Krzysztof Miler

Selection for alternative male reproductive tactics alters intralocus sexual conflict.

Intralocus sexual conflict (IASC) arises when fitness optima for a shared trait differ between the sexes; such conflict may help maintain genetic variation within populations. Sex‐limited expression of sexually antagonistic traits may help resolve the conflict, but the extent of this resolution remains a subject of debate. In species with alternative male reproductive tactics, unresolved conflict should manifest more in a more sexually dimorphic male phenotype. We tested this prediction in the bulb mite (Rhizoglyphus robini), a species in which aggressive fighters coexist with benign scramblers. To do this, we established replicated lines in which we increased the proportion of each of the alternative male morphs using artificial selection. After approximately 40 generations, the proportion of fighters and scramblers stabilized at >0.9 in fighter‐ and scrambler‐selected lines, respectively. We then measured several female fitness components. As predicted by IASC theory, female fecundity and longevity were lower in lines selected for fighters and higher in lines selected for scramblers. This finding indicates that sexually selected phenotypes are associated with an ontogenetic conflict that is not easily resolved. Furthermore, we suggest that IASC may be an important mechanism contributing to the maintenance of genetic variation in the expression of alternative reproductive tactics.

Moribund Ants Do Not Call for Help.

When an antlion captures a foraging ant, the victim’s nestmates may display rescue behaviour. This study tested the hypothesis that the expression of rescue behaviour depends on the life expectancy of the captured ant. This hypothesis predicts that the expression of rescue behaviour will be less frequent when the captured ant has a lower life expectancy than when it has a higher life expectancy because such a response would be adaptive at the colony level. Indeed, significant differences were found in the frequency of rescue behaviours in response to antlion victims with differing life expectancies. In agreement with prediction, victims with lower life expectancies were rescued less frequently, and those rescues had a longer latency and shorter duration. There was also a qualitative difference in the behaviour of rescuers to victims from the low and high life expectancy groups. Several explanations for these findings are proposed.

Sedentary antlion larvae (Neuroptera: Myrmeleontidae) use vibrational cues to modify their foraging strategies

Learning abilities are exhibited by many animals, including insects. However, sedentary species are typically believed to have low capacities and requirements for learning. Despite this view, recent studies show that even such inconspicuous organisms as larval antlions, which employ an ambush predation strategy, are capable of learning, although their learning abilities are rather simple, i.e., limited to the association of vibrational cues with the arrival of prey. This study demonstrates, for the first time, that antlion larvae can use vibrational cues for complex modifications of their foraging strategies. Specifically, antlion larvae rapidly learn to differentiate between the vibrational cues associated with prey of different sizes, and they save resources by ignoring smaller prey in favour of larger, more energetically profitable prey. Moreover, antlion larvae can learn to associate vibrational cues with the loss of their prey, and they respond by burying their victims under the sand more often and more rapidly than do individuals with no opportunities to form such associations. These findings provide not only new insights into the cognitive abilities of animals but also support for the optimal foraging strategy concept, suggesting the importance of maximizing fitness output by balancing the costs and benefits of alternative foraging strategies.

Different predation efficiencies of trap-building larvae of sympatric antlions and wormlions from the rainforest of Borneo: Antlions and wormlions from Borneo

1. This study reports the discovery of sympatric populations of antlions (Neuroptera: Myrmeleontidae) and wormlions (Diptera: Vermileonidae) in a unique system of sandy microhabitats in the lowland rainforest of Borneo. The two species convergently evolved sit‐and‐wait predatory larvae, which construct pitfall traps to hunt insects. Despite similar specialised foraging strategies, the two species coexist in the competitive environment of small, isolated sandy patches in the rainforest, which begs the question: what biological characteristics allow their coexistence?

Larval antlions with more pronounced behavioural asymmetry show enhanced cognitive skills.

Brain lateralization is hypothesized to improve the efficiency of information processing. Here, we found that some Myrmeleon bore antlion larvae showed individual asymmetry in righting from a supine to normal position over one side of their body, which can be considered a reflection of greater brain lateralization. We demonstrated that these behaviourally asymmetrical individuals showed improved learning abilities, providing novel evidence that brain lateralization leads to beneficial effects on cognitive functions.

Secretions of mandibular glands are not involved in the elicitation of rescue behaviour in Formica cinerea ants

Certain ants perform rescue behaviour for other ants that require help, and the expression of rescue behaviour is hypothesized to depend on signals (“calls for help”) sent by the imperilled individuals. We studied whether the mandibular glands were involved in the elicitation of rescue behaviour in Formica cinerea Mayr ants. In the first experiment, we determined the occurrence and characteristics of rescue behaviour directed towards nest mates with impaired mandibular gland communication. We did not observe any difference in rescue behaviour directed towards individuals who were untreated, treated with paint over the mandibles, or sham-treated with paint over the thorax. In the second experiment, we determined whether rescue behaviour would occur towards dummy ants coated with the contents of the mandibular glands. Compared with the control untreated nest mates, we found that rescue behaviour was not directed towards either the untreated dummy ants or the dummy ants covered with crushed mandibular glands. Our results indicated that the “call for help” signal does not originate from the mandibular glands. Therefore, we propose that gaster-tip glands represent a plausible alternative source of rescue-eliciting pheromone(s) for the F. cinerea ants examined in this study.

Honeybee workers with higher reproductive potential live longer lives

ABSTRACT Social insects, especially honeybees, have received much attention in comparative gerontology because of their peculiar and flexible ageing patterns that differ across genetically similar individuals. The longevity of honeybee individuals varies and depends on patterns of gene expression during development; females developing into reproductive individuals (queens) live longer than facultatively sterile workers. Here, we show that rebel workers, which develop under queenless conditions after swarming and have high reproductive potential, live approximately 4 days longer in hives and approximately 3 days longer in cages than individuals that develop in queenright colonies and have lower reproductive potential; this difference in longevity occurs in both free‐flying and caged workers. Moreover, we show that both rebel and normal workers live longer when their ovaries contain more ovarioles. Longer‐living rebel workers can benefit the colony because they can fill the generation gap that emerges between workers after queen exchange during swarming. Our findings provide novel evidence that the fecundity of workers in a social insect colony impacts their intrinsic longevity. HighlightsRebel honeybee workers have higher reproductive potential than normal workers.Rebel workers have a longer lifespan under both caged and free‐flying conditions.The reproductive potential of both types of workers influences their longevity.Longer‐living rebel workers can fill the generation gap after swarming.

Thermal dependence of trap building in predatory antlion larvae (Neuroptera: Myrmeleontidae)

Trap-building predators remain under strong selection from thermal microenvironments. To address how soil temperature and body size affect trap building, we conducted a laboratory experiment using larvae of the antlion Myrmeleon bore at six ecologically relevant temperatures. Larger larvae built larger traps, and warmer soil led to more and larger traps. Body mass did not alter the dependence of trap building on temperature. Our results suggest that the physiological capacity of antlion larvae, which is affected by larval size and body temperature, is the major determinant of trap building. This effect should be considered when assessing interactions between antlions and prey.

Honeybees show adaptive reactions to ethanol exposure

The honeybee is being developed as a simple invertebrate model for alcohol-related studies. To date, several effects of ethanol consumption have been demonstrated in honeybees, but the tolerance effect, one of the hallmarks of alcohol overuse, has never been shown. Here, we confirm our hypothesis that the response to ethanol (in terms of motor impairment) is lower in bees that have previously experienced intoxication than in bees encountering ethanol for the first time, indicating that the chronic tolerance effect occurs in honeybees. Furthermore, we investigated the basis of this effect and found that it likely results from conditioned compensatory responses to cues associated with ethanol delivery. Our findings significantly improve our understanding of the suitability of honeybees as models for alcoholism-related research and underline the first and foremost function of all conditioned reactions – their adaptive value.

Honeybee rebel workers invest less in risky foraging than normal workers

In eusocial insect colonies, workers have individual preferences for performing particular tasks. Previous research suggests that these preferences might be associated with worker reproductive potential; however, different studies have yielded inconsistent results. This study constitutes the first comparison of foraging preferences between genetically similar normal and rebel honeybee workers, which present different reproductive potential. We found that rebels, which have a higher reproductive potential than normal workers, displayed a delayed onset of foraging and a stronger tendency to collect nectar compared with normal workers. These results support the hypothesis that workers with high reproductive potential invest more in their own egg laying and avoid risky tasks such as foraging. In contrast, the results do not support the hypothesis that reproductive workers initiate foraging earlier in life than normal workers and specialize in pollen foraging.