Habitat preferences of small mammals in tropical open-forest of the Northern Territory

Pattern analysis was used to investigate the habitat preferences of five small mammal species in tropical open-forest of the Northern Territory. Fifty-one sites were classified by faunal abundance and the groups examined for significant differences in vegetation structural attributes and plant species in both dry and wet seasons. The omnivore Isoodon macrourus showed strong association with floristic and vegetation structural attributes only in the dry season, when areas with a dense understorey of small trees and shrubs and a high percentage of leaf litter cover were favoured. Of the two primarily carnivorous species, Antechinus bellus was related strongly with floristic and structural attributes in both seasons and showed a consistent preference for areas with relatively dense low-level foliage (< 2m). By contrast, Dasyurus hallucatus was associated more with the structurally simple open-forest types. Of the two mainly herbivorous species Mesembdomys gouldii showed associations only withfioristics in both seasons, while the habitat relationships of Trichosurus arnhemensis were very weak due to its low abundance in the study area. The number and strength of animal/habitat relationships were greatest in the dry season. Forest types with dense mid-level foliage and abundant hollow logs and leaf litter had the greatest mammal richness and abundance; these areas may be critical to the survival of local mammal populations. A comparison of site-groups, defined independently on the basis of fauna, floristics or structure, showed that animal groups overlapped one to six of the habitat groups. The animal's perception of s‘habitat’ may thus differ from that of humans, or that defined by measurement of habitat attributes.     

Ecological association of birds and vegetation structure in wet tropical forests of Australia

Birds and environments of tropical rainforests were studied in 18 selected areas from sea level to 1520 m within the humid tropical region of northeastern Australia. A total of 122 sites (20 m × 20 m each) were established within the 18 areas, and bird data (observation and mist-netting) and environmental data (pro forma survey and foliage measurements) were collected at each site. The bird data were analysed numerically in two ways: abundance of 146 species in 18 areas and presence and absence of 108 species at 122 sites. Both classification and ordination analyses produced a major discontinuity between the tableland sites and the lowland sites, each divisible further into various types of vine forest and non-vine forest vegetation. The few rare species did not contribute to the general pattern. The environmental data were reduced to a set of those attributes that showed variation among the sites. They included topographic and edaphic features, physiognomic and structural features of vegetation, fruiting and defoliating habits of plants, foliage height diversity and evenness, and canopy cover. The primary pattern in the data set of 135 attributes by 122 sites was vine forest versus nonvine forest, and altitudinal divisions appeared as a secondary pattern, in both classification and ordination. Canonical correlation coefficients between bird vectors and environmental vectors were reasonably high for the first four canonical vectors, which correlated well with major Gower vectors of birds and environments. The back-correlation to the raw data produced bird species and matching environmental attributes with sites sharing them for both positive and negative ends of each canonical vector. In general, the analysis extracted elements of both fauna and environment that characterized the vine forest as opposed to the non-vine forest and the tableland sites as opposed to the lowland sites. Canonical correlation analysis is limited by the unverifiable nature of derived correlations. Such correlations may suggest certain associations to be tested by independent means (hypothesis-generating function), but may also formalize self-evident or fortuitous associations.     

Explaining bird species composition and richness in eucalypt-dominated remnants in subhumid Tasmania

Aim To determine the factors influencing the distribution of birds in remnants in a fragmented agricultural landscape. Location Forty‐seven eucalypt remnants and six sites in continuous forest in the subhumid Midlands region of Tasmania, Australia. Methods Sites were censused over a two‐year period, and environmental data were collected for remnants. The avifauna of the sites was classified and ordinated. The abundances of bird species, and bird species composition, richness, abundance and diversity were related to environmental variables, using simple correlation and modelling. Results There were two distinct groups of sample sites, which sharply differed in species composition, richness, diversity and bird abundance, separated on the presence/absence of noisy miner (Manorina melanocephala Latham) colonies, remnant size, vegetation structural attributes and variables that reflected disturbance history. The approximate remnant size threshold for the change from one group to another was 20–30 ha. Remnant species richness and diversity were most strongly explained by remnant area and noisy miner abundance, with contributions from structural and isolation attributes in the second case. Segment richness was explained by precipitation, logging history and noisy miner abundance. Bird abundance was positively related to precipitation and negatively related to tree dieback. The 28 individual bird species models were highly individualistic, with vegetation structural variables, noisy miner abundance, climatic variables, variables related to isolation, area, variables related to floristics, disturbance variables, the nature of the matrix and remnant shape all being components in declining order of incidence. Age of the remnant did not relate to any of the dependent variables. Main conclusions Degraded and small remnants may have become more distinct in their avifaunal characteristics than might otherwise be the case, as a result of the establishment of colonies of an aggressive native bird, the noisy miner. The area, isolation and shape of remnants directly relate to the abundance of relatively few species, compared to vegetation attributes, climate and the abundance of the noisy miner. The nature of the matrix is important in the response of some species to fragmentation.     

长江口潮下带春季大型底栖动物的群落结构

2005年4月对长江口全区域潮下带共10个采样站位的大型底栖动物进行了调查。调查采获大型底栖动物38种,分属5个生态类型,种类数较少,河口外缘站位种类数多于口内站位。各站位大型底栖动物的平均丰度为32.9个/m2、平均生物量为5.035g/m2(湿重);与20世纪七八十年代相比,平均生物量显著降低;口外缘站位的总丰度和总生物量均高于口内站位。环境因子相关分析表明,盐度是决定长江口大型底栖动物种类分布最重要的环境因子。群落聚类、标序分析显示,春季长江口潮下带大型底栖动物群落结构空间分异明显,完全符合目前长江口支、港、槽“三级分汊”的空间格局。其中,北支的大型底栖动物以混合高盐水种类为主,而南支则以淡水和半咸水种类为主。南支的南北槽分界处内外站位的群落差异也由盐度决定,因为靠近口内的群落均受长江冲淡水影响较大;而口外站位群落则受咸淡水影响。南支的南北港分界点内外的群落差异则主要受长江来水的影响,原因在于处在港分界点以内的群落所在区域,直接受长江来水的冲刷,底质环境极不稳定;而港、槽分界点之间的群落所在区域由于河口上段的诸多明暗沙体的阻挡,水势较为稳定,所以底质环境较稳定,从而使得港、槽分界点之间的群落出现了更多的沙蚕等底质环境类型种类。     

Wildlife-Habitat Restoration in an Urban Park in Southern California

Within an urban park in southern California, the relationship between the structure and floristics of vegetation and the distribution, abundance, and behavior of wildlife was studied in relatively undisturbed areas (San Luis Rey) and in contiguous areas (Guajome Park) in need of restoration. These data were used to develop recommendations for the enhancement of native animal species in the park. The abundance of amphibians and reptiles was highest in native upland scrub and willow (Salix)-riparian vegetation types, and lowest in dry, disturbed sites. Western fence lizards (Sceloporus occidentalis) were the most abundant reptile throughout both study areas. Overall, bullfrogs (Rana catesbiana), an exotic species, were the dominant amphibians; the native Pacific treefrog (Hyla regilla) was rare throughout. At both study areas, the small mammal community was dominated by western harvest mice (Reithrodontomys megalotis) and deer mice (Peromyscus maniculatus) and, to a lesser extent, by brush mice (P. boylii) and exotic house mice (Mus musculus). Negative correlations in abundance existed between house mice and harvest mice, and between house mice abundance and overall small mammal abundance. In riparian sites, cottonwood (Populus fremontii) and various height classes of willow were the dominant factors in the majority of bird abundance–habitat‘correlations and where foraging activities were concentrated. Recommendations for enhancing native animal species include reduction of marsh sedimentation, removal of feral species, and development of connections between the park and nearby natural areas. A corridor of native riparian vegetation (primarily cottonwood-willow) should be developed to replace the existing agricultural fields, thereby linking Guajome with the San Luis Rey River.     

Site vegetation characteristics are more important than landscape context in determining bird assemblages in revegetation

The effectiveness of revegetation in providing habitat for fauna is expected to be determined both by within‐site factors and attributes of the landscape in which a revegetation site occurs. Most studies of fauna in revegetation have been conducted in landscapes that have been extensively cleared, modified or fragmented, and in Australia, predominantly in the southern temperate zone. We investigated how within‐site vegetation attributes and landscape context attributes were related to bird species richness and composition in a chronosequence of post‐mining rehabilitation sites within an otherwise intact landscape in tropical northern Australia. Our working hypothesis was that bird species richness in rehabilitating sites would be positively related to site vegetation structure and landscape context including (1) proximity to woodland and (2) the proportion of woodland within a 500‐m buffer of rehabilitation sites. Within each of 67 sites, we sampled vegetation once and surveyed for birds eight times over 16 months. Landscape context variables were calculated using GIS. There were large differences between bird assemblages of woodland and rehabilitation sites and between age classes of rehabilitation. Bird assemblages were strongly related to site vegetation attributes across all rehabilitation sites. Proximity to woodland was only related to bird assemblages in rehabilitation sites older than 4 years old. We conclude that the relative importance of landscape context and site variables at any point in time will be a function of how closely vegetation within the revegetation site matches the habitat resource requirements of individual species.     

Sampling design in large-scale vegetation studies: Do not sacrifice ecological thinking to statistical purism!

Most of the historical phytosociological data on vegetation composition have been sampled preferentially and thus belong to those ecological data that do not fulfill the statistical assumption of independence of observations, necessary for valid statistical testing and inference. Nevertheless, phytosociological data have been recently used for various ecological meta-analyses, especially in studies of large-scale vegetation patterns. For this reason, we focus on the comparison of preferential sampling with other sampling designs that have been recommended as more convenient alternatives from the point of view of statistical theory. We discuss that while simple random sampling, systematic sampling and stratified random sampling better meet some of the statistical assumptions, preferential sampling yields data sets that cover a broader range of vegetation variability. Moreover, today’s large phytosociological databases provide huge amounts of vegetation data with unrivalled geographic extent and density. We conclude that in the near future ecologists will not be able to replace the preferentially sampled phytosociological data in large-scale studies. At the same time, phytosociological databases have to be complemented with relevés of vegetation composed mostly of common and generalist species, which are under-represented in historical data. Stratified random sampling seems to be a suitable tool for doing this. Nevertheless, a methodology and input data for stratification have to be developed to make stratified random sampling an ecologically more relevant and practical method.     

Bias in vegetation databases? A comparison of stratified‐random and preferential sampling

Aim: Vegetation plots collected since the early 20th century and stored in large vegetation databases are an important source of ecological information. These databases are used for analyses of vegetation diversity and estimation of vegetation parameters, however such analyses can be biased due to preferential sampling of the original data. In contrast, modern vegetation survey increasingly uses stratified‐random instead of preferential sampling. To explore how these two sampling schemes affect vegetation analyses, we compare parameters of vegetation diversity based on preferentially sampled plots from a large vegetation database with those based on stratified‐random sampling. Location: Moravian Karst and Silesia, Czech Republic. Methods: We compared two parallel analyses of forest vegetation, one based on preferentially sampled plots taken from a national vegetation database and the other on plots sampled in the field according to a stratified‐random design. We repeated this comparison for two different regions in the Czech Republic. We focussed on vegetation properties commonly analysed using data from large vegetation databases, including alpha (within‐plot) diversity, cover and participation of different species groups, such as endangered and alien species within plots, total species richness of data sets, beta diversity and ordination patterns. Results: The preferentially sampled data sets obtained from the database contained more endangered species and had higher beta diversity, whereas estimates of alpha diversity and representation of alien species were not consistently different between preferentially and stratified‐randomly sampled data sets. In ordinations, plots from the preferential samples tended to be more common at margins of plot scatters. Conclusions: Vegetation data stored in large databases are influenced by researcher subjectivity in plot positioning, but we demonstrated that not all of their properties necessarily differ from data sets obtained by stratified‐random sampling. This indicates the value of vegetation databases for use in biodiversity studies; however, some analyses based on these databases are clearly biased and their results must be interpreted with caution.     

Exploring a new biodiversity frontier: subterranean ants in northern Australia

Although it is common for ant surveys to uncover previously uncollected species, a recent study of subterranean ants in Amazonian Ecuador has indicated that an entire ant fauna may remain largely undiscovered. Here we report on the first systematic investigation of subterranean ants in northern Australia, in order to assess the extent to which the high abundance and diversity of subterranean ants in Amazonia is apparent in tropical Australia. We use a novel sampling technique that combines elements of an attractant bait and a pitfall trap, and allows many traps to be deployed simultaneously. Our main study was conducted at three closely approximated sites in Darwin, where the local ant fauna has been intensively surveyed using conventional (above-ground) sampling techniques. The 720 traps deployed resulted in 421 species records, representing 29 species from 17 genera. Sixteen of these species have cryptobiotic morphology, with four recorded here for the first time. Remarkably, one of these four (a blind species of Solenopsis) was the second most frequently caught species in subterranean traps, with 70 records. Ant abundance, species richness and composition varied markedly between sites, despite site similarity in soils and vegetation. Total ant records were greater in the middle compared with start of the wet season, declined with depth, and were greater after 4 days than one. Sampling at six sites in the Mitchell Falls area of the northern Kimberley region, 1,200 km southwest of Darwin, also revealed several cryptobiotic species new to science, including a new genus record (Pseudolasius) for Western Australia. Our underground sampling has therefore revealed an abundant and diverse subterranean ant fauna in northern Australia, containing many cryptobiotic species not previously collected. We use our results to provide methodological guidelines for most effectively sampling this fauna. Combined with the Amazonian study, our findings indicate that a specialist subterranean ant fauna, including numerous species remaining to be discovered, might be a feature of tropical landscapes throughout the world.     

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.     

Sampling strategies for the assessment of tree species diversity

Abstract. This paper aims at proposing efficient vegetation sampling strategies. It describes how the estimation of species richness and diversity of moist evergreen forest is affected by (1) sampling design (simple random sampling, random cluster sampling, systematic cluster sampling, stratified cluster sampling); (2) choice of species richness estimators (number of observed species vs. non-parametric estimators) and (3) choice of diversity index (Simpson vs. Shannon). Two sites are studied: a 28-ha area situated in the Western Ghats of India and a 25-ha area located at Pasoh in Peninsular Malaysia. The results show that: (1) whatever the sampling strategy, estimates of species richness depend on sample size in these very diverse forest ecosystems which contain many rare species; (2) Simpson's diversity index reaches a stable value at low sample sizes while Shannon's index is affected more by the addition of rare species with increasing sample size; (3) cluster sampling strategies provide a good compromise between cost and statistical efficiency; (4) 300 - 400 sample trees grouped in small clusters (10–50 individuals) are enough to obtain unbiased and precise estimates of Simpson's index; (5) the local topography of the Western Ghats has a major influence on forest composition, the steep slopes being richer and more diverse than the ridges and gentle slopes; (6) stratified cluster sampling is thus an interesting alternative to systematic cluster sampling.     

Large variation of suction sampling efficiency depending on arthropod groups,species traits,and habitat properties

Suction sampling is widely used to estimate arthropod abundance and diversity. To test the reliability of abundance data derived from suction sampling, we examined sampling efficiency across a wide range of arthropod groups and tested for effects of species traits, vegetation density, and differences between sites. Suction sampling efficiency was quantified by vacuuming an enclosed meadow area and subsequent removal of the turf, which was treated with heat extraction to collect the remaining arthropods. We obtained 250 pairs of suction and turf samples from seven grasslands with variable vegetation density. High suction sampling efficiencies between 49 and 86% were obtained for Auchenorrhyncha, Heteroptera, Araneida, Curculionoidea, Hymenoptera, and Diptera. In contrast, efficiencies were below 30% for Aphidae, Thysanoptera, Staphylinidae and other Coleoptera, and for soil arthropods such as Collembola, Isopoda, Diplopoda, and Formicidae. Efficiency varied significantly among habitats (sites) for most groups, often more than two‐fold. Surprisingly, sampling efficiency for Hymenoptera, Diplopoda, and Collembola increased with vegetation density, probably because aboveground activity of these taxa was higher in dense vegetation. Suction sampling was nearly twice as efficient for spiders living in the vegetation than for spiders living near the soil surface, and cursorial and large‐bodied spider species were more efficiently sampled than web‐builders and small species. Depending on the sampling effort, suction sampling missed between 49% (one sample) and 31% (250 samples) of the spider species present. Suction sampling efficiency varied more strongly among sites and among arthropod groups than previously recognized. Abundance data derived from suction sampling are strongly underestimated, especially for arthropods living near the soil surface. Thus, comparisons of abundance and diversity between sites should be restricted to vegetation‐dwelling species of the most efficiently sampled groups. The positive relationship of sampling efficiency with vegetation density demonstrates that variation in efficiency is mediated by arthropod behaviour.     

Local and landscape factors determining occurrence of phyllostomid bats in tropical secondary forests

Neotropical forests are being increasingly replaced by a mosaic of patches of different successional stages, agricultural fields and pasture lands. Consequently, the identification of factors shaping the performance of taxa in anthropogenic landscapes is gaining importance, especially for taxa playing critical roles in ecosystem functioning. As phyllostomid bats provide important ecological services through seed dispersal, pollination and control of animal populations, in this study we assessed the relationships between phyllostomid occurrence and the variation in local and landscape level habitat attributes caused by disturbance. We mist-netted phyllostomids in 12 sites representing 4 successional stages of a tropical dry forest (initial, early, intermediate and late). We also quantitatively characterized the habitat attributes at the local (vegetation structure complexity) and the landscape level (forest cover, area and diversity of patches). Two focal scales were considered for landscape characterization: 500 and 1000 m. During 142 sampling nights, we captured 606 individuals representing 15 species and 4 broad guilds. Variation in phyllostomid assemblages, ensembles and populations was associated with variation in local and landscape habitat attributes, and this association was scale-dependent. Specifically, we found a marked guild-specific response, where the abundance of nectarivores tended to be negatively associated with the mean area of dry forest patches, while the abundance of frugivores was positively associated with the percentage of riparian forest. These results are explained by the prevalence of chiropterophilic species in the dry forest and of chiropterochorous species in the riparian forest. Our results indicate that different vegetation classes, as well as a multi-spatial scale approach must be considered for evaluating bat response to variation in landscape attributes. Moreover, for the long-term conservation of phyllostomids in anthropogenic landscapes, we must realize that the management of the habitat at the landscape level is as important as the conservation of particular forest fragments.     

Conservation of arthropod diversity in montane wetlands: effect of altitude, habitat quality and habitat fragmentation on butterflies and grasshoppers

1. The patterns of arthropod diversity were investigated in 24 montane wetlands in Switzerland. These differed in altitude, management regime (cattle-grazing vs. mowing), vegetation structure (index combining vegetation height and density) and degree of habitat fragmentation.
2. The general arthropod diversity was determined by net sampling at 10 sampling points per site. The diversity of grasshoppers and butterflies was measured by counting species richness at the site and species density (species richness per unit area) on transects. The species richness of grasshoppers and butterflies was found to be more sensitive to the geographical attributes of the site whereas species density was more affected by the habitat quality.
3. Grasshopper diversity decreased within the observed altitudinal range (800–1400 m) and was higher at grazed sites, whereas butterfly diversity was higher at mown sites. Arthropod diversity but not abundance of arthropods was positively related to the vegetation structure.
4. The species richness of butterflies was negatively influenced by the degree of habitat fragmentation: both the size of habitat as well as the area of wetland habitats within 4 km were related positively to the number of specialist wetland butterflies.
5. Late mowing as well as low-density cattle-grazing are appropriate management actions to maintain arthropod diversity in montane wetlands. In order to establish site-specific management plans, the biology of the present target species as well as the historical context should be considered.
6. We suggest that the best protection for the species examined in this study would be a network of wetland sites managed using a variety of traditional, non-intensive methods. This can only be achieved by coordinated planning of conservation measures among sites.     

Fauna as passengers and drivers in vegetation restoration: A synthesis of processes and evidence

Efforts to restore terrestrial woody ecosystems to former agricultural land are typically based on plant‐focused actions, often neglecting fauna. However, the processes that maintain or restore the health and integrity of these ecosystems involve many animal–plant interactions. Here, I synthesise information about these relationships and the implications for revegetation practice. Fauna have often been viewed as passengers, responding passively to plant‐focused revegetation. This view involves two surrogacy assumptions: first, that vegetation attributes can indicate habitat sufficiency for fauna; second, that animals will be capable of dispersing to the restored habitat and of establishing populations there. Habitat sufficiency depends on how resources such as food and nest sites can be indicated by vegetation attributes and how they interact with an animal's species‐specific requirements. Dispersal and establishment depend on proximity to source populations in habitat elsewhere, the type of intervening habitat and the intrinsic mobility of different species. Evidence about the effects of age, revegetation type and spatial context in relation to animal communities indicates that it can often be invalid to assume vegetation surrogacy. Fauna can also drive the developmental trajectories of floristic diversity and composition during revegetation, because animal–plant interactions frequently mediate life‐history transitions that determine seedling recruitment. Frugivore‐mediated seed dispersal is the best studied, but animals also directly influence early‐stage tree recruitment, especially through their roles in seed predation, seedling herbivory and indirectly through top‐down cascades that include large carnivores. These processes have been insufficiently recognised or studied, although some recent work highlights their significance. Intervening to alter abundances of functionally important animals could be useful in accelerating the redevelopment of woody vegetation. Further research is needed to clarify animals’ roles as both passengers and drivers during revegetation, especially manipulative experiments and innovative restoration trials, in which animals and plants are considered together from the outset.     

Biodiversity Characterization in Nubra Valley, Ladakh with Special Reference to Plant Resource Conservation and Bioprospecting

Trans-Himalayan mountains, owing to harsh climatic conditions and a short growing season support low vegetation cover (<20%), yet it is known to harbour a unique assemblage of flora and fauna which have not been systematically inventoried and documented so far. This paper deals with spatial and non-spatial information on landscape units, vegetation characteristics and plant species diversity of Nubra Valley in Ladakh, India. Based on digital – visual (on screen) interpretation of remote sensing data coupled with knowledge-based classification we delineated 19 cover classes (11 vegetation types and 8 non-vegetation categories). The vascular plants (angiosperms and gymnosperms) were systematically collected using stratified random sampling of different landscape/vegetation to characterize plant communities and assess the distribution patterns of species. The study reveals that nearly 78–80% of plant species in Nubra are restricted to the valley bottoms. In all, 414 species of vascular plants were recorded from the study area. These belongs to 56 families and 202 genera. Of these, 102 species were reported to be used in traditional system of medicine by Amchis over 80 species are largely associated with cultivated fields and human habitation. As many as 49 species were cultivated which include several varieties of crop plants especially those of barley and buckwheat. Aspects of bioprospecting and conservation of valuable species have been discussed.     

Seasonal abundance and habitat use of bird species in and around Wondo Genet Forest,south‐central Ethiopia

The habitat use and seasonal migratory pattern of birds in Ethiopia is less explored as compared to diversity studies. To this end, this study aimed at investigating the patterns of distribution related to seasonality and the effect of habitat characteristics (elevation, slope, and average vegetation height) on habitat use of birds of Wondo Genet Forest Patch. A stratified random sampling design was used to assess the avian fauna across the four dominant habitat types found in the study area: natural forest, wooded grassland, grassland, and agroforestry land. A point transect count was employed to investigate avian species richness and abundance per habitat type per season. Ancillary data, such as elevation above sea level, latitude and longitude, average vegetation height, and percent slope inclination, were recorded with a GPS and clinometers per plot. A total of 33 migratory bird species were recorded from the area, of which 20 species were northern (Palearctic) migrants while 13 were inter‐African migrants. There was a significant difference in the mean abundance of migratory bird species between dry and wet seasons (t = 2.13, p = .038, df = 44). The variation in mean abundance per plot between the dry and wet seasons in the grassland habitat was significant (t = 2.35, p = .051, df = 7). In most habitat types during both dry and wet seasons, omnivore birds were the most abundant. While slope was a good predictor for bird species abundance in the dry season, altitude and average vegetation height accounted more in the wet season. The patch of forest and its surrounding is an important bird area for migratory, endemic, and global threatened species. Hence, it is conservation priority area, and the study suggests that conservation coupled with ecotourism development is needed for its sustainability.     

Season‐modulated responses of Neotropical bats to forest fragmentation

Seasonality causes fluctuations in resource availability, affecting the presence and abundance of animal species. The impacts of these oscillations on wildlife populations can be exacerbated by habitat fragmentation. We assessed differences in bat species abundance between the wet and dry season in a fragmented landscape in the Central Amazon characterized by primary forest fragments embedded in a secondary forest matrix. We also evaluated whether the relative importance of local vegetation structure versus landscape characteristics (composition and configuration) in shaping bat abundance patterns varied between seasons. Our working hypotheses were that abundance responses are species as well as season specific, and that in the wet season, local vegetation structure is a stronger determinant of bat abundance than landscape‐scale attributes. Generalized linear mixed‐effects models in combination with hierarchical partitioning revealed that relationships between species abundances and local vegetation structure and landscape characteristics were both season specific and scale dependent. Overall, landscape characteristics were more important than local vegetation characteristics, suggesting that landscape structure is likely to play an even more important role in landscapes with higher fragment‐matrix contrast. Responses varied between frugivores and animalivores. In the dry season, frugivores responded more to compositional metrics, whereas during the wet season, local and configurational metrics were more important. Animalivores showed similar patterns in both seasons, responding to the same group of metrics in both seasons. Differences in responses likely reflect seasonal differences in the phenology of flowering and fruiting between primary and secondary forests, which affected the foraging behavior and habitat use of bats. Management actions should encompass multiscale approaches to account for the idiosyncratic responses of species to seasonal variation in resource abundance and consequently to local and landscape scale attributes.     

Skink and invertebrate abundance in relation to vegetation, rabbits and predators in a New Zealand dryland ecosystem

We explored the relationships between ground vegetation, ground fauna (native skinks and invertebrates), rabbits, and predators in a modified New Zealand dryland ecosystem. We hypothesised that vegetation cover would provide habitat for ground fauna. We also hypothesised that rabbits (Oryctolagus cuniculus) would reduce the abundance of these fauna by reducing vegetation, and by providing prey for mammalian predators (cats Felis catus and ferrets Mustela putorius) that consume ground fauna as secondary prey. We measured these variables at 30 sites across three pastoral properties in the South Island in 1996 and 2002. There were mostly positive relationships between vegetation ground cover and fauna captures in pitfall traps. Relatively few beetles and caterpillars were caught where cover was less than 80%, no millipedes were caught where cover was less than 70%, and few spiders and mostly no skinks, crickets, flies or slugs were caught where vegetation cover was less than 50%. Most grasshoppers were caught where cover ranged from 30 to 80%. Faunal species richness was also positively related to cover. This supports our hypothesis that ground vegetation provides habitat for skinks and invertebrates in this ecosystem. The introduction of rabbit haemorrhagic disease in 1997 provided a natural experiment to test the hypothesised indirect effects of rabbits on ground fauna. Declines in rabbits varied between properties, and vegetation cover and predator abundance changed according to the magnitude of these declines. However, skink and invertebrate abundance did not track these changes as expected, but instead varied more or less consistently between properties. Some fauna increased (skink captures quadrupled and cricket captures nearly doubled), others declined (flies, caterpillars and spiders), and some did not change (beetles, millipedes, slugs and grasshoppers, and faunal species richness and diversity). Therefore, rabbits, predators and vegetation did not affect changes in skinks and invertebrates in consistent ways. The dynamics of ground fauna are likely to be more influenced by factors other than those we measured.     

Patterns of Ant (Hymenoptera: Formicidae) Richness and Relative Abundance along an Aridity Gradient in Western Venezuela

In xeric ecosystems, ant diversity response to aridity varies with rainfall magnitude and gradient extension. At a local scale and with low precipitation regimes, increased aridity leads to a reduction of species richness and an increased relative abundance for some ant species. In order to test this pattern in tropical environments, ant richness and relative abundance variation were evaluated along 35 km of an aridity gradient in the Araya Peninsula, state of Sucre, Venezuela. Three sampling stations comprising five transects each were set up. Pitfall traps and direct collecting from vegetation were assessed per transect. Overall, 52 species, 23 genera, and 7 subfamilies of ants were recorded in the peninsula. The total number of species and genera recorded by both sampling stations and transects decreased linearly with increasing aridity. Total relative abundance was highest in the most arid portion of the peninsula, with Crematogaster rochai (Forel) and Camponotus conspicuus zonatus (Emery) (Hymenoptera: Formicidae) being the numerically dominant species. Spatial and multivariate analyses revealed significant changes in ant composition every 11 km of distance, and showed a decrease of ant diversity with the increase of harsh conditions in the gradient. Here, we discuss how local geographic and topographic features of Araya originate the aridity gradient and so affect the microhabitat conditions for the ant fauna.