Drought-induced Suppression of Female Fecundity in a Capital Breeder.

Human-induced global climate change is exerting increasingly strong selective pressures on a myriad of fitness traits that affect organisms. These traits, in turn, are influenced by a variety of environmental parameters such as temperature and precipitation, particularly in ectothermic taxa such as amphibians and reptiles. Over the past several decades, severe and prolonged episodes of drought are becoming commonplace throughout North America. Documentation of responses to this environmental crisis, however, is often incomplete, particularly in cryptic species. Here, we investigated reproduction in a population of pitviper snakes (copperhead, Agkistrodon contortrix), a live-bearing capital breeder. This population experienced a severe drought from 2012 through 2016. We tested whether declines in number of progeny were linked to this drought. Decline in total number offspring was significant, but offspring length and mass were unaffected. Reproductive output was positively impacted by precipitation and negatively impacted by high temperatures. We hypothesized that severe declines of prey species (e.g., cicada, amphibians, and small mammals) reduced energy acquisition during drought, negatively impacting reproductive output of the snakes. Support for this view was found using the periodical cicada (Magicicada spp.) as a proxy for prey availability. Various climate simulations, including our own qualitative analysis, predict that drought events will continue unabated throughout the geographic distribution of copperheads which suggests that long-term monitoring of populations are needed to better understand geographic variation in drought resilience and cascading impacts of drought phenomena on ecosystem function.

Seed ingestion and germination in rattlesnakes: overlooked agents of rescue and secondary dispersal.

Seed dispersal is a key evolutionary process and a central theme in the population ecology of terrestrial plants. The primary producers of most land-based ecosystems are propagated by and maintained through various mechanisms of seed dispersal that involve both abiotic and biotic modes of transportation. By far the most common biotic seed transport mechanism is zoochory, whereby seeds, or fruits containing them, are dispersed through the activities of animals. Rodents are one group of mammals that commonly prey on seeds (granivores) and play a critical, often destructive, role in primary dispersal and the dynamics of plant communities. In North America, geomyid, heteromyid and some sciurid rodents have specialized cheek pouches for transporting seeds from plant source to larder, where they are often eliminated from the pool of plant propagules by consumption. These seed-laden rodents are commonly consumed by snakes as they forage, but unlike raptors, coyotes, bobcats, and other endothermic predators which eat rodents and are known or implicated to be secondary seed dispersers, the role of snakes in seed dispersal remains unexplored. Here, using museum-preserved specimens, we show that in nature three desert-dwelling rattlesnake species consumed heteromyids with seeds in their cheek pouches. By examining the entire gut we discovered, furthermore, that secondarily ingested seeds can germinate in rattlesnake colons. In terms of secondary dispersal, rattlesnakes are best described as diplochorous. Because seed rescue and secondary dispersal in snakes has yet to be investigated, and because numerous other snake species consume granivorous and frugivorous birds and mammals, our observations offer direction for further empirical studies of this unusual but potentially important channel for seed dispersal.

Differential proteomic and behavioral effects of long-term voluntary exercise in wild-type and APP-overexpressing transgenics.

Physical exercise may provide protection against the cognitive decline and neuropathology associated with Alzheimer's disease, although the mechanisms are not clear. In the present study, APP/PSEN1 double-transgenic and wild-type mice were allowed unlimited voluntary exercise for 7months. Consistent with previous reports, wheel-running improved cognition in the double-transgenic mice. Interestingly, the average daily distance run was strongly correlated with spatial memory in the water maze in wild-type mice (r(2)=.959), but uncorrelated in transgenics (r(2)=.013). Proteomics analysis showed that sedentary transgenic mice differed significantly from sedentary wild-types with respect to proteins involved in synaptic transmission, cytoskeletal regulation, and neurogenesis. When given an opportunity to exercise, the transgenics' deficiencies in cytoskeletal regulation and neurogenesis largely normalized, but abnormal synaptic proteins did not change. In contrast, exercise enhanced proteins associated with cytoskeletal regulation, oxidative phosphorylation, and synaptic transmission in wild-type mice. Soluble and insoluble Aß40 and Aß42 levels were significantly decreased in both cortex and hippocampus of active transgenics, suggesting that this may have played a role in the cognitive improvement in APP/PSEN1 mice. ß-secretase was significantly reduced in active APP/PSEN1 mice compared to sedentary controls, suggesting a mechanism for reduced Aß. Taken together, these data illustrate that exercise improves memory in wild-type and APP-overexpressing mice in fundamentally different ways.

Effects of Intensive Family Preservation Services in Rural Tennessee on Parental Hopefulness with Families Affected by Substance Use.

This article describes how Building Strong Families in Rural Tennessee (BS-FinRT) increased hopefulness and helped to promote the policy goal of developing a recovery focus among families with vulnerabilities. These outcomes were achieved by implementing collaborative strategies for addressing issues of child safety, substance use, and family stability. Early analyses of the program's outcomes indicated an unexpected positive influence on parent and child hopefulness. Further analyses found that changes in hope between baseline and discharge correlated positively with changes over the same time period in problem severity, general functioning, and mental health symptomology.

Spatial and nonspatial escape strategies in the Barnes maze.

The Barnes maze is a spatial memory task that requires subjects to learn the position of a hole that can be used to escape the brightly lit, open surface of the maze. Two experiments assessed the relative importance of spatial (extra-maze) versus proximal visible cues in solving the maze. In Experiment 1, four groups of mice were trained either with or without a discrete visible cue marking the location of the escape hole, which was either in a fixed or variable location across trials. In Experiment 2, all mice were trained with the discrete visible cue marking the target hole location. Two groups were identical to the cued-target groups from Experiment 1, with either fixed or variable escape locations. For these mice, the discrete cue either was the sole predictor of the target location or was perfectly confounded with the spatial extra-maze cues. The third group also used a cued variable target, but a curtain was drawn around the maze to prevent the use of spatial cues to guide navigation. Probe trials with all escape holes blocked were conducted to dissociate the use of spatial and discrete proximal cues. We conclude that the Barnes maze can be solved efficiently using spatial, visual cue, or serial-search strategies. However, mice showed a strong preference for using the distal room cues, even when a discrete visible cue clearly marked the escape location. Importantly, these data show that the cued-target control version of the Barnes maze as typically conducted does not dissociate spatial from nonspatial abilities.