Seasonal spatial dynamics and causes of nest movement in colonies of the invasive Argentine ant (Linepithema humile)

Abstract

1. Colony organisation and movement behaviour of the Argentine ant ( Linepithema humile ) was studied over 3 years in field populations in California and in captive colonies in the laboratory. This invasive species is highly polydomous and unicolonial; colonies consist of expansive and fluid networks of nests and trails. The spatial and temporal organisation of colonies may contribute to ecological dominance.2. Argentine ant nests and inter-nest trails shift in size, abundance, and location, so that colony networks are spatially contracted in the winter and expanded spring to autumn. Colonies occupy permanent sites; ants migrated to and from the same winter nest locations year after year, and occupied 30% of the same nests repeatedly during seasonal migrations.3. Nests were moved on average 2 -3 m. Forty-two per cent were occupied less than 1 month, 4% the entire study, and the other 54% lasted 3.9 ± 2.3 months (mean ± SD).4. Nests were located within 2 -4 m of woody plants, in warm sites in the winter and cool sites in the summer. Both humidity and food availability influenced nest-site choice in laboratory colonies. However, when faced with a trade-off between factors, the ants chose humid nest boxes over nest boxes near food, and ants moved nests only in response to changes in humidity and not distance to food.5. The results indicate that L. humile colonies are seasonally polydomous, and that nest movements are driven by changes in microclimate. Colony organisation maintains high local density and increases food supply, which may improve the competitive ability of L. humile colonies and reduce opportunities for species coexistence.

Habitat requirements for the conservation of wood cricket (Nemobius sylvestris) (Orthoptera: Gryllidae) on the Isle of Wight, UK

“…nearest neighbour distance). Studies on grassland species have revealed positive relationships with food availability and negative relationships with habitat distance, but differing results for vegetation structure and related abiotic conditions (Binzenhofer et al 2005;Strauss and Biedermann 2005;Heller and Gordon 2006). Studies specifically on woodland species have found similar relationships.…”

Nest connectivity and colony structure in unicolonial Argentine ants

“…We suggest that the group of nests within which ants travel and share food can be considered to be a colony. Our field observations of nests and trails indicate that colonies show regular patterns of organization and seasonal polydomy (Newell and Barber, 1913;Benois, 1973;Heller and Gordon, 2006). The seasonal spatial organization of nests within colonies was similar across different habitats and nest densities, with nests aggregated in large clusters at the scale of 3 -4 m in radius in the winter, spring and fall.…”

“…A different color of bait was used between trials. We used a 3-month interval to ensure many nests would still be active in the same locations between the first and second trial because Argentine ants move nest sites on average every 3 months (Heller and Gordon, 2006).…”

Polydomy enhances foraging performance in ant colonies

“…First, it is expected to reduce food search costs by increasing the total searched area while decreasing the overlap between foragers' search paths [5,6,[25][26][27][28][29][30]. Second, dispersed central-place foraging should decrease food transport costs by reducing the average distance between food sources and the nearest nest entrance [6,23,24,28,[31][32][33][34][35][36][37][38][39][40]. Third, foraging over a larger territory is considered beneficial by allowing colonies to diversify their food sources [20,21].…”