American mastodon mitochondrial genomes suggest multiple dispersal events in response to Pleistocene climate oscillations

Abstract

Pleistocene glacial-interglacial cycles are correlated with dramatic temperature oscillations. Examining how species responded to these natural fluctuations can provide valuable insights into the impacts of present-day anthropogenic climate change. Here we present a phylogeographic study of the extinct American mastodon (Mammut americanum), based on 35 complete mitochondrial genomes. These data reveal the presence of multiple lineages within this species, including two distinct clades from eastern Beringia. Our molecular date estimates suggest that these clades arose at different times, supporting a pattern of repeated northern expansion and local extirpation in response to glacial cycling. Consistent with this hypothesis, we also note lower levels of genetic diversity among northern mastodons than in endemic clades south of the continental ice sheets. The results of our study highlight the complex relationships between population dispersals and climate change, and can provide testable hypotheses for extant species expected to experience substantial biogeographic impacts from rising temperatures.

A novel approach to combatting proboscidean ivory trafficking using a multiplex High-Resolution Melt (M-HRM) assay

“…The 3 African elephant composite melt profiles -P3, P8, and P9, were unique to African elephants, and the sequences of the 16S and Cytb melt peaks comprising those composite melt profiles were specific to African elephants. Although no mastodon sequence information was obtained in this study, we observed 1 mastodon-specific composite melt profile, P10, which consisted of 16S and Cytb melt peak sequences that were unique to American mastodon [20] in this study of limited sample size. Since Pacific mastodon was also observed to have a P10 composite melt profile, we can infer that the 16S and Cytb melt peak sequences of Pacific mastodon would likely be the same as they are for American mastodon, although further investigation is required to be certain.…”

“…Each composite melt profile, its corresponding melt peaks, and the relevant SNPs are presented in Table 4. Since the mastodon samples that yielded complete composite melt profiles (3 Pacific mastodon samples, and 1 American mastodon sample) failed to produce sequencing results at 16S and Cytb, mastodon sequence analysis relied on whole mitochondrial genome sequences of American mastodon [20]. All sequences produced by this study (N = 1062) were deposited in GenBank (https://www.ncbi.nlm.nih.…”

“…The Asian elephant (P4) S2 melt peak sequence is unique to Asian elephants, whereas the S2 melt peak sequence for African elephants and mammoths (P5-P7) is shared between African savanna and African forest elephants, and mammoths, and anticipated to be shared with the extinct straight-tusked elephant. The S3 melt peak sequence produced by African elephants (P8-P9) is specific to African savanna and African forest elephants only, and the anticipated mastodon (P10) S3 melt peak sequence from [20] is unique to American mastodon. The 54-bp Cytb site contained 11 of the 16 SNPs, and the four melt peaks observed at Cytb, C1-C4, appeared to be most informative for taxonomic identification.…”

Overkill, glacial history, and the extinction of North America’s Ice Age megafauna

“…Other animals underwent sometimesextensive range shifts (caribou and muskox no longer live in the southeastern United States, as each had in the Pleistocene), changes in abundance, and extirpation (14,24,28,29). Ancient DNA evidence shows there were population bottlenecks and declining genetic diversity in the Late Pleistocene among a number of extant and extinct taxa, in some instances, beginning well before the first appearance of humans in North America (30)(31)(32)(33)(34)(35).…”

“…Building a case Calculated adjusted residuals are in parentheses, significant values are in bold (data from Table 2). χ 2 = 6.659, df = 2, P = 0.036. will require high-resolution chronologies and ancient DNA evidence to determine when each species began its downward demographic spiral, and track its population dynamics and range through to its extinction (7,13,31,34,35). It will also require detailed, region-specific records of the pace and magnitude of tclimate change, and of changes in the species and structure of the biotic community (drawn from pollen, macrofossils, ancient environmental DNA, and other proxies) (24,28,49,64,65,67,68,99).…”