Changes in seed dispersal processes and the potential for between-patch connectivity for an arid land daisy

Dispersal is a major and critical process in population biology that has been particularly challenging to study. Animals can have major roles in seed dispersal even in species that do not appear specifically adapted to animal-aided dispersal. This can occur by two processes: direct movement of diaspores by animals and modification of landscape characteristics by animals in ways that greatly influence dispersal. We exploited the production of large, persistent dispersal structures (seed heads, henceforth) by Erodiophyllum elderi (Asteraceae), a daisy from arid Australia, to further understand secondary dispersal. Seed head dispersal on and off animal tracks in eight E. elderi patches was monitored for 9.5 months by periodically recording the location of marked seed heads. Sites were located inside a reserve that excludes sheep but not kangaroos, and in a nearby area with both kangaroos and sheep. The distance moved and likelihood of seed head movement was higher in areas with sheep, and especially along animal tracks. There was clear evidence that seed heads were channeled down animal tracks during large rainfall events. Seed head dispersal away from patches occurred to a limited extent via their physical contact with sheep and potentially via wind dispersal. Thus, the advantages of this study system allowed us to demonstrate the two postulated effects of herbivores on dispersal via direct movement of seed heads, and two distinct indirect effects through landscape modification by herbivores from the creation of animal tracks and the denudation of vegetation.Louise M. Emmerson, José M. Facelli, Peter Chesson, Hugh Possingham, and Jemery R. Da

Interprofessional Peer Teaching: Assistive Device Training and Medications Impacting Safe Ambulation

ABSTRACT Purpose: An interprofessional peer teaching activity was designed and implemented to provide students with an opportunity to practice interprofessional education collaborative (IPEC) competencies while improving student knowledge of assistive devices for gait and medications impacting safe ambulation. Method: During the activity, second year physical therapy students instructed third year pharmacy students in the accurate fit and counseling for use of canes, crutches, and walkers. Pharmacy students then demonstrated these skills and were checked off on their ability to accurately fit and instruct consumers on basic gait patterns. The pharmacy students in turn educated the physical therapy students about medications that impact safe ambulation and gait training. The activity was designed to meet the interprofessional competencies of roles and responsibilities, interprofessional communication, teams and teamwork, in addition to specific course objectives. Students completed a 15-item pre- and post-knowledge assessment and a perceptions survey to evaluate the effectiveness of the peer teaching activity. Results: Significant improvements in knowledge and performance were demonstrated following participation in the activity, and students reported positive perceptions of the activity and its impact on their learning about assistive devices and medications reviewed during the session. Our results indicate that physical therapy and pharmacy students can effectively teach each other and learn about assistive devices and medications impacting safe ambulation through an interprofessional peer teaching activity. Conclusion: Peer teaching across disciplines can help prepare students to communicate and collaborate with other healthcare providers

Effect of different drying systems for the conservation of olive leaves on their nutritive value for ruminants

Leaves obtained from olive trees (Olea europaea L.) were stored under various conditions for periods up to 42 months. Duration of storage had a marked effect on crude protein digestibility of leaves when fed to sheep. Protein appeared to be unavailable to animals fed leaves stored for 24 months or longer. The effect of storage on organic matter digestibility was less dramatic and due largely to the loss of soluble cell contents (r = 0.97). As a result, the proportion of water-insoluble dry matter and lignin present in leaves increased with duration of storage while the proportion of water or acetone-water (60:30 v/v) soluble material decreased. Despite being unavailable in vivo, cellulase digestion released protein from the water-insoluble residues of stored leaves in greater amounts than that released from freshly-dried leaves. It appears likely that protein released from stored leaves was in the form of a complex and remained unavailable to the animal. Hydrolysable and condensed tannins were not detected in fresh or dried leaves and could not have acted as complexing agents. The seco-iridoid glycoside oleuropein was found in fresh tissue (69.9 g kg(-1)) but concentrations decreased on storage in parallel with the observed decrease in crude protein digestibility (r = 0.80). ((C) Elsevier/Inra)

The influence of taphonomy on histological and isotopic analyses of treated and untreated buried modern human bone

The chemical (e.g., preservation/embalming) treatment of skeletal remains can reduce overall DNA quality and quantity. The histological and stable isotope examination of treated and untreated human remains improves our understanding of how chemical preservatives impact bone diagenesis and will determine if chemical treatment adversely affects stable isotope ratio analysis of collagen. Fidelity in the application(s) of stable isotope interpretations requires that the isotope delta (δ) values have not been altered postmortem. Re-associated antimeres and refits of chemically treated and untreated rib and long bones from eight casualties [thin-sectioned human bone (n = 43) and collagen extraction/stable isotope analysis (n = 42)] from the World War II Battle of Tarawa were examined to compare skeletal elements from the same individual that had different taphonomic histories. Histological analyses included scoring upon the Oxford Histological Index (OHI) and Birefringence scale, recording microbial invasion, and general observations. The collected data were analyzed via simple descriptive statistics and paired samples t-tests. Treated remains scored higher on the OHI and for Birefringence, indicating that bone quality was good to excellent. The untreated samples scored lower on the OHI and Birefringence scales suggesting poorer preservation than the treated remains. Histology results were supported by the isotope sample preparation results: the collagen % yield was higher for treated bone than untreated bone. Additionally, chemical preservation had no meaningful impact on isotope δ values of treated and untreated remains from the same element or pair-matched elements. Overall, treated remains exhibited good preservation while untreated remains exhibit poorer preservation with significant microfocal destruction to the extent that little histological analyses can be applied. Stable isotope ratio analysis is viable for both treated and untreated remains indicating this testing modality likely can be used for most treated remains, regardless of origin

Tillage energy savings from zone burial of shredded and whole cotton stalks

Two prototypes of a stalk burial implement were tested for energy requirements at the University of California, Shafter Research Station. Both versions of the implement are designed to bury the cotton stalks in a concentrated Zone and reform the bed in the same location. To plow under shredded stalks, both versions of the implement required less energy than a conventional tillage systems typical of the San Joaquin Valley of California. Both stalk burial implements were also used to plow under whole cotton stalks. This offers additional energy savings by eliminating the stalk shredding operation

Fluctuation induces evolutionary branching in a modeled microbial ecosystem

The impact of environmental fluctuation on species diversity is studied with a model of the evolutionary ecology of microorganisms. We show that environmental fluctuation induces evolutionary branching and assures the consequential coexistence of multiple species. Pairwise invasibility analysis is applied to illustrate the speciation process. We also discuss how fluctuation affects species diversity.Comment: 4 pages, 4 figures. Submitted to Physical Review Letter

Invasion speeds for structured populations in fluctuating environments

We live in a time where climate models predict future increases in environmental variability and biological invasions are becoming increasingly frequent. A key to developing effective responses to biological invasions in increasingly variable environments will be estimates of their rates of spatial spread and the associated uncertainty of these estimates. Using stochastic, stage-structured, integro-difference equation models, we show analytically that invasion speeds are asymptotically normally distributed with a variance that decreases in time. We apply our methods to a simple juvenile-adult model with stochastic variation in reproduction and an illustrative example with published data for the perennial herb, \emph{Calathea ovandensis}. These examples buttressed by additional analysis reveal that increased variability in vital rates simultaneously slow down invasions yet generate greater uncertainty about rates of spatial spread. Moreover, while temporal autocorrelations in vital rates inflate variability in invasion speeds, the effect of these autocorrelations on the average invasion speed can be positive or negative depending on life history traits and how well vital rates ``remember'' the past

Spatial complementarity and the coexistence of species

Coexistence of apparently similar species remains an enduring paradox in ecology. Spatial structure has been predicted to enable coexistence even when population-level models predict competitive exclusion if it causes each species to limit its own population more than that of its competitor. Nevertheless, existing hypotheses conflict with regard to whether clustering favours or precludes coexistence. The spatial segregation hypothesis predicts that in clustered populations the frequency of intra-specific interactions will be increased, causing each species to be self-limiting. Alternatively, individuals of the same species might compete over greater distances, known as heteromyopia, breaking down clusters and opening space for a second species to invade. In this study we create an individual-based model in homogeneous two-dimensional space for two putative sessile species differing only in their demographic rates and the range and strength of their competitive interactions. We fully characterise the parameter space within which coexistence occurs beyond population-level predictions, thereby revealing a region of coexistence generated by a previously-unrecognised process which we term the triadic mechanism. Here coexistence occurs due to the ability of a second generation of offspring of the rarer species to escape competition from their ancestors. We diagnose the conditions under which each of three spatial coexistence mechanisms operates and their characteristic spatial signatures. Deriving insights from a novel metric — ecological pressure — we demonstrate that coexistence is not solely determined by features of the numerically-dominant species. This results in a common framework for predicting, given any pair of species and knowledge of the relevant parameters, whether they will coexist, the mechanism by which they will do so, and the resultant spatial pattern of the community. Spatial coexistence arises from complementary combinations of traits in each species rather than solely through self-limitation

Dosimetric Consequences of 3D Versus 4D PET/CT for Target Delineation of Lung Stereotactic Radiotherapy

Introduction:Lung tumor delineation is frequently performed using 3D positron emission tomography (PET)/computed tomography (CT), particularly in the radiotherapy treatment planning position, by generating an internal target volume (ITV) from the slow acquisition PET. We investigate the dosimetric consequences of stereotactic ablative body radiotherapy (SABR) planning on 3D PET/CT in comparison with gated (4D) PET/CT.Methods:In a prospective clinical trial, patients with lung metastases were prescribed 26 Gy single-fraction SABR to the covering isodose. Contemporaneous 3D PET/CT and 4D PET/CT was performed in the same patient position. An ITV was generated from each data set, with the planning target volume (PTV) being a 5-mm isotropic expansion. Dosimetric parameters from the SABR plan derived using the 3D volumes were evaluated against the same plan applied to 4D volumes.Results:Ten lung targets were evaluated. All 3D plans were successfully optimized to cover 99% of the PTV by the 26 Gy prescription. In all cases, the calculated dose delivered to the 4D target was less than the expected dose to the PTV based on 3D planning. Coverage of the 4D-PTV by the prescription isodose ranged from 74.48% to 98.58% (mean of 90.05%). The minimum dose to the 4D-ITV derived by the 3D treatment plan (mean = 93.11%) was significantly lower than the expected dose to ITV based on 3D PET/CT calculation (mean = 111.28%), p < 0.01. In all but one case, the planned prescription dose did not cover the 4D-PET/CT derived ITV.Conclusions:Target delineation using 3D PET/CT without additional respiratory compensation techniques results in significant target underdosing in the context of SABR