Wasmannia Forel (Hymenoptera: Formicidae: Myrmicinae) in Argentina: systematics and distribution

The ant genus Wasmannia is endemic to the Neotropics, with 10 species occurring within the presumptive native range for the genus from Mexico to Argentina. Only the little fire ant, Wasmannia auropunctata is widely distributed being present from central-eastern Argentina to Bermuda, and has become infamous due to its recent worldwide expansion and status as an invasive pest. The objective of this work was to study the systematics and distribution of Wasmannia in its southern limit of distribution in Argentina. Out of the three species reported so far for Argentina, only W. auropunctata was found to be widely distributed, but abundant only in disturbed habitats mostly in the Northeast. Herein, the distribution of Wasmannia auropunctata is extended and its queen and male castes are redescribed, along with descriptions of gynandromorphs (specimens with left side of the head similar to a male and right side similar to a queen). Wasmannia sulcaticeps and W. williamsoni are much less common and widespread. W. sulcaticepsis mostly found in mountain forests in northwestern Argentina, whereas W. williamsoni is only found in shrublands and grasslands in central eastern Argentina, and most frequently in mountain grasslands. Both species overlap with W. auropunctata, which is more common in the lowlands, between approximately 400 and 1000 m elevation. The queen of W. williamsoni is described and queen and male of W. sulcaticeps are redescribed. A new species, Wasmannia longiseta n. sp. Cuezzo and Calcaterra, recently found in northeastern Argentina is described based on worker morphology. Wasmannia rochai is recorded for the first time in Misiones, extending its distribution range from São Paulo (Brazil) to Misiones in northeastern Argentina. A key to the worker caste is provided. A cladistic analysis based on discrete and continuous morphological characters is presented as a first attempt to clarify the phylogenetic relationships between the known species of Wasmannia.Fil: Cuezzo, Fabiana del Carmen. Universidad Nacional de Tucumán. Facultad de Ciencias Naturales E Instituto Miguel Lillo. Instituto Superior de Entomología; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Calcaterra, Luis Alberto. Fundación Para El Estudio de Especies Invasivas; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Chifflet, Lucila. Universidad de Buenos Aires; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Follet, P. A.. Pacific Basin Agricultural Research Center; Estados Unido

Dependence of egg hatching on Wolbachia density in a parthenogenetic weevil revealed by antibiotic treatment

Naupactini is a tribe of Neotropical broad-nosed weevils highly diverse in South America. This group includes several parthenogenetic species, some of them harmful for agriculture and invasive around the world. Although some hypotheses based on polyploidy and hybridization have been proposed to explain the origin of parthenogenesis in weevils, the infection with the bacterium Wolbachia pipientis may be involved in the origin of parthenogenetic reproduction of some species. In this contribution, we studied the role of Wolbachia in the reproductive biology of Pantomorus postfasciatus Hustache (Coleoptera: Curculionidae) through a curing experiment using tetracycline. This weevil has a mixed mode of reproduction including sexual and parthenogenetic populations. Exposure to an antibiotic did not affect fecundity, but did reduce egg hatching in comparison with untreated individuals. Consequently, we inferred that Wolbachia most probably takes part in the reproduction of P. postfasciatus, either by exerting nutritive functions in oogenesis necessary for egg hatching, or by induction of thelytokous parthenogenesis. Although infection was not totally cured, Wolbachia load was significantly lower in treated than in control females. Thereby, we hypothesize that a minimum threshold density of Wolbachia is required for weevil reproduction. We conclude that all analyses support a role of Wolbachia in P. postfasciatus reproduction.Fil: Rodriguero, Marcela Silvina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Ecología, Genética y Evolución de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Ecología, Genética y Evolución de Buenos Aires; ArgentinaFil: Scannapieco, Alejandra Carla. Instituto Nacional de Tecnología Agropecuaria. Centro de Investigación en Ciencias Veterinarias y Agronómicas. Instituto de Genética; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Monti, Daniela Soledad. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Ecología, Genética y Evolución de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Ecología, Genética y Evolución de Buenos Aires; ArgentinaFil: Chifflet, Lucila. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Ecología, Genética y Evolución de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Ecología, Genética y Evolución de Buenos Aires; ArgentinaFil: Elías Costa, Agustín Jorge. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Ecología, Genética y Evolución de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Ecología, Genética y Evolución de Buenos Aires; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales "Bernardino Rivadavia"; ArgentinaFil: Lanteri, Analia Alicia. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata; ArgentinaFil: Confalonieri, Viviana Andrea. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Ecología, Genética y Evolución de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Ecología, Genética y Evolución de Buenos Aires; Argentin

Evolutionary history of the little fire ant Wasmannia auropunctata before global invasion: Inferring dispersal patterns, niche requirements and past and present distribution within its native range

The evolutionary history of invasive species within their native range may involve key processes that allow them to colonize new habitats. Therefore, phylogeographic studies of invasive species within their native ranges are useful to understand invasion biology in an evolutionary context. Here we integrated classical and Bayesian phylogeographic methods using mitochondrial and nuclear DNA markers with a palaeodistribution modelling approach, to infer the phylogeographic history of the invasive ant Wasmannia auropunctata across its native distribution in South America. We discuss our results in the context of the recent establishment of this mostly tropical species in the Mediterranean region. Our Bayesian phylogeographic analysis suggests that the common ancestor of the two main clades of W. auropunctata occurred in central Brazil during the Pliocene. Clade A would have differentiated northward and clade B southward, followed by a secondary contact beginning about 380 000 years ago in central South America. There were differences in the most suitable habitats among clades when considering three distinct climatic periods, suggesting that genetic differentiation was accompanied by changes in niche requirements, clade A being a tropical lineage and clade B a subtropical and temperate lineage. Only clade B reached more southern latitudes, with a colder climate than that of northern South America. This is concordant with the adaptation of this originally tropical ant species to temperate climates prior to its successful establishment in the Mediterranean region. This study highlights the usefulness of exploring the evolutionary history of invasive species within their native ranges to better understand biological invasions. © 2016 European Society for Evolutionary Biology

Ecological and genetic studies of the invasive ant Wasmannia auropunctata in Argentina, its native southernmost distribution limit

La historia evolutiva de especies invasoras en su área nativa puede involucrar procesos clave en su éxito fuera de ésta. Wasmannia auropunctata es una hormiga neotropical, que ha invadido diversos sitos tropicales del mundo, aunque recientemente también se estableció en la región Mediterránea. La posible población fuente de esta última invasión se localizó en Argentina, el límite sur de su distribución nativa. Resulta entonces interesante estudiar las poblaciones de W. auropunctata en esta región para entender su éxito fuera de la zona intertropical. En este trabajo se estudiaron distintos aspectos -ecológicos, genéticos y comportamentales- de W. auropunctata en el límite sur de su distribución nativa, con el fin de entender qué factores son responsables de su éxito y analizar si su historia evolutiva se corresponde con la reciente introducción en el Mediterráneo. Se analizó si las poblaciones en esta región presentan características invasoras, estudiando la asociación entre su dominancia y la perturbación del ambiente, su sistema de reproducción, por medio de microsatélites, y su sistema de organización social, por medio de ensayos de agresión. Se realizó un estudio filogeográfico, utilizando ADN mitocondrial y nuclear, para analizar su historia de dispersión y diversificación. Por medio de un modelado de nicho ecológico se determinaron áreas centrales y marginales de distribución y se analizó cómo cambiaron a lo largo del Cuaternario. Finalmente, se analizó su habilidad competitiva en un ensamble local, utilizando cebos y trampas de caída. Wasmannia auropunctata resultó estar ampliamente distribuida en esta región, siendo abundante y dominante en sitios perturbados, principalmente antrópicos. La organización social fue mayormente supercolonial independientemente del nivel de perturbación del ambiente. El sistema de reproducción fue principalmente clonal en sitios antrópicos; mixto en sitios con perturbación antrópica media y en las planicies de inundación; y sexual en sitios naturales. Los marcadores mitocondriales y nucleares corroboraron la existencia de dos clados principales (A y B), como había sido propuesto en otros trabajos. Un análisis filogeográfico bayesiano sugirió que el ancestro común de ambos clados habría existido en el centro de Brasil hace 3,9 millones de años aproximadamente, desde done el clado A se expandió hacia el norte y el B (el mismo que invadió el Mediterráneo) hacia el sur. El modelado de nicho ecológico sugirió que su diferenciación genética podría estar acompañada de una diferenciación de nicho ecológico, siendo el clado A un linaje tropical y el B un linaje subtropical y templado. Sólo el clado B alcanzó altas latitudes en el sur de Sudamérica, hasta Argentina, caracterizado por un clima más frío que el norte de este continente. Esto es compatible con su posterior establecimiento en la región Mediterránea. Wasmannia auropunctata presentó una baja habilidad competitiva, indicando que ésta no es un factor asociado a su éxito. En conjunto, nuestros resultados sugieren que los ambientes naturalmente perturbados (como las planicies de inundación) habrían jugado un papel importante en la aparición de características, como la clonalidad y la supercolonialidad, que posteriormente favorecerían a W. auropunctata en ambientes antrópicos, clave para su introducción fuera de su rango nativo. Por otro lado, su expansión natural a altas latitudes hacia el sur de Sudamérica, le habría permitido una adaptación a climas más fríos y con marcada estacionalidad, clave para su establecimiento en la región Mediterránea. El presente estudio refleja la utilidad de la exploración de la historia de vida de una especie invasora dentro de su rango nativo para lograr una mejor comprensión de su escenario de invasión.The evolutionary history of exotic species within their native range may involve key processes for colonizing new habitats. Native from the Neotropics, the little fire ant Wasmannia auropunctata has invaded many tropical sites around the world, and it has recently been introduced in the Mediterranean region. The putative source population of this last invasion was located in Argentina, its native southernmost distribution limit. Therefore, it is interesting to study the populations of W. auropunctata in this region to understand its success outside the tropics. We studied different -biological, genetic and behavioural- aspects of W. auropunctata within its native southernmost distribution limit, in order to understand which factors are responsible for its success and analyze whether its evolutionary history agrees with the recent introduction into the Mediterranean. We examined whether the populations in this region have invasive characteristics, studying the association between their dominance and the habitat disturbance, the reproductive system, using microsatellite markers, and the social organization, through aggression tests. We analyzed mitochondrial and nuclear DNA markers, to perform a phylogeographic analysis in order to infer its dispersion and genetic differentiation history. Through an ecological niche modelling, we identified central and marginal distribution areas and analyzed how they changed over the Quaternary. Finally, we analyzed its competitive ability in a local assembly, using baits and pitfall traps. Wasmannia auropunctata was widespread at the southernmost limit of its native distribution range, with higher abundances being mainly recorded in anthropic habitats. The social organization was mainly supercolonial in all habitat types. The reproductive system was mainly clonal in anthropic habitats, mixed in partially disturbed sites and floodplains, and sexual in natural sites. The genetic analysis corroborated the existence of two main clades (A and B), as had been proposed in other works. Phylogeographical Bayesian analysis suggested that the common ancestor of both clades would have existed in central Brazil about 3.9 million years ago, from where clade A would have expanded and differentiated northward and clade B (the same that invaded the Mediterranean) southward. The ecological niche modelling suggested that genetic differentiation could be accompanied by a differentiation in the ecological niche requirements, clade A being a tropical lineage and clade B a subtropical and temperate lineage. Clade B was the only one which reached high latitudes in southern South America, which is characterized by colder temperatures than the north of the continent. This agrees with the subsequent establishment in the Mediterranean region. Wasmannia auropunctata had a low competitive ability, indicating that interspecific competition is not a factor associated with its success. Taken together, our results suggest that naturally disturbed environments (such as floodplains) may have played an important role in the appearance of features such as clonality and supercoloniality, which would have later favor W. auropunctata in anthropic habitats, key to its dispersal outside its native range. Aditionally, the natural expansion at high latitudes to the south of South America, would have allowed it to adapt to colder climates and seasonality, key to its later establishment in the Mediterranean region. This study highlights the usefulness and value of exploring the life history and biology of invasive species within their native range to better understand invasion scenario.Fil:Chifflet, Lucila. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina

Diversity of ground-dwelling ants across three severely threatened South American subtropical forests: are diversity patterns influenced by spatial or climatic variables?

Understanding the spatial distribution of species sheds light on the biogeographical history, offers clues to the drivers of biodiversity and helps guide conservation strategies. In southern South America, Andean, Chaco and Atlantic forests drastically decreased their coverage in the last decades mainly by changes in land use. Ants represent an excellent model for macro-ecological studies that support evidence-based management policies. Unfortunately, little is known about ant distribution, diversity patterns and drivers in the southernmost portion of these three biomes. We surveyed ground-dwelling ants using baits and leaf-litter sieves in 38 sites across these subtropical forests in Argentina. We analysed ant species richness, turnover and composition within and between forests, and whether spatial and climatic variables explain diversity patterns. We collected 161 species belonging to 38 genera. The Atlantic forest had the highest cumulative species richness (91 species), followed by the Chaco (60) and Andean (52) forests. Neither mean species richness nor beta diversity differed significantly between forests, though both indicators tended to increase from west to east. Seven spatial and climatic variables differentiated forests. Aridity index, and variables associated with seasonal rainfall, moderately influenced a tendency to increase species richness from west to east. We identified five shared species between the Andean and Atlantic forests, which are candidates to test biogeographic hypotheses. The high level of species replacement across and among forests resulted in unique assemblages (with at least 29 species that seem to be exclusive to one forest), indicating the importance of conserving the biodiversity of the three forests.Fil: Calcaterra, Luis Alberto. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Fundación para el Estudio de Especies Invasivas; ArgentinaFil: Chifflet, Lucila. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales "Bernardino Rivadavia"; ArgentinaFil: Cuezzo, Fabiana del Carmen. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de Tucumán. Facultad de Ciencias Naturales e Instituto Miguel Lillo. Instituto Superior de Entomología; ArgentinaFil: Sánchez Restrepo, Andrés Fernando. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Fundación para el Estudio de Especies Invasivas; Argentin

Southern expansion of the invasive ant Wasmannia auropunctata within its native range and its relation with clonality and human activity.

The little fire ant Wasmannia auropunctata, native to the Neotropics, has become a serious pest worldwide over the past 100 years. It was originally distributed from Mexico to northern Argentina and new evidence suggests a recent southern range expansion during the last 60 years reaching central Argentina. This supercolonial ant species has a polymorphic reproductive system. Some populations, mostly found in undisturbed natural environments, are characterised by a classical sexual haplodiploid reproductive system. In other populations, which mainly occur in human-modified habitats, diploid queens and haploid males are produced clonally while workers are produced sexually. Here we studied the association between the recent southern range expansion of W. auropunctata in relation to human activity and clonality. We carried out an extensive survey within the southern limit of the species' native distribution and characterised the type of habitat where populations were found. Moreover, we genetically determined the type of reproductive system in 35 populations by genotyping at 12 microsatellite loci a total of 191 reproductive individuals (i.e. queens and/or males). Clonality was the most common reproductive system, occurring in 31 out of 35 populations analysed. All the populations found in the recently colonised area in central Argentina were clonal and established in human-modified habitats, suggesting that clonality together with human activity might have facilitated the southwards expansion of W. auropunctata

Linking thermo-tolerances of the highly invasive little fire ant, Wasmannia auropunctata, to its current and potential distribution. Biological Invasions

Species distribution models based on the correlation of bioclimatic variables and presence spatial data-points are useful for recognizing species habitat suitability. However, they have limitations in predicting the introduced ranges of invasive species that could be overcome by using species eco-physiological traits. By combining bioclimatic variables with thermal tolerance plasticity of the highly invasive little fire ant, Wasmannia auropunctata, we intend to better understand the mechanism underlying its current and future distributions. To this end, we performed: 1) laboratory physiological experiments to assess thermal tolerances (CTmin and CTmax) and evaluate the effect of acclimation (laboratory) and acclimatization (nature) on these variables, 2) behavioral foraging observations in the field, 3) a correlative and a simple mechanistic SDM. Briefly, physiological results showed a modulation of the CTmax and CTmin by different acclimation temperatures and by seasonal thermal acclimatization. In the field, worker foraging activity begins at environmental temperatures just above (less than 1°C) the lowest CTmin recorded in the laboratory. At the global scale, CTmin constitutes a key physiological trait that, when linked with the minimum temperature of the coldest month, could explain the southernmost limit of W. auropunctata native distribution and its physiological capacity to expand in the Mediterranean region. The eco-physiological approach carried out here may help explain the current distribution and predict potential spread of populations when there is no certain information about the whole distribution of the species or under a changing environment. The latter is of great importance especially when analyzing invasive insects, pests or disease vectors.Fil: Coulin, Carolina. Fundación para el Estudio de Especies Invasivas; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Biodiversidad y Biología Experimental y Aplicada. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Biodiversidad y Biología Experimental y Aplicada; Argentina. Universidad Nacional de Río Negro. Sede Andina. Instituto de Investigaciones en Recursos Naturales, Agroecología y Desarrollo Rural; ArgentinaFil: de la Vega, Gerardo José. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Biodiversidad y Biología Experimental y Aplicada. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Biodiversidad y Biología Experimental y Aplicada; ArgentinaFil: Chifflet, Lucila. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Ecología, Genética y Evolución de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Ecología, Genética y Evolución de Buenos Aires; ArgentinaFil: Calcaterra, Luis Alberto. Fundación para el Estudio de Especies Invasivas; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Schilman, Pablo Ernesto. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Biodiversidad y Biología Experimental y Aplicada. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Biodiversidad y Biología Experimental y Aplicada; Argentin

Correction: A Species delimitation approach to uncover cryptic species in the South American fire ant decapitating flies (Diptera: Phoridae: Pseudacteon).

[This corrects the article DOI: 10.1371/journal.pone.0236086.]

A Species delimitation approach to uncover cryptic species in the South American fire ant decapitating flies (Diptera: Phoridae: Pseudacteon).

South American fire ant decapitating flies in the genus Pseudacteon (Diptera: Phoridae) are potential biocontrol agents of the invasive fire ants Solenopsis invicta and S. richteri in the United States and other regions of the world due to their high host specificity and the direct and indirect damage to their host ants. Despite their importance and the fact that several flies have already been released in the US, little is known about the genetic variability and phylogenetic relationships of Pseudacteon flies parasitizing South American fire ants in the Solenopsis saevissima species-group. A species delimitation analysis was conducted using a distance-based method (ABGD) and two tree-based methods (GMYC and mPTP) using COI sequences of 103 specimens belonging to 20 of the 22 Pseudacteon species known from southern South America. Additionally, phylogenetic relationships between the already described and new candidate species were inferred using mitochondrial (COI) and nuclear (wingless) sequences. The species delimitation analysis suggests that species richness in these flies has been previously underestimated, due to the existence of putative cryptic species within nominal Pseudacteon obtusus, P. pradei, P. tricuspis, P. cultellatus, and P. nudicornis. Geographic distribution and host fire ant species seem to support cryptic lineages, though additional morphological data are needed to corroborate these results. All phylogenetic analyses reveal that South American fire ant decapitating flies are grouped into two main clades, with Pseudacteon convexicauda sister and well differentiated relative to these clades. Neither host nor geographic association appeared to be related to the differentiation of these two main clades within South American fire ant decapitating flies. This work provides information that will allow testing whether the putative cryptic phorid fly species show differences in their effectiveness as biocontrol agents against the highly invasive imported fire ants