Equatorial decline of reef corals during the last Pleistocene interglacial

Abstract

The Last Interglacial (LIG; ca. 125,000 y ago) resulted from rapid global warming and reached global mean temperatures exceeding those of today. The LIG thus offers the opportunity to study how life may respond to future global warming. Using global occurrence databases and applying sampling-standardization, we compared reef coral diversity and distributions between the LIG and modern. Latitudinal diversity patterns are characterized by a tropical plateau today but were characterized by a pronounced equatorial trough during the LIG. This trough is governed by substantial range shifts away from the equator. Range shifts affected both leading and trailing edges of species range limits and were much more pronounced in the Northern Hemisphere than south of the equator. We argue that interglacial warming was responsible for the loss of equatorial diversity. Hemispheric differences in insolation during the LIG may explain the asymmetrical response. The equatorial retractions are surprisingly strong given that only small temperature changes have been reported in the LIG tropics. Our results suggest that the poleward range expansions of reef corals occurring with intensified global warming today may soon be followed by equatorial range retractions.biodiversity | climate change | paleobiology C urrent global warming triggers substantial range shifts in both terrestrial and marine ecosystems (1-3). Scleractinian reef corals, like many other marine organisms, are currently experiencing poleward range expansions (4-7), but there is little evidence for range retractions in low latitudes. Whether this trend will persist into the future is difficult to predict, partly because of the lack of well-studied examples on past responses to rapid global warming. Range expansions of fossil reef corals with climate warming have been observed in the early to mid-Holocene (10 to 6 ky ago) (7) and during the Last Interglacial (LIG; ca. 125 ky ago) (8, 9). These previous studies highlighted particular taxa and regions, but the generality of the observations remains uncertain. Moreover, the balance between leading-edge range expansions (defined as species ranges moving toward the poles) and trailingedge contractions (defined as species ranges moving away from the equator) in these past warming phases is unexplored.Here we compare latitudinal patterns of global reef coral distributions and diversity (number of species) from raised reef terraces of the LIG [Marine Isotope Stage 5 (MIS 5)] with modern-day distributions to highlight the impact of past global warming. During most of the Pleistocene, global temperatures were colder than today (10-12), but glacial episodes are not well documented in reef corals because coral reefs of those times are largely submerged today (but see ref. 13). Interglacial warming led to polar ice melting and sea levels substantially higher than today (12, 14-16), leaving fossil coral reefs accessible on land. Tectonic uplift on some Pacific islands may also leave a record outside the peak interglacials, but not of p...

The origin and evolution of coral species richness in a marine biodiversity hotspot*

“…; Kiessling et al. ), and the CT may be a net larval source under current environmental conditions (Wood et al. ).…”

Unifying latitudinal gradients in range size and richness across marine and terrestrial systems

“…While numerous marine species coped with climate change by shifting latitudinally to track temperatures [65], many others persisted during Pleistocene cooling in high-latitude refugia [66][67][68][69], either at depths below potential ice damage or in relatively warmwater coastal embayments, before subsequent range expansion across latitudes or depths during warmer periods [70,71]. Although many marine population bottlenecks and some differentiation is attributable to Pleistocene sea-level drops and shifts in climate and circulation [72], speciation and global marine extinction was modest in the Pleistocene tropics compared to temperate extinction following the initiation of Pleistocene glacial cycles [73,74]. In sum, the broad species ranges in tropical bivalves seem to reflect gene flow across a shallow latitudinal gradient in temperature, with relatively minor lasting effects of Pleistocene climate.…”

Faunal breaks and species composition of Indo-Pacific corals: the role of plate tectonics, environment and habitat distribution

“…If so, older species might be more likely to straddle faunal breaks. To test this hypothesis, we included the species trait of genus age, as determined from the fossil record (species level ages cannot be obtained reliably [48] The likelihood of species with particular traits consistently crossing faunal breaks was analysed with a generalized linear mixed model (GLMM; electronic supplementary material, methods (g)).…”