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We obtained 14,140 interception records of ants arriving in Australia between 1986 and 2010 to examine taxonomic and biogeographic patterns of invasion. We also evaluated how trade and transport data influenced interception rates, the identity of species being transported, the commerce most associated with the transport of ants, and which countries are the primary sources for ants arriving in Australia. The majority of ant interceptions, accounting for 48% of interceptions, were from Asia and Oceania. The top commodities associated with ant interceptions were: (1) Live trees, plants, cut flowers; (2) Wood and wood products; (3) Edible vegetables; and (4) Edible fruit and nuts. The best fitting model for predicting ant interceptions included volumes for these four commodities, as well as total trade value, transport volume, and geographic distance (with increased distance decreasing predicted ant interceptions). Intercepted ants identified to species consisted of a combination of species native to Australia, introduced species already established in Australia, and species not yet known to be established. 82% of interceptions identified to species level were of species already known to be established in Australia withParatrechina longicornishaving the most records. These data provide key biogeographic insight into the overlooked transport stage of the invasion process. Given the difficult nature of eradication, once an ant species is firmly established, focusing on early detection and quarantine is key for reducing the establishment of new invasions.

Embryonic exposure to steroids often leads to long-term phenotypic effects. It has been hypothesized that mothers may be able to create a steroid environment that adjusts the phenotypes of offspring to current environmental conditions. Complicating this hypothesis is the potential for developing embryos to modulate their early endocrine environment. This study utilized the threespined stickleback (Gasterosteus aculeatus) to characterize the early endocrine environment within eggs by measuring four steroids (progesterone, testosterone, estradiol, and cortisol) of maternal origin. We then examined how the concentrations of these four steroids changed over the first 12 days post fertilization (dpf). Progesterone, testosterone, estradiol, and cortisol of maternal origin could be detected within unfertilized eggs and levels of all four steroids declined in the first 3 days following fertilization. While levels of progesterone, testosterone, and estradiol remained low after the initial decline, levels of cortisol rose again by 8 dpf. These results demonstrate that G. aculeatus embryos begin development in the presence of a number of maternal steroids but levels begin to change quickly following fertilization. This suggests that embryonic processes change the early endocrine environment and hence influence the ability of maternal steroids to affect development. With these findings, G. aculeatus becomes an intriguing system in which to study how selection may act on both maternal and embryonic processes to shape the evolutionary consequence of steroid-mediated maternal effects. J. Exp. Zool. 323A: 422–429, 2015. © 2015 Wiley Periodicals, Inc.

Ants are some of the most abundant and familiar animals on Earth, and they play vital roles in most terrestrial ecosystems. Although all ants are eusocial, and display a variety of complex and fascinating behaviors, few genomic resources exist for them. Here, we report the draft genome sequence of a particularly widespread and well-studied species, the invasive Argentine ant ( Linepithema humile ), which was accomplished using a combination of 454 (Roche) and Illumina sequencing and community-based funding rather than federal grant support. Manual annotation of >1,000 genes from a variety of different gene families and functional classes reveals unique features of the Argentine ant's biology, as well as similarities to Apis mellifera and Nasonia vitripennis . Distinctive features of the Argentine ant genome include remarkable expansions of gustatory (116 genes) and odorant receptors (367 genes), an abundance of cytochrome P450 genes (>110), lineage-specific expansions of yellow/major royal jelly proteins and desaturases, and complete CpG DNA methylation and RNAi toolkits. The Argentine ant genome contains fewer immune genes than Drosophila and Tribolium , which may reflect the prominent role played by behavioral and chemical suppression of pathogens. Analysis of the ratio of observed to expected CpG nucleotides for genes in the reproductive development and apoptosis pathways suggests higher levels of methylation than in the genome overall. The resources provided by this genome sequence will offer an abundance of tools for researchers seeking to illuminate the fascinating biology of this emerging model organism.

Summary 1. Adaptive maternal programming occurs when mothers alter their offspring's phenotype in response to environmental information such that it improves offspring fitness. When a mother's environment is predictive of the conditions her offspring are likely to encounter, such transgenerational plasticity enables offspring to be better-prepared for this particular environment. However, maternal effects can also have deleterious effects on fitness. 2. Here, we test whether female threespined stickleback fish exposed to predation risk adaptively prepare their offspring to cope with predators. We either exposed gravid females to a model predator or not, and compared their offspring's antipredator behaviour and survival when alone with a live predator. Importantly, we measured offspring behaviour and survival in the face of the same type of predator that threatened their mothers (Northern pike). 3. We did not find evidence for adaptive maternal programming; offspring of predator-exposed mothers were less likely to orient to the predator than offspring from unexposed mothers. In our predation assay, orienting to the predator was an effective antipredator behaviour and those that oriented survived for longer. 4. In addition, offspring from predator-exposed mothers were caught more quickly by the predator on average than offspring from unexposed mothers. The difference in antipredator behaviour between the maternal predator-exposure treatments offers a potential behavioural mechanism contributing to the difference in survival between maternal treatments. 5. However, the strength and direction of the maternal effect on offspring survival depended on offspring size. Specifically, the larger the offspring from predator-exposed mothers, the more vulnerable they were to predation compared to offspring from unexposed mothers. 6. Our results suggest that the predation risk perceived by mothers can have long-term behavioural and fitness consequences for offspring in response to the same predator. These stress-mediated maternal effects can have non-adaptive consequences for offspring when they find themselves alone with a predator. In addition, complex interactions between such maternal effects and offspring traits such as size can influence our conclusions about the adaptive nature of maternal effects.

The success of invasive ants is frequently attributed to genetic and behavioural shifts in colony structure during or after introduction. The Argentine ant (Linepithema humile), a global invader, differs in colony genetic structure and behaviour between native populations in South America and introduced populations in Europe, Japan, New Zealand and North America. However, little is known about its colony structure in Australia. We investigated the genetic structure and behaviour of L. humile across Melbourne, Victoria by quantifying variation at four microsatellite loci and assaying intraspecific aggression at neighbourhood (30–200 m), fine (1–3.3 km) and regional (5–82 km) spatial scales. Hierarchical analyses across these scales revealed that most genetic variation occurred among workers within nests (∼98%). However, although low genetic differentiation occurred among workers between nests at the fine and regional scales (∼2%), negligible differentiation was detected among workers from neighbouring nests. Spatial genetic autocorrelation analysis confirmed that neighbouring nests were genetically more similar to each other. Lack of aggression within and across these scales supported the view that L. humile is unicolonial and forms a large supercolony across Melbourne. Comparisons of genetic structure of L. humile among single nests sampled from Adelaide, Brisbane, Hobart and Perth with Melbourne showed no greater levels of genetic differentiation or dissimilar spatial structure, suggesting an Australia-wide supercolony.

Moffett provides a very thorough review of the ‘‘supercolony’’ concept, focusing on the biology of the Argentine ant (Linepithema humile). The term supercolony is being used more and more frequently in the social insect literature, however, not always to describe the same colony structure. Despite invoking an almost science fiction-like quality, we agree with Moffett that the concept of the supercolony has been valuable, providing considerable insight from both an ecological and an evolutionary perspective. Ecologically, the term supercolony is often used to describe a polydomous colony that occupies such a large number of nests that it is impossible for all members of the colony to interact in their lifetime (Pedersen et al. 2006). That is, the society occupies many nest sites over such a large area that queens and workers who live on one side of the supercolony will never meet individuals from the other side. As Moffett points out, this is likely true for many social insects, even those that occupy relatively few nest sites over smaller areas. Moffett suggests that we restrict the definition of supercolony to societies with at least 1 million workers. However, this seems a bit arbitrary; a number of ant species are known to have more than 1 million workers yet occupy a single nest site. Are these supercolonies in the same sense that a spatially extensive polydomous Argentine ant colony is? Species that form supercolonies are also often ecologically dominant where they occur, both outcompeting other species for resources and overwhelming species through numerical superiority (Holway et al. 2002). However, as pointed out by Holldobler and Wilson (1977), research is still needed to determine if ants become ecologically dominant because they form supercolonies or if ecologically dominant ants monopolize resources and subsequently form supercolonies as a result. From an evolutionary perspective, a supercolony can be defined as the aggregation of ants across many nests that share a common genotype (usually inferred using microsatellites or mitochondrial DNA) and phenotype (e.g., cuticular hydrocarbon profile). This is likely due to having a shared common ancestry. Subsequently, this approach has been used to examine the source and introduction history of invasive ants. Recent holistic work combining behavior, chemistry, and genetics has provided incredible insight into the worldwide spread of Argentine ants (Wilgenburg et al. 2010), and supercolony identity has been used to infer recent exchange of ants between different introduced populations (Tsutsui et al. 2001; Corin et al. 2007; Sunamura et al. 2009; Vogel et al. 2010; Suhr et al. 2011). As Moffett points out, genetic work on both native and introduced populations of Argentine ants suggests little to know gene flow among supercolonies. However, we disagree that each supercolony should be considered its own species (much as each individual is not considered its own species in clonal organisms). More work is needed to determine the spatial extent of gene flow in species that form supercolonies. We agree with Moffett that we need to move past semantic arguments when discussing supercolonies. However, we believe that both ecological and evolutionary examinations of supercolonies need to be conducted from the perspective of the population. A population can be defined as a group of colonies that have the potential to exchange genes or compete for resources. A population can therefore have many colonies, even many supercolonies. However, the term unicolonial, which is often considered synonymous with supercolony (Pedersen et al. 2006), should be restricted to describe situations in which the entire population consists of only one supercolony (a ‘‘unicolonial population’’ Holldobler and Wilson 1977; Suarez et al. 2008). Research is still clearly needed on the biology of species that form supercolonies as many unanswered questions remain. For example, how do supercolonies arise and how long do they last? How much variation in social parameters exists in native populations of species that can form supercolonies (e.g., colony size, queen number, intravs. intercolony genetic diversity, gene flow among colonies)? Is there conflict over reproduction within supercolonies or are they as harmonious as Moffett implies? Over what spatial scales are food and information exchanged (Heller et al. 2008)? These last 2 questions in particular address whether or not supercolonies are effectively made up of aggregations of smaller colonies. Despite being one of the best-studied social insects, we still know surprisingly little about the biology of Argentine ants, particularly in their native range. From an evolutionary perspective, we often know even less about species closely related to those that form supercolonies. For example, what characteristics are shared among sibling species in the humile complex or are unique to the widespread L. humile?