Complete mitochondrial genome of an Arctic Collared Lemming subspecies endemic to the Novaya Zemlya Archipelago, Russia

In this study, we present an announcement of Novaya Zemlya Collared Lemming Dicrostonyx torquatus ungulatus (von Baer, 1841) complete mitogenome. This rodent was described historically as an Arctic Collared Lemming subspecies endemic to Novaya Zemlya (Arctic Russia) but its taxonomic status was unclear due to the lack of available molecular data. Based on a comprehensive mitogenomic phylogeny of the Arctic Collared Lemming, we show that this insular population shares a highly divergent mtDNA sequence (total length 16,341 bp). Hence, it should be considered a valid subspecies of the Arctic Collared Lemming. Our findings support the hypothesis that the Novaya Zemlya Archipelago had served as a cryptic polar refugium for cold-tolerant terrestrial and freshwater taxa since the mid-Pleistocene or even earlier.

Late Pleistocene (MIS 3–4) climate inferred from micromammal communities and δ18O of rodents from Les Pradelles, France

The middle Paleolithic stratigraphic sequence of Les Pradelles (Charente, France) spans from the end of Marine Isotope Stage (MIS) 4 until the middle of MIS 3. Micromammal remains are present in all the stratigraphic levels, offering a rare opportunity to address the questions of both environmental and climatic fluctuations throughout this period. Climate modes were studied through the taphonomy, biodiversity and oxygen isotope compositions of phosphate (δ18O p ) from 66 samples of rodent tooth enamel. The δ18O p values from the lower sedimentary levels provide summer mean air temperatures of 19 ± 2°C (level 2/1) and of 16 ± 2°C (levels 2A, 2B and 4A). Within the middle of sequence (level 4B), a paleobiodiversity change can be identified with an increase of Dicrostonyx torquatus, which is associated with the largest amplitude in δ18O p values and the highest maximal δ18O p values. At the top of the sequence (level 5-2), a biodiversity change is observed with the increase of Microtus arvalis, but without any change in δ18O p values. The association of cold rodent species with unexpected high and large amplitudes in the δ18O p values of their teeth, possibly indicative of aridity, suggests their deposition during a Heinrich event.