Encroachment drives facilitation at alpine shrublines

Ongoing encroachment is driving recent alpine shrubline dynamics globally,but the role of shrub-shrub interactions in shaping shrublines and their relationships with stem density changes remain poorly understood.Here,the size and age of shrubs from 26 Salix shrubline populations along a 900-km latitudinal gradient(30°-38°N)were measured and mapped across the eastern Tibetan Plateau.Point pattern analyses were used to quantify the spatial distribution patterns of juveniles and adults,and to assess spatial associations between them.Mean intensity of univariate and bivariate spatial patterns was related to biotic and abiotic variables.Bivariate mark correlation functions with a quantitative mark(shrub height,basal stem diameter,crown width)were also employed to investigate the spatial relationships between shrub traits of juveniles and adults.Structural equation models were used to explore the relationships among conspecific interactions,patterns,shrub traits and recruitment dynamics under climate change.Most shrublines showed clustered patterns,suggesting the existence of conspecific facilitation.Clustered patterns of juveniles and conspecific interactions(potentially facilitation)tended to intensify with increasing soil moisture stress.Summer warming before 2010 triggered positive effects on population interactions and spatial patterns via increased shrub recruitment.However,summer warming after2010 triggered negative effects on interactions through reduced shrub recruitment.Therefore,shrub recruitment shifts under rapid climate change could impact spatial patterns,alter conspecific interactions and modify the direction and degree of shrublines responses to climate.These changes would have profound implications for the stability of alpine woody ecosystems.

Assessing the Performance of a Dynamical Downscaling Simulation Driven by a Bias-Corrected CMIP6 Dataset for Asian Climate

In this study,we aim to assess dynamical downscaling simulations by utilizing a novel bias-corrected global climate model(GCM)data to drive a regional climate model(RCM)over the Asia-western North Pacific region.Three simulations were conducted with a 25-km grid spacing for the period 1980–2014.The first simulation(WRF_ERA5)was driven by the European Centre for Medium-Range Weather Forecasts Reanalysis 5(ERA5)dataset and served as the validation dataset.The original GCM dataset(MPI-ESM1-2-HR model)was used to drive the second simulation(WRF_GCM),while the third simulation(WRF_GCMbc)was driven by the bias-corrected GCM dataset.The bias-corrected GCM data has an ERA5-based mean and interannual variance and long-term trends derived from the ensemble mean of 18 CMIP6 models.Results demonstrate that the WRF_GCMbc significantly reduced the root-mean-square errors(RMSEs)of the climatological mean of downscaled variables,including temperature,precipitation,snow,wind,relative humidity,and planetary boundary layer height by 50%–90%compared to the WRF_GCM.Similarly,the RMSEs of interannual-tointerdecadal variances of downscaled variables were reduced by 30%–60%.Furthermore,the WRF_GCMbc better captured the annual cycle of the monsoon circulation and intraseasonal and day-to-day variabilities.The leading empirical orthogonal function(EOF)shows a monopole precipitation mode in the WRF_GCM.In contrast,the WRF_GCMbc successfully reproduced the observed tri-pole mode of summer precipitation over eastern China.This improvement could be attributed to a better-simulated location of the western North Pacific subtropical high in the WRF_GCMbc after GCM bias correction.

Trends in Global and Mexico Research in Wildfires: A Bibliometric Perspective

In the last two decades, unprecedented changes have taken place in the frequency and severity of wildfires;in different regions of the world, some fires were even classified as megafires. Although there are studies about the diverse effects of fire, which have made significant theoretical contributions, a comprehensive review of the changes in fire research is required to understand worldwide patterns, particularly in those countries where fire activity is on the rise, such is the case of Mexico. The objective of this study was to analyze the trends in the research on wildfires published in Mexico and worldwide over a 40-year timescale. For this purpose, the Web of Science database, bibliometric tools, and the keywords TI = Forest fire* OR TI = Wildfire* were used to extract as many articles as possible related to fires from 1980 to 2020, without being restricted to those studies whose title included any of the variants of the keywords. There were 8458 publications about fires in the vegetation cover, with a notable increase in the frequency of studies in the previous decade;52% of the studies were concentrated in five countries and 20% of the articles focused on the study of different aspects of the soil. Mexico ranks thirteenth in volume of scientific production and studies in the country have focused mainly on the description of the quantitative relationship between the size of the affected area and the number of occurrences in the landscape, meanwhile, studies on fires and the consequences on the biotic interactions have been little explored.

Different xylogenesis responses to atmospheric water demand contribute to species coexistence in a mixed pine–oak forest

Seasonal patterns of wood formation(xylogenesis)remain understudied in mixed pine-oak forests despite their contribution to tree coexistence through temporal niche complementarity.Xylogenesis was assessed in three pine species(Pinus cembroides,Pinus leiophylla,Pinus engelmannii)and one oak(Quercus grisea)coexisting in a semi-arid Mexican forest.The main xylogenesis phases(production of cambium cells,radial enlargement,cell-wall thickening and maturation)were related to climate data considering 5-15-day temporal windows.In pines,cambium activity maximized from mid-March to April as temperature and evaporation increased,whereas cell radial enlargement peaked from April to May and was constrained by high evaporation and low precipitation.Cell-wall thickening peaked from June to July and in August-September as maximum temperature and vapour pressure deficit(VPD)increased.Maturation of earlywood and latewood tracheids occurred in May-June and June-July,enhanced by high minimum temperatures and VPD in P.engelmannii and P.leiophylla.In oak,cambial onset started in March,constrained by high minimum temperatures,and vessel radial enlargement and radial increment maximized in April as temperatures and evaporation increased,whereas early wood vessels matured from May to June as VPD increased.Overall,15-day wet conditions enhanced cell radial enlargement in P.leiophylla and P.engelmannii,whereas early-summer high 15-day temperature and VPD drove cell-wall thickening in P.cembroides.Warm night conditions and high evaporation rates during spring and summer enhanced growth.An earlier growth peak in oak and a higher responsiveness to spring-summer water demand in pines contributed to their coexistence.

Growth phenology adjusts to seasonal changes in water availability in coexisting evergreen and deciduous mediterranean oaks

Different leaf(evergreen vs.deciduous habit)and xylem(diffuse-vs.ring-porous wood)traits represent contrasting strategies to face seasonal changes in water availability and temperature.However,how contrasting leaf and xylem habits of coexisting tree species affect stem wood formation and tree-ring development remains poorly understood.Here,we investigated the spatio-temporal patterns of wood formation in two deciduous oaks(Quercus faginea and Quercus petraea)and two evergreen oaks(Quercus ilex and Quercus suber)coexisting in seasonally dry Mediterranean forests along an aridity gradient in Spain.We hypothesized that growth responses to drought and intra-and inter-annual growth patterns would differ between functional groups.We simulated intra-and interannual growth using a modified version of the Vaganov-Shashkin(VS)process-based,growth model.The VS model simulations were used to estimate growth changes under a high emission scenario(RCP 8.5)for the current distribution of the study oak species and to forecast their future performance under warm(4.8℃)conditions in the Iberian Peninsula.Our simulations indicate that climate warming would induce a shortening of the ringgrowth season and a reduction of radial growth in evergreen and deciduous Mediterranean oaks,particularly in dry sites from southern and eastern Iberia currently occupied by Q.ilex and Q.faginea.Evergreen oaks may better recover after dry periods than deciduous oaks by resuming growth after the summer drought.Low soil water availability in spring would be more detrimental to growth of deciduous oaks.Process-based growth models should be refined and validated to better forecast changes in tree growth as a function of climate.

Interaction network between frugivorous birds and zoochorous plants in cloud forest riparian strips immersed in anthropic landscapes

Worldwide,tropical montane cloud forest is one of the most important and biodiverse ecosystems;however,it is also one of those most threatened by anthropic activities.These activities lead to a fragmented,deforested landscape with narrow riparian forest strips immersed in an agricultural matrix dominated by pastures.Here,we characterize the interaction network between frugivorous birds and zoochorous plants in riparian strips of cloud forest in deforested landscapes of Central Veracruz,Mexico.To characterize the network of this mutualistic interaction,we estimated network-and species-level metrics using the Bipartite R package.Nestedness,modularity and robustness were used to describe network structure.Centrality measures of degree,closeness,betweenness centrality and their relative contribution to nestedness were used to determine the importance of each bird/plant species to the network’s structure.This interaction network has 24 species of birds and 30 species of plants,with low connectance(0.11),low nestedness(11.53),and intermediate but not significant modularity(0.49).The bird species most important to network stability were Chlorospingus flavopectus,Myadestes occidentalis,and Catharus mexicanus.The most important plants were Conostegia xalapensis,C.arborea,and Rubus ulmifolius.Network robustness varied from 0.36 to 0.86 and its stability is compromised when species of birds or plants with the highest values of centrality are removed,with plant removal more detrimental.Riparian strips of cloud forest crossing deforested areas maintain a relatively rich set of birds that disperse the seeds of many forest plants,thus they are crucial to the preservation of this mutualistic network in anthropic landscapes.Network stability is severely undermined by the loss of any of the few species—whether birds or plants—with high centrality values.The most important plants for this stability are pioneer tree and shrub species that provide food for several bird species,and they are also crucial to cloud forest regeneration.A worrisome finding is that some of the bird species most important to network stability are also among the most sought-after as ornamental birds by illegal collectors in the region.

Invertebrate Iridovirus Modulation of Apoptosis

Programmed cell death (apoptosis) is a key host response to virus infection. Viruses that can modulate host apoptotic responses are likely to gain important opportunities for transmission. Here we review recent studies that demonstrate that particles of Invertebrate iridescent virus 6 (IIV-6) (Iridoviridae, genus Iridovirus), or an IIV-6 virion protein extract, are capable of inducing apoptosis in lepidopteran and coleopteran cells, at concentrations 1000-fold lower than that required to shut-off host macromolecular synthesis. Induction of apoptosis depends on endocytosis of one or more heat-sensitive virion component(s). Studies with a JNK inhibitor (SP600125) indicated that the JNK signaling pathway is significantly involved in apoptosis in IIV-6 infections of Choristoneura fumiferana cells. The genome of IIV-6 codes for an inhibitor of apoptosis iap gene (193R) that encodes a protein of 208 aa with 15% identity and 28% similarity in its amino acid sequence to IAP-3 from Cydia pomonella ganulovirus (CpGV). Transcription of IIV-6 iap did not require prior DNA or protein synthesis, indicating that it is an immediate-early class gene. Transient expression and gene knockdown studies have confirmed the functional nature of the IIV-6 iap gene. We present a tentative model for IIV-6 induction and inhibition of apoptosis in insect cells and discuss the potential applications of these findings in insect pest control.

Natural variability of essential oil and antioxidants in the medicinal plant Turnera diffusa

Objective:To evaluate differences in yield and composition of the essential oil and antioxidant contents in T.diffusa plants from localities in central region of Tamaulipas.Methods:Samples were collected in Tamaulipas,Mexico in the arid zone.Essential oil was obtained through steam distillation and analyzed using GC-MS.Polyphenol contents,antioxidant activities using ABTS and ferric reducing antioxidant power(FRAP) methods also were evaluated.Results:A total of 21 compunds were identified in the essential oils;nevertheless,only Eucalyptol,1,4-Methanocycloocta[d]pyridazine,1,4,4a,5,6,9,10,10a-octahydro-11,11-dimethyl-,(1à,4à,4aà,10aà) y Ethanone,1-(1,3-dimethyl-3-cyclohexen-1-yl) were detected in the three sites.Highest contents were registered in the sample from Padrón y Juárez with phenolic content of 33.85 mg GAE/g of dry material and antioxidant activities with ABTS 72.32% and with FRAP 21.33 mg GAE/g of dry material.Statistical differences were observed in essential oil,phenolics and antioxidants contents between populations.Conclusions:Results suggest that climatic differences and origin influence the phytochemicals in the medicinal plant T.diffusa,and thus,it is worth to consider such effects for industrial and medicinal purposes.

Noisy environments:untangling the role of anthropogenic noise on bird species richness in a Neotropical city

Background:Among urban stimuli,anthropogenic noise has been identified to be one of the behavioral drivers of species that rely on acoustic signals for communication.Studies have shown both species‑specific and assemblage responses to urban noise,ranging from the modulation of their acoustic frequencies and spatiotemporal adjustments to declines in species richness.In this study,we assessed the citywide relationship between two anthropogenic noise variables(noise levels recorded during bird surveys and daily average noise levels)and vegetation cover with bird species richness.Methods:This study was conducted in the city of Xalapa(Mexico)through a 114 citywide point‑count survey.We recorded bird communities at each sampling site.We measured noise levels using a sound level meter while performing point‑counts.Then,we generated a map of average daily noise of the city using an array of 61 autonomous recording units distributed across the city of Xalapa and calculated daily noise levels for the 114 points.We ran a linear model(LM)to assess potential relationships between both point‑count and daily(24 h)noise values and vegetation cover with bird richness.Results:Results from the LM show:(1)a negative relationship between maximum point‑count noise and avian species richness,(2)no relationship between 24 h noise and bird species richness,and(3)a positive relationship between vegetation cover and bird species richness.Conclusions:Results provide evidence that decreases in urban bird species richness do not necessarily imply the permanent absence of species,suggesting that birds can temporarily fly away from or avoid sites when noisy,become cryptic while noisy events are occurring,or be undetected due to our inability to record them in the field during noisy events.

Narcea—an unknown,ancient cultivated rose variety from northern Spain

The present work reports the discovery and the complete characterisation of an ancient cultivated rose variety found growing in a private garden in the southwest of the Principality of Asturias(northern Spain).The variety is here given the name Narcea.The majority of roses currently cultivated belong to the so-called group of‘Modern Roses’,all of which were obtained after 1867 via artificial crosses and improvement programmes.All are destined for ornamental use.Until the 19th century,the great majority of the many ancient cultivated roses in Europe were used in perfumery and cosmetics,or had medicinal uses.Rosa damascena and Rosa centifollia are still grown and used by the French and Bulgarian perfume industries.The Asturian Massif of the Cantabrian Mountain Range provides a natural habitat for some 75%of the wild members of the genus Rosa,but until now there was no evidence that this area was home to ancient cultivated roses.A complete botanical description is here provided for a discovered ancient rose.It is also characterised according to a series of sequence tagged microsatellite sites,and its agronomic features are reported.In addition,a histological description(optical and scanning electronic microscope studies)of the petals is offered,along with an analysis of the volatile compounds present in these organs as determined by solid phase microextraction and gas chromatography-mass spectroscopy.The results reveal the uniqueness of this ancient type of rose and suggest it may be of interest to the perfume industry.

Phylogenetic endemism of the orchids of Megamexico reveals complementary areas for conservation

Orchid diversity provides a unique opportunity to further our understanding of biotic and abiotic factors linked to patterns of richness,endemism,and phylogenetic endemism in many regions.However,orchid diversity is consistently threatened by illegal trade and habitat transformation.Here,we identified areas critical for orchid conservation in the biogeographic province of Megamexico.For this purpose,we evaluated orchid endemism,phylogenetic diversity,and phylogenetic endemism within Megamexico and characterized orchid life forms.Our results indicate that the majority of the regions with the highest estimates of endemism and phylogenetic endemism are in southern Mexico and northern Central America,mostly located on the Pacific side of Megamexico.Among the most important orchid lineages,several belong to epiphytic lineages such as Pleurothallidinae,Laeliinae and Oncidiinae.We also found that species from diverse and distantly related lineages converge in montane forests where suitable substrates for epiphytes abound.Furthermore,the southernmost areas of phylogenetic diversity and endemism of Megamexico are in unprotected areas.Thus,we conclude that the most critical areas for orchid conservation in Megamexico are located in southern Mexico and northern Central America.We recommend that these areas should be given priority by the Mexican system of natural protected areas as complementary conservation areas.

Abundance of White-fronted Parrots and diet of an urban parrot assemblage(Aves:Psittaciformes)in a green Neotropical city

Urban ecosystems are evolutionarily recent novel environments acting as biodiversity filters.Psittacidae birds are considered successful urban adapters mainly due to their generalist feeding and opportunistic behavior,allowing them to occupy environments from cold temperate to dry xeric areas.Therefore,it is important to understand how these species interact in the urban environment.We studied the interannual(2013–2016)abundance of the White-fronted Parrot(Amazona albifrons)in the Neotropical cities of Xalapa and Coatepec,in Central Veracruz,México.Additionally,we studied the feeding ecology during 13 months of 6 parrot species detected in the city of Xalapa.The abundance of the White-fronted Parrot was significantly higher in Xalapa than in Coatepec,and it was homogeneous across years.Non-native plants represented 30–41%of Psittacidae diets in Xalapa,where seeds were the most commonly consumed resource.We recorded the highest Psittacidae species richness and highest diet overlap among species by the end of the dry season(April–May).The White-fronted Parrot had the highest plant richness in its diet,followed by the Monk Parakeet(Myiopsitta monachus)and the Green Parakeet(Psittacara holochlorus);yet,the White-fronted Parrot had a specialized diet dominated by two plant species(Grevillea robusta and Ficus aurea).The diet overlap among the three above-mentioned parrot species was not significantly different to a null model,where the White-fronted Parrot and the Monk Parakeet overlapped during the months of February,April,June,and September.The White-fronted Parrot is an urban adapter that has successfully expanded its geographic range via natural means and by human activities.The invasive Monk Parakeet is currently restricted to one park in Xalapa,and it has remained in that stage for many years(i.e.,pre-expansion phase).Exotic plant species in Xalapa represent∼55%of the woody vegetation,some of which have longer flowering and fruiting periods that may have aided the successful establishment of parrot species in urban environments.

Importance of Quercus spp.for diversity and biomass of vascular epiphytes in a managed pine-oak forest in Southern Mexico

Background:Forestry management modifies the diversity,structure,and functioning of intervened forests.Timber extraction reduces tree density and basal area,leading to changes in the communities of vascular epiphytes.The objective of this study was to evaluate the diversity and biomass of vascular epiphytes in Quercus trees remaining in two pine-oak forest stands that have been subjected to two stages of the Silvicultural Development Method(release cutting,and thinning)in comparison with an unharvested old-secondary forest in southern Mexico.For each treatment,richness of epiphytes present on 60 oak trees was recorded and their dry biomass estimated.We calculated the true diversity(Hill numbers)and beta diversity using the Jaccard coefficient of similarity,and generated rank abundance curves per taxonomic epiphyte group(bromeliads,orchids,ferns and others).For each treatment,the relationships between overall diversity and epiphyte biomass to the host trees basal area were analyzed using log linear models.Results:We recorded a total of 67 species of epiphytes species belonging to 10 families hosted by five species of oaks.The greatest species richness(^(0)D)was recorded in the old-secondary forest.Fewer common(^(1)D)and dominant(^(2)D)species were recorded in the release cutting than in the other treatments.Epiphyte diversity and biomass were both slightly related to host tree basal area.Composition of epiphytes was similar(60%)among treatments,although orchids,bromeliads,and other families were more diverse in the old-secondary forest.Most bromeliad species were shared across all treatments,although orchids presented the most exclusive species in the unharvested forest.The bromeliad Tillandsia seleriana provided the greatest contribution to biomass in all treatments,followed by the orchid Camaridium densum.Generalized linear models indicated that epiphyte diversity was significantly related to treatment,and epiphyte biomass to basal area of host trees.Conclusions:Although forest management affects diversity,composition,and abundance of vascular epiphytes,most of their diversity and biomass can be maintained despite timber harvesting.This requires sparing some mature oaks during logging,as they contribute to conservation,establishment,and development of epiphytic communities,and maintaining untreated areas as a source of propagules for these communities.

Entry into Midgut Epithelial Cells is a Key Step in the Selection of Genotypes in a Nucleopolyhedrovirus

An isolate of the Spodoptera frugiperda multiple nucleopolyhedrovirus comprises a stable proportion of deletion genotypes (e.g., SfNIC-C), that lack pif1 and pif2 rendering them noninfectious per os, and that survive by complementation with a complete genotype (SfNIC-B) in coinfected cells. To determine whether selection for particular ratios of complete and deletion genotypes occurs mainly during the establishment of the primary infection in insect midgut cells or during subsequent systemic infection, we examined genotype frequencies in insects that fed on OBs comprising different co-occluded mixtures of genotypes. Dramatic changes in genotype frequencies were observed between the OB inoculum and budded virus (BV) samples taken from larvae inoculated with OBs comprising 10% SfNIC-B + 90% SfNIC-C indicating that a marked reduction of SfNIC-C genotype had occurred in the insect midgut due to the immediate elimination of all OBs that originated from cells that had been infected only by SfNIC-C. In contrast, immediate changes were not observed in OBs comprising mixtures of 50% SfNIC-B + 50% SfNIC-C or those comprising 10% SfNIC-B + 90% SfNIC-C as most of the OBs in these mixtures originated from cells that had been infected by both genotypes. Subsequent changes in genotypic frequencies during five days of systemic infection were fairly small in magnitude for all genotypic mixtures. We conclude that the prevalence of defective genotypes in the SfNIC population is likely determined by a balance between host selection against OBs produced in cells infected by SfNIC-C alone and within-host selection for fast-replicating deletion genotypes. The strength of intra-host selection is likely modulated by changes in MOI during the infection period.

Impacts of fire severity and cattle grazing on early plant dynamics in old-growth Araucaria-Nothofagus forests

Background: Fire has historically shaped the dynamics of Araucaria araucana-Nothofagus pumilio forests in the Andean region of South America. Nevertheless, human disturbances and stronger drought events have resulted in increased occurrence and severity of wildfires. Regardless of their conservation relevance, the initial response to fire of Araucaria-Nothofagus forests has not been well documented. Through this research we tested the hypothesis that plant composition of Araucaria-Nothofagus forest after fire will initially differ in its recovery depending on fire severity, but over time, plant similarity will increase among areas with different levels of fire severity. The study was carried out in old-growth Araucaria-Nothofagus forests in south-central Chile(38°S) that were burned in 2015. We studied vegetation response to three levels of fire severity(low(LS), moderate(MS) and high(HS) severity), also including an adjacent unburned forest(UN), which were assessed one, two and three years after fire. We also evaluated the impact of cattle on plant recovery after fire. We measured species richness, abundance, plant diversity and origin of all vascular plant species.Results: Species richness and plant abundance responded differently to fire severity. Time-since-fire had a significant effect on plant richness and abundance. Plant composition within LS areas was similar to UN areas, but MS and HS areas were significantly less diverse compared to UN and LS. In absence of other major disturbances, similarity in plant composition tended to increase over time across the different levels of fire severity, becoming more similar to UN. We also found a synergetic effect of cattle and fire on species richness. This interaction promotes the establishment of nonnative species and limits the recovery of native species following fire.Conclusions: Fire severity had a significant impact on the plant community of old-growth Araucaria-Nothofagus forests,especially in areas of high fire severity, where the native tree N. pumilio was completely absent. Nevertheless,plant communities can recover gradually, depending on fire severity, time-since-fire, and the absence of cattle grazing. Management actions should include the exclusion of cattle within fire-affected areas and afforestation with N. pumilio in areas high fire severity due to its unsuccessful recruitment after fire.

Nightlife in the city: drivers of the occurrence and vocal activity of a tropical owl

Background:Cities differ from non-urban environments by the intensity,scale,and extent of anthropogenic pres-sures,which can drive the occurrence,physiology,and behavior of the organisms thriving in these settings.Traits as green cover often predict the occurrence patterns of bird species in urban areas.Yet,anthropogenic noise and artificial light at night(ALAN)could also limit the presence and disrupt the behavior of birds.However,there is still a dearth of knowledge about the influence of urbanization through noise and light pollution on nocturnal bird species ecology.In this study,we assessed the role of green cover,noise,and light pollution on the occurrence and vocal activity of the Mottled Owl(Ciccaba virgata)in the city of Xalapa(Mexico).Methods:We obtained soundscape recordings in 61 independent sites scattered across the city of Xalapa using autonomous recording units.We performed a semi-automated acoustic analysis of the recordings,corroborating all Mottled Owl vocalizations.We calculated two measures of anthropogenic noise at each study site:daily noise(during 24 h)and masking noise(mean noise amplitude at night per site that could mask the owl’s vocalizations).We further performed generalized linear models to relate green cover,ALAN,daily noise,and masking noise in relation to the owl’s occurrence(i.e.,detected,undetected).We also ran linear models to assess relationships among the beginning and ending of vocal activity with ALAN,and with the anthropogenic and masking noise levels at the moment of which vocalizations were emitted.Finally,we explored variations of the vocal activity of the Mottled Owl measured as vocalization rate across time.Results:The presence of Mottled Owls increased with the size of green cover and decreased with increases in both artificial light at night and noise levels.At the temporal scale,green cover was positively related with the ending of the owl’s vocal activity,while daily noise and ALAN levels were not related to the timing and vocal output(i.e.,number of vocalizations).Furthermore,the Mottled Owl showed a marked peak of vocal activity before dawn than after dusk.Although anthropogenic noise levels varied significantly across the assessed time,we did not find an association between high vocal output during time periods with lower noise levels.Conclusions:Spatially,green cover area was positively related with the presence of the Mottled Owl in Xalapa,while high noise and light pollution were related to its absence.At a temporal scale,daily noise and ALAN levels were not related with the timing and vocal output.This suggests that instead of environmental factors,behavioral contexts such as territoriality and mate interactions could drive the vocal activity of the Mottled Owl.Further studies need to incorporate a wider seasonal scale in order to explore the variation of different vocalizations of this species in relation to environmental and biological factors.

Evidence on Night Movements of Macroinvertebrates to Macrophytes in a Pampean Stream

Nocturnal invertebrate abundance peaks in lotic systems are usually associated to drift, however, diel migrations other than drift may be important in slow-flowing systems. Then, macroinvertebrate distribution on macrophytes may change along the day as result of vertical or horizontal migration from sediments or the water column. My objective was to determine whether macroinvertebrate abundance on macrophytes changes along 24 h. Three Ceratophyllum demersum patches were sampled in late spring from the Las Flores stream (Central Argentina) at 11:20 h, 17:10 h, 23:00 h and 5:00 h. Macroinvertebrates were counted and identified, and relative abundances were estimated for each sampling time. The dominant groups of macroinvertebrates sampled were Oligochaeta, Amphipoda and Cladocera. The relative abundance of macroinvertebrates on macrophytes was the highest at 5:00 h, when dissolved oxygen in water reached its minimum. In conclusion, the abundance of macroinvertebrates on macrophytes in Pampean streams may increase at night, probably as result of nocturnal migration driven by changes in predation risk or dissolved oxygen.

The Structure of <i>Pinus hartwegii</i>at the Cofre de Perote, Veracruz, Mexico

A study was conducted on the forest structure of Pinus hartwegii Lindl., located at the Cofre de Perote National Park. The density, diameter, height and wooded coverage were evaluated along an altitudinal gradient from 3500 to 4000 meters in 20 plots of 100 m2. The structure of the population was found to be in the form of an “inverted J”. No statistically significant differences were found for any of the above-mentioned variables evaluated in the altitudinal range. A high density of suppressed individuals was found to occur at 50% of the sites sampled. Given the suppression characteristics of the trees, shelterwood is suggested for a better development of the woodland mass, as well as the introduction of mycorrhizal plants.

On the potential of documenting decadal-scale avifaunal change from before-and-after comparisons of museum and observational data across North America

Studies of biodiversity dynamics have been cast on either long(systematics)or short(ecology)time scales,leaving a gap in coverage for moderate time scales of decades to centuries.Large-scale biodiversity information resources now available offer opportunities to fill this gap for many parts of the world via detailed,quantitative comparisons of assemblage composition,particularly for regions without rich time series datasets.We explore the possibility that such changes in avifaunas across the United States and Canada before and after the first three decades of marked global change(i.e.,prior to 1980 versus after 2010)can be reconstructed and characterized from existing primary biodiversity data.As an illustration of the potential of this methodology for sites even in regions not as well sampled as the United States and Canada,we also explored changes at a single site in Mexico(Chichén-Itzá).We analyzed two large-scale datasets:one summarizing bird records in the United States and Canada before 1980,and one for the same region after 2010.We used probabilistic inventory completeness analyses to identify sites that have avifaunas that have likely been inventoried more or less completely.We prepared detailed comparisons between the two time periods to analyze species showing distributional changes over the time period analyzed.We identified 139 sites on a 0.05°grid that were demonstrably well-inventoried before 1980 in the United States and Canada,of which 108 were also well-inventoried after 2010.Comparing presence/absence patterns between the two time periods for 601 bird species,we found significant spatial autocorrelation in overall avifaunal turnover(species gained and lost),but not in numbers of species lost.We noted potential northward retractions of ranges of several species with high-latitude(boreal)distributions,while other species showed dominant patterns of population loss,either rangewide(e.g.,Tympanuchus cupido)or regionally(e.g.,Thryomanes bewickii).We developed linear models to explore a suite of potential drivers of species loss at relatively fine-grained resolutions(<6km),finding significant effects of precipitation increase,particularly on the eastern border of the United States and Canada.Our exploration of biotic change in Chichén-Itzáincluded 265 species and showed intriguing losses from the local avifauna(e.g.,Patagioenas speciosa),as well as vagrant and recent invasive species in the Yucatán Peninsula.The present work documents both the potential for and the problems involved in an approach integrating primary biodiversity data across time periods.This method potentially allows researchers to assess intermediate-time-scale biodiversity dynamics that can reveal patterns of change in biodiversity-rich regions that lack extensive time-series information.

Tree growth is more limited by drought in rear-edge forests most of the times

Background:Equatorward,rear-edge tree populations are natural monitors to estimate species vulnerability to climate change.According to biogeographical theory,exposition to drought events increases with increasing aridity towards the equator and the growth of southern tree populations will be more vulnerable to drought than in central populations.However,the ecological and biogeographical margins can mismatch due to the impact of ecological factors(topography,soils)or tree-species acclimation that can blur large-scale geographical imprints in trees responses to drought making northern populations more drought limited.Methods:We tested these ideas in six tree species,three angiosperms(Fagus sylvatica,Quercus robur,Quercus petraea)and three gymnosperms(Abies alba,Pinus sylvestris and Pinus uncinata)by comparing rear-edge tree populations subjected to different degrees of aridity.We used dendrochronology to compare the radial-growth patterns of these species in northern,intermediate,and southern tree populations at the continental rear edge.Results and conclusions:We found marked variations in growth variability between species with coherent patterns of stronger drought signals in the tree-ring series of the southern populations of F.sylvatica,P.sylvestris,and A.alba.This was also observed in species from cool-wet sites(P.uncinata and Q.robur),despite their limited responsiveness to drought.However,in the case of Q.petraea the intermediate population showed the strongest relationship to drought.For drought-sensitive species as F.sylvatica and P.sylvestris,southern populations presented more variable growth which was enhanced by cool-wet conditions from late spring to summer.We found a trend of enhanced vulnerability to drought in these two species.The response of tree growth to drought has a marked biogeographical component characterized by increased drought sensitivity in southern populations even within the species distribution rear edge.Nevertheless,the relationship between tree growth and drought varied between species suggesting that biogeographical and ecological limits do not always overlap as in the case of Q.petraea.In widespread species showing enhanced vulnerability to drought,as F.sylvatica and P.sylvestris,increased vulnerability to climate warming in their rear edges is forecasted.Therefore,we encourage the monitoring and conservation of such marginal tree populations.