Suburban sprawl: environmental features affect colony social and spatial structure in the black carpenter ant, Camponotus pennsylvanicus

Abstract

1. In social insects, the number of nests that a colony inhabits may have important consequences for colony genetic structure, the number of queens, sex allocation, foraging efficiency, and nestmate recognition. Within the ants, colonies may either occupy a single nest (monodomy) or may be organised into a complex network of nests and trails, a condition known as polydomy. 2. The current study is a large‐scale, long‐term, comprehensive field examination of various features of colony social and spatial structure in the facultatively polydomous black carpenter ant, Camponotus pennsylvanicus (DeGeer). The study examined the density, persistence, and the spatiotemporal distribution of colonies across a gradient of land disturbance associated with urban development. The temporal and spatial pattern of nest use was compared between fragmented landscapes where nesting sites were interspersed among human‐built structures (urban plots) and less disturbed landscapes with higher tree density (suburban plots). In addition, nesting site fidelity and changes in colony spatial structure were monitored over 7 years. 3. Long‐term monitoring and extensive sampling over a large spatial area allowed the first comprehensive insight into the spatiotemporal dynamics of colony and population structure in C. pennsylvanicus. A total of 1113 trees were inspected over 233 ha. Camponotus pennsylvanicus were active on 348 of the 1113 trees (31%) and these represented 182 distinct colonies. The colonisation rate remained relatively stable over 7 years suggesting that an equilibrium point had been reached. Relative to the suburban plots, tree density was 65% lower in the urban plots. The proportion of trees colonised by C. pennsylvanicus was significantly higher in the urban plots suggesting that intraspecific competition for nesting sites may be especially high in areas with lower tree density. Colony spatial structure also differed significantly between habitats and a higher incidence of monodomy was observed in the urban environment. The average number of trees per colony across all subplots was 1.95 (range 1–4) indicating that C. pennsylvanicus are weakly polydomous. 4. The composite picture that emerges for C. pennsylvanicus colonies in the urban habitat is a chain reaction of events: (i) the urban habitat has a lower tree density, (ii) lower tree density results in higher tree colonisation rate, (iii) higher tree colonisation rate results in simpler colony spatial structure (i.e. higher incidence of monodomy), and (iv) simpler colony spatial structure results in numerically smaller colonies. Long‐term monitoring of the spatiotemporal pattern of nest site use in selected colonies revealed a unique trend. While worker counts in selected colonies remained relatively stable throughout the course of the study, colony spatial structure changed considerably with 28% of colonies experiencing a change. Furthermore, the likelihood of detecting a change in colony spatial structure increased with the amount of time passing from the initial inspection...

Trap–treat–release: horizontal transfer of fipronil in field colonies of black carpenter ants, Camponotus pennsylvanicus

“…Trees selected for the study were located on the campus of Purdue University, West Lafayette, Indiana. The study site was a managed urban landscape that included mature trees interspersed among various campus buildings . Visual inspections were performed to identify trees occupied by black carpenter ants.…”

“…Trees with significant ant activity (> 25 ants per count) were tagged with numbered aluminum tags and subsequently used in the study. Previous research indicates that ∼ 35% of all trees within the study site are colonized by carpenter ants and the average number of workers observed on the trees is 45 ± 5 . In urban habitats, carpenter ants typically nest inside of live trees and colony size varies from 8000 to 12 000 individuals .…”

“…Mature carpenter ant colonies are frequently polydomous and are partitioned into parent and satellite nests . A previous study examined 1113 trees within the current study site and demonstrated that the average number of trees (nests) per colony was 1.95 (range 1–4); 32% of colonies nested in single trees, 45% nested in two trees, 22% nested in three trees, and 1% nested in four trees . In the current objective, the horizontal transfer of fipronil was investigated in colonies that comprised two nests – primary parent nest and secondary satellite nest.…”

Inferring polydomy: a review of functional, spatial and genetic methods for identifying colony boundaries

“…Another factor which may confound an assessment of polydomy by clustering is nest density. In several species, populations with a higher nest density have been shown to have a higher degree of polydomy than populations with a lower nest density (Banschbach and Herbers 1996a ; Bernasconi et al 2005 ; Buczkowski 2011 ; Cao 2013 ). A link between nest density and polydomy makes judging the effect of clustering more difficult, as spatial proximity and social structure are no longer independent.…”

Urbanization and wetland communities: applying metacommunity theory to understand the local and landscape effects

“…For instance, local processes tend to dominate in metacommunities composed of species with passive dispersal, while those constituted by primarily active dispersers are strongly influenced by regional processes (Cottenie ). Thus far, however, there have been few attempts to apply metacommunity theory to human‐modified landscapes, despite an abundance of evidence showing that human activity affects both local and regional processes (Parris ; Corbyn ; Buczkowski ).…”