Abstract
Biodiversity dynamics are shaped by a complex interplay between current conditions and historic legacy. The interaction of short- and long-term climate change may mask the true relationship of evolutionary responses to climate change if not specifically accounted for. These paleoclimate interactions have been demonstrated for extinction risk and biodiversity change, but their importance for origination dynamics remains untested. Here, we show that origination probability in marine fossil genera is strongly affected by paleoclimate interactions. Overall, origination probability increases by 27.8% [95% CI (27.4%, 28.3%)] when a short-term cooling adds to a long-term cooling trend. This large effect is consistent through time and all studied groups. The mechanisms of the detected effect might be manifold but are likely connected to increased allopatric speciation with eustatic sea level drop caused by sustained global cooling. We tested this potential mechanism through which paleoclimate interactions can act on origination rates by additionally examining a proxy for habitat fragmentation. This proxy, continental fragmentation, has a similar effect on origination rates as paleoclimate interactions, supporting the importance of allopatric speciation through habitat fragmentation in the deep-time fossil record. The identified complex nature of paleoclimate interactions might explain contradictory conclusions on the relationship between temperature and origination in the previous literature. Our results highlight the need to account for complex interactions in evolutionary studies both between and among biotic and abiotic factors.
Highlights
Habitat fragmentation and loss is correlated with the intensity of ecological interactions [15,16,17] and speciation rates [18, 19]. Building on these ecological concepts through which past climate might affect origination dynamics, we expect that the interaction between climate change and previous temperature trends is a strong determinant of origination rates in the deep-time fossil record
Our results show that the effect of fragmentation on origination rates is large when an increase in continental fragmentation adds to a previous long-term increase
Cooling-cooling paleoclimate interaction resulting in a drop in eustatic sea level due to glaciation leads to reduced continental shelf area and emerging barriers in this main habitat of the majority of the studied fossil groups
Summary
If short-term change adds to a long-term temperature trend in the same direction (e.g. a short-term cooling following a prolonged cooling trend), species are less likely to have adaptations to the climatic situation due to niche conservatism [7,8,9] This lack of adaptation to climatic conditions might result in bottleneck and subsequent founder effects, as well as ecological releases [10,11,12]. Habitat fragmentation and loss is correlated with the intensity of ecological interactions [15,16,17] and speciation rates [18, 19] Building on these ecological concepts through which past climate might affect origination dynamics, we expect that the interaction between climate change and previous temperature trends is a strong determinant of origination rates in the deep-time fossil record. To estimate whether this increase is caused by a reduction in available habitat space subsequently to cooling-cooling paleoclimate interaction, we analyze the effect of a proxy for shelf-area habitat space on origination rates using the same modeling framework
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