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

Abstract

Concerns about widespread human-induced declines in insect populations are mounting, yet little is known about how land-use change modifies the dynamics of insect communities, particularly in understudied biomes. Here we examine how the seasonal patterns of ant activity, key drivers of ecosystem functioning, vary with human-induced land cover change on a subtropical island landscape. Using trap captures sampled biweekly from a biodiversity monitoring network covering Okinawa Island, Japan, we processed 1.2 million individuals and reconstructed activity patterns within and across habitat types. We determined that communities inside the forest exhibited more variability than those in more developed areas. Using time-series decomposition to deconstruct this pattern, we found that ant communities at sites with greater human development exhibited diminished seasonality, reduced synchrony, and higher stochasticity compared to those at sites with greater forest cover. We demonstrate that our results cannot be explained by variation in either regional or in situ temperature patterns, or by differences in species richness or composition among sites. We conclude that the breakdown of natural seasonal patterns of functionally key insect communities may comprise an important and underappreciated consequence of global environmental change that must be better understood across Earth's biomes.

Climate drives the long-term reproductive investment of a tropical ant community

“…As expected, community composition of male ants flying during the wet and dry seasons were significantly different. Seasonal effects on ant communities are widespread for tropical ant communities [48][49], especially in seasonally dry forests [11], varying both in temperature and precipitation regimes [50]. Nonetheless, in this long-term study (16 years), only a small directional trend was observed for community composition, and this occurred only for the wet season assemblages.…”

Divergent ecological responses to typhoon disturbance revealed via landscape‐scale acoustic monitoring

“…For example, our focal species differ in their seasonality and phenology, meaning that natural phenological differences may be in part responsible for the differences in species' typhoon responses we observed here. A recent study of Okinawan ants showed that ant activity was more seasonal in forested than developed field sites, and that these patterns in seasonality were driven by asynchronous seasonal dynamics of different ant species at the community level (Kass et al., 2023). This raises the possibility that land development degraded seasonal dynamics in the soundscape, possibly contributing to differences in the spatial divergence of SPL High among forested but less so among developed field sites.…”

Divergent ecological responses to typhoon disturbance revealed via landscape-scale acoustic monitoring

“…For example, our focal species differ in their seasonality and phenology, meaning that natural phenological differences may be in part responsible for the differences in species' typhoon responses we observed here. A recent study of Okinawan ants showed that ant activity was more seasonal in forested than developed field sites, and that these patterns in seasonality were driven by asynchronous seasonal dynamics of different ant species at the community level (Kass et al, 2023). This raises the possibility that land development degraded seasonal dynamics in the soundscape, possibly contributing to differences in the spatial divergence of SPLHigh among forested but less so among developed field sites.…”