Turban snails as habitat for foliose algae: contrasting geographical patterns in species richness

Abstract

Understanding patterns of species richness is a major goal for ecologists, especially in space-limited habitats where many organisms live on top of others (epibiosis, e.g. by algae growing on gastropods in marine environments). We tested the hypotheses that species richness of epiflora on the gastropod Turbo torquatus would not differ between regions with similarly rich algal floras, and that epifloral richness would increase with increasing gastropod size. Macroalgal floras of Hamelin Bay (HB), Marmion (M), Jurien Bay (JB) and Kalbarri (K), Western Australia, ranged from ∼20 to 40 species reef–1 (JB = HB = M ≥ K). Epiflora on small T. torquatus (shell area <150 cm2) did not differ among regions but epifloral richness increased with increasing basibiont size. Large T. torquatus (>150 cm2) were only found in Hamelin Bay and Marmion, where epifloral richness differed substantially. Epifloral richness was positively related to basibiont size in Marmion but not in Hamelin Bay. However, densities of patellid limpets on large T. torquatus were ∼4× higher in Hamelin Bay than in Marmion, implying that limpet grazing suppresses epifloral richness. Epifloral richness on turbinids is not simply associated with regional species pools or gastropod size; rather, biological interactions at the scale of individual basibionts apparently govern broad scale patterns of epibiosis.

A sixth‐level habitat cascade increases biodiversity in an intertidal estuary

“…This conclusion is supported by past field experiments that have documented a positive relationship between the abundance of second-order habitat-formers and their inhabitants (Figure 4 Figure 1) for the two seaweeds and the colonial bryozoan, but not the two shell-forming molluscs. The latter result contrasts with other studies that have found strong size dependency of inhabitants attached to shells (Gribben et al, 2009;Martins et al, 2014;Thyrring et al, 2015;Wernberg et al, 2010).…”

“…It is possible that species interactions between these inhabitants, such as competition, or grazing, reduce size correlations. For example, limpets predominantly inhabit larger shells on which they likely exert considerable grazing pressure (Thomas et al, 1998;Wernberg et al, 2010). Furthermore, we did not find any inhabitants attached to very small Austrovenus recruits, highlighting that it takes time for inhabitants to colonize new biogenic substrates.…”

Communities and Attachment Networks Associated with Primary, Secondary and Alternative Foundation Species; A Case Study of Stressed and Disturbed Stands of Southern Bull Kelp

“…Finally, several shell-forming snails, including L. smaragda and Notoacmea spp, were found to be mobile primary (hosts) and secondary (attached) foundation species that were embedded within the larger macroalgal habitats. This result supports the findings of other studies that suggest that snails can be mobile foundation species that control small-scale patterns of biodiversity [41,[129][130][131][132]. In our study, the relative importance of shell-formers varied among habitats.…”

Large-scale facilitation of a sessile community by an invasive habitat-forming snail

“…Furthermore, B. australis recruits and N. pauperatus have the smallest shells and, in the case of N. pauperatus, are short-lived (Brearley 2005), i.e. sessile organisms have little space or time to settle and grow (Wernberg et al 2010). The high richness and densities of sessile organisms found on live adult B. australis with G. comosa attached is partly explained by sampling methodology; by default, this shell type always has a minimum of 'one species and several individuals' (=dense G. comosa).…”