The Effects of Land Use on the Structure of Ground‐Foraging Ant Communities in the Argentine Chaco

Abstract

We examined the responses of a ground‐foraging ant community to a gradient of land‐use intensity in a grazing agroecosystem in the Chaco of northern Argentina. The gradient extended from a highly degraded condition characteristic of traditional grazing practices, through an area of less severe disturbance where grazing was less concentrated, to two areas in which grazing had been managed for 3 and 18 yr, respectively. Ground cover changed along this gradient from bare to litter‐covered, ground‐layer vegetation changed from sparse to a structurally complex mixture of grasses and forbs, and canopy cover increased in areas of intermediate grazing intensity and then decreased. Community diversity varied among the sites depending on both season and scale of analysis. Site‐scale ant species richness was slightly higher in sites of intermediate disturbance in the summer‐wet season but was much greater in the least disturbed site in the winter‐dry season. The same dry‐season pattern was evident in both species richness and diversity at the scale of transects within sites, whereas species richness at the scale of individual traps within transects was significantly lower at sites of intermediate disturbance than at either highly restored or highly degraded sites. Abundances of individual ant species and functional groups also changed along the land‐use gradient. Litter‐inhabiting cryptic species and specialized predators responded positively to grazing management, whereas opportunists and the hot‐climate specialist Forelius nigriventris were prevalent in highly disturbed areas. Other functional groups exhibited redundancy and species turnover along the gradient. Detrended correspondence analysis (DCA) revealed that the ant faunas at the extremes of the land‐use gradient were more similar than expected. We hypothesize that the interaction of local‐scale habitat features with historical and biogeographic influences may determine the responses of this ant community to land use, and that highly degraded areas may have conservation value because they are regional sources of arid‐adapted ants.

A comparison of the leaf-litter ant fauna in a secondary atlantic forest with an adjacent pine plantation in southeastern Brazil

“…A common effect of habitat modifi cation on the ant fauna is a change in abundance and species richness across functional groups (Bestelmeyer & Wiens 1996). The pine plantation is richer in species classifi ed as soil or litter omnivorous-dominants that also forage in the vegetation , such as Brachymyrmex, Camponotus and Solenopsis.…”

Inconsistent outcomes of heterogeneity-based management underscore importance of matching evaluation to conservation objectives

“…We used an existing dataset of five rangeland experiments in Oklahoma and Iowa, USA (McGranahan et al, 2012a Knopf and Miller (1994) Ant community composition affected by changes in bare ground Graham et al (2008) Litter cover Litter cover < 25% doubled success rate of Greater Prairie-chicken nests McKee et al (1998) Altered litter cover associated with altered ant community composition Bestelmeyer and Wiens (1996) Winter cover, greater soil moisture increase survival of grassland obligate butterflies Vogel et al (2010) sizes, and management schemes (Table 2). Although established independently, the basic structure of each experiment was consistent: each experiment consisted of a replicated treatment in which fire was applied in spatially discrete patches, and a replicated control reflecting conventional management with homogeneous fire regimes.…”

As formigas como indicadores biológicos do impacto humano em manguezais da costa sudeste da Bahia

“…A estrutura da comunidade de formigas é influenciada pela modificação da paisagem natural, tal como o desmatamento (MacKay et al 1991, Verhaagh 1991, e por uma ampla faixa de mudanças na forma de uso de todos os ecossistemas terrestres (Perfecto & Snelling 1995, Bestelmeyer & Wiens 1996, Silva & Brandão 1999. Esperase, então, que qualquer perturbação de origem humana provoque alterações na estrutura da comunidade de formigas nos manguezais, de forma similar aos descritos nos estudos citados.…”