Doris Nagel

Evidence for Reproductive Isolation between Cave Bear Populations

The European cave bear (Ursus spelaeus), which became extinct around 15,000 years ago, had several morphologically different forms. Most conspicuous of these were small Alpine cave bears found at elevations of 1,600 to 2,800 m. Whereas some paleontologists have considered these bears a distinct form, or even a distinct species, others have disputed this. By a combination of morphological and genetic methods, we have analyzed a population of small cave bears from Ramesch Cave (2,000 m altitude) and one of larger cave bears from Gamssulzen Cave (1,300 m), situated approximately 10 km apart in the Austrian Alps (Figure 1A). We find no evidence of mitochondrial gene flow between these caves during the 15,000 years when they were both occupied by cave bears, although mitochondrial DNA sequences identical to those from Gamssulzen Cave could be recovered from a site located about 200 km to the south in Croatia. We also find no evidence that the morphology of the bears in the two caves changed to become more similar over time. We suggest that the two cave bear forms may have represented two reproductively isolated subspecies or species.

First DNA sequences from Asian cave bear fossils reveal deep divergences and complex phylogeographic patterns

Until recently, cave bears were believed to have only inhabited Europe. However, recent morphological evidence suggests that cave bears’ geographic range extended as far east as Transbaikalia, Eastern Siberia. These Asian cave bears were morphologically distinct from European cave bears. However, how they related to European lineages remains unclear, stressing the need to assess the phylogenetic and phylogeographic relationship between Asian cave bears and their European relatives. In this work, we address this issue using a 227 base‐pair fragment of the mitochondrial control region obtained from nine fossil bone samples from eight sites from the Urals, Caucasus, Altai Mountains, Ukraine and Yana River region in Eastern Siberia. Results of the phylogenetic analyses indicate that (i) the cave bear from the Yana River is most closely related to cave bears from the Caucasus region; (ii) the Caucasus/Yana group of bears is genetically very distinct from both European cave bears and brown bears, suggesting that these bears could represent an independent species; and (iii) the Western European cave bear lineage reached at least temporarily to the Altai Mountains, 7000 km east of their known centre of distribution. These results suggest that the diversity of cave bears was greater than previously believed, and that they could survive in a much wider range of ecological conditions than previously assumed. They also agree with recent studies on other extinct and extant species, such as wolves, hyenas and steppe bison, which have also revealed higher genetic and ecological diversity in Pleistocene populations than previously known.

Influence of climate warming on arctic mammals? New insights from ancient DNA studies of the collared lemming Dicrostonyx torquatus.

Background Global temperature increased by approximately half a degree (Celsius) within the last 150 years. Even this moderate warming had major impacts on Earths ecological and biological systems, especially in the Arctic where the magnitude of abiotic changes even exceeds those in temperate and tropical biomes. Therefore, understanding the biological consequences of climate change on high latitudes is of critical importance for future conservation of the species living in this habitat. The past 25,000 years can be used as a model for such changes, as they were marked by prominent climatic changes that influenced geographical distribution, demographic history and pattern of genetic variation of many extant species. We sequenced ancient and modern DNA of the collared lemming (Dicrostonyx torquatus), which is a key species of the arctic biota, from a single site (Pymva Shor, Northern Pre Urals, Russia) to see if climate warming events after the Last Glacial Maximum had detectable effects on the genetic variation of this arctic rodent species, which is strongly associated with a cold and dry climate. Results Using three dimensional network reconstructions we found a dramatic decline in genetic diversity following the LGM. Model-based approaches such as Approximate Bayesian Computation and Markov Chain Monte Carlo based Bayesian inference show that there is evidence for a population decline in the collared lemming following the LGM, with the population size dropping to a minimum during the Greenland Interstadial 1 (Bølling/Allerød) warming phase at 14.5 kyrs BP. Conclusion Our results show that previous climate warming events had a strong influence on genetic diversity and population size of collared lemmings. Due to its already severely compromised genetic diversity a similar population reduction as a result of the predicted future climate change could completely abolish the remaining genetic diversity in this population. Local population extinctions of collared lemmings would have severe effects on the arctic ecosystem, as collared lemmings are a key species in the trophic interactions and ecosystem processes in the Arctic.

Differences in the Tooth Eruption Sequence in Hyaenodon (‘Creodonta’: Mammalia) and Implications for the Systematics of the Genus

ABSTRACT Specimens that give new information on the tooth eruption sequence in European Hyaenodon are described. These specimens show a marked difference from the tooth eruption sequence established for North American Hyaenodon. The eruption of p4 after p3 and m3 and the earlier eruption of the permanent canine in European specimens versus the eruption of p4 before p3 and m3 and the eruption of the permanent canine as the last tooth in North American specimens indicate divergent evolutionary pathways for New and Old World lineages. In conjunction with other skeletal differences, described in the literature, our findings support the need for a reanalysis of the taxonomy of Hyaenodon.

Enlightening complexity. The Dimylidae of Petersbuch 28

The Bavarian fissure filling Petersbuch 28 (Lower Miocene, MN 3/4) yielded a large assemblage of the dimylid Plesiodimylus aff. chantrei. This assemblage includes molars of three incompletely differentiated morphotypes, resembling Plesiodimylus huerzeleri, P. chantrei and P. bavaricus, respectively. This pattern is interpreted as due to ecological reasons and a small time averaging. The lower molars do not show such differentiation. Next to Plesiodimylus, Chainodus intercedens was found, but in far smaller numbers.

Palaeobiology of Hyaenodon exiguus (Hyaenodonta, Mammalia) based on morphometric analysis of the bony labyrinth.

Species of the extinct genus Hyaenodon were among the largest carnivorous mammals from the Late Eocene through Early Miocene in North America, Europe and Asia. The origin, phylogeny and palaeobiology of Hyaenodonta are still ambiguous. Most previous studies focused on teeth and dental function in these highly adapted species, which might be influenced by convergent morphologies. The anatomy of the bony labyrinth in vertebrates is generally quite conservative and, additionally, was used in functional–morphological studies. This study provides the first anatomical description of the bony labyrinth of the extinct European species Hyaenodon exiguus in comparison to selected extant carnivoran taxa discussed from a functional–morphological perspective. Hyaenodon exiguus may have occupied a hyaena‐like dietary niche with a semi‐arboreal lifestyle, based on the relative height, width and length of the semicircular canals of the inner ear. However, this contradicts previous functional–morphological studies focusing on the diameter of the canals, which presumably represent the signal of locomotion mode.

Functional morphological adaptations of the bony labyrinth in marsupials (Mammalia, Theria)

Diprotodontia represents the largest and ecologically most distinct order of marsupials occurring in Australasian being highly divers in size, locomotion, habitat preferences, feeding, and activity pattern. The spatial orientation in the habitat and therefore the three‐dimensional space is detected by the vestibular system of the inner ear, more precisely by the three semicircular canals. In this study, we investigated the bony labyrinth of diprotodontian and selected non‐diprotodontian marsupial mammals of almost all genera with noninvasive micro‐CT scanning and 3D‐reconstructions. In principal component analyses, the subterranean taxon can be separated from gliding and saltatorial taxa, whereas arboreal species can be separated from saltatorial specimens. The highest PCA loadings of this functional distinction are clearly found in the diameter of the semicircular canals, whereas the overall shape (height, width, length) of the semicircular canals is less important. Additionally, the investigated arboreal and fossorial species of South America are nested in the morphospace of the Australasian taxa. Even if a phylogenetic signal in the anatomy of the bony labyrinth cannot be excluded entirely, the main functional morphological signal of the vestibular system is found in the diameter of the semicircular canals. With the large dataset of extant marsupial mammals analysed here, the locomotion mode of extinct taxa can be inferred in future studies independent of any evidence of postcranial material.

Historical biogeography of the leopard (Panthera pardus) and its extinct Eurasian populations

BackgroundResolving the historical biogeography of the leopard (Panthera pardus) is a complex issue, because patterns inferred from fossils and from molecular data lack congruence. Fossil evidence supports an African origin, and suggests that leopards were already present in Eurasia during the Early Pleistocene. Analysis of DNA sequences however, suggests a more recent, Middle Pleistocene shared ancestry of Asian and African leopards. These contrasting patterns led researchers to propose a two-stage hypothesis of leopard dispersal out of Africa: an initial Early Pleistocene colonisation of Asia and a subsequent replacement by a second colonisation wave during the Middle Pleistocene. The status of Late Pleistocene European leopards within this scenario is unclear: were these populations remnants of the first dispersal, or do the last surviving European leopards share more recent ancestry with their African counterparts?ResultsIn this study, we generate and analyse mitogenome sequences from historical samples that span the entire modern leopard distribution, as well as from Late Pleistocene remains. We find a deep bifurcation between African and Eurasian mitochondrial lineages (~ 710 Ka), with the European ancient samples as sister to all Asian lineages (~ 483 Ka). The modern and historical mainland Asian lineages share a relatively recent common ancestor (~ 122 Ka), and we find one Javan sample nested within these.ConclusionsThe phylogenetic placement of the ancient European leopard as sister group to Asian leopards suggests that these populations originate from the same out-of-Africa dispersal which founded the Asian lineages. The coalescence time found for the mitochondrial lineages aligns well with the earliest undisputed fossils in Eurasia, and thus encourages a re-evaluation of the identification of the much older putative leopard fossils from the region. The relatively recent ancestry of all mainland Asian leopard lineages suggests that these populations underwent a severe population bottleneck during the Pleistocene. Finally, although only based on a single sample, the unexpected phylogenetic placement of the Javan leopard could be interpreted as evidence for exchange of mitochondrial lineages between Java and mainland Asia, calling for further investigation into the evolutionary history of this subspecies.