Patterns of food and microhabitat resource use by two benthic gobiid fishes

The mechanisms responsible for different patterns of habitat use by two benthic gobiid fishes, Acentrogobius sp. 1 and A. sp. 2, which displayed identical food use but resided in shallow and deep zones of coarse and fine sediments, respectively, in Lake Hamana, Shizuoka Prefecture, Japan, were investigated by field removal and laboratory sediment-grain size selection experimentation. Following field manipulation, involving removal of both species, the distribution patterns of each were found to be similar in both control and manipulated quadrats, suggesting their differential habitat use patterns may be the outcome not of competition but of differing preferences for habitat characteristics. Results of a sediment-grain size selection experiment in the laboratory suggested a weak preference of A. sp. 2 for fine sediment, while A. sp. 1 showed no grain size preference. The observed difference in the distribution patterns between these two species, therefore, may possibly have resulted from, at least in part, a combination of differences in their preference for sediment grain size and other habitat characteristics such as water depth.     

Spatio-temporal microhabitat use by two co-occurring species of scorpions in Atlantic rainforest in Brazil

With the increasing devastation of the tropical rain forest, there is a critical need to understand how animal forest communities are structured and how habitat degradation will affect these communities. We conducted a field survey to investigate the microhabitat preferences of two co-occurring species of scorpions (Tityus pusillus and Ananteris mauryi) in a fragment of Atlantic rainforest, as well as their abundance and their ecological niche, during both the dry and rainy seasons. Behavioural aspects related to the use of the environment and the proportions of juveniles and adults are also described. The occurrence of intra- and interspecific coexistence was assessed by active search. In addition, pitfall catches were used to assess the structure of the population in the dry and rainy seasons. The differential patterns of spatial distribution in the litter layers provided evidence of partial niche partitioning between the two coexisting scorpion species depending on age and climatic conditions. Abundance, foraging behaviour and age structure (juveniles and adults) were seasonally influenced. We conclude that the diverse and subtle behaviours involved in interaction and habitat use may facilitate species coexistence. Resource partitioning and refuge sharing on a temporal and/or spatial scale, as well as predation pressure, may drive the dynamics and spatial distribution of scorpion species in the rain forest environment.     

Microhabitat segregation in two desert rodent species: the relation of prey availability to diet

Summary I studied diet in relation to microhabitat use in two desert rodents:Microdipodops megacephalus, the dark kangaroo mouse, andPeromyscus maniculatus, the deer mouse. Contrary to expectation, both species ate primarily arthropods, which were most abundant near shrubs.Peromyscus used the area near shrubs, in contrast toMicrodipodops, which used open microhabitat. As a consequence, the diet ofPeromyscus was narrower and more concentrated on abundant prey types than that ofMicrodipodops. Thus microhabitat segregation, which is frequently reported for desert rodents, is related to a diet-breadth difference between these rodents. The use of open microhabitat and low density resources byMicrodipodops, when compared with the large bipedalDipodomys and small quadrupedalPerognatus, suggests that bipedal locomotion in desert rodents is related to use of open microhabitat, and that body size is related to density of food resources.     

Distribution patterns of four Orthoptera species in relation to microhabitat heterogeneity in an ecotonal area

Microhabitat heterogeneity is considered to be one of the main factors affecting the structure and diversity of natural communities. This study evaluated: (i) whether it is possible to associate the distribution of four orthopteran species with small-scale spatial microhabitat heterogeneity based on floristic composition; and (ii) whether interspecific differences exist in microhabitat was among the different orthopteran species over a gradient of vegetation succession induced by abandonment of meadows. Orthoptera and plant species were sampled on 72 plots across an ecotonal area on Monte Bondone in the Southern Italian Alps. Microhabitats were identified based on grassland and undergrowth vegetation composition and by classifying sample plots using cluster analysis. Eight microhabitats were identified, each corresponding to a separate successional stage, and microhabitat use by each species was assessed. The distribution of orthopteran species revealed a different use of microhabitats. Species also had differing patterns of distribution, and a shift in distribution occurred following a change in microhabitat structure caused by mowing. The importance of the maintenance of a mosaic of microhabitats, with differently managed adjacent areas is discussed.     

Patterns of microhabitat and larval host-plant use by an imperiled butterfly in northern Florida

The quality of habitat for a given species is fundamental to its persistence in that habitat space. Herbivorous insects often require a specific combination of host plants, floral resources, and physical features such as shelter. Identifying these different habitat features is a focus of ecology and conservation, particularly for managing rare or imperiled taxa. We investigated the patterns of microhabitat and host plant use of the rare frosted elfin butterfly, Callophrys irus, a larval host-plant specialist found in frequently disturbed sand plains, barrens, and sandhill pine-oak forests of the eastern United States. Previous studies have been conducted on populations in the Northeastern and Midwestern US, but the southern part of its range remains unstudied. Our efforts focused on a persistent C. irus colony in northeastern Florida, resulting in a geographically referenced census of larval host-plant Lupinus perennis, along with a multiple year survey of microhabitat features relevant to both C. irus adults and immatures. Results of the larval host-plant census revealed that the highest densities of host plants were located distant to the highest densities of C. irus. Hot-spot analysis confirmed the significance of this pattern, suggesting different habitat requirements for larval host-plant L. perennis and C. irus individuals in order to achieve maximum potential densities. Our survey of C. irus immatures showed a similar pattern of microhabitat affinity that was previously recorded in the Northeast and Midwestern US, including large larval host-plants, low amounts of ground cover vegetation, and the presence of some shade. Unique to our study we found that the presence of other herbivores of L. perennis such as larvae of the crambid moth Uresiphita reversalis had a negative effect on encountering C. irus immatures. Our results suggest that management that aims to conserve these species needs to include habitat factors that favor the overlap of these species and to consider where their densities are the highest.     

Interspecific differences in microhabitat choice by two species of Australian reptile tick

The microhabitat choice of all life cycle stages, both unfed and engorged, of two Australian ixodid ticks, Amblyomma limbatum and Aponomma hydrosauri, were compared in the laboratory. When offered a choice between bare soil (or sand) and soil covered with litter, most ticks moved into the litter, except unfed larvae which often took refuge within crevices on the surface of exposed sand. The two species differed in the position they adopted within the litter. Ap. hydrosauri were predominately found at the interface between the soil and litter. Amb. limbatum were more often found higher up in the litter. There were also interspecific differences in the body orientation of ticks within the litter. All life cycle stages of Ap. hydrosauri adopted a position with their dorsal surface facing upwards, whereas unfed stages of Amb. limbatum were more frequently found with their ventral surface facing upwards. The behaviour of each species probably represents a different compromise between two factors, maximizing host detection, and minimizing their exposure to desiccation or predation.     

Plant diversity in paddy fields in relation to agricultural practices in Savannakhet Province, Laos

This paper reports a study of paddy vegetation in central Laos. Plants were inventoried and vegetation types classified. Relationships between vegetation and agricultural practices were identified. A total of 184 wild herbaceous species and 17 cultivated species were recorded in two villages. Of the wild species, 19 were used by local people, four were rare species, and three were major weeds. Paddy vegetation was arranged in order of water regime from shorter to longer hydroperiod by DCA. The factors contributing to high species diversity were: (1) the presence of species unique to different paddy types; (2) the presence of remnant species from original vegetation; and (3) the impact of agricultural practices. Thus, at this study site, multiple plant species coexisted in paddy fields under various agricultural practices, and some species were essential sources of food or were used in other ways to support the subsistence livelihoods of local residents.     

Patterns of floral resource use by two dominant ant species in a biodiversity hotspot

Ecological dominance in ants is often fuelled by carbohydrate intake. Most studies have focused on the importance of invasive ant mutualistic associations with trophobionts whereas few studies have investigated the importance of floral nectar on invasion success. In this study, utilisation of temporarily available floral nectar by the invasive Argentine ant, Linepithema humile, was compared to that of the dominant native ant, Anoplolepis custodiens, within the Cape Floristic Region (CFR), a biodiversity hotspot. The effect of these two focal ant species on species composition and abundance of ground foraging ants as well as floral arthropod visitors in inflorescences of Proteacea species was assessed. Foraging activity, and trophic ecology inferred from the abundance of natural stable isotopes of Carbon (δ¹³C) and Nitrogen (δ¹⁵N), and the ratio of Carbon to Nitrogen (C:N) were compared between the two ant species during three flowering periods. Linepithema humile significantly reduced the abundance and species diversity of both above-ground and floral arthropod species abundance and composition. Linepithema humile increased its foraging activity with increasing nectar availability, switching its diet to a more herbivorous one. Anoplolepis custodiens did not respond as effectively to increasing floral nectar or negatively impact floral arthropod visitors. This study showed that the availability of floral nectar and ability of L. humile to more effectively utilise this temporarily available resource than native ants, can contribute significantly to the further spread and persistence of L. humile in natural environments in the CFR.     

Coexistence of similar species: evidence of a resource and microhabitat sharing in two intertidal hermit crab species

Hydrobiologia - Theory predicts that species can only coexist if they are sufficiently different in their resource and/or microhabitat utilization; if their needs are too similar, the stronger...     

不同栖息环境的两种啮齿动物Vkorc1基因多态性

维生素K环氧化物还原酶复合物亚基1基因(Vkorc1)的变异与啮齿动物对抗凝血灭鼠剂的抗药性密切相关。为掌握Vkorc1基因变异在野栖类和家栖类啮齿动物中的流行情况,从山西省13个县(市、区)的农田和14个县(市、区)的养殖场采样,检测长尾仓鼠(Cricetulus longicaudatus)和黄胸鼠(Rattus tanezumi) Vkorc1基因编码区的变异位点及携带不同变异位点的个体的分布情况。结果显示,长尾仓鼠在13个采样地均有捕获,整体占野栖类啮齿动物的23.29%;黄胸鼠分布于8个采样地,整体占家栖类啮齿动物的68.63%。在长尾仓鼠样本(n=105)中检测到6个沉默突变位点和5个错义突变位点,其中,沉默突变C438T (His146His)的变异率最高,为67.62%;共有17只长尾仓鼠样本存在错义突变位点。黄胸鼠样本(n=70)中存在6个沉默突变位点和1个错义突变位点,其中,最常见的沉默突变位点A321C (Ile107Ile)和T411C (Thr137Thr)的变异率均达到18.57%;8只黄胸鼠样本存在与其抗药性相关的A416G (Tyr139Cys)错义突变...     

Size and shape variability in relation to species differences and climatic gradients in the African rodent Oenomys

Aim The modern African murine rodent Oenomys is a semiarboreal genus characteristic of the rain forest zone. The size and shape geographical differentiation is studied in order to discuss the possible evolutionary patterns and constraints leading to this distribution. Location Two species of Oenomys have been previously recognized, corresponding to the West African forest block on the one hand and to the main forest block on the other hand. Both species have been sampled, and forty localities permit the study of the whole geographical range of Oenomys, from Guinea to Kenya. Methods A Fourier analysis applied to the outlines of the first upper and lower molars allows a quantification of the size and shape variations across the geographical range of Oenomys. Results This morphometrical analysis defines three morphological groups of Oenomys, corresponding to the West, Central, and East African forest zone. This result suggests the existence of an additional cryptic species. The Western group is characterized by broad asymmetrical molars and a small size. The Central African group has more elongated and larger molars while the Eastern African group displays extremely constricted molars and a small size. Main conclusion The shape can be considered as charactheristic of each group and its variations appear to be mostly related to phylogeny while size exhibits variations within each group related to climatic gradients. This discrepancy could be related to different genetic determinants for both characters, the shape being strongly genetically constrained while size can vary according to a wide range of environmental factors.     

Ovarian cycles and microhabitat use in two species of topminnow, Fundulus olivaceus and F. euryzonus, from the southeastern United States

Synopsis Differences in spawning seasonality, inferred from ovarian cycles, and microhabitat use for two closely related Fundulus species were not effective as potential reproductive isolating mechanisms. Seasonal spawning periodicity of F. olivaceus and F. euryzonus as shown by changes in mean egg diameter and mean number of mature eggs recovered from ovaries showed nearly identical temporal patterns in reproductive activity. Peak egg development was between April and May and was lowest by the end of August. Univariate comparisons of 11 environmental variables associated with aggregations of Fundulus spp. revealed highly significant differences in several of these variables. However, individuals of both species were frequently collected together, and microhabitat differences did not remove the potential for mismating.     

Patterns in the local assembly of Egyptian rodent faunas: Areography and species combinations

We implicate ecological processes in assembly patterns of Egyptian desert rodents using spatial variation of distribution and composition of local assemblages. We also compare our assemblages to prior analyses of North American and Australian small mammal communities in terms of species richness and representation of trophic groups.We studied patterns of occurrence of 29 rodent species among 335 collecting events in 308 sites using museum specimen records resulting from a country-wide survey. The studied taxa vary greatly in their natural histories and ecology. Fully 69% of studied species (20) were localized in 30 or fewer sites (9% of all sites). Site incidence was closely correlated with the geographic range size of species, while local abundance of a species showed little relationship to its geographic range. The species richness of local assemblages ranged from a lone species at 73 sites to 11 species at 3 sites. A total of 214 different combinations were recorded of which 164 (77%) were unique to a single site. G. gerbillus was both the most abundant and most ubiquitous species. Coexistence with other species was positively correlated with incidence and geographic range size. Body mass distribution was remarkably uniform for the fauna as a whole, and influenced the geographic distributions and abundance of individual species.Our sites have low species richness and substantial variability in species composition, which also characterize desert rodent communities elsewhere. Habitat requirements, exclusive distributions of sibling species, low primary productivity, and Egypt's location all influenced species assembly. The Egyptian and Australian deserts supported higher proportions of low richness assemblages compared to North America. As in North America, Egyptian sites were dominated by granivorous species.     

Patterns of plant species richness in relation to different environments: An appraisal

Abstract. We review patterns of plant species richness with respect to variables related to resource availability and variables that have direct physiological impact on plant growth or resource availability. This review suggests that there are a variety of patterns of species richness along environmental gradients reported in the literature. However, part of this diversity may be explained by the different types and lengths of gradients studied, and by the limited analysis applied to the data. To advance in understanding species richness patterns along environmental gradients, we emphasise the importance of: (1) using variables that are related to the growth of plants (latitudinal and altitudinal gradients have no direct process impact on plant growth); (2) using multivariate gradients, not single variables; (3) comparing patterns for different life forms; and (4) testing for different shapes in the species richness response (not only linear) and for interaction between variables.     

Microhabitat use by rodent species in a central Brazilian cerrado

We analysed microhabitat use by the rodents Calomys tener, Necromys lasiurus and Thalpomys lasiotis and the factors that may influence their abundances in “murundu” grasslands (open fields with termite mounds) at Aguas Emendadas Ecological Station, Planaltina, Federal District, Brazil. Two grids with 100 sampling points were established and traps were placed at each intersection of the grid, where five microhabitat variables were also measured. Rodents were trapped from June through October 2008. Microhabitat explained 21% of the variation in community structure, with grass density and the number of termite mounds explaining most of the variation. Necromys lasiurus was most often captured in areas with dense grasses, whereas T. lasiotis and C. tener were most often in areas less dense with grasses.     

Environmental issues in relation to agricultural practices and attitudes of farmers: A case study from Saudi Arabia

PurposeThe Kingdom of Saudi Arabia is continuously in search of environment-friendly farming practices since mass-scale agriculture was initiated. It is imperative to gauge to the level of awareness of the farmers on the agricultural practices causing environmental issue in order to devise new agricultural extension programs. This research aims to identify the attitudes of farmers towards agriculture and environment in Al-Ghat area of Saudi Arabia.MethodologyA simple random sample of 110 farms truly representing the farming community was drawn to meet the objectives of the study. Data were collected by using the pre-tested questionnaire during the face-to-face interviews. In order to understand the message of study, data were analyzed for percentages, arithmetic average and standard deviation in addition to the simple Pearson correlation coefficient.ResultsThe results showed that the high proportion (87.3%) of farmers was interested in continuing to work farm and 77.3% of farmers did not consider adopting agriculture their main occupation. The findings of the survey reveal that some 55.5% of the respondent farmers were aware of the agricultural practices and their relation to the environment. Some 57.3% of the surveyed farmers are aware of potential benefits of enhanced utilization of agricultural organic wastes. However, main profession, farm employment (as the independent variables) showed a significant positive correlation with the attitudes of farmers towards their working in agriculture (as a dependent variable). Also a significant negative relationship between the educational levels and the attitudes of the farmers towards working in agriculture was noticed. The study also indicated a significant correlation between education and the degree of awareness of agricultural practices related to the environment and maximizing the optimum utilization of agricultural waste i.e. organic residues.ConclusionsThe study suggested the need for new awareness and orientation programs to educate farmers and extension workers, highlighting the environment- friendly agricultural practices.Recommendation: There is need to offer incentives and facilities to keep the farmers stay in the farming business. Extension staff must keep educating them on beneficial features of organic farm waste and crop residues as organic fertilizers.     

Patterns of species richness in dry grassland patches in an agricultural landscape

Eighty-five patches of semi-natural grassland of varying size scattered in a agricultural landscape were investigated for their flora of vascular plants. Relationships between species richness and patch area, spatial isolation and local habitat conditions including heterogeneity were examined. Differences between single species and among groups of species defined by life-history traits were also investigated.
Area was shown to be an important determinant of species richness irrespective of habitat heterogeneity. Isolation in space and habitat heterogeneity also play significant roles. These results are consistent with results from a multitude of studies on fragments of ancient deciduous woodland in northern Europe, They are, however, contradictory to results from previous studies in grasslands within the same region. Seed mass and dispersal syndrome were poor predictors of the degree to which the species were affected by isolation of grassland patches. Seed mass deviation from community median could explain a small percentage of the variation in regional abundance. Logistic regression on species occurrences showed that few species are associated with large patches, and less than half seem to avoid isolated patches.