Contrasting patterns of selection between MHC I and II across populations of Humboldt and Magellanic penguins

Indexación: Web of ScienceThe evolutionary and adaptive potential of populations or species facing an emerging infectious disease depends on their genetic diversity in genes, such as the major histocompatibility complex (MHC). In birds, MHC class I deals predominantly with intracellular infections (e.g., viruses) and MHC class II with extracellular infections (e.g., bacteria). Therefore, patterns of MHC I and II diversity may differ between species and across populations of species depending on the relative effect of local and global environmental selective pressures, genetic drift, and gene flow. We hypothesize that high gene flow among populations of Humboldt and Magellanic penguins limits local adaptation in MHC I and MHC II, and signatures of selection differ between markers, locations, and species. We evaluated the MHC I and II diversity using 454 next-generation sequencing of 100 Humboldt and 75 Magellanic penguins from seven different breeding colonies. Higher genetic diversity was observed in MHC I than MHC II for both species, explained by more than one MHC I loci identified. Large population sizes, high gene flow, and/or similar selection pressures maintain diversity but limit local adaptation in MHC I. A pattern of isolation by distance was observed for MHC II for Humboldt penguin suggesting local adaptation, mainly on the northernmost studied locality. Furthermore, trans species alleles were found due to a recent speciation for the genus or convergent evolution. High MHC I and MHC II gene diversity described is extremely advantageous for the long term survival of the species.http://onlinelibrary.wiley.com/doi/10.1002/ece3.2502/epd

New crania from Seymour Island (Antarctica) shed light on anatomy of Eocene penguins

Antarctic skulls attributable to fossil penguins are rare. Three new penguin crania from Antarctica are here described providing an insight into their feeding function. One of the specimens studied is largely a natural endocast, slightly damaged, and lacking preserved osteological details. Two other specimens are the best preserved fossil penguin crania from Antarctica, enabling the study of characters not observed so far. All of them come from the uppermost Submeseta Allomember of the La Meseta Formation (Eocene–?Oligocene), Seymour (Marambio) Island, Antarctic Peninsula. The results of the comparative studies suggest that Paleogene penguins were long−skulled birds, with strong nuchal crests and deep temporal fossae. The configuration of the nuchal crests, the temporal fossae, and the parasphenoidal processes, appears to indicate the presence of powerful muscles. The nasal gland sulcus devoid of a supraorbital edge is typical of piscivorous species.Fil: Acosta Hospitaleche, Carolina Ileana Alicia. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de la Plata. Facultad de Ciencias Naturales y Museo. División Paleontología Vertebrados; Argentin

Bayesian total evidence dating reveals the recent crown radiation of penguins

The total-evidence approach to divergence-time dating uses molecular and morphological data from extant and fossil species to infer phylogenetic relationships, species divergence times, and macroevolutionary parameters in a single coherent framework. Current model-based implementations of this approach lack an appropriate model for the tree describing the diversification and fossilization process and can produce estimates that lead to erroneous conclusions. We address this shortcoming by providing a total-evidence method implemented in a Bayesian framework. This approach uses a mechanistic tree prior to describe the underlying diversification process that generated the tree of extant and fossil taxa. Previous attempts to apply the total-evidence approach have used tree priors that do not account for the possibility that fossil samples may be direct ancestors of other samples. The fossilized birth-death (FBD) process explicitly models the diversification, fossilization, and sampling processes and naturally allows for sampled ancestors. This model was recently applied to estimate divergence times based on molecular data and fossil occurrence dates. We incorporate the FBD model and a model of morphological trait evolution into a Bayesian total-evidence approach to dating species phylogenies. We apply this method to extant and fossil penguins and show that the modern penguins radiated much more recently than has been previously estimated, with the basal divergence in the crown clade occurring at ~12.7 Ma and most splits leading to extant species occurring in the last 2 million years. Our results demonstrate that including stem-fossil diversity can greatly improve the estimates of the divergence times of crown taxa. The method is available in BEAST2 (v. 2.4) www.beast2.org with packages SA (v. at least 1.1.4) and morph-models (v. at least 1.0.4).Comment: 50 pages, 6 figure

Bayesian phylogenetic estimation of fossil ages

Recent advances have allowed for both morphological fossil evidence and molecular sequences to be integrated into a single combined inference of divergence dates under the rule of Bayesian probability. In particular the fossilized birth-death tree prior and the Lewis-Mk model of discrete morphological evolution allow for the estimation of both divergence times and phylogenetic relationships between fossil and extant taxa. We exploit this statistical framework to investigate the internal consistency of these models by producing phylogenetic estimates of the age of each fossil in turn, within two rich and well-characterized data sets of fossil and extant species (penguins and canids). We find that the estimation accuracy of fossil ages is generally high with credible intervals seldom excluding the true age and median relative error in the two data sets of 5.7% and 13.2% respectively. The median relative standard error (RSD) was 9.2% and 7.2% respectively, suggesting good precision, although with some outliers. In fact in the two data sets we analyze the phylogenetic estimates of fossil age is on average < 2 My from the midpoint age of the geological strata from which it was excavated. The high level of internal consistency found in our analyses suggests that the Bayesian statistical model employed is an adequate fit for both the geological and morphological data, and provides evidence from real data that the framework used can accurately model the evolution of discrete morphological traits coded from fossil and extant taxa. We anticipate that this approach will have diverse applications beyond divergence time dating, including dating fossils that are temporally unconstrained, testing of the "morphological clock", and for uncovering potential model misspecification and/or data errors when controversial phylogenetic hypotheses are obtained based on combined divergence dating analyses.Comment: 28 pages, 8 figure

Krill-feeding behaviour in a chinstrap penguin compared to fish-eating in Magellanic penguins: a pilot study.

Inferring feeding activities from undulations in diving depth profiles is widespread in studies of foraging marine predators. This idea, however, has rarely been tested because of practical difficulties in obtaining an independent estimate of feeding activities at a time scale corresponding to depth changes within a dive. In this study we attempted to relate depth profile undulations and feeding activities during diving in a single Chinstrap Penguin Pygoscelis antarctica, by simultaneously using a conventional time-depth recorder and a recently developed beak-angle sensor. Although failure in device attachments meant that data were obtained successfully from just a part of a single foraging trip, our preliminary results show a linear relationship between the number of depth wiggles and the number of underwater beakopening events during a dive, suggesting that the relative feeding intensity of each dive could be represented by depth-profile data. Underwater beak-opening patterns of this krill-feeding penguin species are compared with recent data from three fish- and squid-feeding Magellanic Penguins Spheniscus magellanicus

Contemporary outbreaks of different avipoxviruses in Humboldt penguins of wild animal park Planckendael and in chickens of commercial poultry farms in Belgium

In the present study, the first outbreak of a penguinpox virus (PPV) in Humboldt penguins (Spheniscus humboldd) and four outbreaks of fowlpox virus (FPV) in layer chickens are reported. Clinically, cutaneous wart-like growths were observed around the eyes in four juvenile Humboldt penguins and cutaneous nodular lesions in the comb, wattles, around the eyes and other unfeathered skin parts of layer chickens. Histopathology (FPV and PPV), electron microscopy (PPV), virus isolation (FPV) and PCR amplification (FPV and PPV) confirmed that both isolates were avipoxviruses (APVs). According to the phylogenetic analysis of the partial P4b core protein gene, the Belgian Humboldt PPV clustered with sequences of free-range (domestic and synanthrope bird species) and wild bird species of the United States and Europe (99-100% homology), and all four Belgian FPV isolates clustered with FPV isolates of chickens, turkeys, canary and FPV attenuated live vaccines from all over the world (100% homology)

Sexual and geographic dimorphism in northern rockhopper penguins breeding in the South Atlantic Ocean

The Endangered northern rockhopper penguin Eudyptes moseleyi, like all penguins, is monomorphic, making sex determination of individuals in the field challenging. We examined the degree of sexual size dimorphism of adult birds across the species’ breeding range in the Atlantic Ocean and developed discriminant functions (DF) to predict individuals’ sex using morphometric measurements. We found significant site-specific differences in both bill length and bill depth, with males being the larger sex on each island. Across all islands, bill length contributed 78% to dissimilarity between sexes. Penguins on Gough Island had significantly longer bills, whilst those from Tristan da Cunha had the deepest. Island-specific DFs correctly classified 82-94% of individuals, and all functions performed significantly better than chance. The model for Nightingale Island correctly classified the greatest proportion of individuals (94-95%), while that for Tristan da Cunha performed the poorest (80-82%). A discriminant function derived from all sites accurately sexed 86-88% of northern rockhopper penguins achieving similar accuracy to island-specific functions. While molecular techniques conclusively determine an individual’s sex, morphometric measurements can provide a reliable estimate with close to 90% accuracy using a method that is less invasive and requires little technical expertise. Sexing is an important tool for meaningful interpretation of ecological data. Consideration of sex-specific differences in future studies will aid investigation of a potential sex-dependent vulnerability in this Endangered species.© The authors 2019. Open Access under Creative Commons by Attribution Licence. Use, distribution and reproduction are unrestricted. Authors and original publication must be credited. The attached file is the published pdf

Foraging movements of emperor penguins at Pointe Géologie, Antarctica.

International audienceThe foraging distributions of 20 breeding emperor penguins were investigated at Pointe Ge´ologie, Terre Ade´lie, Antarctica by using satellite telemetry in 2005 and 2006 during early and late winter, as well as during late spring and summer, corresponding to incubation, early chick-brooding, late chick-rearing and the adult pre-moult period, respectively. Dive depth records of three post-egg-laying females, two post-incubating males and four late chick-rearing adults were examined, as well as the horizontal space use by these birds. Foraging ranges of chick-provisioning penguins extended over the Antarctic shelf and were constricted by winter pack-ice. During spring ice break-up, the foraging ranges rarely exceeded the shelf slope, although seawater access was apparently almost unlimited. Winter females appeared constrained in their access to open water but used fissures in the sea ice and expanded their prey search effort by expanding the horizontal search component underwater. Birds in spring however, showed higher area-restricted-search than did birds in winter. Despite different seasonal foraging strategies, chick-rearing penguins exploited similar areas as indicated by both a high ‘Area-Restricted-Search Index' and high ‘Catch Per Unit Effort'. During pre-moult trips, emperor penguins ranged much farther offshore than breeding birds, which argues for particularly profitable oceanic feeding areas which can be exploited when the time constraints imposed by having to return to a central place to provision the chick no longer apply