prey items from different regions and seasons. Percentage mean and SD contribution of different regional sources to the diet of blue, fin and sei whales estimated using Bayesian isotopic mixing models.

We investigate stratification patterns and topographical variations in the blubber of the striped dolphin (Stenella coeruleoalba) to gain insights into its regionally-specific functions. We collected blubber from 10 stranded striped dolphins (5 females and 5 males) from the eastern coast of Spain in 2007-2009, at 11 body positions. Histological measurements (adipocyte number and area) and blubber lipid content were analysed for each position. Histological measurements revealed stratification of blubber into outer, middle, and inner layers. Both the adipocyte number and area were largest in the middle layer. The adipocyte number was higher in the outer than the inner layer, whereas the adipocyte area was higher in the inner than the outer layer. The ventral anterior position did not follow this pattern, likely due to its proximity to the acoustic blubber, which is known to have a different biochemical composition. The stratification in morphological blubber characteristics most likely reflects functional differences. The outer layer may provide structural support and act as a mechanical barrier with a minor role in energy storage. The middle layer may be responsible for thermoregulation, and the inner layer could be responsible for energy mobilization, which is favoured by its proximity to the body core and a higher vascularization. In addition, an increasing gradient from dorsal to ventral positions was observed in the mean number of adipocytes and lipid content, with the exception of the caudal region. Although both ventral and dorsal blubber can have insulator and buoyancy functions, the ventral blubber may mainly serve as an energy reserve., En el presente estudio se investigaron los patrones de estratificación así como las variaciones topográficas en la grasa del delfín listado (Stenella coeruleoalba) con el fin de conocer mejor las posibles funciones regionales de este tejido. Se recolectaron muestras de grasa en 11 posiciones corporales diferentes de 10 delfines listados (5 hembras y 5 machos) varados en la costa este de España entre los años 2007 y 2009. Las medidas histológicas (número de adipocitos y área de los mismos) y el contenido lipídico se analizaron en cada una de las posiciones. Las medidas histológicas mostraron que la grasa se estratificaba en 3 capas: externa, media e interna. Tanto el número de adipocitos como su área eran mayores en la capa media. El número de adipocitos era superior en la capa externa que en la interna, mientras que el área de los adipocitos era mayor en la capa interna que en la externa. Sin embargo, la región ventral anterior no seguía este patrón, probablemente esto sea debido a que esta región se encuentra muy próxima a la grasa acústica, que es conocida por presentar una composición bioquímica diferente al resto de grasa corporal. La estratificación morfológica observada en la grasa probablemente esté reflejando una diferenciación funcional. La capa más externa podría dar soporte estructural y actuar como barrera mecánica, con un papel menos importante como almacén de reservas energéticas. La capa media podría ser responsable de la termorregulación, mientras que en la capa interna se produciría la movilización energética, lo cual se vería favorecido por su elevada vascularización y por estar en contacto con el interior del cuerpo. Además, se observó que tanto el número de adipocitos como el contenido lipídico seguían un gradiente creciente desde las posiciones dorsales a las ventrales, a excepción de la región caudal. Aunque tanto la grasa de la región dorsal como la de la ventral pueden presentar funciones de flotabilidad y aislamiento térmico, la grasa de la región ventral podría estar actuando principalmente como región de reserva energética.

From the early 17th century to the 1970s southern right whales, Eubalaena australis, were subject to intense exploitation along the Atlantic coast of South America. Catches along this coast recorded by whalers originally formed a continuum from Brazil to Tierra del Fuego. Nevertheless, the recovery of the population has apparently occurred fragmentarily, and with two main areas of concentration, one off southern Brazil (Santa Catarina) and another off central Argentina (Peninsula Valdés). This pattern suggests some level of heterogeneity amongst the population, which is apparently contradicted by records that traced individuals moving throughout the whole geographical extension covered by the species in the Southwest Atlantic. To test the hypothesis of the potential occurrence of discrete subpopulations exploiting specific habitats, we investigated N, C and O isotopic values in 125 bone samples obtained from whaling factories operating in the early 1970s in southern Brazil (n = 72) and from contemporary and more recent strandings occurring in central Argentina (n = 53). Results indicated significant differences between the two sampling areas, being δ13C and δ18O values significantly higher in samples from southern Brazil than in those from central Argentina. This variation was consistent with isotopic baselines from the two areas, indicating the occurrence of some level of structure in the Southwest Atlantic right whale population and equally that whales more likely feed in areas commonly thought to exclusively serve as nursing grounds. Results aim at reconsidering of the units currently used in the management of the southern right whale in the Southwest Atlantic Ocean. In the context of the current die-off affecting the species in Peninsula Valdés, these results also highlight the necessity to better understand movements of individuals and precisely identify their feeding areas. Fil: Morgana, Vighi. Universidad de Barcelona; España Fil: Borrell, Asunción. Universidad de Barcelona; España Fil: Crespo, Enrique Alberto. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Centro Nacional Patagónico; Argentina Fil: Oliveira, Larissa R.. Universidade Vale do Rio dos Sinos; Brasil. Universidade Federal do Rio Grande do Sul; Brasil Fil: Simões Lopes, Paulo C.. Universidade Federal Santa Catarina; Brasil Fil: Flores, Paulo A. C.. Centro Nacional de Pesquisa e Conservaçào de Mamíferos Aquáticos; Brasil Fil: Garcia, Nestor Anibal. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Centro Nacional Patagónico; Argentina Fil: Aguilar, Alejandro. Universidad de Barcelona; España

RATIONALE The relationship between stocks of fin whales inhabiting the temperate eastern North Atlantic and the Mediterranean Sea is subject to controversy. The use of chemical markers facilitates an alternative insight into population structure and potential borders between stocks because the two areas present dissimilar isotopic baselines. METHODS Baleen plates, composed of inert tissue that keeps a permanent chronological record of the isotopic value of body circulating fluids, were used to investigate connectivity and boundaries between the stocks. Values were determined by continuous flow isotope ratio mass spectrometry. RESULTS Stable isotopes confirm that, while the two subpopulations generally forage in well-differentiated grounds, some individuals with characteristic Atlantic values do penetrate into the Mediterranean Sea up to the northernmost latitudes of the region. As a consequence, the border between the two putative subpopulations may be not as definite as previous acoustic investigations suggested. The discriminant function obtained in this study may assist researchers to use baleen plate isotopic data to assign the origin of fin whales of uncertain provenance. CONCLUSIONS This study strengthens the stock subdivision currently accepted for management and conservation while recognizes a low level of exchange between the Mediterranean and temperate eastern North Atlantic subdivisions. Copyright © 2013 John Wiley & Sons, Ltd.

In pelagic species inhabiting large oceans, genetic differentiation tends to be mild and populations devoid of structure. However, large cetaceans have provided many examples of structuring. Here we investigate whether the sperm whale, a pelagic species with large population sizes and reputedly highly mobile, shows indication of structuring in the eastern North Atlantic, an ocean basin in which a single population is believed to occur. To do so, we examined stable isotope values in sequential growth layer groups of teeth from individuals sampled in Denmark and NW Spain. In each layer we measured oxygen-isotope ratios (delta O-18) in the inorganic component (hydroxyapatite), and nitrogen and carbon isotope ratios (delta N-15: delta C-13) in the organic component (primarily collagenous). We found significant differences between Denmark and NW Spain in delta N-15 and delta O-18 values in the layer deposited at age 3, considered to be the one best representing the baseline of the breeding ground, in delta N-15, delta C-13 and delta O-18 values in the period up to age 20, and in the ontogenetic variation of delta N-15 and delta O-18 values. These differences evidence that diet composition, use of habitat and/or migratory destinations are dissimilar between whales from the two regions and suggest that the North Atlantic population of sperm whales is more structured than traditionally accepted.