Cannibalism in the Brown Marmorated Stink Bug Halyomorpha halys (Stål)

The phytophagous brown marmorated stink bug Halyomorpha halys (Stål) is known to exhibit cannibalistic behaviour towards eggs. Here, we provide evidence of cannibalism among overwintering H. halys adults. Since diapausing individuals have high physiological demands for surviving long periods under stressful conditions, including the risk of depletion of metabolic reserves and desiccation, we assumed that nutritional and water requirements can be met by intraspecific predation. The role of aggregative behaviour in promoting cannibalism is also discussed. Given its evolutionary advantage, this trait should be maintained over generations and may be more widespread than previously considered in species that display aggregative behaviour during adverse seasons.

Aggregations and associations in deep-sea chondrichthyans

Group living has been recorded across a diverse range of chondrichthyans, but due to a variety of factors, any inferences of social associations in deep-sea cartilaginous fishes have yet to be described. Using a companion preference analysis, aggregating behaviour and associations in deep-sea chondrichthyans (four holocephalans, ten elasmobranchs) were evaluated across class and group size from long-term archived fisheries independent research trawl survey datasets. Results indicated that not all selected species engaged in aggregative behaviour, but those that did suggested patterns of sex- and size-specific associations, which varied with catch density. Adult females were caught most frequently in low densities, and were highly associated with other adult females. Adult males were consistently associated with each other. The nature of associations has important implications for selective mortality by spatial or temporally stratified, or aggregation-targeting, fisheries.

The semi-aquatic pondweed bugs of a Cretaceous swamp

Pondweed bugs (Hemiptera: Mesoveliidae), considered a sister group to all other Gerromorpha, are exceedingly rare as fossils. Therefore, each new discovery of a fossil mesoveliid is of high interest, giving new insight into their early evolutionary history and diversity and enabling the testing of their proposed relationships. Here, we report the discovery of new mesoveliid material from Spanish Lower Cretaceous (Albian) amber, which is the first such find in Spanish amber. To date, fossil records of this family only include one species from French Kimmeridgian as compression fossils, two species in French amber (Albian-Cenomanian boundary), and one in Dominican amber (Miocene). The discovery of two males and one female described and figured asGlaesivelia pulcherrimaSánchez-García & Solórzano Kraemer gen. et sp. n., and a single female described and figured asIberovelia quisquiliaSánchez-García & Nel, gen. et sp. n., reveals novel combinations of traits related to some genera currently in the subfamily Mesoveliinae. Brief comments about challenges facing the study of fossil mesoveliids are provided, showing the necessity for a revision of the existing phylogenetic hypotheses. Some of the specimens were studied using infrared microscopy, a promising alternative to the systematic study of organisms preserved in amber that cannot be clearly visualised. The new taxa significantly expand the fossil record of the family and shed new light on its palaeoecology. The fossils indicate that Mesoveliidae were certainly diverse by the Cretaceous and that numerous tiny cryptic species living in humid terrestrial to marginal aquatic habitats remain to be discovered. Furthermore, the finding of several specimens as syninclusions suggests aggregative behaviour, thereby representing the earliest documented evidence of such ethology.

Microconchid tubeworms (Class Tentaculita) from the Joggins Formation (Pennsylvanian), Nova Scotia, Canada

Microconchids have been described from the classic Pennsylvanian locality at Joggins, Nova Scotia. These encrusting tentaculitoid tubeworms have previously been mentioned and described from Joggins under the polychaete genus Spirorbis. Detailed morphological and microstructural investigation revealed that they belong to the species Microconchus carbonarius Murchison, confirming the previous tentative assignment (as Spirorbis carbonarius) made by Sir J. William Dawson in the nineteenth century. The occurrence of the same species in Upper Carboniferous deposits of England provides evidence supporting a connection between England and Nova Scotia in the Late Carboniferous (Pennsylvanian). Migration of the species could have been possible via brackish seas connecting both areas during maximum sea level during the Pennsylvanian. The species inhabited retrograding poorly drained coastal plain and open-water brackish environments, encrusting bivalve shells and plant remains in both sandstone and limestone deposits. Their high density (up to 19 individuals/cm2) may have resulted from their aggregative behaviour, high fecundity, and a lack of any competition with other skeleton-bearing encrusters. The large number (34%) of regenerated tubes indicates that microconchids were often preyed upon by associated animals, most probably fishes, which could graze on their dense encrusting aggregations.

Cooperate or compete? Influence of sex and body size on sheltering behaviour in the wall lizard, Podarcis muralis

Reptile sheltering behaviour, despite profound life history ramifications, remains poorly investigated. Whether or not individuals share a suitable shelter or, conversely, exclude conspecifics may depend on associated costs (resource partitioning, sexual harassment, disease or parasite contamination) and benefits (predation risk dilution, thermal resilience, information sharing). We performed two experiments on field caught wall lizards (Podarcis muralis), a highly territorial species, to investigate the relative roles of sex and body size in night sheltering. In the first experiment, random pairs of lizards were offered two identical shelters. Lizards either shared a shelter, or sheltered separately. In the second experiment, different random pairs of lizards were offered only one shelter so as to elicit a share or compete response. Body size and sex both appeared as significant drivers for sheltering patterns. Unexpectedly, wall lizards often chose to share shelters. When only one shelter (too small to accommodate two adult lizards) was available, many lizards rejected the sheltering option in preference for aggregation. Such aggregative behaviour was not sex dependant, and may reflect thermoregulatory or anti-predatory benefits. Our results nevertheless suggest that cooperative behaviour may exist in wall lizards.

Asymmetric reproductive character displacement in male aggregation behaviour

Reproductive character displacement—the evolution of traits that minimize reproductive interactions between species—can promote striking divergence in male signals or female mate preferences between populations that do and do not occur with heterospecifics. However, reproductive character displacement can affect other aspects of mating behaviour. Indeed, avoidance of heterospecific interactions might contribute to spatial (or temporal) aggregation of conspecifics. We examined this possibility in two species of hybridizing spadefoot toad (genus Spea ). We found that in Spea bombifrons sympatric males were more likely than allopatric males to associate with calling males. Moreover, contrary to allopatric males, sympatric S. bombifrons males preferentially associated with conspecific male calls. By contrast, Spea multiplicata showed no differences between sympatry and allopatry in likelihood to associate with calling males. Further, sympatric and allopatric males did not differ in preference for conspecifics. However, allopatric S. multiplicata were more variable than sympatric males in their responses. Thus, in S. multiplicata , character displacement may have refined pre-existing aggregation behaviour. Our results suggest that heterospecific interactions can foster aggregative behaviour that might ultimately contribute to clustering of conspecifics. Such clustering can generate spatial or temporal segregation of reproductive activities among species and ultimately promote reproductive isolation.

Markov chain model of phytoplankton dynamics

Markov chain model of phytoplankton dynamicsA discrete-time stochastic spatial model of plankton dynamics is given. We focus on aggregative behaviour of plankton cells. Our aim is to show the convergence of a microscopic, stochastic model to a macroscopic one, given by an evolution equation. Some numerical simulations are also presented.