Constitutive and Operational Variation of Learning in Foraging Predatory Mites

Learning is widely documented across animal taxa but studies stringently scrutinizing the causes of constitutive or operational variation of learning among populations and individuals are scarce. The ability to learn is genetically determined and subject to constitutive variation while the performance in learning depends on the immediate circumstances and is subject to operational variation. We assessed variation in learning ability and performance of plant-inhabiting predatory mites, Amblyseius swirskii, caused by population origin, rearing diet, and type of experience. Using an early learning foraging paradigm, we determined that homogeneous single prey environments did not select for reduced learning ability, as compared to natural prey-diverse environments, whereas a multi-generational pollen diet resulted in loss of learning, as compared to a diet of live prey. Associative learning produced stronger effects than non-associative learning but both types of experience produced persistent memory. Our study represents a key example of environmentally caused variation in learning ability and performance.     

Predatory Mites in Tropical Australia: Local Species Richness complementarity1

Although little supporting data is available, mites (Acari) are often considered to be one of the ‘hyperdiverse’ taxa in tropical ecosystems. To test this assumption, we sampled single guilds of predatory mites (Hydracarina and Mesostigmata) in three different habitats (fresh water, rotting fungi, and forest foliage) across a range of sites in monsoonal, wet-tropical, and subtropical Australia. Most species (61%) were collected at a single site; as a result, all seven collector's curves rose steeply with little indication of reaching asymptotes. Regional faunas ranged from 87–94 percent distinct and of the 247 species identified, 114 (46%) were previously unknown in Australia and appear to be new. Even within taxonomically well-studied groups, such as the Hydracarina and Phytoseiidae, we found many new species (32% and 60%, respectively). Our results suggest that the diversity of tropical mites is very high and comparable to that of many insect taxa. We propose a simple model to explain our results, i.e. that in the tropics, high levels of complementarity between sites amplify local mite species richness. We tested this model by additional sampling, comparing within-site to between-site complementarity, and contrasting temperate with tropical foliar Mesostigmata. As predicted by the model, collecting at new sites continued to accumulate new species, complementarity was significantly greater between-sites than within-sites (72 vs. 25%), and temperate collections were more homogeneous and less diverse than tropical collections.     

Intraguild Interactions Between the Predatory Mites Neoseiulus californicus and Phytoseiulus persimilis

Species at the same trophic level may interact through competition for food, but can also interact through intraguild predation. Intraguild predation is widespread at the second and third trophic level and the effects may cascade down to the plant level. The effects of intraguild predation can be modified by antipredator behaviour in the intraguild prey. We studied intraguild predation and antipredator behaviour in two species of predatory mite, Neoseiulus californicus and Phytoseiulus persimilis, which are both used for control of the two-spotted spider mite in greenhouse and outdoor crops. Using a Y-tube olfactometer, we assessed in particular whether each of the two predators avoids odours emanating from prey patches occupied by the heterospecific predator. Furthermore, we measured the occurrence and rate of intraguild predation of different developmental stages of P. persimilis and N. californicus on bean leaves in absence or in presence of the shared prey. Neither of the two predator species avoided prey patches with the heterospecific competitor, both when inexperienced with the other predator and when experienced with prey patches occupied by the heterospecific predator. Intraguild experiments showed that N. californicus is a potential intraguild predator of P. persimilis. However, P. persimilis did not suffer much from intraguild predation as long as the shared prey was present. This is probably because N. californicus prefers to feed on two-spotted spider mites rather than on its intraguild prey.     

Canid Reproductive Biology: an Integration of Proximate Mechanisms and Ultimate Causes

SYNOPSIS. The canid reproductive system includes many featuresthat are unusual or even unique among mammals. Focusing on graywolves, for example, these include monogamy, monestrum withexceptionally long proestrous and diestrous phases, a copulatorylock or tie, incorporation of adult young into the social group,behavioral suppression of mating in these subordinate young,obligate pseudopregnancy in subordinate females, and alloparentalcare. These features can be analyzed on the levels of both proximateand ultimate causation by considering them in the context ofthe reproductive system as a whole. First, when assessing possibleproximate mechanisms, monestrum appears to be pivotal. It isprobably accomplished by the extremely long luteal or diestrousphase, which is followed by a seasonal peak in prolactin. Twosequellae of the extended diestrus (or pseudopregnancy) in non-pregnantsubordinate females are to 1) suppress any subsequent cycles,and 2) hormonally prime them to behave maternally. The prolactinpeak in all adult pack members, coincident with the birth ofpups, also may stimulate parental behavior. The risk of monestrum(limited chance for conception) appears to be reduced by therelatively long proestrous and estrous periods, as well as bymonogamy. The adaptive value, or ultimate cause, of this reproductivesystem is most obvious for the more social canid species, suchas the gray wolf. That is, advantages to sociality, such ascooperative hunting, may have driven development of the anomaliesof the reproductive system.     

Sexual Strategy and Size Dimorphism in Rattlesnakes: Integrating Proximate and Ultimate Causation

SYNOPSIS. Integrating proximate and ultimate causes and effectssimultaneously in the study of behavior is challenging and complex,but useful. This is equivalent to asking both "How?" (in thesense of proximate mechanisms) and "Why?" (in the sense of ultimateevolutionary payoffs) an organism operates in one way and notanother. Sex differences in rattlesnake (i) size and growthand (ii) mating and reproductive strategies and tactics, providea good theoretical and empirical context in which to attemptsuch integration. We employ interdisciplinary and multidisciplinaryapproaches in our behavioral and physiological work, but wemean something different by "integrative," that amounts to thesimultaneous study of both proximate and ultimate levels ofcausation and explanation. Though not always feasible, thisapproach represents an important goal to work towards becauseit attempts to represent faithfully the complexity inherentin living systems. To this end, we also employ a variety ofmodeling approaches, which entrain intuition, generate new hypotheses,and sharpen inference. Individual-based simulations, for example,offer promise for broad, integrative programs of biologicalresearch.     

Integrating Proximate and Ultimate Causation in the Study of Vertebrate Behavior: Methods Considerations

SYNOPSIS. Methods issues are critical for the integration ofproximate and ultimate explanations of animal behavior. Understandingthat evolution of behavior may begin with changes in sensoryand perceptual systems is a first step. For example, advancesin neurobiology can trigger questions about social behavior.Variation in the size of particular brain areas, such as thehippocampus, can be related to variation in socio-spatial systems.Second, procedures, developed in recent years, provide new avenuesto understand behavior. Hormone assay techniques, such as RIAand ELISA, can be performed on some hormones from urine andfeces collected in the wild. Metabolic measurement, such asthe use of doublylabeled water, make it possible to measureenergy costs under field conditions. Advances in DNA technologiesprovide new perspectives, particularly with regard to measuringreproductive success. Third, current theories in behavior canbe tested with regard to physiological mechanisms; all thatis needed is some ingenuity to design and execute appropriatestudies. These include kin recognition, sex ratio variation,and foraging behavior. Fourth, cross—fertilization betweenlaboratory and field approaches produces new insights regardingbehavior. Organizational effects of hormones have now been exploredin field populations of mice and in domestic swine. Testingaspects of foraging behavior in the laboratory is another example.Fifth, simulation models have been used to produce new questionsabout both proximate and ultimate aspects of behavior. Exploringbehavioral phenomena may involve semi—natural settings.The suitability of semi—natural enclosures for the studyof house mouse behavior has been tested with regard to densityand home range size.     

Initial Screening of Little Known Predatory Mites in Brazil as Potential Pest Control Agents

The objective of this study was to evaluate the oviposition rate and the survivorship of some of the most common predators on plants of the natural vegetation of southeastern Brazil, when confined with different food sources. Forty-four laboratory tests were carried out, each corresponding to a different combination of predator species and food source. The predators tested were: Phytoseiidae—Amblyseius acalyphus, Euseius citrifolius, Iphiseiodes zuluagai, Metaseiulus (Metaseiulus) camelliae, Typhlodromips cananeiensis; Stigmaeidae—Agistemus floridanus, Zetzellia malvinae; Tydeidae—Pronematus sp. For most predators, the highest oviposition rate and survivorship were obtained when the prey was one of the tenuipalpid mites, Brevipalpus phoenicis or Tenuipalpus heveae. With the exception of A. floridanus, the predators had low oviposition rate and survivorship on Calacarus heveae relative to their respective rate on other food sources. Predators had also generally low oviposition rate and survivorship when feeding on Tetranychus urticae, Oligonychus gossypii or Frankliniella sp.     

Oviposition Behavior of Interacting Predatory Mites: Response to the Presence of Con- and Heterospecific Eggs

Oviposition behavior may be affected by the presence of potential future competitors, mates, or predators of offspring. We examined patch choice, oviposition site preference and egg production in the predaceous mites Phytoseiulus persimilis and Neoseiulus californicus (Acari: Phytoseiidae) when given a choice between paired spider mite patches with and without conspecific eggs, with and without heterospecific eggs, and with conspecific or heterospecific eggs. Neoseiulus californicus females had no patch preference and distributed their eggs randomly in all choice situations. This was also the case with P. persimilis females given a choice between patches with and without conspecific eggs and between patches with either con- or heterospecific eggs. Phytoseiulus persimilis females confronted with patches with and without heterospecific eggs preferentially stayed and oviposited in the predator free patches. We discuss the oviposition strategies of P. persimilis and N. californicus with respect to food competition, cannibalism and intraguild predation.     

Prevalence and Correlates of Poor Sleep Quality and Daytime Sleepiness in Belgian Truck Drivers

Sleepiness and sleep complaints are common among professional drivers. Sleepiness is a considerable problem not only because it affects the drivers' well-being, but also because of the consequences for performance and safety. Assessment of the (self-reported) prevalence and research into the risk factors are thus an important health issue and are also indispensable to prevent productivity loss and work-related accidents and injuries. Therefore, the aim of this study was to describe sleeping, driving, and health characteristics of Belgian truck drivers and to determine occupational and individual factors associated with poor sleep quality and daytime sleepiness. Cross-sectional data were collected using a self-administered questionnaire that included the Pittsburgh Sleep Quality Index (PSQI), Epworth Sleepiness Scale (ESS), and Berlin Questionnaire (BQ). The mean (SD) age of the 476 studied truck drivers was 42.7 (10.2) yrs and the mean (SD) body mass index was 27.3 (5.1) kg/m². Approximately 47% declared that they drove >50 h/wk and found their work schedule unrealistic. The mean (SD) PSQI score was 4.45 (2.7); poor quality of sleep (PSQI >5) was found in 27.2%. The mean (SD) ESS score was 6.79 (4.17); 18% had a score >10. The BQ indicated that 21.5% had a higher risk on obstructive sleep apnea. In multiple logistic regression analysis, low educational level (odds ratio [OR] 1.86), current smoking (OR 1.75), unrealistic work schedule (OR 1.75), and risk for obstructive sleep apnea (OR 2.97) were found to be independent correlates of daytime sleepiness. Poor sleep quality was significantly associated with poor self-perceived health (OR 1.95), unrealistic work schedule (OR 2.85), low job satisfaction (OR 1.91), and less driving experience (OR 1.73). These results show that poor sleep quality and daytime sleepiness were prevalent in Belgian truck drivers. Taking into account that several significant correlates with respect to these sleep problems were identified both at the individual and the occupational level, comprehensive countermeasures to improve working conditions and organization are needed, as well as health promotion interventions, to ensure the safety and well-being of truck drivers. (Author correspondence: lutgart.braeckman@ugent.be)     

Effects of Light on the Tritrophic Interaction Between Kidney Bean Plants, Two-Spotted Spider Mites and Predatory Mites, Amblyseius Womersleyi (Acari: Phytoseiidae)

By analyzing the volatiles from Tetranychus urticae-infested kidney bean plants (Phaseolus vulgaris) at different times for two days, we found that they were mainly produced in the light. Tetranychus urticae showed a higher oviposition rate and spent more time feeding during the day (in the light) than at night (in the dark). Infested leaves placed in the light attracted the predatory mite Amblyseius womersleyi, whereas those that were placed in the dark for at least 2h in daytime did not. This indicates that presence or absence of light affects the production of herbivore-induced plant volatiles. Amblyseius womersleyi dispersed more frequently and consumed more T. urticae eggs during the day (in the light) than at night (in the dark), whereas their oviposition rate did not differ between day and night. Presence or absence of herbivore-induced plant volatiles in the surroundings did not affect dispersal, predation or oviposition rates of A. womersleyi. These results show that A. womersleyis behavior coincides with the production pattern of herbivore-induced plant volatiles.     

Social Familiarity Reduces Reaction Times and Enhances Survival of Group-Living Predatory Mites under the Risk of Predation

Background

Social familiarity, which is based on the ability to recognise familiar conspecific individuals following prior association, may affect all major life activities of group-living animals such as foraging, reproduction and anti-predator behaviours. A scarcely experimentally tested explanation why social familiarity is beneficial for group-living animals is provided by limited attention theory. Limited attention theory postulates that focusing on a given task, such as inspection and assessment of unfamiliar group members, has cognitive and associated physiological and behavioural costs with respect to the attention paid to other tasks, such as anti-predator vigilance and response. Accordingly, we hypothesised that social familiarity enhances the anti-predator success of group-living predatory mites, Phytoseiulus persimilis, confronted with an intraguild predator, the predatory mite Amblyseius andersoni.

Methodology/Principal Findings

We videotaped and analysed the response of two P. persimilis larvae, held in familiar or unfamiliar pairs, to attacks by a gravid A. andersoni female, using the behavioural analyses software EthoVision Pro®. Familiar larvae were more frequently close together, reacted more quickly to predator attacks, survived more predator encounters and survived longer than unfamiliar larvae.

Significance

In line with the predictions of limited attention theory, we suggest that social familiarity improves anti-predator behaviours because it allows prey to shift attention to other tasks rather than group member assessment.     

Polyandry and protandry in butterflies

Current models on protandry in butterflies assume that females mate only once, yet for many species this assumption is not realistic. In this paper a model is formulated to study how polyandry, i.e. repeated mating of females, affects protandry. Moreover, the model is elaborated to describe the probability distribution of the number of matings per female. Field data on this distribution are well described by the model, which supports the use of the law of mass action to describe the encounter rate between males and females. Finally, a weight factor is derived, taking into account the decline in oviposition rate with age, as well as the chance that a female is remated. In comparison with the situation that all matings contribute equally to a male's reproductive success, the application of the weight factor enhances protandry. This suggests that mate competition is not the sole cause of protandry.     

How Predatory Mites Learn to Cope with Variability in Volatile Plant Signals in the Environment of their Herbivorous Prey

When the chemical cues co-occurring with prey vary in time and space, foraging predators profit from an ability to repeatedly associate chemical cues with the presence of their prey. We demonstrate the ability of a predatory arthropod (the plant-inhabiting mite, Phytoseiulus persimilis) to learn the association of a positive stimulus (herbivorous prey, Tetranychus urticae) or a negative stimulus (hunger) with a chemical cue (herbivore-induced plant volatiles or green leaf volatiles). It has been suggested that the rate at which the integration of information becomes manifest as a change in behaviour, differs between categories of natural enemies (parasitoids versus insect predators; specialist versus generalist predators). We argue that these differences do not necessarily reflect differential learning ability, but rather relate to the ecologically relevant time scale at which the biotic environment changes.     

Evolution of Polyandry in Birds

Polyandry in which one female forms either simultaneous or sequentialpair bonds with more than one male is a rare vertebrate mateshipsystem. Prior to 1972 only two cases were known with certaintyamong birds. All other reports of polyandry were based on inadequateinformation. Recently, polyandry has been demonstrated in severaladditional species. Surprisingly, they all belong to the avianorder Charadriiformes. Comparisons of the existing polyandroussystems suggest that they can be arranged in a sequence thatleads through a series of relatively minor differences frommonogamy to simultaneous polyandry. Polyandrous species differ from species with other mateshipsystems in the following ways: females large, females more aggressive,egg or clutch size reduced, production of multiple clutches.Except in some sequential systems, the small, subordinate malesperform all incubation behavior and provide all parental carefor the chicks. In the Charadriiformes, polyandry has evolvedin conjunction with sex role reversal and with assumption ofincubation and parental behavior by the male. It is not clearwhy role reversal and parental behavior are related. The simplestforms of polyandry are in high-latitude birds, but the bestdeveloped forms are found in tropical species.     

Infochemical-Mediated Niche Use by the Predatory Mites Typhlodromalus manihoti and T. aripo (Acari: Phytoseiidae)

In Africa, Typhlodromalus manihoti and T. aripo, two introduced predators of the cassava green mite Mononychellus tanajoa, occupy different parts of cassava foliage. In the present study, niche use by these two predators, as mediated by prey-induced infochemicals, was investigated. In response to prey feeding damage, cassava plant parts emit volatile blends, that attract phytoseiidae predators. When given a choice between old cassava leaves infested with M. tanajoa and either apices or young cassava leaves infested with M. tanajoa, T. aripo displayed a marked preference for odors emitted from either infested apices or infested young leaves over infested old leaves but showed no preference for odors from apices versus young leaves, all infested with M. tanajoa. Typhlodromalus manihoti did not discriminate between volatiles from the three infested cassava plant parts. Our data show that T. aripo uses differences in volatile blends released by infested cassava plant parts and restricts its fundamental niche to a realized niche, which enables coexistence with its competitor T. manihoti.     

Pollen as Food for the Predatory Mites Iphiseius Degenerans and Neoseiulus Cucumeris (Acari: Phytoseiidae): Dietary Range and Life History

Although all known phytoseiid mites (Acari: Phytoseiidae) are predators of mites or small insects, many readily feed and reproduce on pollen as well. This ability to feed on food from plant origin increases their survival during periods when prey is locally sparse, but might occur at the expense of the ability to utilize food as efficiently as specialized predators. In this study we compare two predatory mite species used as biological control agents against thrips, Neoseiulus cucumeris and Iphiseius degenerans, with respect to (1) the range of pollen species that may serve as food sources for a sustained oviposition; and (2) the life history and expected intrinsic growth rates on some suitable pollen diets. The results show that I. degenerans is, compared to N. cucumeris, able to utilize a larger proportion of approx. 25 pollen species tested, but does not show equally high ovipositional rates as N. cucumeris. Consequently, the highest intrinsic growth rate for I. degenerans (0.21 day ^–1) will be surpassed by N. cucumeris.     

Functional and Numerical Responses of Three Species of Predatory Phytoseiid Mites (Acari: Phytoseiidae) to Thrips flavidulus (Thysanoptera: Thripidae)

Phytoseiid mites are considered the most effective natural enemies of pest mites. They also have been shown to attack pest thrips. It is unknown, however, whether phytoseiid mites can reduce high densities of Thrips flavidulus (Bagnall). We addressed this question by the study of functional and numerical responses. The aim of this research was to evaluate the potential predation success of the adults of three predatory mites, Neoseiulus cucumeris (Oudemans), Neoseiulus barkeri (Hughes), and Euseius nicholsi (Ehara & Lee), against the first-instar of T. flavidulus in a climatic chamber at five different temperatures. The results showed that the functional responses of those predators reflected the Holling type II functional response and were density dependent and positively related to temperature. For the three predatory mites, predation and successful attack rates increased with increasing temperature up to 26°C, reducing afterward. Handling time had the opposite trend. Reproductive ability also increased with an increase in temperature and prey consumption.     

Effect of Air Humidity on the Egg Viability of Predatory Mites (Acari: Phytoseiidae, Stigmaeidae) Common on Rubber Trees in Brazil

Rubber pest mites, Calacarus heveae and Tenuipalpus heveae, reach economic damage levels at the end of the rainy season and the beginning of the dry season in Brazil. Therefore, low humidity adaptation might be an important characteristic for predatory mites to successfully control pest organisms. This study determined the effect of the relative humidity (RH) levels of 30–100% on the hatching of larvae of Amblyseius acalyphus, Euseius citrifolius, Iphiseiodes zuluagai, Metaseiulus camelliae, Agistemus floridanus and Zetzellia malvinae at 25 ± 0.5 °C. These predatory mites are common on rubber trees in the state of São Paulo and might be used for introduction in the major rubber tree production regions in the state of Mato Grosso. At 70% RH or higher, viability was 70% or higher for all species, indicating that their performance might be higher during the rainy season than during the dry season. Eggs of E. citrifolius and M. camelliae presented higher viability at the lower relative humidity levels than those of other species, indicating that these species might have higher chance to persist in the dry season. It is suggested that M. camelliae should be further evaluated for introduction in the state of Mato Grosso, considering that this mite is not yet present in that area.