Entry for:NZMSS Student Awards
It is well-established that habitat-forming host-species characterized by widely different form-functional traits affect epiphytes and faunal community differently. However, the opposite hypothesis, that form-functionally similar habitat-forming hosts have similar effects on epiphytes and fauna, has been studied much less. We used a survey and two experiments to test if density or type of epiphytes modify the abundance and taxonomic richness of small gastropods associated with three co-occurring form-functionally similar canopy-forming seaweed hosts (Cystophora scalaris, C. torulosa, C. retroflexa).
In the survey host-epiphyte-gastropod associations were collected from different locations, sites and tide pools. We found that the three Cystophora species supported similar epiphyte and gastropod communities, and that the epiphytes again facilitated gastropods, across sites, locations and tidepools. The first experiment confirmed the positive effects of epiphytes on the abundance but not richness of gastropods. The second experiment documented that both density and type of epiphytes increased the abundance but not richness of gastropods. These results will be compared to gastropod communities associated with a co-occurring but morphologically different host, Hormosira banksii, and its obligate epiphyte Notheia anomala (work in progress). Finally, we will discuss results in the context of rocky shore ‘habitat cascades’, i.e. in the context of general ecological processes whereby primary biogenic habitat-formers (here Cystophora and Hormosira species) indirectly facilitate inhabitants (here gastropods) by providing structural support to secondary habitat-formers (here different densities and types of epiphytes).
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