Ant Species Richness Research Articles

DIVERSITY AND FUNCTIONS OF ANTS (HYMENOPTERA: FORMICIDAE) IN BANGABANDHU SHEIKH MUJIBUR RAHMAN AGRICULTURAL UNIVERSITY CAMPUS OF BANGLADESH

Ants play a crucial role as ecosystem engineers and natural enemies of insect pests in different forests and agroecosystems. Bangladesh’s varied agroecosystem harbors a diverse ant community, it can be utilized to track recent changes to the agricultural environment. However, it’s utilization is deemed due to insufficient taxonomic checklist of ant fauna and their diversity pattern in various ecosystems in Bangladesh. This research aimed to measure the taxonomic and functional diversity of ants in an agroecosystem. Sampling was done by time-unit sampling (TUS) during March- April 2021 in different cropland habitats in Bangabandhu Sheikh Mujibur Rahman Agricultural University (BSMRAU) campus. A total of 172 individuals of 20 genera under 5 subfamilies were identified, of which Myrmicinae was the richest subfamily with 9 genera, while Camponotus is the most dominant genus in the ecosystem. Four habitats from BSMRAU campus significantly contributed on ant species richness and diversity matrix as revealed through Principal component analysis (PCA). The functional diversity of identified ant genera was explained using the results retrieved from Shannon Diversity Index, Species Evenness index and Effective number of species (ENS). The Shannon-Wiener diversity index of Field pathway (2.5202) is highest, followed by Entomology field (2.38086), agroforestry field (1.37315) and lowest in rice field (0.16794). Field pathway had the highest value due to comprising several types of vegetation alongside and non-ploughed soil. Rice field has only rice crops that were grown in a wetland; hence, water causes the lowest value. The evenness index (>0.75) implies the probability of stable communities in all the tested habitats except in rice field (0.242), which indicates a depressed community structure and is strengthened by the ENS value as 12.4, 10.8, 3.9, and 1.18 in the field pathway, in entomology field, agroforestry field, and rice field, respectively. The findings generated a comprehensive ant checklist and diversity indices with indicator species to measure the land type transformation and restoration in the agroecosystem of Bangladesh for future research.

Diversity and Distribution of Forest Ants (Hymenoptera: Formicidae) in Nepal: Implications for Sustainable Forest Management.

Simple SummaryThere is little information available about the species diversity and distribution patterns of Nepalese ants, as well as their importance in maintaining forest health. A survey of forest ants was conducted in Nepal to learn about their diversity, distribution, and role in forest management. Ants were collected using vegetation beating, sweeping, and hand collection methods in eastern, central, and western Nepal. Seventy ant species from thirty-six genera and six subfamilies were recorded in the study. The research also discovered five genera and nine species new for the country, as well as eight tramp species, four of which are major ecological, agricultural, and/or household pests. The study discovered that western Nepal and the Siwalik region have a relatively high ant diversity. Ant diversity was found to decrease with increasing elevation. The assessment of ant diversity using multiple sampling methods that cover all seasons and forest types may be useful in obtaining complete ant diversity data. Early intervention through sustainable forest management initiatives would aid in preventing invasive ant incursions in the forests of Nepal.The information available on the diversity of ant species and their distribution and interaction with forest health in Nepal remains limited. As part of a nationwide project on forest health, we conducted inventories to assess the diversity and distribution of forest ants and their role in forest management in Nepal. Ants were collected from 187 plots of 10 m × 10 m size along the north–south belt transects in eastern, central, and western Nepal. We used vegetation beating, sweeping, and hand collection methods in selected forest types. In each transect, we designed six plots in each major forest type (Sal, Schima–Castanopsis, and broadleaf mixed forests) and three plots each in deodar, Alnus, riverine, and Cryptomeria forests. We recorded 70 ant species from 36 genera and six subfamilies. This includes five genera and nine species new for the country, as well as eight tramp species, four of which are major ecological, agricultural, and/or household pests. Our study indicates that forest ant species richness is high in western Nepal and the Siwaliks, and it decreases as elevation increases. The high diversity of ant species in the forests of Nepal needs to be assessed with further exploration using multiple sampling methods covering all seasons and forest types. Ants can be useful indicators for ecosystem management and human impacts on forests. Reports of invasive ants in Nepalese forests indicate the relevance of urgent interventions through sustainable forest management initiatives to prevent future incursions.

Ants of the Forest and Dune Habitats of an Atlantic Coastal Barrier Island

We investigated ant species richness and abundance of the maritime forest and dune habitats of Assateague Island, a barrier island off the coasts of Maryland and Virginia. We paired 5 transects of 100 m in forest habitats with 5 transects in dune and grassland habitats, with pitfall traps set every 10 m along each transect. During a 5-month period (May–September), we collected 26 species of ants, including 9 that had not been previously recorded on the island and 2 that had never been recorded east of Maryland's Chesapeake Bay. Forest habitats had a significantly higher species richness than the dunes, with 24 and 14 species collected, respectively. Our research provides baseline data on ant species richness for this temperate barrier island using pitfall-collection methods. We provide evidence for forest habitats supporting higher species richness and make suggestions for future research.

Assessing the efficacy of higher‐taxon approach for ant species surveys to improve biodiversity inventories

AbstractUnderstanding the distribution of species is essential for the conservation and management of biodiversity. But the availability of this kind of information is still scarce for the most diverse regions. The higher‐taxon approach (i.e. use of coarser taxonomic levels to represent species) as an easier and efficient method in representing species patterns can be one way to overcome these constraints. However, there is a general lack of information about the taxonomic stability of surrogate taxa across space and time. We investigated the predictive power and stability of taxonomic identification at the genus level as a predictor of ant species (Hymenoptera: Formicidae) distribution throughout ~1000 km along the Amazon Basin, using taxonomy over the past 120 years. Using intervals of 10 years, from 1900 to 2020 we generated a genus and species matrix based on actual data from our sampling sites for each decade over a total of 120 years. We tested the predictive power of genera as a surrogate of species for approximating species‐level richness, composition and distribution‐based measures along topographic gradients at local (within site) and regional (between sites) scales. We detected a strong correlation between genera and ant species richness in the current database. There was also high congruence between genera and ant species composition over the time period studied. Genera were also efficient at detecting patterns of species distribution along topographic gradients. Despite changes in ant taxonomy over the past 120 years, our data indicate that such revisions did not affect the ability of ant genera to predict general patterns of ant species in our study area within the Amazon Basin. This reinforces the potential of genera to serve as surrogates for ant species elsewhere, which may significantly decrease the cost of surveying ants in environmental monitoring programs because of the time saved from identifying collected specimens to genus rather than species level.

Local coexistence of native and invasive ant species is associated with micro-spatial shifts in foraging activity

Invasive species often displace native species by outcompeting them. Yet, some native species can persist even in heavily invaded areas. The mechanisms mediating this local coexistence are still unclear. Fine-scale microclimatic heterogeneity could promote the local coexistence of native and invasive animal competitors. We tested if native ant species could coexist with a recent ant invader, Tapinoma magnum, by shifting their foraging activity in time or space to different microclimatic conditions. We compared the foraging activity of native epigeic ant species among invaded and uninvaded sites. We collected ants at baits in green spaces on the north, east, south and west sides of buildings in the morning, at noon and in the afternoon to test if native species foraged under different microclimatic conditions in invaded sites. Invaded sites had lower ant species richness, diversity, and relative abundance. The native black garden ant Lasius niger – one of the most widespread Palearctic ant species – persisted at high densities in invaded areas but foraged less on the east side of buildings and more on the west side. Microclimatic heterogeneity might promote native and invasive species coexistence by allowing some native species to shift their foraging behaviour to locally avoid or outcompete invasive competitors. Better understanding how fine-scale micro-environmental heterogeneity affects native species’ persistence in invaded areas could help to predict and locally mitigate the negative impacts of biological invasions.

Passive restoration of subtropical grasslands leads to incomplete recovery of ant communities in early successional stages

Understanding how land use and management practices affect biodiversity is essential for developing effective restoration and conservation strategies. Here, we used ant communities to evaluate the effects of historical land uses (former agriculture or tree plantation) and current management (grazing, burning, mowing, and fertilizing) in subtropical grasslands. We also examined how ant species richness and composition are affected through changes in resource diversity and habitat structure. We classified 80 study sites in southern Brazil into two groups: permanent and secondary grasslands. Permanent grasslands presented high, medium or low management intensities that had never been under other land use. Secondary grasslands are former grasslands that were used for agriculture or pine plantations in the past, followed by passive restoration. We sampled ant communities with D-Vac suction in three multiplots per site in 2013–2015. We found that secondary grasslands had lower ant species diversity and different community composition than permanent grasslands. Ant diversity did not differ among permanent grasslands, but composition was markedly different, especially when comparing medium and high management intensities with low. Additionally, ant richness in secondary grasslands was mainly mediated by a decreased resource diversity (i.e., plant species richness) and grass cover, while burning and mowing management increased ant richness by increasing resource diversity. Our results indicate that passive recovery of grasslands in early successional stages after other land uses leads to incomplete recovery of ant communities, as important resource and structure-related drivers of ant species remain altered. In contrast, traditional management practices promote ant diversity.

Functional composition of ant assemblages in habitat islands is driven by habitat factors and landscape composition

Fragmented natural habitats within human-transformed landscapes play a key role in preserving biodiversity. Ants as keystone species are essential elements of terrestrial ecosystems; thus, it is important to understand the factors influencing their presence. In a large-scale multi-site study, we surveyed ant assemblages using sweep netting and D-vac sampling on 158 ancient burial mounds preserving grassland habitats in agricultural landscapes in East-Hungary. We asked the following questions: (1) How do habitat factors and landscape composition affect species richness and functional diversity of ants? (2) Which ant traits are affected by habitat factors and landscape composition? Despite their small sizes, mounds as permanent and relatively undisturbed landscape elements could provide safe havens for diverse ant assemblages even in transformed agricultural landscapes. The complex habitat structure of wooded mounds supported high species and functional diversity of ant assemblages. Ant species on wooded mounds had small or medium-sized colonies, enabling the co-existence of more species. The effect of landscape composition on ant assemblages was mediated by habitat factors: steep slopes buffered the negative effect of the cropland matrix and enabled higher ant diversity.

Tropical land use drives endemic versus exotic ant communities in a global biodiversity hotspot

Understanding how land-use change affects biodiversity is a fundamental step to develop effective conservation strategies in human-modified tropical landscapes. Here, we analyzed how land-use change through tropical small-scale agriculture affects endemic, exotic, and non-endemic native ant communities, focusing on vanilla landscapes in north-eastern Madagascar, a global biodiversity hotspot. First, we compared ant species richness and species composition across seven land-use types: old-growth forest, forest fragment, forest-derived vanilla agroforest, fallow-derived vanilla agroforest, woody fallow, herbaceous fallow, and rice paddy. Second, we assessed how environmental factors drive ant species richness in the agricultural matrix to identify management options that promote endemic and non-endemic native while controlling exotic ant species. We found that old-growth forest, forest fragment, and forest-derived vanilla agroforest supported the highest endemic ant species richness. Exotic ant species richness, by contrast, was lowest in old-growth forest but highest in herbaceous fallows, woody fallows, and rice paddy. Rice paddy had the lowest non-endemic native ant species richness. Ant species composition differed among land-use types, highlighting the uniqueness of old-growth forest in harboring endemic ant species which are more sensitive to disturbance. In the agricultural matrix, higher canopy closure and landscape forest cover were associated with an increase of endemic ant species richness but a decrease of exotic ant species richness. We conclude that preserving remnant forest fragments and promoting vanilla agroforests with a greater canopy closure in the agricultural matrix are important management strategies to complement the role of old-growth forests for endemic ant conservation in north-eastern Madagascar.

Diversity of ground‐dwelling ants across three severely threatened South American subtropical forests: are diversity patterns influenced by spatial or climatic variables?

Abstract Understanding the spatial distribution of species sheds light on the biogeographical history, offers clues to the drivers of biodiversity and helps guide conservation strategies. In southern South America, Andean, Chaco and Atlantic forests drastically decreased their coverage in the last decades mainly by changes in land use. Ants represent an excellent model for macro‐ecological studies that support evidence‐based management policies. Unfortunately, little is known about ant distribution, diversity patterns and drivers in the southernmost portion of these three biomes. We surveyed ground‐dwelling ants using baits and leaf‐litter sieves in 38 sites across these subtropical forests in Argentina. We analysed ant species richness, turnover and composition within and between forests, and whether spatial and climatic variables explain diversity patterns. We collected 161 species belonging to 38 genera. The Atlantic forest had the highest cumulative species richness (91 species), followed by the Chaco (60) and Andean (52) forests. Neither mean species richness nor beta diversity differed significantly between forests, though both indicators tended to increase from west to east. Seven spatial and climatic variables differentiated forests. Aridity index, and variables associated with seasonal rainfall, moderately influenced a tendency to increase species richness from west to east. We identified five shared species between the Andean and Atlantic forests, which are candidates to test biogeographic hypotheses. The high level of species replacement across and among forests resulted in unique assemblages (with at least 29 species that seem to be exclusive to one forest), indicating the importance of conserving the biodiversity of the three forests.

Diversity begets diversity: Low resource heterogeneity reduces the diversity of nut‐nesting ants in rubber plantations

One of the most general patterns in ecology is the positive relationship between environmental heterogeneity and local diversity. On the one hand, increased resource heterogeneity provides more resources for diverse consumers in the community. On the other hand, increased structural heterogeneity creates variation in the environment's physical structure, thus allowing the coexistence of diverse species with different environmental requirements. Here, we examined the relative importance of resource and structural heterogeneity in determining the taxonomic, functional, and phylogenetic diversity of nut-nesting ants in natural rainforest and rubber plantation. The species richness of nut-nesting ants was 70% higher in rainforest than in rubber plantation. The clustered functional and phylogenetic structure in rubber plantation suggested a strong effect of environmental filtering in shaping ant functional and phylogenetic structure. Nesting heterogeneity (nut diversity) was the major factor explaining variation in taxonomic, functional, and phylogenetic diversity, suggesting that resource heterogeneity plays a major role in shaping the biodiversity patterns of nut-nesting ants. Overall, these results indicate that decreased resource diversity following the conversion of rainforest to rubber plantation can drive biodiversity loss in nut-nesting ants, through its effect on reducing both ant species, functional, and phylogenetic diversity. The decline in species richness and functional and phylogenetic diversity in the local ant community might have major effects on ecosystem functioning.

Ant Species Diversity, Distribution, and Community Composition in Different Forest Types in Papua New Guinea

Previous studies have provided important scientific information on ant species richness and composition relating to the effects of elevation, sampling approaches, stratification, and forest succession. Yet, they have primarily focused on single sites or regions. Knowledge of ant ecology should also include the impact of disturbance in various forest types. Tuna baiting and hand collection methods were used to investigate diversity and community composition of ants in 16 sites sampled across Papua New Guinea, in both disturbed and pristine forest, at heights ranging from 28 to 2,728 m above sea level. We found 176 species as a result of exposing 320 tuna baits and traversing 72 hand-searched plots. Baiting samples were strongly dominated by a few common species, while the hand-collecting captured more species per plot. The Chao 2 richness estimator for both methods predicted undersampling of the local community. As expected, ant species diversity and richness significantly decrease with increasing elevation. We observed, on average, greater species diversity of ground-dwelling ant communities in disturbed compared to undisturbed forests. The effect was not significant using multivariate randomisations, since the same species dominated both forest classes. The unexpected pattern of ant species richness being locally higher in the disturbed sites is driven by our sampling of undisturbed communities at all elevations, but sampling of the disturbed communities only up to 1,600 m above sea level. Hence, future studies should consider more locations, aiming ideally for an equal sampling effort to capture disturbance stage and elevation.

Ant diversity sampling in the Brazilian Amazon: a comparison of litter collection and pitfall trapping

Introduction: Ants in tropical forests are a hyper-diverse group that plays important ecological roles. Several studies on tropical forests have used different sampling protocols to capture soil ants, making it difficult to compare responses and patterns of diversity between studies. Thus, research that compares different well-structured and standardized sampling methodologies to adequately estimate the richness of ant species in tropical forests is necessary. Objective: In this study, we examined the combination of catches with pitfall traps with and without baits and litter collections for soil ant sampling. Methods: In the fall traps, we use two baited (sardines and bananas) and one non-baited. For the manual collections (litter sampling), the litter and only the topsoil of the loose soil were collected. Results: We found that traps containing sardine baits collected a greater abundance of ants, whereas non-baited traps collected a greater richness of ant species. On the other hand, litter collections captured the largest number of exclusive species, presenting a different species composition from the pitfall traps (with and without baits). In general, baited traps showed greater abundance in more degraded locations, while manual collections and unbaited pitfalls captured more individuals in preserved environments. Conclusions: Our results provide evidence that, for accurate sampling of soil ant assemblages in tropical forests, the use of different methodologies is necessary to capture a greater diversity of species because the methods differ in effectiveness according to habitat.

High Diversity in Urban Areas: How Comprehensive Sampling Reveals High Ant Species Richness within One of the Most Urbanized Regions of the World

The continuous increase in urbanization has been perceived as a major threat for biodiversity, particularly within tropical regions. Urban areas, however, may still provide opportunities for conservation. In this study focused on Macao (China), one of the most densely populated regions on Earth, we used a comprehensive approach, targeting all the vertical strata inhabited by ants, to document the diversity of both native and exotic species, and to produce an updated checklist. We then compared these results with 112 studies on urban ants to illustrate the dual roles of cities in sustaining ant diversity and supporting the spread of exotic species. Our study provides the first assessment on the vertical distribution of urban ant communities, allowing the detection of 55 new records in Macao, for a total of 155 ant species (11.5% being exotic); one of the highest species counts reported for a city globally. Overall, our results contrast with the dominant paradigm that urban landscapes have limited conservation value but supports the hypothesis that cities act as gateways for exotic species. Ultimately, we argue for a more comprehensive understanding of ants within cities around the world to understand native and exotic patterns of diversity.

Spatiotemporal Patterns of Ant Metacommunity in a Montane Forest Archipelago.

Naturally fragmented landscapes are adequate systems for evaluating patterns and mechanisms that determine species distribution without confounding effects of anthropogenic fragmentation and habitat loss. We aimed to evaluate an ant metacommunity's spatiotemporal patterns in montane forest islands amid a grassland-dominated matrix. We assessed these patterns by deconstructing the ant metacommunity into forest-dependent and habitat generalist species. We sampled twice a year (summer and winter) over 2 years (2014 and 2015), using soil and arboreal pitfall traps, in fourteen forest islands (varying in size, shape, and connectivity) in the Espinhaço Range Biosphere Reserve, Brazil. We evaluated the relationship between ant species richness, composition (β-diversity), and predictor variables of forest island structure (canopy cover and understory density) and landscape structure (forest amount, number of forest islands, and shape). We sampled 99 ant species, 66.7% of which were classified as forest-dependent and 33.3% as habitat generalist species. We found that ant β-diversity was higher in space than in time, and that species composition variation in time (temporal β-diversity) differed between ant species groups. Both ant groups responded differently to forest island and landscape structure characteristics. Landscape structure seems to act as a spatial filter and the forest islands' local characteristics as an environmental filter, which jointly determine the local and regional diversity. We demonstrate the importance that forest archipelagos pose to ant metacommunity's structure and dynamics in montane tropical regions. Mountaintop conservation and management strategies must consider the forest island archipelago to maintain the biodiversity and the functioning of these systems.

Species diversity and biological trait function: Effectiveness of ant–plant mutualism decreases as ant species diversity increases

Abstract One of the major concerns of ecological and evolutionary research is the prediction of community function in relation to the degree of biodiversity. To clarify the relationship between biodiversity and the expression of plant defence traits, we investigated ant–plant defensive mutualism in the pioneer plant Mallotus japonicus at several sites across Japan. The plant bears ant‐attracting extrafloral nectar (EFN) and food bodies (FBs) as indirect defence traits. To reveal variations in ant–plant interactions in the field, we measured species richness of nectar‐feeding ants and interaction strength between each ant species and the plant (visiting frequency of each ant species to the plant). We also investigated the expression of EFNs and FBs in natural plant populations at the study sites. To assess the defensive quality of each ant species, we then experimentally estimated the aggressiveness of the dominant ant species. To examine the link between ant species richness and the defensive function of ants, we conducted an ant‐exclusion experiment and a common garden experiment to clarify whether the defence efficacy of ants varied in relation to ant species richness. Ant species richness differed among the study sites. We found negative relationships between ant species richness and the mean interaction strength of ant species, the interaction strength of aggressive ant species and the number of EFNs per leaf. The effectiveness of indirect defence by ants was poor at sites where ant species richness was high. When cultivated in the same environment, plants from sites with low ant species richness developed a larger number of EFNs per leaf than those from sites with high ant species richness. Our results suggest that facultative ant–plant defensive mutualism is weakened at sites where ant species richness is high, resulting in a decrease in the number of EFNs per leaf. Such a link between species richness and an indirect trait function may help us to understand the evolutionary patterns of various species traits in complex biological communities. A free Plain Language Summary can be found within the Supporting Information of this article.

Bottom-up effects on arthropod communities in Platycyamus regnellii (Fabaceae) fertilized with dehydrated sewage sludge

Sewage sludge is a nitrogen-rich organic compound, which can be used to aid development in plants such as Platycyamus regnellii (Fabaceae), in the recovery of degraded areas. This study aimed to assess the bottom-up effects on leaf mass and percentage ofground cover (leaf litter, herbaceous plants, and grasses) in P. regnellii trees fertilized (or not) with dehydrated sewage sludge and arthropod communities over 24 months. Platycyamus regnellii trees fertilized with dehydrated sewage sludge presented significantly more leavesper branch, branches per tree, and a higher percentage of ground cover compared to unfertilized trees. Phenacoccus sp. (Pseudococcidae) was the most abundant phytophagous insect associated with P. regnellii trees. Fertilization did not affect the abundance, diversity, and species richness of Hemiptera phytophagous on P. regnellii trees. However, fertilizedtrees presented higher abundance and species richness of trophobiont-tending ants compared to unfertilized trees, with Camponotus sp. being the most abundant regardless of the treatment. Fertilized P. regnellii trees also presented higher species richness of natural enemies compared to unfertilized ones, with Aranae and Dolichopodidae being the most abundant. We concluded that fertilization with dehydrated sewage sludge improved P. regnellii trees leafmass and ground cover and increased the diversity of trophobiont-tending ants and natural enemies. To our knowledge, this is the first study on the arthropods community associated withthis tree species. This suggests that upon fertilization, P. renellii trees are useful for ecological restoration in severely disturbed areas.

Similarity of ant communities increases with isolation from natural habitat and abundance of invasive ants in oil palm plantations of Central Borneo

Natural habitats can support insect diversity and shape their community structure in agroecosystems. The objective of this research was to investigate how proximity of natural habitat and invasive ant species influences the community structure of ants in oil palm plantations in Central Borneo, Indonesia. Twelve oil palm fields, at varying distances from areas of remaining forest or natural habitat, were selected as research plots. In each plot, insects were sampled using canopy knockdown fogging with a pyrethroid insecticide. In total, we found 62 canopy ant species belonging to six subfamilies. We found that Anoplolepis gracilipes (invasive species) and Oecophylla smaragdina were the most abundant ant species across all of our plots, and their abundances were not spatially correlated. Distance of oil palm fields to natural habitat did not affect species richness and abundance of ants, but affected ant community similarity. Based on the generalized linear models, the ant community similarity was not only affected by the distance to natural habitat but also affected by the abundance of A. gracilipes. A. gracilipes abundance also had a negative effect on other ant abundance especially O. smaragdina. In conclusion, the occurrence of natural habitats helps shape the similarity of ant community in oil palm plantations possibly via inhibits the abundance of invasive species.

Re-established grasslands on farmland promote pollinators more than predators

Agricultural intensification is among the major threats to farmland biodiversity and associated ecosystem services. Agri-environment schemes in Europe aim to counteract the continuous decrease of permanent grassland habitat and related decline of biodiversity in agricultural landscapes. We established new grasslands adjacent to permanent old grasslands to study effects on arthropod pollinators and predators. Over three years, we assessed the effects of newly established grasslands on activity density, species richness and assemblages of pollinators (syrphids, bumblebees, solitary bees) and ground-dwelling predatory arthropods (carabids, spiders, ants). Pollinator activity density and species richness of all three pollinator groups approximately doubled in newly established grasslands compared to old grasslands, indicating suitability of new grasslands as pollinator feeding habitat. Predator responses were less consistent. Species richness and activity density of carabids and ants did not increase in new grasslands, indicating slower adaptation to new habitats. Spider activity density increased in the newly established grasslands and in adjacent cereal fields, but no significant differences in species richness compared to old grasslands were observed. Bumblebees and solitary bees showed distinct distance decays in cereal fields. Syrphid activity density declined in cereal fields far away from the newly established grasslands, but not nearby. Carabids increased and ants decreased in species richness and activity density with increasing distance from old grasslands in cereal fields and newly established grasslands alike. In contrast, spider species richness and activity density decreased with increasing distance from old grasslands in cereal fields only, but there was no distance decay in newly established grasslands. While pollinators utilized the additional floral resources within the whole area of newly established grassland quickly, predators reacted much slower. Even after three years, there was no measurable response of carabid and ant activity density and only a minor response of spiders. This clearly shows that short-term measures are not sufficient to sustainably conserve farmland biodiversity. The conservation of permanent grassland and landscape heterogeneity should be prioritized. However, the restoration of new grassland should also be encouraged by agri-environment schemes as a supplement, to enhance functional biodiversity in agricultural landscapes.

Ant functional structure and diversity changes along a post-grazing succession in Mediterranean oak woodlands

Grazing exclusion may be used to promote the recovery of disturbed ecosystems. A promising way for the evaluation of its effectiveness is through the monitoring of key biological groups, particularly those more responsive to disturbance and playing key roles in ecosystem functioning. Ants have been used as ecological indicators as they are abundant, diverse and sensitive to environmental changes. Here, we aimed to evaluate changes in ant taxonomic and functional structure and diversity, using functional groups, along a post-grazing succession in a Mediterranean oak woodland and to understand which environmental variables drive them. The post-grazing succession comprised a chronosequence of grazing excluded sites for 8, 12 and 18 years and a grazed control site. We found that ant species richness, functional structure and diversity increased with years since grazing exclusion: Generalist/Opportunist and the Hot Climate specialists increased in the 18 years grazing excluded site, while the Cryptic Species group increased in the 12 years grazing excluded site. Yet, their responses were not linear over time. Time since grazing exclusion and vegetation structure explained differences in ant taxonomic and functional structure and diversity. The Invasive/Exotic group dominated in all sites, except in the longest excluded site, where it occurred in the lowest proportion. The invasive Argentine ant dominated the grazed site, where it may have led to ant taxonomic and functional homogenization. Our results suggest that the time and changes in habitat structure may favour the recovery of ant biodiversity, although the presence of the invasive Argentine ant species may have slowed it down.

Small-scale traditional maize farming fosters greater arthropod diversity value than conventional maize farming

Globally insects are in decline, with the transformation of natural areas for agriculture one of the most important drivers of this decline. Yet, insects play an important role in regulating ecosystem services such as pollination, soil fertility and pest suppression, so their conservation within agricultural areas is critical. We examined comparative impacts of traditional small-scale low input farming versus large-scale conventional farming systems, and mono-cropped versus inter-cropped systems in Kenyan maize fields on predator, ant and herbivore arthropod species richness and composition. We also considered the value of hedgerows and percentage of surrounding maize cover for arthropod conservation. As expected, traditional farming retained higher herbivore species richness, evenness and abundance, as well as higher predator abundance compared to conventional farming. Percentage maize cover was positively correlated to ant species richness, predator and herbivore abundance, as well as determining species assemblage composition for ants and herbivores. Hedgerow volume and the comparison of mono- vs inter-cropping were important predictors for predator evenness. These results suggest that the low input farming systems retain far higher arthropod numbers, although this does not seem to be due to the use of intercropping on the farms. Rather it seems that hedgerows play an important role in maintaining arthropods. While higher maize coverage surrounding the farm increases the species and abundance of arthropods in the fields, this is most likely due to the high biotope fidelity of arthropods that specialize in open cropping systems such as maize fields.Implications for insect conservationThe results here are encouraging as the retention of culturally important farming techniques (i.e., the traditional Kenyan farmers) and small improvements, such as the retention of hedgerows, greatly promotes biodiversity in the farmlands.