Endangered Tree Species Research Articles

Low effective population size and high spatial genetic structure of black poplar populations from the Oder valley in Poland

ContextBlack poplar (Populus nigra L.) is a keystone species of European riparian ecosystems that has been negatively impacted by riverside urbanization for centuries. Consequently, it has become an endangered tree species in many European countries. The establishment of a suitable rescue plan of the remaining black poplar forest stands requires a preliminary knowledge about the distribution of genetic variation among species populations. However, for some parts of the P. nigra distribution in Europe, the genetic resources and demographic history remain poorly recognized.AimsHere, we present the first study on identifying and characterizing the genetic resources of black poplar from the Oder valley in Poland. This study (1) assessed the genetic variability and effective population size of populations and (2) examined whether gene flow is limited by distance or there is a single migrant pool along the studied river system.MethodsA total of 582 poplar trees derived from nine black poplar populations were investigated with nuclear microsatellite markers.Results(1) The allelic richness and heterozygosity level were high and comparable between populations. (2) The genetic structure of the studied poplar stands was not homogenous. (3) The signatures of past bottlenecks were detected.ConclusionOur study (1) provides evidence for genetic substructuring of natural black poplar populations from the studied river catchment, which is not a frequent phenomenon reported for this species in Europe, and (2) indicates which poplar stands may serve as new genetic conservation units (GCUs) of this species in Europe.Key messageThe genetic resources of black poplar in the Oder River valley are still substantial compared to those reported for rivers in Western Europe. On the other hand, clear signals of isolation by distance and genetic erosion reflected in small effective population sizes and high spatial genetic structure of the analyzed populations were detected. Based on these findings, we recommend the in situ and ex situ conservation strategies for conserving and restoring the genetic resources of black poplar populations in this strongly transformed by human river valley ecosystem.

Detection and application of novel SSR markers from transcriptome data for Astronium fraxinifolium Schott, a threatened Brazilian tree species.

Astronium fraxinifolium is an endangered tree species from Brazil. Due to its significance in environmental reforestation, as well as the continued exploitation of its wood, it is necessary to develop management programs that support the conservation of the species. Simple sequence repeats (SSR) or microsatellite markers are widely used in population genetic studies across a range of diverse organisms. In this study, we present the first SSR markers developed for A. fraxinifolium as well as their frequency and distribution based on transcriptome data. From transcriptome data, we identified more than 100 thousand sequences presenting microsatellites, with a predominant distribution of trinucleotide repeats. From the initial screening, we selected 20 microsatellite loci which were validated and evaluated for genetic indices in two natural populations. All loci were polymorphic, ranging from four to 11 alleles per locus. The observed and expected heterozygosities ranged from 0 to 1.0 and from 0.533 to 1.0, respectively, while the genetic differentiation (GST = 0.363) was greater within than between populations. The developed SSR loci from RNA-Seq data provides a foundation for future studies on genetic diversity and population structure, mating system, and gene flow for A. fraxinifolium populations and related species, aiming at conservation and management.

In situ conservation of endangered tree species (Elaeocarpus venustus Bedd.) habitated in Agasthiyamalai Biosphere Reserve, Southern Western Ghats, India.

Elaeocarpus venustus is an endemic as well as endangered tree species habitated in the wet evergreen forests of Southern Western Ghats (SWG), India. Due to insufficient natural regeneration, low seedling tendency, and prevailing anthropogenic disturbances, their distribution has been shrinking in their native environment. Towards conserving this endangered species, we have attempted to propagate E. venustus in its habitat by adopting vegetative propagation techniques of cutting and air layering through growth hormones. Significant growth has been observed by providing 2 mM concentration of indole-3-butyric acid (IBA) for both cutting and air layering. Higher rooting response has been observed through cutting and air layering techniques during monsoon periods. Based on the results of the study, we suggest that the cutting and air layering techniques can be employed as promising strategies towards the in situ conservation and promotion of Elaeocarpus venustus tree species as well as other endangered species in Western Ghats.

Shifts in leaf herbivory stress and defense strategies of endangered tree species after 20–35 years of ex-situ conservation

Ex-situ conservation, the transplanting of individuals outside of their natural range, can dramatically alter biotic interactions among species. Here, we explored the shifts in the herbivory pressure and defense strategies of ex-situ populations of five endangered tree species (Pterostyrax psilophyllus, Davidia involucrata, Dipteronia sinensis, Tapiscia sinensis, and Tetracentron sinense) after 20–35 years since translocation. All species were not native to the ex-situ site and only P. psilophyllus had a closely related native species (Pterostyrax corymbosus). We compared the leaf damage type, herbivory rate, and chemistry (total phenols, tannins, N, and P) of each species, and assessed the relationship between the herbivory rate and leaf chemistry between the ex-situ and wild populations. Excluding P. psilophyllus, all species in the ex-situ populations showed changes in the type of leaf damage and lower overall herbivory rates. Ex-situ populations of P. psilophyllus showed reduced total phenol, N, and P levels, while the other four species showed decreased total phenol and tannin levels, or increased N and P levels. The herbivory rate was positively correlated with the N and P levels in wild populations, and negatively correlated with the total phenol content in ex-situ populations. These differences reflect the reduced herbivory pressure, decreased defense ability, and shift in defense strategy of ex-situ populations. We showed that prolonged exposure to the ex-situ environment led to the maladaptation of these endangered plant species to herbivory pressure in the natural environment, and that these shifts should be considered in ex-situ conservation and reintroduction strategies.

Dynamics of Water and Abscisic Acid During Embryogeny and Embryo Drying in the Recalcitrant Seeds of Vateria indica L.

Vateria indica L. is a critically endangered tree species in South-Western Ghats of India, commercially exploited for its valuable resins. Seed recalcitrance is a major problem hindering the natural regeneration of this species and it poses a great challenge in seed storage and conservation. There was a continuous import of water from the maternal tissues to seed tissues till maturity and the seeds were released in a fully hydrated state. Differential accumulation of water has been noticed in the cotyledons and embryonal axis. There was a positive correlation between seed moisture content and rate of germination which is a character of recalcitrant seeds. The critical moisture content was found to be 40% in the axis and 23.5% in the cotyledons, below which the embryo will not germinate. Loss of germination ability as a result of desiccation was attributed to the cell membrane damage, expressed as the electrolyte leakage exceeding 0.79 μS/cm. ABA peaked in the mid embryogenesis, then dropped drastically and maintained a lower level till seed maturity. On desiccation, ABA started to increase but gradually dropped down. Both cotyledons and embryonal axis had differential ABA content but exhibited a general pattern of ABA level during embryogeny. Due to the thin seed coat/embryo ratio and low investment in the seed coat, this recalcitrant seed could not hold water as efficient as orthodox seeds. Thus, it germinated as soon as it was shed from the mother plant. On desiccation, ABA shot up and moisture content decreased along with electrolyte leakage and cell membrane damage. All these hindered germination of the seed. Thus, we can see a clear interplay between moisture content and ABA levels during embryogeny and desiccation. Since the seed biology of this species has not been well documented, the present work is mainly intended to study the dynamics of water and ABA during embryogeny and embryo drying. This study can surely contribute to the long-term storage and conservation of recalcitrant seeds which is a less explored area.

Forest Resources Depletion: An Ecological Model for Biodiversity Preservation and Conservation in Cote D’Ivoire

The biodiversity-rich primary forest of Cote d’Ivoire has been substantially converted into a mosaic of secondary forests, cash and lumber plantations, food crops, and timber plantations, food crops, and wasteland. Deforestation started even before independence but has increased dramatically in the last three decades, resulting in the loss of most of the country’s biodiversity. It is essential to have information about the condition of the country’s natural resources following many human pressures. This research aimed to examine the Cote d’Ivoire Phytogeographical zones to understand the state of the wood’s ad wildlife in 2020 about the anthropic pressure on the whole Ivorian land. The Land-Use Planner approach has been used as a tool for creating a model for preserving biodiversity. There are 15 endangered tree species recognized, five each phytogeographical zone. Buffaloes are seen and distributed in the West and north of Cote d’Ivoire, duikers are observed in nearly all phytogeographical zones, elephants are observed in the West and North. At the same time, harnessed guibs are observed and dispersed across the nation, according to the findings. In terms of endangered tree species, the most frequent endangered trees species in the country’s south are Strombosia pustulata (6.2%), Diospyros mannii (5.1%), Protomegabaria stapfiana (3.7%), Musanga cecropiodes (3.6%), and Xylopia quintasii (3.2%). In the Middle Tectona grandis accounts for (11.8%), Nesogordonia papaverifera accounts for (4.2%), Cedrela odorata accounts for (3.7%), and Gmelia Arborea accounts for (2.8%). In the North, Isoberlinia doka accounts for (10.3%), Upaca togoenisis accounts for 8.9%, Anogeisssus leicarpa accounts for (5.1%), Pterocarpus erinaceus accounts for (4.6%), and Pericopsis laxiflora accounts for (3.9%). In reforested woods, the volume of merchantable wood timber of the P1, P2, and P3 categories per hectare is more significant than in wild forests. We find that biodiversity is severely endangered. Endemic species have decreased due to human activities like agriculture and logging, which are the root causes of deforestation and animal and plant biodiversity loss.

Characterization of the complete chloroplast genome of Prosopis tamarugo (Prosopis, Leguminosae), an endangered endemic tree species from the Atacama Desert

Prosopis tamarugo (Prosopis, Sect. Strombocarpa) is an important endangered tree species from the Atacama Desert (Chile). However, this species requires urgent conservation measures, for which it is necessary to evaluate their genetic diversity. Here, we present the characterization of the complete chloroplast genome of P. tamarugo; the first complete chloroplast of a species from the Strombocarpa section, obtained by next generation sequencing (NGS) methods. The complete chloroplast contains 161,575 bp and a total of 129 genes. A phylogenetic analysis of four Prosopis plastomes revealed that P. tamarugo is a sister species of the other Prosopis species albeit having smaller chloroplast sequence compared to those of other Prosopis species. Nine DNAcp markers were detected to distinguish between haplotypes. Therefore, the chloroplast sequence of P. tamarugo could be highly valuable for upcoming phylogenetic studies.

Low genetic diversity and population differentiation in Thuja sutchuenensis Franch., an extremely endangered rediscovered conifer species in southwestern China

Thuja sutchuenensis Franch. is an extremely endangered conifer (Cupressaceae) species that is endemic to southwestern China. It was once considered extinct in the wild and was rediscovered after 100 years later in October 1999. Due to the habitat destruction from nature and humans, the population has decreased sharply and the distribution range is narrow. Thus there is an urgent need to evaluate genetic variation within this species in order to establish a feasible conservation strategy. In this study, we used six single-copy nuclear loci (4CL, LEAFY, NEEDLY, CC1147, GAPC and RABGGTB) to investigate the genetic diversity, population structure and dynamics of T. sutchuenensis based on a sampling of 109 individuals from 6 natural populations across the known extant geographical range. Our results indicated that the genetic diversity of T. sutchuenensis was relatively lower (πt = 0.00219, θwt = 0.00240) than that of other Cupressaceae species. Extensive gene flow (Nm ≥ 11.07) and low genetic differentiation among populations were detected. Extended Bayesian skyline plots revealed that the population size of T. sutchuenensis has remained constant through time. The low genetic diversity was believed to result primarily from genetic drift caused by habitat fragmentation and population dynamics caused by climate fluctuations. The low genetic differentiation among populations was largely attributed to high levels of gene flow and small geographic distribution. Based on the above analyses, we should first conserve all extant populations and their habitats to maintain its current genetic diversity. Besides these, artificial propagation efforts such as seed propagation, cuttage breeding or tissue culture methods should be made to rescue this rare and endangered tree species.

Tree growth decline as a response to projected climate change in the 21st century in Mediterranean mountain forests of Chile

Global Climate Models project that observed climate trends are likely to be preserved and the number of extreme events will be increasing during the rest of the 21st century, which may have a detrimental impact on forest ecosystems. These impacts may include forest decline and widespread dieback of the most vulnerable biomes, such as the Mediterranean Forest of Central Chile (MFCC). Nothofagus macrocarpa and Austrocedrus chilensis are two canopy-dominant, endangered tree species in the mountains of MFCC. Here, we project tree growth of these species based on tree-ring width chronologies, a simplified version of a process-based model, and climate change projections. We used the tree ring information derived from ~400 trees from 12 sites distributed across MFCC in combination with the simplified version of process-based Vaganov-Shashkin tree-growth model (VS-Lite) to forecast changes in tree growth for the next four decades. Tree growth projections were made on the basis of monthly values of temperature and precipitation from the output of 35 climate models based on two ensembles of CO 2 emission scenarios of the IPCC AR5 (RCP 8.5: higher-emission scenario, and RCP 2.6: lower-emission scenario). For the MFCC region these scenarios result in temperature rise ranging between 0.5 °C and 2.0 °C, and a precipitation decrease between 5% and 20% by the year 2065, as related to historical conditions. Our results showed that the VS-Lite model is capable of reproducing tree growth decline during the recent extreme dry period, i.e. 2010–2018, which supports its use for tree growth projections in the MFCC region. According to the modeling results, we find that tree growth in both N. macrocarpa and A. chilensis forests distributed in the MFCC region will be adversely affected by future climate changes, mainly starting from the year 2035, under both scenarios. Our work provides evidence of the degree of vulnerability of Mediterranean mountain forests in central Chile according to current climate change projections. The projected decline in tree growth indicates serious risks in the dynamics and survival of these forests relatively soon, so alerts are given about this situation which may require to counteract the deleterious effects of global change on vegetation in this region. • A VS-Lite model was used to project radial growth from two mountain tree species of Central Chile Mediterranean forests. • The tree-growth model was robustly calibrated and validated for its use in future growth projections under climate change. • A significant tree growth decline in response to climate change is projected in Central Chile by 2065.

Distribution of Syzygium travancoricum Gamble (Myrtaceae), a Critically Endangered tree species from Kerala part of Western Ghats, India

Syzygium travancoricum Gamble is an endemic, Critically Endangered tree species found in marshy swamps of the Western Ghats. An assessment was conducted on existing distribution pattern and population structure of this species in Kerala. Most of the existing populations are mainly located in sacred groves and this tree is an ideal example on role of sacred groves in conserving biodiversity especially IUCN red listed species. A total of 465 individuals were recorded in which maximum number of sapling density was recorded in Kalasamala Sacred grove followed by patches of Myristica swamps in Kulathupuzha. Fragmentation of populations, habitat modification, over exploitation, pollution and invasion of exotics are major threats to S. travancoricum. Hence urgent intervention is required for restoration programmes, management of habitat and subsequently delisting this species from IUCN red list of threatened species.

First Report of Southern Blight of Manglietia decidua Caused by Sclerotium rolfsii in China.

Manglietia decidua, named 'Hua manglietia', belonging to the Magnoliaceae family, is one of the most important ornamental plant in China. In 2019 and 2020, an unknown disease caused 3- to 12-month plants of M. decidua to wither and die in the field in Zhanjiang, Guangdong province（N21°9'3";E110°17'47"）. Initially, the infected plants showed leaves dehydration, chlorosis and wilting with water-soaked lesions on stems at ground level. About 7 days later, the plants completely wilted, collapsed and died. Delayed and stunted growth with wilting of foliage continued through the whole year. Dense white mycelial mat and small white-to-brown spherical sclerotia were observed on the surface of the stalk lesion when weather conditions were warm and humid. Approximately 10% of plants were infected. Especially from July to October 2020, up to 30% of about 500 plants were infected and died. To identify the causal agents of the disease, infected tissue and sclerotia were collected, surface disinfected in 75% alcohol for 30s and 30% hydrogen peroxide solution for 5 min, and washed with sterile water for 1 min. The surface disinfected tissue and sclerotia were put on potato dextrose agar containing ampicillin (50mg/L) and kept in an incubator at 25°C in the dark. Fast growing fungus colonies with white mycelium and numerous sclerotia developed in the plates after 6 to 8 days of incubation. The hyphae were septate, hyaline and formed typically clamp connection after 10 days of growth. Sclerotia were initially white and became tan to dark brown over time and 1.0 to 3.0 mm (2.13 mm on average, n=124) in diameter at maturity. For molecular identification，the ITS region was amplified using primer pair ITS1/ITS4 (White et al. 1990). A 666 bp PCR product was sequenced (GenBank accession no. MW093622) and shared above 99% sequence identity with some Athelia rolfsii isolates (GenBank accession Nos. HQ895869, KX499470 and AB075290). Based on morphological and molecular characteristics, the fungus was identified as Sclerotium rolfsii (teleomorph A. rolfsii) （Paul et al. 2017，Xu et al. 2010. Pathogenicity tests were conducted by inoculating ten healthy 1-year-old M. decidua plants grown in pots. Five sclerotia and mycelial mat obtained from 15-day-old cultures were buried adjacent to the stem of each unwounded healthy plant. Non-inoculated plants served as controls. After inoculation, the plants were maintained in a 25-28 ℃ greenhouse and watered regularly to keep the soil moisture content at about 15%. Symptoms of southern blight were observed on all inoculated plants, which began to wilt 7 to 10 days after inoculation and died within 15 to 20 days. The control plants remained healthy. S. rolfsii was again isolated from the artificially inoculated plants, but not from non-inoculated plants. The pathogenicity test was repeated twice and the results were the same. S. rolfsii has an extensive host range worldwide and the common host ornamental plants are Iris, Chrysanthemum, CymbidiumTrifolium, Jasminum, Begonia, and Stevia etc. in China. To our knowledge, this is the first report of southern blight caused by S. rolfsiii on M. decidua in China. M. decidua is a horticultural plant which belongs to the protected and endangered tree species. This finding is important to alert growers to realize the proper management of this disease during species protection and cultivar extension.

Isolation and characterization of twelve polymorphic microsatellite markers in the endangered Hopea hainanensis (Dipterocarpaceae).

Microsatellite markers were isolated and characterized for Hopea hainanensis Merrill & Chun, an endangered tree species with scattered distribution in Hainan Island and northern Vietnam. Twenty‐six microsatellite markers were developed based on next‐generation sequencing data and were genotyped by capillary electrophoresis on an ABI 3730xl DNA Analyzer. Twelve markers were found to be polymorphic in H. hainanensis. GENODIVE analyses indicated that the number of alleles ranged from 2 to 6 per locus, and the observed and expected heterozygosity varied from 0 to 0.755 and from 0.259 to 0.779, respectively. Primer transferability was tested with Hopea chinensis Hand.‐Mazz. and Hopea reticulata Tardieu, in which 3 and 7 microsatellite markers were found to be polymorphic, separately. The results showed that H. reticulata and H. hainanensis had similar levels of genetic diversity. A neighbor joining dendrogram clustered all individuals into two major groups, one of which was exclusively constituted by H. hainanensis, while the other consisted of two subgroups, corresponding to H. reticulata and H. chinensis, respectively. The 12 polymorphic microsatellite markers could be applied to study genetic diversity, population differentiation, mating system, and fine‐scale spatial genetic structures of H. hainanensis as well as its close relatives, facilitating the conservation and restoration of these endangered but valuable Hopea species.

Importance of microhabitat selection by birds for the early recruitment of endangered trees in a fragmented forest

BackgroundRemnant microhabitats are important for bird habitat selection and plant regeneration in the fragmented habitat. However, empirical information on the consequences of how microhabitat use by birds affects the early recruitment of plants is lacking.MethodsIn this study, we evaluated whether microhabitat selection by the Black Bulbul (Hypsipetes leucocephalus) (J. F. Gmelin, 1789) impacts the early recruitment of the endangered tree species, the Chinese Yew (Taxus chinensis (Pilger) Rehd), in a fragmented forest over a 4-year period (2011–2012, 2018–2019).ResultsOur results showed the main factors affecting H. leucocephalus microhabitat selection were distance to the nearest T. chinensis mature tree, herb cover and density, leaf litter cover, and vegetation type. Moreover, the results of logistic regression also highlighted the importance of elevation, distance to light gap and roads, tree cover in bird microhabitat selection. Furthermore, the seed emergence rate in microhabitats used by birds did not differ from the natural forest, which was related to five factors of bird microhabitat. The Random Forest model showed that seedling emergence rate was increased with leaf litter cover and distance to fallen dead trees, but decreased in relation to herb cover, slope, and elevation.ConclusionOur results highlight the importance of remnant microhabitats in fragmented forests for sustaining forest ecology and optimal management. The contribution of microhabitats used by birds to plant recruitment provides insights into how frugivore species contribute to plant regeneration, which should be incorporated in future conservation and management practices of fragmented forests.

The Threat of the Combined Effect of Biotic and Abiotic Stress Factors in Forestry Under a Changing Climate.

Plants encounter several biotic and abiotic stresses, usually in combination. This results in major economic losses in agriculture and forestry every year. Climate change aggravates the adverse effects of combined stresses and increases such losses. Trees suffer even more from the recurrence of biotic and abiotic stress combinations owing to their long lifecycle. Despite the effort to study the damage from individual stress factors, less attention has been given to the effect of the complex interactions between multiple biotic and abiotic stresses. In this review, we assess the importance, impact, and mitigation strategies of climate change driven interactions between biotic and abiotic stresses in forestry. The ecological and economic importance of biotic and abiotic stresses under different combinations is highlighted by their contribution to the decline of the global forest area through their direct and indirect roles in forest loss and to the decline of biodiversity resulting from local extinction of endangered species of trees, emission of biogenic volatile organic compounds, and reduction in the productivity and quality of forest products and services. The abiotic stress factors such as high temperature and drought increase forest disease and insect pest outbreaks, decrease the growth of trees, and cause tree mortality. Reports of massive tree mortality events caused by “hotter droughts” are increasing all over the world, affecting several genera of trees including some of the most important genera in plantation forests, such as Pine, Poplar, and Eucalyptus. While the biotic stress factors such as insect pests, pathogens, and parasitic plants have been reported to be associated with many of these mortality events, a considerable number of the reports have not taken into account the contribution of such biotic factors. The available mitigation strategies also tend to undermine the interactive effect under combined stresses. Thus, this discussion centers on mitigation strategies based on research and innovation, which build on models previously used to curb individual stresses.

Genetic diversity and population structure in the endangered tree Hopea hainanensis (Dipterocarpaceae) on Hainan Island, China.

Hopea hainanensis Merrill & Chun (Dipterocarpaceae) is an endangered tree species restricted to Hainan Island, China and a small part of Northern Vietnam. On Hainan Island, it is an important indicator species for tropical forests. However, because of its highly valued timber, H. hainanensis has suffered from overexploitation, leading to a sharp population decline. To facilitate the conservation of this species, genetic diversity and population structure were assessed using 12 SSR markers for 10 populations sampled across Hainan Island. Compared to non-threatened Hopea species, H. hainanensis exhibited reduced overall genetic diversity and increased population differentiation (AMOVA: FST = 0.23). Bayesian model-based clustering and principal coordinate analysis consistently assigned H. hainanensis individuals into three genetic groups, which were found to be widespread and overlapping geographically. A Mantel test found no correlation between genetic and geographical distances (r = 0.040, p = 0.418). The observed genetic structure suggests that long-distance gene flow occurred among H. hainanensis populations prior to habitat fragmentation. A recent population bottleneck was revealed, which may cause rapid loss of genetic diversity and increased differentiation across populations. Based on these findings, appropriate strategies for the long-term conservation of the endangered species H. hainanensis are proposed.

Influence of neighbor competition and tree attributes on the fruit production of Sinomanglietia glauca, an endangered tree species endemic to China

Sinomanglietia glauca is a critically endangered species with limited population and narrow distribution in China. Yet to date, we know surprisingly little about how the characteristics of forests affect the reproduction process of S. glauca individuals. The fruit production of S. glauca individuals was examined in artificial forest (AF), free-encroached deciduous forest (FF), and intensively encroached forest by evergreen trees and moso bamboos (EF) at Mingyueshan Mountain in Jiangxi province. The relationships between the characteristics of fruits and seeds and those of parent trees and neighborhood were analyzed through redundancy analysis. The fruiting indicators (number, weight and volume of fruits/seeds) for S. glauca in AF were significantly higher than those in EF and FF. The fruit production was positively related to the crown radius and the ratio of crown length to tree height, and was negatively linked to neighbor enclosure index. The characteristics of parent trees, neighborhood and their interaction explained the variation of fruit production by 70.6%. Although the competition of neighbors exerted less explanatory power than the characteristics of parent trees, it was negatively correlated with the crown radius and volume. The crown radius and neighbor enclosure were identified as the two dominant causal factors taking the major responsibility to the fruit production. The increasing competition from neighbors bring detrimental impacts on the fruiting of S. glauca. Efficient management strategies were proposed to reduce the interference from neighbors, such as reasonably pruning and thinning adjacent evergreen trees and bamboos.

SEMANTIC SEGMENTATION OF ENDANGERED TREE SPECIES IN BRAZILIAN SAVANNA USING DEEPLABV3+ VARIANTS

Abstract. Knowing the spatial distribution of endangered tree species in a forest ecosystem or forest remnants is a valuable information to support environmental conservation practices. The use of Unmanned Aerial Vehicles (UAVs) offers a suitable alternative for this task, providing very high-resolution images at low costs. In parallel, recent advances in the computer vision field have led to the development of effective deep learning techniques for end-to-end semantic image segmentation. In this scenario, the DeepLabv3+ is well established as the state-of-the-art deep learning method for semantic segmentation tasks. The present paper proposes and assesses the use of DeepLabv3+ for mapping the threatened Dipteryx alata Vogel tree, popularly also known as cumbaru. We also compare two backbone networks for feature extraction in the DeepLabv3+ architecture: the Xception and MobileNetv2. Experiments carried out on a dataset consisting of 225 UAV/RGB images of an urban area in Midwest Brazil demonstrated that DeepLabv3+ was able to achieve in mean overall accuracy and F1-score above 90%, and IoU above 80%. The experimental analysis also pointed out that the MobileNetv2 backbone overcame its counterpart by a wide margin due to its comparatively simpler architecture in view of the available training data.

Anachronic Fruit Traits and Natural History Suggest Extinct Megafauna Herbivores as the Dispersers of an Endangered Tree.

Megafaunal seed dispersal syndrome refers to a group of traits attributed to the evolution of plants in the presence of large mammals. Present-day plants that bear these traits in areas where megafauna are absent are presumed to represent anachronic dispersal systems. Gomortega keule is an endangered tree species from a monotypic family (Gomortegaceae), endemic to Chile. Its fruit traits suggest adaptation to seed dispersal by large vertebrates; however, none are present today along its area of distribution. Here, we conducted a detailed revision on the fruit morphology of G. keule to examine whether its fruit traits fit a megafaunal dispersal syndrome. Additionally, we examined the fruit processing behavior of large domestic and captive wild animals fed with G. keule fruits, and its effect on germination. G. keule fruits had traits consistent with those of a Type 1 megafaunal fruit. Compared to intact, whole stones, seed germination probabilities decreased when fruits were handled by animals, suggesting that the seed was damaged during mastication and/or ingestion. Moreover, results from our feeding trials with elephants may also imply low efficiency of extinct gomphotheres as seed dispersers of this species. Our results also suggest that although domestic animals may disperse G. keule, it is unlikely that at present they can substitute the services of its original dispersers. Further investigation on seedling survival, local livestock management and forest management practices may help reinstate sexual regeneration in G. keule. Finally, integrating observations on fruit ecology and local people’s knowledge with experimental data enriches our species-centered approach and may help to address regeneration problems in other endangered plants.

Analysis of genetic diversity and population structure in endangered Populus wulianensis based on 18 newly developed EST-SSR markers

Populus wulianensis is an endangered tree species endemic to Shandong Province, China. Genetic diversity assessments represent the basis and a prerequisite for protecting endangered species. In our study, a total of 116 individuals of P. wulianensis from 4 extant populations (3 wild populations and 1 artificial population that covered the entire geographic distribution of the species) were analyzed using 18 expressed sequence tag-simple sequence repeat (EST-SSR) markers to assess their genetic diversity and population structure. The 18 EST-SSR markers had high levels of polymorphisms (PIC = 0.698), and 202 alleles were amplified. The present study revealed high genetic diversity at the population level (Na = 4.847, NR = 3.000, HS = 0.624, HE = 0.611, I = 1.114, and PPL = 98.6%) and the species level (HT = 0.741). Private alleles were detected in all four populations (including the artificial population JYS). Negative inbreeding coefficients (FIS<0) indicated that the populations of P. wulianensis produced too many heterozygotes due to outbreeding and that there might be a risk of outbreeding depression. The AMOVA results showed that 19.05% and 80.95% of the total variation occurred among and within populations, respectively. Obvious genetic differentiation between populations (FST = 0.191) and a high level of gene flow (Nm = 2.566) were detected, indicating that gene flow is not the main cause of genetic differentiation among populations. The results of UPGMA cluster analysis, PCoA and structure analysis (ΔK = 4) showed that the 4 populations were clustered into four groups and suggested that the natural population ZHS gave rise to the artificial population JYS. The genetic bottleneck analysis results suggested that three populations (ZHS, JXS and JYS) recently experienced bottleneck events. These genetic results are of great significance for scientifically formulating conservation strategies for endangered P. wulianensis.

Using ForeStereo and LIDAR data to assess fire and canopy structure-related risks in relict Abies pinsapo Boiss. forests.

In this study we combine information from aerial LIDAR and hemispherical images taken in the field with ForeStereo—a forest inventory device—to assess the vulnerability and to design conservation strategies for endangered Mediterranean fir forests based on the mapping of fire risk and canopy structure spatial variability. We focused on the largest continuous remnant population of the endangered tree species Abies pinsapo Boiss. spanning 252 ha in Sierra de las Nieves National Park (South Andalusia, Spain). We established 49 sampling plots over the study area. Stand structure variables were derived from ForeStereo device, a proximal sensing technology for tree diameter, height and crown dimensions and stand crown cover and basal area retrieval from stereoscopic hemispherical images photogrammetry. With this information, we developed regression models with airborne LIDAR data (spatial resolution of 0.5 points∙m−2). Thereafter, six fuel models were fitted to the plots according to the UCO40 classification criteria, and then the entire area was classified using the Nearest Neighbor algorithm on Sentinel imagery (overall accuracy of 0.56 and a KIA-Kappa Coefficient of 0.46). FlamMap software was used for fire simulation scenarios based on fuel models, stand structure, and terrain data. Besides the fire simulation, we analyzed canopy structure to assess the status and vulnerability of this fir population. The assessment shows a secondary growth forest that has an increasing presence of fuel models with the potential for high fire spread rate fire and burn probability. Our methodological approach has the potential to be integrated as a support tool for the adaptive management and conservation of A. pinsapo across its whole distribution area (<4,000 ha), as well as for other endangered circum-Mediterranean fir forests, as A. numidica de Lannoy and A. pinsapo marocana Trab. in North Africa.