From Broadway Avenue to Central Park: Ant diversity, invasions and diets across Manhattan’s urban habitat mosaic

Background/Question/Methods:

Human-modified ecosystems dominate inhabitable terrestrial ecosystems globally and most of the world’s humans live in cities. However, most ecological studies-to-date have focused on protected areas, and we know surprisingly little about the ecology of species living in urban environments. This lack of study in urban centers could lead to misinterpretations of ecological dynamics and evolutionary trajectories of species that co-occur with humans, where selective pressures from humans are likely highest. Most cities are comprised of habitat mosaics which include habitats with varying degrees of chronic stress. In this study, we sampled ant communities across parks and road medians of Manhattan to examine the following questions: (i) how do ant assemblages in the relatively low stress habitats in parks compare to those in surrounding, high stress road median environments? (ii) how does the occurrence of native and invasive ant species compare in Manhattan’s parks and medians? Because resource availability is likely to be very different in parks and medians, we additionally used bait stations (water, sugar water, salt water, amino acid solution & extra virgin olive oil) to examine the question: (iii) how do short term feeding choices and long-term diets of ants vary across the urban habitat mosaic?

 Results/Conclusions:

The most common ant species across Manhattan’s urban habitat mosaic were the exotic ants, Tetramorium sp. E and Nylanderia flavipes. Tetramorium sp. E was the most common ant collected in median habitats (present in 72% of samples), while N. flavipes was the most common species collected in parks (74% of samples). The within-site composition (α-diversity) of entire ant assemblages differed significantly between park and median sites. This pattern became even stronger when exotic ants were excluded from the analysis. Similarly, among site dissimilarity (β-diversity) was lower in medians than parks; a pattern driven by differences in the occurrences of native ant species. Additionally, ant food preferences shifted from sugars in parks to oils in medians. This change was most stark for T.sp.E, which displayed a strong preference for sugars in parks (92.1%), but completely shifted towards a preference for oil in medians (92.6%). In sum, these findings suggest that the ecology of local ant assemblages is significantly altered across sites with varying levels of chronic stress. As part of this ongoing research program, we will next investigate the community, ecosystem, and evolutionary consequences of these changes.