Grant A. Duffy

Size-dependent directed social learning in nine-spined sticklebacks

To forage efficiently in a patchy environment animals must make informed decisions concerning in which patches to forage, for which the behaviour of other animals often provides informative cues. However, other individuals may differ in the quality or relevance of information that they provide, and accordingly animals are expected to be selective with respect to whom they copy. Such selectivity may include the biasing of copying towards older, larger or more experienced conspecifics. We investigated whether the ability of nine-spined sticklebacks, Pungitius pungitius, to exploit public information, that is, to judge the relative profitability of food patches solely on the basis of the relative feeding activity of others, is influenced by their own body size and that of the individuals from whom they copy. Individual observer fish, classed as either small or large, were trained that two discrete foraging patches differed in their relative quality, one being rich and the other poor (‘personal information’). They then watched two shoals of either small or large demonstrator conspecifics feeding at the two patches (‘public information’), but with relative profitability of the patches reversed compared to training, before being given the opportunity to make a patch choice. The effectiveness of this public demonstration was clearly contingent on the size of the demonstrators, with subjects of both size classes copying the patch choice of large demonstrators significantly more than they copied the patch choice of small demonstrators. This study reinforces the view that animal social learning is directed along particular pathways, with individuals predisposed by selection to copy particular categories of individual differentially.

Microclimate-based macrophysiology: implications for insects in a warming world

Understanding the influence of microclimates is an increasing focus of investigations of global change risks to insects. Here we review recent advances in this area in the context of macrophysiological forecasts of the impacts of warming. Some studies have suggested that risk estimates may be inaccurate owing to microclimate variation or behavioural responses. Using modelled microclimatic data we illustrate this problem, demonstrating that soil microclimates on the Australian continent will warm in concert with global climate change such that the upper thermal tolerance limits of many insects will be exceeded across much of the continent. Deeper microclimates will be cooler and more hospitable, emphasising the importance of behavioural adaptation and movement amongst microclimates as a response to environmental warming.

Upper thermal tolerance in aquatic insects

•Owing to the characteristics of their contrasting habitats, aquatic and terrestrial insects will respond differently to global environmental change.•A synthesis of aquatic insect thermal tolerance studies identified a weak latitudinal pattern of upper thermal traits.•Average upper thermal tolerances of aquatic insects are generally lower than those of terrestrial species.•Immature life-stages have lower thermal tolerances than adults.•Geographic biases in aquatic insect physiological studies highlight the need for further experimental work.Given global climate change, much attention has been given to the extent to which upper thermal tolerance limits in terrestrial and marine metazoans might be constrained. A quantitative synthesis of the available information indicates that aquatic insects, and especially immature life stages, have a broader range of thermal tolerances, and a lower average thermal tolerance, than their terrestrial counterparts. The pronounced incidence of oxygen and capacity limitation of thermal tolerance in aquatic-dwelling stages and species is likely responsible for this pattern. A combination of high temperature and low water oxygen content is likely to be especially problematic for aquatic species. Maximum limits to upper thermal tolerance are similar among terrestrial and aquatic insects, verifying the generality of constrained upper thermal tolerances. These findings are, however, limited by the narrow geographic and taxonomic scope of assessments.

Growth and reproduction of laboratory-reared neanurid Collembola using a novel slime mould diet

Although significant progress has been made using insect taxa as model organisms, non-tracheated terrestrial arthropods, such as Collembola, are underrepresented as model species. This underrepresentation reflects the difficulty in maintaining populations of specialist Collembola species in the laboratory. Until now, no species from the family Neanuridae have been successfully reared. Here we use controlled growth experiments to provide explicit evidence that the species Neanura muscorum can be raised under laboratory conditions when its diet is supplemented with slime mould. Significant gains in growth were observed in Collembola given slime mould rather than a standard diet of algae-covered bark. These benefits are further highlighted by the reproductive success of the experimental group and persistence of laboratory breeding stocks of this species and others in the family. The necessity for slime mould in the diet is attributed to the ‘suctorial’ mouthpart morphology characteristic of the Neanuridae. Maintaining laboratory populations of neanurid Collembola species will facilitate their use as model organisms, paving the way for studies that will broaden the current understanding of the environmental physiology of arthropods.

Urban warming favours C4 plants in temperate European cities

Summary Elucidating the mechanisms responsible for the structure of urban communities is a key aim of urban ecology, but one that is often confounded by the multitude of environmental changes that are caused by urbanization. We applied trait-based techniques to identify the specific environmental drivers that shape urban plant assemblages and predict how these drivers will further impact biotas with increasing urbanization and global environmental change. Urbanized areas across temperate Europe have significantly higher abundance and richness of plants using the C4 photosynthetic pathway, relative to the total number and species richness of all plant records, than non-urban areas. Urban warming, mediated by the contrasting physiological responses of C3 and C4 plants to warming, is the main driver of observed patterns of plant assemblage structure. This mirrors broadscale and historical distribution patterns of C3 and C4 plants. The increased relative abundance of C4 plants in cities demonstrated here may be indicative of more geographically widespread assemblage changes to be expected in temperate environments under continuing global climate change. Synthesis. Applying a combined trait-based, ecoinformatic and remote-sensing approach provides new insight into the landscape-level consequences of urbanization. Specifically, we show that localized urban warming in cities across temperate Europe favours C4 plant species, which respond positively to increased temperatures. Urban plant assemblages are shaped by environmental warming and exhibit significant increases in C4 plant relative abundance compared to non-urban assemblages.

Basal resistance enhances warming tolerance of alien over indigenous species across latitude

Significance How climate change and biological invasions interact to affect biodiversity is of major concern to conservation. Quantitative evidence for the nature of climate change–invasion interactions is, however, limited. For the soil ecosystem fauna, such evidence is nonexistent. Yet across the globe, soil-dwelling animals regulate belowground functioning and have pronounced influences on aboveground dynamics. Using springtails as an exemplar taxon, widely known to have species-specific effects on below- and aboveground dynamics, we show that across a wide latitudinal span (16–54°S), alien species have greater ability to tolerate climate change-associated warming than do their indigenous counterparts. The consequences of such consistent differences are profound given globally significant invasions of soil systems by springtails. Soil systems are being increasingly exposed to the interactive effects of biological invasions and climate change, with rising temperatures expected to benefit alien over indigenous species. We assessed this expectation for an important soil-dwelling group, the springtails, by determining whether alien species show broader thermal tolerance limits and greater tolerance to climate warming than their indigenous counterparts. We found that, from the tropics to the sub-Antarctic, alien species have the broadest thermal tolerances and greatest tolerance to environmental warming. Both groups of species show little phenotypic plasticity or potential for evolutionary change in tolerance to high temperature. These trait differences between alien and indigenous species suggest that biological invasions will exacerbate the impacts of climate change on soil systems, with profound implications for terrestrial ecosystem functioning.

The veiled ecological danger of rising sea levels

As sea levels rise, human displacement and subsequent land-use change may be as ecologically significant as the direct impacts of climate change. New work suggesting that mean sea level will rise further and faster than previously thought calls attention to the importance of these indirect processes for ecology and conservation.

A comparative analysis of canyon and non-canyon populations of the deep-sea scavenging amphipod Paralicella caperesca

Existing population studies of deep-sea amphipods have focused on species that inhabit deep-sea vent or trench environments but few cosmopolitan species have been studied. Here we provide new insight into the life history and population ecology of the pan-oceanic scavenging amphipod Paralicella caperesca and discuss the influence of nutrient-rich submarine canyon environments on the growth and reproduction of this species. Data were collected through the dissection and measurement of 2997 P. caperesca from 14 samples taken from abyssal plains, continental slopes and submarine canyons in the North-East Atlantic. Sexual dimorphism was less pronounced than observed for other scavenging amphipod species but females were significantly larger and had shorter antennae than males. The size of oostegites in female P. caperesca varied considerably within size classes, ovaries contained a relatively large number of oocytes, and no empty ovaries were observed. These factors, in combination with absence of mature females, suggest that P. caperesca practices semelparity, a reproductive strategy that complements the feeding strategy of this obligate necrophage. Five male and seven female size-grouped cohorts were identified for P. caperesca. Cohorts from deep-sea submarine canyon populations showed consistently larger mean total body lengths than non-canyon cohorts. Individuals from canyon samples also expressed sexual characteristics at smaller sizes than non-canyon individuals. We hypothesize that these trends are indicative of nutrient-mediated growth, maturation, and reproduction in P. caperesca. The species is able to grow and reproduce relatively quickly in response to increased nutrient input in canyon environments and therefore dominates scavenging amphipod assemblages.

High resolution temperature data for ecological research and management on the Southern Ocean Islands

Southern Ocean Islands are globally significant conservation areas. Predicting how their terrestrial ecosystems will respond to current and forecast climate change is essential for their management and requires high-quality temperature data at fine spatial resolutions. Existing datasets are inadequate for this purpose. Remote-sensed land surface temperature (LST) observations, such as those collected by satellite-mounted spectroradiometers, can provide high-resolution, spatially-continuous data for isolated locations. These methods require a clear sightline to measure surface conditions, however, which can leave large data-gaps in temperature time series. Using a spatio-temporal gap-filling method applied to high-resolution (~1 km) LST observations for 20 Southern Ocean Islands, we compiled a complete monthly temperature dataset for a 15-year period (2001-2015). We validated results using in situ measurements of microclimate temperature. Gap-filled temperature observations described the thermal heterogeneity of the region better than existing climatology datasets, particularly for islands with steep elevational gradients and strong prevailing winds. This dataset will be especially useful for terrestrial ecologists, conservation biologists, and for developing island-specific management and mitigation strategies for environmental change.