Myuchelys bellii (Bell's turtle). Unexpected dietary contents.
Freshwater turtles are typically omnivores and dietary generalists and fill important niches as aquatic grazers and scavengers. Some species prefer plant material over animal, or vice versa, but in general, freshwater turtle species will take advantage of all available food sources. The natural diets of a species can be dcoumented by directly observing feeding, examining feces, and by flushing the stomachs of captured individuals. Stomach flushing provides more intact samples than feces, and is logistically more feasible than observing foraging behavior, but is also more invasive than these other methods (Legler 1977. Herpetologica 33:281-284).
A trait-based framework for dung beetle functional ecology
Traits are key for understanding the environmental responses and ecological roles of organisms. Trait approaches to functional ecology are well established for plants, whereas consistent frameworks for animal groups are less developed. Here we suggest a framework for the study of the functional ecology of animals from a trait-based response–effect approach, using dung beetles as model system. Dung beetles are a key group of decomposers that are important for many ecosystem processes. The lack of a trait-based framework tailored to this group has limited the use of traits in dung beetle functional ecology. We review which dung beetle traits respond to the environment and affect ecosystem processes, covering the wide range of spatial, temporal and biological scales at which they are involved. Dung beetles show trait-based responses to variation in temperature, water, soil properties, trophic resources, light, vegetation structure, competition, predation and parasitism. Dung beetles' influence on ecosystem processes includes trait-mediated effects on nutrient cycling, bioturbation, plant growth, seed dispersal, other dung-based organisms and parasite transmission, as well as some cases of pollination and predation. We identify 66 dung beetle traits that are either response or effect traits, or both, pertaining to six main categories: morphology, feeding, reproduction, physiology, activity and movement. Several traits pertain to more than one category, in particular dung relocation behaviour during nesting or feeding. We also identify 136 trait–response and 77 trait–effect relationships in dung beetles. No response to environmental stressors nor effect over ecological processes were related with traits of a single category. This highlights the interrelationship between the traits shaping body-plans, the multi-functionality of traits, and their role linking responses to the environment and effects on the ecosystem. Despite current developments in dung beetle functional ecology, many knowledge gaps remain, and there are biases towards certain traits, functions, taxonomic groups and regions. Our framework provides the foundations for the thorough development of trait-based dung beetle ecology. It also serves as an example framework for other taxa.
The importance of species interactions in eco-evolutionary community dynamics under climate change
Eco-evolutionary dynamics are essential in shaping the biological response of communities to ongoing climate change. Here we develop a spatially explicit eco-evolutionary framework which features more detailed species interactions, integrating evolution and dispersal. We include species interactions within and between trophic levels, and additionally, we incorporate the feature that species' interspecific competition might change due to increasing temperatures and affect the impact of climate change on ecological communities. Our modeling framework captures previously reported ecological responses to climate change, and also reveals two key results. First, interactions between trophic levels as well as temperature-dependent competition within a trophic level mitigate the negative impact of climate change on biodiversity, emphasizing the importance of understanding biotic interactions in shaping climate change impact. Second, our trait-based perspective reveals a strong positive relationship between the within-community variation in preferred temperatures and the capacity to respond to climate change. Temperature-dependent competition consistently results both in higher trait variation and more responsive communities to altered climatic conditions. Our study demonstrates the importance of species interactions in an ecoevolutionary setting, further expanding our knowledge of the interplay between ecological and evolutionary processes.
The susceptibility of species to extinctions in model communities
Despite the fact that the loss of a species from a community has the potential to cause a dramatic decline in biodiversity, for example through cascades of secondary extinctions, little is known about the factors contributing to the extinction risk of any particular species. Here we expand earlier modeling approaches using a dynamic food-web model that accounts for bottom-up as well as top-down effects. We investigate what factors influence a species' extinction risk and time to extinction of the non-persistent species.
We identified three basic properties that affect a species' risk of extinction. The highest extinction risk is born by species with (1) low energy input (e.g. high trophic level), (2) susceptibility to the loss of energy pathways (e.g. specialists with few prey species) and (3) dynamic instability (e.g. low Hill exponent and reliance on homogeneous energy channels when feeding on similarly sized prey).
Interestingly, and different from field studies, we found that the trophic level and not the body mass of a species influences its extinction risk. On the other hand, body mass is the single most important factor determining the time to extinction of a species, resulting in small species dying first. This suggests that in the field the trophic level might have more influence on the extinction risk than presently recognized.
Beyond body size—new traits for new heights in trait-based modelling of predator-prey dynamics
Food webs map feeding interactions among species, providing a valuable tool for understanding and predicting community dynamics. Using species' body sizes is a promising avenue for parameterizing food-web models, but such approaches have not yet been able to fully recover observed community dynamics. Such discrepancies suggest that traits other than body size also play important roles. For example, differences in species' use of microhabitat or non-consumptive effects of intraguild predators may affect dynamics in ways not captured by body size. In Laubmeier et al. (2018), we developed a dynamic food-web model incorporating microhabitat and non-consumptive predator effects in addition to body size, and used simulations to suggest an optimal sampling design of a mesocosm experiment to test the model. Here, we perform the mesocosm experiment to generate empirical time-series of insect herbivore and predator abundance dynamics. We minimize least squares error between the model and time-series to determine parameter values of four alternative models, which differ in terms of including vs excluding microhabitat use and non-consumptive predator-predator effects. We use both statistical and expert-knowledge criteria to compare the models and find including both microhabitat use and non-consumptive predator-predator effects best explains observed aphid and predator population dynamics, followed by the model including microhabitat alone. This ranking suggests that microhabitat plays a larger role in driving population dynamics than non-consumptive predator-predator effects, although both are clearly important. Our results illustrate the importance of additional traits alongside body size in driving trophic interactions. They also point to the need to consider trophic interactions and population dynamics in a wider community context, where non-trophic impacts can dramatically modify the interplay between multiple predators and prey. Overall, we demonstrate the potential for utilizing traits beyond body size to improve trait-based models and the value of iterative cycling between theory, data and experiment to hone current insights into how traits affect food-web dynamics.
The association of Ned Kelly tattoos with suicide and homicide in a forensic context—a confirmatory prospective study
Ned Kelly, an iconic fgure in contemporary Australian mythology, was a bushranger (outlaw) who was executed in 1880 for the murder of a serving police ofcer, Constable Thomas Lonigan. Kelly is often commemorated by tattoos which depict his armour and helmet or his alleged last words of "Such is life". A study was undertaken from January 1, 2011, to December 31, 2020, at Forensic Science SA, Adelaide, South Australia, of all cases with such tattoos. De-identifed case details included the year of death, age, sex and cause and manner of death. There were 38 cases consisting of 10 natural deaths (26.3%) and 28 unnatural (73.7%). The latter included 15 cases of suicide (39.5%), 9 accidents (23.7%) and 4 homicides (10.5%). Of the 19 suicides and homicides, there were 19 males and no females (age range 24–57 years" average 44 years). The number of suicides in the general South Australian forensic autopsy population in 2020 was 216/1492 (14.5%) which was signifcantly lower than in the study population in which 39.5% of cases were suicides (2.7 times higher" p<0.001). A similar trend occurred for homicides which accounted for 17/1492 in the general forensic autopsy population (1.1%), signifcantly lower than in the study population which had 10.5% homicides (approximately 9.5 times higher" p<0.001). Thus, in the select population referred for medicolegal autopsy, there appears no doubt that Ned Kelly tattoos are associated with suicides and homicides. While this is not a population-based study, it may provide useful information for forensic practitioners dealing with such cases.