A Late-Pleistocene pollen sequence from the Jammertal, south-western Germany with particular reference to location and altitude as factors determining Eemian forest composition

Pollen analytical data from a 23-m core taken in the Jammertal subglacial basin, near Biberach an der Riss, has given a continuous sequence from the Rissian late-glacial to the beginning of the Mid-Würmian. The Eemian interglacial is completely preserved and with a high temporal resolution. Two interstadials, Stafflangen I and II, are recognised in the Lower Würmian. These two woodlands were dominant byPinus andPicea and there was a small but significant (up to 12%) component of thermophilous deciduous tree pollen. Stafflangen I and II are correlated with St. Germain I and II as known from Grande Pile. The north-eastern areal boundary of thermophilous deciduous trees lies between Jammertal and Grande Pile. Furthermore, it was possible for the first time to define and describe altitudinal zonation in Eemian vegetation. During the Eemian, the altitudinal boundary of shade-tolerant deciduous trees (Carpinus, Abies andPicea) lay at ca. 625 m in Upper Swabia and the Swiss Alpine foreland, and at ca. 560 m in Upper Bavaria to the east. The sites, which were dominated byCarpinus occur below this limit whereasAbies orPicea show a preference for habitats at higher altitudes.     

再论南京直立人和北京直立人的年代与环境

以更新世全球性气候变化规律为基准,结合深海氧同位素阶段的划分,以及中国冰期与其对比关系等方面的研究进展,对以往学者所提出的一些更新世事件与氧同位素时段的对比关系进行了检验。结果佐证了南京直立人生活于昆仑主冰期,年代约为距今642ka—620ka,可能与MIS16相当的观点。研究同时表明:北京直立人可能生存于前大间冰期(MIS15—13)的初期,推测最早的北京直立人的年代为距今约620ka。     

Contrasting effects of climate and CO2 on Amazonian ecosystems since the last glacial maximum

The nature of Amazonian ecosystem responses to the large-scale environmental changes characterizing glacial–interglacial cycles is poorly understood. We investigated this issue with a series of transient, continuous 21 000-year simulations using a dynamic process-based ecosystem model. Our results indicate that the Amazon Basin has been dominated by evergreen rain forests since the last glacial maximum (LGM), demonstrating the resilience of this ecosystem to glacial–interglacial environmental change. We find that biome shifts in ecotonal areas since the LGM were driven predominantly by climate change, while coincident, increased ecosystem carbon storage throughout the Amazon Basin was driven largely by CO₂. Our findings imply that recent observed biomass increases in contemporary rain forest plots might be part of a long-term trend driven by the anthropogenic rise in CO₂ over recent centuries.     

Soil phosphorus as a control of productivity and openness in temperate interglacial forest ecosystems

Aim Observations of long chronosequences in forest ecosystems show that, after some millennia of build‐up, biomass declines in relation to the slow depletion of soil phosphorus. Plants that dominate during this period of soil impoverishment have specialized strategies for P acquisition, including ectomycorrhiza or root clusters. We use quantitative, pollen‐based reconstructions of regional vegetation in four Quaternary warm stages (Holocene, Eemian, Holsteinian, Harreskovian) to test whether inferred forest cover and productivity changes are consistent with long‐term modification of soil nutrient pools. Location Southern Scandinavia (Denmark, southern Sweden). Methods The REVEALS model was used to estimate regional vegetation abundances of 25 pollen‐type‐equivalent taxa from pollen records of large sedimentary basins in southernmost Scandinavia. Based on the estimated regional vegetation, we then calculated time‐series of Ellenberg indicator values for L (light), R (soil reaction) and N (a productivity proxy). We classified the vegetation records into distinct phases and compared these phases and the samples using hierarchical clustering and ordination. Results All three interglacials developed coniferous or mixed forests. However, pure deciduous forests were never reached during the Holsteinian, while pure coniferous forests never developed in the Holocene. Above‐ground productivity was inferred to be low initially, peaking in the first third of the warm stages and then slowly declining (except during the Holocene). Dominant trees of the post‐peak phases all had ectomycorrhiza as a strategy for P acquisition, indicating that easily accessible P pools had become depleted. Increases in fire regimes may have amplified the inferred final drop in productivity. Mid/late Holocene productivity changes were much influenced by agricultural activities. Main conclusions REVEALS vegetation estimates combined with Ellenberg indicator values suggest a consistent pattern in warm stages of initially rising productivity, followed by a long and slow decline. The P‐acquisition strategies of dominant trees indicate that the decline reflects increasing P depletion of soils.     

Intraspecific genetic variation in selected mosses of Scandinavian interglacial refugia suggests contrasting distribution history patterns

Three pleurocarpous mosses were studied to explore the haplotype diversity patterns in a Scandinavian system of interglacial refugia in which low‐competitive species of calcareous or base‐rich habitats occur. Hypnum bambergeri and H. vaucheri displayed little variation across Scandinavia. For the third species, Drepanocladus turgescens, an analysis of molecular variance showed that two S Scandinavian lowland regional populations were significantly different from each other and differed or almost differed (Gotland vs. Jämtland, according to pair‐wise Φ_PT) from the populations of the Scandinavian mountain range and Svalbard. Haplotype diversity displayed little variation among regional populations, and did not reflect the higher frequency of sexual reproduction in southern than in mountain populations. A coalescent‐based analysis (LAMARC) indicated immigration into the population now found in the lowlands from that represented in the mountains. This is contrary to that found in Rhytidium rugosum in an earlier study and, together with the fact that sporophytes are produced almost exclusively in the lowlands, speaks against this direction of post‐glacial migration. Therefore, if the LAMARC results reflect migration patterns, these most probably reflect events that occurred earlier. Taken together with the results on R. rugosum, this study emphasizes the fact that moss species having similar distribution patterns reached these distributions in partly different ways. © 2014 The Linnean Society of London, Botanical Journal of the Linnean Society, 2014, 176 , 295–310.     

Phylogenetic conservatism and biogeographic affinity influence woody plant species richness–climate relationships in eastern Eurasia

Mechanisms underlying species richness patterns remain a central yet controversial issue in biology. Climate has been regarded as a major determinant of species richness. However, the relative influences of different evolutionary processes, (i.e. niche conservatism, diversification rate and time for speciation) on species richness–climate relationships remain to be tested. Here, using newly compiled distribution maps for 11 422 woody plant species in eastern Eurasia, we estimated species richness patterns for all species and for families with tropical and temperate affinities separately, and explored the phylogenetic signals in species richness patterns of different families and their relationships with contemporary climate and climate change since the Last Glacial Maximum (LGM). We further compared the effects of niche conservatism (represented by contemporary-ancestral climatic niches differences), diversification rate and time for speciation (represented by family age) on variation in the slopes of species richness–climate relationships. We found that winter coldness was the best predictor for species richness patterns of most tropical families while Quaternary climate change was the best predictor for those of most temperate families. Species richness patterns of closely-related families were more similar than those of distantly-related families within eudicots, and significant phylogenetic signals characterized the slopes of species richness–climate relationships across all angiosperm families. Contemporary-ancestral climatic niche differences dominated variation in the relationships between family-level species richness and most climate variables. Our results indicate significant phylogenetic conservatism in family-level species richness patterns and their relationships with contemporary climate within eudicots. These findings shed light on the mechanisms underlying large-scale species richness patterns and suggest that ancestral climatic niche may influence the evolution of species richness–climate relationships in plants through niche conservatism.     

Late Pleistocene small mammals from the Wannenköpfe volcanoes (Neuwied Basin, western Germany) with remarks on the stratigraphic range of Arvicola terrestris

Redeposited loess sediments from a Pleistocene crater filling in the Neuwied Basin (western Germany) yielded a small mammal fauna mainly composed of arvicoline rodents. The occurrence of rare faunal elements such as Sorex minutissimus, Sicista subtilis, and a species of Microtus (Terricola) is remarkable. Based on the evolutionary level of Arvicola terrestris, the biostratigraphic age of the fossiliferous horizon is transitional between late Eemian and early Weichselian. This conclusion is partly supported by the generalized ecological requirements of a few dominant rodent species. The fauna contributes to the knowledge of this time period, which is poorly documented in western Germany. A new character of the m1 is proposed for the discrimination of Sicista betulina and S. subtilis. To avoid further confusion in the specific assignment of transitional Arvicola specimens from the late Middle Pleistocene to early Late Pleistocene, we propose the formal taxonomic boundary between chronospecies A. mosbachensis and A. terrestris to be shifted from SDQ value 100 to SDQ value 120.     

WHEN COLD IS BETTER: CLIMATE-DRIVEN ELEVATION SHIFTS YIELD COMPLEX PATTERNS OF DIVERSIFICATION AND DEMOGRAPHY IN AN ALPINE SPECIALIST (AMERICAN PIKA, OCHOTONA PRINCEPS)

The genetic consequences of climate-driven range fluctuation during the Pleistocene have been well studied for temperate species, but cold-adapted (e.g., alpine, arctic) species that may have responded uniquely to past climatic events have received less attention. In particular, we have no a priori expectation for long-term evolutionary consequences of elevation shifts into and out of sky islands by species adapted to alpine habitats. Here, we examined the influence of elevation shifts on genetic differentiation and historical demography in an alpine specialist, the American pika ( Ochotona princeps ). Pika populations are divided into five genetic lineages that evolved in association with separate mountain systems, rather than lineages that reflect individual sky islands. This suggests a role for glacial-period elevation shifts in promoting gene flow among high-elevation populations and maintaining regional cohesion of genetic lineages. We detected a signature of recent demographic decline in all lineages, consistent with the expectation that Holocene climate warming has driven range retraction in southern lineages, but unexpected for northern populations that presumably represent postglacial expansion. An ecological niche model of past and future pika distributions highlights the influence of climate on species range and indicates that the distribution of genetic diversity may change dramatically with continued climate warming.