Cliff Habitats Research Articles

Spatial distribution of cliff plant species in the Balearic Islands under current and projected climatic scenarios

Cliff ecology has been studied for decades, providing information about its high biodiversity values and their vulnerability to climate change. Also, insular ecosystems present biodiversity hotspots with high endemicity, but they are also severely affected by anthropogenic effects. Together, insular cliff communities combine both biodiversity uniqueness and high vulnerability to global change, but few studies have evaluated these particular ecosystems. Our aim was to provide information on the spatial distribution of insular cliff-specific vegetation assessing which environmental and climatic variables contribute to the definition of cliff habitat conditions. Ecological niche modelling for cliff populations in Balearic Islands has been calculated with presences of 20 plant species and climatic and geographical variables using a Random Forest model. The most important climatic variables for the model generation were mean temperature of the driest quarter and precipitation of the coldest quarter. The map obtained showed that mountain ranges from all islands provide highly suitable conditions for rupicolous species. Both the pessimistic and optimistic models showed that the habitat suitability of cliff vegetation in the mountain ranges would decrease, while they are close to zero in lowlands for the period 2021–2040. This study emphasizes the vulnerability of cliff habitats to climate change due to their limited dispersal capacity and distribution and the strict requirements for habitat suitability. From this work, future studies can focus on single-species analysis to evaluate if any cliff specialist species can be at risk of extinction due to climate change.

Chromosome-level genome assembly of a cliff plant Taihangia rupestris var. ciliata provides insights into its adaptation and demographic history

BackgroundCliffs are recognized as one of the most challenging environments for plants, characterized by harsh conditions such as drought, infertile soil, and steep terrain. However, they surprisingly host ancient and diverse plant communities and play a crucial role in protecting biodiversity. The Taihang Mountains, which act as a natural boundary in eastern China, support a rich variety of plant species, including many unique to cliff habitats. However, it is little known how cliff plants adapt to harsh habitats and the demographic history in this region.ResultsTo better understand the demographic history and adaptation of cliff plants in this area, we analyzed the chromosome-level genome of a representative cliff plant, T. rupestris var. ciliata, which has a genome size of 769.5 Mb, with a scaffold N50 of 104.92 Mb. The rapid expansion of transposable elements may have contributed to the increasing genome and its ability to adapt to unique and challenging cliff habitats. Comparative analysis of the genome evolution between Taihangia and non-cliff plants in Rosaceae revealed a significant expansion of gene families associated with oxidative phosphorylation, which is likely a response to the abiotic stresses faced by cliff plants. This expansion may explain the long-term adaptation of Taihangia to harsh cliff environments. The effective population size of the two varieties has continuously decreased due to climatic fluctuations during the Quaternary period. Furthermore, significant differences in gene expression between the two varieties may explain the varied leaf phenotypes and adaptations to harsh conditions in different natural distributions.ConclusionOur study highlights the extraordinary adaptation of T. rupestris var. ciliata, shedding light on the evolution of cliff plants worldwide.

The conservation impact of botanical drones: Documenting and collecting rare plants from vertical cliffs and other hard‐to‐reach areas

Abstract A high percentage of island floras are at risk of extinction and have been reduced to relic populations, often in remote hard‐to‐reach areas. Uncrewed aircraft systems (UAS aka drones) are now being utilized to assist in the survey and collection of rare plants in inaccessible areas or vertical cliff habitats. Here, we test the application of this technology for conservation of 23 plant taxa in three oceanic island hotspots: Hawaiʻi, Madeira and the Republic of Palau. We collect high‐resolution imagery using a small UAS to document the distribution and abundance of vascular flowering plants. Location information is then used to map and assess plant populations. Depending on the terrain, collections are completed using either traditional rope techniques or newly developed remote drone‐based collection methods. Over the course of 6 years, we have greatly expanded our knowledge of rare and endangered species, while increasing survey efficiency and staff safety. Most importantly, this work has had a large impact on the conservation of critically endangered plants. Although using drones for botanical conservation comes with limits and challenges, we see great potential in the continued employment of these techniques wherever plants are growing on cliffs or in other hard‐to‐reach areas.

A pilot study on home range of female Chinese goral (Naemorhedus griseus): exploring GPS tracking data in a cliff landscape

ABSTRACT Home range size estimation is an important basis for developing effective conservation strategies and provides important insights into the study of animal behavior and spatial ecology. We analyze home range variations and the fitfulness of estimation methods on Chinese gorals (Naemorhedus griseus) living at a cliff landscape with GPS tracking data. We report annual, seasonal, and monthly home range sizes of five female Chinese gorals tracked from February 2015 to September 2018. We found variations existed in 95% seasonal home range sizes among estimation methods. We recommend that the α-LoCoH model be used in home range estimations, as this model appeared to more accurately reflect animal locations within the steep cliff habitat in our study area. Furthermore, more animals should be GPS tracked to ensure the validity of any interpretation concerning their home range size in a rugged habitat. This study was the first conducting home-range GPS tracking of Chinese gorals in their northern distribution range. Additionally, our findings provided previously unknown information regarding the home range traits of this endangered species, and they may contribute to the development of effective conservation strategies.

EDNA metabarcoding reveals high soil fungal diversity and variation in community composition among Spanish cliffs.

Environments characterized by physical extremes harbor unique species diversity with particular adaptations. Cliffs are harsh environments for organisms but host a great diversity of specialized plants with many endemics, rare and even endangered species. It is, however, less known which fungal diversity the cliff habitats contain and whether it differs among different cliff locations. We thus sampled soil from three separate cliff locations in the North, Centre, and South of Spain and used eDNA metabarcoding to determine fungal diversity. To better understand whether cliff specialist plants may promote particular fungal communities, we have sampled soil from crevices with cliff specialist plants and no apparent plants as controls. Major lifestyles found in cliff soils were saprotrophs, and major fungal orders were Dothideomycetes, Sordariomycetes, and Eurotiomycetes, while the amount of symbiotrophic fungi was relatively low. We found no significant differences in fungal amplicon sequence variant (ASV) richness among the three sampled locations, but the sites were significantly different in their community composition and their main indicator species. Overall, there were no significant differences in fungal ASV richness or composition between soils from cliff specialist plants and soils without plants, suggesting a unique fungal diversity in cliff soils independent from specialized plants. However, preliminary findings on soils of the specialist cliff plant Sedum dasyphyllum against control soils suggest that the presence of a specialist plant may be a relevant factor affecting the specificity of the fungal community in cliff soils. Our results indicate the existence of particular cliff fungal communities in each location, and that, despite limited and poorly developed soils and harsh conditions, cliffs can harbor a great diversity of fungal species, comparable to other ecosystems of Spain. This study points out that some fungi may be cliff-specific, shaping particular communities that mediate plant adaptations to cliffs' extreme conditions.

A novel method for cliff vegetation estimation based on the unmanned aerial vehicle 3D modeling.

The cliff ecosystem is one of the least human-disturbed ecosystems in nature, and its inaccessible and often extreme habitats are home to many ancient and unique plant species. Because of the harshness of cliff habitats, their high elevation, steepness of slopes, and inaccessibility to humans, surveying cliffs is incredibly challenging. Comprehensive and systematic information on cliff vegetation cover is not unavailable but obtaining such information on these cliffs is fundamentally important and of high priority for environmentalists. Traditional coverage survey methods—such as large-area normalized difference vegetation index (NDVI) statistics and small-area quadratic sampling surveys—are not suitable for cliffs that are close to vertical. This paper presents a semi-automatic systematic investigation and a three-dimensional reconstruction of karst cliffs for vegetation cover evaluation. High-resolution imagery with structure from motion (SFM) was captured by a smart unmanned aerial vehicle (UAV). Using approximately 13,000 records retrieved from high-resolution images of 16 cliffs in the karst region Guilin, China, 16 models of cliffs were reconstructed. The results show that this optimized UAV photogrammetry method greatly improves modeling efficiency and the vegetation cover from the bottom to the top of cliffs is high-low-high, and very few cliffs have high-low cover at the top. This study highlights the unique vegetation cover of karst cliffs, which warrants further research on the use of SFM to retrieve cliff vegetation cover at large and global scales.

Collecting critically endangered cliff plants using a drone-based sampling manipulator

Kauaʻi, an island within the Hawaiʻi archipelago, is home of a unique flora that contains 250 single-island endemic plant species. Threats have led to a significant population decrease where 97% of these plant species are now listed as endangered, critically endangered, or extinct. Vertical cliff habitats on Kauaʻi work as refugia to protect plants from their stressors. However, this habitat makes conservation work particularly difficult, forcing scientists, and botanists to use risky and time-consuming methods such as abseiling to access remote plant populations. Here we present the Mamba, the first aerial system capable of sampling plants on cliffs. This system is operated by two pilots and consists of an actively controlled platform suspended by a long cable under a lifting drone. Eleven otherwise inaccessible samples from five critically endangered species were collected during the first field trials on Kauaʻi Island. The samples are currently surviving in nurseries, demonstrating that the Mamba can be used to complete the conservation life cycle for organisms located in difficult areas, from location to collection, then cultivation and outplanting.

Testing Drones as a Tool for Surveying Lizards

A lack of effective methods for sampling lizards in terrain that is inaccessible to human observers limits our knowledge of their ecology and conservation needs. Drones are increasingly being used in wildlife monitoring, but their potential use for surveying lizards has not been evaluated. We investigated: (1) the detectability of model lizards using a drone relative to a human observer, and (2) the response of four lizard species to an approaching drone in three habitat types. Model lizards placed in potential basking positions within a defined search area were detected by both the drone operator and human observer, but the probability of detection was lower with the drone. Jewelled geckos (Naultinus gemmeus) in shrubland and grand skinks (Oligosoma grande) in rocky habitats showed surprisingly little reaction to the approaching drone, enabling close approaches (means of 59 cm and 107 cm, respectively) and accurate species identification with photos taken by the drone camera. For highly patterned jewelled geckos, identification was also possible to individual level. However, the drone was unsuccessful at detecting two alpine skink species in a near-vertical cliff habitat. Collectively, our results suggest that drones have potential as a tool for detecting small-bodied lizards in habitats inaccessible to human observers.

Detectability of common ravens (Corvus corax) in the eastern USA: Rapid assessment of a recolonizing species

AbstractCommon ravens (Corvus corax) inhabited much of the eastern United States prior to European colonization but were nearly extirpated by the mid‐1900s. Although remnant raven populations have since begun recolonizing portions of their historic range in the eastern United States, the extent of recovery remains largely unknown because of the species' elusive behavior. To aid development of targeted monitoring programs for this rare and cryptic species, we investigated factors that may influence detectability of ravens in natural cliff habitat during the nesting season in the Central Appalachian Mountains. Using a time‐to‐detection framework, we performed surveys at cliff sites with positive raven occupancy and recorded time to first detection (TFD) and confirmed cliff occupancy (i.e., occupied detection) to estimate detection probability curves as a function of survey time. We further compared multiscale habitat features of occupied and unoccupied cliff sites to characterize regional nesting habitat. Mean TFD at occupied cliffs was 14 ± 2 (SE) min. The TFD and subsequent detection probability increased with warming temperatures, likely as a result of heightened activity at nests as the reproductive season progressed. Shorter distances from observation point to the surveyed cliff resulted in longer TFD, indicating that ravens are likely sensitive to disturbance at nest sites. Analysis of cliff‐nesting habitat data identified raven selection of cliffs with large, exposed faces positioned on predominant west‐facing aspects. Mean detection probability calculated from detectability curves was ≥0.8 after the first 30 min. Using a probability‐based model and empirical detection probabilities, we estimated that raven absence from a cliff site during the nesting season may be inferred with p = 0.99 after three independent 30‐min surveys. Although ravens have been considered elusive and rare in the eastern United States, we find that their detectability at occupied cliff sites during the nesting season is relatively high and that observation of distributional changes may be easier for this species than for other, more cryptic birds.

Reproductive biology of an endangered lithophytic shrub and implications for its conservation

BackgroundPlants in cliff habitats may evolve specific reproductive strategies to cope with harsh environments, and unraveling these reproductive characteristics can improve our understanding of survival strategies and lithophyte evolution. This understanding is especially important for efforts to protect rare and endemic plants. Here, we investigated the reproductive biology of Lonicera oblata, an endangered lithophytic shrub that is scattered in highly fragmented and isolated cliff habitats of the Taihang and Yan mountains in North China.ResultsFlowers of L. oblata are herkogamous and protandrous, characteristics that can prevent autogamy at the single-flower level, and insects are necessary for pollination. The outcrossing index, pollen/ovule ratio, and the results of hand pollination were measured and all revealed a mixed mating system for L. oblata, that combines cross-fertilization and partial self-fertilization. The floral traits of L. oblata of zygomorphic and brightly yellowish corolla, heavy fragrance, and rich nectar, suggest an entomophilous pollination system. Sweat bees were observed as the most effective pollinators but their visiting frequencies were not high. Pollen limitation may limit the reproductive success of L. oblata.ConclusionsWe determined the reproductive characteristics of L. oblata, a critically endangered species endemic to cliffs in North China, providing insight into its endangerment and suggesting conservation strategies. L. oblata has highly pollinator-dependent self-fertilization as part of a mixed mating system. Floral features such as low-flowering synchrony, asynchronous anthers dehiscence, and high duration of stigma receptivity, improve pollination efficiency in the case of low pollinator service. Our work provides reference information to understand the survival strategies and conservation of L. oblata and other lithophytes.

Vegetation Type Preference and Habitat Use of Kashmir Markhor (<i>Capra falconeri cashmiriensis</i>) in Kazinag National Park, Kashmir, India

Habitat preferences of the least studied wild caprid, Kashmir Markhor ( Capra falconeri cashmiriensis ) was assessed in Kazinag National Park Kashmir by field surveys on 10 predetermined trails/transects and 6 vantage points during different seasons from 2017 to 2018. Data was collected directly from the field through direct observations and evidences of faecal pellets and footprints. Markhor was found to prefer elevations between 2200-3400m in different seasons. It prefers lower elevations in cold season and higher elevations in warmer seasons, thus shows altitudinal migration. Cliff habitat is most preferred habitat followed by conifers. Riverine and grassland habitats are least preferred whereas alpine meadows are avoided. During winter Markhor prefers south facing slopes (67.30%), while as all the slopes are used almost equally in other seasons. During fawning, females remain at lower elevations, steeper slopes and close to cliffs. The identification of the crucial and preferred areas of Markhor, by this study, can be utilized as a valuable guiding tool in devising conservation and management strategies for the revival of Markhor in Kashmir.

Assessment of the Potential Risk of Rock-Climbing for Cliff Plant Species and Natural Protected Areas of Spain

In recent years, the popularity of rock-climbing has grown tremendously, setting an increasing pressure on cliff habitats. Climbing may be particularly harmful in the Mediterranean biome due to its appropriate environmental conditions for climbing. A few studies have identified the effect of climbing on plant diversity at a small-scale (namely locally or even just in specific climbing areas). However, no studies exist assessing the potential risk of rock-climbing on a broad-scale (e.g., regional or national). The study aims to identify the priority locations and priority cliff plant species in Spain to focus future study efforts. Spain was selected because it is a plant biodiversity hotspot, with a great diversity of endemic and endangered species, and one of the most popular destinations for climbers. We used a geographic information system-based approach to model the spatial concurrence among Spanish climbing areas (and climbing intensity), natural protected areas (NPAs), and distribution of threatened cliff plants (and their IUCN threat category). We found that 53.5% of climbing areas in Spain are located within a NPA, most of them falling into NPAs of medium protection level. We mapped 151 threatened cliff plants, identifying four medium priority Mediterranean locations and eight priority species in which future research efforts should be focused. High-priority study locations are absent in Spain according to our spatial modeling. For the first time on a national scale, this study identifies areas in which climbing represents a potential threat for cliff habitats and threatened plants. These findings contribute to designing field studies on the effects of rock-climbing on Mediterranean cliffs, laying the groundwork for a sustainable, yet challenging, balance between the protection of these unique habitats and rock-climbing.

The Importance of Inland Cliffs and Quarries for Bats

Although cliffs may play an important role in bat ecology (offering natural roosting sites and thermally favourable foraging habitat), there are surprisingly few systematic investigations of bat activity in cliff habitats compared to other habitats. We carried out systematic recordings of bat calls at inland cliff habitats (comprising natural cliffs and quarries) and compared them to three other habitat types (water bodies, settlements and forests) in order to better understand the importance of cliff habitats for bats. A total of 38,440 call sequences were recorded during this study. Overall bat activity at cliff habitats was comparable to activity at water bodies and settlements but was much higher compared to forests. Median activity in forests was only 6% of that in other habitat types. In total, we recorded a minimum of 19 bat species (16 determined to the species level and three representing indistinguishable species pairs). At cliff habitats, 18 species were recorded, representing at least 75% of the 24 bat species with recent records from Carinthia, Austria, including many threatened species. Two species exhibited a significant preference for cliffs over other habitat types: Eptesicus serotinus and Hypsugo savii, the latter of which is known to be a cliff habitat specialist. Bat assemblages in cliff habitats and settlements tended to be more similar compared to other habitat types, a finding that may contribute to our understanding of the urban ecology of bats. The results of our study emphasise the importance of inland cliff habitats for bats and thus, the preservation of abandoned quarries is a significant conservation measure for bats. Moreover, studies focusing on possible negative impacts of rock climbing on bat activity and roosting behaviour of bats are needed.

Eagle Owl presence and diet at mining sites: implications for restoration and management for cliff‐nesting birds

The possible consequences of top predators for the success of restoration actions for animals is still poorly understood. Our main objective was to analyze whether there could be a risk of creating habitats with an excess of predation by top predators when carrying out actions to improve cliff habitats for cliff‐nesting birds at mining sites. We surveyed 28 mining sites in Spain to obtain information regarding the Eagle Owl's (Bubo bubo) presence and diet, and analyzed its relationship with the density of cliff‐nesting birds and rabbits (Oryctolagus cuniculus, its main prey) at the mining sites. We detected Eagle Owls in 18 mining sites (64%) and collected enough prey remains in 11 mining sites. A total of 732 minimum number of prey were identified. The diet of the Eagle Owl consisted mainly of mammals (83%) and the proportion of birds in the diet was low (13%). There was no relationship between the presence of Eagle Owls and the density of rabbits in the mining sites, but there was a positive relationship with the density of cliff‐nesting birds. We conclude that the Eagle Owl does not seem to exert significant pressure on the cliff‐nesting birds, even on wild pigeons, the most abundant cliff‐nesting birds in its diet. Restoration projects which promote cliff‐nesting birds would not entail a significant risk of generating ecological traps by excess of predation by the Eagle Owl. Furthermore, this species could be favored in restoration plans, as it is a threatened species in some areas in Europe.

Monitoring of Plant Species and Communities on Coastal Cliffs: Is the Use of Unmanned Aerial Vehicles Suitable?

Cliffs are reservoirs of biodiversity; therefore, many plant species and communities of inland and coastal cliffs are protected by Council Directive 92/43/EEC (European Economic Community), and their monitoring is mandatory in European Union countries. Surveying plants on coastal cliff by traditional methods is challenging and alternatives are needed. We tested the use of a small Unmanned Aerial Vehicle (UAV) as an alternative survey tool, gathering aerial images of cliffs at Palinuro Cape (Southern Italy). Four photo-interpreters analysed independently the derived orthomosaic and plotted data needed for the monitoring activity. Data showed to be not affected by photo-interpreters and reliable for the prescribed monitoring in the European Union (EU). Using the GIS analysis tools, we were able to: (a) recognise and map the plant species, (b) derive and measure the area of distribution on the cliff of habitat and species, and (c) count Eokochia saxicola individuals and gather quantitative data on their projected area. Quality of the images represented the main constraint, but incoming technological improvements of sensors and UAVs may overcome this problem. Overall results support the use of UAVs as an affordable and fast survey technique that can rapidly increase the number of studies on cliff habitats and improve ecological knowledge on their plant species and communities.

Reproductive ecology of Seselighafoorianum (Apiaceae) restricted to rocky cliffs in Iran

Endemic and relict species are of particular interest when evaluating the ecological intactness of a given area. In this paper, the reproductive ecology of Seseli ghafoorianum (Apiaceae) is investigated, aiming to contribute to its protection. The species is considered as a Tertiary relict species in Iran. Both dwarf form and cliff habitats are rare in the family, raising the question of how the plant has adapted to this environment. Population structure, plant architecture and flowering sequence, pollinators, pollen quantification, and seed set (bagging experiment) were investigated. Individuals produce about 20 flowering branches with ca. 120 umbels. Flowers and umbels are protandrous. The female stage of the terminal umbels usually overlaps the maleness of the 1st order umbels promoting geitonogamy. The pollen/ovule ratio is about 30,000:1, indicating outcrossing. The degree of andromonoecy (>70%) and pollen vitality (~90%) indicate that pollen availability is not a limiting factor. In contrast, fruit set is low (~7%). It depends on the presence of pollinators (Lasioglossum), which is low, most likely due to the use of pesticides. The population furthermore suffers from the low survival rate of seedlings (0.02%). S. ghafoorianum appears to be an outcrossing species suffering from low pollinator and survival rates. To protect the species, use of pesticides and grazing should be reduced.

Tree growth patterns associated with extreme longevity: Implications for the ecology and conservation of primeval trees in Mediterranean mountains

Abstract This study analyzed with dendrochronology 177 Heldreich’s pines growing on the Pollino Massif in southern Italy for understanding climatic and human impacts on old trees. Most of the large-diameter trees currently living became established in the late Medieval to Renaissance periods under a snowy wet climate and low anthropic influence. Millennium-old (i.e., > 900 years of age) trees in remote sites escaped Medieval human impacts, then a wave of pine stands established in the late 14th and 16th centuries following recurrent human plague epidemics. Stem growth histories showed that both millennium-old and the majority of century-old trees grew along similar trajectories. These old trees have survived long-lasting climatic reversals, clearly a sign of their resilience to extreme events. Cliff habitats played a strategic environmental role for tree conservation during periods of land exploitation; such biodiversity refugia may serve as stepping stones for rewilding mountain landscapes. In recent decades, land abandonment following the collapse of sheep-herding, together with climate warming, have led to a new pulse of tree recruitment. Since 1850, low-frequency variability (50-70-year periods) in tree growth has been in synchrony with the Atlantic Multidecadal Oscillation. Recently observed growth increases counter widespread reports of tree and forest decline in Mediterranean environments, and suggest that extreme longevity does not necessarily reduce stem increment. Discovering, studying, and preserving primeval trees in forest landscapes remains a priority for biodiversity conservation in the Anthropocene. Heldreich’s pine resilience to current global changes bodes well for sustainable development in the Mediterranean mountains they inhabit, and similar studies are needed for threatened habitats and iconic trees of other ecoregions in order to assess their probable survival into the future.

Rock climbing activity and physical habitat attributes impact avian community diversity in cliff environments.

As the sport of outdoor rock climbing rapidly grows, there is increasing pressure to understand how it can affect communities of organisms in cliff habitats. To that end, we surveyed 32 cliff sites in Boulder, Colorado, USA, and assessed the relative roles of human recreation and natural habitat features as drivers of bird diversity and activity. We detected only native avian species during our observations. Whereas avian abundance was not affected by climbing, avian species diversity and community conservation value were higher at low-use climbing formations. Models indicated that climber presence and cliff aspect were important predictors of both avian diversity and avian cliff use within our study area, while long-term climbing use frequency has a smaller, but still negative association with conservation value and cliff use by birds in the area. In contrast, the diversity of species on the cliff itself was not affected by any of our measured factors. To assess additional community dynamics, we surveyed vegetation and arthropods at ten site pairs. Climbing negatively affected lichen communities, but did not significantly affect other vegetation metrics or arthropods. We found no correlations between avian diversity and diversity of either vegetation or arthropods. Avian cliff use rate was positively correlated with arthropod biomass. We conclude that while rock climbing is associated with lower community diversity at cliffs, some common cliff-dwelling birds, arthropods and plants appear to be tolerant of climbing activity. An abiotic factor, cliff aspect strongly affected patterns of both avian diversity and cliff use, suggesting that the negative effects of rock climbing may be mitigated by informed management of cliff habitat that considers multiple site features.

Epiphytic strangler trees colonizing extreme habitats of building envelopes in Hong Kong

Trees growing spontaneously on building envelopes, as wall vegetation, denote unique urban ecology. This study investigates the tree flora, substrate, and colonization-development factors on poorly-maintained buildings in Hong Kong. Field surveys gleaned data on species composition, microhabitat, shoot-root dimensions, and biomass structure. The survey sampled 567 trees. They belonged to ten species, distinguished as strong stranglers, moderate stranglers and non-stranglers. Strong stranglers, such as the native Ficus microcarpa and F. virens, were dominant, with diaspores dispersed mainly by frugivorous birds tapping cultivated and ruderal trees. Most trees had limited crown spread and height, and the larger ones were strong stranglers. The compact tree form, reflecting growth constraints, limited their landscape-scenic contributions. Most surface roots displayed restricted lateral growth contrasted by more vertical extension. Five microhabitats were identified. Two mainly vertical ones accommodated 42.3% of the trees, including wall vertical surface holding the most, and pipe surface. Three mainly horizontal microhabitats, more conducive to seed lodging and tree establishment, held 57.7%, including awning & ledge, roof top & edge taking the second largest share, and window sill & canopy. The stranglers scaled more vertical sites, whereas non-stranglers more horizontal. Root-shoot and root-biomass ratios reflected microhabitat controls. The findings were discussed vis-a-vis pre-adaptation of stranglers to vertical-habitat existence, enabling and restrictive microhabitat traits, plaster degradation as critical pre-condition, leap-frog succession and species paucity, analogy with rocky cliff habitat, and application to building-tree management.

Autonomous self-pollination in the South African orchid Satyrium rupestre Schltr.

Autonomous self-pollination is widespread in orchids, but has not yet been reported for Satyrium, a genus in which floral variation is generally associated with attraction of and specialized pollination by a wide range of animals. Here I add evidence for autonomous self-pollination in the diminutive flowers of S. rupestre from the Cape Floristic Region. In recently opened flowers, pollinia of S. rupestre flowers have moved out of the anther sacs and, accompanied by reconfiguration of the caudicles, moved upwards to contact and rest on the stigma. Movement of the pollinia is associated with a narrowed central region of the rostellum, which results from tissue disintegration in flower buds; a process which does not occur in the animal-pollinated sister species S. ligulatum. Evidence of autonomous self-pollination in S. rupestre was observed both in fresh flowers in situ in two populations and in several herbarium specimens collected across the c. 400 km long species range, consistent with autonomous self-pollination as a species-wide trait. Tetrazolium staining tests indicated that more than 50% of seeds produced following self-pollination are viable. Although small amounts of liquid were detected in the spurs of S. rupestre flowers, scent emission rates and the number of massulae per pollinium are consistent with reduced reliance on animal pollinators. Future studies should focus on the extent to which the species relies on autonomous self-pollination for reproduction, to reveal whether it may serve as a mechanism of reproductive assurance in the pollinator-depauperate forest and cliff habitats of S. rupestre.