Not all forest edges are the same: agricultural edges have the greatest impacts on ant-mediated seed dispersal of temperate forest myrmecochores

Abstract Contemporary temperate forest ecosystems are fragmented and set within matrices of surrounding landscapes with various land uses, generating forest-edge habitats with distinct conditions that influence forest organisms and their interactions. Seed-dispersal by ants (myrmecochory) is a prominent interaction for temperate forest understory plants. Here, we examine the effects of forest edges in common surrounding landscapes in eastern North America on myrmecochory and whether environmental variables mediate the differences between edges and interior forest patches. We measured seed dispersal by ants, the abundance of the primary seed-dispersing ant, Aphenogaster sp., the presence of myrmecochores (plants with ant-dispersed seeds), the abundance of seed antagonists, and environmental variables in forests surrounded by agriculture, residential development, or low-maintenance landscapes. We found that organisms involved in myrmecochory were generally reduced at edges compared to forest interiors. Agricultural edges were the most altered, with the greatest differences in environmental conditions and loss of myrmecochores compared to interiors. Myrmecochory in forest interiors was unaffected by surrounding landscape types, and some edge types were more conducive to myrmecochory than others. These findings suggest that preserving forest interiors is important for the persistence of myrmecochory. Additionally, restoration of myrmecochores, which are reduced in many contemporary forests, would benefit from the increased seed-dispersal capacity of forest interiors and from the conditions of some edge types.