Intertidal invertebrates in Western Australia

Abstract: Aims: Along the west coast of Australia, intertidal rock
platforms support high invertebrate diversities that provide vital
ecosystem services, yet patterns in diversity are not well understood.
Here, we document and examine the invertebrate assemblages on intertidal
rock platforms in Western Australia and delineate ecoregions according to
assemblage structure.  Location: West coast of Australia Taxon:
Invertebrates Methods: We recorded 406 invertebrate species from quadrat
and timed search surveys on 39 intertidal limestone platforms that span
16° of latitude. We analysed latitudinal variation in species assemblage
composition and multiple components of invertebrate diversity (alpha,
gamma and beta diversity) that relate to different spatial scales (local,
regional, bioregional) using multivariate analysis of variance and
distance-based linear models. Bioregions of similar invertebrate
assemblages were delineated using hierarchical cluster analysis with
unweighted pair-group methods using arithmetic averaged. Results: There
was a clear relationship between alpha and gamma diversity, with both
increasing towards the equator. Beta diversity was relatively high across
all sites, not reporting any significant variation with latitude,
highlighting how regional patterns can arise from sites with high local
variation. Our results indicate that the intertidal diversity aligns with
latitudinal diversity gradient theory, demonstrating how regional scale
processes influence patterns in diversity. Main conclusions: The
composition of species distributions across latitudes indicates that a
transition between tropical- and temperate-dominated assemblages occurs
between 27°S – 24°S, however further research is required to examine the
properties of the transition zone. Distinct groupings of invertebrate
assemblages were identified, which delineated the coast into five regions.
We established a comprehensive empirical understanding of invertebrate
assemblages along the west coast of Australia acts as a valuable baseline
to assess future change and aid in future management and conservation
efforts.