Coexistence of competing species of seaweed flies: the role of temperature

Abstract

1. Competition is shown to be occurring within and between the congeners Coelopa frigida and C.pilipes; it is noted that the two species frequently coexist despite ongoing competition.2. Observations on natural wrack-beds indicate that there is a marked difference in the distributions of the larvae: C.frigida larvae aggregate in cooler parts of the bed, C.pilipes in warmer parts. This difference in microdistribution reflects a broader-scale difference in the geographical distributions of the species -C.pilipes being the more southerly of the two.3. The larval distributions are shown to be caused primarily by the behaviour of the larvae themselves -not by choices made by ovipositing females, nor (at least to any great extent) by differential survival. 4.The different micro-distributions within beds constitute a form of niche difference which will cause competitive abilities to be frequency-dependent and hence have a stabilizing effect. It is possible that this effect may be supplemented by others; and, in particular, effects operating at the level of the 'linear metapopulation' may be worthy of further investigation both in Coelopa and in other coastal species.

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

“…For instance, the case depicted in ¢gure 2b (solid lines) shows the possibility of two stable parasitic interactions, with the peculiarity that each species can play both the victim and exploiter roles interchangeably. Could this be the situation found by Phillips et al (1995) in the C. frigida and C. pilipes association? Figure 3 provides a situation where both competition and parasitism are feasible under identical or under di¡erent environments.…”

Ecological non-monotonicity and its effects on complexity and stability of populations, communities and ecosystems

“…For example, leguminous or mycorrhizal plants benefit their neighboring plants by providing nitrogen or minerals and thus increase plant diversity or primary production (Bergelson, 1988;Bertness and Leonard, 1997;Díaz and Cabido, 2001;Fridley, 2001;Loreau et al, 2001;Tilman et al, 2001). Interaction between two seaweed flies, Coelopa frigida and C. pilipes, can change between acting as competitors or as amensalists (Phillips et al, 1995). As shown in Fig.…”

Asymmetric Interactions between Species of Seaweed Fly

“…A previous investigation into the interactions between the two species of coelopid examined here (Phillips et al 1995a) suggested that C. pilipes could inhibit C.frigida under certain conditions. Although their finding appears to disagree with the facilitation found in this investigation, there were a number of differences between the two studies, the most obvious being that Phillips study?…”

“…Adult flies were removed from each wrack sample by placing the whole sample in a bucket of concentrated saline and capturing the animals as they floated to the surface (Lavoie 1985;Phillips et al 1995a). Adult flies were removed from each wrack sample by placing the whole sample in a bucket of concentrated saline and capturing the animals as they floated to the surface (Lavoie 1985;Phillips et al 1995a).…”

“…A reticence to lay eggs in laboratory cultures has been found for both C. pilipes and T. zosterae, and when eggs are laid they tend to be laid singly (Egglishaw 1960(Egglishaw , 1961Leggett, 1993;Phillips et al 1995a). A reticence to lay eggs in laboratory cultures has been found for both C. pilipes and T. zosterae, and when eggs are laid they tend to be laid singly (Egglishaw 1960(Egglishaw , 1961Leggett, 1993;Phillips et al 1995a).…”