Modellierung der Artenvielfalt und biogeografischen Muster atlantischer Großforaminiferen: Prognostische Szenarien in Zeiten globaler Klimaveränderungen
Paläontologie
Zusammenfassung der Projektergebnisse
This first global-level species distribution modeling (SDM) of symbiont-bearing larger benthic foraminifera (LBF) suggests that current species richness in the Indo-Pacific Western Coral Triangle ecoregion is two to three times higher than in the Bahamas ecoregion, which is identified as the center of LBF diversity in the Atlantic. Modeling of present-day patterns of species richness also suggests that diversity in the eastern tropical Atlantic is not fully captured. This is supported by the finding of Operculina sp. through analyzing additional material from São Tomé and Príncipe. The genus Operculina is widespread and diverse in the Indo-Pacific, but its occurrence in the Atlantic has been widely questioned. The record from São Tomé now not only confirms its distribution in the Atlantic but is also the first documented record of this genus in the eastern tropical Atlantic. Further studies are needed to determine whether it is a distinct species or whether it belongs to a circumtropical species that also occurs in the Indo-Pacific. The future SDMs for different climate scenarios project a dramatic temperature-driven decline in low-latitude species richness and an increasing widening bimodal latitudinal pattern of species diversity. This is in line with studies on other tropical shallow-water marine taxa (e.g. corals, planktonic foraminifera). An increase of bimodality and increasing habitat fragmentation in low latitudes could lead to disruption of genetic connectivity among LBF populations. LBF species will face large-scale non-analogous climatic conditions compared to currently realized climate space in the near future, particularly in the central Indo-Pacific. While the central Indo-Pacific, now the stronghold of LBF diversity, is expected to be most pushed outside of the currently realized niches of most species, refugia may be largely preserved in the Atlantic. Potential refugia for Indo-Pacific LBF are located primarily in the northern South China Sea, the Northwest Australian Shelf, and the Southern Tropical Pacific. The modeling results also suggest that current and future LBF distribution and diversity patterns are driven by an interplay of different environmental parameters. This is supported by previous experimental studies tolerances of selected LBF species to changing environmental conditions and synergistic effects of combined stressors. The results of this project suggest that global biogeographic patterns of LBF are expected to undergo fundamental changes including loss of species in the course of climate change. Fragmentation of habitat and separation of populations might drive parapatric speciation in the Indo-Pacific in the aftermath of extinction. This first global-scale modeling approach also highlights the need to gain more knowledge about species-specific tolerances and how LBF species may be able to adapt to changing conditions. Further research and a better understanding of both aspects are key to anticipating the impacts of climate change on LBF worldwide.
