Antlers on the Arctic Refuge: capturing multi-generational patterns of calving ground use from bones on the landscape

Life and death at Dmanisi, Georgia: Taphonomic signals from the fossil mammals

There are many hypotheses regarding influences on the early hominin biogeographic spread into Eurasia; among them is increased meat-eating. Dmanisi in Georgia is one of the rare Early Pleistocene sites in Eurasia, and here we present primary information and analysis of the medium and large mammal taphonomy, contributing information about site formation and the hominins' interaction with the fauna. Nearly 85% of the specimens come from the B1 stratum. Relative abundances of mammal families demonstrate some bias toward carnivores, especially Canis borjgali, and diverse Felidae species. Bones display little weathering. Post-depositional surface modifications and matrix obscure many bone surfaces, but carnivore tooth marking is the most common bone surface modification from the nutritive taphonomic phase. Tooth pits are large, in the size range of those made by modern Crocuta crocuta and Panthera leo. Breakage variables indicate most breaks occurred while the bones were still fresh, many by carnivore consumption. Fairly even limb bone representation of herbivores suggests carcasses were introduced to the site nearly whole. Hominin tool marks are present in low frequencies, but they suggest a variety of behaviors. These marks are found on Equus, Palaeotragus, Bison, large cervids, Pseudodama, Canis, and Mammuthus. Some were made by filleting proximal limb segments, and so are likely indicative of early access to carcasses, while other marks suggest scavenging. The Homo taphonomic variables resemble the rest of the taphonomic signatures from the site with little weathering, a slightly higher percentage of their bones are whole, but only a few have probable carnivore damage. The assemblage characteristics are compared to modern actualistic and experimental assemblages, and it is concluded that Dmanisi presents a palimpsest of hyena denning, felid activity, hominin meat-eating and likely natural deaths.

Historical Landscape Use of Migratory Caribou: New Insights From Old Antlers

Accumulations of shed caribou antlers (Rangifer tarandus) are valuable resources for expanding the temporal scope with which we evaluate seasonal landscape use of herds. Female caribou shed their antlers within days of giving birth, thus marking calving ground locations. Antler geochemistry (87Sr/86Sr) reflects the isotopic signature of regions used during antler growth, thereby providing data on a second component of seasonal landscape use. Here, we evaluate shed caribou antlers from the Coastal Plain of the Arctic National Wildlife Refuge, Alaska. The Central and Eastern regions of the Coastal Plain are calving grounds for the Porcupine Caribou Herd, while the Western Coastal Plain supports calving by the Central Arctic Herd. We found that antler 87Sr/86Sr from the Central and Eastern Coastal Plain were isotopically indistinguishable, while antler 87Sr/86Sr from the Western Coastal Plain was significantly smaller. For each region, we compared isotopic data for “recent” antlers, which overlap the bulk of standardized state and federal caribou monitoring (early 1980s and younger), with “historical” antlers shed in years predating these records (from the 1300s to the 1970s). For Porcupine Herd females calving in the Arctic Refuge, comparisons of antler 87Sr/86Sr through time indicate that summer ranges have been consistent since at least the 1960s. However, changes between historical and recent antler 87Sr/86Sr for the Central Arctic Herd indicate a shift in summer landscape use after the late 1970s. The timing of this shift is coincident with multiple factors including increased infrastructural development in their range related to hydrocarbon extraction. Accumulations of shed caribou antlers and their isotope geochemistry extend modern datasets by decades to centuries and provide valuable baseline data for evaluating potential anthropogenic and other influences on caribou migration and landscape use.

Taphonomic information from the modern vertebrate death assemblage of Doñana National Park, Spain

Modern death assemblages provide insights about the early stages of fossilization and useful ecological information about the species inhabiting the ecosystem. We present the results of taphonomic monitoring of modern vertebrate carcasses and bones from Doñana National Park, a Mediterranean coastal ecosystem in Andalusia, Spain. Ten different habitats were surveyed. Half of them occur in active depositional environments (marshland, lake margin, river margin, beach and dunes). Most of the skeletal remains belong to land mammals larger than 5 kg in body weight (mainly wild and feral ungulates). Overall, the Doñana bone assemblage shows good preservation with little damage to the bones, partly as a consequence of the low predator pressure on large vertebrates. Assemblages from active depositional habitats differ significantly from other habitats in terms of the higher incidence of breakage and chewing marks on bones in the latter, which result from scavenging, mainly by wild boar and red fox. The lake-margin and river-margin death assemblages have high concentrations of well preserved bones that are undergoing burial and offer the greatest potential to produce fossil assemblages. The spatial distribution of species in the Doñana death assemblage generally reflects the preferred habitats of the species in life. Meadows seem to be a preferred winter habitat for male deer, given the high number of shed antlers recorded there. This study is further proof that taphonomy can provide powerful insights to better understand the ecology of modern species and to infer past and future scenarios for the fossil record.

Genome sequence and comparative analysis of reindeer (Rangifer tarandus) in northern Eurasia

Reindeer are semi-domesticated ruminants that have adapted to the challenging northern Eurasian environment characterized by long winters and marked annual fluctuations in daylight. We explored the genetic makeup behind their unique characteristics by de novo sequencing the genome of a male reindeer and conducted gene family analyses with nine other mammalian species. We performed a population genomics study of 23 additional reindeer representing both domestic and wild populations and several ecotypes from various geographic locations. We assembled 2.66 Gb (N50 scaffold of 5 Mb) of the estimated 2.92 Gb reindeer genome, comprising 27,332 genes. The results from the demographic history analysis suggested marked changes in the effective population size of reindeer during the Pleistocene period. We detected 160 reindeer-specific and expanded genes, of which zinc finger proteins (n = 42) and olfactory receptors (n = 13) were the most abundant. Comparative genome analyses revealed several genes that may have promoted the adaptation of reindeer, such as those involved in recombination and speciation (PRDM9), vitamin D metabolism (TRPV5, TRPV6), retinal development (PRDM1, OPN4B), circadian rhythm (GRIA1), immunity (CXCR1, CXCR2, CXCR4, IFNW1), tolerance to cold-triggered pain (SCN11A) and antler development (SILT2). The majority of these characteristic reindeer genes have been reported for the first time here. Moreover, our population genomics analysis suggested at least two independent reindeer domestication events with genetic lineages originating from different refugial regions after the Last Glacial Maximum. Taken together, our study has provided new insights into the domestication, evolution and adaptation of reindeer and has promoted novel genomic research of reindeer.

Biology in the Anthropocene: Challenges and insights from young fossil records

With overwhelming evidence of change in habitats, biologists today must assume that few, if any, study areas are natural and that biological variability is superimposed on trends rather than stationary means. Paleobiological data from the youngest sedimentary record, including death assemblages actively accumulating on modern land surfaces and seabeds, provide unique information on the status of present-day species, communities, and biomes over the last few decades to millennia and on their responses to natural and anthropogenic environmental change. Key advances have established the accuracy and resolving power of paleobiological information derived from naturally preserved remains and of proxy evidence for environmental conditions and sample age so that fossil data can both implicate and exonerate human stressors as the drivers of biotic change and permit the effects of multiple stressors to be disentangled. Legacy effects from Industrial and even pre-Industrial anthropogenic extirpations, introductions, (de)nutrification, and habitat conversion commonly emerge as the primary factors underlying the present-day status of populations and communities; within the last 2 million years, climate change has rarely been sufficient to drive major extinction pulses absent other human pressures, which are now manifold. Young fossil records also provide rigorous access to the baseline composition and dynamics of modern-day biota under pre-Industrial conditions, where insights include the millennial-scale persistence of community structures, the dominant role of physical environmental conditions rather than biotic interactions in determining community composition and disassembly, and the existence of naturally alternating states.

Implications of Time-Averaged Death Assemblages for Ecology and Conservation Biology

Biologists increasingly appreciate the importance of community-level attributes in the functioning and temporal turnover of ecosystems, but data other than species richness are difficult to acquire over the habitat-to-regional and decadal-to-millennial scales needed to recognize biodiversity change, discriminate between natural and anthropogenic drivers, and inform theoretical and applied ecology. Death assemblages (DAs)—the actively accumulating organic remains encountered in present-day seabeds and landscapes, as distinct from permanently buried fossil assemblages—are an underexploited source of historical information at precisely these scales. Meta-analyses, dynamic modeling, and individual case studies, particularly of mollusks and mammals, reveal that DAs differ from censused living assemblages (LAs) primarily because they are temporally coarse, time-averaged samples, contrary to concerns that postmortem bias dominates. Temporal pooling predictably damps the ability of DAs to detect small-scale variation, but promotes their ability to inventory rare species; estimate the abundance structure of the metacommunity; document range changes; evaluate historic habitat use; and identify now-absent species, community states, and anthropogenically shifted baselines.