Body Size and Weight of Pill Bugs (Armadillidium vulgare) Vary between Urban Green Space Habitats

Rapid urban development poses a threat to global biodiversity. At the same time, urban green spaces offer opportunities for holding biodiversity in cities. Among biological communities, the soil fauna plays a crucial role in ecological processes but is often ignored. Understanding the effects of environmental factors on soil fauna is critical for ecological conservation in urban areas. In this study, five typical green space habitats were selected including bamboo grove, forest, garden, grassland, and wasteland in spring, for detecting the relationship between habitats and Armadillidium vulgare population characteristics in Yancheng, China. Results indicate that soil water content, pH, soil organic matter, and soil total carbon varied significantly among habitats, as well as the body length and body weight of pill bugs. The higher proportion of larger pill bugs was found in the wasteland and the lower proportion in the grassland and the bamboo grove. The body length of pill bugs was positively related to pH. Soil total carbon, soil organic matter, and the number of plant species were correlated with the body weight of pill bugs.

Comparative exploratory movements of two terrestrial isopods (suborder: Oniscidea), in response to humidity and availability of food

Unfavourable conditions within familiar environments may prompt organisms to make forays into other habitats, at least temporarily. This behaviour is in turn linked to key demographic processes such as immigration, emigration, and eventually, metapopulation dynamics. How such movements are triggered by environmental conditions (much less their interaction effects) has rarely been experimentally tested. To address this, we examined how environmental conditions (3 levels of food and 3 levels of humidity) within a microcosm affect the movements of two species of isopods (Armadillidium vulgare and Porcellio scaber) out of their familiar habitat. We used web-camera checkpoints to record the movements of individually marked animals as they conducted forays along corridors that lead to new, unused habitats. Thirty-six trials were run in total for each species, with each trial involving 16 animals (8 ♂♂, 8 ♀♀). Relatively unfavourable conditions of low humidity, low food levels, and their interaction prompted changes to all the foray metrics we measured. However, different levels of mobility and tolerance to desiccation between the two species also appeared linked to the degree of responses, e.g., Porcellio demonstrated a greater tendency to depart from familiar habitat under low humidity, possibly due to their superior mobility and greater susceptibility to desiccation. This study improves our understanding of how different environmental conditions act in concert to affect the exploratory movements away from familiar habitat, and how these responses differ even for closely-related species.

Social environment shapes female settlement decisions in a solitary carnivore

How and where a female selects an area to settle and breed is of central importance in dispersal and population ecology as it governs range expansion and gene flow. Social structure and organization have been shown to influence settlement decisions, but its importance in the settlement of large, solitary mammals is largely unknown. We investigate how the identity of overlapping conspecifics on the landscape, acquired during the maternal care period, influences the selection of settlement home ranges in a non-territorial, solitary mammal using location data of 56 female brown bears (Ursus arctos). We used a resource selection function to determine whether females' settlement behavior was influenced by the presence of their mother, related females, familiar females, and female population density. Hunting may remove mothers and result in socio-spatial changes before settlement. We compared overlap between settling females and their mother's concurrent or most recent home ranges to examine the settling female's response to the absence or presence of her mother on the landscape. We found that females selected settlement home ranges that overlapped their mother's home range, familiar females, that is, those they had previously overlapped with, and areas with higher density than their natal ranges. However, they did not select areas overlapping related females. We also found that when mothers were removed from the landscape, female offspring selected settlement home ranges with greater overlap of their mother's range, compared with mothers who were alive. Our results suggest that females are acquiring and using information about their social environment when making settlement decisions.

Persistence and space preemption explain species-specific founder effects on the organization of marine sessile communities

Community assembly may not follow predictable successional stages, with a large fraction of the species pool constituted by potential pioneering species and successful founders defined through lottery. In such systems, priority effects may be relevant in the determination of trajectories of developing communities and hence diversity and assemblage structure at later advanced states. In order to assess how different founder species may trigger variable community trajectories and structures, we conducted an experimental study using subtidal sessile assemblages as model. We manipulated the identity of functionally different founders and initial colony size (a proxy of the time lag before the arrival of later species), and followed trajectories. We did not observe any effects of colony size on response variables, suggesting that priority effects take place even when the time lag between the establishment of pioneering species and late colonizers is very short. Late community structure at experimental panels that started either with the colonial ascidian Botrylloides nigrum, or the arborescent bryozoan Bugula neritina, was similar to control panels allowed natural assembling. In spite of high potential for fast space domination, and hence negative priority effects, B. nigrum suffered high mortality and did not persist throughout succession. Bugula neritina provided complex physical microhabitats through conspecific clustering that have enhanced larval settlement of late species arrivals, but no apparent facilitation was observed. Differently, panels founded by the encrusting bryozoan Schizoporella errata led to different and less diverse communities compared to naturally assembled panels, evidencing strong negative priority effects through higher persistence and space preemption. Schizoporella errata founder colonies inhibited further conspecific settlement, which may greatly relax intraspecific competition, allowing resource allocation to colony growth and space domination, thus reducing the chances for the establishment of other species.