Oceanic-Scale Species Diversity of Living Benthic Foraminifera: Insights into Neogene Diversity, Community Structure, Species Duration, and Biogeography

Within-habitat (α) diversity of living benthic foraminifera in the Atlantic Basin increases as latitude decreases and generally increases with depth from shelf to abyss. Total populations (live + dead) show the same pattern and indicate that species are becoming more widespread with increasing water depth. Thus, within-habitat diversity increases with depth while regional (or γ) diversity is greater on the shelf (more communities). Community structure analysis indicates stasis and growth in shallower areas with stasis or decline in the abyss. The latitudinal gradient has existed for ca. 34 Ma; lower latitude deeper habitats have the longest species durations. For living populations an inverse relationship between density and diversity suggests scarcity of food is not sufficient to decrease diversity through extinction. For shallower-dwelling species, variability of solar energy can explain the latitudinal gradient. For deep-sea species, energy transfer from the surface, along with environmental stability over vast expanses, are plausible explanations for high diversity.