Habitat overlap of enemies: temporal patterns and the role of spatial complexity

Abstract

Environmental heterogeneity can promote coexistence of conflicting species by providing spatial or temporal refuges from strong interactions (e.g., intraguild predation, competition). However, in many systems, refuge availability and effectiveness may change through time and space because of variability in habitat use by either species. Here I consider how the intensity of intraguild predation risk varies from day to night for aquatic insects that use both vegetated and open water habitats. Large (1,265 l) and small (42 l) mesocosms were used to test the hypothesis that Buenoa would choose an open-water habitat that minimized predation by the ambush predator Notonecta during the day, but that at night Buenoa would safely use both vegetated and open water. Regardless of container size, Notonecta remained in vegetated water during the day and exploited both habitats at night, despite exhibiting greatest instantaneous predation rates in open water during the day. In contrast, Buenoa maintained an even distribution throughout the mesocosms during day and night, even though habitat-specific predation risks were fivefold lower in open waters than in vegetation during the day and habitat-specific predation risk would have been reduced threefold by fully exploiting open waters. Thus, temporal heterogeneity was both beneficial and detrimental to Buenoa; darkness of night reduced predation, but spatial refuges also disappeared. Together, these patterns suggest that while environmental heterogeneity can dampen intense biotic interactions, enemies do not select habitats solely on the basis of conflict avoidance. Instead, it appears that habitat-specific variation in other biotic (e.g., visual predators) or physical factors (e.g., UV radiation) may also mediate species interactions by influencing habitat selection.

Methods for sampling benthic macroinvertebrates in tropical lentic systems

“…Theoretically, greater complexity will support greater diversity, richness and abundance of species because complex habitats possess more spatial resources (physical niches) than less complex ones (O'Connor 1991, Kostylev et al 2005, Shumway et al 2007). Complex habitats serve as predation refuges for benthic macroinvertebrates (Everett & Ruiz 1993, Taniguchi & Tokeshi 2004, and enhanced substrate heterogeneity should enable more species to coexist (Minshall 1984, Hampton 2004. Coconut brushes provide higher surface complexity, greater surface area and more interstitial spaces relative to artificial substrate samplers made from PVC or hardboard.…”

Predicting species interactions from edge responses: mongoose predation on hawksbill sea turtle nests in fragmented beach habitat

“…On the other hand, risk could be reduced through dilution effects if predators under-match prey abundance ( Foster & Treherne 1981;Inman & Krebs 1987). Habitat characteristics that change across the edge, such as the structural complexity of vegetation, may also affect predation risk by altering the ability of predators to detect or pursue prey (Hampton 2004;Bergman et al 2006).…”

Laboratory studies on intraguild predation and cannibalism among coccinellid larvae (Coleoptera: Coccinellidae)

“…There are many ecological studies on refuges that can be used to escape from predators as they play an important role in maintaining a high diversity of predators (Forrester & Steele, 2004;Denno & Finke, 2006). Thus, as pointed out by Elliott et al (1996), if competition is an important factor in determining coccinellid assemblages, refuges from competition probably exist for most species of coccinellid at plant (Schellhorn & Andow, 1999), field (Hampton, 2004) and landscape levels (Gardiner et al, 2009). In particular, Evans et al (2011b) review several examples of native coccinellids that show a niche-shift that allows them to survive in territories invaded by an exotic species of ladybird.…”