Fragmented Urban Wilderness Areas Build Bubbles of Ant Diversity and Pave the Way for Invasive Species

Ants are a diverse and abundant group of invertebrates that have remained prominent in tropical and temperate terrestrial environments, despite human development and habitat destruction. Massachusetts is home to approximately 100 ant species, but little is known about distribution patterns throughout the state. Human expansion has resulted in habitat fragmentation that is likely to develop interesting pockets of ant diversity. To assess the effects of urban expansion, we manually collected individuals throughout eastern Massachusetts, including city streets, woodlands, islands, bogs and marshes. We identified specimens to species, noted GPS location with geo-tagged images of the site, and categorized collection sites as urban, urban “wild," or conservation land. Twenty-seven species representing 15 genera have been collected in Greater Boston. We found a pattern of continually increasing species richness with sample number from wildlife sanctuaries, while diversity of species found in urban areas was much lower after collecting markedly fewer samples. The recently invasive European ant, Myrmica rubra, was found in urban sites, but not conservation land, alongside common native carpenter ants (Camponotus pennsylvanicus) and the older invasive pavement ant (Tetramorium caespitum). M. rubra was particularly abundant in the Boston Nature Center’s “urban island” setting (Mattapan, MA), which suggests that the combination of a minimum of land maintenance and a high proportion of non-native plants may create hotspots for future spreading of invasive ants. Each of the distinct habitat types seems to be sustaining unique species assemblages that may provide further insight into the distribution of Massachusetts ants.