Mammal virus diversity estimates are unstable due to accelerating discovery effort

Abstract

Host-virus association data form the backbone of research into eco-evolutionary drivers of viral diversity and host-level zoonotic risk. However, knowledge of the wildlife virome is inherently constrained by historical discovery effort, and there are concerns that the reliability of ecological inference from host-virus data may be undermined by taxonomic and geographical sampling biases. Here, we evaluate whether current estimates of host-level viral diversity in wild mammals are stable enough to be considered biologically meaningful, by analysing a comprehensive dataset of discovery dates of 6,571 unique mammal host-virus associations between 1930 and 2018. We show that virus discovery rates in mammal hosts are still either constant or accelerating, with little evidence of declines towards viral richness asymptotes in even highly-sampled hosts. Consequently, inference of relative viral richness across host species has been unstable over time, particularly in bats, where intensified surveillance since the early 2000s caused a rapid rearrangement of species' ranked viral richness. Our results show that comparative inference of host-level virus diversity across mammals is highly sensitive to even short-term changes in sampling effort. We advise caution to avoid overinterpreting patterns in current data, since our findings suggest that an analysis conducted today could feasibly draw quite different conclusions than one conducted only a decade ago.

Present and future distribution of bat hosts of sarbecoviruses: implications for conservation and public health

“…Revisions could rapidly lead to taxonomic changes and changes in conservation assessments. Similar rapid changes happen with viral surveillance, particularly for bat hosts [72,73]. Also, new species discoveries can indicate or alter sampling bias, since remote areas may be undersampled.…”

The science of the host–virus network

“…At most, 1% of mammal viruses have been described to date 9 and even fewer are known from other vertebrates. At such an early stage in viral discovery, even the most basic statistics, such as host-level viral richness estimates, may say more about sampling effort than the underlying biological reality 63,64 . When a new zoonotic virus emerges, researchers are disproportionately likely to sample related host species and viral taxa in the vicinity of the spillover event (bottom-up sampling bias).…”

Present and future distribution of bat hosts of sarbecoviruses: implications for conservation and public health

“…Furthermore, bat species continue to be discovered and described, which could rapidly change conservation assessments. Similar rapid changes happen with viral surveillance, particularly for bats [79,80]. Also, new species descriptions and discoveries can alter sampling bias, since remote areas may be undersampled.…”