EXPLORING SPATIAL PATTERNS OF MORPHOLOGICAL DISPARITY IN EXTANT COCCOLITHOPHORES

Coccoliths are the immediate interface between a coccolithophorid cell and its environment. It is thus reasonable to assume that coccolith morphology carries both an ecological and an evolutionary signal. I identify and investigate the spatial patterns of morphology in extant coccolithophores, asking whether some regions of the world have higher morphological diversity than others and how the morphological diversity of a family varies spatially. I analyze 68 discrete, binary, morphological characters of body coccoliths from 106 extant species, using SEM images available through Nannotax3 and other literature sources. I calculate disparity as the mean dissimilarity between species, using the Gower Distance, and generate an all-encompassing global coccolithophorid morphospace, plotted as principal coordinate axes. This approach allows me to focus on morphological patterns, as opposed to species patterns, and compare all coccolithophore families. I base my pelagic province scheme on Spalding et al. (Ocean & Coastal Management (2012) 60:19-30), wherein a province is a large area defined by spatially and temporally stable (or seasonally recurrent) oceanographic conditions hosting a distinct assemblage of species, and I tabulate presence/absence of a species in a given province based on observations from past literature for any area within that province. Although the average disparity values of all provinces are fairly close, my preliminary results show that the Kuroshio-Oyashio current has the highest average disparity of all provinces, the Indian ocean has a higher average disparity than other ocean basins, and Western boundary currents –usually warm, deep, and fast flowing– have a higher average disparity than other pelagic biomes, even when I exclude the Kuroshio-Oyashio current province. When I examine the morphospace occupation of an individual family, I find that it varies over space, even when the provinces compared have the same all-species average disparity. While one family may have a broad range of morphologies in a particular region, another family can have a more restricted range of morphologies in that same place, which suggests that the forces that influence the morphological disparity of a family are different in each area and are likely tied to environmental factors.