IMPACT OF MORPHO-FUNCTIONAL GROUP REDUNDANCY ON THE ORIGINATION AND EXTINCTION OF CARIBBEAN CORALS

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.

Occurrences of shallow water corals of the Caribbean region were extracted from published literature and the Paleobiology Database (PBDB). Since a species can express more than one growth form, we use a presence-absence matrix of growth forms to establish morpho-functional groups. A PCA was performed on the morpho-functional groups to map their locations and visualize shifts over time and space across Caribbean ecoregions. We identified a total of 15 and 17 functional groups of the 127 theoretically possible combinations which encompassed 58 extant and 502 fossil species, respectively. Branching and Massive adjacent groups emerged as the largest occupants from both extant and fossil data. We noticed that in the fossil record 49.4 % of the species belonged to Massive adjacent groups, and this has consistently remained the dominant group throughout the Cenozoic, implying that the present-day dominance of massive groups could be associated with historical functional redundancy.Additionally, the trajectory of morpho-functional groups through the Cenozoic follows the general stages of reef development.

To assess the impact of functional groups on the emergence and extinction of species within, we used a Multivariate Birth-Death model. Our study revealed that despite the high species diversity of the Massive group there was no significant impact on either extinction or emergence. We also did not observe a significant impact on extinction of individuals within a group as a function of high diversity. This implies co-existence of similar species, since the diversity does not play a role in the origination or extinction of species within a morpho- functional group. However, we noticed multiple groups such as Branching and Laminar+massive had a significant impact on the extinction of co-exiting groups, suggesting that their present-day decline would severely impact the survival and proliferation of other functional groups.