Efficacy of N-mixture models for surveying and monitoring white-tailed deer populations

Automated cameras have become increasingly common for monitoring wildlife populations and estimating abundance. Most analytical methods, however, fail to account for incomplete and variable detection probabilities, which biases abundance estimates. Methods which do account for detection have not been thoroughly tested, and those that have been tested were compared to other methods of abundance estimation. The goal of this study was to evaluate the accuracy and effectiveness of the N-mixture method, which explicitly incorporates detection probability, to monitor white-tailed deer (Odocoileus virginianus) by using camera surveys and a known, marked population to collect data and estimate abundance. Motion-triggered camera surveys were conducted at Auburn University’s deer research facility in 2010. Abundance estimates were generated using N-mixture models and compared to the known number of marked deer in the population. We compared abundance estimates generated from a decreasing number of survey days used in analysis and by time periods (DAY, NIGHT, SUNRISE, SUNSET, CREPUSCULAR, ALL TIMES). Accurate abundance estimates were generated using 24 h of data and nighttime only data. Accuracy of abundance estimates increased with increasing number of survey days until day 5, and there was no improvement with additional data. This suggests that, for our system, 5-day camera surveys conducted at night were adequate for abundance estimation and population monitoring. Further, our study demonstrates that camera surveys and N-mixture models may be a highly effective method for estimation and monitoring of ungulate populations.     

Reduced primary cilia length and altered Arl13b expression are associated with deregulated chondrocyte Hedgehog signaling in alkaptonuria

Alkaptonuria (AKU) is a rare inherited disease resulting from a deficiency of the enzyme homogentisate 1,2‐dioxygenase which leads to the accumulation of homogentisic acid (HGA). AKU is characterized by severe cartilage degeneration, similar to that observed in osteoarthritis. Previous studies suggest that AKU is associated with alterations in cytoskeletal organization which could modulate primary cilia structure/function. This study investigated whether AKU is associated with changes in chondrocyte primary cilia and associated Hedgehog signaling which mediates cartilage degradation in osteoarthritis. Human articular chondrocytes were obtained from healthy and AKU donors. Additionally, healthy chondrocytes were treated with HGA to replicate AKU pathology (+HGA). Diseased cells exhibited shorter cilia with length reductions of 36% and 16% in AKU and +HGA chondrocytes respectively, when compared to healthy controls. Both AKU and +HGA chondrocytes demonstrated disruption of the usual cilia length regulation by actin contractility. Furthermore, the proportion of cilia with axoneme breaks and bulbous tips was increased in AKU chondrocytes consistent with defective regulation of ciliary trafficking. Distribution of the Hedgehog‐related protein Arl13b along the ciliary axoneme was altered such that its localization was increased at the distal tip in AKU and +HGA chondrocytes. These changes in cilia structure/trafficking in AKU and +HGA chondrocytes were associated with a complete inability to activate Hedgehog signaling in response to exogenous ligand. Thus, we suggest that altered responsiveness to Hedgehog, as a consequence of cilia dysfunction, may be a contributing factor in the development of arthropathy highlighting the cilium as a novel target in AKU.     

Explaining ecological shifts: the roles of temperature and primary production in the long‐term dynamics of benthic faunal composition

Predicting the ecological consequences of environmental change requires that we can identify the drivers of long‐term ecological variation. Biological assemblages can exhibit abrupt deviations from temporal trends, potentially resulting in irreversible shifts in species composition over short periods of time. Such dynamics are hypothesised to occur as gradual forcing eventually causes biological thresholds to be crossed, but could also be explained by biota simply tracking abrupt changes to their environment. Here, we modelled temporal variation in a North Sea benthic faunal assemblage over a 40‐year period (1972–2012) to test for changes to temporal trends of biota and determine whether they could be explained by underlying patterns in sea temperature and primary production. These extrinsic factors were postulated to influence community dynamics through their roles in determining and sustaining the metabolic demands of organisms, respectively. A subset of mainly large and long‐lived taxa (those loaded on the first principal component of taxa densities) exhibited two significant changes to their temporal trends, which culminated in a shift in assemblage composition. These changes were explained by an increase in pelagic primary production, and hence detrital food input to the seabed, but were unrelated to variation in sea temperature. A second subset of mainly small and short‐lived taxa (those loaded on the second principal component) did not experience any significant changes to their temporal trends, as enhanced pelagic primary production appeared to mitigate the impact of warming on these organisms. Our results suggest that abrupt ecological shifts can occur as biota track underlying variation in extrinsic factors, in this case primary production. Changes to the structure of ecosystems may therefore be predictable based on environmental change projections.     

Modification of littoral algal assemblages by gardening caddisfly larvae

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Exogenous and endogenous corticosterone in feathers

In birds, the steroid hormone corticosterone (CORT) increases in response to real or perceived threats to homeostasis. A long‐term record of CORT exposure is recorded in feathers when the hormone is incorporated into the keratinized tissue, and then preserved when the mature feather is cut off from the blood supply. The opportunity to retrospectively assess the exposure of an individual to stressors by measuring the amount of CORT in a feather has generated excitement amongst avian ecologists. However, this technique is relatively new and requires additional validations. In this study, we performed experiments in wild caught European starlings Sturnus vulgaris to test whether: 1) CORT deposition in the feather depends on time of day and 2) whether an ecologically relevant stressor (unpredictable food access) causes a change in feather CORT. We found that exogenous CORT was incorporated into feathers during the day and the night. However, there was no difference in feather CORT between birds with unpredictable access to food and those with continuous access, indicating that feather CORT might not always detect ecologically relevant stressors.     

Reduced expression of PMCA1 is associated with increased blood pressure with age which is preceded by remodelling of resistance arteries

Hypertension is a well‐established risk factor for adverse cardiovascular events, and older age is a risk factor for the development of hypertension. Genomewide association studies have linked ATP2B1, the gene for the plasma membrane calcium ATPase 1 (PMCA1), to blood pressure (BP) and hypertension. Here, we present the effects of reduction in the expression of PMCA1 on BP and small artery structure and function when combined with advancing age. Heterozygous PMCA1 null mice (PMCA1^Ht) were generated and conscious BP was measured at 6 to 18 months of age. Passive and active properties of isolated small mesenteric arteries were examined by pressure myography. PMCA1^Ht mice exhibited normal BP at 6 and 9 months of age but developed significantly elevated BP when compared to age‐matched wild‐type controls at ≥12 months of age. Decreased lumen diameter, increased wall thickness and increased wall:lumen ratio were observed in small mesenteric arteries from animals 9 months of age and older, indicative of eutrophic remodelling. Increases in mesenteric artery intrinsic tone and global intracellular calcium were evident in animals at both 6 and 18 months of age. Thus, decreased expression of PMCA1 is associated with increased BP when combined with advancing age. Changes in arterial structure precede the elevation of BP. Pathways involving PMCA1 may be a novel target for BP regulation in the elderly.