Crab regulation of cross-ecosystem resource transfer by marine foraging fire ants

• Published in: Oecologia 2011-08, Vol.166 (4), p.1111-1119
• Main Authors: Garcia, Erica A., Bertness, Mark D., Alberti, Juan, Silliman, Brian R.
• Format: Article
• Language: English
• Subjects: Abiotic factors; Animal and plant ecology; Animal, plant and microbial ecology; Animals; Ants; Aquatic Organisms; Argentina; Biological and medical sciences; Biomedical and Life Sciences; Biotic factors; Boundaries; Brachyura; Carbon Isotopes - analysis; Coastal ecosystems; COMMUNITY ECOLOGY; Community ecology - Original Paper; Crabs; Crustacea; Decapoda; Ecological engineering; Ecology; Ecosystem; Ecosystem components; Feeding Behavior; Fire ants; Foraging; Formicidae; Fundamental and applied biological sciences. Psychology; General aspects; Hydrology/Water Resources; Invertebrates; Isotopes; Life Sciences; Marine; Marine ecosystems; Marine resources; Marine systems; Nitrogen Isotopes - analysis; Permeability; Plant Sciences; Polychaeta; Population Density; Shellfish; Solenopsis richteri; Stable isotopes; Terrestrial ecosystems
• ISSN: 0029-8549; 1432-1939
• DOI: 10.1007/s00442-011-1952-x

Permeability of boundaries in biological systems is regulated by biotic and/or abiotic factors. Despite this knowledge, the role of biotic factors in regulating resource transfer across ecosystem boundaries has received little study. Additionally, little is known about how cross-ecosystem resource transfer affects source populations. We used experiments, observations and stable isotopes, to evaluate: (1) the proportion of intertidal-foraging black fire ant (Solenopsis richteri) diet derived from marine sources, (2) how black fire ant cross-ecosystem resource transfer is altered by the dominant bioengineer in the intertidal, a burrowing crab (Neohelice granulata), (3) the top-down impact of these terrestrial ants on a marine resource, and (4) the effect of marine resources on recipient black fire ants. We found that more than 85% of the black fire ant diet is derived from marine sources, the number of intertidal foraging ants doubles in the absence of crab burrows, and that ants cause a 50% reduction in intertidal polychaetes. Also, ant mound density is three times greater adjacent to marine systems. This study reveals that cross-ecosystem foraging terrestrial ants can clearly have strong impacts on marine resources. Furthermore, ecosystem engineers that modify and occupy habitat in these ecosystem boundaries can strongly regulate the degree of cross-ecosystem resource transfer and resultant top down impacts.