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Social structure is a fundamental component of a population that drives ecological and evolutionary processes ranging from parasite transmission to sexual selection. Nevertheless, we have much to learn about factors that explain variation in social structure. We used advances in biologging and social network analysis to experimentally test how the local habitat, and specifically habitat complexity, modulates social structure at different levels in wild populations. Sleepy lizards, Tiliqua rugosa, establish nonrandom social networks that are characterized by avoidance of some neighbours and frequent interactions with one opposite-sex individual. Using synchronous GPS locations of all adult lizards, we constructed social networks based on spatial proximity of individuals. We increased habitat structural complexity in two study populations by adding 100 short fences across the landscape. We then compared the resulting movement behaviour and social structure between these populations and two unmanipulated populations. Social connectivity (network density) and social stability, measured at weekly intervals, were greater in populations with increased habitat structural complexity. The level of agonistic interaction (quantified as scale damage) was also higher, indicating a fitness cost of greater social connectivity. However, some network parameters were unaffected by increased complexity, including disassortative mixing by sex, and at the individual level, social differentiation among associates (coefficient of variation of edge weights) and maximal interaction frequencies (maximal edge weight). This suggests divergent effects of changed ecological conditions on individual association behaviour compared to the resulting social structure of the population. Our results contrast with those from studies of more gregarious species, in which higher structural complexity in the environment relaxed the social connectivity. This shows that the response to altered ecological conditions can differ fundamentally between species or between populations, and we suggest that it depends on their tendency for gregarious behaviour.

Understanding space use remains a major challenge for animal ecology, with implications for species interactions, disease spread, and conservation. Behavioural type (BT) may shape the space use of individuals within animal populations. Bolder or more aggressive individuals tend to be more exploratory and disperse further. Yet, to date we have limited knowledge on how space use other than dispersal depends on BT. To address this question we studied BT-dependent space-use patterns of sleepy lizards (Tiliqua rugosa) in southern Australia. We combined high-resolution global positioning system (GPS) tracking of 72 free-ranging lizards with repeated behavioural assays, and with a survey of the spatial distributions of their food and refuge resources. Bayesian generalized linear mixed models (GLMM) showed that lizards responded to the spatial distribution of resources at the neighbourhood scale and to the intensity of space use by other conspecifics (showing apparent conspecific avoidance). BT (especially aggressiveness) affected space use by lizards and their response to ecological and social factors, in a seasonally dependent manner. Many of these effects and interactions were stronger later in the season when food became scarce and environmental conditions got tougher. For example, refuge and food availability became more important later in the season and unaggressive lizards were more responsive to these predictors. These findings highlight a commonly overlooked source of heterogeneity in animal space use and improve our mechanistic understanding of processes leading to behaviourally driven disease dynamics and social structure.

Movement is often used to indicate host vigour, as it has various ecological and evolutionary implications, and has been shown to be affected by parasites. We investigate the relationship between tick load and movement in the Australian Sleepy Lizard (Tiliqua rugosa (Gray, 1825)) using high resolution GPS tracking. This allowed us to track individuals across the entire activity season. We hypothesized that tick load negatively affects host movement (mean distance moved per day). We used a multivariate statistical model informed by the ecology and biology of the host and parasite, their host--parasite relationship, and known host movement patterns. This allowed us to quantify the effects of ticks on lizard movement above and beyond effects of other factors such as time in the activity season, lizard body condition, and stress. We did not find any support for our hypothesis. Instead, our results provide evidence that lizard movement is strongly driven by internal state (sex and body condition independent of tick load) and by external factors (environmental conditions). We suggest that the Sleepy Lizard has largely adapted to natural levels of tick infection in this system. Our results conform to host--parasite arms race theory, which predicts varying impacts of parasites on hosts in natural systems.Key words: reptile, body-mass index, movement ecology, parasite, GPS tracking, host--parasite interaction, spatial behaviour, Sleepy Lizard, Tiliqua rugosa.Les deplacements sont souvent utilises pour inferer la vigueur des hotes, puisqu'ils temoignent de differentes manieres de l'ecologie et de l'evolution et qu'il a ete demontre qu'ils sont influences par les parasites. Nous examinons la relation entre la charge de tiques et les deplacements chez le scinque rugueux (Tiliqua rugosa (Gray, 1825)) en utilisant le reperage par GPS de haute resolution, qui permet de suivre des individus durant toute la periode d'activite. Nous avons postule que la charge de tiques a une incidence negative sur les deplacements des hotes (distance de deplacement moyenne par jour). Nous utilisons un modele statistique multi-variable integrant de l'information sur l'ecologie et la biologie de l'hote et du parasite, leur relation hote--parasite et les motifs de deplacement connus de l'hote. Cela nous permet de quantifier les effets des tiques sur les deplacements des scinques en excluant les effets d'autres facteurs comme le moment de la periode d'activite, l'embonpoint des scinques et le stress. Les resultats ne supportent aucunement notre hypothese. Ils indiquent plutot que les deplacements des scinques sont fortement modules par l'etat interne (sexe et embonpoint independants de la charge de tiques) et des facteurs externes (conditions ambiantes). Nous proposons que le scinque rugueux s'est en bonne partie adapte aux niveaux naturels d'infection de tiques dans ce systeme. Nos resultats sont conformes a la theorie de la course aux armements entre hote et parasite, qui predit des impacts variables des parasites sur les hotes dans des systemes naturels. [Traduit par la Redaction]Mots-cles: reptile, indice de masse corporelle, ecologie des deplacements, parasite, reperage par GPS, interaction hote-parasite, comportement spatial, scinquea rugueux, Tiliqua rugosa., IntroductionParasites, by definition, gain their energy resources from their hosts, which negatively impacts the host's health and vigour (Beyer and Grossman 1997; Fenner and Bull 2008). Such impacts in host--parasite [...]

In the fairly modest temperature and pressure regime of 0–2 GPa and 200–295 K, 2,2,2-trifluoroethanol (TFE) exhibits a remarkable degree of polymorphism, with the observation of four ordered phases (forms 1–4) and a cubic plastic phase (form 5). The ordered phases are characterised by hydrogen-bonded chains, with the crystal structures of the three high-pressure forms (forms 2, 3 and 4) based on the same hydrogen-bonded catemeric motif. The structures and relationships between these phases were determined using a combination of high-pressure single-crystal X-ray diffraction, at ambient temperature, and a series of high-pressure neutron powder-diffraction experiments to ∼6 GPa at 295 K, 245 K and 200 K. As well as allowing the determination of the relative compressibilities of the phases, the neutron powder-diffraction studies also provided a preliminary mapping of the surprisingly rich phase diagram of TFE. [ABSTRACT FROM AUTHOR]

Uniform plots of broccoli raab (Brassica rapa subsp. rapa) seedlings were inoculated with a rifampicin-resistant strain of Pseudomonas syringae pv. alisalensis, the causal agent of bacterial blight on crucifers. resulting in 100% disease incidence in mature plants. Diseased plants were incorporated into the soil at maturity and smaller replicated plots were replanted at various times after incorporation. Rifampicin-resistant fluorescent pseudomonads with rep-PCR profiles identical to P. syringae pv. alisalensis were isolated from lesions on plants grown in soil into which the first diseased crop was incorporated. Disease incidence declined in mature plants as the length of time between incorporation of the first planting and seeding of the replanted plots increased. Bacterial population levels in soil decreased over time and bacteria were no longer detectable 3 weeks after incorporation of the diseased crop. In laboratory tests, population levels of P. syringae pv. alisalensis decreased in untreated soil but not in autoclaved soil. Greenhouse studies demonstrated a direct correlation between population levels of P. syringae pv. alisatensis applied to soil and disease incidence in seedlings. However, the decline in bacterial populations in field soils did not wholly account for the decline in disease incidence with subsequent plantings.

The nuclear and magnetic structure of PrCrO3 has been investigated using neutron and X-ray powder diffraction as a function of pressure and temperature. The orthorhombic symmetry (space group Pbnm) remains stable up to the highest temperature (1500 K) and pressure (approx. 6 GPa) considered. There is a crossover in the magnitude of the a- and b-lattice parameters at approximately 1135 K, caused by competing effects of octahedral tilting and distortion. The material is antiferromagnetic (TN≈240 K) with Pb′n′m symmetry, with a maximum moment of 2.34(2)μb on the Cr3+ sites aligned along the direction of the a -axis. The application of pressure shows an abnormal softening in the unit-cell volume, which is suggestive of a continuous approach to a second-order phase transition. Raman spectroscopy measurements at ambient temperature were collected as a function of pressure up to approximately 12 GPa, with discontinuous mode behaviour further suggesting the existence of a transition above 7 GPa. The measured structural changes in PrCrO3 are compared extensively in the wider context of other lanthanide orthochromites, and the comparative effects of A- and B-site substitution on the polyhedral tilts and distortion are discussed. This article is part of the theme issue 'Exploring the length scales, timescales and chemistry of challenging materials (Part 1)'. [ABSTRACT FROM AUTHOR]