Recruitment in epifaunal communities: an experimental test of the effects of species composition and age

Abstract

A key prediction to emerge from community assembly models is that resistance to invasion increases as the community matures. Three epifaunal communities of differing age were developed upon artificial substrata in the Firth of Forth, Scotland, to examine whether community age influenced the rate of establishment of new recruits. Four repeat experiments assessed the numbers of species and individuals invading a controlled amount of free space in these communities. The oldest communities were invaded by the smallest mean number of species in each experiment although these differences were significant for only 1 experiment. Multiple regression showed that age was the most significant predictor variable of the percentage coverage of new species. Because there were no significant effects on communities only a few centimetres away, the mechanisms by which community age controlled invasion in these experiments operate over small spatial scales. These data support the prediction that older communities are more resistant to invasion, but only if the term invasion includes further recruitment of species already present in the community. However, the experimental design does not distinguish between the effects of age per se, and those of different assemblage sequences. As expected, species responded in different ways to community age, and species composition played an important role in determining the success of invasion.KEY WORDS: Community · Age · Recruitment · Invasion · Assembly models · Successional theory Resale or republication not permitted without written consent of the publisherMar Ecol Prog Ser 307: [49][50][51][52][53][54][55][56][57] 2006 tance to invasion increases as the community matures (Post 1983, Post & Pimm 1983, Drake 1985, Kokkoris et al. 1999). This prediction is consistent with the models of succession described by Connell & Slatyer (1977), and is thus one of the more robust predictions to arise from assembly theory. Following Diamond (1975), Belyea & Lancaster (1999) inferred that the proportion of available resources consumed increases as species invade, and theoretically older communities should be more efficient and more difficult to invade. This appropriation of available resources and niche space is the mechanism underlying the increasing resistance to new recruitment in most models.The main driving force in the development of epifaunal sessile communities is competition for primary space, which is often a limiting factor (Dayton 1971). Space is likely to constitute a limiting resource because of the minimum requirements for attachment, feeding and growth of sessile organisms and because these species cannot move: competition for space in sessile species can still be intense even when the resource (primary space) is not strictly limiting (that is, preempted) (Turner & Todd 1993). As communities age, and the primary free space available for colonisation diminishes, community development can be regarded as a species-by-species replacement process that Greene & Schoener (1982) likene...

Response of intertidal macrofauna to multiple disturbance types and intensities – An experimental approach

“…Since the keystone role can be context, rather than species, specific, the removal of the same species from two apparently similar communities can have dramatically different effects. Similar disturbances in similar communities may also cause different outcomes through chance effects, such as different assembly or disassembly trajectories caused by different abundances of important species (Lindsay et al, 2006). For example, the order in which species are lost from a community might affect both abiotic and biotic interactions, which are known to structure benthic communities (Ostfield and LoGiudice, 2003).…”