Surviving a Drought: Population Dynamics of \u3ci\u3eOchotona pallasi pricei\u3c/i\u3e in a Dry Steppe, Gobi Altai, Mongolia

Two distinct life history traits are described from the genus Ochotona, the group of “burrowing” species exhibiting high but fluctuating population densities and the “non-burrowing” species exhibiting relatively stable low population densities. The life history traits are linked to ecosystem dynamics with climatically variable steppe environments hosting “burrowing” species and relatively stable mountainous and rocky habitats hosting “non-burrowing” species. There are few intermediate species, living in both steppe and rocky environments. This study presents survival rates, reproductive rates and a tentative model of population dynamics for Ochotona pallasi pricei, an intermediate species with respect to habitat preference. We used Cormack-Jolly-Seber models on 153 trapped as well as observed individuals during 10 encounter occasions to estimate survival rates. The study period lasted from November 2000 to July 2002, including a severe drought summer in 2001. Reproductive rates are estimated based on observation of the 100 x 100 m2 study site. Population dynamics are simulated using a Leslie-Matrix with monthly time steps. Neither the drought conditions nor the harsh winter conditions showed an influence on the survival rates of the observed individuals. Instead, population density, sex, and age were explaining factors in the most parsimonious model. Independence of climatic conditions suggests that O. pallasi pricei exhibits traits of a “non-burrowing” species although living in a variable steppe environment. This sheds new light on the evolution of the behavioral traits of pikas, since the variability of the climate cannot predict the life history traits of the species. The behavioral traits may be more conservative than has been assumed previously. Survival during the drought summer is probably enabled by the storage of enough dry herbs and grasses in the burrows of the animals, while the territorial behavior of the species is the prerequisite of harvesting enough biomass to persist through the adverse climatic conditions of a potentially coming drought

Preface

Preface to Erforschung biologischer Ressourcen der Mongolei, band 9, 2005. First paragraph: The present volume 9 of ”Biologische Ressourcen der Mongolei” continues the cooperation between the National University of Mongolia, Ulaan Baatar, and German academic institutions, mainly led by the University of Halle-Wittenberg. Thus, the volume stands in a tradition stretching now over 40 years (described in the respective chapter written by Stubbe et al.), but also raises new issues and topics. The chapters provided by Ts. Jamsran, W. Hilbig, E. Jäger, M. Stubbe und A. Stubbe demonstrate nicely that this cooperation is not only based on continued institutional but also on personal commitment, as these scientists had been working together long before political changes in the early 1990s and have carried out joint projects ever since. Contributions provided by young authors originate mainly from work recently done in the Mongolian-German Research Station in the Gobi Gurvan Saykhan region

Preface

Preface to Erforschung biologischer Ressourcen der Mongolei, band 9, 2005. First paragraph: The present volume 9 of ”Biologische Ressourcen der Mongolei” continues the cooperation between the National University of Mongolia, Ulaan Baatar, and German academic institutions, mainly led by the University of Halle-Wittenberg. Thus, the volume stands in a tradition stretching now over 40 years (described in the respective chapter written by Stubbe et al.), but also raises new issues and topics. The chapters provided by Ts. Jamsran, W. Hilbig, E. Jäger, M. Stubbe und A. Stubbe demonstrate nicely that this cooperation is not only based on continued institutional but also on personal commitment, as these scientists had been working together long before political changes in the early 1990s and have carried out joint projects ever since. Contributions provided by young authors originate mainly from work recently done in the Mongolian-German Research Station in the Gobi Gurvan Saykhan region

The Kobresia pygmaea ecosystem of the Tibetan highlands – Origin, functioning and degradation of the world's largest pastoral alpine ecosystem: Kobresia pastures of Tibet

With 450,000 km2 Kobresia (syn. Carex) pygmaea dominated pastures in the eastern Tibetan highlands are the world's largest pastoral alpine ecosystem forming a durable turf cover at 3000–6000 m a.s.l. Kobresia's resilience and competitiveness is based on dwarf habit, predominantly below-ground allocation of photo assimilates, mixture of seed production and clonal growth, and high genetic diversity. Kobresia growth is co-limited by livestock-mediated nutrient withdrawal and, in the drier parts of the plateau, low rainfall during the short and cold growing season. Overstocking has caused pasture degradation and soil deterioration over most parts of the Tibetan highlands and is the basis for this man-made ecosystem. Natural autocyclic processes of turf destruction and soil erosion are initiated through polygonal turf cover cracking, and accelerated by soil-dwelling endemic small mammals in the absence of predators. The major consequences of vegetation cover deterioration include the release of large amounts of C, earlier diurnal formation of clouds, and decreased surface temperatures. These effects decrease the recovery potential of Kobresia pastures and make them more vulnerable to anthropogenic pressure and climate change. Traditional migratory rangeland management was sustainable over millennia, and possibly still offers the best strategy to conserve and possibly increase C stocks in the Kobresia turf. © 201

Nonuniform Late Pleistocene glacier fluctuations in tropical Eastern Africa

Today’s ice caps and glaciers in Africa are restricted to the highest peaks, but during the Pleistocene, several mountains on the continent were extensively glaciated. However, little is known about regional differences in the timing and extent of past glaciations and the impact of paleoclimatic changes on the afro-alpine environment and settlement history. Here, we present a glacial chronology for the Ethiopian Highlands in comparison with other East African Mountains. In the Ethiopian Highlands, glaciers reached their maximum 42 to 28 ka thousand years ago before the global Last Glacial Maximum. The local maximum was accompanied by a temperature depression of 4.4° to 6.0°C and a ~700-m downward shift of the afro-alpine vegetation belt, reshaping the human and natural habitats. The chronological comparison reveals that glaciers in Eastern Africa responded in a nonuniform way to past climatic changes, indicating a regionally varying influence of precipitation, temperature, and orography on paleoglacier dynamics

Phylogeography and allopatric divergence of cypress species (Cupressus L.) in the Qinghai-Tibetan Plateau and adjacent regions

Additional files can be found at http://www.biomedcentral.com/1471-2148/10/194Background Although allopatric speciation is viewed as the most common way in which species originate, allopatric divergence among a group of closely related species has rarely been examined at the population level through phylogeographic analysis. Here we report such a case study on eight putative cypress (Cupressus) species, which each have a mainly allopatric distribution in the Qinghai-Tibetan Plateau (QTP) and adjacent regions. The analysis involved sequencing three plastid DNA fragments (trnD-trnT, trnS-trnG and trnL-trnF) in 371 individuals sampled from populations at 66 localities. Results Both phylogenetic and network analyses showed that most DNA haplotypes recovered or haplotype-clustered lineages resolved were largely species-specific. Across all species, significant phylogeographic structure (NST > GST, P < 0.05) implied a high correlation between haplotypes/lineages and geographic distribution. Two species, C. duclouxiana and C. chengiana, which are distributed in the eastern QTP region, contained more haplotypes and higher diversity than five species with restricted distributions in the western highlands of the QTP. The remaining species, C. funebris, is widely cultivated and contained very little cpDNA diversity. Conclusions It is concluded that the formation of high mountain barriers separating deep valleys in the QTP and adjacent regions caused by various uplifts of the plateau since the early Miocene most likely promoted allopatric divergence in Cupressus by restricting gene flow and fixing local, species-specific haplotypes in geographically isolated populations. The low levels of intraspecific diversity present in most species might stem from population bottlenecks brought about by recurrent periods of unfavorable climate and more recently by the negative impacts of human activities on species' distributions. Our findings shed new light on the importance of geographical isolation caused by the uplift of the QTP on the development of high plant species diversity in the QTP biodiversity hotspot.Publisher PDFPeer reviewe

Evolutionary history of two rare endemic conifer species from the eastern Qinghai-Tibet plateau

BACKGROUND AND AIMS: Understanding the population genetics and evolutionary history of endangered species is urgently needed in an era of accelerated biodiversity loss. This knowledge is most important for regions with high endemism that are ecologically vulnerable, such as the Qinghai–Tibet Plateau (QTP). METHODS: The genetic variation of 84 juniper trees from six populations of Juniperus microsperma and one population of Juniperus erectopatens, two narrow-endemic junipers from the QTP that are sister to each other, was surveyed using RNA-sequencing data. Coalescent-based analyses were used to test speciation, migration and demographic scenarios. Furthermore, positively selected and climate-associated genes were identified, and the genetic load was assessed for both species. KEY RESULTS: Analyses of 149 052 single nucleotide polymorphisms showed that the two species are well differentiated and monophyletic. They diverged around the late Pliocene, but interspecific gene flow continued until the Last Glacial Maximum. Demographic reconstruction by Stairway Plot detected two severe bottlenecks for J. microsperma but only one for J. erectopatens. The identified positively selected genes and climate-associated genes revealed habitat adaptation of the two species. Furthermore, although J. microsperma had a much wider geographical distribution than J. erectopatens, the former possesses lower genetic diversity and a higher genetic load than the latter. CONCLUSIONS: This study sheds light on the evolution of two endemic juniper species from the QTP and their responses to Quaternary climate fluctuations. Our findings emphasize the importance of speciation and demographic history reconstructions in understanding the current distribution pattern and genetic diversity of threatened species in mountainous regions

Long-term fire resilience of the Ericaceous Belt, Bale Mountains, Ethiopia

Fire is the most frequent disturbance in the Ericaceous Belt (ca 3000–4300 m.a.s.l.), one of the most important plant communities of tropical African mountains. Through resprouting after fire, Erica establishes a positive fire feedback under certain burning regimes. However, present-day human activity in the Bale Mountains of Ethiopia includes fire and grazing systems that may have a negative impact on the resilience of the ericaceous ecosystem. Current knowledge of Erica–fire relationships is based on studies of modern vegetation, lacking a longer time perspective that can shed light on baseline conditions for the fire feedback. We hypothesize that fire has influenced Erica communities in the Bale Mountains at millennial time-scales. To test this, we (1) identify the fire history of the Bale Mountains through a pollen and charcoal record from Garba Guracha, a lake at 3950 m.a.s.l., and (2) describe the long-term bidirectional feedback between wildfire and Erica, which may control the ecosystem's resilience. Our results support fire occurrence in the area since ca 14 000 years ago, with particularly intense burning during the early Holocene, 10.8–6.0 cal ka BP. We show that a positive feedback between Erica abundance and fire occurrence was in operation throughout the Lateglacial and Holocene, and interpret the Ericaceous Belt of the Ethiopian mountains as a long-term fire resilient ecosystem. We propose that controlled burning should be an integral part of landscape management in the Bale Mountains National Park

Revisiting afro-alpine Lake Garba Guracha in the Bale Mountains of Ethiopia:Rationale, chronology, geochemistry, and paleoenvironmental implications

Abstract: Previous paleolimnological studies demonstrated that the sediments of Garba Guracha, situated at 3950 m asl in the afro-alpine zone of the Bale Mountains of Ethiopia, provide a complete Late Glacial and Holocene paleoclimate and environmental archive. We revisited Garba Guracha in order to retrieve new sediment cores and to apply new environmental proxies, e.g. charcoal, diatoms, biomarkers, and stable isotopes. Our chronology is established using 210Pb dating and radiocarbon dating of bulk sedimentary organic matter, bulk n-alkanes, and charcoal. Although bedrock was not reached during coring, basal ages confirm that sedimentation started at the earliest ~ 16 cal kyr BP. The absence of a systematic age offset for the n-alkanes suggests that “pre-aging” is not a prominent issue in this lake, which is characterised by a very small afro-alpine catchment. X-ray fluorescence scans and total organic carbon contents show a prominent transition from minerogenic to organic-rich sediments around 11 cal kyr BP coinciding with the Holocene onset. While an unambiguous terrestrial versus aquatic source identification seems challenging, the n-alkane-based Paq proxy, TOC/N ratios, δ13C values, and the sugar biomarker patterns suggest a predominantly autochthonous organic matter source. Supraregional climate events, such as the African Humid Period, the Younger Dryas (YD), a 6.5 cal kyr BP short drying event, and the 4.2 cal kyr BP transition to overall drier climate are recorded in our archive. The Garba Guracha record suggests that northern hemisphere forcings played a role in the Eastern African highland paleoclimate

Surviving a Drought: Population Dynamics of \u3ci\u3eOchotona pallasi pricei\u3c/i\u3e in a Dry Steppe, Gobi Altai, Mongolia

Two distinct life history traits are described from the genus Ochotona, the group of “burrowing” species exhibiting high but fluctuating population densities and the “non-burrowing” species exhibiting relatively stable low population densities. The life history traits are linked to ecosystem dynamics with climatically variable steppe environments hosting “burrowing” species and relatively stable mountainous and rocky habitats hosting “non-burrowing” species. There are few intermediate species, living in both steppe and rocky environments. This study presents survival rates, reproductive rates and a tentative model of population dynamics for Ochotona pallasi pricei, an intermediate species with respect to habitat preference. We used Cormack-Jolly-Seber models on 153 trapped as well as observed individuals during 10 encounter occasions to estimate survival rates. The study period lasted from November 2000 to July 2002, including a severe drought summer in 2001. Reproductive rates are estimated based on observation of the 100 x 100 m2 study site. Population dynamics are simulated using a Leslie-Matrix with monthly time steps. Neither the drought conditions nor the harsh winter conditions showed an influence on the survival rates of the observed individuals. Instead, population density, sex, and age were explaining factors in the most parsimonious model. Independence of climatic conditions suggests that O. pallasi pricei exhibits traits of a “non-burrowing” species although living in a variable steppe environment. This sheds new light on the evolution of the behavioral traits of pikas, since the variability of the climate cannot predict the life history traits of the species. The behavioral traits may be more conservative than has been assumed previously. Survival during the drought summer is probably enabled by the storage of enough dry herbs and grasses in the burrows of the animals, while the territorial behavior of the species is the prerequisite of harvesting enough biomass to persist through the adverse climatic conditions of a potentially coming drought