MEPS 574:167-179 (2017)  -  DOI: https://doi.org/10.3354/meps12170

ABSTRACT: The biotic interactions hypothesis (BIH) is often cited as a driver for the latitudinal diversity gradient (LDG), yet few studies have quantified biotic interactions using standardized methods across a broad geographic range. Similarly, despite increasing interest in the ecological properties of man-made marine habitats, no large-scale comparisons of ecological processes in natural versus artificial habitats have been performed. Here, we used a simple, standardized consumption assay to test the BIH and its consistency in natural habitats and docks across 17° of latitude. We deployed 1205 ‘squidpops’ underneath and 10-15 m away from marine docks in 4 mid-latitude locations on the US east coast (Florida, North Carolina, Massachusetts, and Maine), and monitored the squidpops for consumption of the bait after 1 and 24 h. Consumption rates decreased significantly with latitude and were consistently higher away from docks as compared to underneath docks after 24 h. Our results indicate that, when controlling for prey and habitat type, there is a consistent latitudinal gradient in consumption pressure for a specific group of consumers, which supports the BIH as a potential driver of the LDG. Furthermore, the geographically consistent reduced rates of consumption under docks compared to nearby habitats indicate generality in reduced predation pressure in docks vs. natural habitats, which has previously been reported at local scales. Our results suggest that, despite high local-scale variability, docks and squidpops may provide a useful avenue for future large-scale ecological studies and aid the understanding of ecological processes in highly developed coastal marine ecosystems.

KEY WORDS: Latitudinal gradient · Predation · Top-down control · Fish · Ecosystem function · Biodiversity · Pier · Anthropogenic habitat