Risky Courtship: Background Contrast,Ornamentation, and Display Behavior of Wolf Spiders Affect Visual Detection by Toad Predators

Males that search widely for females and perform conspicuous courtship displays run a high risk of being detected by their predators. Therefore, gains in reproductive success might be offset by increased mortality due to predation. Male brush‐legged wolf spiders (Schizocosa ocreata) with larger decorative traits (foreleg tufts) are preferred by females as mates, but are more readily detected by predators. However, predation risk may also be influenced by the interaction between components of signals and the environment in which signaling occurs. Courting male spiders were readily accepted as prey by a sympatric predator, the American toad (Anaxyrus americanus). We used video playback to tease apart the interactive effect between visual signals and the signaling environment on the ability of toads to detect courting spiders as a function of distance, background contrast, the presence or absence of male foreleg tufts, and behavioral activity. The response of toads to video sequences of male spiders was similar to their response to live male spiders. Toad response varied over distance toward spiders displayed against high contrast (sunny) vs. low contrast (shaded) backgrounds. Beyond 30 cm, more toads detected courting male spiders against light, ‘sunny’ backgrounds and detected them faster when compared to the same spider stimulus against darker, ‘shady’ backgrounds. In choice tests, toads oriented more often toward courting males with leg tufts than those without. Toad responses also varied with male spider behavior in that only videos of moving males were attacked. Latency to orient and detection by toads was significantly greater for walking males than courting males, and this effect was most evident at distances between 30 cm and 50 cm. Results supported that courting wolf spiders are at significant risk of predation by visually acute predators. Distance, background contrast, and the presence of foreleg decorations influence detection probability. Thus, the same complex visual signals that make males conspicuous and are preferred by females can make males more vulnerable as prey to toads.     

DnaJ/Hsc70 chaperone complexes control the extracellular release of neurodegenerative‐associated proteins

It is now known that proteins associated with neurodegenerative disease can spread throughout the brain in a prionlike manner. However, the mechanisms regulating the trans‐synaptic spread propagation, including the neuronal release of these proteins, remain unknown. The interaction of neurodegenerative disease‐associated proteins with the molecular chaperone Hsc70 is well known, and we hypothesized that much like disaggregation, refolding, degradation, and even normal function, Hsc70 may dictate the extracellular fate of these proteins. Here, we show that several proteins, including TDP‐43, α‐synuclein, and the microtubule‐associated protein tau, can be driven out of the cell by an Hsc70 co‐chaperone, DnaJC5. In fact, DnaJC5 overexpression induced tau release in cells, neurons, and brain tissue, but only when activity of the chaperone Hsc70 was intact and when tau was able to associate with this chaperone. Moreover, release of tau from neurons was reduced in mice lacking the DnaJC5 gene and when the complement of DnaJs in the cell was altered. These results demonstrate that the dynamics of DnaJ/Hsc70 complexes are critically involved in the release of neurodegenerative disease proteins.     

Biodegradability of Vegetation-Derived Dissolved Organic Carbon in a Cool Temperate Ombrotrophic Bog

Dissolved organic carbon (DOC) plays a key role in the peatland carbon balance and serves numerous ecological and chemical functions including acting as a microbial substrate. In this study, we quantify the concentration, biodegradability, and intrinsic properties of DOC obtained from peat, fresh material, and litter from nine species of ombrotrophic bog vegetation. Potential biodegradability was assessed by incubating vegetation extracts for 28 days in the dark and measuring percent DOC loss as the fraction of biodegradable DOC (%BDOC) while DOC properties were characterized using UV–Vis absorbance and fluorescence measurements. The mean initial DOC concentration extracted differed significantly among species (P < 0.05) and was significantly higher in fresh material, 217 ± 259 mg DOC l^?1, than either litter or peat extracts with mean concentrations of 82.1 ± 117 mg DOC l^?1 and 12.7 ± 1.0 mg DOC l^?1, respectively (P < 0.05). %BDOC also differed significantly among species (P < 0.05) and ranged from 52 to 73% in fresh cuttings with the greatest fraction observed in S. magellanicum; 22–46% in litter; and 24% in peat. The majority of variability (82.5%) in BDOC was explained by initial absorbance at 254 nm and total dissolved nitrogen concentration which was further resolved into significant non-linear relationships between %BDOC and both humic-like and protein-like DOC fractions (P < 0.05). Our results highlight the extremely heterogeneous nature of the surface vegetation-derived DOC input in peatlands and stress the importance of vegetation species in peatland ecosystem function.     

Examining the sensitivity of molecular species delimitations to the choice of mitochondrial marker

Defining and understanding species diversity forms the basis of a wide range of biological and conservation work. Traditional taxonomy can be complemented and accelerated using molecular methods of species delimitation, such as the widely used Generalised Mixed Yule-Coalescent (GMYC) approach. This method uses time-calibrated phylogenetic trees in order to identify transition points between inter- and intraspecific divergence processes. Despite some important limitations, the GMYC approach appears to be robust to a wide range of dataset characteristics. It is one of the few model-based species-delimitation methods that remain practical for analysing molecular datasets with a large numbers of taxa. Most GMYC analyses have been based on datasets consisting of one or a small number of mitochondrial genes. To investigate the sensitivity of GMYC to the choice of mitochondrial marker, we compared GMYC estimates from 15 mitochondrial genes for three vertebrate datasets (cetaceans, ursids and whitefish). Despite the shared evolutionary history among mitochondrial genes, different markers exhibited substantial variation in GMYC delimitation results across all three datasets. This variability was not restricted to specific genes or taxa and extended to commonly used barcoding genes such as COI and CYTB. Using multiple concatenated markers mitigated these problems in two of the datasets, but exacerbated systematic biases present in a third. Our findings indicate the need to consider multiple markers, loci and lines of evidence when performing molecular species delimitation.     

The macroecology of infectious diseases: a new perspective on global‐scale drivers of pathogen distributions and impacts

Identifying drivers of infectious disease patterns and impacts at the broadest scales of organisation is one of the most crucial challenges for modern science, yet answers to many fundamental questions remain elusive. These include what factors commonly facilitate transmission of pathogens to novel host species, what drives variation in immune investment among host species, and more generally what drives global patterns of parasite diversity and distribution? Here we consider how the perspectives and tools of macroecology, a field that investigates patterns and processes at broad spatial, temporal and taxonomic scales, are expanding scientific understanding of global infectious disease ecology. In particular, emerging approaches are providing new insights about scaling properties across all living taxa, and new strategies for mapping pathogen biodiversity and infection risk. Ultimately, macroecology is establishing a framework to more accurately predict global patterns of infectious disease distribution and emergence.