Biogeographic problem-solving reveals the Late Pleistocene translocation of a short-faced bear to the California Channel Islands

Abstract

An accurate understanding of biodiversity of the past is critical for contextualizing biodiversity patterns and trends in the present. Emerging techniques are refining our ability to decipher otherwise cryptic human-mediated species translocations across the Quaternary, yet these techniques are often used in isolation, rather than part of an interdisciplinary hypothesis-testing toolkit, limiting their scope and application. Here we illustrate the use of such an integrative approach and report the occurrence of North America’s largest terrestrial mammalian carnivore, the short-faced bear, Arctodus simus, from Daisy Cave (CA-SMI-261), an important early human occupation site on the California Channel Islands. We identified the specimen by corroborating morphological, protein, and mitogenomic lines of evidence, and evaluated the potential natural and anthropogenic mechanisms of its transport and deposition. While representing just a single specimen, our combination of techniques opened a window into the behavior of an enigmatic species, suggesting that A. simus was a wide-ranging scavenger utilizing terrestrial and marine carcasses. This discovery highlights the utility of bridging archaeological and paleontological datasets to disentangle complex biogeographic scenarios and reveal unexpected biodiversity for island systems worldwide.

Dietary niche separation of three Late Pleistocene bear species from Vancouver Island, on the Pacific Northwest Coast of North America

“…Despite popular depictions of U. arctos consuming salmon, fish are not essential to the survival of U. arctos , and when resources such as salmon are not available the bears rely on terrestrial vegetation, insects, freshwater fish and mammals (Davis, 1996). Furthermore, U. arctos can, as observed in some modern ecosystems, subsist on a completely vegetarian diet; some populations of U. arctos have been observed to subsist solely on vegetation across multiple years, despite the availability of other resources such as fish (Rode et al , 2001; Mychajliw et al , 2020).…”

“…The dietary requirements of now‐extinct Arctodus simus have been debated within the paleontological literature, with claims made for everything from an herbivorous to a hyper‐carnivorous diet based on morphological characteristics, microwear and paleopathological analyses, and stable isotope analyses of skeletal remains (Kurtén and Anderson, 1967; Emslie and Czaplewski, 1985; Bocherens et al , 1995; Fox‐Dobbs et al , 2008; Figueirido et al , 2010; Donohue et al , 2013; Figueirido et al , 2017). Existing stable isotope data for Arctodus are limited primarily to that of more northernly specimens from the Yukon and Alaska, with only one specimen from pre‐LGM Vancouver Island (see Bocherens et al , 1995; Matheus, 1995; Barnes et al , 2002; Fox‐Dobbs et al , 2008; Steffen and Harington, 2010; Schwartz‐Narbonne et al , 2015), although recently published data from a single Late Pleistocene specimen found on the California Channel Islands provide some insight into the diets of more southernly populations (Mychajliw et al , 2020).…”

Leveraging palaeoproteomics to address conservation and restoration agendas

“…Yet, the underrepresentation of dated megafaunal fossils in the archaeological and paleontological records currently problematizes precise estimates of extinction chronologies and geographical ranges for many megafauna taxa ( Price et al., 2018b ; Swift et al., 2019 ). As part of combined, multidisciplinary investigations, ZooMS studies have the potential to contribute significantly to our understanding of both, especially now that peptide markers for megafauna species are becoming increasingly widely available ( Buckley et al., 2011 , 2017a ; Van der Sluis et al., 2014 ; Welker et al., 2015b ; Mychajliw et al., 2020 ). The ability of ZooMS to identify ancient hominin remains (e.g., Brown et al., 2016 ; Welker et al., 2016 ) can also contribute to refining dispersal chronologies and clarifying the chronological overlap between human arrival and megafauna extinctions.…”

“…Of course, the addition of biomolecular techniques to study the fossil record does not resolve its inherently biased nature as a result of site-specific formation histories and preservation conditions ( Wolverton and Lyman, 2012 ), and palaeoproteomics is not a panacea for modern conservation efforts. Instead, it is the application of biomolecular approaches like palaeoproteomics in concert with more established methods like paleobiology, zooarchaeology, and palaeontology that provides a powerful new conservation tool, with the potential to significantly expand our knowledge and understanding of ecosystems in the past as well as the ecology of both extinct and extant species ( Evans et al., 2016 ; Faurby and Araújo, 2018 ; Mychajliw et al., 2020 ). As numerous examples cited here demonstrate, interdisciplinary studies that combine palaeoproteomics with additional biomolecular methods such as stable isotope or aDNA analysis also offer significant potential.…”

High-throughput microCT and ZooMS collagen fingerprinting of Scombrid bone from the Marquesas Islands

“…3). As with ZooMS analysis of other taxa such as bear (e.g., Mychajliw et al, 2020), some identifications can be more readily made using low m/z values that are present in poor collagen fingerprints, in this case that of the skipjack tuna which dominates this assemblage (although all four of the markers for this taxon were identified in all archaeological spectra in this study; Supplementary Tables S1-S2).…”