Large-scale diversity patterns of vascular epiphytes in Neotropical montane rain forests

Aim Epiphytes contribute up to 30% to the number of vascular plant species in certain global biodiversity hotspots, e.g. the Ecuadorian Andes. However, their large scale diversity patterns are still discussed on the base of results from a few, local epiphyte inventories. Consequently, explanatory models on epiphyte diversity concentrate on the impact of local climate on small scale epiphyte species richness. Our aim was to analyse large scale elevational patterns of epiphyte diversity integrating data from different geographic scales. Location Tropical America, with special emphasis on the Ecuadorian Andes. Methods Our study is based on two data sources. First, we analysed the elevational patterns of epiphyte diversity based on the Catalogue of the Vascular Plants of Ecuador and the Libro Rojo de las Plantas Endèmicas del Ecuador. Secondly, the floristic turnover between the epiphyte inventories of seven montane and four lowland study sites in the Neotropics was analysed. Results The floristic turnover between Neotropical montane epiphyte floras is higher than the one between lowland epiphyte floras. Montane study sites located only a few kilometres apart from each other show considerable differences in their epiphyte species inventories. Irrespectively of their similar dispersal mode, the floristic turnover is much higher for orchids than for Pteridophyta. The Orchidaceae are the species richest group in all of the examined 11 Neotropical epiphyte floras. At the larger scale of the Ecuadorian Flora, c. 50% of the species in the elevational zone with maximum epiphyte diversity (between 1000 and 1500 m) are orchids. Elevational patterns of epiphyte diversity strongly reflect patterns of Orchidaceae. Main conclusions Our results support the observation of a ‘mid‐elevation bulge’ of epiphyte diversity by Gentry and Dodson. It has been frequently shown that the high humidity in mid‐elevations is suitable to maintan a high epiphyte species richness. Our findings show that in addition, large scale epiphyte diversity in montane rain forest is increased by the high floristic turnover at local and regional scale. Based on the importance of Orchidaceae for epiphyte diversity, we discuss that speciation processes corresponding to the highly diverse environment are a driving force for endemism, floristic heterogeneity and consequently for large scale epiphyte species richness in montane forests.     

Assessing the effects of selective logging on birds in Neotropical piedmont and cloud montane forests

In tropical and subtropical forests there is limited information about how to integrate sustainable timber management with the conservation of biodiversity. We examined the effect of selective logging on the bird community to help develop management guidelines to assure the conservation of biodiversity in forests managed for timber production. The study design consisted of control and harvested plots in piedmont and cloud forests of the subtropical montane forests of the Andes in northwestern Argentina. We conducted bird point-count surveys combined with distance estimation. Breeding season bird community composition was more similar between control and logged forest in both the cloud forest and piedmont, than between the two elevations, probably because Neotropical bird communities change dramatically along elevational gradients. Within each elevation zone, community composition changed significantly between harvested and control forests. Both between and within each elevation zone no significant differences in bird density were detected. Similarly, when we analyzed bird density according to diet guilds no general pattern could be extracted. However, we found a significantly greater density of cavity nesters and lower of non-cavity nesters in control plots, probably because most trees that can develop suitable cavities were extracted in logged plots and these plots had a greater structural diversity enabling more nesting resources. Grouping species according to their nesting habitat requirements has rarely been used in the neotropics and other tropical and subtropical forests, but focusing management attention on cavity nesters might address the most sensitive portion of the avian community as well as other species dependent on trees likely to hold cavities.     

Saprotrophic and ectomycorrhizal fungi exhibit contrasting richness patterns along elevational gradients in cool-temperate montane forests

Increasing evidence suggests that elevational gradients of soil fungal richness are highly variable, but few studies have examined how diversity components of each guild contribute to overall fungal diversity. Here, we aimed to disentangle the relationships between total, saprotrophic, and ectomycorrhizal fungal richness, and environmental factors across elevational gradients in cool-temperate montane forests. We observed that total and saprotrophic richness decreased but ectomycorrhizal richness increased with increase in elevation. Elevational range size and nestedness analyses illustrated that saprotrophic and ectomycorrhizal source communities were located at lower and higher elevations, respectively. The observed total and saprotrophic richness were directly influenced by soil properties and indirectly influenced by climate and plant communities. Ectomycorrhizal fungal richness was affected by climate and the dominance of ectomycorrhizal trees. We highlight that two directional source–sink dynamics lead to opposite elevational patterns between saprotrophic and ectomycorrhizal fungal richness, shaping the variation in elevational richness gradients.     

Distributional patterns of the Neotropical humid montane forest avifaunas

The study of biogeographical patterns of the Neotropical humid montane forest avifauna has been prevented due to the lack of phylogenetic hypotheses for most taxa, and to the paucity of detailed studies about the geographical distribution for most of the species. Distributional patterns of this avifauna were explored by integrating predictive distributional models and Parsimony Analysis of Endemicity (PAE). Distributional maps were generated using the Genetic Algorithms for Rule Set Prediction for 442 species; this information was transformed into a data matrix for analysis with PAE. Hierarchical information corresponding to the genus level was incorporated to help resolve the relationships between areas. A strict consensus cladogram showed a clear separation between the Mesoamerican and South American avifaunas. Within the Mesoamerican clade, three geographically structured groups were obtained, whereas the South American clade showed a polytomy of three groups, with two of them, the South Andean Yungas and the Tepuis, located outside the main clade. The third group is a well resolved clade, including areas from eastern Panama and northern Venezuela to central Bolivia. Area relationships suggest a mixed history of dispersal and vicariant events, with the latter being the most important for explaining the biogeographical patterns found.  © 2008 The Linnean Society of London, Biological Journal of the Linnean Society , 2008, 94 , 175–194.     

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.     

History meets ecology: a geographical analysis of ecological restriction in the Neotropical humid montane forests avifaunas

Aim To analyse the ecological patterns of distribution of the avifaunas of the Neotropical humid montane forests, by assessing the degree of habitat restriction among species through the calculation of a numerical index, analysing their relationships with adjacent habitat, and exploring the relative contribution of both higher and lower habitats in shaping the avian assemblages. Location The Neotropical humid montane forests, from Mexico to north‐western Argentina. Methods The degree of species’ restriction to the habitat was calculated through a restriction index based on published endemicity indexes. The index scores range from 0 to 1: a score of 1 indicates a totally endemic species (i.e. fully restricted to the habitat); values tending to 0 indicate a widespread species. Results In Mesoamerica, completely restricted species represent a lower proportion of the total avifauna than in South American humid montane forests; whereas species shared to other habitats showed a higher proportion of the avifauna with affinities to higher altitude forests (e.g. pine and pine‐oak forests). South America, on the other hand, holds assemblages with a high proportion of completely restricted species; species shared to other habitats showed a high proportion of taxa with affinities to lowland forests. Main conclusions The ecological distribution of the HMF's avifauna could be partitioned in three main components: the ecologically restricted avifauna, the high altitude species and, the lower altitude species, which are tightly associated to the floristic composition along the gradient. The history of formation of the HMF flora and the ecological distribution of different avian taxa suggest a common history. Finally, the restriction index allowed a detailed evaluation of the composition of avian assemblages, their degree of restriction to the habitat and of the affinities regarding adjacent habitats, as well as an accurate distinction between species richness and restricted species richness, which should be a fundamental step towards the establishment of conservation priorities.     

Toward ecologically realistic predictions of species distributions: A cross‐time example from tropical montane cloud forests

There is an urgent need for more ecologically realistic models for better predicting the effects of climate change on species’ potential geographic distributions. Here we build ecological niche models using MAXENT and test whether selecting predictor variables based on biological knowledge and selecting ecologically realistic response curves can improve cross‐time distributional predictions. We also evaluate how the method chosen for extrapolation into nonanalog conditions affects the prediction. We do so by estimating the potential distribution of a montane shrew (Mammalia, Soricidae, Cryptotis mexicanus) at present and the Last Glacial Maximum (LGM). Because it is tightly associated with cloud forests (with climatically determined upper and lower limits) whose distributional shifts are well characterized, this species provides clear expectations of plausible vs. implausible results. Response curves for the MAXENT model made using variables selected via biological justification were ecologically more realistic compared with those of the model made using many potential predictors. This strategy also led to much more plausible geographic predictions for upper and lower elevational limits of the species both for the present and during the LGM. By inspecting the modeled response curves, we also determined the most appropriate way to extrapolate into nonanalog environments, a previously overlooked factor in studies involving model transfer. This study provides intuitive context for recommendations that should promote more realistic ecological niche models for transfer across space and time.     

Variation of seasonal litterfall in subtropical montane cloud forests to typhoon severity and environmental factors

Forest litterfall is pivotal for biogeochemical cycles and for assessing the impacts of perturbations on ecosystems. Typhoon occurrence is the primary mechanism for producing litterfall; Taiwan is situated in one of the most frequently disturbed regions. However, no typhoons were recorded in 2018, only occurring three times since 1911. This rare occasion, along with the regular (2017) and extreme typhoon (2016) years, provides an opportunity to investigate the responses of typhoon-prone forest ecosystems to a future climate scenario: Elevated temperatures amplify the intensity but reduce the frequency of typhoons. We compared three years (2016–2018) of summer typhoon season (July–October) mean monthly litterfall (MML) in the subtropical montane cloud forests of northeastern Taiwan, and investigated the relationships between MML/typhoon-induced MML (ΔMML) and 17 biophysical, bioclimatic and topographic attributes. More MML was produced in 2016, caused by strong winds and heavy rainfall. However, there was no statistical difference between 2017 and 2018 since forests may also produce substantial amounts of litterfall in summer without typhoons. The relationship between ΔMML and 17 variables was relatively insensitive to typhoon severity. Variables associated with succession and forest management were crucial for modeling MML in the presence of typhoons, but none of them were pivotal for MML without typhoons. The mean air temperature and elevation (related to forest productivity) were crucial for MML without typhoons; surface curvature may form shelters to prevent extreme typhoon with reduced MML. These outcomes may shed light on future ecosystem dynamics in typhoon-prone forests under a changing climate. Abstract in Mandarin is available with online material.     

Fire effects and ecological recovery pathways of tropical montane cloud forests along a time chronosequence

Tropical montane cloud forests (TMCFs) harbour high levels of biodiversity and large carbon stocks. Their location at high elevations make them especially sensitive to climate change, because a warming climate is enhancing upslope species migration, but human disturbance (especially fire) may in many cases be pushing the treeline downslope. TMCFs are increasingly being affected by fire, and the long‐term effects of fire are still unknown. Here, we present a 28‐year chronosequence to assess the effects of fire and recovery pathways of burned TMCFs, with a detailed analysis of carbon stocks, forest structure and diversity. We assessed rates of change of carbon (C) stock pools, forest structure and tree‐size distribution pathways and tested several hypotheses regarding metabolic scaling theory (MST), C recovery and biodiversity. We found four different C stock recovery pathways depending on the selected C pool and time since last fire, with a recovery of total C stocks but not of aboveground C stocks. In terms of forest structure, there was an increase in the number of small stems in the burned forests up to 5–9 years after fire because of regeneration patterns, but no differences on larger trees between burned and unburned plots in the long term. In support of MST, after fire, forest structure appears to approximate steady‐state size distribution in less than 30 years. However, our results also provide new evidence that the species recovery of TMCF after fire is idiosyncratic and follows multiple pathways. While fire increased species richness, it also enhanced species dissimilarity with geographical distance. This is the first study to report a long‐term chronosequence of recovery pathways to fire suggesting faster recovery rates than previously reported, but at the expense of biodiversity and aboveground C stocks.     

Patterns of morphological and ecological similarities of small-eared shrews (Soricidae,Cryptotis) in tropical montane cloud forests from Mesoamerica

It has been proposed that high morphological similarity between closely related species of small-eared shrews resulted from a recent divergence and intermittent population connectivity, presumably due to Pleistocene climatic fluctuations and associated changes in forest habitat distribution. Here we examined the morphological variation of two sister species of small-eared shrews inhabiting cloud forests from Mexico, Cryptotis obscurus and C. mexicanus. We then used ecological niche modelling to provide compelling evidence for current environmental barriers for population connectivity, and for detecting divergent ecological niches between candidate species. Our results indicated that the species boundaries in this clade should be subject to change. High morphological similarity suggested that populations of C. obscurus and C. mexicanus located west of the Isthmus of Tehuantepec, a major geographic barrier for montane species, are conspecific. Niche divergence between these two putative species was not supported indicating niche conservatism across the evolutionary history of these small-eared shrews. In addition, several barriers seem to play a main role for current lineage divergence between populations within this clade. The population located east of the Isthmus, previously referred to C. mexicanus, might prove to represent a new species based on morphological distinction and current geographic isolation. We have highlighted that estimating species’ potential distributions provides insights to evaluating the effect of geographic barriers on lineage divergence and making stronger inferences when delimiting species.     

A new Cheilolejeunea Marchantiopsida: Lejeuneaceae from montane forests in New Zealand

Abstract

Cheilolejeunea celata M.Renner & Glenny sp. nov., a minute species from high elevation (generally >600 m), high rainfall forests on the wetter, western side of New Zealand, is described and illustrated. It is similar to Cheilolejeunea novaezelandiae R.M. Schust. in its dome-shaped papillae on the lobe surface and its autoicous state, but differs in bearing papillae over the entire lobe surface and on the underleaves, in having narrower underleaves that are never imbricate and have a narrow sinus, and in growing primarily in forest, on the stems of other bryophyte species. In its combination of oblique lobes, strongly inflated keel, and bifid underleaves, the species provides further support for the recent merger of Cyrtolejeunea into Cheilolejeunea.     

Liverworts of southwest Ethiopian montane forests: ecological and biogeographical notes

Abstract

Ethiopia has diverse topographic features and climatic conditions with a diverse flora. The liverwort flora of southwest Ethiopia is practically unknown, despite a favourable climate and the occurrence of suitable ecosystems such as montane rainforests. During an ecological study of diversity patterns of bryophytes and vascular plants in relation to land use, we recorded many bryophyte species. In this paper we report the finding of 89 species of liverworts, and give short ecological notes and describe the distribution (locally and in Africa) for each species. Of these, 51 species are newly reported from Ethiopia. It is thus obvious that Ethiopia is considerably richer in liverworts than might be expected from previous checklists.     

Altitudinal distribution patterns of Mexican cloud forests based upon preferential characteristic genera

Mexican cloud forest vegetation has been recorded in temperate humidconditions at rather different elevations ranging from 600 to 3000m. They are characterised by high biodiversity under continuousfoggy situations. Some authors state that many genera are quantitativelyimportant to depict cloud forest conditions. Detailed quantitative studiescomprising most of the localities of Mexican cloud forests to depict altidudinaldistribution ranges on basis of preferential genera have not been previouslyconducted. The aim of this study is (1) to recognise characteristic preferentialgenera of Mexican cloud forest conditions, and (2) to determine quantitativelythe current altitudinal distribution pattern of this vegetation type. From adatabase composed by 995 genera inhabiting in the Mexican cloud forests, sixgenera were chosen preliminary as preferential characteristics. These wereClethra, Magnolia, Meliosma, Styrax, Symplocos, andTernstroemia. These genera include 70 species that occur atover 70% of the current Mexican cloud forest fragments. The mean elevation ofthese genera records were 1853 m (±600 at 95% confidenceinterval). The results showed that Mexican cloud forests occur optimally between1250 and 2450 m. Additionally, Mexican cloud forest is the bestdistributed within some provinces of the Región Mesoamericana deMontaña, chiefly at Serranías Meridionales,Sierra Madre Oriental, and SerraníasTransístmicas. The results are discussed in light of theimportance of these regions as diversification centres.     

Community composition and diversity of Neotropical root‐associated fungi in common and rare trees

Interactions between plants and root‐associated fungi can affect the assembly, diversity, and relative abundances of tropical plant species. Host–symbiont compatibility and some degree of host specificity are prerequisites for these processes to occur, and these prerequisites may vary with host abundance. However, direct assessments of whether specificity of root‐associated fungi varies with host abundance are lacking. Here, in a diverse tropical forest in Los Tuxtlas, Mexico, we couple DNA metabarcoding with a sampling design that controls for host phylogeny, host age, and habitat variation, to characterize fungal communities associated with the roots of three confamilial pairs of host species that exhibit contrasting (high and low) relative abundances. We uncovered a functionally and phylogenetically diverse fungal community composed of 1,038 OTUs (operational taxonomic units with 97% genetic similarity), only 14 of which exhibited host specificity. Host species was a significant predictor of fungal community composition only for the subset of OTUs composed of putatively pathogenic fungi. We found no significant difference in the number of specialists associating with common versus rare trees, but we found that host abundance was negatively correlated with the diversity of root fungal communities. This latter result was significant for symbiotrophs (mostly arbuscular mycorrhizal fungi) and, to a lesser extent, for pathotrophs (mostly plant pathogens). Thus, root fungal communities differ between common and rare trees, which may impact the strength of conspecific negative density dependence. Further studies from other tropical sites and host lineages are warranted, given the role of root‐associated fungi in biodiversity maintenance.     

海南岛热带山地雨林种类组成的局域分布与垂直分布

对海南岛四大山地雨林区常见植物种类的局域及垂直分布进行了研究,结果表明,海南岛热带山地雨林的种类组成,除了在各林区有一定数量相同的种外,各林区之间种类成分也存在着显著的差异,由于各林区生态因子的差异,使得生态幅度不同的物种在垂直方向上的分布也产生明显的差异,生态幅度较小的物种仅局限于某一地段,生态幅度较广,适应性较强的种类则有较广泛的分布。     

Root-associated community composition and co-occurrence patterns of fungi in wild grapevine

Crops’ wild relatives host a wide range of microorganisms, including some beneficial species that are not found or are under-represented in the domesticated crops. Our goal was to study the underexplored composition of root-associated fungal communities in endangered wild grapevines. We found high taxonomic diversity representing multiple trophic guilds that include beneficial symbiotrophs and endophytes. Soil factors explain a relatively small part of their overall variability. In contrast, the majority of the associated fungal taxa shows a close fit to the neutral model for prediction of their distributions. Only beneficial arbuscular mycorrhizal fungi and the pathogenic Ilyonectria depart from the neutral distribution model and form intimate interactions with the plant host. In addition, pathogenic fungi rarely occurred in samples that included ectomycorrhizal fungi, which suggested potentially applicable inter-microorganism interactions. High abundance and diversity of fungal endophytes on the wild grapevine roots highlight the need for their careful consideration in future studies.