Solar radiation and functional traits explain the decline of forest primary productivity along a tropical elevation gradient

One of the major challenges in ecology is to understand how ecosystems respond to changes in environmental conditions, and how taxonomic and functional diversity mediate these changes. In this study, we use a trait‐spectra and individual‐based model, to analyse variation in forest primary productivity along a 3.3 km elevation gradient in the Amazon‐Andes. The model accurately predicted the magnitude and trends in forest productivity with elevation, with solar radiation and plant functional traits (leaf dry mass per area, leaf nitrogen and phosphorus concentration, and wood density) collectively accounting for productivity variation. Remarkably, explicit representation of temperature variation with elevation was not required to achieve accurate predictions of forest productivity, as trait variation driven by species turnover appears to capture the effect of temperature. Our semi‐mechanistic model suggests that spatial variation in traits can potentially be used to estimate spatial variation in productivity at the landscape scale.     

藜麦及其资源开发利用

藜麦Chenopodium quinoa Willd.英文名:quinoa,原产于南美洲安第斯山区,是印加土著居民的主要传统食物,至今已有5 000~7 000多年的利用和种植历史。古代印加人将它称之为"粮食之母"。藜麦在20世纪80年代,被美国宇航局用于宇航员的太空食品。联合国粮农组织认为藜麦是唯一的单一植物即可满足人体基本营养需求的食物,正式推荐藜麦为最适宜人类的完美的全营养食品。本文对藜麦的植物形态、生态特性、营养价值以及在我国种植展望作了综合报道。     

Keep collecting: accurate species distribution modelling requires more collections than previously thought

Aim Species distribution models (SDMs) use the locations of collection records to map the distributions of species, making them a powerful tool in conservation biology, ecology and biogeography. However, the accuracy of range predictions may be reduced by temporally autocorrelated biases in the data. We assess the accuracy of SDMs in predicting the ranges of tropical plant species on the basis of different sample sizes while incorporating real‐world collection patterns and biases. Location Tropical South American moist forests. Methods We use dated herbarium records to model the distributions of 65 Amazonian and Andean plant species. For each species, we use the first 25, 50, 100, 125 and 150 records collected and available for each species to analyse changes in spatial aggregation and climatic representativeness through time. We compare the accuracy of SDM range estimates produced using the time‐ordered data subsets to the accuracy of range estimates generated using the same number of collections but randomly subsampled from all available records. Results We find that collections become increasingly aggregated through time but that additional collecting sites are added resulting in progressively better representations of the species’ full climatic niches. The range predictions produced using time‐ordered data subsets are less accurate than predictions from random subsets of equal sample sizes. Range predictions produced using time‐ordered data subsets consistently underestimate the extent of ranges while no such tendency exists for range predictions produced using random data subsets. Main conclusions These results suggest that larger sample sizes are required to accurately map species ranges. Additional attention should be given to increasing the number of records available per species through continued collecting, better distributed collecting, and/or increasing access to existing collections. The fact that SDMs generally under‐predict the extent of species ranges means that extinction risks of species because of future habitat loss may be lower than previously estimated.     

Deeply conserved susceptibility in a multi‐host,multi‐parasite system

Variation in susceptibility is ubiquitous in multi‐host, multi‐parasite assemblages, and can have profound implications for ecology and evolution in these systems. The extent to which susceptibility to parasites is phylogenetically conserved among hosts can be revealed by analysing diverse regional communities. We screened for haemosporidian parasites in 3983 birds representing 40 families and 523 species, spanning ~ 4500 m elevation in the tropical Andes. To quantify the influence of host phylogeny on infection status, we applied Bayesian phylogenetic multilevel models that included a suite of environmental, spatial, temporal, life history and ecological predictors. We found evidence of deeply conserved susceptibility across the avian tree; host phylogeny explained substantial variation in infection status, and results were robust to phylogenetic uncertainty. Our study suggests that susceptibility is governed, in part, by conserved, latent aspects of anti‐parasite defence. This demonstrates the importance of deep phylogeny for understanding present‐day ecological interactions.     

Distributional change and conservation on the Andean flank: a palaeoecological perspective

Aim To review the insights that palaeoecology can offer on the threat posed to Andean communities by global climate change. Location The geographical focus is the eastern flank of the tropical Andes, with particular reference to Peru. Method The article presents a synthetic review of the problem. Results Species‐rich communities of the eastern Andean flank are threatened both by development and climate change. If, as predicted, the cloudbase and frost line lifts 600 m elevation this century, there will be a substantial loss of cloud forest habitat. Palaeoecology provides insights on the location and nature of past ecotones, the continuity of niche availability, and estimates for rates and modes of migration. With further warming and drying of lower montane regions, upslope migration of species will be individualistic: a new equilibrium with the altered climate is unlikely to be attained. The zone of agriculture will move upslope faster than the migrating trees and so landscape conversion will negate the ability of some species to respond to the new conditions. Conservation of the lower reaches of modern cloud forest is advocated as a means to limit this foreseeable extinction event. Main Conclusions Climate change will induce changes in plant and animal communities. Human disturbance will invade climatically marginal agricultural lands at the pace of climate change. Rapid migratory response such as that witnessed at the onset of the Holocene may not be evident as climates warm, because Holocene climatic stability has reduced outlying upslope populations that may have served as expansion nuclei. Conservation must aim to maintain plant and animal niches, rather than particular communities of species.     

The extraordinary journey of Peperomia subgenus Tildenia (Piperaceae): insights into diversification and colonization patterns from its cradle in Peru to the Trans‐Mexican Volcanic Belt

Aim Peperomia subgenus Tildenia consists of c. 60 species growing in seasonal habitats of Neotropical mountain areas from Mexico to Argentina. The subgenus can be split geographically, with almost equal diversity in the Northern Hemisphere (centred in Mexico and Guatemala) and in the Southern Hemisphere (centred in Peru and Bolivia). Only a few species are known from a limited number of localities between these two hotspots. As such, Tildenia is an ideal candidate with which to test time, direction and mode of migration of high mountain taxa against the background of the ‘Great American Biotic Interchange’. Location The Andes with focus on the Central Andes, and the Mexican mountain chains, especially the Trans‐Mexican Volcanic Belt. Methods To elucidate the spatio‐temporal origin, subsequent colonization and radiation of Tildenia, we combine Bayesian phylogenetics based on the chloroplast trnK–matK–psbA region, georeferenced distribution data, and fossil calibrated molecular dating approaches using both penalized likelihood and relaxed phylogenetics. Reconstruction of the ancestral distribution area was performed using dispersal–vicariance analysis and dispersal–extinction–cladogenesis. Results Peperomia subgenus Tildenia is subdivided into six Andean clades and one Mexican and Central American clade originating from a north/central Peruvian ancestor. Molecular dating approaches converge on a stem age of c. 38 Ma for Tildenia and a mostly Miocene diversification and colonization. Main conclusions We detect a strong correlation between diversification of Tildenia and orogenetic events in the respective distribution centres. In the Andes, distribution was influenced by the Altiplano–Eastern Cordillera System as well as the Amotape‐Huancabamba Zone, where the latter serves as both migration barrier and migration bridge for different clades. In contrast to most studies of high‐elevation taxa, we provide support for a south–north colonization towards Central America and Mexico, and provide additional, independent evidence for the latest view on the timing of the Great American Biotic Interchange. In Mexico, the Trans‐Mexican Volcanic Belt has played a major role in more recent radiations together with climatic oscillation and the formation of refugia.     

Origin of hummingbird faunas

Ecological studies of hummingbird communities have emphasized the importance of local conditions and contemporary interactions in the development of these varied faunas. A time-calibrated, DNA hybridization-based phylogeny of the principal hummingbird lineages was used to examine historical aspects of hummingbird faunas in the species-rich tropical lowlands and Andes, and the relatively depauperate West Indies and temperate regions of Central and North America. Parsimony reconstructions of ancestral distributions indicate that these faunas are polyphyletic in origin, comprising several to many independent lineages. Based on the timing of geologic and cladogenic events, hummingbird faunas appear to have arisen more often by colonization than by large-scale vicariance, with multiple dispersals across water gaps, elevational gradients, and latitude. The extent to which particular lineages colonized different regions depended, however, on lineage ecology as well as on the habitat and age of the fauna. In general, the oldest extant trochilofauna, which today occupies the tropical lowlands, was the principal source of colonizing taxa. However, all regions except possibly the West Indies contributed taxa now found elsewhere, including in the tropical lowlands. The Andean fauna comprises several lineages with lowland origin (hermits, Mangoes, Brilliants, Coquettes, Emeralds) as well as at least one that arose in temperate regions outside South America (Bees). At least two lineages that colonized the West Indies gave rise to endemic genera (Mangoes to Eulampis, and Emeralds to Orthorhyncus). Even groups that diversified in the highlands (Brilliants and Bees) gave rise to taxa that subsequently reinvaded the tropical lowlands. As the result of these varied histories, hummingbird communities cannot be arranged easily with respect to organizational complexity and coevolution with nectar sources. Although the physically insular faunas in the Andes and West Indies differ markedly in diversity, both were more strongly affected by colonization than the other faunas. A high potential for coevolution between hummingbirds and plants probably facilitated the successful establishment and radiation of the several Andean-associated lineages. However, coexistence between the two most diverse Andean clades may have been favoured initially through different habitat preferences by their extra-Andean ancestors. In the tropical lowlands, by comparison, the basic separation between the forest-dwelling hermits and canopy and edge-dwelling nonhermits appears to have evolved in situ. The low species and morphologic diversity of hummingbirds breeding north of Mexico reflects the predominance there of a single relatively recent lineage. The regional coexistence of numerous unrelated lineages implies that patterns of ancestry, colonization, and extinction contribute to the make-up of contemporary species-rich hummingbird faunas and serves to qualify the view that hummingbird communities are coadapted assemblages that resist change.     

Systematics and biogeography of the Andean genusEriocnemis (Aves: Trochilidae)

Summary With 11 currently recognised species, the genusEriocnemis (Reichenbach, 1849) is one of the most diversified Andean trochilid groups occupying mainly open montane habitats such as the edges of cloud forest or páramos. On the basis of distributional and morphological patterns, this study highlights the geographical variation and biogeography of the taxon. Characteristics common to all these species are the greenish dorsal plumage, the conspicuous and mostly whitish tibial tufts, and a fairly pronounced tail bifurcation. With the help of plumage synapomorphies for a cladistic analysis (PAUP*), several species groups or superspecies can be distinguished: theE. vestitus group (incl.E. vestitus, E. godini, E. nigrivestis), theE. luciani group (incl.E. luciani, E. cupreoventris, E. sapphiropygia), and theE. alinae group (incl.E. alinae, E. mirabilis).E. glaucopoides, E. mosquera, andE. derbyi differ quite widely in morphology and ecological requirements from the other species. Three new subspecies are described,E. vestitus arcosi from southern Ecuador and northern Peru, andE. luciani baptistae from central and southern Ecuador. A previously overlooked specimen ofE. luciani from the Andes of Mérida represents the first species record for Venezuela, about 1100 km northeast of the main population range, and should be recognised taxonomically asE. luciani meridae, subsp. nov., on the basis of its unique plumage morphology and geographical separation. Additionally, the unique type ofE. ventralis (Salvin, 1891) is probably of hybrid origin (E. vestitus × cupreoventris). The genus may have evolved in the northern Andes, subsequently spreading southward and invading the central Andes. Its recent range and phylogenetic patterns indicate vicariance events as the major speciation factor inEriocnemis.In memoriam Dr. Luis F. Baptista (1941–2000)     

Tempo and mode of hummingbird evolution

Lack of adequate historical data has hindered understanding of the evolutionary tempo and mode of many ecologically well-characterized avian radiations. DNA hybridization distances among 28 hummingbirds (Trochilidae) were used to establish a timescale for this family's radiation into more than 330 species. Under a variety of analytical assumptions, genetic distances calibrated with a fossil divergence date corrected for incompleteness in the geologic record indicated that all extant hummingbird lineages began to diverge in the Early Miocene, approximately 40 Myr (million years) after the Paleocene date estimated for the divergence of hummingbirds and swifts. The long period prior to the radiation of living forms provides ample time for divergent evolution to produce the large morphological gap that has tended to obscure the sister-relationship of hummingbirds and swifts. The Miocene radiation of extant hummingbird lineages itself began with the divergence of the hermit and nonhermit subfamilies approximately 17 Ma (million years ago), followed by the rapid divergence of two Andean and one principally Central and North American clade at approximately 12 Ma. Younger subsidiary lineages, including ones found mainly in the Andes or in North America, date to the later Miocene-earlier Pliocene, approximately 6 Ma. The DNA hybridization-based chronology thus indicates a protracted, rather than stricdy rapid, radiation. Evidence from a broader spectrum of organisms supports the general pattern that higher taxonomic structure within many extant continental families evolved in the Miocene, suggesting that a common environmental pacemaker initiated radiation in unrelated groups. Compared to those in the Pleistocene, radiations tracing to the Miocene may have depended less on rapid climate cycling than on creation of new habitats by major geologic and climatic upheavals. For extant hummingbirds, a principal cause for their Miocene diversification probably was the ability of the ecologically generalized subfamily of nonhermits to radiate in montane areas created by the Andean and other orogenies. Similar interactions between new habitats and their exploitation by ecological generalists may explain, at least in part, the contemporaneous radiation of Passeriformes, the most diverse avian order.     

A modern pollen rain study from the central Andes region of South America

Aim To provide a greater understanding of the modern pollen rain for the central Andes region of South America, thus laying the groundwork for future pollen studies and the derivation of pollen‐climate transfer functions and response surfaces. Location Peru, Bolivia and Chile. Methods Standard palynological techniques for surface soil sampling and discriminant analysis. Results Statistical analysis of the 40 surface samples revealed four palynologically distinct assemblages: (1) the Yungas on the eastern slopes of the Andes; (2) the puna grasslands of the Altiplano; (3) the Coastal Deserts to the west of the Andes; and (4) the Southern Bolivian Highlands. Main conclusions The Yungas group is characterized by high percentages of Urticaceae/Moraceae pollen and fern spores along with trace amounts of pollen from common zoophilous lowland taxa such as Piperaceae, Bignoniaceae and Malpighiaceae. The puna assemblage of the Altiplano is characterized by the dominance of grass (Poaceae) in combination with moderate frequencies of Asteraceae pollen, which tend to increase slightly towards the southern (drier) locations of the Altiplano. Lower percentages of grass pollen and the greater prevalence of Asteraceae, Solanaceae, and the Chenopodiaceae/Amaranthaceae families define the coastal deserts to the west of the Andes. Samples taken from the Southern Bolivian Highlands are characterized by the dominance of Solanaceae in the area, in combination with the pollen of other xerophytic taxa.