Morphological variation and different branch modularity across contrasting flow conditions in dominant Pocillopora reef-building corals

Abstract

Pocillopora corals, the dominant reef-builders in the Eastern Tropical Pacific, exhibit a high level of phenotypic plasticity, making the interpretation of morphological variation and the identification of species challenging. To test the hypothesis that different coral morphospecies represent phenotypes that develop in different flow conditions, we compared branch characters in three Pocillopora morphospecies (P. damicornis, P. verrucosa, and P. meandrina) from two communities in the Gulf of California exposed to contrasting flow conditions. Morphological variation and branch modularity (i.e., the tendency of different sets of branch traits to vary in a coordinated way) were assessed in colonies classified as Pocillopora type 1 according to two mitochondrial regions. Our results can be summarized as follows. (1) Pocillopora type 1 morphospecies corresponded to a pattern of morphological variation in the Gulf of California. Overall, P. damicornis had the thinnest branches and its colonies the highest branch density, followed by P. verrucosa, and then by P. meandrina, which had the thickest branches and its colonies the lowest branch density. (2) The differentiation among morphospecies was promoted by different levels of modularity of traits. P. verrucosa had the highest coordination of traits, followed by P. damicornis, and P. meandrina. (3) The variation and modularity of branch traits were related to water flow condition. Morphology under the high-flow condition was more similar among morphospecies than under the low-flow condition and seemed to be related to mechanisms for coping with these conditions. Our results provide the first evidence that in scleractinian corals different levels of modularity can be promoted by different environmental conditions.

From population connectivity to the art of striping Russian dolls: the lessons from Pocillopora corals

“…Nevertheless, the corallum macromorphology is not a diagnostic character in Pocillopora genus [e.g., Paz‐Garcia et al. (2015) or Gélin, Postaire, et al. (2017)].…”

Switch between Morphospecies of Pocillopora Corals

“…In an earlier study (Paz-García et al 2015), we showed that the Punta Galeras and Isla Gaviotas locations had different water flow conditions, regardless of the method of flow estimation (rate of dissolution of gypsum vs. dye release) or season (winter vs. summer). Thus, differences in water flow among the three locations were assessed using the rate of dissolution of gypsum (Muus 1968) as in PazGarcía et al (2015).…”

“…This observation, along with patterns of morphological variation between morphospecies seen under different flow regimes (Paz-García et al 2015), suggests that these recognizable morphospecies result from morphological plasticity. If so, then shifts in environmental conditions may trigger morphological changes between morphospecies.…”

“…A subset of changed (P. inflata, n p 14) and unchanged (P. damicornis, n p 6; P. verrucosa n p 5; P. meandrina, n p 5) colonies were selected randomly to verify the host lineage identity using two mitochondrial regions (an open reading frame [ORF] of as-yet-unknown function and the putative control region [CR] following protocols described in Paz-García et al 2015). Sequences generated in this study were deposited in GenBank, and accession numbers are KF985973 and KF985980.…”

“…Colonies bearing just one of these haplotypes (Pocillopora type 1) show several morphologies throughout their range (Pinzón et al 2013;Marti-Puig et al 2014). The high morphological variation seen within a single mitochondrial lineage thus seems especially pronounced in the eastern tropical Pacific Paz-García et al 2015).…”