Nonrandom dispersal drives phenotypic divergence within a bird population

Gene flow through dispersal has traditionally been thought to function as a force opposing evolutionary differentiation. However, directional gene flow may actually reinforce divergence of populations in close proximity. This study documents the phenotypic differentiation over more than two decades in body size (tarsus length) at a very short spatial scale (1.1 km) within a population of pied flycatchers Ficedula hypoleuca inhabiting deciduous and coniferous habitats. Unlike females, males breeding in the deciduous forest were consistently larger than those from the managed coniferous forest. This assortment by size is likely explained by preset habitat preferences leading to dominance of the largest males and exclusion of the smallest ones toward the nonpreferred coniferous forest coupled with directional dispersal. Movements of males between forests were nonrandom with respect to body size and flow rate, which might function to maintain the phenotypic variation in this heritable trait at such a small spatial scale. However, a deeply rooted preference for the deciduous habitat might not be in line with its quality due to the increased levels of breeding density of hole‐nesting competitors therein. These results illustrate how eco‐evolutionary scenarios can develop under directional gene flow over surprisingly small spatial scales. Our findings come on top of recent studies concerning new ways in which dispersal and gene flow can influence microevolution.     

Preservation of RNA and DNA from mammal samples under field conditions

Ecological and conservation genetics require sampling of organisms in the wild. Appropriate preservation of the collected samples, usually by cryostorage, is key to the quality of the genetic data obtained. Nevertheless, cryopreservation in the field to ensure RNA and DNA stability is not always possible. We compared several nucleic acid preservation solutions appropriate for field sampling and tested them on rat (Rattus rattus) blood, ear and tail tip, liver, brain and muscle. We compared the efficacy of a nucleic acid preservation (NAP) buffer for DNA preservation against 95% ethanol and Longmire buffer, and for RNA preservation against RNAlater (Qiagen) and Longmire buffer, under simulated field conditions. For DNA, the NAP buffer was slightly better than cryopreservation or 95% ethanol, but high molecular weight DNA was preserved in all conditions. The NAP buffer preserved RNA as well as RNAlater. Liver yielded the best RNA and DNA quantity and quality; thus, liver should be the tissue preferentially collected from euthanized animals. We also show that DNA persists in nonpreserved muscle tissue for at least 1 week at ambient temperature, although degradation is noticeable in a matter of hours. When cryopreservation is not possible, the NAP buffer is an economical alternative for RNA preservation at ambient temperature for at least 2 months and DNA preservation for at least 10 months.     

An Appended Domain Results in an Unusual Architecture for Malaria Parasite Tryptophanyl-tRNA Synthetase

Specific activation of amino acids by aminoacyl-tRNA synthetases (aaRSs) is essential for maintaining fidelity during protein translation. Here, we present crystal structure of malaria parasite Plasmodium falciparum tryptophanyl-tRNA synthetase (Pf-WRS) catalytic domain (AAD) at 2.6 Å resolution in complex with L-tryptophan. Confocal microscopy-based localization data suggest cytoplasmic residency of this protein. Pf-WRS has an unusual N-terminal extension of AlaX-like domain (AXD) along with linker regions which together seem vital for enzymatic activity and tRNA binding. Pf-WRS is not proteolytically processed in the parasites and therefore AXD likely provides tRNA binding capability rather than editing activity. The N-terminal domain containing AXD and linker region is monomeric and would result in an unusual overall architecture for Pf-WRS where the dimeric catalytic domains have monomeric AXDs on either side. Our PDB-wide comparative analyses of 47 WRS crystal structures also provide new mechanistic insights into this enzyme family in context conserved KMSKS loop conformations.     

Causes of Stranding and Mortality,and Final Disposition of Loggerhead Sea Turtles (Caretta caretta) Admitted to a Wildlife Rehabilitation Center in Gran Canaria Island,Spain (1998-2014): A Long-Term Retrospective Study

Aims

The aims of this study were to analyze the causes of stranding of 1,860 loggerhead turtles (Caretta caretta) admitted at the Tafira Wildlife Rehabilitation Center in Gran Canaria Island, Spain, from 1998 to 2014, and to analyze the outcomes of the rehabilitation process to allow meaningful auditing of its quality.

Methods

Primary causes of morbidity were classified into seven categories: entanglement in fishing gear and/or plastics, ingestion of hooks and monofilament lines, trauma, infectious disease, crude oil, other causes, and unknown/undetermined. Final dispositions were calculated as euthanasia (E_r), unassisted mortality (M_r), and release (R_r) rates. Time to death (T_d) for euthanized and dead turtles, and length of stay for released (T_r) turtles were evaluated.

Results

The most frequent causes of morbidity were entanglement in fishing gear and/or plastics (50.81%), unknown/undetermined (20.37%), and ingestion of hooks (11.88%). The final disposition of the 1,634 loggerhead turtles admitted alive were: E_r = 3.37%, M_r = 10.34%, and R_r = 86.29%. E_r was significantly higher in the trauma category (18.67%) compared to the other causes of admission. The highest M_r was observed for turtles admitted due to trauma (30.67%). The highest R_r was observed in the crude oil (93.87%) and entanglement (92.38%) categories. The median T_r ranged from 12 days (unknown) to 70 days (trauma).

Conclusions

This survey is the first large-scale epidemiological study on causes of stranding and mortality of Eastern Atlantic loggerheads and demonstrates that at least 71.72% of turtles stranded due to anthropogenic causes. The high R_r (86.29%) emphasizes the importance of marine rehabilitation centers for conservation purposes. The stratified analysis by causes of admission of the three final disposition rates, and the parameters T_d and T_r should be included in the outcome research of the rehabilitation process of sea turtles in order to allow comparative studies between marine rehabilitation centers around the world.     

Characterization of Lethal Zika Virus Infection in AG129 Mice

BackgroundMosquito-borne Zika virus (ZIKV) typically causes a mild and self-limiting illness known as Zika fever, which often is accompanied by maculopapular rash, headache, and myalgia. During the current outbreak in South America, ZIKV infection during pregnancy has been hypothesized to cause microcephaly and other diseases. The detection of ZIKV in fetal brain tissue supports this hypothesis. Because human infections with ZIKV historically have remained sporadic and, until recently, have been limited to small-scale epidemics, neither the disease caused by ZIKV nor the molecular determinants of virulence and/or pathogenicity have been well characterized. Here, we describe a small animal model for wild-type ZIKV of the Asian lineage.Conclusions/SignificanceFoot pad injection of AG129 mice with ZIKV represents a biologically relevant model for studying ZIKV infection and disease development following wild-type virus inoculation without the requirement for adaptation of the virus or intracerebral delivery of the virus. This newly developed Zika disease model can be exploited to identify determinants of ZIKV virulence and reveal molecular mechanisms that control the virus-host interaction, providing a framework for rational design of acute phase therapeutics and for vaccine efficacy testing.     

Morphological and sexual traits in Atlas and Iberian Pied Flycatchers Ficedula hypoleuca speculigera and F. h. iberiae: a comparison

Capsule: There are significant biometric differences between Pied Flycatchers from Iberian and north African populations which are consistent with proposals to classify the two forms into separate species.

Aims: To determine the similarities and differences in the main biometrical and plumage sex traits between populations of the Iberian Pied Flycatcher Ficedula hypoleuca iberiae and the Atlas Flycatcher Ficedula hypoleuca speculigera.

Methods: Biometric and plumage traits of 193 breeding individuals of Iberian Pied Flycatchers and 43 Atlas Flycatchers were measured in 2014 with standardized protocols.

Results: Both sexes of Atlas Flycatchers were larger than Iberian Pied Flycatchers in skeletal (tarsus) and wing size and also differed in bill morphology, which was wider but shallower in speculigera than iberiae, with females (but not males) having shorter bills than iberiae females. Males differed in mantle colour and forehead patch size, with speculigera males being darker and displaying larger forehead patches than iberiae males. As in populations of iberiae, some speculigera females also expressed a white forehead patch.

Conclusion: We demonstrate significant phenotypic differences between Iberian Pied Flycatchers and Atlas Flycatchers with respect to size and traits of ecological and evolutionary relevance, supporting the recently proposed scenarios on their independent evolution.     

Phenotype Matching and Early Social Conditions Affect Shoaling and Exploration Decisions

Early social conditions are vital for the establishment of future social interactions. Less, however, is known about how differences in early social conditions contribute to the process of individual recognition and subsequently in the decision of associating and exploring behaviours. In this study, we address this gap in the Trinidadian guppy Poecilia reticulata and test the prediction that fish would show a higher tendency to recognize and associate with individuals of similar phenotype. This prediction was tested by comparing the likelihood of association and latency to explore a novel area in males and females when in the presence of individuals that were familiar (reared together but from different populations), from the same population of origin (from the same population but deprived of interaction with each other), or were unfamiliar (different population and have never interacted). Both early social conditions and population of origin (phenotype matching) affected the tendency to shoal and explore. Females, but not males, exhibited identical preference to associate either with unfamiliar females as with familiar females from a different population. Importantly, female preference did not occur with unfamiliar individuals from a different population. In contrast with our prediction, tendency to shoal did not predict exploration propensity. Males always start exploration before the group whenever unfamiliar males composed the group. Females on the other hand only moved to the novel area after seeing the group doing so, revealing sexual dimorphism in exploratory behaviour. Our results provide evidence for a familiarity and phenotypic matching recognition mechanism at the population level and also highlight the importance of accounting for differences between sexes when investigating the effects of early social conditions.     

Climate change,extinction, and Sky Island biogeography in a montane lizard

Around the world, many species are confined to “Sky Islands,” with different populations in isolated patches of montane habitat. How does this pattern arise? One scenario is that montane species were widespread in lowlands when climates were cooler, and were isolated by local extinction caused by warming conditions. This scenario implies that many montane species may be highly susceptible to anthropogenic warming. Here, we test this scenario in a montane lizard (Sceloporus jarrovii) from the Madrean Sky Islands of southeastern Arizona. We combined data from field surveys, climate, population genomics, and physiology. Overall, our results support the hypothesis that this species' current distribution is explained by local extinction caused by past climate change. However, our results for this species differ from simple expectations in several ways: (a) their absence at lower elevations is related to warm winter temperatures, not hot summer temperatures; (b) they appear to exclude a low‐elevation congener from higher elevations, not the converse; (c) they are apparently absent from many climatically suitable but low mountain ranges, seemingly “pushed off the top” by climates even warmer than those today; (d) despite the potential for dispersal among ranges during recent glacial periods (~18,000 years ago), populations in different ranges diverged ~4.5–0.5 million years ago and remained largely distinct; and (e) body temperatures are inversely related to climatic temperatures among sites. These results may have implications for many other Sky Island systems. More broadly, we suggest that Sky Island species may be relevant for predicting responses to future warming.     

Leishmania amazonensis: Anionic currents expressed in oocytes upon microinjection of mRNA from the parasite

Transport mechanisms involved in pH homeostasis are relevant for the survival of Leishmania parasites. The presence of chloride conductive pathways in Leishmania has been anticipated since anion channel inhibitors limit the proton extrusion mediated by the H+ATPase, which is the major regulator of intracellular pH in amastigotes. In this study, we used Xenopus laevis oocytes as a heterologous expression system in which to study the expression of ion channels upon microinjection of polyA mRNA from Leishmania amazonensis. After injection of polyA mRNA into the oocytes, we measured three different types of currents. We discuss the possible origin of each, and propose that Type 3 currents could be the result of the heterologous expression of proteins from Leishmania since they show different pharmacological and biophysical properties as compared to endogenous oocyte currents.     

In vivo gene regulation in Salmonella spp. by a salicylate-dependent control circuit

Systems allowing tightly regulated expression of prokaryotic genes in vivo are important for performing functional studies of bacterial genes in host-pathogen interactions and establishing bacteria-based therapies. We integrated a regulatory control circuit activated by acetyl salicylic acid (ASA) in attenuated Salmonella enterica that carries an expression module with a gene of interest under control of the XylS2-dependent Pm promoter. This resulted in 20-150-fold induction ex vivo. The regulatory circuit was also efficiently induced by ASA when the bacteria resided in eukaryotic cells, both in vitro and in vivo. To validate the circuit, we administered Salmonella spp., carrying an expression module encoding the 5-fluorocytosine-converting enzyme cytosine deaminase in the bacterial chromosome or in a plasmid, to mice with tumors. Induction with ASA before 5-fluorocytosine administration resulted in a significant reduction of tumor growth. These results demonstrate the usefulness of the regulatory control circuit to selectively switch on gene expression during bacterial infection.