GLOBAL BIOGEOGRAPHIC PATTERNS OF MODERN LARGER SYMBIONT-BEARING FORAMINIFERA (Invited Presentation)

Symbiont-bearing larger benthic foraminifera (LBF) are among the most important carbonate producers in the world's oceans and play an important role in tropical and subtropical reef and shelf systems. This presentation highlights key findings from more than 25 years of research on the biogeography of modern LBF, is based on the largest database available to date and includes a total of 105 morphospecies from nearly 5000 reference sites. For all LBF species, individual maps with precise data on their distribution over latitude and longitude are available. It was thus possible to identify the hotspot of LBF diversity and to recognize the spatial distribution of biogeographic provinces with their indicator species. Our results show that LBF species richness highly correlates with that of corals, peaks in the hotspot of the Coral Triangle as the world's most biodiverse marine ecoregion, and is two to three times higher than in the Bahamian ecoregion of the Atlantic Ocean.

In addition to the biogeographic distribution data, detailed species-specific data on the respective minimum and maximum temperature, salinity, and nutrient requirements are available for all LBF species. Interesting biogeographic patterns for different groups of LBF (e.g. nummulitids, alveolinids, peneroplids, calcarinids, amphisteginids) possibly controlled by their symbionts are revealed. The association of modern LBF with specific environmental variables provides guidance and vital information to interpret the fossil record.

To identify and evaluate potential distributions of taxa based on their specific environmental tolerances we applied Species Distribution Modeling (SDM). SDM using Maxent was applied to assess future species richness patterns on a global scale for the time periods 2040–2050 and 2090–2100 with a focus on Representative Concentration Pathway 6.0 (RCP) from the Intergovernmental Panel on Climate Change. The RCP 6.0 scenario projects mean surface temperature changes of +2.2°C by the year 2100. Our results project substantial range extensions, an increasing widening bimodal latitudinal pattern of species diversity, a temperature-driven decline in low-latitude species richness, and support hypothesis that biogeographic patterns of LBF will fundamentally change under future climate conditions.