Checking the landing zone: do invertebrate larvae avoid settling near superior spatial competitors?

Abstract

It has been hypothesized that larvae of benthic marine invertebrates may reduce their risk of post-settlement competition by avoiding superior competitors during settlement. Few studies, however, have directly compared the levels of larval settlement close to and away from established competitors. We conducted experiments in the New England subtidal to determine whether larvae of fouling organisms would avoid substrata (100 cm 2 PVC panels) with established adult colonies of the tunicates Botryllus schlosseri, Botrylloides violaceus, and Diplosoma listerianum compared to control substrata without tunicates. After panels had been exposed for 1 wk in the field, we assessed larval settlement on the entire surface of panels and within 1 cm of established tunicate colonies. We also monitored the fate of larvae that settled near established tunicates to determine if different tunicate species posed different risks of overgrowth to newly settled juveniles. Pair-wise comparisons revealed only 1 significant difference (out of 48 total analyses) when we examined levels of settlement on panels with tunicates relative to bare controls. We also found no significant differences in the number of settlers overgrown by different tunicate species. Thus, our results suggest that invertebrate larvae do not avoid settling near established dominant competitors (i.e. colonial tunicates). These results are in contrast to a previous study which had shown that larvae of competitively inferior species avoided settling near B. schlosseri.

Seasonal and multi-annual patterns of colonisation and growth of sessile benthic fauna on artificial substrates in the brackish low-diversity system of the Baltic Sea

“…The process is continuous, sequential and directional, and it involves the colonisation and extinction of species, the growth of individual components and increments of diversity, biomass and structure which eventually leads to a stable finale-the climax community (Odum, 1969;Sousa, 1980;Pacheco et al, 2010). Community development on hard substrates depends on colonisation success, which is related to juvenile-adult interactions and initial conditions (Bullard et al, 2004), interspecific competitive interactions for available space and resources (Valdivia et al, 2005), predation (Osman et al, 1992) and grazing (Benedetti-Cecchi, 2000). Succession can also vary following fluctuations in environmental factors, including water temperature and its dynamics (waves, currents), substrate availability and primary production, all of which render succession highly seasonal in many temperate and subtropical systems (Pacheco et al, 2010;Speight & Henderson, 2010).…”

Role of the sea anemone Metridium senile in structuring a developing subtidal fouling community

“…It is this variability, inherent in fouling communities, that has often generated inconsistent results and conflicting conclusions in previous studies of successional processes and the role of individual species in generating pattern (e.g. settlement: Grosberg 1981, Bullard et al 2004; species richness, free space, and invasion: Stachowicz et al 2002, Dunstan & Johnson 2004. This variability has often caused more focus on the pattern itself rather than on the underlying processes which cause these patterns.…”

Offspring Size Effects Mediate Competitive Interactions in a Colonial Marine Invertebrate

“…It is possible that the effects of settler size on colony growth persisted because of the availability of free space. Botrylloides violaceus is known to be a dominant competitor (Bullard et al 2004), and so it would be interesting to know if the effect of settler size on colony growth persists even in the presence of other fouling species.…”