Lasius alienus

Abstract: Nest-mounds of Lasius flavus, Lasius alienus and Formica rufibarbis are mainly on north-facing slopes with a markedly patchy distribution at Gimritz, northwest of Halle (Saale). Nest-mound soils had higher sodium and potassium levels but lower phosphorus and nitrogen levels than soils away from mounds. Moisture content was lower but soil pH was significantly higher in nest-mound soils. However, there was no difference in the relative abundance of plants of alkaline or acid soils growing on mounds compared to plants off mounds and no significant difference between the numbers of nitrophilous plants on and off mounds. Fewer plant species (35 spp.) in total occurred on mounds than off mounds (42 spp.). Plant species richness and total plant cover was significantly less on the nest-mounds than off the mounds. Similarly, the mean number of grass (1.39 spp dm−2) and forb species (1.13 spp dm−2) on mounds was lower than the mean number of grass (1.99 spp dm−2) and forb species (1.91 spp dm−2) off mounds. Some shrubs and forbs had higher occurrence and cover on the mounds, although only in Calluna vulgaris, Thymus serpyllum and Cerastium arvense was this difference particularly marked. Ant nest-mounds may favour plant species that cannot compete with tall grasses on unmanaged, set-aside meadows.

Abstract: Ant assemblages of a successional dune area (Tvarminne, south Finland) were analysed at three levels: the distribution of species among habitats, the distribution of colonies within habitats and the spatio-temporal distribution of individuals. The distribution of ant species among habitat patches representing different stages of succession is correlated with the composition of the epigeic fauna, the number and condition of dead twigs on the ground and the vegetation architecture. The composition of ant assemblages seems relatively independent of the plant species composition, and there are uncoordinated successional steps between the vegetation and ant communities. In the early successional stages interference competition is weak and insignificant, as indicated by the random spatial arrangement of colonies, the absence of postcompetitive niche segregation and the low encounter rates of ant workers on the ground and at baits. In the aggressive behavioural hierarchy, Formica cinerea is a submissive species as compared with either Formica sanguinea or Lasius alienus.

Abstract: (1) Ramsey Island (260 ha), Dyfed, Wales was surveyed by random quadrat sampling for ants' nests, and twelve variables of the habitat associated with each nest. (2) Nine species of ants from four genera were found. The average nest density was 0.057 m-2, with a maximum of 0 61 m-2. The distributions of the five commonest species are analysed in detail. (3) Nest dispersion is highly contagious (conforming to a logarithmic model), resulting from high nest densities in a few favourable sites. There is incomplete segregation of each species in the habitat, indicated by a random distribution of species packing. (4) Three physical and nine vegetational variables of the habitat are considered singly and in combination as niche dimensions. The variables are compared in a correlation matrix, and three principal components extracted. (5) The first component, representing an exposure factor differentiates the exposed coastal habitat of Lasius alienus F6rster from the sheltered sites of L. niger L. in heath and grassland vegetation. The second representing a drainage factor separates these two species from Myrmica scabrinodis Nylander and M. sabuleti Meinert. The third represents altitude and differentiates Lasius flavus F. from the other Lasius species, as well as Myrmica sabuleti from M. scabrinodis. (6) The nest dispersions of all Ramsey's ants are compared, and explained by specific and generic differences in nest building and foraging behaviour. The canopy effect of vegetation and the importance of rabbit grazing are discussed. (7) It is concluded that the dispersion and density of nests are broadly determined by the pattern of habitats on Ramsey and the factors influencing them, particularly exposure, moisture and rabbit grazing. The most widely distributed ants are generalist in their physical and vegetational resource requirements and can built a variety of nest structures. Lasius flavus typifies this group as it is able to nest at high and low densities in a range of habitats, either as the dominant species or in co-existence with as many as four other species.