Paranepheliinae亚族(菊科,Liabeae族)的系统发育和可能的属间杂交

The nuclear ribosomal ITS region and the chloroplast trnL-trnF (trnLF) intergenic region were sequenced for 45 accessions of Paranephelius and six accessions of Pseudonoseris, the two genera of the subtribe Paranepheliinae (Liabeae, Asteraceae) distributed in the alpine regions of the Andes. This data set was used to estimate relationships between these genera and within each genus to aid in evaluating morphological variation and classification. Our results with both ITS and trnLF markers support the monophyly of subtribe Paranepheliinae, and place Pseudonoseris discolor as the first diverged taxon sister to the clade containing Paranephelius. Pseudonoseris szyszylowiczii exhibited intraspecific divergence supporting intergeneric hybridization between Pseudonoseris and Paranephelius. Within Paranephelius, genetic divergence is low and not adequate to fully resolve phylogenetic relationships at the species level, but two genetically and morphologically recognizable groups were revealed by the ITS data. Several accessions possessing multiple ITS sequences represent putative hybrids between the two groups. These putative hybrids have caused some taxonomic confusion and difficulties in establishing species boundaries in Paranephelius. The divergence time estimates based on ITS sequences indicated that the stem of subtribe Paranepheliinae dates to 13 million years ago, but the diversification of the crown clade of the extant members began in the early Pleistocene or late Pliocene, perhaps associated with the uplift of the Andes and the climatic changes of global cooling.     

Los pumas (Puma concolor) como agentes tafonómicos. Análisis actualístico de un sitio de matanza en los Andes de Mendoza, Argentina

A taphonomic study of the carcass of an adult guanaco (Lama guanicoe) recently killed and consumed by one or more pumas (Puma concolor) in the Laguna del Diamante reserve (Mendoza province, Argentina) is exposed, and the case is discussed in the light of the available taphonomic information on this agent in America. The carcass was dispersed along more than 30 m and basically devoid of soft tissues. Thirty-four percent of the bones presented tooth modifications, removal of bone tissue and edge damage, mostly attributable to pumas. Some of these modifications are considerable, as in the case of the skull. The results of the study suggest that bone modifications are intense as compared to other taphonomic studies on this felid. The implications of this are discussed, and the conclusion is reached that more knowledge is needed on the range of variation in puma taphonomic action and the conditions under which such variation occurs.     

Topographic and spatial controls of palm species distributions in a montane rain forest, southern Ecuador

The northern Andes harbour a flora that is as species-rich or even richer than the 18-times larger lowland Amazon basin. Gaining an understanding of how the high species richness of the Andean region is generated and maintained is therefore of particular interest. Environmental sorting due to elevational gradients in climate has been emphasized as a driver of vegetation distribution and plant community assembly in tropical mountain areas such as the Andes for two centuries, while alternative mechanisms have been little studied. Here, we investigated the importance of topography and spatial location as factors controlling species distributions in a palm community in a montane rain forest landscape in the Andes of southern Ecuador (1900–2150 m above sea level). Eleven species were present: Aiphanes verrucosa, Ceroxylon parvifrons, Chamaedorea pinnatifrons, Dictyocaryum lamarckianum, Euterpe precatoria, Geonoma densa, Geonoma orbignyana, Geonoma paradoxa, Prestoea acuminata and Wettinia aequatorialis. To study their spatial distribution, forty 250 m² (5 × 50 m²) plots were laid out perpendicular to four paths that were categorized into three areas and two topographic units (ridges and gullies). Mantel tests and indicator species analysis showed that both topography and spatial location imposed strong controls on palm species distributions at the study site. Our results suggest that species distributions in the studied montane forest landscape were partly determined by the species’ habitat requirements, but also by unknown spatial effects. Although a number of possible explanations exist for the latter, such as unmeasured environmental variables and historical disturbance events, we believe dispersal limitation is likely to be involved. Furthermore, although the gully- or ridge-association of some species corresponded to their general elevational ranges in southern Ecuador, this was not the case for other species. Based on such considerations, we conclude that elevational climatic gradients are likely to only form part of the explanation for the topographic effects on palm species distributions at the study site. Other factors must also be involved, notably wind-exposure and hydrology, as discussed for lowland palm communities. Our results show that to understand plant community assembly in the tropical montane forests of the Andes it is too simple to focus just on environmental sorting by elevational climatic gradients.     

Contracting montane cloud forests: a case study of the Andean alder (Alnus acuminata) and associated fungi in the Yungas

Alnus acuminata is a keystone tree species in the Yungas forests and host to a wide range of fungal symbionts. While species distribution models (SDMs) are routinely used for plants and animals to study the effects of climate change on montane forest communities, employing SDMs in fungi has been hindered by the lack of data on their geographic distribution. The well‐known host specificity and common biogeographic history of A. acuminata and associated ectomycorrhizal (ECM) fungi provide an exceptional opportunity to model the potential habitat for this symbiotic assemblage and to predict possible climate‐driven changes in the future. We (1) modeled the present and future distributions of suitable habitats for A. acuminata; (2) characterized fungal communities in different altitudinal zones of the Yungas using DNA metabarcoding of soil and root samples; and (3) selected fungi that were significant indicators of Alnus. Fungal communities were strongly structured according to altitudinal forest types and the presence of Alnus. Fungal indicators of Alnus, particularly ECM and root endophytic fungi, were also detected in Alnus roots. Current and future (year 2050) habitat models developed for A. acuminata predict a 25–50 percent decrease in suitable area and an upslope shift of the suitable habitat by ca. 184–380 m, depending on the climate change scenario. Although A. acuminata is considered to be an effective disperser, recent studies suggest that Andean grasslands are remarkably resistant to forest invasion, and future range contraction for A. acuminata may be even more pronounced than predicted by our models.     

Angiosperm flora and biogeography of the páramo region of Colombia,Northern Andes

Páramo is the neotropical high elevation ecosystem in the northern Andes and Central America consisting of multiple dissected open areas above 3000 m a.s.l. Complex evolutionary processes that occurred within these ecosystems gave rise to a unique tropical Andean flora. Previous phytogeographical classifications for Colombian páramos have been based on subjective assessments of species distributions. However, a detailed floristic analysis highlighting affinities between páramo regions in Colombia has not yet been proposed. The aim of this study is to provide an analytical scenario for the patterns of regional plant diversity in a hierarchical framework based on the biogeographical history of the páramos, based on 30 localities of the Colombian páramos. Parsimony analysis of endemicity (PAE) and Jaccard similarity indices were applied to a presence/absence data matrix of páramo angiosperm species. Altitudinal distribution of species was used to determine the percentage of the páramo flora endemic to this ecosystem. Genera are shared among páramos, whereas species composition is highly endemic. 86% of the páramo angiosperm plant species is endemic to this ecosystem. The Colombian Páramo areas can be grouped using PAE into five biogeographical units, based on angiosperm species composition. These are: (1) Páramos de la Cordillera Oriental; (2) Páramos de la Cordillera Central and Macizo Colombiano; (3) Páramos de Antioquia; (4) Páramos del Norte; (5) Páramos de la Cordillera Occidental.     

Grass allometry and estimation of above‐ground biomass in tropical alpine tussock grasslands

The puna/páramo grasslands span across the highest altitudes of the tropical Andes, and their ecosystem dynamics are still poorly understood. In this study we examined the above‐ground biomass and developed species specific and multispecies power‐law allometric equations for four tussock grass species in Peruvian high altitude grasslands, considering maximum height (h_max), elliptical crown area and elliptical basal area. Although these predictors are commonly used among allometric literature, they have not previously been used for estimating puna grassland biomass. Total above‐ground biomass was estimated to be of 6.7 ± 0.2 Mg ha^?1 (3.35 ± 0.1 Mg C ha^?1). All allometric relationships fitted to similar power‐law models, with basal area and crown area as the most influential predictors, although the fit improved when tussock maximum height was included in the model. Multispecies allometries gave better fits than the other species‐specific equations, but the best equation should be used depending on the species composition of the target grassland. These allometric equations provide an useful approach for measuring above‐ground biomass and productivity in high‐altitude Andean grasslands, where destructive sampling can be challenging and difficult because of the remoteness of the area. These equations can be also applicable for establishing above‐ground reference levels before the adoption of carbon compensation mechanisms or grassland management policies, as well as for measuring the impact of land use changes in Andean ecosystems.     

The validity of ecogeographical rules is context‐dependent: testing for Bergmann's and Allen's rules by latitude and elevation in a widespread Andean duck

Consistent responses by various organisms to common environmental pressures represent strong evidence of natural selection driving geographical variation. According to Bergmann's and Allen's rules, animals from colder habitats are larger and have smaller limbs than those from warmer habitats to minimize heat loss. Although evidence supporting both rules in different organisms exists, most studies have considered only elevational or latitudinal temperature gradients. We tested for the effects of temperature associated with both elevation and latitude on body and appendage size of torrent ducks (Merganetta armata), a widespread species in Andean rivers. We found a negative relationship between body size and temperature across latitude consistent with Bergmann's rule, whereas there was a positive relationship between these variables along replicate elevational gradients at different latitudes. Limb‐size variation did not support Allen's rule along latitude, nor along elevation. High‐elevation ducks were smaller and had longer wings than those inhabiting lower elevations within a river. We hypothesize that temperature is likely a major selective pressure acting on morphology across latitudes, although hypoxia or air density may be more important along elevational gradients. We conclude that the effect of temperature on morphology, and hence the likelihood of documenting ecogeographical ‘rules’, depends on the environmental context in which temperature variation is examined. © 2014 The Linnean Society of London, Biological Journal of the Linnean Society, 2014, 111, 850–862.     

Comparative demography of two giant caulescent rosettes (Espeletia timotensis and E. spicata) from the high tropical Andes

Using field data from previous studies we built matrix models for two populations of giant rosettes, Espeletia timotensis Cuatrec. and E. spicata Sch. Bip. Wedd., from the Andes Cordillera in Mérida, Venezuela. We analysed the models and calculated population growth rate (λ), sensitivities, elasticities and the sensitivity of the elasticities to changes in the vital rates. The analysis showed that the two species behave alike in general demographic terms. In both models, population growth rate is positive and sensitivities of λ to changes in vital rates decrease markedly in this order: plant establishment, progression of juvenile–adult, germination and survival. The relative contributions of vital rates to λ (elasticities) are very similar to those of other woody plant species: a higher contribution of survival and a very low contribution of fecundity. Transition from seedling to juvenile is most important and the younger established stages (juveniles and young adults) play a predominant demographic role in both populations. Seed banks and older adults are playing a relatively minor role in the dynamics of both populations. However, they may be important in relation to unpredictable, favourable or detrimental events. Perturbation analysis of elasticities showed that increasing the rate of plant establishment will decrease the relative importance of stasis. We conclude that both species are demographically very close, and similar to other long‐lived woody plant species. However, the two species differ in the role of the seed bank, which seems more important in the demography of E. spicata than in E. timotensis.     

The genomic basis of high-elevation adaptation in wild house mice (Mus musculus domesticus) from South America

Understanding the genetic basis of environmental adaptation in natural populations is a central goal in evolutionary biology. The conditions at high elevation, particularly the low oxygen available in the ambient air, impose a significant and chronic environmental challenge to metabolically active animals with lowland ancestry. To understand the process of adaptation to these novel conditions and to assess the repeatability of evolution over short timescales, we examined the signature of selection from complete exome sequences of house mice (Mus musculus domesticus) sampled across two elevational transects in the Andes of South America. Using phylogenetic analysis, we show that house mice colonized high elevations independently in Ecuador and Bolivia. Overall, we found distinct responses to selection in each transect and largely nonoverlapping sets of candidate genes, consistent with the complex nature of traits that underlie adaptation to low oxygen availability (hypoxia) in other species. Nonetheless, we also identified a small subset of the genome that appears to be under parallel selection at the gene and SNP levels. In particular, three genes (Col22a1, Fgf14, and srGAP1) bore strong signatures of selection in both transects. Finally, we observed several patterns that were common to both transects, including an excess of derived alleles at high elevation, and a number of hypoxia-associated genes exhibiting a threshold effect, with a large allele frequency change only at the highest elevations. This threshold effect suggests that selection pressures may increase disproportionately at high elevations in mammals, consistent with observations of some high-elevation diseases in humans.