Persistent effects of land-use history on myrmecochorous plant and epigeic ant assemblages across an ecoregional gradient in New York State

Forested landscapes increasingly comprise patches of differing land-use histories that include past stand-replacing anthropogenic disturbances such as logging, fire, or agricultural use. These disturbances affect community composition, and can disrupt trophic interactions among mutualistic guilds that differ in ecological requirements and mobility. However, few studies address the joint effects of past disturbance on spatial distributions of mutualistic guilds across spatial scales. We studied how past land-use history affected regional community patterns of ant-dispersed plants (myrmecochores) and their ant mutualists across a broad climatic gradient in New York State (spanning two ecoregions, 250 km distance, and elevations from 276 to 616 m above sea level). We found that changes in species composition of myrmecochores and ants along the full environmental gradient were closely coupled in residual stands that did not experience stand-replacing disturbance within the last 80 years. In contrast, species compositions of myrmecochores and ants varied independently of each other across this gradient in secondary stands (established after a stand-replacing disturbance similar to 60-80 years prior to this study), suggesting that past disturbance decoupled species compositions of the two guilds. Importantly, historical land-use diluted the effects of regional climatic gradient in secondary stands at broad scale, but its effect was too weak to observe it within individual ecoregions. Thus, weak hard-to-observe land-use history effects on community composition at local (subregional) scales can scale up to homogenize community composition at broader scales. Consequently, it is important to consider these emergent broad-scale effects of local land-use decisions in biodiversity conservation.

Automated summary

The past land-use history can affect the community composition of plants and ants in forested landscapes. However, there are limited studies on the combined effects of past disturbance on the spatial distributions of mutualistic guilds across different scales.