Microhabitat Traits Research Articles

Geographic drivers more important than landscape composition in predicting bee beta diversity and community structure

AbstractThe importance of microhabitat traits such as floral availability is well known; however, forest bee spatial dynamics have been variably studied across local to broad geographic scales. Past literature suggests that landscape factors from proximate to distal are important in determining forest bee community metrics, including richness, abundance, and taxonomic composition. Leveraging the interest and assistance of citizen science volunteers, we employed standard bee bowl trap transects across Maryland, Delaware, northern Virginia, and the District of Columbia and identified correlations between bee community composition, local and regional land cover, and broader geospatial patterns. We also identified the partial contributions of both specific species and sampling sites to total beta diversity. Various land cover metrics were significantly related to bee community structure, with bee abundance positively and negatively correlated with forest and wetland cover, respectively. In general, land cover metrics within 1000‐m buffer exhibited stronger correlations with bee communities; however, broader geographic variation, using Cartesian coordinates north and east as indices, was most significantly correlated with the bee community. Specifically, bee communities were less rich in the east and south of the study area. We also identified similar correlations with the bee community as categorized by both trophic and nesting behaviors, with both geographic northing and easting proving to be most strongly correlated with the forest bee community. Results of beta diversity and cluster analyses showed that the most species‐depauperate sites exhibited the highest contributions to beta diversity and that species‐poor sites consisted of a reduced subset of the greater community. Our results show that successful bee conservation must consider, beyond local‐scale resource availability, broad geospatial considerations and forest habitat connectivity across political and administrative boundaries.

Multi-spatial analysis on cave ecosystems to predict the diversity of subterranean invertebrates

Subterranean habitats around the world can shelter diversified and threatened faunal communities. However, issues related to alterations in the landscape and structure of subterranean habitats still need to be better understood. Therefore, we used a multi-spatial scale analysis of land cover, land use, and cave habitats to predict the diversity of communities of subterranean invertebrates. We hypothesized that changes in land cover promote alterations in both faunal richness and composition and microhabitat diversity and that microhabitat features determined subterranean biodiversity. Sixteen limestone caves were sampled in Brazil at micro, meso, and macro scales using quadrats (1m²), transects (100 meters) as sample units inside caves and buffers with the radius of 100 and 250 meters in the surroundings of the cave entrances. Models performed showed that land cover and land use influenced cave environments, regarding both microhabitats traits and terrestrial invertebrate richness and composition. We also observed a relationship between microhabitat structure and terrestrial invertebrate richness and composition. Our results showed that deforested areas had negative effects on species richness and changed their composition, while natural areas had positive effects on microhabitat diversity. The same effects were observed for both 100 and 250 meters buffers. Invertebrate richness was negatively predicted by deforested areas while positively predicted by natural areas. Richness was also positively predicted by the combination of all microhabitat traits, and dissimilarity of fauna was influenced by microhabitat diversity in mesoscale and microscale by all microhabitat elements. The results highlight the importance of the landscape surrounding the caves to conserve the subterranean habitats and their fauna. Due to the spatial and temporal changes in the global environmental scenario, we argue the urgency of further detailed studies in fragmented landscapes to define minimum areas of protection for cave environments.

Combined application of biochar and N fertilizer shifted nitrification rate and amoA gene abundance of ammonia-oxidizing microorganisms in salt-affected anthropogenic-alluvial soil

Biochar has been globally recognized as a novel and eco-friendly soil ameliorant to mitigate hazardous effects of salinization on soil health, and mediate carbon and nitrogen (N) nutrient cycling in agricultural ecosystems. However, knowledge pertaining to the regulatory mechanism of biochar application on nitrification in the salt-affected soil is limited. In this study, field plot experiment for three consecutive years and an aerobic incubation experiment with three biochar application rates (7.5, 15, and 30 ton ha−1) and N fertilizer (225 kg N ha−1 yr−1) were conducted. We investigated the effect of combined application of biochar and N fertilizer on soil chemical and microbial properties, nitrification kinetic parameters, and the abundance of ammonia monooxygenase (subunit A, amoA) gene of ammonia-oxidizing bacteria (AOB) and archaea (AOA). Our results showed that biochar addition increased soil pH, cation exchange capacity, available potassium, and microbial biomass carbon, and decreased the numbers of amoA-AOB gene in the salt-affected soil applied with N fertilizer. The nitrification process and fitted kinetic parameters were negatively responsive to the combined application of biochar and N fertilizer, which reduced the nitrification potential and potential nitrification rate, and prolonged the duration of nitrification. The nitrification rate and abundance of amoA-AOB and amoA-AOA genes decreased under biochar and N fertilizer addition, and biochar played the predominant role in the inhibiting effect, which aggravated with the increase of biochar rate. The AOB dominated the autotrophic nitrification with the nitrification rate having higher positive correlation with abundance of amoA-AOB gene than with that of amoA-AOA gene. The abundance of both amoA-AOB and amoA-AOA genes showed significantly negative correlation with nitrate nitrogen (NO3−-N) concentration. In conclusion, biochar and N fertilizer addition inhibited the autotrophic nitrification rate mainly by greatly reducing the abundance of amoA-AOB gene, which was adaptive to the changing soil microhabitat traits induced by biochar application and N fertilization.

Nest site selection and nesting behavior of the mud turtle Kinosternon scorpiodes (Testudines, Kinosternidae) in Palo Verde National Park, Costa Rica: implications for management

Habitat selection is the process whereby individuals preferentially use, or occupy, a non-random set of available habitats. At the same time, nest site selection is defined as the placement of eggs by females at sites differing from random sites within a delimited area. We located 59 nests of the mud turtle Kinosternon scorpioides in Palo Verde National Park (PVNP) in Northwestern Costa Rica. We compared eight microhabitat variables at nest sites against those at random sites. Females significantly placed their eggs at sites with more understory, leaf litter cover, and greater leaf litter depth than in random sites. Additionally, females selected sites with lower air and soil temperature and lower air humidity. Palo Verde NP is subject to active management actions designed to control invasive plant species in the wetland, namely cattail (Thypha domingensis Pers.). The main actions have been cattle grazing, controlled fires, and mechanical crushing of vegetation. We found that habitat quality in nesting areas is being threatened by at least one of these actions: cattle grazing. This is detrimental for three microhabitat traits that turtles select for nesting sites: understory cover, leaf litter cover, and leaf litter depth. The continued degradation of microhabitats at nesting areas of K. scorpioides at PVNP could be affecting recruitment due to embryo survivorship.

Diversity patterns of Coleoptera and saproxylic communities in unmanaged forests of Mediterranean mountains

Abstract Beetle communities are excellent indicators to monitor biodiversity in forest environments. The most common indicators monitored for assessing the effectiveness of the sustainable forest management measures are deadwood amount, forest structure, and microhabitat traits. In Mediterranean mountain forests, however, the relationships between stand-level attributes and species diversity indicators have been still poorly studied. We have investigated the patterns of species diversity of beetle communities in relation to stand structural traits in two unmanaged forests located in central Apennines (Italy). The two forest stands are characterized by different tree species composition and management history. The experimental area extends over approximately 300 ha, within which 50 circular plots of 530 m2 were sampled for each studied forest. Coleoptera were collected using window flight traps and emergence traps on decaying deadwood. We evaluated i) the differences in species diversity (richness, Shannon diversity and Simpson diversity) between the two forests and ii) the beetle Shannon diversity and composition in relation to selected forest variables, with a particular focus on saproxylic species. Principal Component Analysis followed by rarefaction analysis were applied to examine differences in species diversity. Within each forest stand, a Boosted Regression Tree model and a Non-Metric Multidimensional Scaling were performed to relate the species Shannon diversity and community assemblages to the forest structural attributes. Results revealed how these forest structural attributes have a fundamental role in influencing the diversity of Coleoptera and their assemblages. Forest vertical heterogeneity, snag volume and tree dominance were the most important variables for saproxylic assemblages in these Mediterranean mountain forests, while the amount of coarse woody debris positively affected the overall beetle diversity and that of saproxylic species. At stand level, differences in species diversity were mainly driven by tree composition, probably indicating that food resources, determined by tree species, are of primary importance in determining species assemblages and beetle diversity in these forests; while at plot level, we found that the variables, which drove species composition and beetle diversity, varied between the two forests. This study provides the basis for the integration of independent biodiversity indicators in sustainable solutions for the conservation of unmanaged forests in Mediterranean mountain systems.

Substrate moisture, particle size and temperature preferences of trap‐building larvae of sympatric antlions and wormlions from the rainforest of Borneo

1. Larvae of antlions (Neuroptera: Myrmeleontidae) and wormlions (Diptera: Vermileonidae) display a convergently evolved sit‐and‐wait hunting strategy of building pitfall traps in sandy areas. This study investigated a sympatric population of antlions and wormlions in the lowland rainforest of Borneo for substrate moisture, particle size and temperature preferences. It was hypothesised that these animals would show different preferences regarding these microhabitat traits.2. The results showed that antlions had a higher aversion to moisture compared with wormlions, but that wormlions had a higher preference for small‐particle sand. Furthermore, thermal preferences in antlions and wormlions were significantly different, with antlions choosing higher temperatures.3. The detected differences between antlions and wormlions might contribute to their niche partitioning in the mixed Bornean population and thus facilitate coexistence of these animals. It is possible that the hotter and dryer microhabitat edges are preferred by antlions.

Epiphytic strangler trees colonizing extreme habitats of building envelopes in Hong Kong

Trees growing spontaneously on building envelopes, as wall vegetation, denote unique urban ecology. This study investigates the tree flora, substrate, and colonization-development factors on poorly-maintained buildings in Hong Kong. Field surveys gleaned data on species composition, microhabitat, shoot-root dimensions, and biomass structure. The survey sampled 567 trees. They belonged to ten species, distinguished as strong stranglers, moderate stranglers and non-stranglers. Strong stranglers, such as the native Ficus microcarpa and F. virens, were dominant, with diaspores dispersed mainly by frugivorous birds tapping cultivated and ruderal trees. Most trees had limited crown spread and height, and the larger ones were strong stranglers. The compact tree form, reflecting growth constraints, limited their landscape-scenic contributions. Most surface roots displayed restricted lateral growth contrasted by more vertical extension. Five microhabitats were identified. Two mainly vertical ones accommodated 42.3% of the trees, including wall vertical surface holding the most, and pipe surface. Three mainly horizontal microhabitats, more conducive to seed lodging and tree establishment, held 57.7%, including awning & ledge, roof top & edge taking the second largest share, and window sill & canopy. The stranglers scaled more vertical sites, whereas non-stranglers more horizontal. Root-shoot and root-biomass ratios reflected microhabitat controls. The findings were discussed vis-a-vis pre-adaptation of stranglers to vertical-habitat existence, enabling and restrictive microhabitat traits, plaster degradation as critical pre-condition, leap-frog succession and species paucity, analogy with rocky cliff habitat, and application to building-tree management.

Cave benthic invertebrates in south-eastern Brazil: are there 'key' factors structuring such communities?

The aim of this study was to determine the effects of microhabitat traits related to water quality and physical features of stream channels (substrate, channel morphology and hydraulic characteristics) on the richness and structure of the aquatic insect assemblage in cave streams. Sampling was conducted in three subterranean streams in Brazil. Aquatic insect richness was significantly and positively related to water depth and the presence of shelters for invertebrates. These shelters are directly related to channel heterogeneity, a factor that determined the surface area of habitats suitable for colonisation, refuges and the amount and variety of nutrients in streams where resources are extremely limited. Furthermore, analyses of community composition revealed that aquatic insect assemblages in each cave were structured by distinct factors (including physicochemical characteristics of the water or hydraulic features of the channel). Together, these findings highlight that different factors are responsible for structuring the assemblages in each cave, which may reflect their local variability, and that silting of cave streams would likely have deleterious effects on aquatic insect communities through reductions in overall habitat heterogeneity.

Contrasting annual cycles of an intratropical migrant and a tropical resident bird

Throughout their annual cycle, migrants often adopt different foraging and microhabitat usage strategies. Previous studies treat migrants as niche-trackers/niche-followers, i.e., they track similar niches along their annual cycle, almost exclusively based on food resource availability, which is inferred based on the climate at either the wintering or breeding grounds. An alternative approach is the use of such techniques as stable isotope analyses that allow researchers to more directly infer a migrant’s niche across seasons. While the use of carbon isotopes enables an assessment of microhabitat traits, that of nitrogen isotopes provides information on a bird’s trophic level. In the study reported here, we performed comparative analyses of stable carbon and nitrogen isotope ratios in tissues of the resident Plain-crested Elaenia and the intratropical migrant Lesser Elaenia to evaluate their year-round ecological niches. Our data suggest that both residents and migrants were consistent in their use of similar microhabitats throughout the year, which indicates a niche-tracking behavior on the part of migratory individuals. Migrants often fed at higher trophic levels than residents, but both species exhibited similar trophic level shifts through the year, feeding on higher trophic levels during breeding and on the lowest ones while wintering. The observed patterns could be due to several factors, including differential energetic demand needed for the migratory journey, species-specific nutritional needs during each stage of the year, and/or the use of multiple wintering grounds by migrants.

Spatial patterns of distribution and abundance of Harrisia portoricensis, an endangered Caribbean cactus

Aims The spatial distribution of biotic and abiotic factors may play a dominant role in determining the distribution and abundance of plants in arid and semiarid environments. In this study, we evaluated how spatial patterns of microhabitat variables and the degree of spatial dependence of these variables influence the distribution and abundance of the endangered cactus Harrisia portoricensis. Methods We used geostatistical analyses of five microhabitat variables (e.g. vegetation cover, soil cover and light incidence) and recorded the abundance of H. portoricensis in 50 permanent plots established across Mona Island, Puerto Rico, by the United States Department of Agriculture Forest Service as part of the Forest Inventory and Analysis (USDA–FIA). We also used partial Mantel tests to evaluate the relationships between microhabitat variables and abundance of H. portoricensis, controlling for spatial autocorrelation. Important findings Abundance of H. portoricensis showed strong affinities with microhabitat variables related to canopy structure, soil cover and light environment. The distribution of this cactus species throughout the island was consistent with the spatial variation patterns of these var iables. In general, landscape-level analyses suggested a predictive value of microhabitat traits for the distribution and abundance of this endangered species. For sensitive cacti species, wherein abundance may be influenced by similar variables, these types of analyses may be helpful in developing management plans and identifying critical habitats for conservation.

Habitat structure, soil properties, and food availability do not predict terrestrial flatworms occurrence in Araucaria Forest sites

Abstract Flatworm community structure responds strongly to large-scale habitat alteration, with low diversity in disturbed environments. However, the ecological factors influencing small-scale distribution of flatworms are poorly understood. The aim of this study is to test if the occurrence of land planarians is influenced by microhabitat traits. The study was developed in two Araucaria Forest sites located in the Sao Francisco de Paula National Forest, southern Brazil. In each site, a 0.5 ha grid subdivided in 10 m 2 plots, was established. In 100 randomly selected plots, the occurrence and abundance of each land planarian species were recorded. For each plot, we also recorded information on six habitat structural traits, 21 soils properties, and 15 prey availability parameters. Sixty-six specimens were recorded, belonging to 21 species of land planarians. Although the two areas differed in relation to 17 ecological factors analyzed, mean flatworm density did not significantly differ between the two studied areas. The pattern of their abundance followed a Poisson distribution, suggesting that flatworms were randomly distributed throughout the study area. Simple logistic regressions and a multiple logistic regression, controlled for spatial autocorrelation, showed no evidence that the occurrence of terrestrial flatworms is controlled by habitat structure, prey availability or soil properties. In addition, a Principal Component Analysis, controlled for spatial autocorrelation, generated three main axes that represented 40.7% of the variation of the 42 ecological traits. This analysis showed very similar distribution of plots with and without flatworms along these three axes. The results suggest that land flatworms exhibit no pronounced microhabitat preferences inside undisturbed Araucaria Forest sites.

Using visual cues of microhabitat traits to find home: the case study of a bromeliad-living jumping spider (Salticidae)

There are many examples of predators having specialized microhabitat requirements, but the sensory mechanisms by which predators detect, identify, and evaluate microhabitats are only poorly understood. The ability to use visual cues to select microhabitats was investigated using Psecas chapoda, a bromeliad-dwelling salticid spider. In this study, we manipulated real plants and photos of plants to test whether P. chapoda uses plant architecture to select host plants and whether visual cues alone are sufficient for them to select microhabitats. The use of photos on the experiment allowed us to exclude the potential influence of other cues, such as color and odor, on host plant selection by the spider. Our results showed that P. chapoda selects their microhabitat by evaluating architectural features of leaves and rosette of the host plants. Rosette-shaped plants (Agavaceae) were preferred over other types of plant architecture. Spiders showed a preference for photographs of rosette-shaped plants having narrow and long leaves, confirming that they can make these choices entirely on the basis of vision. These salticids can recognize and select microhabitats bearing specific architectural features, which possibly reflects an adaptation to choose microhabitats that are favorable to its survivorship. Copyright 2010, Oxford University Press.

Spatial variation in post-dispersal seed removal in an Atlantic forest: Effects of habitat, location and guilds of seed predators

Studies of post-dispersal seed removal in the Neotropics have rarely examined the magnitude of seed removal by different types of granivores. The relative impact of invertebrates, small rodents, and birds on seed removal was investigated in a 2,178 ha Atlantic forest fragment in southeastern Brazil. We used popcorn kernels (Zea maysdPoaceae) to investigate seed removal in a series of selective exclosure treatments in a replicated, paired design experiment that included forest understory, gaps, and forest edge sites. We recorded the vegetation around the experimental seed stations in detail in order to evaluate the influence of microhabitat traits on seed removal. Vertebrate granivores (rodents and birds) were surveyed to determine whether granivore abundance was correlated with seed removal levels. Seed removal varied spatially and in unpredictable ways at the study site. Seed encounter and seed use varied with treatments, but not with habitat type. However, seed removal by invertebrates was negatively correlated with gap-related traits, which suggested an avoidance of large gaps by granivorous ants. The abundance of small mammals was remarkably low, but granivorous birds (tinamous and doves) were abundant at the study site. Birds were the main seed consumers in open treatments, but there was no correlation between local granivorous bird abundance and seed removal. These results emphasize the stochastic spatial pattern of seed removal, and, contrary to previous studies, highlight the importance of birds as seed predators in forest habitats.

Roles of larval behaviour and microhabitat traits in determining spatial aggregations in the ascidian Pyura chilensis

The large edible ascidian Pyura chilensis Molina, 1782 is a sessile suspension feeder that occurs in intertidal and subtidal habitats along the Chilean and Peruvian coasts. In these habi- tats the species, although solitary, is commonly found in highly aggregated assemblages and is sel- dom isolated. The results of a study to determine whether the observed field aggregations could be explained by larval behaviour, microhabitat with quiescent hydrodynamics, or both, are reported. Our laboratory experiments showed that P. chilensis larvae have a short pre-settlement period when maintained in the presence of artificial substratum conditioned with adult conspecific extract. More- over, P. chilensis larvae tended to settle in shaded areas. In the control treatment without con- specifics, or in illuminated areas, low numbers of P. chilensis settlers were found. In a 5-armed radial maze, under still water and low seawater flow regimens, larvae of P. chilensis tended to swim toward and settle in chambers that contained water in which conspecific adults had been placed. In the field, we tested the hypothesis that larval settlement in P. chilensis differs depending on microhabitat traits such as water flow, mechanical disturbance and light intensity. We conducted quadrat sampling on low rocky platforms in contrasting microhabitats, such as around holdfasts of the kelp Lessonia nigrescens, kelp whiplash zones and between holdfasts. The majority of P. chilensis settlers were found on top of conspecific adults inhabiting shaded microhabitats and around kelp holdfasts. These results suggest that protected habitats and chemical cue-mediated larval response to waterborne conspecifics during the settlement period contribute to the formation of intertidal and shallow subti- dal aggregations of P. chilensis. Given that the edible ascidian P. chilensis supports an important small-scale fishery and hosts an important associated community of macro- and micro-invertebrates, we suggest that our results should be considered when determining fisheries regulatory and management practices for this species.