William T. Wcislo

Smithsonian Tropical Research Institute, Ciudad de Panamá, Panamá, Panama

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Publications (118)409.77 Total impact

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    K. M. Kapheim · T.-Y. Chan · A. R. Smith · W. T. Wcislo · P. Nonacs
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    ABSTRACT: In eusocial nests, colony task are divided among queens and workers, but how this division of labor develops is unknown for most species. We compared division of labor and aggressive behavior among queens and workers in the facultatively eusocial bee, Megalopta genalis, using nests with established queen-worker pairs and nests in which the incipient worker had recently emerged. We find that the majority of aggression is directed from queens toward workers in both incipient and established relationships. Established workers forage and perform trophallaxis as donors more frequently than queens, but both queens and workers perform trophallaxis as donors when workers are young. Queens spend significantly more time nest guarding than incipient and established workers, perhaps because older workers spend more time foraging and incipient workers spend significantly more time in cells than do queens. Our results show that the development of worker behavior involves dynamic temporal changes in task performance among queens and workers during the 10 days after worker emergence. During this establishment period, queens engage in maternal care by feeding their daughters, but are also aggressive toward them. This may be a mechanism by which queens coerce their daughters into becoming non-reproductive workers. © 2015 International Union for the Study of Social Insects (IUSSI)
    Full-text · Article · Dec 2015 · Insectes Sociaux
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    S. M. Rehan · S. M. Tierney · W. T. Wcislo
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    ABSTRACT: Small carpenter bees (Ceratinini) are a key taxon to understanding the transition from subsocial to social behaviour, as all documented groups are long-lived and tend to their young periodically throughout development, though the behaviour of multiple lineages is little known. This study provides the first evidence for social nesting in three Neotropical species of Ceratina (Ceratinula) from Panama. Social nesting was associated with nest reuse, consistent with the hypothesis of kin associations, and the proportion of nests (per species) that displayed sociality was as follows: C. buscki 5 %; C. rectangulifera 0 %; C. tricolor 6 %; and C. zeteki 23 %. Sociality is always a low-frequency phenomenon in ceratinine bee populations, and generally represents a third or less of the population. The fact that the majority of colonies remain solitary indicates that solitary nesting is adaptive in the studied species. © 2015, International Union for the Study of Social Insects (IUSSI).
    Full-text · Article · Nov 2015 · Insectes Sociaux
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    Emily Baird · Diana C. Fernandez · William T. Wcislo · Eric J. Warrant
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    ABSTRACT: Like their diurnal relatives, Megalopta genalis use visual information to control flight. Unlike their diurnal relatives, however, they do this at extremely low light intensities. Although Megalopta has developed optical specializations to increase visual sensitivity, theoretical studies suggest that this enhanced sensitivity does not enable them to capture enough light to use visual information to reliably control flight in the rainforest at night. It has been proposed that Megalopta gain extra sensitivity by summing visual information over time. While enhancing the reliability of vision, this strategy would decrease the accuracy with which they can detect image motion—a crucial cue for flight control. Here, we test this temporal summation hypothesis by investigating how Megalopta's flight control and landing precision is affected by light intensity and compare our findings with the results of similar experiments performed on the diurnal bumblebee Bombus terrestris, to explore the extent to which Megalopta's adaptations to dim light affect their precision. We find that, unlike Bombus, light intensity does not affect flight and landing precision in Megalopta. Overall, we find little evidence that Megalopta uses a temporal summation strategy in dim light, while we find strong support for the use of this strategy in Bombus.
    Full-text · Article · Oct 2015 · Frontiers in Physiology
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    Beryl M Jones · William T Wcislo · Gene E Robinson
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    ABSTRACT: 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. Copyright © 2015 Author et al.
    Full-text · Article · Aug 2015 · G3-Genes Genomes Genetics
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    A. E. Quiñones · W. T. Wcislo
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    ABSTRACT: As a result of different brood cell provisioning strategies, nest-making insects may differ in the extent to which adults regularly provide extended parental care to their brood beyond nest defense. Mass-provisioning species cache the entire food supply needed for larval development prior to the oviposition and typically seal the brood cell. It is usually assumed that there is no regular contact between the adult(s) and brood. Here, we show that the bee, Megalopta genalis, expresses a form of cryptic brood care, which would not be observed during normal development. Following experimental injections of different provisioning materials into brood cells, foundresses reopened manipulated cells and the brood were aborted in some cases, implying that the foundresses assessed conditions within the cells. In aborted cells, foundresses sometimes laid a second egg after first removing dead larvae, previously stored pollen and contaminants. Our results show that hygienic brood care can be cryptic and hence may be more widespread than previously believed, lending support to the hypothesis that extended parental care is a preadaptation toward eusociality. Electronic supplementary material The online version of this article (doi:10.1007/s00040-015-0409-3) contains supplementary material, which is available to authorized users.
    Full-text · Article · Aug 2015 · Insectes Sociaux
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    ABSTRACT: Plants host a vast diversity of fungal symbionts inside their tissues that live in close proximity with each other to form rich and dynamic communities. Although endophytes can affect plant-herbivore interactions in several ways, it is still not known to what extent such effects are influenced by the properties of endophyte communities or by particular species traits. Here we compared the effects of high versus low foliar fungal endophyte diversity on the preferences of laboratory and wild colonies of leaf-cutting ants. We found that when endophyte densities were high, the ants responded similarly to leaves hosting one endophyte species, Colletotrichum tropicale, or those hosting a species-rich endophyte community. Results were also consistent when comparing the laboratory versus wild ant colonies. We discuss the significance of these results with respect to the ecological effects of plant-endophyte interactions in natural and agricultural ecosystems.
    No preview · Article · Jul 2015 · Current science
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    ABSTRACT: Fungus-farming ant colonies vary four to five orders of magnitude in size. They employ compounds from actinomycete bacteria and exocrine glands as antimicrobial agents. Atta colonies have millions of ants and are particularly relevant for understanding hygienic strategies as they have abandoned their ancestors' prime dependence on antibiotic-based biological control in favour of using metapleural gland (MG) chemical secretions. Atta MGs are unique in synthesizing large quantities of phenylacetic acid (PAA), a known but little investigated antimicrobial agent. We show that particularly the smallest workers greatly reduce germination rates of Escovopsis and Metarhizium spores after actively applying PAA to experimental infection targets in garden fragments and transferring the spores to the ants' infrabuccal cavities. In vitro assays further indicated that Escovopsis strains isolated from evolutionarily derived leaf-cutting ants are less sensitive to PAA than strains from phylogenetically more basal fungus-farming ants, consistent with the dynamics of an evolutionary arms race between virulence and control for Escovopsis, but not Metarhizium. Atta ants form larger colonies with more extreme caste differentiation relative to other attines, in societies characterized by an almost complete absence of reproductive conflicts. We hypothesize that these changes are associated with unique evolutionary innovations in chemical pest management that appear robust against selection pressure for resistance by specialized mycopathogens. © 2015 The Author(s) Published by the Royal Society. All rights reserved.
    Full-text · Article · Apr 2015 · Proceedings of the Royal Society B: Biological Sciences
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    ABSTRACT: One of the hallmarks of eusociality is that workers forego their own reproduction to assist their mother in raising siblings. This seemingly altruistic behaviour may benefit workers if gains in indirect fitness from rearing siblings outweigh the loss of direct fitness. If worker presence is advantageous to mothers, however, eusociality may evolve without net benefits to workers. Indirect fitness benefits are often cited as evidence for the importance of inclusive fitness in eusociality, but have rarely been measured in natural populations. We compared inclusive fitness of alternative social strategies in the tropical sweat bee, Megalopta genalis, for which eusociality is optional. Our results show that workers have significantly lower inclusive fitness than females that found their own nests. In mathematical simulations based on M. genalis field data, eusociality cannot evolve with reduced intra-nest relatedness. The simulated distribution of alternative social strategies matched observed distributions of M. genalis social strategies when helping behaviour was simulated as the result of maternal manipulation, but not as worker altruism. Thus, eusociality in M. genalis is best explained through kin selection, but the underlying mechanism is likely maternal manipulation. © 2015 The Author(s) Published by the Royal Society. All rights reserved.
    Full-text · Article · Mar 2015 · Proceedings of the Royal Society B: Biological Sciences
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    ABSTRACT: Group size in both multicellular organisms and animal societies can correlate with the degree of division of labour. For ants, the task specialization hypothesis (TSH) proposes that increased behavioural specialization enabled by larger group size corresponds to anatomical specialization of worker brains. Alternatively, the social brain hypothesis proposes that increased levels of social stimuli in larger colonies lead to enlarged brain regions in all workers, regardless of their task specialization. We tested these hypotheses in acacia ants (Pseudomyrmex spinicola), which exhibit behavioural but not morphological task specialization. In wild colonies, we marked, followed and tested ant workers involved in foraging tasks on the leaves (leaf-ants) and in defensive tasks on the host tree trunk (trunk-ants). Task specialization increased with colony size, especially in defensive tasks. The relationship between colony size and brain region volume was task-dependent, supporting the TSH. Specifically, as colony size increased, the relative size of regions within the mushroom bodies of the brain decreased in trunk-ants but increased in leaf-ants; those regions play important roles in learning and memory. Our findings suggest that workers specialized in defence may have reduced learning abilities relative to leaf-ants; these inferences remain to be tested. In societies with monomorphic workers, brain polymorphism enhanced by group size could be a mechanism by which division of labour is achieved. © 2015 The Author(s) Published by the Royal Society. All rights reserved.
    No preview · Article · Feb 2015 · Proceedings of the Royal Society B: Biological Sciences
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    ABSTRACT: One of the key features of eusociality is the seemingly altruistic behavior of workers who forego their own reproduction to assist their mother in raising siblings. This behavior may be adaptive if gains in indirect fitness from rearing siblings outweigh the loss of direct fitness. If the presence of workers is sufficiently advantageous to mothers, however, worker fitness may not be the primary driver of eusocial evolution. This distinction is important, because indirect fitness benefits are often cited as prima facie evidence for the importance of kin selection in eusociality, but suitably large indirect fitness gains have rarely been demonstrated in natural populations. Here we compare the inclusive fitness of alternative social strategies in the tropical sweat bee, Megalopta genalis, for which eusocial nesting is optional. We show that inclusive fitness is similar among reproductive females with and without workers, but workers in eusocial nests have significantly lower inclusive fitness than would have been expected if they departed to found their own nests. In support for the role of kin selection in eusocial evolution, mathematical simulations based on M. genalis field data found eusociality cannot evolve with reduced intra-nest relatedness. In addition, the simulated distribution of alternative social strategies matched observed distributions of M. genalis social strategies when simulated as a maternal trait (i.e., manipulation), but not when helping behavior was coded as a worker trait (i.e., altruism). Thus, eusociality in M. genalis is best explained through kin selection, but the mechanism being selected is likely maternal manipulation.
    No preview · Conference Paper · Nov 2014
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    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 (Ehigh) and low (Elow) endophyte colonization. We found that, opposite to our expectations, cultivars grew significantly faster in Ehigh leaf extracts compared to Elow 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.
    Full-text · Article · Apr 2014 · Fungal Ecology
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    ABSTRACT: Social transmission and host developmental stage are thought to profoundly affect the structure of bacterial communities associated with honey bees and bumble bees, but these ideas have not been explored in other bee species. The halictid bees Megalopta centralis and Megalopta genalis exhibit intra-population social polymorphism, which we exploit to test whether bacterial communities differ by host social structure, developmental stage, or host species. We collected social and solitary Megalopta nests, and sampled bees and nest contents from all stages of host development. To survey these bacterial communities, we used 16S rRNA gene 454 pyrosequencing. We found no effect of social structure, but found differences by host species and developmental stage. Wolbachia prevalence differed between the two host species. Bacterial communities associated with different developmental stages appeared to be driven by environmentally acquired bacteria. A Lactobacillus kunkeei clade bacterium that is consistently associated with other bee species was dominant in pollen provisions and larval samples, but less abundant in mature larvae and pupae. Foraging adults appeared to often reacquire L. kunkeei clade bacteria, likely while foraging at flowers. Environmental transmission appears to be more important than social transmission for Megalopta bees at the cusp between social and solitary behavior. This article is protected by copyright. All rights reserved.
    Full-text · Article · Mar 2014 · FEMS Microbiology Ecology
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    ABSTRACT: Ant social parasites evolve adaptive relationships with their hosts. Theoretically, coevolution predicts strong selection to maximize fitness of the parasite that minimizes costs to its host, which potentially leads to the evolution of benign interactions. We studied the demographic and behavioral traits of the ant social parasite Megalomyrmex symmetochus (Solenopsidini), an agro-predator that feeds on larvae and fungal garden products of their host, Sericomyrmex amabilis (Attini). Based on demographic data from 15 parasitized colonies, the proportion of parasitic workers to those of the host is 1:2. Moreover, defensive prophylactic behaviors observed during infections with Metarhizium brunneum, a generalist entomopathogen, and Escovopsis, a specialized fungal garden parasite, showed that S. amabilis works extensively to remove and control fungal infections, in contrast to M. symmetochus. M. symmetochus, however, performed intraspecific allogrooming during infections with Escovopsis and M. brunneum, suggesting that they may recognize fungal pathogens and indirectly limit dispersion of spores. Our results indicate that M. symmetochus did not have a strong role in maintaining a hygienic nest.
    Full-text · Article · Feb 2014 · Insectes Sociaux
  • Courtney Rockenbach · Chris Reid · William Wcislo · Simon Garnier
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    ABSTRACT: Leaf-cutter ants Atta colombica form supply chains to move leaf fragments from their foraging sites to the nest of the colony. The ants then mulch these leaf fragments into substrate for the fungus they grow for food. The overall efficiency of this transportation system depends on the dynamic integration of the supply rate of the cutter ants, the layout of the trail network and the processing rate of the workers remaining at the nest. In this study, we investigated the contribution of leaf-caches (way stations that can form near the production sites, along the trail, and near the nest) to the foraging efficiency of natural colonies. In this study we tested to see if these leaf-caches were used as buffers to equalize flow rate when leaf delivery and processing rate were mismatched. The nutritional quality of the leaves is important for fungal growth. Therefore, we also tested the cycling of leaves within caches to investigate whether fresh leaves are prioritized and how this occurs. Results from this study have important implications for our understanding of the caching behavior of leaf-cutting ants and the optimization of self-organizing supply chains.
    No preview · Conference Paper · Nov 2013
  • Peter Marting · Stephen C. Pratt · William Wcislo
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    ABSTRACT: Over the past decade, there has been growing evidence that non-human animals maintain individual personalities, or sets of behavioral tendencies that are consistent across contexts, a phenomenon termed behavioral syndromes. This framework shifts the classic approach to behavioral ecology by implying limited behavioral flexibility. To account for this, behavioral traits should be viewed across multiple situations instead of in isolated contexts, aiming to quantify individual variation instead of ignoring it. Studies in a broad range of taxa (e.g., birds, fish, and spiders) have described behavioral syndromes in individuals, but collective behavioral syndromes of highly social groups are largely uncharted. These groups provide an opportune system for studying the proximate and ultimate mechanisms driving behavioral syndromes because colonies can be easily manipulated and deconstructed. We tested for the existence of collective behavioral syndromes in ant colonies of an arboreal Azteca ant associated with Cecropia trees. Preliminary evidence shows consistent variation in defensive behavior among colonies, suggesting collective behavioral syndromes may occur. Pursuing this, we presented colonies with a series of behavioral tests to assess five colony-level behavioral traits: defensive aggression, exploratory tendency, prey capture efficiency, response to leaf damage, and patrolling behavior. This work sets up future studies that will focus on how the personalities of a colony’s workers influence its collective personality, environmental effects on colony personality, and fitness consequences of behavioral type.
    No preview · Conference Paper · Nov 2013
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    ABSTRACT: Associative color learning has been demonstrated to be very poor using restrained European honey bees unless the antennae are amputated. Consequently, our understanding of proximate mechanisms in visual information processing is handicapped. Here we test learning performance of Africanized honey bees under restrained conditions with visual and olfactory stimulation using the proboscis extension response (PER) protocol. Restrained individuals were trained to learn an association between a color stimulus and a sugar-water reward. We evaluated performance for "absolute" learning (learned association between a stimulus and a reward) and "discriminant" learning (discrimination between two stimuli). Restrained Africanized honey bees (AHBs) readily learned the association of color stimulus for both blue and green LED stimuli in absolute and discriminatory learning tasks within 7 presentations, but not with violet as the rewarded color. Additionally, 24-hour memory improved considerably during the discrimination task, compared to absolute association (15%-55%). We found that antennal amputation was unnecessary and reduced performance in AHBs. Thus color learning can now be studied using the PER protocol with intact AHBs. This finding opens the way toward investigating visual and multimodal learning with application of neural techniques commonly used in restrained honey bees.
    Full-text · Article · Sep 2013 · Journal of Experimental Biology
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    Catalina Estrada · William T Wcislo · Sunshine A Van Bael
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    ABSTRACT: Fungal symbionts that live asymptomatically inside plant tissues (endophytes) can influence plant–insect interactions. Recent work has shown that damage by leaf-cutting ants, a major Neotropical defoliator, is reduced to almost half in plants with high densities of endophytes. We investigated changes in the phenotype of leaves that could influence ants' behavior to result in the reduction of foliar damage. We produced cucumber seedlings with high and low densities of one common endophyte species, Colletotrichum tropicale. We used the leaves in bioassays and to compare chemical and physical leaf characteristics important for ants' food selection. Ants cut about one-third more area of cucumber leaves with lower densities of endophytes and removed c. 20% more paper disks impregnated with the extracts of those leaves compared with leaves and disks from plants hosting the fungus. Colletotrichum tropicale colonization did not cause detectable changes in the composition of volatile compounds, cuticular waxes, nutrients or leaf toughness. Our study shows that endophytes changed leaf chemistry and suggests that compounds with relative low volatility released after leaf wounding are a major factor influencing foraging decisions by ants when choosing between plants with low or high endophyte loads.
    Full-text · Article · Apr 2013 · New Phytologist
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    ABSTRACT: The genus Mycocepurus is a phylogenetically basal attine ant, so studies of its biology may provide insight into the evolution of behaviours associated with fungus‐growing that characterize the tribe Attini. Mycocepurus smithii from Puerto Rico produces sexual females from July to September, but no males were observed in 2 years of observations, confirming previous observations elsewhere. Colonies were founded between July and August and most nests were haplometrotic (85% of 74 nests). After excavating a tunnel and small chamber, a foundress queen inserted her fore wings into the ceiling and used the wing surfaces as a platform on which the incipient fungal garden was grown. Foundresses foraged for substrate to grow the fungus garden. Growth of incipient colonies was slow: the first workers emerged 2–5 months after colony founding and, after 8 months, colonies contained on average only a single worker.
    Full-text · Article · Feb 2013 · Journal of Natural History
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    ABSTRACT: The reproductive (queen) and nonreproductive (worker) castes of eusocial insect colonies are a classic example of insect polyphenism. A complementary polyphenism may also exist entirely among females in the reproductive caste. Although less studied, reproductive females may vary in behavior based on size-associated attributes leading to the production of daughter workers. We studied a bee with flexible social behavior, Megalopta genalis, to better understand the potential of this polyphenism to shape the social organization of bee colonies and, by extension, its role in the evolution of eusociality. Our experimental design reduced variation among nest foundresses in life history variables that could influence reproductive decisions, such as nesting quality and early adulthood experience. Within our study population, approximately one third of M. genalis nests were eusocial and the remaining nests never produced workers. Though they do not differ in survival, nest-founding females who do not attempt to produce workers (which we refer to as the solitary phenotype) are significantly smaller and become reproductive later than females who attempt to recruit workers (the social phenotype). Females with the social phenotype are more likely to produce additional broods but at a cost of having some of their first offspring become nonreproductive workers. The likelihood of eusocial organization varies with body size across females of the social phenotype. Thus, fitness consequences associated with size-based plasticity in foundress behavior has colony level effects on eusociality. The potential for size-based polyphenisms among reproductive females may be an important factor to consider in the evolutionary origins of eusociality.
    No preview · Article · Feb 2013 · Behavioral Ecology and Sociobiology
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    ABSTRACT: Local environmental conditions can facilitate or preclude the development of eusocial colonies in insects that facultatively express behavioural-caste polyphenism. To explore how environmental variability relates to the expression of social behaviour, we collected 120 nests of the facultatively social sweat bee, Megalopta genalis (Halictidae: Augochlorini), along a nearly twofold rainfall gradient in central Panama. Brood rearing activity of bees in seasonal neotropical forests should track flowering phenologies, which are typically set by rainfall and phylogenetic patterns. Nests were collected at roughly similar times of year from three sites comprising wet, moist and dry lowland tropical forests. There were significant differences in ovarian development, brood production and body size across sites for some comparisons, but no effect on the proportion of social colonies collected at each site. Results show that phenotypes of M. genalis relevant to social behaviour (ovarian development, brood production, body size) may be responsive to variation in local environment over distances of <20 km.
    Full-text · Article · Jan 2013 · Insectes Sociaux

Publication Stats

3k Citations
409.77 Total Impact Points

Institutions

  • 1994-2015
    • Smithsonian Tropical Research Institute
      Ciudad de Panamá, Panamá, Panama
  • 1987-2008
    • University of Kansas
      • Department of Ecology and Evolutionary Biology
      Lawrence, Kansas, United States
  • 1992-1999
    • Cornell University
      • Department of Entomology
      Итак, New York, United States
  • 1995
    • The University of Arizona
      Tucson, Arizona, United States