GEOGRAPHIC RANGE CONTRACTIONS AND EXPANSIONS IN LARGE BENTHIC FORAMINIFERA

One of the most vexing issues in modern biogeography is the origin of large scale biodiversity patterns, with the centre of maximum marine biodiversity in the Indonesian-Australian Archipelago (IAA) as an important feature. Up to now biodiversity patterns have mostly been evaluated either on global or event based scales. However, organisms will primarily respond to their local environment. For example, during the, globally cooling, past 50 Million years the tropical biodiversity hotspot shifted from Europe to the Indo-West Pacific. Over this period generic diversity in large benthic foraminifera (LBF) decreased by roughly one third, whereas generic diversity almost doubled in the Indo-West Pacific. Here I will isolate regional from global drivers in the biological response to environmental change. I will focus on macroevolutionary processes underpinning biodiversity patterns, i.e. extinction, extirpation (local last occurrence or extirpation), origination, and immigration (local first occurrence, but the species ranges into older strata elsewhere).

Large benthic foraminifera have been shown to display comparable diversity trends with better known organisms, such as corals and molluscs. In addition, LBF are abundant and diverse in the fossil record of tropical shallow marine tropical environments, allowing both regional morphological analysis and diversity assessment in 1-2 Million years bins.

Preliminary results show that provinciality is highest in the Middle Eocene and Neogene, and that especially the Early Oligocene is characterized by a low provinciality. Within the paleotropics during the Eocene most first occurrences in the Western Tethys reflect speciation, and in the IWP immigration, and this is reversed in the Neogene. Following the Eocene-Oligocene boundary provinciality is reduced, at least in part due to rapid range expansions of surviving taxa.