Ants in space and time: Spatiotemporal niche changes facilitate species coexistence in semi-natural ecosystem complexes

Semi-natural farming systems with high conservation value offer a valuable opportunity to meet biodiversity conservation goals without compromising agricultural production. The high conservation value of such systems often roots in their increased local or landscape-level heterogeneity, which facilitates the coexistence of different species on a small spatial scale. Gaining a comprehensive understanding of the coexistence mechanisms operating in such systems is essential to mark future conservation trajectories. To facilitate this process, in this study, we aimed to uncover the interactive effects of spatial and temporal heterogeneity on community structuring mechanisms in wood-pastures, Europe’s widespread and heterogeneous semi-natural land-use form. Using ants as bioindicators, we connected species occurrence data with fine-scale measurements of local microclimatic conditions and quantified the seasonal niche breadths and overlaps of ant species forming communities in the four different habitat types (grasslands, solitary trees, forests, and forest edges) of three Central European wood-pastures. The niche quantification (performed for 28 ant species in total) was based on four-dimensional hypervolumes, with solar irradiation, air and soil temperature, and air humidity values of every species occurrence. Our results show that despite being located close to one another, the ant communities of the four different habitat types exhibited distinct patterns of seasonal realized niche dynamics, leading to community-wide temporal changes in niche hypervolumes and hypervolume overlaps (i.e., realized niche breadths and niche overlaps). The hypervolumes of dominant ants (characterized by high behavioral and ecological dominance) were mainly determined by the favorability of environmental conditions throughout the year, and in turn, their values shaped the realized niche breadths and overlap patterns of the intermediate and subordinate species. Importantly, the niche expansions and retractions of the dominant group changed the competitive pressure within the communities (quantified by hypervolume overlaps), opening up empty ecological niches to intermediate and subordinate species during periods characterized by suboptimal environmental conditions. Moreover, the niche dynamics showed a varying pattern across the different habitat types, implying that habitat structure and the associated environmental conditions interact with the effects of seasonality even on a small spatial scale. Our results uncover the interactive effects of spatial and temporal heterogeneity on coexistence mechanisms within wood-pastures. Given the distinct patterns in community dynamics and different community structuring mechanisms of the individual habitat types, wood-pastures and other complex landscapes have the potential to sustain different communities on a small spatial scale and thus boost landscape-level biodiversity.