Conditional indirect genetic effects of caregivers on brood in the clonal raider ant.

Caregivers shape the rearing environment of their young. Consequently, offspring traits are influenced by the genes of their caregivers via indirect genetic effects (IGEs). However, the extent to which IGEs are modulated by environmental factors, other than the genotype of social partners (i.e., intergenomic epistasis), remains an open question. Here we investigate how brood are influenced by the genotype of their caregivers in the clonal raider ant, Ooceraea biroi, a species in which the genotype, age and number of both caregivers and brood can be experimentally controlled. First, we used four clonal lines to establish colonies that differed only in the genotype of caregivers and measured effects on foraging activity, as well as IGEs on brood phenotypes. In a second experiment, we tested whether these IGEs are conditional on the age and number of caregivers. We found that caregiver genotype affected the feeding and foraging activity of colonies, and influenced the rate of development, survival, body size, and caste fate of brood. Caregiver genotype interacted with other factors to influence the rate of development and survival of brood, demonstrating that IGEs can be conditional. Thus, we provide an empirical example of phenotypes being influenced by IGE-by-environment interactions beyond intergenomic epistasis, highlighting that IGEs of caregivers/parents are alterable by factors other than their brood's/offspring's genotype.

Sparse and stereotyped encoding implicates a core glomerulus for ant alarm behavior.

Ants communicate via large arrays of pheromones and possess expanded, highly complex olfactory systems, with antennal lobes in the brain comprising up to ∼500 glomeruli. This expansion implies that odors could activate hundreds of glomeruli, which would pose challenges for higher-order processing. To study this problem, we generated transgenic ants expressing the genetically encoded calcium indicator GCaMP in olfactory sensory neurons. Using two-photon imaging, we mapped complete glomerular responses to four ant alarm pheromones. Alarm pheromones robustly activated ≤6 glomeruli, and activity maps for the three pheromones inducing panic alarm in our study species converged on a single glomerulus. These results demonstrate that, rather than using broadly tuned combinatorial encoding, ants employ precise, narrowly tuned, and stereotyped representations of alarm pheromones. The identification of a central sensory hub glomerulus for alarm behavior suggests that a simple neural architecture is sufficient to translate pheromone perception into behavioral outputs.

DNMT1 mutant ants develop normally but have disrupted oogenesis.

Although DNA methylation is an important gene regulatory mechanism in mammals, its function in arthropods remains poorly understood. Studies in eusocial insects have argued for its role in caste development by regulating gene expression and splicing. However, such findings are not always consistent across studies, and have therefore remained controversial. Here we use CRISPR/Cas9 to mutate the maintenance DNA methyltransferase DNMT1 in the clonal raider ant, Ooceraea biroi. Mutants have greatly reduced DNA methylation, but no obvious developmental phenotypes, demonstrating that, unlike mammals, ants can undergo normal development without DNMT1 or DNA methylation. Additionally, we find no evidence of DNA methylation regulating caste development. However, mutants are sterile, whereas in wild-type ants, DNMT1 is localized to the ovaries and maternally provisioned into nascent oocytes. This supports the idea that DNMT1 plays a crucial but unknown role in the insect germline.

The pupal moulting fluid has evolved social functions in ants.

Insect societies are tightly integrated, complex biological systems in which group-level properties arise from the interactions between individuals1-4. However, these interactions have not been studied systematically and therefore remain incompletely known. Here, using a reverse engineering approach, we reveal that unlike solitary insects, ant pupae extrude a secretion derived from the moulting fluid that is rich in nutrients, hormones and neuroactive substances. This secretion elicits parental care behaviour and is rapidly removed and consumed by the adults. This behaviour is crucial for pupal survival; if the secretion is not removed, pupae develop fungal infections and die. Analogous to mammalian milk, the secretion is also an important source of early larval nutrition, and young larvae exhibit stunted growth and decreased survival without access to the fluid. We show that this derived social function of the moulting fluid generalizes across the ants. This secretion thus forms the basis of a central and hitherto overlooked interaction network in ant societies, and constitutes a rare example of how a conserved developmental process can be co-opted to provide the mechanistic basis of social interactions. These results implicate moulting fluids in having a major role in the evolution of ant eusociality.

Avispas de la vegetación arbórea en el Parque Nacional Natural Gorgona, Pacífico de Colombia / Wasps of the arboreal vegetation in the Gorgona National Natural Park, Pacific of Colombia

Wasps from the arboreal vegetation in Gorgona National Natural Park, Colombian Pacific. Studies of Colombian Hymenoptera are incipient, fragmented and there is no comprehensive study about its size and composition. We know that the guild of hymenopteran parasitoids is the richest in species and that they are common and abundant in all terrestrial ecosystems, acting as regulators of populations of other insects. Studies in Gorgona National Natural Park have mostly focused on the natural history and identification of Formicidae and Apidae. This work was directed toward the identification of other hymenopteran species associated with its tropical rain forest. In November 2007, 16 trees were sampled by fogging with a biodegradable pyrethroid insecticide applied from 1m above the ground to the canopy. We found 641 individuals (45% identified to subfamily and 28% to genera) from seven superfamilies, 20 families and 118 morphospecies. Chalcidoidea was the most representative superfamily, Eulophidae the most diverse family and Braconidae the numerically dominant family. The sampling efficiency was 71% and 166 species are estimated to exist in the island. Approximately 71% of the estimated species were captured during this study. We report 12 genera new for the island. Rev. Biol. Trop. 62 (Suppl. 1): 307-315. Epub 2014 February 01.

A pesar de la reconocida riqueza de Colombia, los estudios de la fauna de himenópteros son muy incipientes, fragmentarios y no hay revisiones de base que muestren el tamaño y composición de la fauna del país. Los himenópteros parasitoides son muy comunes y abundantes en todos los ecosistemas terrestres, actuando como reguladores de poblaciones de otros insectos. Este trabajo fue dirigido hacia la identificación de especies asociadas al dosel del bosque húmedo tropical del Parque Nacional Natural Gorgona, ecosistema insular ubicado en la parte sur del Pacífico colombiano, con el propósito de ampliar el conocimiento sobre este orden. En noviembre de 2007, se muestrearon 16 árboles mediante la técnica de nebulización, utilizando un insecticida piretroide biodegradable aplicado desde 1m sobre el nivel del suelo hasta el dosel. Se examinaron 641 individuos (identificados 45% a subfamilias y 28% a género) pertenecientes a siete superfamilias, 20 familias y 118 morfoespecies, siendo Chalcidoidea la superfamilia más representativa, Eulophidae la familia más diversa y Braconidae la familia dominante con el mayor número de ejemplares colectados. Se reportan 12 géneros nuevos para la isla, ampliando su rango de distribución y posicionando este estudio como el primero enfocado en este gremio de Hymenoptera en el parque.

Hormigas arbóreas del Parque Nacional Natural Gorgona (Pacífico de Colombia) / Arboreal ants of the Gorgona National Natural Park (Pacific of Colombia)

Arboreal ants of Gorgona National Park (Pacific of Colombia). Despite the strong microclimatic fluctuations, scarcity of nesting sites and unpredictable prey availability in open environments, ants are the dominant invertebrates in the tropical forest canopy. This study focused on the arboreal ants in Gorgona National Park, Colombia, a rainforest ecosystem (27ºC, 6 000mm average annual rainfall). In November 2007, 16 trees were sampled by fogging them with a biodegradable pyrethroid insecticide in four levels between 1 and 15 m above the understory vegetation. We found 53 species of Formicidae (24 genera and six subfamilies): two subfamilies had the most species: Formicinae (20 species) and Myrmicinae (17). The most abundant were arboreal species of Azteca, Dolichoderus (D. bispinosus and D. lutosus), Camponotus (C. atriceps, C. claviscapus, C. championi, C. excisus) and Crematogaster (C. brasiliensis, C. carinata, C. curvispinosa). Some species that are common at ground level (Wasmannia auropunctata and Camponotus sericeiventris) were collected up to a height of 15 m. We remark the capture of Nesomyrmex pittieri, Crematogaster stolli, Cephalotes basalis, Anochetus bispinosus and Stigmatomma mystriops, species rarely found using conventional methods. Rev. Biol. Trop. 62 (Suppl. 1): 277-287. Epub 2014 February 01.

Este trabajo se enfocó en el conocimiento de la mirmecofauna arbórea de Gorgona, ecosistema insular de la zona de vida de bosque lluvioso tropical (27ºC, 6 000mm de precipitación promedio anual). En noviembre de 2007 se muestrearon 16 árboles mediante la técnica de nebulización usando un insecticida piretroide biodegradable, aplicado en dirección al dosel, desde cuatro alturas diferentes, entre 1 y 15m por encima de la vegetación del sotobosque. Se encontraron 53 especies de Formicidae pertenecientes a 24 géneros y seis subfamilias, sobresaliendo por su riqueza las Formicinae (20 especies) y Myrmicinae (17). Por su abundancia, se destacaron especies arbóreas de los géneros Azteca, Dolichoderus (D. bispinosus y D. lutosus), Camponotus (C. atriceps, C. claviscapus, C. championi, C. excisus) y Crematogaster (C. brasiliensis, C. carinata, C. curvispinosa). Algunas especies que son muy comunes a nivel del suelo (Wasmannia auropunctata y Camponotus sericeiventris), fueron colectadas a más de 15m de altura. Se resalta la captura de Nesomyrmex pittieri, Crematogaster stolli, Cephalotes basalis, Anochetus bispinosus y Stigmatomma mystriops que usualmente no se detectan en muestreos comunes.

Especies de hormigas del suelo en el Parque Nacional Natural Gorgona, Pacífico Colombiano / Soil ant species in Gorgona Island, Colombian Pacific

Soil ant species in Gorgona Island, Colombian Pacific. Gorgona is one of the two insular areas of the Colombian tropical rain forest at the Pacific and is amongst the most diverse biogeographic regions of the world, the Choco. This study compiles information on ant species from published (1991) and unpublished (2006) studies and provides new records for ant species collected in 2010. Ants were sampled and information was obtained from 15 sites in Gorgona island (13.82km²), including the Gorgonilla atoll (0.49km²). Collecting methods included pitfall traps, tuna baits, mini-Winkler extraction of leaf litter, Malaise traps, entomological net and direct search. The soil and understory ant inventory resulted in 107 ant species and morphospecies, 46 genera in 12 subfamilies. Myrmicinae held the highest species richness (37 species), followed by Ponerinae (27) and Formicinae (12). The richest genera were Pachycondyla (15 species), Camponotus (nine) and Pheidole (eight), while 30 genera were represented by a single species. Twelve species were very common (both in distribution and time): Azteca sp., Atta cephalotes, Camponotus sericeiventris, Eciton vagans, Ectatomma goninion, Gnamptogenys annulata, Odontomachus bauri, Pachycondyla bugabensis, P. harpax, P. verenae, Paraponera clavata and Wasmannia auropunctata. Direct search was the most efficient method to collect diferent species and was responsible for 52% of the total species found. Compared to other Neotropical islands, Gorgona holds a suprisingly high number of ant species, none of them invasive. The invasive Monomorium floricola, which was collected 20 years ago, was not found in 2010. These evidences suggest that ecological mechanisms and natural recovery processes in the ecosystem have generated microhabitats allowing their coexistence. Rev. Biol. Trop. 62 (Suppl. 1): 265-276. Epub 2014 February 01.

Este trabajo compila registros publicados (1991) y no publicados (2006) sobre las especies de hormigas del PNN Gorgona y aporta nuevos registros de especies recolectadas en 2010. Se recopiló información de 15 diferentes sitios de isla Gorgona (13.82km²), incluyendo la pequeña isla de Gorgonilla (0.4899km²). Los métodos de recolecta incluyeron trampas de caída, cebos de atún, sacos Winkler, trampas Malaise, red entomológica y captura directa. El inventario de hormigas de suelo y sotobosque resultó en 107 especies y morfoespecies, 46 géneros y 12 subfamilias. Myrmicinae reunió la mayor riqueza (37 especies) seguida de Ponerinae (27) y Formicinae (12). Los géneros más ricos fueron Pachycondyla (15 especies), Camponotus (nueve) y Pheidole (ocho), mientras que 30 géneros solo presentaron una especie. Doce especies fueron muy comunes: Azteca sp., Atta cephalotes, Camponotus sericeiventris, Eciton vagans, Ectatomma goninion, Gnamptogenys annulata, Odontomachus bauri, Pachycondyla bugabensis, P. harpax, P. verenae, Paraponera clavata y Wasmannia auropunctata. En comparación con otras islas neotropicales, Gorgona tiene un número sorprendentemente elevado de especies de hormigas, ninguna de ellas invasivas. Por tanto, estos resultados sugieren que, mecanismos ecológicos y procesos de recuperación natural en el ecosistema han generado disponibilidad de microhábitats permitiendo la coexistencia una gran riqueza de especies.