Intraspecific Relationships and Nest Mound Shape Are Affected by Habitat Features in Introduced Populations of the Red Wood Ant Formica paralugubris

Abstract

Ants belonging to the Formica rufa group build large nest mounds, which aid their survival during severe winters. We investigated whether different environmental features of the habitats affected the nest mound shape and the population structure. We assessed the shape of all the nest mounds and mapped inter-nest trails connecting mounds for three imported populations of Formica paralugubris in three forest habitats: fir-dominated, beech-dominated, and a mixture of fir and beech. Single-nest mounds were averagely smaller and flatter in the beech-dominated forest, probably because of lighter building materials. Nonetheless, by summing the volumes of all interconnected nests, the size was similar among all three sites. In fir- and beech-dominated forests, large nests were also central in the networks, suggesting a central place foraging model with these nests as reference. We finally performed aggression tests, and found that aggressiveness was significantly higher among nests belonging to the same population than between populations. The results highlight the plasticity of the species to adapt nest and colony structure to different environments. Additionally, it appears that none of these populations is unicolonial, as observed in various alpine sites, there and the observed patterns of aggression are coherent with the ‘nasty neighbor’ effect.

Assessing Molecular Diversity in Native and Introduced Populations of Red Wood Ant Formica paralugubris

“…Our results also confirmed the existence of considerable genetic admixture in all the surveyed populations, which was expected, based on the observations on the reproductive behaviour reported by Frizzi et al [ 41 ] and the findings on other European F. paralugubris populations as well as other RWA species [ 19 ]. The low genetic variance among nests (8% of total) suggests gene flow between them and is also consistent with budding reproductive behaviour, characterised by mating occurring in close proximity or even within the natal nest [ 20 ].…”

Comparative Analysis of Facial Coloration between Introduced and Source Populations of the Red Wood Ant Formica paralugubris

“…In the first case, nests-or subsets of them-should belong to different colonies that are genetically isolated from one another. Although F. paralugubris has been shown to be unicolonial at some sites in the Swiss Alps [63,64], this does not seem to be the case at the studied Apennine sites, where nonnegligible intra-population aggressiveness has been recently documented [40]. On the other hand, if-as in F. rufa-kinship is not correlated with the color pattern variability [33], the factors influencing coloration should be prevalently external and localized, such as sun exposure, humidity, or even the occurrence of an environmental stressor.…”

“…After an initial decline, the introduced populations started to expand, raising concerns about their impact on local communities [36][37][38]. Two features helping the adaptability of this species to the different Apennine environmental conditions are the plasticity of its diet and the ability to use different nest mound materials according to the habitat in which they dwell [39,40]. Here, we used a landmark-based morphological approach to investigate the interplay between inherited and acquired components of facial coloration.…”