Resilience of native ant community against invasion of exotic ants after anthropogenic disturbances of forest habitats

Abstract

The positive association between disturbances and biological invasions is a widely observed ecological pattern in the Anthropocene. Such patterns have been hypothesized to be driven by the superior competitive ability of invaders or by modified environments, as well as by the interaction of these factors. An experimental study that tests these hypotheses is usually less feasible, especially in protected nature areas. An alternative approach is to focus on community resilience over time after the anthropogenic disturbance of habitats. Here, we focused on ant communities within a forest to examine their responses after disturbance over time. We selected the Yanbaru region of northern Okinawa Island, which is a biodiversity hotspot in East Asia. We compared ant communities among roadside environments in forests where the road age differed from 5 to 25 years. We also monitored the ant communities before and after disturbance from forest thinning. We found that the species richness and abundance of exotic ants were higher in recently disturbed environments (roadsides of 5-15 years old roads), where the physical environment was warmer and drier. In contrast, the roadsides of 25-year-old roads indicated the potential recovery of the physical environment with cooler and moister conditions, likely owing to regrowth of roadside vegetation. At these sites, there were few exotic ants, except for those immediately adjacent to the road. The population density of the invasive species Technoymex brunneus substantially increased 1-2 years after forest thinning. There was no evidence of the exclusion of native ants by exotic ants that were recorded after disturbance. Our results suggest that local ant communities in the Yanbaru forests have some resilience to disturbance. We suggest that restoration of environmental components is a better strategy for maintaining native ant communities, rather than removing exotic ants after anthropogenic disturbance.

Breakdown in seasonal dynamics of subtropical ant communities with land-cover change

“…Indeed, we witnessed such an event in our 2-year period at one of our sites (Sefautaki Forest), where Pheidole megacephala , a notoriously impactful invasive ant, arrived and quickly reached high activity, raising variability of this site beyond what was typical of others with similar land-cover characteristics. Recent research in Yambaru Forest has documented resilience of native ant communities to disturbance based on surveys of invasions at developed areas after regrowth [ 88 ], so this site too may eventually recover to its previous structure. Thus, successive regime shifts in these more disturbed communities could occur over longer timescales, but only monitoring over more years would reveal such dynamics.…”

Breakdown in seasonal dynamics of subtropical ant communities with land-cover change

“…Indeed, we witnessed such an event in our two-year period at one of our sites (Sefautaki Forest), where Pheidole megacephala , a notoriously impactful invasive ant, arrived and quickly reached high abundance, raising variability of this site beyond what was typical of others with similar land-cover characteristics. Recent research in Yambaru Forest has documented resilience of native ant communities to disturbance based on surveys of invasions at developed areas after regrowth (Shimoji et al, 2022), so this site too may eventually recover to its previous structure. Thus, successive regime shifts in these more disturbed communities could occur over longer timescales, but only monitoring over more years would reveal such dynamics.…”

Increased dispersal explains increasing local diversity with global biodiversity declines

“…In contrast, many other ‘natural’ ecosystems in continental regions, which have had higher background immigration rates, appear relatively robust to invasion, compared to human‐altered ecosystems (which may still be in the ‘burn‐in period’) (e.g. MacDougall & Turkington, 2005; Shimoji et al, 2022).…”