关键词： RNA-seq   PLANARIA   TRANSCRIPTOMES  

摘要： Flatworms of the species Schmidtea mediterranea are immortal-adult animals contain a large pool of pluripotent stem cells that continuously differentiate into all adult cell types. Therefore, single-cell transcriptome profiling of adult animals should reveal mature and progenitor cells. By combining perturbation experiments, gene expression analysis, a computational method that predicts future cell states from transcriptional changes, and a lineage reconstruction method, we placed all major cell types onto a single lineage tree that connects all cells to a single stem cell compartment. We characterized gene expression changes during differentiation and discovered cell types important for regeneration. Our results demonstrate the importance of single-cell transcriptome analysis for mapping and reconstructing fundamental processes of developmental and regenerative biology at high resolution.

关键词： competition   fire   rodents   savanna ecosystem   shrews   small mammals   Zambia  

摘要： While niche separation and relationships with environmental conditions of large mammals of the African savanna have been studied intensively, less conspicuous components have not received similar attention. This is the case of Kafue National Park (KNP), Zambia, where mechanisms supporting coexistence among rodent and shrew species remain unclear, much less the influence of fire on their dietary resource use. Here, we use stable carbon and nitrogen isotopes to assess dietary resource use and partitioning among rodents and shrews found in three vegetation formations of KNP. According to the nitrogen isotope signatures, rodents are one to two trophic levels above primary production, save for Mus triton that is above by two to three. Shrews are two trophic levels above primary production. Among shrews, factors allowing coexistence of similar sized species could not be resolved. Rodent species of the same assemblage either differ in body mass by a factor of two (following Hutchinson's rule) or similar sized species occupy different trophic levels or dietary guilds based on their isotopic nitrogen or carbon signatures. At sites with frequent fires, rodents have broader dietary niches than at sites with low fire frequencies. This could either indicate relaxed competition under high fire frequencies as rodent populations do not reach the carrying capacity of the habitat, or it could reflect reduced competition due to lower species numbers under high versus low fire recurrence regimes. The results indicate competition as an important component structuring rodent communities in Zambian savannas, thus suggesting limited resources.

关键词： Below and aboveground interactions   Arbuscular mycorrhizal fungi   Simulated herbivory   Local adaptation   Kenya Long-term Exclosure Experiment (KLEE)  

摘要： The functional relationship between arbuscular mycorrhizal fungi (AMF) and their hosts is variable on small spatial scales. Here, we hypothesized that herbivore exclusion changes the AMF community and alters the ability of AMF to enhance plant tolerance to grazing. We grew the perennial bunchgrass, Themeda triandra Forssk in inoculum from soils collected in the Kenya Long-term Exclosure Experiment where treatments representing different levels of herbivory have been in place since 1995. We assessed AMF diversity in the field, using terminal restriction fragment length polymorphism and compared fungal diversity among treatments. We conducted clipping experiments in the greenhouse and field and assessed regrowth. Plants inoculated with AMF from areas accessed by wild herbivores and cattle had greater biomass than non-inoculated controls, while plants inoculated with AMF from where large herbivores were excluded did not benefit from AMF in terms of biomass production. However, only the inoculation with AMF from areas with wild herbivores and no cattle had a positive effect on regrowth, relative to clipped plants grown without AMF. Similarly, in the field, regrowth of plants after clipping in areas with only native herbivores was higher than other treatments. Functional differences in AMF were evident despite little difference in AMF species richness or community composition. Our findings suggest that differences in large herbivore communities over nearly two decades has resulted in localized, functional changes in AMF communities. Our results add to the accumulating evidence that mycorrhizae are locally adapted and that functional differences can evolve within small geographical areas.

关键词： American chestnut   browse   Castanea dentata   matrix model   plant population and community dynamics   post-dispersal seed predation   pre-dispersal seed predation   transient analysis  

摘要： Both seed predators and herbivores can have profound effects on individual plant growth, reproduction and survival, but their population-level effects are less well understood. While most plants interact with a suite of seed predators and herbivores over their life cycle, few studies incorporate the effects of multiple interacting partners and multiple life stages on plant population growth. We constructed a matrix model using 6years of data from a rare, seed-producing population of American chestnut (Castanea dentata). We combined field demographic data with published experimental results on the effects of pre-dispersal seed predators (weevils) and post-dispersal seed predators (scatter-hoarding vertebrates) and incorporated the effect of vertebrate herbivores estimated from the field data. We explored the impact of these three different animal interactions for short-term (transient) and long-term (asymptotic) tree population growth. In addition, we used the model to explore the conditions under which scatter hoarding would function as a mutualism. Seed predators had greater effect on both short- and long-term population growth than herbivores. Although weevil infestation can greatly reduce the probability of germination, pre-dispersal seed predators had smaller effects on both short- or long-term population growth than post-dispersal predators. The elasticities of weevil-related parameters were also small. The effect of browsers on both the short- and long-term population growth rate were the smallest of the effects studied. Post-dispersal seed predation affected population growth the most in the interactions studied. The probability of seed removal was among the largest elasticities, similar in magnitude to survival of large ***. Our results indicate that neither weevils nor the intensity of browse damage observed at our study site are likely to hinder tree regeneration or reintroduction, although both reduced population growth. Although researchers a

关键词： Bayesian hierarchical abundance model   Bush encroachment   Camera trapping   Mammals   Savanna systems   Swaziland  

摘要： In grasslands across the world, woody species are replacing grass cover. This bush encroachment can alter available food, cover, and space resources for most mammalian species;however, the specific responses of mammals to bush encroachment in African savannas remain largely unknown. We examined the fine-scale response of mammals across a gradient of bush encroachment using camera traps and a Bayesian hierarchical multi-species abundance model that estimates local relative abundance and species richness while accounting for imperfect detection. Additionally, we simulated species-specific relative abundances and species richness responses to differing bush encroachment management actions. Contrary to our expectations, the relative abundance of only one species showed a negative relationship to shrub cover and another to tree cover. However, the relative abundance of eight out of twenty-one species showed a positive association with grass cover. Mammal species richness increased with grass cover, decreased with shrub cover, and showed no clear pattern with increasing tree cover. Furthermore, our simulations suggest reducing and increasing shrub and grass cover respectively by 50% would increase species richness and local abundances for the mammal community of the area. Our results indicate grass cover exerts a strong influence on habitat use, relative abundances and species richness in bush encroached areas. Our study shows that mammal's positive response to grass cover is more important than potential negative impacts of increasing shrub cover. Consequently, recovering and maintaining adequate grass cover in savannas subject to bush encroachment is an indispensable condition to maximize mammalian diversity and abundances.

关键词： body mass   carbonate   collagen   hair   pleistocene  

摘要： Predator-prey size relationships are among the most important patterns underlying the structure and function of ecological ***,these relationships have already been shown to be important for understanding patterns of macroevolution and differential extinction in the terrestrial vertebrate fossil *** isotope analysis(SIA)is a powerful remote approach to examining animal diets and *** approach is based on the principle that isotope compositions of consumer tissues reflect those of their *** systems where resource isotope compositions are distributed along a body size gradient,SIA could be used to reconstruct predator-prey size *** analyzed stable carbon isotope distributions amongst mammalian herbivores in extant and Plio-Pleistocene African savanna assemblages,and show that the range ofδ^(13)C values among mammalian prey species(herbivores and rodents)increases with body mass(BM),because C_(4) plant feeding(essentially grazing)is more common among larger ***,δ^(13)C values of mammalian carnivores in these systems are related to species’BM,reflecting a higher average C_(4) prey component in the diets of larger-bodied *** pattern likely emerges because only the largest carnivores in these systems have regular access to the C_(4) prey base,whereas smaller carnivores do ***δ^(13)C-BM relationship observed in mammalian carnivores is a potentially powerful approach for reconstructing and parameterizing predator-prey size relationships in contemporary and fossil savanna assemblages,and for interpreting how various behavioral,ecological and environmental factors influence prey size selection.

关键词： Antilles   Dispersal   Eulipotyphla   Nesophontes   Solenodon   Vicariance  

摘要： The mammalian order Eulipotyphla includes four extant families of insectivorans: Solenodontidae (solenodons);Talpidae (moles);Soricidae (shrews);and Erinaceidae (hedgehogs). Of these, Solenodontidae includes only two extant species, which are endemic to the largest islands of the Greater Antilles: Cuba and Hispaniola. Most molecular studies suggest that eulipotyphlan families diverged from each other across several million years, with the basal split between Solenodontidae and other families occurring in the Late Cretaceous. By contrast, Sato et al. (2016) suggest that eulipotyphlan families diverged from each other in a polytomy similar to 58.6 million years ago (Mya). This more recent divergence estimate for Solenodontidae versus other extant eulipotyphlans suggests that solenodons must have arrived in the Greater Antilles via overwater dispersal rather than vicariance. Here, we show that the young timetree estimates for eulipotyphlan families and the polytomy are due to an inverted ingroup-outgroup arrangement of the tree, the result of using Tracer rather than TreeAnnotator to compile interfamilial divergence times, and of not enforcing the monophly of well-established clades such as Laurasiatheria and Eulipotyphla. Finally, Sato et al.'s (2016) timetree includes several zombie lineages where estimated divergence times are much younger than minimum ages that are implied by the fossil record. We reanalyzed Sato et al.' s (2016) original data with enforced monophyly for well-established clades and updated fossil calibrations that eliminate the inference of zombie lineages. Our resulting timetrees, which were compiled with TreeAnnotator rather than Tracer, produce dates that are in good agreement with other recent studies and place the basal split between Solenodontidae and other eulipotyphlans in the Late Cretaceous.

关键词： Bats   birds   conservation   fire   fire management   INLA   mammals   protected areas  

摘要： Fire is a fundamental process in savannas and is widely used for management. Pyrodiversity, variation in local fire characteristics, has been proposed as a driver of biodiversity although empirical evidence is equivocal. Using a new measure of pyrodiversity (Hempson etal.), we undertook the first continent-wide assessment of how pyrodiversity affects biodiversity in protected areas across African savannas. The influence of pyrodiversity on bird and mammal species richness varied with rainfall: strongest support for a positive effect occurred in wet savannas (> 650 mm/year), where species richness increased by 27% for mammals and 40% for birds in the most pyrodiverse regions. Range-restricted birds were most increased by pyrodiversity, suggesting the diversity of fire regimes increases the availability of rare niches. Our findings are significant because they explain the conflicting results found in previous studies of savannas. We argue that managing savanna landscapes to increase pyrodiversity is especially important in wet savannas.

关键词： archaeomalacology   shell midden   human impacts   Pacific Islands archaeology   intertidal ecosystems   archeomalacologie   restes de mollusques   impacts humaine   archeologie du Iles Pacifique   ecosystemes marins intertidaux  

摘要： Small, remote islands, such as low coral atolls, with nutrient-poor, biogenic soils for food crops and vulnerability to extreme weather, have long been considered marginal environments for human habitation. Yet, four decades of archaeological research in the atoll archipelago of the Marshall Islands, eastern Micronesia have demonstrated sustained human occupation there for over two millennia. Here, we present a fine-grained analysis of mollusc remains from four recently excavated archaeological sites (4476 total MNI / 14843 total NISP) combined with mapping and analysis of extant benthic habitats, on Ebon Atoll, Marshall Islands. We examine spatial and temporal variability in mollusc foraging practices from prehistoric village sites and ephemeral camp sites across the windward-leeward exposure gradient. Our analysis demonstrates that foragers targeted a rich assemblage of taxa from different habitats, reflecting a foraging strategy that was adapted to local environmental conditions. Human foraging over 2000 years documented no observable human impacts to molluscs or nearshore intertidal marine ecosystems, challenging previous notions of atolls as marginal, exceptionally difficult settings for human habitation. RESUME Les petites iles reculees, comme les atolls coralliens de faible altitude aux sols biogeniques pauvres en elements nutritifs pour les cultures alimentaires et exposes a des conditions climatiques extremes, ont longtemps ete considerees comme des environnements marginaux pour l'habitat humain. Pourtant, quatre decennies de recherches archeologiques dans l'archipel d'atolls des iles Marshall a l'est de la Micronesie y ont demontre une occupation humaine soutenue pendant plus de deux millenaires. Nous presentons ici une analyse nuancee de restes de mollusques provenant de quatre sites recents de fouilles archeologiques (NMI total 4476 / NISP total 14843) combines a une cartographie et une analyse d'habitats benthiques subsistants sur l'atoll d'Ebon dans le

关键词： 生物群   哺乳动物   新型式   侏罗纪   结构   中耳   滑翔   晚侏罗世  

摘要： 中国科学院古脊椎动物与古人类研究所研究人员与中美数家研究机构,于2017年11月13日在英国《自然》（Nature）期刊联合发表了关于晚侏罗世早期燕辽生物群树贼兽一个新种——阿霍氏树贼兽的研究成果。新种标本产于河北省青龙县干沟镇髫髻山组,时代为晚侏罗世早期（距今约164～159百万年前）,属于燕辽生物群。