Single mitochondrial gene barcodes reliably identify sister-species in diverse clades of birds

Background  

DNA barcoding of life using a standardized COI sequence was proposed as a species identification system, and as a method for detecting putative new species. Previous tests in birds showed that individuals can be correctly assigned to species in ~94% of the cases and suggested a threshold of 10× mean intraspecific difference to detect potential new species. However, these tests were criticized because they were based on a single maternally inherited gene rather than multiple nuclear genes, did not compare phylogenetically identified sister species, and thus likely overestimated the efficacy of DNA barcodes in identifying species.     

When Bergmann's rule fails: evidences of environmental selection pressures shaping phenotypic diversification in a widespread seabird

Organisms tend to exhibit phenotypes that can be shaped by climate, commonly demonstrating clinal variations along latitudinal gradients. In vertebrates, air temperature plays a major role in shaping body size in both ectothermic and endothermic animals. However, additional small‐scale environmental factors can also act as selection pressures in the marine ecosystem (e.g. primary productivity), evidencing multi‐scale processes acting on marine organisms. In this study, we tested Bergmann's rule in a widely distributed seabird, the brown booby Sula leucogaster, in addition to evaluating the relationship of sea surface temperature and chlorophyll α with phenotypes. We used traits from a morphometric dataset (culmen, wing chord, and tarsus length) and body mass of 276 brown boobies distributed on six breeding sites along a latitudinal gradient in the South Atlantic Ocean (0–27°S). We found significant differentiation among colonies, but phenotypic similarities were observed between colonies located at the extremes of the latitudinal gradient. As the colony nearest to the Equator, Saint Peter and Saint Paul archipelago, had the largest and heaviest individuals, the model containing only air temperature explained < 5% of the allometric variation, providing no substantial support for Bergmann's rule. However, when we added the interaction of chlorophyll α and sea surface temperature the deviance explained rose to over 80%. Primary productivity and sea surface temperature do not follow a latitudinal gradient in the ocean and, therefore, the role of small‐scale oceanographic processes in shaping body size and the importance of considering additional environmental variables when testing Bergmann's rule in marine organisms are evident.     

Host-Parasite Interactions in Chagas Disease: Genetically Unidentical Isolates of a Single Trypanosoma cruzi Strain Identified In Vitro via LSSP-PCR

The present study aims at establishing whether the diversity in pathogenesis within a genetically diverse host population infected with a single polyclonal strain of Trypanosoma cruzi is due to selection of specific subpopulations within the strain. For this purpose we infected Swiss mice, a genetically diverse population, with the polyclonal strain of Trypanosoma cruzi Berenice-78 and characterized via LSSP-PCR the kinetoplast DNA of subpopulations isolated from blood samples collected from the animals at various times after inoculation (3, 6 and 12 months after inoculation). We examined the biological behavior of the isolates in acellular medium and in vitro profiles of infectivity in Vero cell medium. We compared the characteristics of the isolates with the inoculating strain and with another strain, Berenice 62, isolated from the same patient 16 years earlier. We found that one of the isolates had intermediate behavior in comparison with Berenice-78 and Berenice-62 and a significantly different genetic profile by LSSP-PCR in comparison with the inoculating strain. We hereby demonstrate that genetically distinct Trypanosoma cruzi isolates may be obtained upon experimental murine infection with a single polyclonal Trypanosoma cruzi strain.     

A Three-Dimensional Skeletal Reconstruction of the Stem Amniote Orobates pabsti (Diadectidae): Analyses of Body Mass,Centre of Mass Position,and Joint Mobility

Orobates pabsti, a basal diadectid from the lower Permian, is a key fossil for the understanding of early amniote evolution. Quantitative analysis of anatomical information suffers from fragmentation of fossil bones, plastic deformation due to diagenetic processes and fragile preservation within surrounding rock matrix, preventing further biomechanical investigation. Here we describe the steps taken to digitally reconstruct MNG 10181, the holotype specimen of Orobates pabsti, and subsequently use the digital reconstruction to assess body mass, position of the centre of mass in individual segments as well as the whole animal, and study joint mobility in the shoulder and hip joints. The shape of most fossil bone fragments could be recovered from micro-focus computed tomography scans. This also revealed structures that were hitherto hidden within the rock matrix. However, parts of the axial skeleton had to be modelled using relevant isolated bones from the same locality as templates. Based on the digital fossil, mass of MNG 10181 was estimated using a model of body shape that was varied within a plausible range to account for uncertainties of the dimension. In the mean estimate model the specimen had an estimated mass of circa 4 kg. Varying of the mass distribution amongst body segments further revealed that Orobates carried most of its weight on the hind limbs. Mostly unrestricted joint morphology further suggested that MNG 10181 was able to effectively generate propulsion with the pelvic limbs. The digital reconstruction is made available for future biomechanical studies.     

Structure and growth pattern of the bizarre hemispheric prominence on the rostrum of the fossil beaked whale Globicetus hiberus (Mammalia,Cetacea, Ziphiidae)

The rostrum of most ziphiids (beaked whales) displays bizarre swollen regions, accompanied with extreme hypermineralisation and an alteration of the collagenous mesh of the bone. The functional significance of this specialization remains obscure. With the voluminous and dense hemispheric excrescence protruding from the premaxillae, the recently described fossil ziphiid Globicetus hiberus is the most spectacular case. This study describes the histological structure and interprets the growth pattern of this unique feature. Histologically, the prominence in Globicetus is made up of an atypical fibro‐lamellar complex displaying an irregular laminar organization and extreme compactness (osteosclerosis). Its development is suggested to have resulted from a protraction of periosteal accretion over the premaxillae, long after the end of somatic growth. Complex shifts in the geometry of this tissue are likely to have occurred during its accretion and no indication of Haversian remodeling could be found. X‐ray diffraction and Raman spectroscopy indicate that the bone matrix in the premaxillary prominence of Globicetus closely resembles that of the rostrum of the extant beaked whale Mesoplodon densirostris: apatite crystals are of common size and strongly oriented, but the collagenous meshwork within bone matrix seems to be extremely sparse. These morphological and structural data are discussed in the light of functional interpretations proposed for the highly unusual and diverse ziphiid rostrum. J. Morphol. 277:1292–1308, 2016. © 2016 Wiley Periodicals, Inc.     

Acclimation to UV irradiance in Gracilaria chilensis Bird,McLachlan & Oliveira (Gigartinales,Rhodophyta)

Photoautotrophs can cope with an increase in ultraviolet (UV) irradiance in the aquatic environment, through protection and acclimation mechanisms (i.e. synthesis of UV-absorbing compounds). This capacity has been proven to vary according to the organism's sensitivity. To quantify variations of this capacity between the different parts of macroalgae, an in vitro study was performed with the tips, cystocarps and thalli segments of Gracilaria chilensis. Whole algae incubated during 3 days at high and low PAR, supplying UV B (4.6 µW cm^–2) during 2 hours showed, as predicted, an increase in absorption (OD) at 320 nm of the different parts, after the first day of exposure to UV B. The tips presented the highest increase in the standardized OD at 320 nm relative to cystocarps and thalli segments; their mean percentage of increase was 38% and 29% at low and high PAR, respectively. The lowest sensitivity was consistently found in the thalli segments, while the highest was in the tips. The tips are important for growth and therefore they play a major role in the maintenance of the Gracilaria populations. Acclimation mechanisms that occurred in a short time scale, and mainly in the tips, may allow Gracilaria to have an almost immediate protection to increases in UV B fluxes.