Community structure and species diversity dynamics of a subtropical evergreen broad-leaved forest in China:2005 to 2020

Here,we characterize the temporal and spatial dynamics of forest community structure and species diversity in a subtropical evergreen broad-leaved forest in China.We found that community structure in this forest changed over a 15-year period.Specifically,renewal and death of common species was large,with the renewal of individuals mainly concentrated within a few populations,especially those of Aidia canthioides and Cryptocarya concinna.The numbers of individual deaths for common species were concentrated in the small and mid-diameter level.The spatial distribution of community species diversity fluctuated in each monitoring period,showing a more dispersed diversity after the 15-year study period,and the coefficient of variation on quadrats increased.In 2010,the death and renewal of the community and the spatial variation of species diversity were different compared to other survey years.Extreme weather may have affected species regeneration and community stability in our subtropical monsoon evergreen broad-leaved forests.Our findings suggest that strengthening the monitoring and management of the forest community will help better understand the long-and short-term causes of dynamic fluctuations of community structure and species diversity,and reveal the factors that drive changes in community structure.

Effects of urbanization and forest type on species composition and diversity,forest characteristics,biomass carbon sink,and their associations in Changchun,Northeast China:implications for urban carbon stock improvement

Differences in forest attributes and carbon sequestration of each organ and layer between broadleaved and conifer forests of central and outer urban areas are not well-defined,hindering the precise management of urban forests and improvement of function.To clarify the effect of two forest types with different urbanization intensities,we determined differences in vegetation composition and diversity,structural traits,and carbon stocks of 152 plots(20 m×20 m)in urban park forests in Changchun,which had the largest green quantity and carbon density effectiveness.We found that 1.1-fold thicker and healthier trees,and 1.6-to 2.0-fold higher,healthier,denser,and more various shrubs but with sparser trees and herbs occurred in the central urban forests(p<0.05)than in the outer forests.The conifer forests exhibited 30–70%obviously higher tree aboveground carbon sequestration(including stem and leaf)and 20%bigger trees,especially in the outer forests(p<0.05).In contrast,1.1-to 1.5-fold higher branch stocks,healthier and more diverse trees were found in broadleaved forests of both the inner and outer forests(p<0.05).Plant size and dominant species had similarly important roles in carbon stock improvement,especially big-sized woody plants and Pinus tabuliformis.In addition,a higher number of deciduous or needle species positively affected the broadleaved forest of the central urban area and conifer forest of the outer urban area,respectively.These findings can be used to guide precise management and accelerate the improvement of urban carbon function in Northeast China in the future.

Assessment of plant diversity of endemic species of the Saharo-Arabian region in Egypt

Savanna, semi-deserts, and hot deserts characterize the Saharo-Arabian region, which includes Morocco, Mauretania, Algeria, Tunisia, Libya, Egypt, Palestine, Kuwait, Saudi Arabia, Qatar, Bahrain, the United Arab Emirates, Oman, Yemen, southern Jordan, Syria, Iraq, Iran, Afghanistan, Pakistan, and northern India. Its neighboring regions, the Sudano-Zambezian region belonging to the Paleotropical Kingdom and the Mediterranean and Irano-Turanian regions included in the Holarctic Kingdom, share a large portion of their flora with the Saharo-Arabian region. Despite the widespread acknowledgment of the region's global importance for plant diversity, an up to date list of the Saharo-Arabian endemics is still unavailable. The available data are frequently insufficient or out of date at both the whole global and the national scales. Therefore, the present study aims at screening and verifying the Saharo-Arabian endemic plants and determining the phytogeographical distribution of these taxa in the Egyptian flora. Hence, a preliminary list of 429 Saharo-Arabian endemic plants in Egypt was compiled from the available literature. Indeed, by excluding the species that were recorded in any countries or regions outside the Saharo-Arabian region based on different literature, database reviews, and websites, the present study has reduced this number to 126 taxa belonging to 87 genera and 37 families. Regarding the national geographic distribution, South Sinai is the richest region with 83 endemic species compared with other eight phytogeographic regions in Egypt, followed by the Isthmic Desert(the middle of Sinai Peninsula, 53 taxa). Sahara regional subzone(SS1) distributes all the 126 endemic species, Arabian regional subzone(SS2) owns 79 taxa, and Nubo-Sindian subzone(SS3) distributes only 14 endemics. Seven groups were recognized at the fourth level of classification as a result of the application of the two-way indicator species analysis(TWINSPAN) to the Saharo-Arabian endemic species in Egypt, i.e., Ⅰ Asphodelus refractus group, Ⅱ Agathophora alopecuroides var. papillosa group, Ⅲ Anvillea garcinii group, Ⅳ Reseda muricata group, V Agathophora alopecuroides var. alopecuroides group, Ⅵ Scrophularia deserti group, and Ⅶ Astragalus schimperi group. It's crucial to clearly define the Saharo-Arabian endemics and illustrate an updated verified database of these taxa for a given territory for providing future management plans that support the conservation and sustainable use of these valuable species under current thought-provoking devastating impacts of rapid anthropogenic and climate change in this region.

Thriving green havens in baking deserts:Plant diversity and species composition of urban plantations in the Sahara Desert

Hot arid zones represent vital reservoirs of unique species and ecosystems,holding significant importance for biodiversity.This study aimed to explore the plant diversity associated with tree plantations in urban ecosystems under hyper-arid climatic conditions in the Sahara Desert of Algeria.In May 2022,30 quadrats measuring 1 m^(2) each were established at the base of Phoenix dactylifera,Leucaena leucocephala,and Tamarix aphylla,corresponding to the dominant tree species in each of three plantations.In each quadrat,the plant quantitative inventory was conducted to measure plant diversity and similarity among the studied plantations.Based on this,we assessed the plant functional traits and rarity/abundance status of the flora.The findings revealed a diverse flora associated with the studied plantations,comprising 29 plant species grouped into 27 genera and 12 families.Notably,Poaceae(accounting for 30.8% of the flora),Asteraceae(25.0%),and Zygophyllaceae(21.6%)were well-represented.With an overall density of approximately 555 individuals/m^(2),Zygophyllum album(120 individuals/m^(2))and Polypogon monspeliensis(87 individuals/m^(2))emerged as the most abundant species.Functional trait analysis underscored the pivotal role of therophytes(constituting over 50.0% of the flora)and anemochorous species(33.0%-62.5%).Phytogeographic analysis emphasized the prevalence of the Saharo-Arabic element(constituting over 31.0% of the flora)and the Mediterranean Saharo-Arabic element(9.5%-21.5%).The Cosmopolitan element thrived under disturbance factors,recording percentages from 13.0% to 20.0% of the plant community.The rarity/abundance status of the flora emphasized the significance of rare,common,and very common species in the studied plantations.These findings could provide fundamental data for the effective control and management of biodiversity in hot hyper-arid urban ecosystems.

Genome-wide SNP markers provided insights into the reproductive strategy and genetic diversity of the green tide causative species Ulva prolifera in China

Ulva prolifera is the causative species of the annually occurring large-scale green tides in China since 2007.Its specific biological features on reproductivity strategies,as well as intra-species genetic diversity,are still largely unknown,especially at the genome level,despite their importance in understanding the formation and outbreak of massive green tides.In the present study,the restriction site-associated DNA genotyping approach(2b-RAD)was adopted to identify the genome-wide single-nucleotide polymorphisms(SNPs)of 54 individual thalli including samples collected from Subei Shoal in 2019 and Qingdao coast from 2019 to 2021.SNPs genotype results revealed that most of the thalli in 2019 and 2020 were haploid gametophytes,while only half of the thalli were gametophytes in 2021,indicating flexibility in the reproductive strategies for the formation of the green tides among different years and the dominance of asexual and vegetative reproductive mode for the floating period.Besides,population analysis was conducted,and it revealed a very low genetic diversity among samples from Subei Shoal and the Qingdao coast in the same year and a higher divergence among samples in different years.The results showed the efficiency of 2b-RAD in the exploration of SNPs in U.prolifera and provided the first genome-wide scale evidence for the origin of the large-scale green tides on the Qingdao coast.This study improved our understanding of the reproductive strategy and genetic diversity of the green tide causative species and will help further reveal the biological causes of the green tide in China.

Impacts of Human Activities and Season on Species Diversity and Abundance of Butterflies in Mpanga Kipengere Game Reserve and Surrounding Farmlands, Tanzania

Maintaining natural habitats is crucial for the preservation of insects and other species that indicate environmental changes. However, the Mpanga/Kipengere Game Reserve and its surrounding farmlands are facing disturbance due to human activities, which is putting many wildlife species, particularly larger mammals, at risk. To determine the impact of human activities on butterfly species diversity and abundance in the reserve and its surrounding areas, we conducted a study from November 2021 to October 2023. We collected butterfly data using transect walks and baited traps in two habitat types. Our study yielded 2799 butterfly Individuals ranging in 124 species divided into five families habitat, season, and anthropogenic factors are significant environmental variables influencing species diversity and abundance of butterflies. Therefore, it’s important to protect habitat and dry-season water for the conservation of invertebrates such as butterflies. Our study findings provide essential information for ecological monitoring and future assessment of the Mpanga/Kipengere Game Reserve ecosystem health.

Floristic Diversity and Conservation Status of Guineo-Congolese Species in Southeastern Cameroon: The Case of the Gari-Gombo Communal Forest

The conservation of plant biodiversity has become one of the most important objectives in the sustainable management of Guinean-Congolese ecosystems. However, in the south-east zone of Cameroon, there is a lack of rigor in the management of these forests, which can result in the loss of species of high conservation value. The study was carried out in communal forests in the south-east zone of Cameroon. Its aim was to carry out a floristic inventory and then compare the list of species with the IUCN catalog. Twenty-four plots, each with a surface area of 0.2 ha, were set up in the Gari-Gombo communal forest. All timbers with a DBH ≥ 5 cm were systematically counted. A total of 176 species, belonging to 144 genera and 45 families, were surveyed. Fabaceae (42.08%), Malvaceae (39%), Euphorbiaceae (24.64%), Moraceae (20.92%), Apocynaceae (18.64%), Cecropiaceae (16.60%), Ulmaceae (14.76%), Meliaceae (14.61%), Violaceae (14.08%), Combretaceae (12.67%), Theobroma cacao (21.17%), Baphia leptobotrys (18.06%), Rinorea sp. (14.09%), Musanga cecropioides (12.18%), Terminalia superba (10.32%), Neosloetiopsis kamerunensis (10.14%), Celtis zenkeri (8.29%) and Alstonia boonei (7.77%) were the most important taxa. Nearly 90% of the species in this forest are Guinean species, with a dominance of Guinean-Congolese species (66%). Fourteen (14) threatened species have been identified in the FCGG. This study, which highlights the rich biodiversity of communal forests, is important for guiding biodiversity conservation policies in ecosystems used for production.

Responses of arid plant species diversity and composition to environmental factors

An oasis is a unique natural landscape in arid and semi-arid areas,significant for regulating regional microclimates and hydrological processes in deserts.However,little is known regarding the response of natural oasis plants communities to various environmental factors.Nineteen sample plots(50 m×50 m)were selected in the Daliyabuyi Oasis in the Taklimakan Desert hinterland based on the location of groundwater monitoring wells and 76 vegetation quadrats(25 m×25 m)were established.A two-way indicator species analysis,Mantel test,detrended correspondence analysis,canonical correspondence analysis(CCA),and hierarchical partitioning were used to provide an in-depth analysis of community classification,species composition,and environmental interpretation of the oasis.A generalized linear model was used to verify the results which showed that the current oasis community could be divided into four types according to the dominant species,which is controlled by soil moisture.Measurement of species composition and distribution of communities showed significant differences between species diversity of individual community types.Variations in groundwater depth affects patterns of species diversity which is sensitive to richness,while the degree of surface water disturbance affects the pattern of species evenness.Moreover,the CCA ordination map showed that community distribution and diversity characteristics have their own preferences in habitat gradients.The study concluded that the species dominance of the community and the composition and distribution are not dominated by a single factor.There are differences in the scale and effect of different water resource types in maintaining community characteristics.

Impact of agricultural landscape structure on the patterns of bird species diversity at a regional scale

The loss of bird species diversity is a crucial problem in the European agricultural landscape.Change in the area coverage of major land cover types has been mentioned as one of the main factors responsible for bird biodiversity impoverishment.In this study,we focused on the impact of landscape matrix characteristics on bird species richness and on Faith’s phylogenetic diversity index on a spatial scale of 1000-m radius around the measured occurrence points.We investigated how land cover composition affects bird diversity on the landscape scale using nationwide citizen science data.In total,168,739 records of bird occurrence in the South Moravian Region of the Czech Republic during growing season from 2009 to 2019 were evaluated.We found that the presence of water bodies and wetlands significantly corresponded to the areas of highest bird species richness.We also revealed that the presence of forests(~60%of the forest in the Czech Republic is occupied by commercial forests),urban areas and arable land were negatively associated with bird species richness and phylogenetic diversity.Forests(both coniferous and deciduous)and urban habitats were found to have a tendency to host a clustered phylogenetic community structure in comparison with wetland and arable land.A strong negative association between forest proportion and bird diversity led us to conclude that the expansion of the forest(with simple species composition,horizontal and vertical structure)could be one of the critical drivers of the decline of bird species diversity in the European agricultural landscape.On the other hand,our results also pointed out that small woody features(i.e.,woodlots)and scattered woodland shrub vegetation were one of the main landscape characteristics supporting a bird diversity in rural landscape.This is in concordance with other studies which mention these landscape structures as important elements for nesting and foraging of farmland birds.We thus recommend to maintain and restore scattered trees or woodlots with complex structure in agricultural landscape.

Patterns of species richness and beta diversity of vascular plants along elevation gradient in Brazilian páramo

Understanding the relationships between plant diversity and the environment is an important step towards conservation of species and ecosystems.In this study,we hypothesize that community species richness decreases and species composition change along the elevation gradient,with a greater contribution of species turnover than nestedness to beta diversity.We surveyed plant species in 300 plots(1 m×1 m)in four elevational bands(2100 m,2300m,2500 m,and 2700 m)in the CaparaóNational Park,Southeastern Brazil.The samples presented a great number of species(97 spp.,59 genera,27families),however,74%of the species were considered rare with their relative abundance being<1%.Among the four bands along the gradient,we detected two distinct communities with few species in common.The transition between the two communities occurred at 2500 m,and this elevation band also had the highest species richness in total.A non-metric multidimensional scaling(NMDS)showed floristic differences between the bands even though they had similar richness.In 89%of the plot pairs,using pairwise comparison of species composition,only half of the species that occurred in one did occur in the other plot.The dissimilarity among the plots and elevational band reflects a significant contribution of spatial species turnover to the species richness and beta diversity on the Caparaómountain.Beta diversity increased with spatial scale(from plot to elevational-band).The dissimilarity(βSOR=0.907)in the area was due almost exclusively to spatial species turnover(βSIM=0.879),with very low contribution of species nestedness(βSNE=0.028).Our research showed that species richness does not decrease with elevation in the study area,but the floristic composition changes.The clear distinction of species along the gradient show that spatial species turnover is the major diversitygenerating process in the studied area.

Resilience effects for household food expenditure and dietary diversity in rural western China

A more resilient livelihood is increasingly recognized as an efficient way to improve vulnerable households’food security and optimize their dietary decisions.This study quantifies rural household resilience in western China,identifies the three pillars(absorptive capacity,adaptive capacity,and transformative capacity)contribution to resilience,and then establishes the estimated Resilience Capacity Index(RCI)linked with food security and dietary diversity supported by the multiple indicator multiple cause(MIMIC)model.Results show that,despite geographical heterogeneity,the RCI consistently increased from 2015 to 2021.Households with a higher RCI inheriting better capacity to deal with risk and shocks are significantly and positively correlated with increasing food expenditure and diversifying food choices.It can be because resilient households will allocate more money to food expenditure instead of saving for livelihood uncertainty.Thus,policymakers can provide more incentives for rural households to adopt more dynamic and effective risk management strategies.This,in turn,could yield positive spillover effects by preventing human capital loss associated with dietary-related chronic diseases and mortality.

Off-farm employment,agriculture production activities,and household dietary diversity in environmentally and economically vulnerable areas of Asia

Access to off-farm employment has been expected to be a critical approach to ending hunger and all forms of malnutrition,two important targets of achieving Zero Hunger.This study aims to investigate the role of off-farm employment in improving dietary diversity through substitution effect and complementary effect with agricultural production activities and income effect.This study adopts Poisson/Tobit/Probit/OLS regressions and the instrument variable method based on the primary survey data collected among 1,282 households at 12 sites in environmentally and economically vulnerable areas of China,Nepal,Cambodia,Thailand,and Myanmar in 2019.The results show that off-farm employment is positively associated with household dietary diversity and the consumption of flesh meat,fish and other aquatic animals,fruits,and milk and dairy products,which are rich in protein and micronutrients.The results of mechanism analysis show that off-farm employment contributes to household dietary diversity by improving crop diversity,especially for poor households,boosting the probability of livestock raising for households with the middle one-third disposal income,and increasing household income.The positive association between off-farm employment and household dietary diversity is much higher for households with the bottom one-third disposal income,low illiteracy,and from upper-middle income countries.These findings imply that off-farm employment does play a vital role in achieving multiple benefits of poverty alleviation,malnutrition reduction,and agrobiodiversity conservation in environmentally and economically vulnerable areas.However,it may enlarge the gaps in dietary diversity between households with low human capital and from low and lower-middle income countries and those with high human capital and from middle-high countries.

Analysis of genetic diversity and prediction of Larix species distribution in the Qinghai–Tibet Plateau,China

Larix resources in the Qinghai-Tibet Plateau have important ecological and economic values.However,the lack of genetic diversity background and related research hinders the development of conservation strategies.In this study,genetic diversity and distribution of fi ve Larix species were investigated.Using 19 polymorphic microsatellite markers to study 272 representative individuals from 13 populations,the results show low genetic diversity at the population level,with variation explained mainly by diff erentiation among populations.The Larix populations were classifi ed into two clades,one formed by eight populations,including three of the species in this study,L.kongboensis,L.speciosa,and L.potaninii var.australis.The other clade consists of fi ve populations,including the other two species in this study,L.griffi thii and L.himalaica.Genetic distance of the species was aff ected by geographical isolation and genetic diversity was mainly aff ected by altitude.The area suitable for Larix spp.decreased during the Last Glacial Maximum compared to the current distribution according to the niche model,but should increase in future climate scenarios(2050s),expanding westward along the Himalayas.These results provide an important scientifi c basis for the development of conservation strategies and further the sustainable utilization of Larix resources in the Qinghai-Tibet Plateau.

Species Composition and Diversity of Fagus longipetiolata in Leigong Mountain, Guizhou Province

[Objectives]To understand the species composition and diversity of Fagus longipetiolata community.[Methods]The F.longipetiolata community in Guizhou Province was investigated by typical plot method.[Results]There were 107 species of vascular plants belonging to 79 genera and 51 families in Leigong Mountain F.longipetiolata community,including 3 species of pteridophytes belonging to 3 genera and 3 families,104 species of spermatophytes belonging to 76 genera and 48 families,including 3 species of gymnosperms belonging to 3 genera and 3 families,and 101 species of angiosperms belonging to 73 genera and 45 families.The types of Leigong Mountain F.longipetiolata community were divided into 7 formations,and the top 10 important species of each formation were Fagaceae,followed by Lauraceae and Ericaceae.The change trend of tree layer richness index was formation I>formation IV>formation VI>formation III>formation VII>formation II>formation V;the dominance index was formation I>formation IV>formation V>formation VI>formation VII>formation III>formation II;H diversity index was formation V>formation II>formation I>formation III>formation VII>formation VI>formation IV;the evenness index is formation II>formation III>formation VI>formation VII>formation IV>formation I>formation V;the total diversity index of the community,formation I(3.67)was the highest,formation V(2.74)was the lowest,manifested as formation I>formation III>formation VI>formation II>formation IV>formation VII>formation V.[Conclusions]The community stability is closely related to its species composition,and the background species is the basis for the survival of the community;the existence of rare species can further enhance the community diversity index and enhance the community stability.

Biodiversity metrics on ecological networks: Demonstrated with animal gastrointestinal microbiomes

Biodiversity has become a terminology familiar to virtually every citizen in modern societies.It is said that ecology studies the economy of nature,and economy studies the ecology of humans;then measuring biodiversity should be similar with measuring national wealth.Indeed,there have been many parallels between ecology and economics,actually beyond analogies.For example,arguably the second most widely used biodiversity metric,Simpson(1949)’s diversity index,is a function of familiar Gini-index in economics.One of the biggest challenges has been the high“diversity”of diversity indexes due to their excessive“speciation”-there are so many indexes,similar to each country’s sovereign currency-leaving confused diversity practitioners in dilemma.In 1973,Hill introduced the concept of“numbers equivalent”,which is based on Renyi entropy and originated in economics,but possibly due to his abstruse interpretation of the concept,his message was not widely received by ecologists until nearly four decades later.What Hill suggested was similar to link the US dollar to gold at the rate of$35 per ounce under the Bretton Woods system.The Hill numbers now are considered most appropriate biodiversity metrics system,unifying Shannon,Simpson and other diversity indexes.Here,we approach to another paradigmatic shift-measuring biodiversity on ecological networks-demonstrated with animal gastrointestinal microbiomes representing four major invertebrate classes and all six vertebrate classes.The network diversity can reveal the diversity of species interactions,which is a necessary step for understanding the spatial and temporal structures and dynamics of biodiversity across environmental gradients.

Assessing Forest Cover Distribution, Species Diversity, and Richness of the Buffer Zone for Strategic Forest Management Planning for Nimule National Park, South Sudan

Natural forest ecosystems play an essential role in the conservation of biodiversity of many plants and animals by providing them with habitat and suitable environments. Studies have shown that biodiversity-protected areas reduce the loss and degradation of natural habitats to various wild species of plants. This study examined the forest resources in five subzones by conducting tree/shrub species inventory to be able to develop an effective forest management plan for the Buffer Zone Forest Reserve for the sustainable conservation of flora and fauna of Nimule National Park. This is with the view to identify the main tree and shrub species;assess the composition, distribution, and abundance of various tree/shrub species;to determine the species diversity as well as the richness of these areas in terms of growth and performance where DBH and heights of trees/shrubs in the circular sample plots were measured. The results revealed the overall mean DBH and H of 13.83 cm and 6.61 m respectively. The highest number of trees was obtained in subzone B followed by D, while the least were found in subzone A. The overall mean tree/shrub density was 0.83 tons/ha. The mean total basal area and volume per hectare were 3252.74 m2/ha and 46,540.82 m3/ha respectively. The overall species abundance and distribution indicate Combretum spp, Cedrella spp., Grewia mollis, Acacia Sieberiana, Ziziphus abysinica, and Acacia seyal were the most dominant species, with over 12 species richness at the deposition side of the River Nile, 13 species at the western side of the Nile, the Administration site shows only 7 species, the lowland of Mt. Gordon show over 14 different species, whereas over 10 species were found on the top of Mt. Gordon. The overall mean diversity indices and evenness of H’, D, and E depicted 2.507, 0.871, and 0.840 respectively. These results yielded are relatively moderate. Therefore, conservation efforts are very necessary to improve and maintain the quality of vegetation cover.

Diversity and Importance of Benin’s Forests and Agroforestry Systems Woody Species in Mortars and Pestles Manufacture

The disappearance of resources with high genetic potential and great utility for people and the challenge of the conservation and sustainable management of these resources are two opposing facts of which the world is now concerned. In Benin, forests and agroforestry systems complement each other in wood supply for mortar and pestle manufacture. Thus, this study aimed to investigate the diversity of woody species used for mortar and pestle manufacture and to analyze the preferences of manufacturers through an ethnobotanical approach. Based on the snowball sampling method, and interviews with 112 manufacturers from different ethnic groups, we identified 31 tree species. These species belong to 30 genera and 13 plant families. The Fabaceae are more represented with 14 species (i.e. 45% of the total). Ten are frequently used. But there are four species, such as Vitellaria paradoxa C. F. Gaertn., Prosopis africana (Guill. & Perr.) Taub., Terminalia glaucescens Planch. ex Benth. and Pericopsis laxiflora (Benth.) Meeuwen, which are highly preferred by manufacturers respectively. The calculation of the Indexes of Possession of Global Knowledge (IPSG) revealed that the ethnic group Nagot (0.204) possessed more knowledge and is followed by Mahi (0.201) and Fon (0.18) respectively. Forests and agroforestry systems are both supply sites for manufacturers. The non-parametric Wilcoxon test proved that there are no significant differences between the species’ preference for mortars or pestles manufacture (v = 181, p-value = 0.38). Since the trees cutting in agroforestry systems can be destructive to them, provisions such as the promotion of agroforestry in rural areas and the integration of the used species in the reforestations programs must be taken to curb the pressure and contribute to the conservation of the biodiversity.

Biodiversity responses to insular fragmentation in Amazonia: Two decades of research in the Balbina Hydroelectric Reservoir

As hydropower development expands across lowland tropical forests,flooding and concomitant insular fragmentation have become important threats to biodiversity.Newly created insular landscapes serve as natural laboratories to investigate biodiversity responses to fragmentation.One of these most iconic landscapes is the Balbina Hydroelectric Reservoir in Brazilian Amazonia,occupying>400000 ha and comprising>3500 forest islands.Here,we synthesise the current knowledge on responses of a wide range of biological groups to insular fragmentation at Balbina.Sampling has largely concentrated on a set of 22 islands and three mainland sites.In total,39 studies were conducted over nearly two decades,covering 17 vertebrate,invertebrate,and plant taxa.Although species responses varied according to taxonomic group,island area was consistently included and played a pivotal role in 66.7%of all studies examining patterns of species diversity.Species persistence was further affected by species traits,mostly related to species capacity to use/traverse the aquatic matrix or tolerate habitat degradation,as noted for species of vertebrates and orchid bees.Further research is needed to improve our understanding of such effects on wider ecosystem functioning.Environmental Impact Assessments must account for changes in both the remaining habitat amount and configuration,and subsequent long-term species losses.

Some of the Mechanisms for Coexistence of Tree Species Diversity in Tropical Forests: A Review of Effects of Tree Density Dependence

Tree communities contribute to maintenance of species diversity in tropical forests. Coexistence of many tree species is not without competition. Therefore, coexistence of tree species and size diversities occur sequentially or simultaneously in tropical natural forests. Understanding coexistence and competition mechanisms of tree species requires knowledge of interactions within and between species. However, many conservation efforts and strategies failed due to inability to identify and maintain functional coexistence mechanisms among tree species in the forest. Also, most trees died because of pressure on their habitats and not because of limiting growth resources. Hence, species identity, minimum distance and size of the neighbouring trees which are responsible for coexistence of competing trees in most tropical forests have not been explicitly reviewed. Therefore, this review evaluated some of the density dependent mechanisms for coexistence of tree species alpha diversity in tropical forests. Many interactive mechanisms are responsible for coexistence tree species in tropical forests. Inter- and intra-specific competitions are the most significant and both facilitate positive and negative density dependence. Therefore, switching from negative to positive density dependence may occur in some situations. Positive and negative density effects regulate species abundance and coexistence through conspecific and heterospecific structures. Aggregates of conspecific and heterospecific neighbours constitute forest spatial structure. Negative density interactions are mutually exclusive and basically ranged from effect of species identity of neighbours, distance to neighbours and tree size of the neighbours to reference trees in the community structures. Some mechanisms shorten distances for heterospecific than conspecific interactions. Conspecific structures improved survival and growth of rare tree species. Interactive mechanisms in tree community and population structures facilitate species diversity and size inequality, respectively.

Morphometric Traits Differentiation and Phenotypic Diversity of Two Snail Species Ecotypes Archachatina marginata and Achatina fulica in the Western Highlands of Cameroon

This study was conducted from June 2021 to January 2023 to assess the genetic diversity of giant African snails in the western highlands of Cameroon. A total of 652 snails were randomly collected from the wild in three localities in the western highlands (Bafang, Bafoussam, and Santchou). The study revealed significant variations in morphobiometric characteristics both between species and localities. The predominant shell coloration was brownish with yellow zigzag stripes (65%), while the dominant coloration for shell openings was whitish (48%). Regarding foot coloration, both brown with spotted black and black with spotted brown colorations were dominant (29%). The highest recorded live weight of snails (39.33 ± 34) was found in the species Archachatina marginata. In terms of length measurements (in mm), the length of the right and left sides of the shell was higher in the A. fulica species (49.8 ± 19.7 mm and 40.07 ± 18 mm, respectively). Bafang exhibited the highest values for shell length (56 ± 11 mm) and shell width (46.52 ± 11.46 mm). A. fulica recorded the highest shell length (81.5 ± 27 mm), while A. marginata recorded the highest shell width (49.6 ± 12.1 mm), with the highest values observed in A. fulica from fulica having a slightly higher aperture width value (30 ± 10 mm) compared to A. marginata, while A. marginata had the highest value for aperture length measurement (54.5 ± 12 mm). A. fulica also exhibited the highest values for the length from apex to the first whorl and the length from left to right of the first whorl (43.2 ± 18 mm and 39 ± 19.8 mm, respectively). Strong and positive correlations were observed between the live weight of snails and body measurements regardless of species, except for the number of whorls, which showed very weak or negative correlations with other body measurements. The results of Hierarchical Cluster Analysis (HCA) revealed three distinct snail population types. These findings provide valuable insights into the phenotypic diversity of edible land snails in the western highlands of Cameroon and can be considered in improvement and conservation programs aimed at enhancing snail meat yield.