Habitat diversity enhances ant diversity in a naturally heterogeneous Brazilian landscape

Understanding the factors that drive species richness and composition at multiple scales is of crucial importance for conservation. Here we evaluated how habitat heterogeneity—at the local and landscape scales—affects the diversity of ants in the Brazilian Cerrado. The Cerrado is a biodiversity hotspot that is characterized as a mosaic of habitats, including savannas of variable structure (the dominant vegetation), grasslands, and forests. We sampled ground-dwelling ants in four habitats, representing a gradient of increasing tree cover and decreasing grass cover. Twelve sites, distributed along two degrees of latitude, were sampled. Our sampling revealed a highly diverse and patchily distributed fauna comprising 150 species (from 44 genera), of which nearly 40% were found in only one site. On average, we found fewer species in the least structurally complex habitat. However, there was relatively little variation in species density among the remaining habitats despite strong differences in vegetation structure among them. Ant species composition varied markedly among sites and such differences were related to variations in vegetation structure but not to inter-site distances (latitude). Similar results were obtained when overall ant species richness (γ diversity) was partitioned additively into three components: α₁ (diversity within sampling sites), β₁ (diversity among sites within the same habitat type), and β₂ (diversity among sites from different habitats). The β₂ component contributed much more to γ diversity than did the remaining diversity components, indicating that conservation of the Cerrado ant fauna depends on the maintenance of habitat diversity.     

Interaction network of vascular epiphytes and trees in a subtropical forest

The commensalistic interaction between vascular epiphytes and host trees is a type of biotic interaction that has been recently analysed with a network approach. This approach is useful to describe the network structure with metrics such as nestedness, specialization and interaction evenness, which can be compared with other vascular epiphyte-host tree networks from different forests of the world. However, in several cases these comparisons showed different and inconsistent patterns between these networks, and their possible ecological and evolutionary determinants have been scarcely studied. In this study, the interactions between vascular epiphytes and host trees of a subtropical forest of sierra de San Javier (Tucuman, Argentina) were analysed with a network approach. We calculated metrics to characterize the network and we analysed factors such as the abundance of species, tree size, tree bark texture, and tree wood density in order to predict interaction frequencies and network structure. The interaction network analysed exhibited a nested structure, an even distribution of interactions, and low specialization, properties shared with other obligated vascular epiphyte-host tree networks with a different assemblage structure. Interaction frequencies were predicted by the abundance of species, tree size and tree bark texture. Species abundance and tree size also predicted nestedness. Abundance indicated that abundant species interact more frequently; and tree size was an important predictor, since larger-diameter trees hosted more vascular epiphyte species than small-diameter trees. This is one of the first studies analyzing interactions between vascular epiphytes and host trees using a network approach in a subtropical forest, and taking the whole vascular epiphyte assemblage of the sampled community into account.     

Patterns and drivers of stream benthic macroinvertebrate beta diversity in an agricultural landscape

Hydrobiologia - Laguna del Sauce, one of the main drinking water sources in Uruguay, is an eutrophic shallow lake with high temporal variation of inorganic turbidity caused by extreme wind events....     

Web building flexibility of an orb‐web spider in a heterogeneous agricultural landscape

Intensification of land‐use in agricultural landscapes is responsible for a decline of biodiversity which provide important ecosystem services like pest‐control. Changes in landscape composition may also induce behavioural changes of predators in response to variation in the biotic or abiotic environment. By controlling for environmentally confounding factors, we here demonstrate that the orb web spider Araneus diadematus alters its web building behaviour in response to changes in the composition of agricultural landscapes. Thereby, the species increases its foraging efficiency (i.e. investments in silk and web asymmetry) with an increase of agricultural land‐use at intermediate spatial scales. This intensification is also related to a decrease in the abundance of larger prey. A negative effect of landscape properties at similar spatial scales on spider fitness was recorded when controlling for relative investments in capture thread length. This study consequently documents the web building flexibility in response to changes in landscape composition, possibly due to changes in prey availability.     

Changes in carabid beetle diversity within a fragmented agricultural landscape

The distribution of carabid and cicindelid (Coleoptera: Carabidae) beetles in five distinct habitats (riparian, mature orchard, pine windbreak, young orchard, natural veld), within Tambuti Citrus Estate (Swaziland) was examined by pitfall trapping over 18 months. Habitats with high vegetation and litter cover had the highest species diversity and larger specimens, e.g. riparian border and pine windbreak, while the lowest diversity was observed in intensively managed mature citrus orchards. While species such as Tefflus delagorguei Guérin occurred in all the habitats sampled, certain species illustrated habitat specificity; e.g. Dromica ambitiosa Péringuey was observed only in the pine windbreaks while Haplotrachelus sp. Chaudoir occurred mainly in the vegetated riparian and natural veld habitats. Four unidentified carabid beetles were exclusive to the riparian border habitat. This habitat was the only one with a distinct assemblage of species in the agricultural mosaic studied. Multivariate analyses were used to assess the role of soil and environmental variables in relation to the ground beetle diversity within the agricultural mosaic studied.     

Lizard diversity and agricultural disturbance in a Caribbean forest landscape

Understanding the impact of agriculture on biodiversity is critical for effective conservation management. Our goal was to determine the impact of agricultural disturbance on the lizard fauna of Los Haitises National Park and the surrounding region in the Dominican Republic. This region has a history of extensive agricultural disturbance followed by abrupt abandonment. Abundance and diversity were surveyed in six habitats: relatively undisturbed hilltop (mogote), four habitats disturbed by agriculture (pasture, oil palm plantation, cacao plantation, conuco or home garden), and one forested habitat. Three of these habitats (pasture, cacao plantation, conuco) were also examined at different stages of activity or abandonment. Glue-trap grids were used to sample each habitat. In general, species richness was lower in more heavily or recently disturbed habitats. Richness was lowest in active agricultural habitats where only 54% of the region's lizard species were detected. Notably, agricultural systems differed considerably in their ability to support a diverse lizard assemblage. Abandoned agricultural habitats had slightly higher richness than their active counterparts, but still contained only 69% of the region's species. By contrast, nearly every native species, including several never observed in agriculturally disturbed habitats, were detected on the undisturbed hilltops (mogotes). These mogotes may have served as refugees for species that could not tolerate disturbance when the region was being heavily exploited for agriculture. Overall, our results suggest that the continued protection of the park, and its mogotes in particular, will be required to maintain the region's lizard diversity.     

Local diversity of arable weeds increases with landscape complexity

Patterns of plant diversity are often related to local site conditions and to competitive interactions, but landscape context may also be important for local plant species richness. This is shown here by analysing the relationship between landscape complexity and local species richness of arable weeds in wheat fields. The fields were located in 18 landscapes characterised by a gradient in landscape complexity from structurally complex to structurally simple (39–94% arable land). We quantified local site conditions, field management intensity and landscape characteristics, and used principle component analyses to ordinate the environmental variables. The percentage of arable land was negatively correlated with perimeter–area ratio, habitat-type diversity and topographical heterogeneity, but landscape characteristics did not correlate with local site conditions and field management intensity. The number of plant species was mainly related to landscape characteristics and to a lesser extent to field management intensity (nitrogen fertilisation), whereas local soil characteristics did not contribute to the explanation of arable weed richness. In a geographic scale analysis using circular landscape sectors ranging from 1 km up to 5 km diameter, the predictive power of landscape complexity for local plant species richness was strongest at 2 km indicating a scale-dependent relationship between landscape context and plant species richness. Our results support the hypothesis that local plant species richness in arable fields is greatly influenced by processes operating at the landscape scale. Seed rain from ruderal source habitats and disturbed edges may be the most important underlying process.     

黄淮平原农业景观鸟类多样性及生境差异

农业景观中的鸟类多样性对生态系统功能和服务的形成与维持具有重要作用。黄淮平原区是我国最重要的农业景观区之一,为探讨区域内农业景观中鸟类多样性特征和不同生境间的差异,在研究区农业景观不同生境中布设样点,调查繁殖期鸟类多样性特征。结果显示:(1)共记录到32科、49属、66种的10044只个体,但优势科属明显;(2)物种丰富度、多样性和均匀度均表现出在沟渠、湖泊生境中较高,农田和村庄生境中相对较低,但物种多度呈现出村庄生境中最高,其次是沟渠和农田生境,湖泊生境中最低;(3)在区系分布上,各生境中均以广布种为主,生态类群上,鸣禽在各生境中均占绝对优势,涉禽和游禽主要分布在沟渠和湖泊生境中,从居留型来看,留鸟是各生境中的主导类群,候鸟、旅鸟和迷鸟比例很低;(4)鸟类群落异质性分析显示,各生境间的相似性总体上较高,表明区域内农业景观中鸟类组成具有较高的重叠性。研究显示农业景观中湖泊和沟渠的存在能有效的提高区域鸟类的丰富度和多样性,而沟渠的存在能有效的提高鸟类个体多度,农田和村庄有助于特定类群多度的增加,因此在未来的区域持续农业景观的构建中一方面要重视自然、半自然非农生境的作用,另一方面也不能忽视不同生物类群对景观异质性响应和对生境特征需求的差异。     

Factors influencing herpetofauna abundance and diversity in a tropical agricultural landscape mosaic

Agricultural intensification and the associated factors, including land transformation, are among the major global threats affecting biodiversity especially herpetofauna. However, little information is available about how different factors shape herpetofauna species assemblages in agricultural landscape at different spatial scales from patch (125 – 250m) to the landscape (500 – 1000m). We assessed the diversity of amphibians and reptiles in areas under low and high degrees of agricultural intensification and explored different factors regulating diversity at different spatial scales using four sampling methods. Diversity and abundance of amphibians varied significantly between the two zones, but not for reptiles. Agricultural intensification index (AII), calculated based on agrochemical use and area under agriculture at 250m scale, seemed to affect amphibians both at patch as well as at 500m and 1000m landscape scales. The AII influenced reptilian diversity only at patch and 500m scales. Vicinity of natural forest had a stronger influence on reptilian abundance. Seminatural vegetation impacted herpetofauna diversities at larger spatial scales. The extent of water bodies influenced the reptilian abundance at 250m patch scale and amphibian abundance both at 250m and 1000m scale. Fallow lands affected only reptilian diversity at all spatial scales. Plantation affected amphibian at all scales but reptiles only at the landscape scale. Habitat heterogeneity regulated only amphibian diversity. These results highlight the fact that different patch and landscape-scale factors regulate the diversity of reptiles and amphibians differentially. Such scale-specific information will crucially inform future conservation action for the herpetofauna in the agricultural landscape.     

A foliar endophyte increases the diversity of phosphorus-solubilizing rhizospheric fungi and mycorrhizal colonization in the wild grass Bromus auleticus

Asexual Epichloë endophytes establish mutualistic symbioses with grasses, improve fitness of their hosts and modify the surrounding environment. To test the hypothesis that this symbiotic association increases the abundance and diversity of phosphate-solubilizing fungi (PSF), a pot experiment was conducted combining two endophytic statuses: Epichloë-infected (E+) and non-infected (E−) Bromus auleticus plants, and two soil types collected from agricultural (A) and non-agricultural (NA) fields. Soil fungi were isolated at the beginning of the experiment and 12 months after the introduction of B. auleticus, and tested for their inorganic P (Pi)-solubilizing capability. Arbuscular mycorrhizal colonization in B. auleticus roots of E+ and E− plants was also analyzed. PSF abundance was affected by the endophytic status and by the type of soil; the highest value was detected in the E−NA treatment, followed by the E+A treatment. PSF diversity was higher in NA than in A soils and higher in soils treated with E+ than in those treated with E−. Arbuscular mycorrhizal fungi colonization was higher in E+ plants. We hypothesize that the positive association between Epichloë endophytes and mycorrhizal fungi with an increase in the PSF diversity would generate an increase in the phosphorus (P) available to plants.     

Scale dependent drivers of wild bee diversity in tropical heterogeneous agricultural landscapes

Factors associated with agricultural intensification, for example, loss of seminatural vegetation and pesticide use has been shown to adversely affect the bee community. These factors may impact the bee community differently at different landscape scales. The scale dependency is expected to be more pronounced in heterogeneous landscapes. However, the scale‐dependent response of the bee community to drivers of its decline is relatively understudied, especially in the tropics where the agricultural landscape is often heterogeneous. This study looked at effects of agricultural intensification on bee diversity at patch and landscape scales in a tropical agricultural landscape. Wild bees were sampled using 12 permanent pan trap stations. Patch and landscape characteristics were measured within a 100 m (patch scale) and a 500 m (landscape scale) radius of pan trap stations. Information on pesticide input was obtained from farmer surveys. Data on vegetation cover, productivity, and percentage of agricultural and fallow land (FL) were collected using satellite imagery. Intensive areas in a bee‐site network were less specialized in terms of resources to attract rare bee species while the less intensive areas, which supported more rare species, were more vulnerable to disturbance. A combination of patch quality and diversity as well as pesticide use regulates species diversity at the landscape scale (500 m), whereas pesticide quantity drove diversity at the patch scale (100 m). At the landscape scale, specialization of each site in terms of resources for bees increased with increasing patch diversity and FL while at the patch scale specialization declined with increased pesticide use. Bee functional groups responded differentially to landscape characteristics as well as pesticide use. Wood nesting bees were negatively affected by the number of pesticides used but other bee functional groups were not sensitive to pesticides. Synthesis and Applications: Different factors affect wild bee diversity at the scale of landscape and patch in heterogeneous tropical agricultural systems. The differential response of bee functional groups to agricultural intensification underpins the need for guild‐specific management strategies for wild bee conservation. Less intensively farmed areas support more rare species and are vulnerable to disturbance; consequently, these areas should be prioritized for conservation to maintain heterogeneity in the landscape. It is important to conserve and restore seminatural habitats to maintain complexity in the landscapes through participatory processes and to regulate synthetic chemical pesticides in farm operations to conserve the species and functional diversity of wild bees.     

Effects of newly planted hedges on ground-beetle diversity (Coleoptera, Carabidae) in an agricultural landscape

The diversity of ground-beetle communities (Coleoptera. Carabidae) was studied to assess the short-term impact of new hedges planted in an intensive agro-ecosystem. Hedges represent a new and undisturbed habitat for those polyphagous predators and may provide increased prey availability. Carabids were sampled with pitfall traps in a hedge and an adjacent cultivated field during the whole activity period of these insects to assess the effect of distance from the hedge on species diversity. Fenced pitfall traps were also used to estimate absolute population densities. Several diversity indices were calculated at various sampling levels (total area, distance treatment, trap). Kendall's coefficient of rank correlation between communities at adjacent distances showed that the greatest changes in species relative abundances occurred close to the hedge. Indices of species richness, dominance concentration, equitability and Fisher's a all indicated a significant decrease in species diversity with increasing distance from the hedge. These trends are explained by two complementary factors. First, the number of species decreased significantly with distance from the centre of the hedge. Second, the various species had different spatial patterns of total capture and absolute density. Four groups of species can thus be distinguished: species restricted to the hedge, species preferring the hedge, species preferring the crop, and species unaffected by the hedge. The respective roles of small-scale abiotic changes in habitat structure and differences in prey availability are discussed.     

Establishment of native perennial shrubs in an agricultural landscape

Abstract Native vegetation has been destroyed or dramatically modified throughout agricultural regions of southern Australia. Extensive restoration of native perennial vegetation is likely to be crucial in these areas for the persistence of native plant and animal species, to ameliorate dryland salinity and soil degradation, and to maintain long‐term agricultural production. The long‐term resilience of these systems will be dependent on the ability of key functional taxa, such as perennial shrubs, to recruit and persist. In this study, we examine the factors limiting establishment of two perennial shrubs in formerly cropped land, the rare Maireana rohrlachii and the common Maireana decalvans. Field and laboratory observations suggest that establishment of both species is not limited by life‐history traits following cultivation. Both species established and persisted under varying levels of plant competition. Similarities existed between species in their initial germination rates. Weak differences were found between species in the growth and survival rates under different levels of competition. The main difference between the two species was in the decline of germinability of fruits with increasing fruit age. From the data, it is difficult to determine what factors limit the establishment of perennial shrubs in these landscapes. The main hypothesis that can be advanced is that establishment of shrub species appears to be limited by propagule availability and this is likely to be a function of past and present grazing management rather than cultivation per se. Further investigation of these land‐use practices may give greater insight into the factors affecting the establishment of this life form across these landscapes.     

Long-term responses in population dynamics and diversity of small mammals in riparian and upland habitats within an agricultural landscape

Riparian zones in agricultural landscapes provide linear non-crop habitats for a variety of plant and mammal species, and hence are an important component of biodiversity. To date, variable responses of abundance, species richness, and species diversity of small mammals have been recorded in riparian and upland habitats. To address this variability, we provide a detailed analysis of seasonal changes in abundance and diversity of terrestrial small-mammal communities over a 7-year period within an agricultural landscape in south-central British Columbia, Canada. We tested the hypotheses (H) that abundance, species richness, and species diversity of communities of small mammals (H₁), and demographic parameters of reproduction, recruitment, and survival of the major species: deer mouse (Peromyscus maniculatus) and montane vole (Microtus montanus) (H₂), would be higher in riparian than upland habitats. Mean total abundance of small mammals was higher in summer and winter, and species richness higher in summer, in riparian than hedgerow habitats. Winter population data supported the total and species abundance patterns for small mammals, but species richness was similar, and diversity lower, in riparian than hedgerow sites during winter periods. Deer mice were the dominant species in terms of abundance and reproductive output for pregnancies and recruitment, but not survival, in riparian sites. Montane voles were similar in abundance and demographic parameters in the two habitats. House mice (Mus musculus) preferred hedgerows and wandering shrews (Sorex vagrans) riparian sites. Demographic parameters for deer mice and montane voles indicated that both riparian and hedgerow sites were “source” rather than “sink” habitats, and likely contribute to maintenance of mammal diversity in agricultural landscapes.     

黄淮平原农业景观不同生境鸟类多样性特征及年际动态

鸟类是地球生物多样性中的重要组成部分,在生态系统功能和服务中发挥着重要作用,是生态环境变化的重要指示物种。农业景观中的食虫鸟类提供了重要的虫害控制服务。当前,农业景观中鸟类多样性丧失加剧,为探讨鸟类多样性在各生境以及年际间的变化,以黄淮平原为研究区,在河流、湖泊、农田、村庄等生境中共设置20个样点。于2016-2019年连续4年在繁殖期采用样线法对鸟类进行多样性调查。调查结果显示：（1）共发现22922只个体,分属14目,38科,53属。从区系分布来看,各生境各年间均以广布种为主;从生态类群来看,鸣禽占绝对优势;从居留型来看,留鸟所占比例最高。（2）在食性组成上,从物种丰富度看,食虫鸟类有57种,约占总物种数的77%;从个体数来看,杂食性鸟类占比超52%。（3）物种丰富度、多样性和均匀度指数最高值均出现在湖泊或河流生境中。（4）鸟类群落相似性分析显示,各生境间鸟类群落均为中等相似程度;鸟类物种丰富度波动幅度在农田和村庄中呈逐年上升趋势。（5）物种多样性加性拆分分析显示,在生境尺度上,局地的α多样性是生物多样性的最重要组成,而从整个研究区来看,生境间的差异则更为重要。造成鸟类多样性时空差异的原因复杂多样,而生境异质性的增加和水域的存在对提高鸟类多样性是具有积极作用的。调查中超过77%的物种和40%的个体均为食虫鸟类,应当充分重视鸟类为区域农业景观提供的虫害控制服务。本研究可为区域鸟类多样性保护及鸟类提供的生态系统服务的提升管理提供理论基础和科学依据。     

Species Richness of Nonvolant Small Mammals Along Elevational Gradients in Northwestern Argentina

The Nevados del Aconquija (5500 m) and Cumbres Calchaquíes (4600 m) are isolated mountain ranges that contain at least three physiognomic units in their eastern slopes: Neotropical rainforests, Andean grasslands and High Andean Steppes. Despite phytogeographical similarities, the two ranges differ in the amount and spatial distribution of rainfall over the elevation gradient. We studied terrestrial small mammals by direct trapping in two altitudinal transects on the eastern slope of the two mountain ranges. We recorded the changes in richness and species composition, as well as the relationships between species and microhabitats at each altitudinal level. The results show a similar structure of the small mammal assemblage in the two ranges. The largest differences, in terms of species composition, were registered at lower elevation forests, and faunal affinities increased with elevation to the point of finding identical species composition at the top of the mountains. Species richness showed a clear curvilinear pattern with a peak at the upper limit of the forests. Our findings suggest that total rainfall has an important influence on the composition and abundance of small mammal species but apparently not on the species richness along the elevation gradient. The highest values of species richness were observed at the sites where a contact between two different physiognomic units exists. These results indicate that habitat heterogeneity plays an important role in allowing the juxtaposition of small terrestrial mammal assemblages of the highlands and lowlands at a given point, contributing significantly to the considerable diversity of species observed in intermediate altitudinal sites.
     

Gravel pits support waterbird diversity in an urban landscape

Few studies exist documenting changes in rotifer communities over long time intervals. Here, we explore seasonal and long-term variation in rotifer communities in four Polish lakes sampled in 1976 and again in 1997. Rarefied, asymptotic species richness did not differ significantly across study years, although values in 1997 tended to be higher. Simpson’s and Shannon–Wiener diversity measures provided inconsistent temporal results, with only the former indicating significantly higher richness in 1997. Sorensen’s coefficient of community similarity was as high among lakes in 1976 (0.81) and in 1997 (0.76) as within lakes across the 21-year span (0.77). Nonlinear redundancy analysis of species’ abundances revealed large, consistent seasonal changes across lakes, smaller consistent shifts between sampling periods, and small differences between lakes. Collectively, these metrics indicate that species composition was relatively stable among lakes within years and within lakes between years, while species’ abundance patterns were far more variable and most affected by season. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users. Handling editor: S. I. Dodson