Print PageHabitat fragmentation disrupts ecological processes and is a driver of species extinctions. Corridors that connect otherwise isolated fragments of habitat may mitigate these negative effects on populations and communities. Although experimental work generally confirms that corridors increase movement of individuals between fragments, the impact of connectivity and increased movement at population and community levels remains unclear. In large scale, experimental landscapes we examined effects of connectivity and edge on the trophic ecology of a dietary generalist, the fire ant (Solenopsis invicta). Due to the breadth of resources consumed by S. invicta, their diet likely reflects food web structure. We quantified stable isotopes of carbon and nitrogen in ~9 colonies from each of 40 habitat fragments, some connected by a corridor and others unconnected, at different distances from edge. Mean and range of d15N and d13C and area of the convex polygon of d13C vs. d15N biplots are indicative of trophic position, basal source of carbon (C3 and C4 plants), and dietary breadth.
Results/Conclusions
S. invicta varied considerably in d15N among colonies (-1.03 to 4.47). Those from connected patches had higher range d15N values than those from unconnected patches. This difference may have been driven by higher species richness of plants in connected than in unconnected fragments. Indeed, we found a positive relationship between plant species richness and mean d15N of S. invicta. d13C values from S. invicta nests near fragment edges were lower than those from S. invicta nests far edges. This apparent edge effect suggests that distance to edge affects relative abundance C3 and C4 plants. Overall, our results show that connectivity and edge effects alter the trophic ecology of S. invicta.
