Orchids in the Open: Understanding Biodiversity Beyond Madagascar's Forests

Managing fire, water, biodiversity and carbon stocks can greatly benefit from early warning of changes in the state of vegetation. While near-real time tools to detect forest change based on satellite remote sensing exist, these ecosystems have relatively stable natural vegetation dynamics. Open (i.e. non-forest) ecosystems like grasslands, savannas and shrublands are more challenging as they show complex natural dynamics due to factors such as fire, postfire recovery, greater contribution of bare soil to observed vegetation indices, as well as high sensitivity to rainfall and strong seasonality. Tools to aid the management of open ecosystems are desperately required as they dominate much of the globe and harbour substantial biodiversity and carbon. We present an innovative approach that overcomes the difficulties posed by open ecosystems by using a spatio-temporal hierarchical Bayesian model that uses data on climate, topography, soils and fire history to generate ecological forecasts of the expected land surface signal under natural conditions. This allows us to monitor and detect abrupt or gradual changes in the state of an ecosystem in near-real time by identifying areas where the observed vegetation signal has deviated from the expected natural variation. We apply our approach to a case study from the hyperdiverse fire-dependent African shrubland, the fynbos of the Cape Floristic Region, a Global Biodiversity Hotspot and UNESCO World Heritage Site that faces a number of threats to vegetation health and ecosystem function. The case study demonstrates that our approach is useful for identifying a range of change agents such as fire, alien plant species invasions, drought, pathogen outbreaks and clearing of vegetation. We describe and provide our full workflow, including an interactive web application. Our approach is highly versatile, allowing us to collect data on the impacts of change agents for research in ecology and earth system science, and to predict aspects of ecosystem structure and function such as biomass, fire return interval and the influence of vegetation on hydrology.

The orchid flora of the Iberian Peninsula is relatively well known, but its biogeographical and diversity patterns have until now remained unanalysed. This work compares the richness of this flora with that of 27 other territories in different continents and at different latitudes, with the aim of establishing whether it is richer or poorer than might be expected. Latitude was found to be an excellent predictor of regional orchid species richness. With 122 taxa, the orchid flora of the Iberian Peninsula is more or less as diverse as that of other Mediterranean areas of similar latitude (e.g. France, Greece or Italy), but more diverse than other European or indeed North African orchid floras. In this study, the Iberian orchid species were assigned to eight monophyletic clades and the global distribution of these are mapped to establish continental affinities between the floras. A recent floristic account on the Iberian orchids was also used to assign the orchid taxa to habitats, and the relationship between the number of endemisms and their habitats was analysed. The patterns of endemism differed in different habitats. Very high levels of endemism were found in habitats peculiar to the Mediterranean Basin, indicating the relict status of its orchid flora.

Orchids of Palau: A field guide by Ann Hillmann Kitalong and Makoto Uesugi. Middletown, DE: The Environment, Inc., 2017. 112 pp. Soft Cover. ISBN 978-982-98016-5-4. £19.00 Micronesian orchid communities are gaining attention from researchers and enthusiasts alike (see, e.g., Raulerson & Rinehart, 1992; GPEPP, 2017; Crain, 2018), however, readily accessible field guides for many of the individual islands or archipelagos are limited in availability. Moreover, 30 to 100 years have passed since much of the literature on Micronesian orchids has been published (e.g., Schlechter, 1921; Tuyama, 1939; Fosberg & Sachet, 1987), during which time numerous changes have taken place in orchid taxonomy that have not been compiled in an easily manageable source. Orchids of Palau: A field guide proficiently fills this void for an important component of orchid diversity in Micronesia. Palau's orchid flora is rich with showy, rare, and endemic species, but given that the islands’ remarkable marine environments often overshadow potential interests in their plant communities, it is encouraging to see that their orchids are being documented and showcased for a broad audience in a convenient field guide. Following the preliminary material [Credits, Acknowledgements, Table of Contents], an Introduction is presented that includes brief sections on Physical Geography, Vegetation of the Islands, History of Palauan Orchids (which includes an interesting list of botanists that have made taxonomic contributions), The Orchid Flora, The Structure of Orchids, The Flower, The Inflorescence, The Seed Capsule, and Vegetative Morphology, most of which include color photos. The main body of the text (Species Descriptions) follows the Introduction and consists of 39 species accounts, organized alphabetically. Each account includes two sections with information on the species’ distribution and habitat (globally and locally) and a species description that includes information on synonymy (in some cases), growth form, stems, leaves, flowers, and phenology. Multiple color photographs of growth form, leaves, flowers, and capsules from co-author Makoto Uesugi and several other contributors also accompany each species account and offer sufficient detail to permit recognition of plants in the field. Although the guide is limited in that it only provides descriptions for less than half of the known orchid species in Palau, it makes up for this in part through a subsequent section of Orchid Plates that includes photos of an additional 12 species. Furthermore, a checklist of 80 recorded species follows the plates section and is a very useful element for consolidating information on the orchids specifically found in Palau. The checklist includes details on phenology (including a monthly calendar) and information on distribution status (Native, Endemic, Introduced, Invasive). The field guide concludes with a Glossary emphasizing orchid morphology and a References section. As with any first edition book, particularly those that cover subjects such as floristics and taxonomy, which are continuously in flux and subject to updates, occasional limitations and errors have inevitably found their way into the publication. In a few instances, photos appear to be captioned incorrectly (e.g., Taeneophyllum palawense, p. 13). Another limitation is that some of the more cryptic species are not included in the Species Descriptions section or in the Plates Section, making it difficult to compare and differentiate closely related species in the field based on the information and photos provided, particularly in the absence of a dichotomous key. In some cases, the taxonomic nomenclature needs to be updated as well, although some of the potential changes are currently under debate (e.g., Oberonia spp., Moerenhoutia spp.). The caption for the checklist also has some missing information for species status symbology (status G), which is omitted. Lastly, it should be noted that the phenology dataset is incomplete, something the authors recognize, and thus it only documents when a species has been observed in bloom by the authors, but not necessarily the true seasonality of the species. Nevertheless, the authors acknowledge that the guide is a work in progress and assert that they are gathering new photographs and added information on seasonality for updated volumes in the future. Despite minor issues with the first edition, I strongly recommend this field guide for any biology department or natural history institute with interests in the flora of Micronesia or southeast Asia. I believe that this book is a valuable resource for botanists focusing on the orchids or flora of Micronesia and a convenient field guide for ecotourists and natural history guides in the Republic of Palau.

Background: La Chinantla, a topographically and geomorphologically complex region, and probably the most humid in the country, hosts a diverse but largely unknown biota, particularly at higher elevations.
 Questions: How many plant species are present in La Chinantla? How are these species distributed along the elevational gradient encompassed in the region?
 Studied species: Lycopodiophyta, Pteridophyta, Gimnospermopsida, Magnoliidae, Eudicots,
 Monocots.
 Study sites and years of study: We studied the flora of the La Chinantla hyper-humid region, Northern Oaxaca Range, southern Mexico, from 1993 to 2017.
 Methods: We collected 2,654 specimens in 73 main localities distributed across an elevational range from 250 to 3,020 m (but concentrated above 800 m). Numerous experts in plant taxonomy examined the specimens and provided or confirmed identifications.
 Results: The checklist of the vascular plants includes 1,021 species, 471 genera and 162 families of vascular plants. The specimens/species ratio (2.6) reflected a satisfactory collecting effort. The most diverse families were Asteraceae, Rubiaceae, and Orchidaceae, whereas the most speciose genera were Peperomia , Miconia and Piper . Most listed species are herbs (47.3 % of the total) and trees (35.2 %), whereas the terrestrial (85.4 %) and epiphytic (15.9 %) growth habits were the most frequent ones (some species presented more than one growth form or growth habit category).
 Conclusions:Based on the magnitude of the current checklist, we estimate that the actual number of species in this region must be around 1,650. The recorded richness of vascular plant species of La Chinantla confirms the large diversity and uniqueness of its flora and calls for efficient conservations efforts to ensure its maintenance in the future.

Glandular trichomes are well known to participate in plant chemical and physical defenses against herbivores, especially herbivorous insects. However, little is known about large-scale geographical patterns in glandular trichome occurrence. Herbivory pressure is thought to be higher at low elevations because of warmer and more stable climates. We therefore predicted a higher proportion of species with glandular trichomes at low elevations than at higher elevations. We compiled glandular trichome data (presence/absence) for 6,262 angiosperm species from the Hengduan Mountains (a global biodiversity hotspot in southwest China). We tested the elevational gradient (800–5,000 m a.s.l.) in the occurrence of plant species with glandular trichomes, and its correlations with biotic (occurrence of herbivorous insects) and abiotic factors, potentially shaping the elevational gradient in the occurrence of glandular trichomes. We found a significantly positive relationship between elevation and the occurrence of glandular trichomes, with the proportion of species having glandular trichomes increasing from 11.89% at 800 m a.s.l. to 17.92% at above 4,700 m. This cross-species relationship remained significant after accounting for phylogenetic relationships between species. Herbivorous insect richness peaked at mid-elevations and its association with the incidence of glandular trichomes was weak. Mean annual temperature was the most important factor associated negatively with glandular trichomes. Our results do not support the hypothesis that plant defenses decrease with increasing elevation. In contrast, a higher proportion of plant species with glandular trichome toward higher elevations is observed. Our results also highlight the importance of considering the simultaneous influences of biotic and abiotic factors in testing geographical variation in multifunctional plant defenses.

Background: It was hypothesised that bryophyte and vascular plant richness of vegetation should exhibit different patterns along gradients of elevation, vegetation productivity and sheep grazing pressure. Aims: The species richness of bryophytes and vascular plant was studied in relation to biomass, elevation and sheep preference on the oceanic northern Atlantic island of St Kilda, Scotland. Methods: Plant communities and biomass were sampled from productive lowlands to summit grasslands associated with decreasing sheep preference. The relationships between bryophyte and vascular plant diversity, elevation and sheep were examined using generalised linear models and smooth trend-surface analyses. Results: Bryophyte and vascular plant richness showed contrasting trends in relation to elevation, sheep preference and biomass. Bryophyte richness peaked at mid to high elevations, was negatively related to levels of sheep preference and standing litter, and showed a curvilinear relation to biomass. Vascular plant species richness had a negative relationship with elevation, negative or unimodal association with sheep preference, and negative relationship with biomass. Conclusions: Bryophyte and vascular plant richness patterns in relation to elevation, vegetation productivity and sheep grazing are not adequate surrogates for each other, and suggest that general species richness models could benefit from organism-specific adjustments.

Xinjiang in China is distinguished by its distinctive regional landscape and high ecological sensitivity. Trollius wildflowers represent a unique and iconic element of the mountain flower landscape in Xinjiang. However, their populations are predominantly distributed in mountainous areas, making them susceptible to climate change. Despite this, the impacts of climate change on the distribution of suitable habitats and ecological niche differentiation for Trollius wildflowers have rarely been quantified. Consequently, simulations were conducted using the R-optimized MaxEnt model to predict the suitable habitat distribution of Trollius wildflowers. This was based on the occurrence data and environmental variables for the four species of Trollius (T. altaicus, T. asiaticus, T. dschungaricus, and T. lilacinus) that exist in the study area. The simulation was conducted over a period of time, beginning with the past glacial period and extending to the present, and then to the future (2050s, 2070s, and 2090s) under multiple scenarios (SSP1-2.6, SSP3-7.0, SSP5-8.5). The simulation of suitable habitats enabled the measurement of the ecological niche breadth and differentiation. The results demonstrate that the model predictions are precisely accurate, with AUC values exceeding 0.9. Annual mean temperature (Bio1), isothermality (Bio3), and precipitation in the warmest quarter (Bio18) are the dominant climate variables, in addition to vegetation, elevation, and soil factors. The proportion of suitable habitats for Trollius wildflowers varies considerably over time, from 0.14% to 70.97%. The majority of habitat loss or gain occurs at the edges of mountains, while stable habitats are concentrated in the core of the mountains. The gravity center of suitable habitats also shifts with spatial transfer, with the shifts mainly occurring in a northeasterly-southwesterly direction. The SSP1-2.6 scenario results in the sustained maintenance of habitats, whereas the SSP3-7.0 and SSP5-8.5 scenarios present challenges to the conservation of habitats. The threshold of ecological niche breadth for Trollius wildflowers is subject to fluctuations, while the ecological niche differentiation also varies. The study aims to examine the evolution of the habitat and ecological niche of Trollius wildflowers in Xinjiang under climate change. The findings will provide theoretical support for delineating the conservation area, clarify the scope of mountain flower tourism development and protection of mountain flower resources, and promote the sustainable development of ecotourism and effective utilization of territorial space in Xinjiang.

Accurate prediction of carbon exchange in the Central Indian Himalaya, a global biodiversity hotspot with extreme vertical gradients and monsoon variability, remains critical for regional carbon assessments. Despite substantial sequestration potential in Himalayan pine forests, mechanistic drivers of net ecosystem exchange (NEE) are poorly constrained, while alpine grassland carbon dynamics remain enigmatic due to observational scarcity at high elevations. Here, we integrate bidirectional long short-term memory (BiLSTM) networks with SHAP explainability to predict hourly NEE and quantitatively rank environmental controls across contrasting ecosystems. Continuous eddy covariance data from a needleleaf forest (Kosi-Katarmal, 1217 m; April-October 2020-2022) and alpine grassland (Darma Valley, 3240 m; July-October 2022-2023) were analyzed using air temperature, relative humidity, net radiation, soil conditions, vapor pressure deficit, NEE derivatives, and multi-scale lag features (1-24 h). The BiLSTM model achieved exceptional performance (forest: R² = 0.94-0.95, RMSE = 2.18-2.86 μmol m⁻² s⁻¹; grassland: R² = 0.95-0.96, RMSE = 1.09-1.73 μmol m⁻² s⁻¹). Critically, SHAP attribution unveiled fundamentally divergent control mechanisms: forest NEE was governed by rapid temporal dynamics (NEE derivative, SHAP: 0.70) and radiation-temperature coupling (SHAP: 0.02 each), signifying energy-driven photosynthetic control. Conversely, grassland NEE exhibited strong short-term memory (1-h lag, SHAP: 0.35) and atmospheric constraint dominance (temperature, SHAP: 0.06, humidity: 0.03), reflecting stomatal regulation and evaporative demand at high elevation. These findings demonstrate that forest carbon exchange operates as an energy-limited, dynamically responsive system, whereas grasslands function as atmospheric-demand limited systems with pronounced temporal persistence. Our results provide a mechanistic framework for ecosystem-specific carbon flux modeling and demonstrate the efficacy of explainable AI for process understanding in data-sparse mountain regions.

The Mediterranean basin is a global hotspot for biodiversity, and wetlands are particularly recognized for their role in this hotspot. Moroccan wetlands, which are part of the broader Mediterranean system, provide habitats for endemic, threatened, and migratory species. Despite their recognized importance and the protection of several Moroccan wetlands, natural wetlands continue to be converted into agricultural lands and urban areas.They are facing anthropogenic pressures and losses in area and quality. Although these transformations have occurred, wetlands located in or near urban areas still harbor remarkable avian biodiversity. In this study, we compared the ornithological composition of urban Mediterranean wetlands, Oued Martil and Oued El Maleh (Tetouan, Northern Morocco), with the Ramsar site Merja Zerga, a classified and a protected wetland. The results show that the urban wetlands and the Ramsar site have in common 66% of families and 43% of species, including several species with significant conservation statuses. In the same way, waterbird species richness was comparable across unprotected and protected coastal wetlands. Likewise, urban wetlands of Oued Martil and Oued El Maleh, as well as the Ramsar site, support the same remarkable, heritage and IUCN- listed species. On the other hand, avian species richness was lower in urban wetlands of the Oued Martil and Oued El Maleh compared to the Ramsar site. In particular, fewer passerine were recorded, and the number of wader species was approximately two times lower in urban wetlands. These results suggest that urban wetlands can support rich and diverse bird populations and need to be protected and integrated into conservation efforts. However, they may also reflect signs of habitat degradation or reduced availability of key resources for bird species. More studies on phenology and long-term monitoring are essential to better understand the ecological significance of urban wetlands in Morocco and across the Mediterranean region.

Tropical mountain ecosystems cover a broad variety of climatic and vegetation zones and are global hotspots of biodiversity. These ecosystems are severely threatened by climate and land-use change, which also strongly affect soil properties. Mt. Kilimanjaro, with its large elevation gradient and relatively homogeneous geology of volcanic rocks and ashes, provides a unique opportunity to study and interpret soil organic matter (SOM) responses to climatic changes.Our objectives were to identify key SOM compounds in six elevation zones (covering ecosystems from tropical dry-lowland, through montane forest, up to alpine heathlands) that are affected by the climatic changes along a 3400 m transect, and to relate these SOM changes to ecosystem specific characteristics. The SOM composition in four topsoils (0–10 cm) samples per ecosystem was characterized by analytical double-shot pyrolysis-gas chromatography–mass spectrometry (Py-GC/MS). Evolving-gas analysis-mass spectrometry (EGA-MS) was used to quantitatively compare the thermal desorption (first shot: <280 °C) and pyrolysis step (second shot: 280–600 °C).The percentage of thermally desorbed compounds increased 10 fold from lowland (<900 m) to mountain forest soils (>2000 m), followed by a 40% decrease in alpine ecosystems (>4000 m). Alkanes/-enes/-ols contributed between 4% and 30% to the identified SOM composition, with a maximum at mid elevation (2120 m). Fatty acids and fatty acid esters contributed with <3% to SOM composition and decreased to a minimum of <1% at Podocarpus forest soils (2900 m), followed by a re-increase at higher elevation. The percentage of lignin-derived compounds followed a similar pattern but also responded to reduced woody inputs above the tree line.Two main factors that seem to affect SOM quality and composition at Mt. Kilimanjaro were: 1) the rate and composition of organic matter inputs that in turn are controlled by climatic characteristics and the vegetation type and 2) the decomposition rate and efficiency, mainly controlled by soil pH, temperature and water availability. High forest productivity at mid elevations (2200 m) leads to high amounts of volatile compounds and increases stable SOM pools. The overall carbon accumulation in Andosols of Mt. Kilimanjaro is linked to the percentage of bound lipids (mainly alkanes, alkenes and alcohols), while site specific input patterns (e.g. vegetation or wild fires) are strongly reflected by sterols, lignin derived compounds or polycyclic aromatic compounds in SOM.

Protected areas (PAs) are a key strategy for conserving areas of outstanding biodiversity value and promoting sustainable development. Significant efforts have been made toward establishing PAs over the last few decades across the globe. However, an assessment of PAs in mountain regions, including in the biodiversity rich Hindu Kush Himalaya (HKH), is lacking. We assessed the status, trend, and distribution of PAs and the ecological representativeness in the PA network. Our analysis showed the HKH has a total of 575 PAs covering 40.17% of the region, accounting for 8.49% of global PA coverage. The HKH hosts 335 Important Bird and Biodiversity Areas (IBAs), 348 Key Biodiversity Areas (KBAs), 12 Global 200 Ecoregions, and 4 Global Biodiversity Hotspots. However, the study showed limited ecological representation in the current PA system as 67% of ecoregions, 39% of hotspots, 69% of KBAs, and 76% of IBAs are still outside of the PA system. About 47% of the PAs are small (&lt;250 sq. km) with no connectivity to other PAs and the majority are distributed in the lower reaches of the HKH. These findings suggest the need to assess and demarcate potential corridors to improve connectivity between PAs and integrate PAs into wider conservation landscapes at national and regional scale beyond country boundaries through regional cooperation. There is also a need to assess and strengthen PA management effectiveness and governance and consider other effective area‐based conservation measures especially in the higher elevations and with a specific focus on ecological representation.

AimAndean forests are a global biodiversity hotspot. They harbour many species living within narrow climate ranges and a high functional diversity of trees. It remains still unclear how such hotspots respond to climatic changes over time. We investigated whether Andean forests are changing their functional composition over time along an elevational gradient by assessing changes in species composition, abundance and functional traits.LocationAn elevational gradient in Colombia's northern Andes.Time PeriodSpecies composition changes were studied two to four times from 2006 to 2017, and functional composition from 2016 to 2017.Major Taxa StudiedA total of 1104 tropical tree species with in situ traits characterization.MethodsWe used seven morphological leaf traits and wood density values to analyse the functional trait dynamic over 10 years along an elevational gradient. By analysing changes in species composition, abundance and trait representation, we inferred the magnitude and direction of changes in functional composition. Then, we assessed if the functional change was related to climate change and demography.ResultsWith increased minimum temperature and vapour‐pressure deficit, we found a decrease over time in mean values for leaf area and specific leaf area and increases in leaf thickness and leaf dry matter content. Long‐term temperature increases are smaller with increasing elevation, but the magnitude of trait changes is greater than in lowlands.Main ConclusionsThe functional composition is changing towards more conservative strategies over time across the elevation gradient, with the strongest changes observed at the highest elevations. This pattern is explained by the change in species turnover within communities due to higher recruitment rates of species with high leaf dry matter content values and low leaf area values. These shifts may be related to communities' responses to higher evapotranspiration demand and thermal stress, mainly at higher elevations.

The survival chance of epiphytic orchids today not only depends on the natural site conditions required by the orchids but also on anthropogenic changes in site conditions. This study answers two questions: (1) What is the ecological niche of the different epiphytic orchid species? (2) What are the ecological factors that threaten epiphytic orchid’s population under anthropogenic disturbances? Our study area was the Kathmandu valley, Nepal, with its subtropical forest.We established 156 systematically selected sampling points in the Kathmandu area covering different types of ecosystems under human impacts such as densely populated area, agricultural land, mixed agricultural and settled area, old tree patches, and a natural forest in a national park. The ecological niche of the orchid species was analyzed with a principal component analysis (PCA). The correlations between the different site factors were statistically significant. Spearman’s rank correlation matrices showed that the variables land-use intensities with altitude, and height with diameter in breast height (dbh) of host had the highest significant positive correlation coefficient (0.67 and 0.64 respectively). On the other hand, host bark pH and altitude as well as land use had a significantly strong negative correlation coefficient (-0.80 and -0.61, respectively). Different epiphytic orchid species interact differently with the given set of environmental factors: for occurrence of Vanda cristata there is no single environmental factor of special influence, while for Rhynchostylis retusa high bark pH and high light availability are important. First two axis of the PCA explained more than 50% of the total variance. Most orchid species occupy a specific, narrow niche in this ecological space. The main causes of anthropogenic influence of orchid population in the Kathmandu Valley are loss of adequate host trees (species and size) and increasing air pollution, resulting in increasing host bark pH.

book reviews ISSN 1948-6596 A much needed compilation of studies of a Neotropical elevation gradient Ecological Gradient Analyses in a Tropical Landscape: Ecological Bulletins 54. Grizelle Gonzalez, Michael R. Willig & Robert B. Waide (editors), 2013, Wiley-Blackwell. 252 pp. £37.50 (Hardback) ISBN: 9781118659328; http://eu.wiley.com/ Since Humboldt’s studies of mountain regions (Humboldt and Bonpland 1807), altitudinal gra- dients have served as a foundation for many ecological processes documenting biodiversity and species distributions. The Luquillo moun- tains in Puerto Rico are perhaps one of the most studied tropical montane forests, where tree distributions across the gradients have been well documented (Weaver and Murphy 1990). Studies in these mountains have gener- ated foundational knowledge about tropical ecology, such as the transition and classifica- tion of ecosystems or “life zone systems” in a landscape (Holdridge 1947), the importance of cloud cover on tropical montane forests (Te Linde et al. 2001), and the impacts of hurri- canes on forest structure (Scatena and Larsen When studying elevational gradients we generally have two choices. Start description and observations of lesser-known mountains, the species occurring in them, and the hydrol- ogy and geology of sites across the gradients; or, build on previous knowledge of the few mountain ranges that are well studied and de- sign experiments based on findings that date from the 1940s. There are advantages in each approach but there is unique value in studying a well known mountain range: previous knowl- edge enables the range to be used as a natural experiment in which species’ distributions and microclimatic and habitat transitions are known. Thanks to researchers including Leslie Holdridge, Fred Scatena, Ariel Lugo, Grizelle Gonzalez, Tamara Heartsil, Michael Willig, Robert Waide and others who devoted their lives to studying many climatological, ecologi- cal and geological aspects across the Luquillo mountains, we can further develop theories about elevation gradients and ask more com- plex questions about these processes. This book is a beautiful hard cover edition including a well-balanced compilation of 15 stud- ies describing the Luquillo mountains. The book is organized in four sections, preceded by an intro- duction of the current knowledge of the area and ending with an insightful conclusion. The compila- tion serves as a testament to the breadth of ques- tions one can pose in a mountain range that is well studied. It is a must-read for researchers planning to work in the Luquillo mountains, or any tropical mountains, since it will bring them up to speed with what has been studied and will pro- vide many insights to what still needs to be under- stood about tropical mountain ranges. Since the Luquillo mountains have been a center of attention for ecologists since 1947, cur- rent studies included in this book have been able to start looking at the diversity gradients of organ- isms that typically are neglected, like snails (Willig et al., p. 117), those dwelling in under-explored microhabitats such as soil, and epiphytes (Richardson and Richardson, p. 101). This book also describes how elevation affects less known aspects of ecology such as nutrient gradients and soil carbon (Medina et al., p. 157). The book in- cludes a study on changes in ecological function- ing across elevation which reveals that the gradi- ent in biogeochemistry (i.e., the REDOX gradient) does not have a linear relationship with elevation, forest type, or net primary productivity (NPP). In- stead, it is shown to be tied to the physical prop- erties of the soil, such as its bulk density (Whendee et al., p. 195). An important read for biogeographers and macroecologists is the study by Harris and collabo- rators (p. 233) who test the maximum power hy- pothesis. They clarify the balance between photo- synthesis and respiration to define the elevation at which the net power flow of the forest is maxi- mized. This elevation band corresponds to where vegetation complexity is at its highest and there frontiers of biogeography 6.3, 2014 — © 2014 the authors; journal compilation © 2014 The International Biogeography Society

Urban expansion threatens biodiversity worldwide, therefore urban spaces need to be amenable to biodiversity conservation. On trees in urban environments, natural colonisation and successful translocation of epiphytic orchids are necessary to enhance urban biodiversity, and depend on the availability of compatible orchid mycorrhizal fungi (OMF). However, the extent of OMF presence and distribution, as well as niche requirements for the OMF, remain poorly studied. To identify and quantify OMF on urban trees as well as assess their suitability for native epiphytic orchids, we conducted high-throughput sequencing on tree bark and orchid root samples. OMF were detected at 60% of the study sites on 16% of 270 bark samples (from stem, fork, and branch microsites within each tree). OMF presence and richness on bark samples were related to multiple biophysical factors; in general, humus presence and precipitation levels were positively predictive of OMF presence and richness. We found Ceratobasidiaceae- and Serendipitaceae-associated OMF both on bark and within roots. Orchid species also showed differing mycorrhizal specificity. Sites associated with fungal genera Ceratobasidium, Rhizoctonia, and Serendipita were considered suitable habitats for seven orchid species. The results suggest that urban trees support OMF and are therefore suitable for native orchid species; however, OMF availability are largely constrained by biophysical factors. To maximise the likelihood of translocation success and consequent natural establishment, we propose that (micro)sites are screened for compatible OMF prior to any intervention.