• Energy Research

Too many meta-analyses of extinctions of giant kangaroos or huge sloths use data that are poor or poorly understood, warn Gilbert J. Price and colleagues. Too many meta-analyses of extinctions of giant kangaroos or huge sloths usedata that are poor or poorly understood, warn Gilbert J. Price and colleagues.

Ancient DNA has significantly improved our understanding of the evolution and population history of extinct megafauna. However, few studies have used complete ancient genomes to examine species responses to climate change prior to extinction. The woolly rhinoceros (Coelodonta antiquitatis) was a cold-adapted megaherbivore widely distributed across northern Eurasia during the Late Pleistocene and became extinct approximately 14 thousand years before present (ka BP). While humans and climate change have been proposed as potential causes of extinction [1-3], knowledge is limited on how the woolly rhinoceros was impacted by human arrival and climatic fluctuations [2]. Here, we use one complete nuclear genome and 14 mitogenomes to investigate the demographic history of woolly rhinoceros leading up to its extinction. Unlike other northern megafauna, the effective population size of woolly rhinoceros likely increased at 29.7 ka BP and subsequently remained stable until close to the species' extinction. Analysis of the nuclear genome from a ∼18.5-ka-old specimen did not indicate any increased inbreeding or reduced genetic diversity, suggesting that the population size remained steady for more than 13 ka following the arrival of humans [4]. The population contraction leading to extinction of the woolly rhinoceros may have thus been sudden and mostly driven by rapid warming in the Bølling-Allerød interstadial. Furthermore, we identify woolly rhinoceros-specific adaptations to arctic climate, similar to those of the woolly mammoth. This study highlights how species respond differently to climatic fluctuations and further illustrates the potential of palaeogenomics to study the evolutionary history of extinct species.

Despite decades of research, the roles of climate and humans in driving the dramatic extinctions of large-bodied mammals during the Late Quaternary period remain contentious. Here we use ancient DNA, species distribution models and the human fossil record to elucidate how climate and humans shaped the demographic history of woolly rhinoceros, woolly mammoth, wild horse, reindeer, bison and musk ox. We show that climate has been a major driver of population change over the past 50,000 years. However, each species responds differently to the effects of climatic shifts, habitat redistribution and human encroachment. Although climate change alone can explain the extinction of some species, such as Eurasian musk ox and woolly rhinoceros, a combination of climatic and anthropogenic effects appears to be responsible for the extinction of others, including Eurasian steppe bison and wild horse. We find no genetic signature or any distinctive range dynamics distinguishing extinct from surviving species, emphasizing the challenges associated with predicting future responses of extant mammals to climate and human-mediated habitat change.

Abstract Arctic marine ecosystems have undergone notable reconfigurations in response to Holocene environmental shifts. Yet our understanding of how marine mammal occurrence was impacted remains limited, due to their relative scarcity in the fossil record. We reconstructed the occurrence of marine mammals across the past 12,000 years through genetic detections based on sedimentary ancient DNA from four marine sediment cores collected around Northern Greenland, and integrated the findings with local and regional environmental proxy records. Our findings indicate a close association between the establishment of marine mammals at densities detectable in marine sediments and the deglaciation of marine environments at the onset of the Holocene. Further, we identified air temperature as a significant driver of community change across time. Several marine mammals were detected in the sediments earlier than in the fossil record, for some species by several thousands of years. During the Early-to-Mid Holocene, a period of past warmer climate, we recorded northward distribution shifts of temperate and low-arctic marine mammal species. Our findings provide unique, long-term baseline data on the occurrence of marine mammals around Northern Greenland, providing novel insights into past community dynamics and the effects of Holocene climatic shifts on the region’s marine ecosystems.

AbstractThe vulnerability of marine biodiversity to accelerated rates of climatic change is poorly understood. By developing a new method for identifying extreme oceanic warming events during Earth's most recent deglaciation, and comparing these to 21st century projections, we show that future rates of ocean warming will disproportionately affect the most speciose marine communities, potentially threatening biodiversity in more than 70% of current‐day global hotspots of marine species richness. The persistence of these richest areas of marine biodiversity will require many species to move well beyond the biogeographic realm where they are endemic, at rates of redistribution not previously seen. Our approach for quantifying exposure of biodiversity to past and future rates of oceanic warming provides new context and scalable information for deriving and strengthening conservation actions to safeguard marine biodiversity under climate change.

ABSTRACTThe Arctic environment plays a critical role in the global climate system and marine biodiversity. The region's ice‐covered expanses provide essential breeding and feeding grounds for a diverse assemblage of marine species, who have adapted to thrive in these harsh conditions and consequently are under threat from global warming. The bearded seal (Erignathus barbatus), including two subspecies (E. barbatus nauticus—Pacific and E. barbatus barbatus—Atlantic), is an ice‐obligate Arctic species using sea ice for many aspects of its life history, rendering it particularly vulnerable to sea ice loss. It is one of the least studied and hence enigmatic of the Arctic marine mammals, with little knowledge regarding genetic structure, diversity, adaptations, and demographic history, consequently hampering management and conservation efforts. Here, we sequenced 70 whole nuclear genomes from across most of the species' circumpolar range, finding significant genetic structure between the Pacific and the Atlantic subspecies, which diverged during the Penultimate Glacial Period (~200 KYA). Remarkably, we found fine‐scale genetic structure within both subspecies, with at least two distinct populations in the Pacific and three in the Atlantic. We hypothesise sea‐ice dynamics and bathymetry had a prominent role in shaping bearded seal genetic structure and diversity. Our analyses of highly differentiated genomic regions can be used to complement the health, physiological, and behavioural research needed to conserve this species. In addition, we provide recommendations for management units that can be used to more specifically assess climatic and anthropogenic impacts on bearded seal populations.