Asymmetric Interactions between Species of Seaweed Fly

Abstract

JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range of content in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new forms of scholarship. For more information about JSTOR, please contact support@jstor.org.. British Ecological Society is collaborating with JSTOR to digitize, preserve and extend access to Journal of Animal Ecology. Summary 1. This paper describes the colonization patterns of, and interactions between, three common species of British seaweed fly: the coelopids, Coelopafrigida and C.pilipes; and the sphaerocerid, Thoracochaeta zosterae. 2. All three species exhibited similar temporal patterns in abundance on wrack beds in the field: adult flies were more abundant in the first 4 days after wrack deposition and then again towards the end of the wrack bed cycle, coinciding with the emergence of the next generation. 3. Two forms of resource were presented to the flies, minced and chopped seaweed (Fucus serratus), under controlled environmental conditions. The species interacted so as to produce a dominance series, with C.frigida being the strongest species and T. zosterae the weakest. All pairwise interactions were extremely asymmetric, adding support to the growing awareness that this phenomenon is common in interactions between insects. 4. On chopped seaweed only, C.pilipes facilitated C.frigida, more than doubling the latter's emergent population size. This facilitation, in conjunction with the inhibition of C.pilipes by C.frigida, produced a contramensal (+, -) interaction. Suggestions are made as to how the facilitative effect may have been produced, but the exact mechanism is not yet understood. such as decaying fruit, dung and carrion. Wrack beds are accumulations of detached seaweed deposited on shore, usually during a high spring tide or storm. During their time on shore, the beds are utilized by a number of detritivorous animals and associated predators and parasites (Backlund 1945; Egglishaw 1965; Phillips & Arthur 1994). There are several species of Diptera which are typically associated with wrack beds. In Britain, the most commonly encountered of these seaweed flies are the coelopids, Coelopa frigida and C. pilipes, and the sphaerocerid, Thoracochaeta zosterae. These species coexist on both a regional (shore) and local (within-bed) scale, and this proximity suggests that they will inevitably encounter and interact with one another to varying extents.

Variable modes of facilitation in the upper intertidal: goose barnacles and mussels

“…In contrast, studies showing interspecific facilitation in organisms of similar sizes are very rare, particularly in animals (Bertness & Yeh 1994, Lively & Raimondi 1987, Hodge & Arthur 1997. In the case of salt marsh plants living under hypersaline conditions, interspecific facilitation between seedlings occurred when salt tolerant species reduced substrate salinity, which in turn allowed salt intolerant but competitively superior species to survive (Bertness & Yeh 1994).…”

Dynamics of transitions between population interactions: a nonlinear interaction alpha-function defined

“…Phillips et al (1995) reported that seaweed £ies, Coelopa frigida and C. pilipes, can interact either as competitors or as amensalists; in addition, the direction of the amensalism depends upon environmental conditions. Hodge & Arthur (1997) described how according to the resource presented to these £y populations the interaction can either be (+, 7) or (0, 7).…”

Macrofaunal colonisation of strandedDurvillaea antarcticaon a southern New Zealand exposed sandy beach

“…Other studies have demonstrated a significant change in the abundance and biomass of Coleoptera, dipteran adults and larvae on wrack over time (Inglis 1989;Chown 1996;Hodge & Arthur 1997;Catenazzi & Donnelly 2007;Garrido et al 2008). However, these studies investigated only dipteran or coleopteran assemblages (Chown 1996;Hodge & Arthur 1997;Garrido et al 2008), or the sampling method included the collection of meiofauna and associated larval stages (Inglis 1989;Catenazzi & Donnelly 2007) that were too small to be retained on 1-mm mesh sieves (Inglis 1989;Chown 1996). In this study, the biomass of Diptera differed significantly between sampling days, with highest biomass occurring during later stages.…”

“…For instance, in a study on dipteran assemblages on the north-east coast of England, adult abundance peaked at the beginning and end of the wrack cycle, with the adults found during later stages being the offspring of those that originally colonised the fresh wrack (Hodge & Arthur 1997).…”