The effects of urbanization on ant assemblages (Hymenoptera: Formicidae) associated with the Molson Nature Reserve, Quebec

Abstract

Urbanization causes the fragmentation of natural habitats into isolated patches surrounded by anthropogenic habitats. Fragment size and the intensity of human disturbance have been shown to affect both composition and diversity of arthropod communities, but most groups have been understudied. We investigated effects of urbanization on ant assemblages (Hymenoptera: Formicidae) in and around the Molson Reserve, a preserved maple-beech forest surrounded by residential properties near Montréal, Quebec. We studied how local ant assemblages differed in terms of composition, abundance, and species richness, depending on whether they were situated in the interior forest, in adjacent residential backyards, or at the edge between these two habitats. We also compared an intact forest interior with a younger and moderately disturbed forest (“buffer zone”) between the urban matrix and the interior forest. Few differences were detected between the buffer zone and the intact forest interior. Extrapolated estimates of species richness suggest that it is lowest in the forest interior and highest in urban zones. Community composition, as investigated with ordination analysis, revealed a clear difference between the fauna of urban sites and the fauna of edges and forest interiors, and analyzing the relative abundance of ants showed residential backyards to contain the most ants. Urban assemblages were characterized by several competitively dominant species, including one introduced or “tramp” species. The occurrence of aggressive and dominant species in urban sites and at the edges of the Molson Reserve could potentially interfere with the dispersal and immigration of ground-dwelling arthropods and negatively affect local diversity or community composition in isolated forest reserves in urban centres.

Effects of the Heterogeneity of the Landscape and the Abundance ofWasmannia auropunctataon Ground Ant Assemblages in a Colombian Tropical Dry Forest

“…Under these circumstances, W. auropunctata has largely displaced the ant fauna in some areas of the tropical forest in southwestern Colombia, accounting for up to 84% of the total captures. The increase in invasive or aggressive species is one of the effects of fragmentation that has been reported with greatest frequency [28,29,[54][55][56] and has had negative effects on the native fauna, decreasing the utilization of resources for other species of ants and other arthropods, thereby affecting plants and associated arthropods, either directly or indirectly [22]. Although W. auropunctata is a very common native species of neotropical forests that does not usually dominate entire assemblage [57][58][59], in disturbed areas such as agricultural and forestry systems, as well as in regions outside its native range, the little fire ant commonly has enormous populations [60,61] and is capable of exterminating ant populations over large areas [20].…”

Local and landscape drivers of arthropod abundance, richness, and trophic composition in urban habitats

“…The pavement ant, Tetramorium caspaetum, and the cornfield ant, Lasius neoniger, were the two most common ant species encountered. Both species form large colonies and tend to occur in open, disturbed habitats (Merickel and Clark 1994;Lessard and Buddle 2005). The pavement ant, in particular, may have dramatic impacts on the abundance and richness of other ants in urban areas and may have negative influences on both biodiversity and agricultural production (Uno et al 2010).…”

Insects Along Urban-Rural Gradients

“…Sanford et al ( 2008 ) noted that changes in abundance or nest density of SPUs might have substantial impacts on rate of water infi ltration in the region's montane forests. The importance of ants' ecological functions was shown also in a Canadian gradient from interior forest to adjacent residential yards, with the edge between these sampled as an intermediate ecotone (Lessard and Buddle 2005 ). All 24 ant species were collected by pitfall traps, with subsets of these found also in bait traps and by visual searches.…”