Lateral Transfer of a Lectin-Like Antifreeze Protein Gene in Fishes

Fishes living in icy seawater are usually protected from freezing by endogenous antifreeze proteins (AFPs) that bind to ice crystals and stop them from growing. The scattered distribution of five highly diverse AFP types across phylogenetically disparate fish species is puzzling. The appearance of radically different AFPs in closely related species has been attributed to the rapid, independent evolution of these proteins in response to natural selection caused by sea level glaciations within the last 20 million years. In at least one instance the same type of simple repetitive AFP has independently originated in two distant species by convergent evolution. But, the isolated occurrence of three very similar type II AFPs in three distantly related species (herring, smelt and sea raven) cannot be explained by this mechanism. These globular, lectin-like AFPs have a unique disulfide-bonding pattern, and share up to 85% identity in their amino acid sequences, with regions of even higher identity in their genes. A thorough search of current databases failed to find a homolog in any other species with greater than 40% amino acid sequence identity. Consistent with this result, genomic Southern blots showed the lectin-like AFP gene was absent from all other fish species tested. The remarkable conservation of both intron and exon sequences, the lack of correlation between evolutionary distance and mutation rate, and the pattern of silent vs non-silent codon changes make it unlikely that the gene for this AFP pre-existed but was lost from most branches of the teleost radiation. We propose instead that lateral gene transfer has resulted in the occurrence of the type II AFPs in herring, smelt and sea raven and allowed these species to survive in an otherwise lethal niche

Paleodistributions and Comparative Molecular Phylogeography of Leafcutter Ants (Atta spp.) Provide New Insight into the Origins of Amazonian Diversity

The evolutionary basis for high species diversity in tropical regions of the world remains unresolved. Much research has focused on the biogeography of speciation in the Amazon Basin, which harbors the greatest diversity of terrestrial life. The leading hypotheses on allopatric diversification of Amazonian taxa are the Pleistocene refugia, marine incursion, and riverine barrier hypotheses. Recent advances in the fields of phylogeography and species-distribution modeling permit a modern re-evaluation of these hypotheses. Our approach combines comparative, molecular phylogeographic analyses using mitochondrial DNA sequence data with paleodistribution modeling of species ranges at the last glacial maximum (LGM) to test these hypotheses for three co-distributed species of leafcutter ants (Atta spp.). The cumulative results of all tests reject every prediction of the riverine barrier hypothesis, but are unable to reject several predictions of the Pleistocene refugia and marine incursion hypotheses. Coalescent dating analyses suggest that population structure formed recently (Pleistocene-Pliocene), but are unable to reject the possibility that Miocene events may be responsible for structuring populations in two of the three species examined. The available data therefore suggest that either marine incursions in the Miocene or climate changes during the Pleistocene—or both—have shaped the population structure of the three species examined. Our results also reconceptualize the traditional Pleistocene refugia hypothesis, and offer a novel framework for future research into the area

Sharing the burden: The interpersonal regulation of emotional arousal in mother-daughter dyads

According to social baseline theory (Beckes & Coan, 2011), load sharing is a feature of close relationships whereby the burden of emotional distress is distributed across relationship partners. Load sharing varies by physical closeness and relationship quality. We investigated the effect of load sharing on emotional arousal via galvanic skin response, an indicator of sympathetic nervous system arousal, during a social stressor. Social stress was elicited in 66 adolescent girls (Mage = 15 years) using a spontaneous public-speaking task. Mother−daughter dyads reported their relationship quality, and physical closeness was manipulated by having mothers either touch or not touch their daughter’s hand during the performance. We found evidence of load sharing among dyads who held hands, independent of relationship quality. However, without physical contact, load sharing was only evident among dyads with higher relationship quality. Thus, high relationship quality buffers against threat in a similar way to the physical comfort of a loved one

Sharing the burden: The interpersonal regulation of emotional arousal in mother-daughter dyads

According to social baseline theory (Beckes & Coan, 2011), load sharing is a feature of close relationships whereby the burden of emotional distress is distributed across relationship partners. Load sharing varies by physical closeness and relationship quality. We investigated the effect of load sharing on emotional arousal via galvanic skin response, an indicator of sympathetic nervous system arousal, during a social stressor. Social stress was elicited in 66 adolescent girls (Mage = 15 years) using a spontaneous public-speaking task. Mother-daughter dyads reported their relationship quality, and physical closeness was manipulated by having mothers either touch or not touch their daughter's hand during the performance. We found evidence of load sharing among dyads who held hands, independent of relationship quality. However, without physical contact, load sharing was only evident among dyads with higher relationship quality. Thus, high relationship quality buffers against threat in a similar way to the physical comfort of a loved one.status: publishe

Radiocarbon dating in estuarine environments

Radiocarbon (14C) is a radioactive cosmogenic isotope continuously produced in the upper atmosphere where it rapidly oxidises to 14CO2. As 14CO2, 14C enters the global carbon cycle and is incorporated into living organisms which can be radiocarbon dated following death. Radiocarbon is among the most common radiometric methods used to provide age estimates some 40–50,000 years back in time. Here, a review of the radiocarbon method covering commonly encountered problems in estuarine environments is given. Emphasis will be on methodological procedures concerning how to estimate the 14C reservoir age in these environments, including how reliably error estimates can be calculated. Subsequently, three case studies are presented, providing a short overview of investigations of 14C reservoir age variability in estuarine environments

New Insights on Polar Bear (Ursus maritimus) Diet from Faeces based on Next-Generation Sequencing Technologies

Practical tools to quantify range-wide dietary choices of the polar bear have not been well developed, thus impeding the monitoring of this species in a changing climate. Here we describe our steps toward non-invasive polar bear diet determination with the optimization of 454 pyrosequencing of a 136 base pair (bp) mitochondrial cytochrome b (cytb) fragment amplified from the extracts of captive and wild polar bear faeces. We first determine the efficacy, reliability, and accuracy of our method using five faecal samples from a captive polar bear fed a known diet at the Canadian Polar Bear Habitat in Cochrane, Ontario, Canada; 19 samples from three polar bears at the Metro Toronto Zoo, Toronto, Ontario, Canada; and seven samples from seven wild (unfed) polar bears from a holding facility in Churchill, Manitoba, Canada. We report 91% overall success in amplifying a 136 bp cytb amplicon from the faeces of polar bears. Our DNA analyses accurately recovered the vertebrate diet profiles of captive bears fed known diets. We then characterized multiyear vertebrate prey diet choices from free-ranging polar bears from the sea ice of the M’Clintock Channel polar bear management unit, Nunavut, Canada (n = 117 from an unknown number of bears). These data point to a diet unsurprisingly dominated by ringed seal (Pusa hispida) while including evidence of bearded seal (Erignathus barbatus), harbour seal (Phoca vitulina), muskox (Ovibos moschatus ssp.), Arctic fox (Vulpes lagopus), wolf (Canis lupus), Herring Gull (Larus argentatus), and Willow Ptarmigan (Lagopus lagopus). We found low levels of contamination (< 3% of sequences when present) and suggest specific process improvements to reduce contamination in range-wide studies. Together, these findings indicate that next-generation sequencing-based diet assessments show great promise in monitoring free-ranging polar bears in this time of climate change.   La réduction de la calotte glaciaire arctique suite au changement climatique risque d’avoir un effet direct sur la capacité des ours polaires à capturer les phoques, leurs principales sources de nourriture. Une surveillance précise des changements alimentaires des ours polaires s’avère ainsi essentielle pour mieux cerner l’impact des changements climatiques sur la survie de cette espèce. Nous détaillons dans cette étude, l’optimisation d’une méthode non invasive basée sur le séquençage de dernière génération (next generation sequencing - NGS) d’un fragment du gène mitochondrial cytochrome b (cytB) de 136 bp à partir de fèces d’ours polaires sauvages collectées en milieu naturel. Pour déterminer l’efficacité, la fiabilité et l’exactitude de notre méthode, nous avons analysé des fèces d›ours polaires en captivité dont le régime alimentaire était connu (Zoo Cochrane (n = 5), Toronto (Ontario, Canada) (n = 17) et des fèces d’ours polaires sauvages provenant de la ville de Churchill (Manitoba, Canada) (n= 7)) ainsi que de la région située au niveau du détroit de M’Clintock (Nunavut, Canada)(n= 117). Ces dernières fèces ont été analysées pour mieux cerner les choix alimentaires pluriannuels des ours polaires sauvages. Les profils alimentaires des ours captifs nourris avec des aliments connus ont été estimés avec précision et ont validé notre méthode. Notre étude sur les ours polaires sauvages du détroit de M’Clintock a révélé que même si le phoque annelé (Phoca hispidia) constituait la majorité de leur régime alimentaire, le phoque barbu (Erignathus barbatus), le phoque commun (Phoca vitulina), le boeuf musqué (Ovibos spp.), le renard arctique (Vulpes lagopus), le loup (Canis lupus), le goéland argenté (Larus argentatus) et le lagopède alpin (Lagopus lagopus) constituaient également des proies. Les risques de contaminations lors de l’utilisation de ces technologies NGS sont également discutés. De faibles degrés de contamination ont été observés (< 3 % des séquences lorsque la contamination était présente). Différentes stratégies sont proposées pour diminuer encore ces risques de contaminations. En conclusion notre étude démontre que les techniques de séquençage de dernière génération s’avèrent trés prometteuses pour l’étude de l’impact du changement climatique sur le régime alimentaire des ours polaires sauvages.&nbsp