Exploring intraspecific and interspecific variation of coral reef algae using a novel trait-based framework

The development of trait-based approaches has accelerated our
understanding of how communities assemble, respond to environmental
change, and may best be managed in the Anthropocene. Understanding the
magnitude and pattern of interspecific variability forms a critical
underpinning of trait-based approaches while exploring intraspecific
variability can identify the potential of species to adapt to changing
environmental drivers. Our work is motivated by the critical need for a
novel conceptual framework for understanding the functional ecology of
macroalgae, as the current paradigm is still mired in functional group
models developed in the 1980s. Our objective was to quantify interspecific
and intraspecific functional trait variability in three common and
morphologically diverse species of tropical marine macroalgae by exploring
traits relating to the ecological functions of resource acquisition,
resistance to herbivory, and resistance to physical disturbance and the
tradeoffs between them. We quantified intraspecific and interspecific
variability of 11 functional traits for three common and morphologically
diverse species of tropical macroalgae from five fringing reefs of
Mo’orea, French Polynesia that were likely to capture a wide range of
environmental variability. Differences in traits among species and sites
were determined with PERMANOVA, visualized with NMDS, and tradeoffs
between pairs of traits explored with correlation. Finally, spatial
patterns among select traits across all species were quantified. Species
clustered together in distinctly different trait spaces driven by
tradeoffs among suites of functional traits. Two of three species had
considerable intraspecific variability, though this variability occurred
at different scales, while one clustered tightly. Exploration of
individual traits across species and sites revealed tradeoffs between two
strategies for resource acquisition, growing tall and strong vs investing
in large surface area. Synthesis: We captured novel patterns of
interspecific and intraspecific variability for tropical marine
macroalgae. We found fundamental differences in traits between species
that may represent ecological strategies while considerable intraspecific
variability demonstrates a wide range in abilities to respond to
environmental drivers. Overall, our work provides novel insights into
intra and interspecific trait variation that form an essential
underpinning for using a trait-based framework in a taxon that is
increasingly dominant on tropical reefs.