Data from: The functional effects of a dominant consumer are altered following the loss of a dominant producer

Human impacts on ecosystems are resulting in unprecedented rates of
biodiversity loss worldwide. The loss of species results in the loss of
the multiple roles that each species plays or functions (i.e., “ecosystem
multifunctionality”) that it provides. A more comprehensive understanding
of the effects of species on ecosystem multifunctionality is necessary for
assessing the ecological impacts of species loss. We studied the effects
of two dominant intertidal species, a primary producer (the seaweed
Neorhodomela oregona) and a consumer (the shellfish Mytilus trossulus), on
twelve ecosystem functions in a coastal ecosystem, both in undisturbed
tide pools and following the removal of the dominant producer. We modified
analytical methods used in biodiversity-multifunctionality studies to
investigate the potential effects of individual dominant species on
ecosystem function. The effects of the two dominant species from different
trophic levels tended to differ in directionality (+/-) consistently (92%
of the time) across the twelve individual functions considered. Using
averaging and multiple threshold approaches, we found that the dominant
consumer – but not the dominant producer – was associated with ecosystem
multifunctionality. Additionally, the relationship between abundance and
multifunctionality differed depending on whether the dominant producer was
present, with a negative relationship between the dominant consumer and
ecosystem function with the dominant producer present compared to a
non-significant, positive trend where the producer had been removed. Our
findings suggest that interactions among dominant species can drive
ecosystem function. The results of this study highlight the utility of
methods previously used in biodiversity-focused research for studying
functional contributions of individual species, as well as the importance
of species abundance and identity in driving ecosystem multifunctionality,
in the context of species loss.