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Responding appropriately during the first predatory attack in life is often critical for survival. In many social species, naive juveniles acquire this skill from conspecifics, but its fitness consequences remain virtually unknown. Here we experimentally demonstrate how naive juvenile Siberian jays (Perisoreus infaustus) derive a long-term fitness benefit from witnessing knowledgeable adults mobbing their principal predator, the goshawk (Accipiter gentilis). Siberian jays live in family groups of two to six individuals that also can include unrelated nonbreeders. Field observations showed that Siberian jays encounter predators only rarely, and, indeed, naive juveniles do not respond to predator models when on their own but do when observing other individuals mobbing them. Predator exposure experiments demonstrated that naive juveniles had a substantially higher first-winter survival after observing knowledgeable group members mobbing a goshawk model, increasing their likelihood of acquiring a breeding position later in life. Previous research showed that naive individuals may learn from others how to respond to predators, care for offspring, or choose mates, generally assuming that social learning has long-term fitness consequences without empirical evidence. Our results demonstrate a long-term fitness benefit of vertical social learning for naive individuals in the wild, emphasizing its evolutionary importance in animals, including humans. [ABSTRACT FROM AUTHOR]

Collective behavior emerges from interactions among group members who often vary in their behavior. The presence of just one or a few keystone individuals, such as leaders or tutors, may have a large effect on collective outcomes. These individuals can catalyze behavioral changes in other group members, thus altering group composition and collective behavior. The influence of keystone individuals on group function may lead to trade-offs between ecological situations, because the behavioral composition they facilitate may be suitable in one situation but not another. We use computer simulations to examine various mechanisms that allow keystone individuals to exert their influence on group members. We further discuss a trade-off between two potentially conflicting collective outcomes, cooperative prey attack and disease dynamics. Our simulations match empirical data from a social spider system and produce testable predictions for the causes and consequences of the influence of keystone individuals on group composition and collective outcomes. We find that a group's behavioral composition can be impacted by the keystone individual through changes to interaction patterns or behavioral persistence over time. Group behavioral composition and the mechanisms that drive the distribution of phenotypes influence collective outcomes and lead to trade-offs between disease dynamics and cooperative prey attack. [ABSTRACT FROM AUTHOR]

Fungus-growing ants (Attini) are abundant and diverse, yet only one taxon of flies (Phoridae) and one of wasps (Diapriinae) are known parasitoids, and the biology of most species is not well known. Here we describe the first evidence for an ant parasitoid in the family Chloropidae (Diptera), in which larvae of Pseudogaurax paratolmos Wheeler, new species, parasitize larvae of the ant, Apterostigma dentigerum Wheeler, 1925. Larval flies are solitary ectoparasitoids, each of which attaches to a single ant larva and develops from larva to pupa in ∼2wk, consuming nearly the entire host, and then ecloses as an adult ~1 wk later. Overall parasitism prevalence was 6.8% of 203 nests, and flies were active during both the dry and rainy seasons. Intensity of parasitism ranged from 18.2 to 100% of larvae attacked per parasitized nest. No other species of Apterostigma that nested in the same localities were parasitized by the flies, including A. pilosum (Mayr, 1865) (n = 93 nests) and A. auriculatum (Wheeler, 1925) (n= 10 nests). All immature ants, parasitized or not, as well as immature stages of Pseudogaurax paratolmos, were attended by adult ants that exhibited normal brood care behavior, including covering immatures with mycelia, grooming, and maintaining brood in the fungus garden. [ABSTRACT FROM AUTHOR]

Understanding the selection pressures that have driven the evolution of sterile insect castes has been the focus of decades of intense scientific debate. An amenable empirical test bed for theory on this topic is provided by the sterile-soldier caste of polyembryonic parasitoid wasps. The function of these soldiers has been a source of controversy, with two basic hypotheses emerging: the "brood-benefit" hypothesis that they provide an overall benefit for their siblings and the "sex-ratio-conflict" hypothesis that the soldiers mediate a conflict between brothers and sisters by killing their opposite-sex siblings. Here, we investigate the divergent sex-ratio optima of a female embryo's maternal-origin and paternal-origin genes, to determine the potential for, and direction of, intragenomic conflict over soldiering. We then derive contrasting empirically testable predictions concerning the patterns of genomic imprinting that are expected to arise out of this intragenomic conflict, for the brood-benefit versus the sex-ratio-conflict hypothesis of soldier function. [ABSTRACT FROM AUTHOR]

Transcriptomes provide excellent foundational resources for mechanistic and evolutionary analyses of complex traits. We present a developmental transcriptome for the facultatively eusocial bee Megalopta genalis, which represents a potential transition point in the evolution of eusociality. A de novo transcriptome assembly of Megalopta genalis was generated using paired-end Illumina sequencing and the Trinity assembler. Males and females of all life stages were aligned to this transcriptome for analysis of gene expression profiles throughout development. Gene Ontology analysis indicates that stage-specific genes are involved in ion transport, cell-cell signaling, and metabolism. A number of distinct biological processes are upregulated in each life stage, and transitions between life stages involve shifts in dominant functional processes, including shifts from transcriptional regulation in embryos to metabolism in larvae, and increased lipid metabolism in adults. We expect that this transcriptome will provide a useful resource for future analyses to better understand the molecular basis of the evolution of eusociality and, more generally, phenotypic plasticity. [ABSTRACT FROM AUTHOR]

Abstract: Fungal symbionts that colonize leaf tissue asymptomatically (endophytes) can alter the foraging behaviour of leaf-cutting ants, and decrease the productivity of this herbivore's mutualistic fungal cultivar, Leucocoprinus gongylophorus. This negative effect of endophytes on the ant's cultivar could be the result of direct fungal–fungal interaction or indirect reductions in the quality of leaves, the cultivar's growth substratum. To test for the indirect effects, we measured in vitro growth rates of cultivars in media that contained sterilized leaf extracts from plants with high (E high) and low (E low) endophyte colonization. We found that, opposite to our expectations, cultivars grew significantly faster in E high leaf extracts compared to E low extracts. Our results suggest that endophyte-driven changes in leaf chemistry are a less likely explanation for the observed in vivo reduction in the ant's symbiotic fungal growth and imply that the effect of direct endophyte–cultivar interactions inside nests are potentially more important. [Copyright &y& Elsevier]