Loss Of Species Diversity Research Articles

Environmental correlates of richness, community composition, and functional traits of terrestrial birds and mammals in a fragmented tropical landscape

Tropical forest loss and fragmentation and the associated loss in species diversity are increasing in both magnitude and scope. Much attention has been paid to how attributes of forest fragments, such as area and forest structure, impact the diversity and functional composition of vertebrate communities, while more recent work has begun to consider the importance of landscape-level variables, such as surrounding tree cover. Yet, the relative impacts of these factors on species diversity and functional composition remain unclear, particularly among under-studied taxonomic groups. We quantified how species richness, community composition, and functional traits of terrestrial birds and mammals are associated with variation in fragment area, elevation, habitat structure and surrounding tree cover. Our goal was to determine the degree to which these diverse explanatory variables contribute to species diversity. We used motion-activated camera traps to sample terrestrial birds and mammals in 22 forest fragments in northwestern Ecuador. We used a hierarchical multi-species occupancy model accounting for imperfect species detection to estimate species richness and species composition differences among fragments, weighted multiple regression and distance matrix regression to assess covariates of richness and composition, and an RLQ ordination to assess co-variation of environmental conditions and species traits. Terrestrial mammals and birds exhibited similar relationships to key environmental variables, but also showed guild-specific differences. Elevation was significantly associated with differences in species richness and community composition for both groups. Forest cover in the surrounding matrix was associated with higher species richness and changes in community composition in mammals, but not terrestrial birds. Canopy openness showed a positive association with mammalian species richness but no relationship with bird species richness. There was no association between density of large trees and richness for either group. We found no significant associations between environmental variation and functional composition among forest fragments. This work highlights the general importance of elevation and forest cover in shaping patterns of species diversity and composition in forest fragments and suggests heightened sensitivity to matrix conditions in mammals relative to terrestrial birds.

Morphological and ecological trait diversity reveal sensitivity of herbivorous fish assemblages to coral reef benthic conditions

Herbivorous fishes play a critical role in the maintenance of coral reefs through grazing and cropping of various benthic algae types. Herbivorous fish assemblages are sensitive to changes in the reef environment and are often targeted by local fisheries. This can lead to a decline in ecosystem functions if key groups are reduced. The present study investigates the morphological and ecological trait diversity of herbivorous reef fish assemblages in habitats differing in relative benthic coverage: i) coral-dominated, ii) algae-dominated, and iii) an intermediate habitat. Trait diversity for conspicuous herbivorous fishes was measured using three trait diversity indices: trait richness, trait divergence, and trait evenness. These indices were derived from in situ community surveys and feeding observations, morphological assessment of feeding mechanics from locally collected specimens, and ecological information obtained from published data. Trait diversity, reflected in higher trait evenness and lower trait richness, was lower within algae-dominated habitats than coral-dominated habitats, suggesting that algae-dominated habitats may be compromised by the lack of essential functions provided by key species. These groups reduce algal biomass and may help facilitate the survival and growth of corals, which in turn can increase coral cover. Algae-habitats were dominated with species known to consume macroalgae (rabbitfish and surgeonfish), appearing to provide essential feeding and habitat resources. These species include browsers and croppers that are fundamental in reducing algal biomass and may help facilitate the survival and growth of corals, which in turn can promote reef health. However, this habitat lacked parrotfishes known to remove turf algae and sediments, an essential function for clearing benthic space for coral settlement and other key benthic invertebrates. This study identified several species with overlapping functional roles in the coral-dominated and intermediate habitats. Still, species that were not redundant showed high trait complementarity, suggesting that their removal may result in the loss of unique functions. Importantly, we show that algae-dominated habitats supported high numbers of juvenile fishes especially in species targeted by local artisanal fishers. We also showed that the loss of trait diversity is greater than the loss of species diversity through the comparison of taxonomic and trait β-diversity, further emphasizing the importance of trait diversity analysis in understanding ecosystem health and maintenance.

Heat tolerance may determine activity time in coprophagic beetle species (Coleoptera: Scarabaeidae).

Although reports have documented loss of species diversity and ecological services caused by stressful temperature changes that result from climate change, some species cope through behavioral compensation. As temperatures and magnitudes of temperature extremes increase, animals should compensate to maintain fitness (such as through temporary behavioral shifts in activity times). Appropriate timing of activity helps avoid competition across species. Although coprophagic dung beetles exhibit species-specific temporal activity times, it is unknown whether temperature drives evolution of these species-specific temporal activity times. Using nine dung beetle species (three each of diurnal, crepuscular, and nocturnal species), we explored differences in heat stress tolerance measured as critical thermal maxima (CTmax ; the highest temperature allowing activity) and heat knockdown time (HKDT; survival time under acute heat stress) across these species, and examined the results using a phylogenetically informed approach. Our results showed that day-active species had significantly higher CTmax (diurnal > crepuscular = nocturnal species), whereas crepuscular species had higher HKDT (crepuscular > nocturnal > diurnal species). There was no correlation between heat tolerance and body size across species with distinct temporal activity, and no significant phylogenetic constraint for activity. Species with higher CTmax did not necessarily have higher HKDT, which indicates that species may respond differently to diverse heat tolerance metrics. Acute heat tolerance for diurnal beetles indicates that this trait may constrain activity time and, under high acute temperatures with climate change, species may shift activity times in more benign environments. These results contribute to elucidate the evolution of foraging behavior and management of coprophagic beetle ecosystem services under changing environments.

Fossil dipterid fern Thaumatopteris in China: new insights of systematics, diversity and tempo-spatial distribution patterns

ABSTRACT Thaumatopteris (Goeppert) Nathorst is a typical dipterid fern in the early Mesozoic, showing global significances for palaeoclimate, phytogeography and biostratigraphy. However, the detailed understanding on the relationship between species diversity and the environmental background of this genus is still unclear. Here, we reinvestigated new collections and type specimens of Thaumatopteris contracta Li et Tsao collected from the Upper Triassic of Yunnan Province, and analysed the systematic, diversity variations and tempo-spatial distribution patterns of Thaumatopteris in China. An emendation was proposed for species diagnosis of Thaumatopteris contracta based on both sterile and fertile pinnae. Our analysis demonstrates that the genus Thaumatopteris reached a higher diversity and differentiation with 11 species during the Late Triassic in China and suffered a severe loss of species diversity across the Triassic-Jurassic transition. Changes in the spatial distribution pattern of Thaumatopteris demonstrate an ecological response to local environment degradation in the Upper Yangtze region. The destruction of habitat and the block of the transport channel of warm moist flow from the Tethys Ocean caused by the Indosinian tectonic movement, especially, the uplift of the Longmen Mountains may represent the potential environmental trigger.

SARS-COV-2 and biomimetics: What saves the planet will save our health.

SARS-COV-2 and biomimetics: What saves the planet will save our health.

The Effects of Habitat Alteration on Anuran Diversity and Assemblages on Mount Mulanje, Malawi

Anthropogenic disturbance and increased environmental degradation often lead to losses in species diversity. As continuous forests become increasingly limited, it is important to determine conservation and biodiversity values of intact forests and surrounding landscapes. Currently, there is little data on how anuran communities react to the alarming growth of habitat degradation in tropical East Africa, nor on the value of remnant forests. This study evaluated the alpha, beta and gamma diversity of frogs in an altered landscape on Mount Mulanje, Malawi, East Africa, and assessed the impact of habitat degradation and diversity of a landscape matrix of various habitat types. Nine sites were sampled: three intact miombo forests, three eucalyptus plantations, and three secondary forests. Twenty-nine species were found throughout these landscapes. Intact miombo forests contained significantly more frog species than the other habitats. The degree of canopy cover and area size appeared to determine species diversity across all three landscapes. Although eucalyptus plantations were impoverished, naturally regenerating secondary forests can help relieve the effects of habitat alteration. Nevertheless, degraded habitats cannot substitute for continuous blocks of forest; therefore understanding these differences is crucial for maintaining the biodiversity value in the long term.

No Net Loss of Species Diversity After Prescribed Fires in the Brazilian Savanna

Although savannas are fire-adapted ecosystems, prescribing fire for biodiversity conservation remains controversial at least in some regions where savannas occur. Faced with uncertainty, many decision makers and even scientists are still reluctant to prescribe fire for conservation purposes in fire-prone ecosystems, invoking the precautionary principle. Knowledge gaps on the ideal fire regime, such as how and when to burn, and especially the fear of biodiversity losses, are among the main arguments against fire management applied to remnants of native savanna vegetation. To inform this debate, we assessed the impact of prescribed fires on diversity of plants (different growth forms), ants, frogs, lizards, birds, and small mammals, in savannas and grasslands of the Brazilian Cerrado. We assessed the existing species richness, composition, and abundance in areas subjected to long periods of fire suppression and compared to that observed over a short period after prescribed dry-season fires, within each group of plants and animals. Whenever possible, we carried out separate analyses for grassland and savanna. Burning did not significantly reduce species richness of any of the groups analyzed, but had a positive effect on richness of graminoids in grassland. When analyzed at the species level, abundance of most animal groups did not show consistent responses to fire, except for a decrease in some frog populations in grasslands. Forbs, graminoids and subshrubs increased in abundance after fire in grassland areas, though in savanna areas, abundance of forbs and subshrubs tended to decline after fire. Species composition changed little in response to fire as indicated by low levels of dissimilarity between burned and unburned areas. These results confirm the high resilience of Cerrado biota to fire, as expected for savanna ecosystems in general. Besides, we demonstrate here that the risk of biodiversity losses cannot justify the objections to the use of prescribed fire for conservation purposes in the Cerrado.

The Marine Natural Product Manzamine A Inhibits Cervical Cancer by Targeting the SIX1 Protein.

Natural products remain an important source of drug leads covering unique chemical space and providing significant therapeutic value for the control of cancer and infectious diseases resistant to current drugs. Here, we determined the antiproliferative activity of a natural product manzamine A (1) from an Indo-Pacific sponge following various in vitro cellular assays targeting cervical cancer (C33A, HeLa, SiHa, and CaSki). Our data demonstrated the antiproliferative effects of 1 at relatively low and non-cytotoxic concentrations (up to 4 μM). Mechanistic investigations confirmed that 1 blocked cell cycle progression in SiHa and CaSki cells at G1/S phase and regulated cell cycle-related genes, including restoration of p21 and p53 expression. In apoptotic assays, HeLa cells showed the highest sensitivity to 1 as compared to other cell types (C33A, SiHa, and CaSki). Interestingly, 1 decreased the levels of the oncoprotein SIX1, which is associated with oncogenesis in cervical cancer. To further investigate the structure–activity relationship among manzamine A (1) class with potential antiproliferative activity, molecular networking facilitated the efficient identification, dereplication, and assignment of structures from the manzamine class and revealed the significant potential in the design of optimized molecules for the treatment of cervical cancer. These data suggest that this sponge-derived natural product class warrants further attention regarding the design and development of novel manzamine analogues, which may be efficacious for preventive and therapeutic treatment of cancer. Additionally, this study reveals the significance of protecting fragile marine ecosystems from climate change-induced loss of species diversity.

DNA barcoding in some Belarusian insects

Due to a number of factors in the anthropogenic load on ecosystems, environmental changes, and competition between native and invasive species, the loss of species diversity has currently risen to an alarming scale. One of the prospective approaches to remedy the current state and halt the loss is the international project “Barcode of Life”. The report describes the results of molecular genetic research on the insect representatives of such orders as Coleoptera (beetles), Lepidoptera (butterflies), and Trichoptera (caddisflies) using the cytochrome c oxidase subunit 1 of the mitochondrial region (COI). We proposed a technique for the sampling of biological material to isolate DNA from the hind legs of individuals. The technique prevents removal of the individuals of the most valuable species collected on the territory of the Republic of Belarus from their habitats. The DNA sample collection of order representatives was investigated. For the subfamily Cetoniinae (flower chafer), significant differences in haplotypes among the representatives of the Belarusian and European parts of their areal were found. For Trichoptera, it was shown that the COI gene has high variability to differentiate species. It was also revealed that some species of caddisflies, which Belarusian researchers believe to be synonymous ones, have sequences with big differences according to the BoldSystem database. This fact should be explored in the future. So, our analysis allows considering the COI gene as a satisfactory marker for the species identification in the Belarusian insects’ taxa studied.

Mapping microhabitat thermal patterns in artificial breakwaters: Alteration of intertidal biodiversity by higher rock temperature.

Urbanization is altering community structure and functioning in marine ecosystems, but knowledge about the mechanisms driving loss of species diversity is still limited. Here, we examine rock thermal patterns in artificial breakwaters and test whether they have higher and spatially less variable rock temperature than natural adjacent habitats, which corresponds with lower biodiversity patterns. We estimated rock temperatures at mid‐high intertidal using infrared thermography during mid‐day in summer, in both artificial (Rip‐raps) and natural (boulder fields) habitats. We also conducted diurnal thermal surveys (every 4 hr) in four seasons at one study site. Concurrent sampling of air and seawater temperature, wind velocity, and topographic structure of habitats were considered to explore their influence on rock temperature. Rock temperature was in average 3.7°C higher in the artificial breakwater in two of the three study sites, while air temperature was about 1.5–4°C higher at this habitat at summer. Thermal patterns were more homogeneous across the artificial habitat. Lower species abundance and richness in the artificial breakwaters were associated with higher rock temperature. Mechanism underlying enhanced substrate temperature in the artificial structures seems related to their lower small‐scale spatial heterogeneity. Our study thus highlighted that higher rock temperature in artificial breakwaters can contribute to loss of biodiversity and that integrated artificial structures may alter coastal urban microclimates, a matter that should be considered in the spatial planning of urban coastal ecosystems.

The end-Guadalupian (259.8 Ma) biodiversity crisis: the sixth major mass extinction?

ABSTRACT The modern loss of species diversity has been labelled the ‘sixth extinction’ subsequent to the five major mass extinctions widely recognised in the Phanerozoic geologic record – the end-Ordovician (443.8 Ma), the Late Devonian (372.2 Ma), end-Permian (251.9 Ma), end-Triassic (201.4 Ma) and end-Cretaceous (66 Ma) events. Rankings in terms of numbers of genera suffering extinction, and especially in terms of ecological impact, however, put the end-Guadalupian (end-Capitanian) (259.8 Ma) extinction event in the same category with the other major mass extinctions. Thus, there were apparently six major Phanerozoic mass extinctions, and the current loss of species should perhaps be called the ‘seventh extinction’.

Soil chemistry, and not short-term (1-2 year) deer exclusion, explains understory plant occupancy in forests affected by acid deposition.

The loss of species diversity and plant community structure throughout the temperate deciduous forests of North America have often been attributed to overbrowsing by white-tailed deer (Odocoileus virginanus). Slow species recovery following removal from browsing, or reduction in deer density, has been termed a legacy effect of past deer herbivory. However, vegetation legacy effects have also coincided with changes to soil chemistry throughout the north-eastern USA. In this paper, we assess the viability of soil chemistry (i.e. pH, extractable nutrients and extractable metals) and other factors (topography, light, overstory basal area and location) as alternative explanations for a lack of vegetation recovery. We compared the relative effects of soil chemistry, site conditions and short-term (1-2 year) deer exclusion on single-species occupancy probabilities of 10 plant taxa common to oak-hickory forests in central Pennsylvania. We found detection for all modelled species was constant and high ( > 0.65), and occupancy probability of most taxa was best explained by at least one soil chemistry parameter. Specifically, ericaceous competing vegetation was more likely to occupy acidic (pH < 3.5), base cation-poor (K < 0.20 cmolc kg-1) sites, while deer-preferred plants were less likely to occur when soil manganese exceeded 0.1 cmolc kg-1. Short-term deer exclusion did not explain occupancy of any plant taxon, and site conditions were of nominal importance. This study demonstrates the importance of soil chemistry in shaping plant community composition in the north-central Appalachians, and suggests soil as an alternative, or additional, explanation for deer vegetation legacy effects. We suggest that the reliance on phyto-indicators of deer browsing effects may overestimate the effects of browsing if those species are also limited by unfavourable soil conditions. Future research should consider study designs that address the complexity of deer forest interactions, especially in areas with complex site-vegetation histories.

Decomposition time, chemical traits and climatic factors determine litter-mixing effects on decomposition in an alpine steppe ecosystem in Northern Tibet

In the context of rapid species diversity loss, whether and how species diversity affects litter decomposition in alpine ecosystems remain unclear. Here, we aimed to assess the impact of litter mixing on decomposition and the influencing factors of such litter-mixing effects (LMEs). We incubated the litter of four alpine steppe species in monocultures and all possible litter combinations and analysed the mass remaining over three years. Litter mixing showed more frequent antagonistic effects than synergistic effects in the early stage of the experiment; however, the LME might change from antagonistic to synergistic at the latter stage of incubation. The magnitude of the LMEs increased as decomposition progressed. The four-species mixture resulted in more antagonistic effects, while the magnitude of the non-additive effects showed no relationship with species richness. Litter chemical traits and climatic factors affected the direction and magnitude of the non-additive effects, but these influences were time-dependent. Additionally, the fast-decomposing and slow-decomposing litter species had negative and positive responses to the litter mixture, respectively. Our results demonstrate that the LME was determined by decomposition time, chemical traits and climatic factors and suggest that assessing the relative individual performances of the litter components in a mixture is an important way to examine the mechanisms underlying LMEs.

Exploring the power of Bayesian birth-death skyline models to detect mass extinction events from phylogenies with only extant taxa.

Mass extinction events (MEEs), defined as significant losses of species diversity in significantly short time periods, have attracted the attention of biologists because of their link to major environmental change. MEEs have traditionally been studied through the fossil record, but the development of birth‐death models has made it possible to detect their signature based on extant‐taxa phylogenies. Most birth‐death models consider MEEs as instantaneous events where a high proportion of species are simultaneously removed from the tree (“single pulse” approach), in contrast to the paleontological record, where MEEs have a time duration. Here, we explore the power of a Bayesian Birth‐Death Skyline (BDSKY) model to detect the signature of MEEs through changes in extinction rates under a “time‐slice” approach. In this approach, MEEs are time intervals where the extinction rate is greater than the speciation rate. Results showed BDSKY can detect and locate MEEs but that precision and accuracy depend on the phylogeny's size and MEE intensity. Comparisons of BDSKY with the single‐pulse Bayesian model, CoMET, showed a similar frequency of Type II error and neither model exhibited Type I error. However, while CoMET performed better in detecting and locating MEEs for smaller phylogenies, BDSKY showed higher accuracy in estimating extinction and speciation rates.

Functional diversity of different vegetation types does not respond homogeneously to change over time after conservation translocation from a rural landscape to an urbanized one

The anthropogenic impact on natural environments and the loss of species diversity along with changes in functional diversity call for effective steps to ensure habitat conservation. The functional diversity in particular has suffered in recent decades due to investment and land use changes. The translocation of whole turfs of certain vegetation plots prior to being destroyed is one possible solution for maintaining habitat functional diversity. In the presented paper, we analyse the functional changes in adaptive, regeneration and urbanity plant traits for meadow, heath and fen that were translocated from a rural site to a post-industrial site in a city. After five years of monitoring, we checked the changes in the functional diversity (FD) and community weighted means with the adoption of nine traits and Rao’s quadratic entropy for calculating the FD and the relative treatment effect (RTE) to evaluate the influence of time. We found that the overall FD of that trait set was not significantly changed. The FD of the seed dispersal type significantly increased. The means of autochoric, anemochoric and hemerochoric species decreased, and nautochoric and zoochoric species increased significantly, with respect to the frequency and abundance. The flowering season was shorter for meadows and heaths with earlier start and termination. The most important factors of the FD changes are probably linked to the microclimate of the urbanized area and the cessation of grazing. Our study demonstrated that translocation of vegetation plots from rural to urbanized environments can be a fairly effective measure in landscape shaping and in promoting biodiversity in urban ecosystems.

Vegetation changes in the Hasbruch forest nature reserve (NW Germany) depend on management and habitat type

AimsWe carried out vegetation studies in the ancient Hasbruch forest, which provided the unique conditions of unmanaged (UM) and managed (M) stands in two vegetation types Stellario-Carpinetum loniceretosum (POOR) and stachyetosum (RICH) stands in one closed forest allowing us to study (1) the changes in species composition and richness over 20 years considering the entire forest as well as (2) group-specific changes. LocationHasbruch forest in the lowlands of Lower Saxony, Germany. MethodsIn 2016 we resurveyed the vascular plant species composition of 79 semi-permanent plots analysed in 1996. General and group-specific trends as well as drivers of changes were analysed using DCA, PCA, LM, t-test, U test, ANOVA. ResultsTree and shrub layer coverage increased significantly in the entire forest. Herb layer species richness decreased significantly only in group RICH_UM. While the pH-value increased significantly in group POOR, it decreased significantly in group B. EIV F increased significantly in group POOR_M and decreased significantly in group RICH_UM. EIV L increased significantly in both of the managed groups, while it decreased significantly in group RICH_UM. An increase was found for EIV N in group POOR_M, whereas a decrease was found in group RICH_M. Strongly increasing species were Ilex aquifolium, Rubus fruticosus agg. and Hedera helix; strongly decreasing species Geum urbanum and Primula elatior. The change in species richness was positively affected by ΔpH and negatively affected by ΔT1cov in the entire forest. ConclusionsThe main drivers for changes in species richness and composition in the Hasbruch forest were light and water availability. The effects of the drivers strongly depended on the vegetation type. Changes in species composition were more pronounced in nutrient-rich forests than on nutrient-poor sites. In nutrient-rich forests, decreased groundwater influence led to decreased soil pH which especially affected typical woodland plants in a negative way. Management positively affected light-demanding species as well as some N-demanding species. Thus, unmanaged, nutrient-rich stands displayed the highest losses in species diversity. In the nutrient-poor stands, changes in species composition were not significantly related to changes in soil and management. However, increasing pH as well as increased Ellenberg L, F, and N values suggest a tendency towards eutrophication. This is possibly a consequence of N deposition and recovery from soil acidification.

Realistic loss of plant species diversity decreases soil quality in a Tibetan alpine meadow

With rapid changes in climate conditions and grazing regimes, a decline in soil quality has become a main challenge for sustainability of Tibetan rangeland. Increasing evidence highlights the significance of plant biomass, but few studies test the role of realistic loss of plant diversity in impacting soil quality. We hypothesized that loss of species diversity will decrease soil quality, not only through lost standing biomass (i.e., “mass effect”) but also directly via the loss of the “diversity effect”. Considering the realistic loss of species diversity following overgrazing, grazing exclusion and climate change, we experimentally removed grass, sedge and various forb species from a Tibetan alpine meadow to test this hypothesis. After target plant species had been removed for five years, we examined the effect of the species removal on the plant community and soil quality with Bayesian linear mixed effect models and inferred potentially causal linkages between plants and soil with a Bayesian network. Results showed (i) overall, plant species removal not only significantly decreased plant diversity and standing biomass but also decreased soil organic matter and nutrients; (ii) the standing biomass decreased more pronouncedly in response to the removal of sedge and grass species, but plant diversity and soil nutrients decreased more pronouncedly in response to the removal of various forb species; and (iii) the loss of species diversity rather than standing biomass was directly associated with the decline in the soil quality, especially a decrease in soil available P. In short, our results indicate that realistic loss of plant species diversity can decrease soil quality in a Tibetan alpine meadow through lost the “diversity effect”. The functional significance of plant species diversity in maintaining soil quality supports the expectation of local pastoralists that diverse plants, promoted by traditionally rotational grazing, can ensure the sustainability of alpine soil and Tibetan rangeland.

Mollusc species from the Pontocaspian region – an expert opinion list

Defining and recording the loss of species diversity is a daunting task, especially if identities of species under threat are not fully resolved. An example is the Pontocaspian biota. The mostly endemic invertebrate faunas that evolved in the Black Sea – Caspian Sea – Aral Sea region and live under variable salinity conditions are undergoing strong change, yet within several groups species boundaries are not well established. Collection efforts in the past decade have failed to produce living material of various species groups whose taxonomic status is unclear. This lack of data precludes an integrated taxonomic assessment to clarify species identities and estimate species richness of Pontocaspian biota combining morphological, ecological, genetic, and distribution data. In this paper, we present an expert-working list of Pontocaspian and invasive mollusc species associated to Pontocaspian habitats. This list is based on published and unpublished data on morphology, ecology, anatomy, and molecular biology. It allows us to (1) document Pontocaspian mollusc species, (2) make species richness estimates, and (3) identify and discuss taxonomic uncertainties. The endemic Pontocaspian mollusc species richness is estimated between 55 and 99 species, but there are several groups that may harbour cryptic species. Even though the conservation status of most of the species is not assessed or data deficient, our observations point to deterioration for many of the Pontocaspian species.

Effects of habitat fragmentation on the functional diversity of insects in Thousand Island Lake, China

AbstractDue to habitat fragmentation, the loss of species diversity has been extensively studied. On the contrary, the effects of habitat fragmentation on functional diversity is still poorly understood. In the Thousand Island Lake, we conducted studies of insect functional diversity on a set of 29 isolated islands. We used 10 functional diversity indices from three aspects (functional richness, functional evenness and functional divergence) to respectively describe functional diversity of insects on sample islands.We found the following results: (i) The functional indices selected could reflect the functional diversity of sample islands and it is further proved that in general, three components of functional diversity were independent of each other; (ii) Sample islands could be divided into two categories, island JSD and the remaining islands; (iii) Functional richness increased with island area and shape index, but had no significant correlation with isolation. Likewise, both functional evenness and functional divergence had no significant correlation with island attributes. The conclusion to emphasize from our research is that: (i) habitat fragmentation reduced the biological functional diversity to some extent, further demonstrating the importance of habitat continuity in biodiversity protection; and (ii) for functional diversity protection of insects in a fragmented landscape, an island which has high approximate shape index values of at least hundred hectare magnitude order has a critical promoting effect.

Trends of phanerophyte encroacher species along an aridity gradient on Kalahari sands, central Namibia

Abstract Poor rangeland management, especially overstocking and under-burning coupled with climate change on southern African savannas, have brought about a serious ecological problem of bush encroachment. Bush encroachment leads to many ecological implications such as extirpation or extinction of plant species and a colonisation by opportunistic species leading to unwanted changes in plant species composition, structure and loss of species diversity. Furthermore, bush encroachment has a negative impact on the country’s progress in terms of conservation efforts, economic stability and livelihood. Namibian livestock ranchers forego an estimated N$ 700 million loss yearly linked to bush encroachment. Studies focusing on particular bush encroacher species enable the devise of ecologically sound management strategies by land manager, farmers and scientists for the prevention and control of bush encroachment. Therefore, this study was undertaken to determine the main encroacher species and their relationship to the environmental factors along an aridity gradient on Kalahari sands in central Namibia. Results disclosed that Acacia erioloba E.Mey., Acacia mellifera (Vahl) Benth. ssp. dentines (Burch.) Brenan, Combretum collinum Fresen., Terminalia sericea Burch. Ex DC., Grewia spp., Bauhinia petersiana Bolle ssp. macrantha (Oliv.) Brummitt &amp; J.H. Ross were the main encroacher species, and mean annual rainfall was the main environmental factor influencing their distribution. Nanophanerophyte from different encroacher species were recorded mainly from 400 mm to 500 mm mean annual rainfall, mesophanerophyte recorded from 280 mm to 450 mm, while microphanerophyte were widely distributed over the rainfall gradient. Bush encroachment was recorded at 440 mm mainly due to the poor rangeland management. Information from this study should be used as a baseline for conservation and restoration attempts towards savanna rangelands.