Inferring the genetic responses to acute drought stress across an ecological gradient

Background How do xerophytic species thrive in environments that experience extreme annual drought? Although critical to the survival of many species, the genetic responses to drought stress in many non-model organisms has yet to be explored. We investigated this question in Mentzelia section Bartonia (Loasaceae), which occurs throughout western North America, including arid lands. To better understand the genetic responses to drought stress among species that occur in different habitats, the gene expression levels of three species from Mentzelia were compared across a precipitation gradient. Two de novo reference transcriptomes were generated and annotated. Leaf and root tissues were collected from control and drought shocked plants and compared to one another for differential expression. A target-gene approach was also implemented to better understand how drought-related genes from model and crop species function in non-model systems. Results When comparing the drought-shock treatment plants to their respective control plants, we identified 165 differentially expressed clusters across all three species. Differentially expressed genes including those associated with water movement, photosynthesis, and delayed senescence. The transcriptome profiling approach was coupled with a target genes approach that measured expression of 90 genes associated with drought tolerance in model organisms. Comparing differentially expressed genes with a ≥ 2 log-fold value between species and tissue types showed significant differences in drought response. In pairwise comparisons, species that occurred in drier environments differentially expressed greater genes in leaves when drought shocked than those from wetter environments, but expression in the roots mostly produced opposite results. Conclusions Arid-adapted species mount greater genetic responses compared to the mesophytic species, which has likely evolved in response to consistent annual drought exposure across generations. Drought responses also depended on organ type. Xerophytes, for example, mounted a larger response in leaves to downregulate photosynthesis and senescence, while mobilizing carbon and regulating water in the roots. The complexity of drought responses in Mentzelia suggest that whole organism responses need to be considered when studying drought and, in particular, the physiological mechanisms in which plants regulate water, carbon, cell death, metabolism, and secondary metabolites.

First Assessment of Nocturnal Lepidopteran Communities in the Forest Savannah Mosaic of the Plateaux Batéké, Southeastern Gabon

Lepidopterans are an important component of central African biodiversity. Indeed, they play an important role as plant pollinators, food source, bio-indicators, and even pests for local crops. However, almost nothing is known about these moths in central Africa, while they are being increasingly threatened by significant landscape changes due mainly to infrastructure constructions and climate change. So, the mosaic of forests and savannah in the Plateaux Batéké (southeastern Gabon) constitutes a unique opportunity to study how Lepidopteran communities might evolve along an ecological gradient with upcoming changes in forest cover in the region. A total of 2824 specimens, representing 14 distinct families or subfamilies, were sampled using light-trapping and sorted into morphospecies, while a subset of 95 samples was further investigated using both morphological and molecular methods. Community comparison of nocturnal Lepidopteran showed that there was a significant difference in terms of abundance only between sampling sessions. Indeed, this could be due to food availability between sampling sessions. In May and June in Gabon, most plants have flowers and fruits and moth families such as Geometridae and Sphingidae emerge at that time. The most represented family in our sampled specimens was the Geometridae, which prefers habitats with permanent river courses as is the case in our sampling area. However, a more comprehensive study using various trapping methods, during several seasonal cycles and with more replicates in each habitat type is needed for a better understanding of the community structure and ecological traits that characterize nocturnal Lepidopteran in the Plateaux Batéké of Gabon.

Spawning behavior of Aedini (Diptera: Culicidae) in a remnant of Atlantic Forest in the state of Rio de Janeiro

Background Mosquito assemblages are organized along an ecological gradient, including small habitats where interspecific competition predominates and large permanent habitats where predation predominates. This study aimed to analyze the oviposition behavior of mosquitoes regarding the preference for traps installed at two different heights with regard to ground level and the tendency to share spawning sites in an Atlantic Forest fragment in Nova Iguaçu, State of Rio de Janeiro, Brazil. Methods The eggs were collected from April 2018 to March 2019. Twelve ovitraps were used, randomly distributed in trees at ground level and at a height of 3 m in a forest environment. Results They were sequentially numbered, monitored, and replaced every 2 weeks. Among the 5818 eggs collected, 3941 hatched, 3756 reached the pupa stage, and 2370 reached the adult stage. The most abundant species were Aedes albopictus (63%) and Haemagogus leucocelaenus (35%), followed by Aedes terrens (2%) and Haemagogus janthinomys (1%). Analyses showed a significant difference of (P = 0.02) between the number of mosquito species collected in the palettes at ground level and the number collected at the height of 3 m. Cluster analysis of species abundance showed that the eggs collected in the palettes at ground level were more abundant than those collected in the palettes at the height of 3 m. We detected co-occurrence of species in the oviposition palettes; according to the null model, such species distribution was not random. Conclusions The exploitation of oviposition sites by mosquito species can represent an event forced by population density facilitated by the ecological valence of individuals of one species. Understanding the aggregate distribution of larvae at the oviposition site allows us to conduct more in-depth studies of the oviposition behavior of female mosquitoes. Graphical Abstract

Nationwide Assessment of Population Structure, Stability and Plant Morphology of Two Mimusops Species along a Social-Ecological Gradient in Benin, West Africa

Understanding tree species autecology and population structure supports effective conservation actions. Of particular importance are multipurpose trees that provide non-timber forest products (NTFPs). We assessed the population structures and morphologies of two species of NTFP trees in the genus Mimusops across bioclimatic zones in Benin by sampling 288 plots within 11 forests. Structural characteristics were compared between species, forests and zones. Correlations were also observed between Mimusops tree regeneration density, tree features and ecological characteristics. The density of trees ≥5 cm and of regeneration and mean tree height were higher for M. andongensis (within more protected forest) than M. kummel (in forests with access to people), while the highest mean diameter was observed for M. kummel. Tree and regeneration densities and mean height were greatest in the humid zone of Benin, whilst the largest mean diameter was obtained in the sub-humid zone. The results showed significant correlations between regeneration density and soil properties for M. andongensis but not for M. kummel. The correlations between tree morphology and soil characteristics were weak for both species. Ecological characteristics, along with the species’ functional traits and pressures, are important factors related to the observed differences between the species. All diameter classes were represented, and the population seemed more stable in the more protected forest relative to other forests. Mimusops trees with a diameter of 5–15 cm represented more than 30% of this species in most forests; this suggests, for M. kummel, whose trees flower when quite small (≥6 cm dbh), that there are sufficient reproductive trees. Thus, as a long-lived species, its populations could be maintained even with low/episodic recruitment. However, we found no regeneration in many forests and climate change could threaten populations. Therefore, it is important to investigate regeneration growth and dynamics, seed production and germination of the species in relation to the biophysical conditions and disturbances experienced by Mimusops stands.

Reviews and syntheses: Composition and characteristics of burrowing animals along a climate and ecological gradient, Chile

Although the burrowing activity of some species (e.g., gophers) is well studied, a comprehensive inventory of burrowing animals in adjacent biomes is not yet known, despite the potential importance of burrowing activity on the physical and chemical evolution of Earth's surface. In this study, we review the available information with a focus on the following: (a) an inventory of burrowing vertebrates and invertebrates along the climate and ecological gradient in Chile; (b) the dimensions and characteristics of burrows; and (c) calculation of excavation rates by local species compositions. Methods used include a literature compilation (> 1000 studies) of Chilean burrowing animal species integrated with global, species-specific excavation rates. A field study augments literature findings with quantification of the zoogeomorphic effects on hillslope mass transport at the animal community level and along the arid to humid–temperate climate gradient within the Chilean Coastal Cordillera (27–38∘ S latitude). The literature review indicates a minimum of 45 vertebrate and 345 invertebrate burrowing species distributed across Chile in different biomes. Burrowing depths for Chilean mammals range between 3 m (e.g., for skunks, Conepatus) and 0.25 m (for rock rats, Aconaemys). For invertebrates, burrowing depths in Chile range between 1 m for scorpions to 0.3 m for spiders. In comparison, globally documented maximum burrow depths reach up to more than 6 m for vertebrates (gopher tortoises and aardvarks) and 4 m for invertebrates (ants). Minimum excavation rates of local animal communities observed from field sites in Chile are 0.34 m3 ha−1 yr−1 for the arid site, 0.56 m3 ha−1 yr−1 for the semiarid site, 0.93 m3 ha−1 yr−1 for the mediterranean site and 0.09 m3 ha−1 yr−1 for the humid–temperate site, with the latter likely an underestimation. The calculated minimum Chilean excavation rates are within the large range of globally observed single species rates ranging between 0.01 and 56.20 m3 ha−1 yr−1 for vertebrates and from 0.01 to 37.31 m3 ha−1 yr−1 for invertebrates. Taken together, results not only highlight the diverse and latitudinally varying number of burrowing vertebrates and invertebrates present in different biomes, but also foster the understanding of how burrowing activity changes over a gradient and is influenced by mean annual temperature, mean annual precipitation, slope aspect and latitudinal-related incoming solar energy.

Climate Change and Possible Impacts on Travel and Tourism Sector

Nepal is a diverse country with lowlands of Terai to the highest mountains attracting many tourists and visitors to make visits. So, the tourism in Nepal is primarily nature-based as tourists are mostly attracted by the spectacular landscapes, majestic mountains, glaciers, lakes, rivers and biodiversity across its diverse ecological gradient. Mountaineering, trekking, whitewater rafting and jungle safari tours are the main forms of nature-based tourism activities in our country. Climate change is affecting Nepal in a number of ways and the travel and tourism sector cannot remain untouched. Various studies on climate change shows increased weather uncertainties and extremities resulting into long dry period and intense rain during monsoon leading to increased water induced disasters like floods, inundation, landslides, cloudburst floods, and glacial lake outburst floods (GLOFs) which are projected to continue in future as well. This has affected natural landscapes, and Himalayas influencing every walk of life and livelihood options. Though the impacts of climate change can be observed in the whole world, poor country like Nepal is likely to suffer most due to limited resources to cope with and adapt to the effects of climate change. In this paper, an effort has been made to review the impact of climate change on the travel and tourism sector in Nepal through the study of previous literatures on climate changes.

Mapping Maize Area in Heterogeneous Agricultural Landscape with Multi-Temporal Sentinel-1 and Sentinel-2 Images Based on Random Forest

Accurate estimation of crop area is essential to adjusting the regional crop planting structure and the rational planning of water resources. However, it is quite challenging to map crops accurately by high-resolution remote sensing images because of the ecological gradient and ecological convergence between crops and non-crops. The purpose of this study is to explore the combining application of high-resolution multi-temporal Sentinel-1 (S1) radar backscatter and Sentinel-2 (S2) optical reflectance images for maize mapping in highly complex and heterogeneous landscapes in the middle reaches of Heihe River, northwest China. We proposed a new two-step method of vegetation extraction and followed by maize extraction, that is, extract the vegetation-covered areas first to reduce the inter-class variance by using a Random Forest (RF) classifier based on S2 data, and then extract the maize distribution in the vegetation area by using another RF classifier based on S1 and/or S2 data. The results demonstrate that the vegetation extraction classifier successfully identified vegetation-covered regions with an overall accuracy above 96% in the study area, and the accuracy of the maize extraction classifier constructed by the combined multi-temporal S1 and S2 images is significantly improved compared with that S1 (alone) or S2 (alone), with an overall accuracy of 87.63%, F1_Score of 0.86, and Kappa coefficient of 0.75. In addition, with the introduction of multi-temporal S1 and/or S2 images in crop growing season, the constructed RF model is more beneficial to maize mapping.

Exploring the Functional Strategies Adopted by Coastal Plants Along an Ecological Gradient Using Morpho-functional Traits

Coastal dunes are characterised by strong interactions between biotic and abiotic factors along a short gradient from the shoreline to the inland region. We carried out an ecological analysis of the vegetation in a protected area of the Italian coast to evaluate the relationships among species abundance, the occurrence of morphoanatomical traits related to leaves, stems, and roots, and soil variables. Three transects were established perpendicular to the shoreline, with 27 plots distributed in the frontal dunes, backdunes, and temporarily wet dune slacks. An analysis based on community-weighted mean values showed that the pioneer communities of the frontal dunes were dominated by ruderals that are well adapted to the harsh ecological conditions of these environments, showing succulent leaves, high limb thickness values, and low values for leaf dry matter content (LDMC). The backdune vegetation was a mosaic of annual herbaceous and perennial shrub communities showing both ruderal and stress-tolerant strategies (clonality, sclerified leaves, high LDMC values, root phenolics) consistent with less extreme ecological conditions. The dune slack areas were dominated by plants showing adaptations to both arid and flooded environments, such as C4 photosynthesis, amphistomatic leaves, and abundant aerenchyma in the roots. The invasive status, C4 photosynthesis, leaf trichomes, and aerenchyma in the roots were significantly correlated with soil humidity, organic matter content, and pH. These results demonstrate the usefulness of anatomical traits (including root system traits) in understanding the functional strategies adopted by plants. Invasive species tended to occupy plots with high levels of soil moisture, suggesting an avoidance strategy for the harsh environmental conditions of coastal sand dunes. Finally, we suggest including information regarding root systems into coastal monitoring programs because they are directly linked to soil parameters useful in coastal dune management and protection.

Biosphere Reserves in the Southwest of Ethiopia

Forests that have a wide ecological gradient, diversity, and significant cover are confined in the southwestern part vis-à-vis other parts of Ethiopia, while the country is fronting biodiversity losses. The intention of this paper is comparative assessment of Majang, Kafa, Sheka, and Yayo biosphere reserves, located in the southwest of Ethiopia, regarding their status of plant diversity, challenges, and efforts of conservation. To this end, an extensive review of different journals, articles, and proceedings was made. Relevance to the objectives of the review was a selection criterion for sources inclusion. Consequently, the review indicates that all the biosphere reserves contained myriad plant biodiversity, specifically the “hotspot” of Afromontane rainforest biodiversity, with some degree of dissimilarities among them. For instance, the values of Shannon index illustrated a decreasing order in plant diversity as Sheka followed by Kafa, Yayo, and Majang biosphere reserve. Besides, out of the top ten documented plant families, the species richest families are Rubiaceae (15) in Yayo, Asteraceae (12) in Kafa, Euphorbiaceae (11) in Majang, and Asteraceae (11) in Sheka biosphere reserve, while the least species found in the families are as follows: Aspleniaceae and Sapindaceae in Majang; Poaceae, Solanaceae, and Araceae in Sheka; Celastraceae and Piperaceae in Kafa; and Fabacae and Solanaceae in Yayo. However, many challenges were encountered in all the biosphere reserves. The driving force behind is commercial coffee-tea plantation, agriculture expansion, overgrazing, firewood, charcoal, and other factors. Hence, to reduce forest conversion and biodiversity loss, the government of Ethiopia is creating conservation mechanism like the establishment of the protected area and biosphere reserve which is controlled and managed by the community and the government.