Host selection in phytophagous insects: a new explanation for learning in adults

Insect learning can change the preferences an egg laying female displays towards different host plant species. Current hypotheses propose that learning may be advantageous in adult host selection behaviour through improved recognition, accuracy or selectivity in foraging. In this paper, we present a hypothesis for when learning can be advantageous without such improvements in adult host foraging. Specifically, that learning can be an advantageous strategy for egg laying females when larvae must feed on more than one plant in order to complete development, if the fitness of larvae is reduced when they switch to a different host species. Here, larvae benefit from developing on the most abundant host species, which is the most likely choice of host for an adult insect which increases its preference for a host species through learning. The hypothesis is formalised with a mathematical model and we provide evidence from studies on the behavioural ecology, of a number of insect species which demonstrate that the assumptions of this hypothesis may frequently be fulfilled in nature. We discuss how multiple mechanisms may convey advantages in insect learning and that benefits to larval development, which have so far been overlooked, should be considered in explanations for the widespread occurrence of learning.

Effectiveness of introduced biocontrol insects on the weed Parthenium hysterophorus (Asteraceae) in Australia

Six species of insects and a rust fungus have been successfully established for biocontrol of the weed Parthenicum hysterophorus L. in Queensland, Australia. Effectiveness of biocontrol insects was evaluated at two properties in Queensland during 1996-97 based on an exclusion experiment using insecticides. Parthenium-infested plots with and without biocontrol insects were sampled at monthly intervals and the impact of biocontrol insects on parthenium at individual plant and whole population levels monitored. Biocontrol insects were more effective at Mt Panorama (central Queensland) than at Plain Creek (north Queensland). At Mt Panorama, the leaf-feeding beetle Zygogramma bicolorata Pallister caused 96% defoliation and the stem-galling moth Epiblema strenuana Walker affected 100% of the plants, resulting in reductions of 90% in weed density, 40% in plant height, and 82% in flower production. Exclusion of biocontrol insects resulted in a 52% increase in seedling emergence and a seven-fold increase in the soil seed bank in the following season. At Plain Creek, E. strenuana was the only prominent agent. It affected 92% of the plants and prevented 32% of plants from producing any flowers, reduced plant height by 40% and flower production by 49%, but did not reduce the plant biomass, weed density or soil seed bank. However, exclusion of biocontrol insects resulted in an eight-fold increase in the soil seed bank in the following season.

Habitat complexity, spatial interference, and "minimum risk distribution": a framework for population stability

In the past century, the debate over whether or not density-dependent factors regulate populations has generally focused on changes in mean population density, ignoring the spatial variance around the mean as unimportant noise. In an attempt to provide a different framework for understanding population dynamics based on individual fitness, this paper discusses the crucial role of spatial variability itself on the stability of insect populations. The advantages of this method are the following: (1) it is founded on evolutionary principles rather than post hoc assumptions; (2) it erects hypotheses that can be tested; and (3) it links disparate ecological schools, including spatial dynamics, behavioral ecology, preference-performance, and plant apparency into an overall framework. At the core of this framework, habitat complexity governs insect spatial variance. which in turn determines population stability. First, the minimum risk distribution (MRD) is defined as the spatial distribution of individuals that results in the minimum number of premature deaths in a population given the distribution of mortality risk in the habitat (and, therefore, leading to maximized population growth). The greater the divergence of actual spatial patterns of individuals from the MRD, the greater the reduction of population growth and size from high, unstable levels. Then, based on extensive data from 29 populations of the processionary caterpillar, Ochrogaster lunifer, four steps are used to test the effect of habitat interference on population growth rates. (1) The costs (increasing the risk of scramble competition) and benefits (decreasing the risk of inverse density-dependent predation) of egg and larval aggregation are quantified. (2) These costs and benefits, along with the distribution of resources, are used to construct the MRD for each habitat. (3) The MRD is used as a benchmark against which the actual spatial pattern of individuals is compared. The degree of divergence of the actual spatial pattern from the MRD is quantified for each of the 29 habitats. (4) Finally, indices of habitat complexity are used to provide highly accurate predictions of spatial divergence from the MRD, showing that habitat interference reduces population growth rates from high, unstable levels. The reason for the divergence appears to be that high levels of background vegetation (vegetation other than host plants) interfere with female host-searching behavior. This leads to a spatial distribution of egg batches with high mortality risk, and therefore lower population growth. Knowledge of the MRD in other species should be a highly effective means of predicting trends in population dynamics. Species with high divergence between their actual spatial distribution and their MRD may display relatively stable dynamics at low population levels. In contrast, species with low divergence should experience high levels of intragenerational population growth leading to frequent habitat-wide outbreaks and unstable dynamics in the long term. Six hypotheses, erected under the framework of spatial interference, are discussed, and future tests are suggested.

Cytological basis of photoresponsive behavior in a sponge larva

Ontogenetic changes in the photoresponse of larvae from the demosponge Reneira sp. were studied by analyzing the swimming paths of individual larvae exposed to diffuse white light. Larvae swam upward upon release from the adult, but were negatively phototactic until at least 12 hours after release. The larval photoreceptors are presumed to be a posterior ring of columnar monociliated epithelial cells that possess 120-mum-long cilia and pigment-filled protrusions. A sudden increase in light intensity caused these cilia to become rigidly straight. If the light intensity remained high, the cilia gradually bent over the pigmented vesicles in the adjacent cytoplasm, and thus covered one entire pole of the larva. The response was reversed upon a sudden decrease in light intensity. The ciliated cells were sensitive to changes in light intensity in larvae of all ages. This response is similar to the shadow response in tunicate larvae or the shading of the photoreceptor in Euglena and is postulated to allow the larvae to steer away from brighter light to darker areas, such as under coral rubble-the preferred site of the adult sponge on the reef flat. In the absence of a coordinating system in cellular sponges, the spatial organization and autonomous behavior of the pigmented posterior cells control the rapid responses to light shown by these larvae.

Patterns and levels of endemism in the Australian Wet Tropics rainforest: evidence from flightless insects

This study examines the level and pattern of endemism among 274 flightless rainforest insects found in the Wet Tropics region of Australia. Endemism is measured at two nested scales: (1) those confined to the Wet Tropics, termed 'regional endemics'; and (2) the subset of those species confined to a single subregion of the Wet Tropics, termed 'subregional endemics'. Fifty per cent of the regional endemic flightless insects are also subregional endemics compared with 15% of the known regional endemic vertebrates. The four subregions with the most endemic flightless insect species are the uplands of Mt Finnigan, Carbine, Bellenden-Ker/Bartle Frere and Atherton. Multiple regression suggests that the combination of rainforest area and shape explain the most variance (R-2 = 0.603) in the numbers of species of regional endemic insects. However, subregional endemism is not closely correlated with the size or shape of the subregions in which they occur, or a combination of these factors. Candidate refugial and recolonised subregions are identified, and are consistent with data from palaeoclimatic models and refugia identified using other taxa. We group upland subregions into larger areas of endemism using parsimony analysis of endemism. These groupings are consistent with our understanding of the history of the Wet Tropics rainforests.

Effect of water temperature and oxygen levels on the diving behavior of two freshwater turtles: Rheodytes leukops and Emydura macquarii

Rheodytes leukops is a bimodally respiring turtle that extracts oxygen from the water chiefly via two enlarged cloacal bursae that are lined with multi-branching papillae. The diving performance of R. leukops was compared to that of Emydura macquarii, a turtle with a limited ability to acquire aquatic oxygen. The diving performance of the turtles was compared under aquatic anoxia (0 mmHg), hypoxia (80 mmHg) and normoxia (155 mmHg) at 15, 23, and 30degreesC. When averaged across all temperatures the dive duration of R. leukops more than doubled from 22.4 +/- 7.65 min under anoxia to 49.8 +/- 19.29 min under normoxic conditions. In contrast, aquatic oxygen level had no effect on the dive duration of E. macquarii. Dive times for both species were significantly longer at the cooler temperature, and the longest dive recorded for each species was 538 min and 166 min for R. leukops and E. macquarii, respectively. Both species displayed a pattern of many short dives punctuated by occasional long dives irrespective of temperature or oxygen regime. Rheodytes leukops, on average, spent significantly less time (42 +/- 2 sec) at the surface per surfacing event than did E. macquarii (106 +/- 20 sec); however, surface times for both species were not related to either water temperature or oxygen level.

Mating behavior of Trissolcus basalis (Wollaston) (Hymenoptera : Scelionidae): Potential for outbreeding in a predominantly inbreeding species

The mating behavior of the quasi-gregarious egg parasitoid Trissolcus basalis (Wollaston) was investigated under field conditions. Trissolcus basalis has female-biased sex ratios and is a protandrous species, with males emerging 1-2 days before females. Males competed aggressively for control of the egg mass, with one male assuming dominance and control of the egg mass, although changes in dominance occurred at least once on each egg mass observed. Typical mating behavior involved the dominant male mating his sisters immediately upon their emergence from the egg mass. These behaviors are characteristic of an inbreeding species that manifests local mate competition. However, several aspects of the mating behavior of T. basalis are inconsistent with that of an inbreeding species. Over 18% of emerging females were not mated by the dominant male upon emergence, 13% of females were not observed to be mated at all and may have left their natal site as virgins, 25% of females were mated multiple times and sometimes by multiple males, females remained near the natal site for up to several hours after emergence before emigrating, and males dispersed away from the natal site during female emergence. Trissolcus basalis may be a predominantly inbreeding species but its emergence and mating behavior suggest that low-frequency outbreeding is also likely to occur.

Dynamic Behavior of the Jahn-Teller distorted Cu(H2O)(6)(2+) ion in Cu2+ doped Cs-2[Zn(H2O)(6)](ZrF6)(2) and the crystal structure of the host lattice

The temperature dependence of the X- and Q-band EPR spectra of Cs-2[Zn(H2O)(6)](ZrF6)(2) containing similar to1% Cu2+ is reported. All three molecular g-values vary with temperature, and their behavior is interpreted using a model in which the potential surface of the Jahn-Teller distorted Cu(H2O)(6)(2+) ion is perturbed by an orthorhombic strain induced by interactions with the surrounding lattice. The strain parameters are significantly smaller than those reported previously for the Cu(H2O)(6)(2+) ion in similar lattices. The temperature dependence of the two higher g-values suggests that in the present compound the lattice interactions change slightly with temperature. The crystal structure of the Cs-2[Zn(H2O)(6)](ZrF6)(2) host is reported, and the geometry of the Zn(H2O)(6)(2+) ion is correlated with lattice strain parameters derived from the EPR spectrum of the guest Cu2+ complex.

Improving attitude-behavior correspondence through exposure to normative support from a salient ingroup

Two experiments were conducted to test predictions derived from social identity/self-categorization theory concerning the role of group norms in attitude-behavior consistency. In Experiment 1, 160 students who could be classified as having a more or less certain target attitude were exposed to attitude congruent versus incongruent normative support from a relevant reference group (own university) under conditions of low versus high group salience. Experiment 2 was very similar in design and methodology (N=180), but a different correlate of attitude accessibility was used (an experimental manipulation of repeated expression), the target attitude was changed, and the reference group was gender. Across the 2 experiments there was consistent support for the hypothesis that participants would behave more in accordance with their attitudes when they received normative support for, rather than opposition to, their original attitude from a relevant reference group (i.e., their ingroup, not an outgroup). There was slightly weaker support for the second hypothesis that this effect would be stronger under high-than low-salience conditions. The third hypothesis (see Fazio, 1986), that attitude certainty and repeated expression of the attitude would strengthen attitude-behavior consistency, was well supported, as was the expectation that accessibility effects would be independent of reference group norm effects on attitude-behavior consistency.

Predictors of cheating behavior at a university: A lesson from the psychology of work

The present study investigated students' behavior across academic departments to establish how personality, demographic, educational, attitudinal, and climate (both psychological and departmental) predicted self-reported cheating behavior at a university, Participants were 107 students from a variety of academic disciplines, The results explain 50.5% of the variability in self-reported cheating behavior in terms of demographic (male, school education qualifications), departmental climate, and individual differences (Lie and Neuroticism scales), We concluded that an expanded theoretical perspective (utilizing a wide range of person and situation variables) explained more variability than would otherwise be explained from any single perspective, and that findings from the literature of integrity at work generalize to educational settings. Finally, we discuss the limitations and implications of this research.

Rumors and stable-cause attribution in prediction and behavior

Two stock-market simulation experiments investigated the notion that rumors that invoke stable-cause attributions spawn illusory associations and less regressive predictions and behavior. In Study 1, illusory perceptions of association and stable causation (rumors caused price changes on the day after they appeared) existed despite rigorous conditions of nonassociation (price changes were unrelated to rumors). Predictions (recent price trends will continue) and trading behavior (departures from a strong buy-low-sell-high strategy) were both anti-regressive. In Study 2, stability of attribution was manipulated via a computerized tutorial. Participants taught to view price-changes as caused by stable forces predicted less regressively and departed more from buy-low-sell-high trading patterns than those taught to perceive changes as caused by unstable forces. Results inform a social cognitive and decision theoretic understanding of rumor by integrating it with causal attribution, covariation detection, and prediction theory. (C) 2002 Elsevier Science (USA). All rights reserved.

Behavior of argon gas release from manganese oxide minerals as revealed by Ar-40/Ar-39 laser incremental heating analysis

Manganese oxides in association with paleo-weathering may provide significant insights into the multiple factors affecting the formation and evolution of weathering profiles, such as temperature, precipitation, and biodiversity. Laser probe step-heating analysis of supergene hollandite and cryptomelane samples collected from central Queensland, Australia, yield well-defined plateaus and consistent isochron ages, confirming the feasibility, dating very-fined supergene manganese oxides by Ar-40/(39) Ar technique. Two distinct structural sites hosting Ar isotopes can be identified in light of their degassing behaviors obtained by incremental heating analyses. The first site, releasing its gas fraction at the laser power 0.2-0.4 W, yields primarily Ar-40(atm), Ar-38(atm), and Ar-36(atm), (atmospheric Ar isotopes). The second sites yield predominantly Ar-40* (radiogenic Ar-40), Ar-39(K), and Ar-38(K) (nucleogenic components), at similar to0.5-1.0 W. There is no significant Ar gas released at the laser power higher than 1.0 W, indicating the breakdown of the tunnel sites hosting the radiogenic and nucleogenic components. The excellent match between the degassing behaviors of Ar-40*, Ar-39(K), and Ar-38(K) suggests that these isotopes occupy the same crystallographic sites and that Ar-39(K) loss from the tunnel site by recoil during neutron irradiation and/or bake-out procedure preceding isotopic analysis does not occur. Present investigation supports that neither the overwhelming atmospheric Ar-40 nor the very-fined nature of the supergene manganese oxides poses problems in extracting meaningful weathering geo-chronological information by analyzing supergene manganese oxides minerals.

Simulation of the influence of rate- and state-dependent friction on the macroscopic behavior of complex fault zones with the lattice solid model

In order to understand the earthquake nucleation process, we need to understand the effective frictional behavior of faults with complex geometry and fault gouge zones. One important aspect of this is the interaction between the friction law governing the behavior of the fault on the microscopic level and the resulting macroscopic behavior of the fault zone. Numerical simulations offer a possibility to investigate the behavior of faults on many different scales and thus provide a means to gain insight into fault zone dynamics on scales which are not accessible to laboratory experiments. Numerical experiments have been performed to investigate the influence of the geometric configuration of faults with a rate- and state-dependent friction at the particle contacts on the effective frictional behavior of these faults. The numerical experiments are designed to be similar to laboratory experiments by DIETERICH and KILGORE (1994) in which a slide-hold-slide cycle was performed between two blocks of material and the resulting peak friction was plotted vs. holding time. Simulations with a flat fault without a fault gouge have been performed to verify the implementation. These have shown close agreement with comparable laboratory experiments. The simulations performed with a fault containing fault gouge have demonstrated a strong dependence of the critical slip distance D-c on the roughness of the fault surfaces and are in qualitative agreement with laboratory experiments.