[IN1336] Argentine ant, Linepithema humile (Mayr) (Insecta: Hymenoptera: Formicidae)

The Argentine ant, Linepithema humile (Mayr), is an insect native to South America, but an invasive species in many parts of the world. It is globally distributed. Linepithema humile is considered a pest species, primarily due to its feeding habits of tending and protecting honeydew producing insects, such as scale insects, which are often damaging to crops and ornamental plants. This aggressive, populous ant species also has a negative effect on native ant species. Linepithema humile colonies have multiple queens, allowing colonies to grow and spread rapidly. Under certain conditions, the argentine ant may also become a household pest if it finds a way into homes. Linepithema humile has been designated as a tramp ant species, meaning that it has an incredible ability to spread and establish in new areas and is difficult to control. Linepithema humile, like other tramp species, can establish in new locations quickly due to the multi-queen nature of the colonies, their abitlity to forage and find resources, and the extensive network of interrelated colonies they are able to form. This document provides an in-depth synopsis of the insect's life history, biology, and management.

Trait Plasticity among Invasive Populations of the Ant Technomyrmex brunneus in Japan

Characters in invasive populations often differ from those in the native range, and the ability to express different characters may enhance invasive potential. Ants are among the most pervasive and damaging invasive species, by virtue of their transportability and broad-ranging ecological interactions. Their success is often attributed to the ability to exhibit different characteristics in invasive populations, including the formation of large, unicolonial associations (‘supercolonies’). It remains unclear, however, if such characteristics are a product or cause of the ecological dominance of invasive ants, and the advancement of our understanding has likely been restrained by the fact that studies to date have focused on a few globally important species with well-established invasions. In this study, we take advantage of an ongoing invasion of the tramp ant Technomyrmex brunneus in Japan to assess trait plasticity in the invasive range of this species. We find evidence for plasticity in social structure among island populations, with a supercolony evident on one of the three islands studied. Interestingly, we found no evidence of lower genetic diversity in this population, though natural isotope data indicate it was operating at a lower trophic level than other populations. These findings add weight to arguments that invasive species may benefit from the capacity to adaptively mould themselves to new ecological contexts.

Tapinoma melanocephalum (ghost ant).

T. melanocephalum is a small ant species around 1.5 mm in length originating from the Old World tropics. It is considered an invasive and "tramp" ant species: widely associated with humans, it has been moved around the subtropical and tropical world by human activity. This ant is also recorded in heated buildings in areas such as Canada and Finland. It is primarily a household pest, nesting in housing and consuming household food. In areas such as Florida it is considered one of the most important house-infesting pests. However it has been known to affect agricultural production in situations such as greenhouses, especially if it tends honeydew-producing insects and protects these pests from biological control organisms. T. melanocephalum is thought to be capable of transporting pathogenic microbes and is often abundant in hospitals. Some people can suffer a slight, red irritation of the skin following contact with this ant. This ant is listed on the ISSG global invasive species database.

First North American Records of the Old-World Tramp Ant Syllophopsis sechellensis(Hymenoptera: Formicidae)

Syllophopsis sechellensis (Emery) (formerly Monomorium sechellense) (Hymenoptera: Formicidae) is a small, inconspicuous ant species native to the Old-World tropics. Syllophopsis sechellensis is widespread in Asia and Australia, and on islands the Indian, Pacific, and Atlantic Oceans. In the New World, all published records come from West Indian islands. Here, I report the first records of S. sechellensis from North America: from four sites in Miami-Dade and Broward counties, Florida, more than 1500 km from the closest records in the West Indies. The ants of Florida have been well-studied in the past, so S. sechellensis appears to be a recent arrival.

Non-native and Invasive Nylanderia Crazy Ants (Hymenoptera: Formicidae) of the World: Integrating Genomics to Enhance Taxonomic Preparedness

Invasive species have devastating economic and ecological impacts worldwide, but proactive monitoring programs are rare on the global stage. By definition, tramp ants are associated with disturbance and human-mediated dispersal, making them especially concerning invasive threats. A proactive—rather than reactive—approach to monitoring for, preventing, and managing invasive species depends on taxonomic preparedness, which enables rapid and accurate identification. Emerging tools and technologies, including genomic barcoding and interactive online keys, can aid in species delimitation and diagnosis. However, resolving tramp species’ identities remains the fundamental first step in invasive species management because diagnostic tools cannot be developed and disseminated until species names are stable. Diagnosis of morphologically difficult species requires basic knowledge of species boundaries, biogeography, and phylogenetic relationships. This review comprehensively synthesizes information available for 15 known and five potential tramp ant species in Nylanderia (Emery) (Hymenoptera: Formicidae): a globally distributed genus of over 130 described species, many of which are only diagnosable by subtle morphological characters. Nylanderia records were drawn from published literature, specimen databases, and museum collections to compile known distributions, biology, natural history, and taxonomy for each species. We review existing resources for visualizing known geographic ranges and high-resolution images of ants globally and encourage the use of these types of tools in support of invasive species diagnosis and distribution tracking. Finally, we discuss how taxonomic and life history information can be used synergistically with genomic and digital technology to develop tools for identification of these, and other emerging invasive insect species.

Cytoplasmic incompatibility between Old and New World populations of a tramp ant

As we enter the Anthropocene, the evolutionary dynamics of species will change drastically, and as yet unpredictably, due to human activity. Already today, increases in global human traffic have resulted in the rapid spread of species to new areas, leading to the formation of geographically isolated populations. These go on to evolve in allopatry, which can lead to reproductive isolation, and potentially, the formation of new species. Surprisingly, little is known about such eco-evolutionary processes in ants, even though numerous invasive ant species are globally distributed in geographically isolated populations. Here, we describe the first case of cytoplasmic incompatibility (CI) between populations of a cosmotropic distributed tramp ant with Asian roots, Cardiocondyla obscurior, which has acquired a novel Wolbachia strain in the New World. Our study uncovers the first symbiont-induced mechanism of reproductive isolation in ants, providing a novel perspective on the biology of globally distributed ants.