Environmental regionalization and endemic plant distribution in the Maghreb

Clustering methods based on environmental variables are useful in the planning of conservation strategies for species and ecosystems. However, there is a lack of work on the regionalization of the vast space of North Africa and the distribution of plant species. The current lists of endemic plants are focused mostly on an occurrence at the country level and not on regions with different conditions. The aim of this work was to lay out an environmental scheme for northwest Africa and to collect data about the occurrence of endemic plants in this area. Clustering with 12 of 33 tested environmental rasters was performed to divide the Maghreb into environmental clusters. Then, a list of 1618 endemic plant taxa (1243 species and 375 subspecies) was prepared and their distribution in estimated environmental clusters was examined. Eleven clusters with different conditions were estimated. The main drivers of regionalization were temperature amplitude, precipitation seasonality, and precipitation of the warmest quarter. According to the occurrence of endemic plants, northwest Africa may be divided into three zones: Atlas, Mediterranean (two environmental clusters), and southern zone (eight environmental clusters). The presented results provide a good basis for understanding the spatial patterns of the Maghreb, including its environment and species diversity. A designed list of endemic plant species together with environmental data may facilitate the planning of future research in north Africa and arranging methods of biodiversity protection.

Geospatial modeling of pre-intervention prevalence of Onchocerca volvulus infection in Ethiopia as an aid to onchocerciasis elimination

Background Onchocerciasis is a neglected tropical and filarial disease transmitted by the bites of blackflies, causing blindness and severe skin lesions. The change in focus for onchocerciasis management from control to elimination requires thorough mapping of pre-control endemicity to identify areas requiring interventions and to monitor progress. Onchocerca volvulus infection prevalence in sub-Saharan Africa is spatially continuous and heterogeneous, and highly endemic areas may contribute to transmission in areas of low endemicity or vice-versa. Ethiopia is one such onchocerciasis-endemic country with heterogeneous O. volvulus infection prevalence, and many districts are still unmapped despite their potential for O. volvulus infection transmission. Methodology/Principle findings A Bayesian geostatistical model was fitted for retrospective pre-intervention nodule prevalence data collected from 916 unique sites and 35,077 people across Ethiopia. We used multiple environmental, socio-demographic, and climate variables to estimate the pre-intervention prevalence of O. volvulus infection across Ethiopia and to explore their relationship with prevalence. Prevalence was high in southern and northwestern Ethiopia and low in Ethiopia's central and eastern parts. Distance to the nearest river (-0.015, 95% BCI: -0.025 - -0.005), precipitation seasonality (-0.017, 95% BCI: -0.032 - -0.001), and flow accumulation (-0.042, 95% BCI: -0.07 - -0.019) were negatively associated with O. volvulus infection prevalence, while soil moisture (0.0216, 95% BCI: 0.014 - 0.03) was positively associated. Conclusions/Significance Infection distribution was correlated with habitat suitability for vector breeding and associated biting behavior. The modeled pre-intervention prevalence can be used as a guide for determining priority for intervention in regions of Ethiopia that are currently unmapped, most of which have comparatively low infection prevalence.

Climate Change Increases the Expansion Risk of Helicoverpa zea in China According to Potential Geographical Distribution Estimation

Helicoverpa zea, a well-documented and endemic pest throughout most of the Americas, affecting more than 100 species of host plants. It is a quarantine pest according to the Asia and Pacific Plant Protection Commission (APPPC) and the catalog of quarantine pests for plants imported to the People’s Republic of China. Based on 1781 global distribution records of H. zea and eight bioclimatic variables, the potential geographical distributions (PGDs) of H. zea were predicted by using a calibrated MaxEnt model. The contribution rate of bioclimatic variables and the jackknife method were integrated to assess the significant variables governing the PGDs. The response curves of bioclimatic variables were quantitatively determined to predict the PGDs of H. zea under climate change. The results showed that: (1) four out of the eight variables contributed the most to the model performance, namely, mean diurnal range (bio2), precipitation seasonality (bio15), precipitation of the driest quarter (bio17) and precipitation of the warmest quarter (bio18); (2) PGDs of H. zea under the current climate covered 418.15 × 104 km2, and were large in China; and (3) future climate change will facilitate the expansion of PGDs for H. zea under shared socioeconomic pathways (SSP) 1-2.6, SSP2-4.5, and SSP5-8.5 in both the 2030s and 2050s. The conversion of unsuitable to low suitability habitat and moderately to high suitability habitat increased by 8.43% and 2.35%, respectively. From the present day to the 2030s, under SSP1-2.6, SSP2-4.5 and SSP5-8.5, the centroid of the suitable habitats of H. zea showed a general tendency to move eastward; from 2030s to the 2050s, under SSP1-2.6 and SSP5-8.5, it moved southward, and it moved slightly northward under SSP2-4.5. According to bioclimatic conditions, H. zea has a high capacity for colonization by introduced individuals in China. Customs ports should pay attention to host plants and containers of H. zea and should exchange information to strengthen plant quarantine and pest monitoring, thus enhancing target management.

Timescale-dependent responses of hydrological changes from global closed basins since the last glacial maximum

Water shortage has plagued the social development and human well-being of global closed basins. However, the hydroclimate research on different time scales in these regions remains inadequate at a global scale. In this paper, the hydrological responses from global closed basins to millennial-scale and centennial-scale cold/warm events since the Last Glacial Maximum were explored. Closed-basin lake records indicate that the westerlies-dominated closed basins are generally wetter during cold events than the corresponding warm ones on the millennial and centennial scales. In contrast, the monsoon-influenced closed basins prevail wetter climates during warm events. According to the hydroclimate simulations, precipitation seasonality plays a significant role in causing above spatial–temporal patterns. There is more winter rainfall in westerlies-dominated closed basins during cold events in the Last Glacial Maximum and Little Ice Age and more summer rainfall in monsoon-influenced closed basins during warm events in the mid-Holocene and Medieval Climate Anomaly. Under modern and future global warming, the hydroclimate changes in global closed basins show more regional differentiation, resulting in wetter mid-latitude Asian and low-latitude African closed basins but drier southwest North American and Australian closed basins.

Geographical Distribution and Relationship with Environmental Factors of Paphiopedilum Subgenus Brachypetalum Hallier (Orchidaceae) Taxa in Southwest China

The determination of the geographic distributions of orchid species and their relationships with environmental factors are considered fundamental to their conservation. Paphiopedilum subgenus Brachypetalum is one of the most primitive, ornamental, and threatened groups of Orchidaceae. However, little is known about the distribution of Brachypetalum orchids and how they are influenced by environmental factors. In this study, we developed a database on the geographical distribution of Brachypetalum orchids based on a large-scale field investigation in the Guangxi, Guizhou, and Yunnan provinces of southwest China (2019–2020). Using this database, we first adopted the nonparametric Mann–Whitney U test to analyze the differences in the geographical distributions and growth environments of Brachypetalum orchids. In addition, we also used the method of principal component analysis (PCA) to explore distribution patterns of Brachypetalum orchids in relation to environmental factors (topography, climate, anthropogenic disturbance, productivity, and soil) in southwest China. Our results indicated that Brachypetalum orchid species were mainly distributed in the karst limestone habitats of southwest China. In general, there were 194 existing localities with the occurrence of seven target orchids in the investigated area. Of the discovered species in our study, 176 locations (~90.7%) were distributed primarily in the karst habitat. Among them, the range of 780–1267 m was the most concentrated elevation of Brachypetalum orchids. In addition, the findings also suggested that the distribution of Brachypetalum orchids in southwest China was relatively scattered in geographical space. However, the density of the distribution of Brachypetalum orchids was high, between 104° and 108° E and between 25° and 26° N. The results of the Mann–Whitney U test revealed that there are obviously different geographical distributions and growth environments of Brachypetalum in southwest China. More specifically, we found some extremely significant differences (p < 0.001) in elevation, mean diurnal range, precipitation of coldest quarter, solar radiation, and exchangeable Ca2+ between the provinces of southwest China. The PCA analysis revealed that elevation, solar radiation, temperature (mean diurnal range, annual temperature range) and precipitation (precipitation seasonality, precipitation of the warmest quarter) were found to be the most significant factors in determining Brachypetalum orchids’ distribution. These findings have implications in assessing conservation effectiveness and determining niche breadth to better protect the populations of these Brachypetalum orchid species in the future.

Population structure and adaptive variation of Helichrysum italicum (Roth) G. Don along eastern Adriatic temperature and precipitation gradient

Immortelle (Helichrysum italicum (Roth) G. Don; Asteraceae) is a perennial plant species native to the Mediterranean region, known for many properties with wide application mainly in perfume and cosmetic industry. A total of 18 wild H. italicum populations systematically sampled along the eastern Adriatic environmental gradient were studied using AFLP markers to determine genetic diversity and structure and to identify loci potentially responsible for adaptive divergence. Results showed higher levels of intrapopulation diversity than interpopulation diversity. Genetic differentiation among populations was significant but low, indicating extensive gene flow between populations. Bayesian analysis of population structure revealed the existence of two genetic clusters. Combining the results of FST - outlier analysis (Mcheza and BayeScan) and genome-environment association analysis (Samβada, LFMM) four AFLP loci strongly associated with the bioclimatic variables Bio03 Isothermality, Bio08 Mean temperature of the wettest quarter, Bio15 Precipitation seasonality, and Bio17 Precipitation of driest quarter were found to be the main variables driving potential adaptive genetic variation in H. italicum along the eastern Adriatic environmental gradient. Redundancy analysis revealed that the partitioning of genetic variation was mainly associated with the adaptation to temperature oscillations. The results of the research may contribute to a clearer understanding of the importance of local adaptations for the genetic differentiation of Mediterranean plants and allow the planning of appropriate conservation strategies. However, considering that the identified outlier loci may be linked to genes under selection rather than being the target of natural selection, future studies must aim at their additional analysis.

Amazon methane budget derived from multi-year airborne observations highlights regional variations in emissions

Atmospheric methane concentrations were nearly constant between 1999 and 2006, but have been rising since by an average of ~8 ppb per year. Increases in wetland emissions, the largest natural global methane source, may be partly responsible for this rise. The scarcity of in situ atmospheric methane observations in tropical regions may be one source of large disparities between top-down and bottom-up estimates. Here we present 590 lower-troposphere vertical profiles of methane concentration from four sites across Amazonia between 2010 and 2018. We find that Amazonia emits 46.2 ± 10.3 Tg of methane per year (~8% of global emissions) with no temporal trend. Based on carbon monoxide, 17% of the sources are from biomass burning with the remainder (83%) attributable mainly to wetlands. Northwest-central Amazon emissions are nearly aseasonal, consistent with weak precipitation seasonality, while southern emissions are strongly seasonal linked to soil water seasonality. We also find a distinct east-west contrast with large fluxes in the northeast, the cause of which is currently unclear.

Prediction of Potentially Suitable Distributions of Codonopsis pilosula in China Based on an Optimized MaxEnt Model

Species distribution models are widely used in conservation biology and invasive biology. MaxEnt models are the most widely used models among the existing modeling tools. In the MaxEnt modeling process, the default parameters are used most often to build the model. However, these models tend to be overfit. Aiming at this problem, this study uses an optimized MaxEnt model to analyze the impact of past, present and future climate on the distributions of Codonopsis pilosula, an economic species, to provide a theoretical basis for its introduction and cultivation. Based on 264 distribution records and eight environmental variables, the potential distribution areas of C. pilosula in the last interglacial, middle Holocene and current periods and 2050 and 2070 were simulated. Combined with the percentage contribution, permutation importance, and jackknife test, the environmental factors affecting the suitable distribution area of this species were discussed. The results show that the parameters of the optimal model are: the regularization multiplier is 1.5, and the feature combination is LQHP (linear, quadratic, hinge, product). The main temperature factors affecting the distribution of C. pilosula are the annual mean temperature, mean diurnal range, and isothermality. The main precipitation factors are the precipitation seasonality, precipitation in the wettest quarter, and precipitation in the driest quarter, among which the annual average temperature contributes the most to the distribution area of this species. With climate warming, the suitable area of C. pilosula exhibits a northward expansion trend. It is estimated that in 2070, the suitable area of this species will expand to its maximum, reaching 2.5108 million square kilometers. The highly suitable areas of C. pilosula are mainly in Sichuan, Gansu, Shaanxi, Shanxi, and Henan Provinces. Our findings can be used to provide theoretical support related to avoiding the blind introduction of C. pilosula.

Main Ethiopian Rift landslides formed in contrasting geological settings and climatic conditions

The Main Ethiopian Rift (MER), where active continental rifting creates specific conditions for landslide formation, provides a prospective area to study the influence of tectonics, lithology, geomorphology, and climate on landslide formation. New structural and morphotectonic data from central Main Ethiopian Rift (CMER) and southern Main Ethiopian Rift (SMER) support a model of progressive change in the regional extension from NW–SE to the recent E(ENE)–W(WSW) direction, driven by the African and Somali plates moving apart with the presumed contribution of the NNE(NE)–SSW(SW) extension controlled by the Arabian Plate. The formation and polyphase reactivation of faults in the changing regional stress field significantly increase the rocks' tectonic anisotropy, slope, and the risk of slope instabilities forming. According to geostatistical analysis, areas prone to landslides in the central and southern MER occur on steep slopes, almost exclusively formed on active normal fault escarpments. Landslide areas are also influenced by higher annual precipitation, precipitation seasonality, vegetation density, and seasonality. Deforestation is also an important predisposition because rockfalls and landslide areas typically occur on areas with bushland, grassland, and cultivated land cover. A detailed study on active rift escarpment in the Arba Minch area revealed similar affinities as in a regional study of MER. Landslides here are closely associated with steep, mostly faulted, slopes and a higher density of vegetation. Active faulting forming steep slopes is the main predisposition for landslide formation here, and the main triggers are seismicity and seasonal precipitation. The Mejo area situated on the uplifting Ethiopian Plateau 60 km east of the Great Rift Valley shows that landslide occurrence is strongly influenced by steep erosional slopes and a deeply weathered Proterozoic metamorphic basement. Regional uplift, accompanied by rapid headward erosion forming steep slopes together with unfavourable lithological conditions, is the main predisposition for landslide formation; the main triggers here are intense precipitation and higher precipitation seasonality.

Landscape and climatic features drive genetic differentiation processes in a South American coastal plant

Background Historical and ecological processes shape patterns of genetic diversity in plant species. Colonization to new environments and geographical landscape features determine, amongst other factors, genetic diversity within- and differentiation between-populations. We analyse the genetic diversity and population structure of Calibrachoa heterophylla to infer the influence of abiotic landscape features on the level of gene flow in this coastal species of the South Atlantic Coastal Plain. Results The C. heterophylla populations located on early-deposited coastal plain regions show higher genetic diversity than those closer to the sea. The genetic differentiation follows a pattern of isolation-by-distance. Landscape features, such as water bodies and wind corridors, and geographical distances equally explain the observed genetic differentiation, whereas the precipitation seasonality exhibits a strong signal for isolation-by-environment in marginal populations. The estimated levels of gene flow suggest that marginal populations had restricted immigration rates enhancing differentiation. Conclusions Topographical features related to coastal plain deposition history influence population differentiation in C. heterophylla. Gene flow is mainly restricted to nearby populations and facilitated by wind fields, albeit without any apparent influence of large water bodies. Furthermore, differential rainfall regimes in marginal populations seem to promote genetic differentiation.