Colonization of gastropods on subtidal reefs depends on density in adjacent habitats, not on disturbance regime |
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| Authors: | Tuya, Fernando Wernberg, Thomas Thomsen, Mads S. |
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| Affiliation: | 1Department of Biology, University of Las Palmas de G.C., Campus Tafira s/n, 35019, Las Palmas de G.C., Canary Islands, Spain; 2Centre for Marine Ecosystems Research, Edith Cowan University, Joondalup Drive, Joondalup, WA 6027, Australia; 3 School of Plant Biology, University of Western Australia, Hackett Drive, Crawley 6009, WA, Australia; and 4Department of Marine Ecology, National Environmental Research Institution, PO Box 358, DK-400, Roskilde, Denmark |
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| Abstract: | Habitats dominated by algal canopies are often altered by physicaldisturbances of varying severity, changing environmental conditionsand biological processes. We used Artificial Seaweed Units (ASUs)to test whether severity of physical disturbances on algal canopiesaffects the post-disturbance colonization of gastropods on subtidalreefs. Specifically, we examined patterns of assemblage structureof gastropods to test the hypothesis that the extent and intensityof canopy removal affects the post-disturbance colonizationof ASUs, testing the consistency of these effects among fourregions encompassing a  6° latitudinal gradient in southwesternAustralia. Because adjacent habitats can act as a source ofnew colonists (either as drifting migrants or as a source ofpropagules) from the perimeter surrounding perturbed areas,we also predicted that patterns of colonization (types and totalabundances of colonizers) were influenced by the available poolof individuals at the scale of reefs. Three reefs were selectedwithin each region. On each reef, ASUs were placed in the centreof circular canopy clearings of different size (0, 3, 13 and50 m2) and intensity (50% vs 100%), and retrieved after3 months. Resulting assemblages occupying the ASUs were quantitativelyrepresentative of the adjacent (undisturbed), algal-associated,assemblages at the scale of reef. Within reefs, recruited assemblageslargely mimicked those associated with erect red algae. However,neither disturbance size nor intensity affected the colonizationpatterns across reefs and regions. These results suggest thatalgal-associated gastropods, regardless of the prevalent modeof dispersion, are resilient to physical disturbances to canopiesacross broad geographical regions as long as the pool of potentialcolonists is maintained. A high dispersal ability of gastropodslikely ensures a quick colonization of recovering algal habitats. (Received 14 April 2008; accepted 18 August 2008) |
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