Funded by the Univ. of Washington Royalty Research Fund

Population genetics of Neotropical army ants (Ecitoninae)

Collaborators and students: Dr. Anjali Kumar (Field Instructor, Council for International Educational Exchange), Dr. Kerry Naish (Univ. of Washington Aquatic & Fishery Sciences), Tom Soare (Univ. of Washington Animal Behavior PhD student)

Our behavioral and ecological data show that army ants can be affected by changes in elevation, and by human disturbances such as forest clearing and forest fragmentation. Temperature and other abiotic gradients appear to play a strong role in army ant distributions and movement patterns. However, army ant species differ in their responses to habitat variation. We are particularly interested in differences between above-ground raiding species (Eciton burchellii) and underground raiding species (Labidus coecus). We are scoring both nuclear (microsatellites) and mitochondrial DNA markers of genetic variability to quantify population genetic structure in army ants, with the aim of identifying ecological variables that affect population genetic structure. The microsatellite data, which include both maternal and paternal contributions to colony genetics, will complement the patterns seen in the maternally inherited mtDNA markers. Maternal inheritance patterns may be especially relevant in these ants: they have wingless queens, and colonies reproduce by splitting the work force, part of which literally walks away with a new queen. Males are winged and potentially move genes over longer distances. Our microsatellite data confirm that army ant queens have very high mating frequencies.

Mating frequency and systematics of ants in the genus Simopelta

Collaborators: Dr. Daniel Kronauer (Harvard), Dr. Alex Wild (Univ. of Illinois)

Simopelta is a Neotropical genus of poneromorph ants that show an amazing degree of convergence in behavior and social structure with true army ants (Ecitoninae): Simopelta raid in groups, specialize by raiding other social insects, move regularly among temporary bivouac sites, and have large-bodied wingless queens. Dan is developing microsatellite markers to test for multiple mating

Alex is sequencing DNA to estimate evolutionary relationships among Simopelta species.

Funded by the US National Science Foundation

Individual differences in brain-behavior relationships in paper wasps

Collaborators and students: Dr. Theresa Jones (Univ. of Texas), Yamile Molina (Univ. of Washington Animal Behavior PhD student)

The main goal of this project is to assess whether neural plasticity in the brain, particularly in the mushroom bodies, plays a functional role in social wasp workers' task performance. In addition to measuring gross brain region volumes, We use stereological microscopy techniques to measure the volume of functionally distinct regions of paper wasp brains, and test whether the size of different brain regions corresponds to individual differences in age, social rank, and task performance. We use Golgi staining methods to quantify changes in dendritic processes of brain neurons that may underlie changes in neuropil volume.

References:

Molina, Y. & S. O'Donnell. 2007. Mushroom body volume is related to social aggression and ovary development in the paper wasp Polistes instabilis. Brain Behavior and Evolution 70: 137-144.

O'Donnell, S., N.A. Donlan, & T.A. Jones. 2007. Developmental and dominance-associated differences in mushroom body structure in the paper wasp Mischocyttarus mastigophorus. Developmental Neurobiology 67: 39-46.

O'Donnell, S., N.A. Donlan, & T.A. Jones. 2004. Mushroom body structural plasticity is associated with temporal polyethism in eusocial wasp workers. Neuroscience Letters 356: 159-162

Evolution of brain architecture in social paper wasps

Collaborators and students: Dr. Sara Farris (Univ. of West Virginia), Yamile Molina (Univ. of Washington Animal Behavior PhD student)

We are using statistical methods that account for the effects of evolutionary relatedness (phylogeny) on correlated evolution among traits to test whether brain architecture has evolved along with social structure in paper wasps. Paper wasp phylogeny is well characterized at the genus level, and paper wasp exhibit a wide array of social complexities. Species vary in colony size, mode of colony founding, nest architecture, and in the degree of queen-worker caste differentiation. Preliminary data suggest that behavioral and developmental factors, such as nest architecture and caste determination, have affected the evolution of the amount of investment in functionally distinct brain regions.

Caste and developmental differences in brain structure of dampwood termites (Zootermopsis)

Funded by an REU supplement from the National Science Foundation

Student: Kayla Helem (Univ. of Washington Biology major)

Zootermopsis are fascinating examples of developmental plasticity: nest mate individuals can develop along a number of different pathways with distinct body designs and behaviors, and development is responsive to colony social conditions. Kayla's independent project is exploring how termite's brain change as they age and molt among different body designs.

Caste differences in brain structure of Neotropical army ants (Ecitoninae)

Student: Yamile Molina (Univ. of Washington Animal Behavior PhD student)

Army ant workers show striking differences in body size and shape, with the greatest differences occurring in the head region. We are measuring the relative sizes of brain structures in different worker morphological castes of the same species, and comparing different species, with the aim of testing whether worker caste behavioral repertoires and body plans are associated with differences in brain structure.

Role of dominance interactions in regulating task performance in paper wasp colonies

Dominance is based on aggressive social interactions that influence individuals' access to resources. It has long been recognized that dominance among female social wasps plays a role in governing the separation between reproductive roles (queens) and sterile, helping roles (workers). I am working on several genera of independent-founding (Polistes and Mischocyttarus) and swarm-founding (Polybia) social wasps to assess how dominance interactions within the worker force influence task performance and non-reproductive division of labor (polyethism). I am particularly interested in the role of adult nutrition in governing social roles.

References:

O'Donnell, S. 2006. Polybia wasp biting interactions recruit foragers following experimental worker removals. Animal Behaviour 71: 709-715.

O'Donnell, S. 2001. Worker biting interactions and task performance in a swarm-founding eusocial wasp (Polybia occidentalis, Hymenoptera: Vespidae). Behavioral Ecology 12: 353-359.

Markiewicz, D.A. & S. O'Donnell. 2001. Social dominance, task performance and nutrition: implications for reproduction in eusocial wasps. Journal of Comparative Physiology A 187: 327-333.

Regulation of division of labor in bumble bees, Bombus bifarius and B. huntii

Collaborator: Dr. Robin Foster (Univ. of Puget Sound)

We are examining factors that influence individual behavioral differences among nest mate workers in bumble bees. We have found that workers differ in their propensities to collect nectar vs. pollen when foraging, and that they also differ in their probabilities of performing thermoregulatory behaviors to regulate internal nest temperature. Our approach is to understand how extrinsic environmental cues and intrinsic differences (e.g., physiology and body size) interact to affect individual behavioral output. We are especially interested in using bumble bees to generate and test threshold of response models for the regulation of task performance. We are also exploring the role of aggressive interactions in regulating division of labor, and how this role may change over the course of colony development.

References:

Gardner, K.E., R.L. Foster, & S. O'Donnell. 2007. Experimental analysis of worker division of labor in bumblebee nest thermoregulation (Bombus huntii, Hymenoptera: Apidae). Behavioral Ecology and Sociobiology 61: 783-792.

Foster, R.L., A. Brunskill, D. Verdirame, & S. O'Donnell. 2004. Reproductive physiology, dominance interactions, and division of labour among bumble bee workers. Physiological Entomology 29: 327-334.

O'Donnell, S. & R.L. Foster. 2001. Thresholds of response in nest thermoregulation by worker bumble bees, Bombus bifarius nearcticus (Hymenoptera: Apidae). Ethology 107: 387-399.

O'Donnell, S., M. Reichardt, & R.L. Foster. 2000. Individual and colony factors in bumble bee division of labor (Bombus bifarius nearcticus Handl, Hymenoptera: Apidae). Insectes Sociaux 47: 164-170.

Trail and recruitment pheromones of the swarm-raiding army ant Eciton burchellii

Collaborators and students: Gerhard Gries (Simon Fraser Univ. Biological Sciences), Tom Soare (Univ. of Washington Animal Behavior PhD student), Frank Turecek (Univ. of Washington Chemistry)

We will use a combination of analytical chemistry methods (GCMS), sensory physiology (electroantennagram assays), and field behavioral bioassays in a effort to identify the active components of army ant trail and recruitment pheromones.

Caste and species differences in army ant exocrine glands

Student: Sean Tully (Univ. of Washington Honors Psychology major)

The glandular source of trail pheromone has been identified for only one species of Neotropical army ant. As part of his Psychology honors thesis research, Sean is surveying workers from species in all genera of Ecitoninae to assess whether exocrine gland presence and development varies among and within species.

Behavior and ecology of army ants: how climate, elevation, and habitat alteration affect the biology of these top predators

Collaborators: Mike Kaspari (Univ. of Oklahoma), Dr. Anjali Kumar (Field Instructor, Council for International Educational Exchange), John Lattke (Univ. Central de Venezuela), Scott Powell (Univ. of Uberlandia, Brazil)

Army ants (Ecitoninae) are mobile insect societies that conduct mass hunting raids across and under forest leaf litter. They are top predators, and as such likely have an major impact on forest animal community structure. Army ants are akin to such spectacular elements of the Neotropical fauna as jaguars and harpy eagles. We have compared army ant community structure across latitudinal and elevational gradients to assess factors that affect their density, diversity, and ecological impact on prey and commensals. Results from this work suggest that army ant raids occur at astoundingly high rates in lowland primary wet forests, on the order of one raid/square meter/day! Our main approach has been to sample army ant density and diversity at different sites using standardized sampling protocols. By comparing latitudinally separate sites, we showed that army ant species composition changes significantly over regional scales, with implications for their commensals and parasites, including antbirds. Surveys across elevational gradients showed that above ground raiders and subterranean species differ in their responses to forest clearing and elevation.

References:

Kumar, A. & S. O'Donnell. 2007. Fragmentation and elevation effects on bird-army ant interactions in Neotropical montane forest of Costa Rica. Journal of Tropical Ecology 23: 581-590.

O'Donnell, S., J. Lattke, S. Powell, & M. Kaspari. 2007. Army ants in four forests: Geographic variation in raid rates and species abundance. Journal of Animal Ecology 76: 580-589.

O'Donnell, S. & A. Kumar. 2006. Elevational patterns of army ant community composition in tropical montane forest. Ecological Entomology 31: 491-498.

Kaspari, M. & S. O'Donnell. 2003. High rates of army ant raids in the Neotropics and implications for ant colony and community structure. Evolutionary Ecology Research 5: 933-939.

Analyzing how communication affects task allocation

Collaborator: Dr. Susan Bulova O'Donnell

A review of the role of social communication in allocating workers among tasks showed that social insects employ diverse modes of communication to coordinate labor with their colonies. The details of these communicative mechanisms, of the structure of social groups, and of worker responses to social information may all shape the ways that colonies allocate workers among different jobs. We developed an individual-based simulation model to explore how characteristics of social groups (number of group members), details of communicative interactions (the strength of effects on receivers), and cognitive mechanisms (forgetting about past interactions) can influence the recruitment of group members to a new task.

References:

O'Donnell, S. & S.J. Bulova. 2007. Worker connectivity: a review of the design of worker communication systems and their effects on task performance in insect societies. Insectes Sociaux 54: 203-210.

O'Donnell, S. & S.J. Bulova. 2007. Worker connectivity: a simulation model of variation in worker communication and its effects on task performance. Insectes Sociaux 54: 211-218.

Bivouac site selection by army ants

Student: Tom Soare (Univ. of Washington Animal Behavior PhD student)

Army ant colonies are highly mobile, moving among temporary shelters or bivouac sites daily for nearly half of their colony cycle. Tom is developing his PhD thesis topic around the problem of bivouac site selection in army ants. He is interested in self-organization and group decision making as factors in bivouac site selection.

Elevational patterns of species richness and community composition in Neotropical paper wasps (Vespidae)

Collaborators: Dr. Rob Colwell (Univ. of Connecticut), Dr. Anjali Kumar (Field Instructor, Council for International Educational Exchange), Dr. Jack Longino (Evergreen State College)

We used data from the ALAS Biodiversity survey in Costa Rica to assess patterns of elevational changes in the occurrence of eusocial paper wasp species. Samples were collected at a series of different elevations above the La Selva Biological Station in Volcan Barva National Park, using standardized collection methods and sampling effort. We tested for elevational effects on species composition and richness, species turnover, and the relative abundances of different genera. We found strong evidence that swarm-founders were more abundant than independent-founders at all elevations, supporting the hypothesis that SF are more ecologically successful. Wasp species richness declined with elevation, while wasp abundance increased with elevation. We develop the hypothesis that higher predation at lower elevations, particularly by army ants, affects these richness and abundance patterns.

Reference:

Kumar, A., J.T. Longino, R.K. Colwell & S. O'Donnell. 2008 (Published online). Elevational patterns of diversity and abundance of eusocial paper wasps (Vespidae) in Costa Rica. Biotropica. Early View, December 2008.

Elevational and seasonal patterns of species richness and community composition in Neotropical paper wasps (Vespidae) in tropical dry forest

Funded by an REU supplement from the National Science Foundation

Collaborators and students: Dr. Daniel Janzen (Univ. of Pennsylvania), Josephine Rodriguez (Univ. of Illinois Entomology PhD student), Sean Tully (Univ. of Washington Psychology major)

We will replicate the ALAS study with malaise trap samples collected at various elevations on the slopes of Cacao Volcano and in the Santa Rosa sector of the Guanacaste Conservation Area. This study will add an important seasonal component to the data, allowing us to test for temporal changes in tropical paper wasp community composition.

Habitat variation effects on birds attending army ant raids in tropical montane forests

Collaborator: Dr. Anjali Kumar (Field Instructor, Council for International Educational Exchange)

A diverse fauna of birds attend army ant raids in montane tropical forests. The birds obtain food at the swarm raids by capturing small animals that flee from the advancing army ants. The montane attendants are particularly interesting because few or no true antbirds are present in montane forests. We are exploring the possibility that high-fidelity or obligate ant following behavior has evolved in some montane bird species. Montane army ant following birds are affected by elevation and forest fragmentation.

Reference:

Kumar, A. & S. O'Donnell. 2007. Fragmentation and elevation effects on bird-army ant interactions in Neotropical montane forest of Costa Rica. Journal of Tropical Ecology 23: 581-590.

Army ant raid attendance by Nearctic migrant birds in tropical montane forests

Collaborators and students: Dr. Anjali Kumar (Field Instructor, Council for International Educational Exchange), Corina Logan (Cambridge Univ. PhD student)

Among the birds that attend montane army ant raids are several species of long-distance migrants that breed in North America. These include species of thrushes, warblers and vireos. We are using relative abundance estimates from previous mist net studies to assess whether some migrants are specialized as army ant followers.

Bivouac checking by birds that attend army ant raids

Collaborators and students: Dr. Nicola Clayton (Cambridge Univ.), Dr. Anjali Kumar (Field Instructor, Council for International Educational Exchange), Corina Logan (Cambridge Univ. PhD student)

Some birds that specialize as army ant followers engage in elaborate behavior called bivouac checking. These birds visit the temporary resting clusters of a series of army ant colonies in the early morning, apparently assessing the ant's raid activity for that day. We are interested in the expression of this behavior by some montane birds that are not in the true antbird family (Thamnophilidae). We are also interested in the cognitive implications and challenges of bivouac checking for the birds.

Predation on paper wasps by Red-throated Caracaras

Students: Sean McCann (Simon Fraser Univ. Biological Sciences PhD student)

I am collaborating with Sean on part of his thesis work on these amazing birds. Red-throated Caracaras appear to rely heavily on the nests of paper wasps as prey items. We are analyzing video tapes of nestling feedings by a group of adults to identify which genera of paper wasps are collected by the adults.