Identifying indicator species of elevation: Comparing the utility of woody plants,ants and moths for long‐term monitoring

Ecologists have found the distributions of many groups of organisms to be elevationally stratified. Consequently, various taxa (or species) have been proposed as indicators for inclusion within long‐term monitoring programmes to quantify the ecological impacts of future climatic change. Ideal indicators should be restricted to a particular elevational range (i.e. have high specificity) and be readily detectable across space and time (i.e. have high fidelity). This, however, has not been rigorously tested for elevational studies. We employed a spatially and temporally replicated sampling design to test the utility of tree, ant, and canopy and understorey moth species as indicators of elevation within continuous subtropical rainforest of eastern Australia. Using the classical indicator value protocol, we tested (i) whether the number of indicator species (all taxa) found in the observed data was significantly greater than the number obtained by chance; (ii) whether the indicator species (ants and moths) identified from one sampling season responded to elevation in a similar way in samples obtained from other seasons; and (iii) whether the indicator species (ants) identified from one elevational transect responded to elevation in a similar way in a nearby transect that incorporated similar elevational ranges. All groups had significantly greater numbers of indicator species than expected by chance. Temporal fidelity of moth indicator species was lower than that of ants as the suite of moth indicator species showed high seasonal variation. In contrast, ants showed high spatial and temporal fidelity. Most ant indicator species were, however, indicative of low and mid‐elevations, and only one species was indicative of the highest elevation, suggesting their relatively low conservation significance in relation to climate warming in this region. It is essential that we understand how spatial and temporal variation affects the distributions of different taxonomic groups when incorporating multiple taxa for long‐term monitoring programmes.     

Altitudinal patterns of moth diversity in tropical and subtropical Australian rainforests

Altitudinal gradients are an excellent study tool to help understand the mechanisms shaping community assembly. We established a series of altitudinal gradients along the east coast of Australia to describe how the distribution of a hyper‐diverse herbivore group (night‐flying Lepidoptera) changes across an environmental gradient in subtropical and tropical rainforests. Two transects were in subtropical rainforest in the same bioregion, one in south‐east Queensland (28.7°S) and one in north east New South Wales (29.7°S). Two were in tropical rainforest, one in mid‐east Queensland (21.1°S) and one in the Wet Tropics of northern Queensland (17.5°S). Replicate plots were established in altitudinal bands separated by 200 m. Canopy and understorey moths were sampled at the beginning and end of the wet season using automatic Pennsylvania light traps. We sorted a total of 93 400 individuals, belonging to 3035 species. The two subtropical transects in the same region showed similar patterns of turnover across altitude, with the most distinctive assemblage occurring at the highest altitude. Moth assemblages in the tropical transects tended to show distinct ‘lowland’ and ‘upland’ communities. For species that were common across several of the transects, many were found at lower altitudes in the subtropics and higher altitudes in the tropics, suggesting they are sensitive to environmental conditions, and track their physiological envelopes across latitudes. These results suggest ubiquitous altitudinal stratification in tropical and subtropical Australian rainforests. The marked response of species to latitude and altitude demonstrates they are sensitive to climatic variables and can be used as indicators to understand future community responses to climate change.     

Effects of helium and other inert gases on Echinosphaerium nucleofilium (protozoa, heliozoa).

The effects of helium, nitrogen, argon and krypton on Echinosphaerium nucleofilum (Heliozoa) have been studied at partial pressures of 10-130 atm. Additional experiments have been carried out with hydrostatic pressure alone. Helium causes shortening of the axopods over the whole range of pressures, and damage to the cell body at pressures of 60-90 atm, both with a maximum at 80 atm. These effects cannot be explained in terms of hydrostatic pressure alone; a 'pressure reversal' effect may be operating, causing the peak at 80 atm. Nitrogen also causes both cell damage and axopod shortening, the severity increasing with increasing pressure. Argon and krypton cause cell damage but no shortening. The order of potency for cell damage is krypton greater than argon greater than nitrogen greater than helium. It is suggested that there may be tuo sites of action, possibly the microtubules (for axopod shortening) and the cell membrane (for cell damage). In appropriate mixtures of helium and argon, both the cell damage usually caused by argon, and the axopod shortening usually caused by helium, are prevented. Possible mechanisms include the effects of hydrostatic pressure on gas solubility coefficients, reversal of the effects of the gases by the increase in total pressure, and competition for sites of action.     

Central place foraging in larvae of the charaxine butterfly,Polyura pyrrhus (L.): A case study in a herbivore

Central place foraging by larvae of the charaxine butterfly,Polyura pyrrhus, was studied. Larvae made foraging trips from the silken pads they constructed on leaflets of their foodplant,Acacia sp. A foraging trip sometimes involved complete depletion of a single patch of foodplant pinnules. Larvae which did not deplete a patch appeared to eat until they were satiated, whereas larvae which depleted a patch either visited another patch (multiple-patch foraging) or returned directly to the pad (single-patch foraging). If the food intake at the first patch was small a larva tended to make a “multiple-patch” decision, especially when the pinnule-patch was distant from the resting pad. The duration between successive foraging trips (resting time on the pad) was much longer than the round trip duration: on average about 3 h and 15 min, respectively. The resting time is suggested to be a handling time (i.e., digesting food in the gut) and was disproportional to the amount of food consumed, i.e., the handling efficiency was higher when the larva consumed a larger amount of food. This may be the reason why larvae usually ate until they were satiated. A food-intake-rate maximizing model was constructed to describe the decision rule as to whether a larva should make a single-patch or a multiple-patch foraging trip. One of the model's predictions (i.e., larvae should engage in multiple-patch foraging when the food intake at the first patch is small) qualitatively corresponds with data, however, the model does not explain the effect of travelling time on decision making in larvae. Several other factors which may influence the decision making of larvae are discussed.