Global distribution of coral diversity: Biodiversity knowledge gradients related to spatial resolution

Abstract

Biodiversity knowledge shortfalls, especially incomplete information on species distributions, can lead to false conclusions about global biodiversity patterns. Diversity estimation theory statistically uses species occurrence records and sampling completeness (coverage) to predict diversity in terms of species richness, dominance and evenness. We estimated Scleractinia coral species diversity at different spatial resolutions, based on 109,296 occurrences and range data for 697 species, using an incidence‐based Hill's numbers approach through a rarefaction and extrapolation technique. We found that spatial patterns of diversity estimates were dependent on a geographic scale. The latitudinal and longitudinal diversity gradients, particularly at finer spatial scales, differed from species range‐based coral biodiversity hotspots of previous studies. The western Indian Ocean was predicted to have the most coral species, with greater diversities than in the Indo‐Pacific Coral Triangle. We concluded that the identification of marine biodiversity hotspots is sensitive to species commission errors (from range maps) and biased sampling coverage. Moreover, estimates of the geographic distribution of species richness informed us of a set of priority areas (the northeastern coast of Australia, central Coral Triangle and coast of Madagascar) for future sampling of unknown coral species occurrence. Our findings of biogeographical survey priorities contribute to filling biodiversity shortfalls for tropical coral reefs through sampling completeness, and consequently for development of conservation planning.

Time Machine Biology: Cross-Timescale Integration of Ecology, Evolution, and Oceanography

“…Quantifying how and why biodiversity levels have changed over Earth history is fundamental to macroecology and macroevolution. Scientific ocean drilling samples have allowed for unprecedented insight into these dynamics on million-year timescales, particularly in response to large-scale global climate and tectonic changes ( Figure 2; Kucera and Schönfeld, 2007;Norris, 2000;Fraass et al, 2015;Lowery et al, 2020). The general correspondence between Cenozoic climate change and biodiversity levels across multiple marine clades suggests that climate, particularly temperature, controls diversification dynamics on long timescales (Box 2 and Figure 3).…”

“…For example, large-scale climatic shifts have modified one of the foremost patterns in ecology, the latitudinal biodiversity gradient (LBG), in which the number of species decreases from the equator to the poles (Hillebrand, 2004a,b;Saupe et al, 2019). In the ocean, LBGs are often characterized by an equatorial dip, resulting in a bimodal biodiversity pattern (Rutherford et al, 1999;Worm et al, 2005;Chaudhary et al, 2016Chaudhary et al, , 2017Worm and Tittensor, 2018;Rogers et al, 2020;Yasuhara et al, 2020). Growing evidence suggests the LBG was flatter during warm periods (e.g., Eocene, Pliocene) and steeper during cold periods (e.g., Last Glacial Maximum of 20,000 years ago; Yasuhara et al, 2012c;Fenton et al, 2016;Lam and Leckie, 2020;Meseguer and Condamine, 2020), potentially reflecting degree of climatic heterogeneity (Saupe et al, 2019).…”

“…Because of slow sedimentation in the deep sea (typically less than 10 cm per 1,000 years) and sediment mixing down to a depth of 10 cm (bioturbation), a typical 1 cm thick surface-sediment sample represents average deposition over centuries to millennia (Jonkers et al, 2019). Thus, the proportion of microfossils recording conditions of the Anthropocene (typically >~1950) in surface sediments is negligible, which means core-top sediments typically provide a global pre-industrial baseline for the state of marine communities in fossilized organisms (Jonkers et al, 2019;Yasuhara et al, 2020). Recently, Jonkers et al (2019) compared planktonic foraminifera assemblages collected from surface sediments that provide a pre-industrial baseline with assemblages collected from sediment traps that monitored particle flux to the seafloor over the last 40 years.…”

“…Climate change is expected to have an accelerating effect on the ocean, yet the challenges of using relatively short-term ecological data to understand long-term consequences to biodiversity and ecosystems remain significant. Sediment cores and associated microfossils can help elucidate links between climate and spatial biodiversity (e.g., Yasuhara et al, 2012cYasuhara et al, , 2020, extinction risks (e.g., Harnik et al, 2012;Finnegan et al, 2015), natural baselines (e.g., Yasuhara et al, 2012aYasuhara et al, , 2017b, and biotic consequences on evolutionary timescales (e.g., Ezard et al, 2011).…”

“…As a result, CLIMAP and related efforts (e.g., the mid-Pliocene PRISM project or Pliocene Research, Interpretation and Synoptic Mapping) have built comprehensive, global data sets of microfossil community censuses for several time periods in Earth history, including the present day, the Last Glacial Maximum, and the Pliocene (CLIMAP Project Members, 1976, 1984Dowsett et al, 1994Dowsett et al, , 2013. These data were seldom studied from a biological perspective initially but later proved critical for gaining insight into present (Rutherford et al, 1999;Fenton et al, 2016;Tittensor et al, 2010) and past (Yasuhara et al, 2012c(Yasuhara et al, , 2020 biodiversity patterns on global and regional scales.…”