MORPHO-FUNCTIONAL GROUP DIVERSITY OF CARIBBEAN CORALS AND THEIR IMPACT ON MACROEVOLUTIONARY PATTERNS

Using scleractinian growth forms for modern and fossil hermatypic corals, we analyze morpho-functional groups in established Caribbean ecoregions and assess their impact on macroevolutionary trends.

The Global Biodiversity Information Facility and published literature provided Caribbean occurrences from 1960–present, whereas the Paleobiology Database provided Cenozoic occurrences. Because a species can express more than one colony growth form, we used a presence-absence matrix of growth forms to establish morpho-functional groups. A total of 15 modern and 17 fossil morpho-functional groups were identified from 127 theoretically possible combinations, and these encompassed 58 modern and 502 fossil species. Branching and massive-related morpho-functional groups emerged as the largest components of reefs from both extant and fossil data.

PCA was performed on morpho-functional groups to map locations and visualize shifts over time and space across Caribbean ecoregions. PCA results revealed that occurrences of the branching group were reduced by half from the 1990s to present throughout the Caribbean, but species decline was uneven across ecoregions. Massive-adjacent groups from the same time period maintained coherence as robust morpho-functional groups and species diversity therein.

In the fossil record representing the Cenozoic, massive-adjacent groups remained consistently dominant, and 49.4% of species belonged to these groups. Results imply that present-day dominance of massive-adjacent groups could be associated with historical functional redundancy.

To further assess the impact of diversity of morpho-functional groups on the emergence and extinction of species within, we used a Multivariate Birth-Death model. A pilot study on four morpho-functional groups with highest species diversity (branching, massive-adjacent, laminar, free-living) revealed that, despite the dominance of massive-adjacent groups, there was no significant impact on extinction or emergence on other groups. However, branching groups, which included 20% of fossil species, showed a significant suppression of extinction rates for multiple functional groups. This suggests that present-day decline of the branching morpho-functional group would severely impact the persistence of other functional groups.