A Contemporary Review of the Taxonomy and Biogeography of Massive-Forming Porites in the Indo-Pacific

Corals of the genus Porites Link, 1807 are often considered difficult to identify to species level, largely due to their complex and historically unstable taxonomy. Much of this uncertainty stems from a long history of inconsistent species descriptions and revisions, which have blurred diagnostic boundaries between taxa. This is compounded by their very small corallite size, which limits the resolution of traditional morphological approaches and has historically precluded detailed morphometric comparisons. Together, these factors have resulted in persistent taxonomic ambiguity within the genus, making species-level identification challenging using morphology alone. Here, we take a two-phase approach to synthesising the taxonomic history of ecologically important massive species within the genus by revisiting original descriptions and reimaging type material to provide more consistent interpretations of morphological features and distinguishing characters between species. We focus on ten massive-forming species from the Indo-Pacific and provide the most comprehensive review of the full nomenclatural history of these species, along with the wider genus itself. We find that at least 22 characters are diagnostically informative for species-level discrimination within the type material examined, although their diagnostic value varies among species and character combinations. Importantly, wall architecture is one of the most useful characters, broadly separating the species into two groups: those with perforate (blistered) walls and those with reticulate walls. However, operationalising Porites taxonomy to robustly resolve species boundaries and refine estimates of species richness beyond type localities will require well-replicated integrative studies that combine molecular evolutionary evidence with ecological and reproductive traits at both regional and transoceanic scales. By building on the legacy of earlier systematists, this work fills a key knowledge gap and provides a robust morphological foundation for advancing Porites taxonomy, supporting more accurate species discovery and identification into the future.