Use of time in a decision‐making process by a parasitoid

1. Time perception is seldom studied in invertebrates, with the limited experimental evidence being insufficient to provide a comprehensive pattern of the capacity of invertebrates to measure time and use it in decision‐making processes. 2. In this study, it was hypothesized that insect parasitoids have evolved the capacity to measure time precisely and to use it to optimize foraging decisions related to host exploitation. To examine time perception in females of the gregarious egg parasitoid Trichogramma euproctidis, the present study used their ability to adjust their investment (number of eggs laid) in a host to the initial transit duration (interval between the first contact with the host and the following contact with the substrate). Females utilize this method to assess host egg size, as a large egg necessarily requires more time to evaluate than a small host. In this study, the initial transit duration for a given sized egg was artificially extended by suspending it. 3. For similar sized hosts, female T. euproctidis significantly increased both oviposition duration and progeny allocation following a longer initial transit duration. 4. These results demonstrate the intrinsic capacity of this parasitoid to measure time and to adjust their progeny investment accordingly. This is believed to be one of the few demonstrations of a retrospective measure of time in an invertebrate.     

Determinate growth and the scaling of photosynthetic energy intake in the solitary coral Fungia concinna (Verrill)

For many marine invertebrates, the maximum size of an individual is influenced heavily by environmental factors and may be limited by energetic constraints. In this study, an energetic model developed originally for anemones was applied to the free-living scleractinian Fungia concinna (Verrill) from Moorea (French Polynesia) to test the hypothesis that energetic constraints limit the size of this solitary coral. The modified model assumed that photosynthesis was the primary source of metabolic energy, and that metabolic costs were represented by aerobic respiration; these sources and sinks of energy were compared using daily energy budgets that were analyzed using double logarithmic regressions of energy against coral size. With this approach, energy limitation is characterized by a scaling exponent for energetic cost (b_cost) that is larger than the scaling exponent for energy intake (b_intake). For the size range of F. concinna studied, b_intake = 0.73 ± 0.09 and b_cost = 0.46 ± 0.10, thereby demonstrating that large individuals accumulated an energetic surplus, even when the expenditure associated with host tissue and symbiont growth was included in the model. The surplus of energy that this coral acquires as it grows appears to be driven by the scaling of traits associated functionally with the scaling of respiration and photosynthesis. Specifically, tissue biomass displayed a strong positive allometry with respect to surface area (i.e., b > 1), and this constraint on surface area may be the mechanistic basis of the low scaling exponent for metabolic cost. In contrast, the capacity for autotrophy - defined indirectly as Symbiodinium population density and chlorophyll content - increased isometrically with surface area, and likely contributed to the higher scaling exponent for intake relative to cost. Our results suggest that growth in F. concinna is not limited strictly by energy, but instead maximum size must be determined by alternative physiological or ecological constraints.     

Thermal time assessment of suitable areas for navy bean (Phaseolus vulgaris) production in the UK

In field trials at eight sites throughout the UK the mean thermal time requirement for navy beans from sowing to harvest for a standard cultivar, Marcus, was 2069 Ontario Heat Units (OHU). Low level plastic covers increased the range of warm environments at one site and gave a mean thermal time required of 2098 OHU. Analysis of daily air temperatures from six weather stations throughout the UK over a 29 year period, showed a 14 day possible planting period on the south coast of England, but gave a high probability of crop failure in Scotland. Maps of England and Wales indicating the probability of achieving 2000 OHU were produced from 5 km grid point temperatures. Less than 2% of the land had more than a 60% chance of receiving 2000 OHU under the present climate, however this area increased to 70% with a mean temperature rise of 1.5°C. Although 2000 OHU is often used as the thermal time requirement of navy beans, these trials showed that it may be more accurate to use the higher figure of 2087 OHU from sowing to harvest, and restrict the use of 2000 OHU to the period between emergence and harvest. When the map was redrawn using 2087 OHU and current climate, no parts of England and Wales showed a reasonable chance of growing the present cultivars of navy beans.     

Kleptoparasitic prey competition in shoaling fish: effects of familiarity and prey distribution

Familiarity is thought to stabilize dominance hierarchies andreduce aggressive interactions within groups of socially livinganimals. Though familiarity has been widely studied in shoalingfish, few studies have investigated changes in prey competitionas a function of time spent together within groups of initiallyunfamiliar individuals. In this study, we created shoals ofthree-spined stickleback (Gasterosteus aculeatus) and monitoredchanges in foraging rates and related competitive behaviorswithin shoals over a 4-week period in experimental series whereprey was spatially and temporally concentrated or dispersed.Prey share was unequal under both prey distribution modes, anddisparity in prey share was not seen to change as trials progressed.Interestingly, the contest rate for prey items fell over timewhen individuals were competing for dispersed prey but not whenprey were concentrated. We found no evidence that fish showedassociation preferences for either group members that had consumeda greater or lesser proportion of prey during trials. Thoughthe intensity of competition may be reduced by increased groupstability in nature, this is likely to be strongly dependenton the way prey resources are distributed through space andtime.     

Mechanisms of madness: evolutionary psychiatry without evolutionary psychology

Delusions are currently characterised as false beliefs produced by incorrect inference about external reality (DSM IV). This inferential conception has proved hard to link to explanations pitched at the level of neurobiology and neuroanatomy. This paper provides that link via a neurocomputational theory, based on evolutionary considerations, of the role of the prefrontal cortex in regulating offline cognition. When pathologically neuromodulated the prefrontal cortex produces hypersalient experiences which monopolise offline cognition. The result is characteristic psychotic experiences and patterns of thought. This bottom-up account uses neural network theory to integrate recent theories of the role of dopamine in delusion with the insights of inferential accounts. It also provides a general model for evolutionary psychiatry which avoids theoretical problems imported from evolutionary psychology.     

Nests, vocalizations, and conservation status of endangered Cochabamba Mountain-Finches (Compsospiza garleppi)

ABSTRACT.   Cochabamba Mountain-Finches ( Compsospiza garleppi ) are endangered residents of semihumid shrublands in the high Andes, with a range restricted to a few high valleys surrounding the city of Cochabamba, Bolivia. We examined the breeding behavior, feeding ecology, habitat requirements, vocalizations, and conservation status of Cochabamba Mountain-Finches from November 2006 to April 2007. We observed 10 nests of eight pairs, with nests found in a variety of small woody shrubs as well as bunchgrass and a ground bromeliad. Clutches ( N = 2) consisted of one or two eggs, and all broods ( N = 4) included one or two young. Our observations suggest that Cochabamba Mountain-Finches are not Polylepis specialists as previously thought, and use a diversity of native shrubs often associated with Polylepis woodlands for foraging and nesting. Pairs inhabited modified habitats where native vegetation and woodland edge persisted, but were not observed in closed canopy woodlands. Cochabamba Mountain-Finches frequently foraged on the edges of potato fields in a rural community and, at least occasionally, consumed parts of unearthed tubers. We recorded two previously unknown song types and three types of calls, and one song type was found to be useful for playback surveys. We recommend that future research and conservation actions include thorough surveys using playback to determine population sizes, and that habitat restoration projects focus on maintaining a diversity of native shrubs rather than only Polylepis trees.     

Proportionate spatial sampling and equal‐time sampling of mobile animals: A dilemma for inferring areal dependence

Abstract Patch or island area is one of the most frequently used variables for inference in conservation biology and biogeography, and is often used in ecological applications. Given that all of these disciplines deal with large spatial scales, exhaustive censusing is not often possible, especially when there are large numbers of patches (e.g. for replication and control purposes). Therefore, data for patches or islands are usually collected by sampling. We argue that if area is to be used as an inferential factor, then the objects under study (i.e. the patches) must be characterized on an areal basis. This necessarily means that fixed‐area sampling is inadequate (e.g. a single standard quadrat or transect set within patches irrespective of the patch area) and that some form of area‐proportionate sampling is needed (e.g. a fixed areal proportion of each patch is surveyed by random allocation of standard quadrats across each patch). However, use of area‐proportionate sampling is not usually dissociated from the increased temporal intensity of sampling that arises from using this approach. The dilemma we see is deciding how much of the area‐specificity of variables such as species richness, rare‐species indices or probabilities of occurrence of individual species is related to the area‐proportionate survey protocol and how much is due to the temporal intensity of surveys. We undertook a study in which we balanced temporal and spatial effects by increasing the time spent surveying smaller patches of vegetation to account for the area‐ratio difference. The estimated species richness of birds of the box–ironbark system of central Victoria, Australia, was found to depend strongly upon area when area‐proportionate sampling alone was performed. When time‐balancing was imposed upon area‐proportionate sampling, the differences between smaller (10‐ha) and larger (40‐ha) areas were much reduced or effectively disappeared. We show that species found in the additional surveys used to conduct the time‐balancing were significantly less abundant than species recorded in area‐proportionate sampling. This effect is probably most severe for mobile animals, but may emerge in other forms of sampling.     

A critical assessment of two species distribution models: a case study of the vervet monkey (Cercopithecus aethiops)

Aim Species distribution models are invaluable tools in biogeographical, ecological and applied biological research, but specific concerns have been raised in relation to different modelling techniques in terms of their validity. Here we compare two fundamentally different approaches to species distribution modelling, one based on simple occurrence data where the lack of an ecological framework has been criticized, and the other firmly based in socio‐ecological theory but requiring highly detailed behavioural information that is often limited in availability. Location (Sub‐Saharan) Africa. Methods We used two distinct techniques to predict the realized distribution of a model species, the vervet monkey (Cercopithecus aethiops Linnaeus, 1758). A maximum entropy model was produced taking 13 environmental variables and presence‐only data from 174 sites throughout Africa as input, with an additional 58 sites retained to test the model. A time‐budget model considering the same environmental variables was constructed from detailed behavioural data on 20 groups representing 14 populations, with presence‐only data from the remaining 218 sites reserved to test model predictions on vervet monkey occurrence. Both models were further validated against a reference species distribution map as drawn up by the African Mammals Databank. Results Both models performed well, with the time budget and maximum entropy algorithms correctly predicting vervet monkey presence at 78.4% and 91.4% of their respective test sites. Similarly, the time‐budget model correctly predicted presence and absence at 87.4% of map pixels against the reference distribution map, and the maximum entropy model achieved a success rate of 81.8%. Finally, there was a high level of agreement (81.6%) between the presence–absence maps produced by the two models, and the environmental variables identified as most strongly driving vervet monkey distribution were the same in both models. Main conclusions The time‐budget and maximum entropy models produced accurate and remarkably similar species distribution maps, despite fundamental differences in their conceptual and methodological approaches. Such strong convergence not only provides support for the credibility of current results, but also relieves concerns about the validity of the two modelling approaches.     

Sexual advertisement and immune function in an arachnid species (Lycosidae)

A simple version of the immunocompetence handicap hypothesizesthat through condition-dependence, the size of the sexual traitmay be positively related to immune function at the populationlevel. In the present study, we investigated the relationshipbetween sexual advertisement and immune function in a naturalpopulation of male wolf spiders, Hygrolycosa rubrofasciata (Araneae:Lycosidae). Males of H. rubrofasciata have a costly and condition-dependentacoustic signal, courtship drumming. In the mating season, malesdrum against dry leaves while wandering around the habitat searchingfor receptive females. Males increase their mating success byincreasing their drumming rate and mobility. We used drummingrate and mobility measured without female proximity as estimatesof sexual advertisement. As estimates of male immune function,we used encapsulation rate and lytic activity. Encapsulationrate is a common challenging technique, which measures immuneresponse against multicellular parasites. Lytic activity isa monitoring technique, which measures immune response againstpathogens. Our results show that males with higher drummingrate had higher encapsulation rate. This suggests that femalesmight use drumming rate as a signal for choosing males withgood immunocompetence. Moreover, our results show that maleswith higher mobility had higher lytic activity. As females aremore likely to encounter those males that have higher mobility,this might also select males with better immune function. Ourresults suggest that the immunocompetence handicap might workalso among spiders, although we could not assess the causalityof the relationship between sexual selection and immune functionin this correlational study.