The microsporidian pathogen Myrmecomorba nylanderiae: Intracolony transmission and impact upon tawny crazy ant (Nylanderia fulva) colonies

Abstract

The microsporidian pathogen Myrmecomorba nylanderiae Plowes et al. infects introduced tawny crazy ants (Nylanderia fulva (Mayr)), and constitutes one of the first natural enemies known to attack this invasive ant. We assess how infection is transmitted within colonies and how infection impacts N. fulva colony fragment growth under carbohydrate-deficient and carbohydrate-sufficient dietary conditions. Carbohydrate scarcity is a common source of stress for ant colonies. Infected workers efficiently pass infection to developing larvae but all other potential pathways for within colony transmission are rare or non-viable. For unknown reasons, queens within infected colony fragments are generally uninfected, limiting the role of transovarial transmission in intracolony transmission. In the laboratory, infection by M. nylanderiae primarily impacts the growth of N. fulva colonies by reducing pupal production. Colony growth showed a substantially greater impact under carbohydrate-deficient conditions implying that the effect of the pathogen may depend on seasonally variable carbohydrate availability. In the colony growth assay, worker mortality did not differ with infection status under either nutrient regime. However, in a longer, direct test of survivorship, infected worker survivorship was significantly lower. Recently, some established N. fulva populations with high prevalence of M. nylanderiae infection have declined precipitously, though it is unknown if M. nylanderiae is a causative agent in these declines. The combination of chronic impacts, presence in North America, and potential association with population declines makes M. nylanderiae a promising prospect for the biological control of N. fulva. K E Y W O R D Sbiological control, biological invasion, formicidae, invasive ant, microsporidia, Paratrechina fulva | INTRODUCTIONTawny crazy ants (Nylanderia fulva (Mayr)) are invading the Gulf Coast region of the United States (Kumar et al., 2015). Nylanderia fulva Nylanderia fulva evolved in central South America where it can be a common member of the ant fauna (Calcaterra, Cuezzo, Cabrera, & Briano, 2010;Kumar et al., 2015;LeBrun et al., 2007). N. fulva colonies contain multiple queens and nest opportunistically in cavities in soil or in objects on the soil surface predisposing them to human transport (Zenner-Polania, 1990). This ant is omnivorous, preying on and scavenging insects and also relying heavily on sugary exudates of plants and homopteran insects (MacGown & Layton, 2010;Sharma, Oi, & Buss, 2013). Although males fly and are caught at lights, no flights of female reproductives have been reported for this species.Thus, new colonies are likely founded exclusively by intranidal mating and colony fission. As a result, isolated populations of N. fulva spread slowly averaging about 200 m of outward spread per year (LeBrun, Abbott, & Gilbert, 2013;Meyers, 2008). In the Gulf Coast region of the United States, these ants successfully invade both urban and natural environments. Invaded natural environments...

High-Resolution Population Genetic Structure of Tawny Crazy Ant (Nylanderia fulva Mayr: Hymenoptera: Formicidae) from the Origin in South America and Introduced Regions of the United States

“…For instance, genetically differentiated populations of green peach aphids (Myzus persicae Sulzer), Mediterranean fruit ies (Ceratitis capitata Wiedemann), and mountain pine beetles (Dendroctonus ponderosae Hopkins) have all been shown to vary in their susceptibility to pesticides and stress tolerance [49][50][51]. Recently, the application of a fungus-like microsporidian pathogen was found effective at decreasing and in some instances eliminating TCA populations [52][53][54]. Further investigation is required into the effectiveness of this biopesticide on other TCA populations.…”