Spatial Niche Overlap Research Articles

Dominant species of cephalopods and their niche characteristics in offshore of northern South China Sea

To understand the relationships among dominant species of cephalopods in offshore nor-thern South China Sea, we examined the niche characteristics of these dominant species from both spatial and temporal dimensions using the index of relative importance (IRI), the niche breadth and overlap indices based on fishery resources data from the bottom-trawl survey for four seasons during 2014-2015. The results showed that five dominant species of cephalopods were recorded for four seasons, including Loligo edulis, L. chinensis, L. beka, Sepia esculenta, and L. duvaucelii. The first two species were shared by all seasons. Compared with historical data, the composition of dominant cephalopods species had changed. The cephalopods resource exhibited obvious temporal and spatial variations. Stock density was higher in the sea area extending from the southern Hainan Island to eastern Guangdong Province than that in Beibu Gulf. The seasonal variation was characte-rized by the largest in summer but the smallest in winter. The temporal and spatial niche analysis showed that there was inconsistent in the order between temporal and spatial niche breadths for domi-nant species. L. edulis (1.32) and L. chinensis (3.90) occupied the largest temporal and spatial niche breadths, respectively. The smallest of temporal and spatial niche breadths were shown for S. esculenta (0.98) and L. duvaucelii (2.04), respectively. Though the temporal niche overlap was numerically larger than the spatial niche overlap, both of them had higher values in interspecies among L. edulis, L. chinensis, L. beka, and the lower overlap for the species pairs between L. duvaucelii and other species. The result of correlation analysis suggested that niche breadth exhibited a significant negative correlation with variation in abundance on both temporal and spatial scales. The ecological niche could reflect the tempo-spatial changes of species resource, which enriched the traditional methods of fishery communities.

Can landscape heterogeneity promote carnivore coexistence in human-dominated landscapes?

Interspecific competition can limit species distributions unless competitors partition niche space to enable coexistence. Landscape heterogeneity can facilitate niche partitioning and enable coexistence, but land-use change is restructuring terrestrial ecosystems globally with unknown consequences for species interactions. We tested the relationship between landscape heterogeneity and carnivore co-occurrence in natural and human-dominated ecosystems to assess the landscape-mediated impacts of anthropogenic change on coexistence. We used boosted regression trees to model the distributions and co-occurrence of two competing forest carnivores, American martens and fishers, at two contrasting sites in the Great Lakes region, USA: a “natural” site largely devoid of human impacts and a “human-dominated” site with substantial development and a history of land-use change. We assessed the importance of climate and habitat variables for each species, measured spatial niche overlap, and quantified co-occurrence as a function of compositional (patch richness), configurational (landscape shape), and topographical (elevation range) heterogeneity per site. We observed significant differences in the effect of heterogeneity on co-occurrence between sites. The natural landscape exhibited little niche overlap and co-occurrence had a significant, positive relationship with heterogeneity. Conversely, the human-dominated site exhibited high niche overlap with variable effects of heterogeneity on co-occurrence. Elevation, snowpack, and development had strong, contrasting effects on marten and fisher distributions, suggesting that differential use of habitat and anthropogenic features facilitates coexistence. Heterogeneity can facilitate coexistence, but too much may undermine carnivore coexistence in human-dominated landscapes where habitat and space are limited. Moreover, future climate change will likely erode niche partitioning among martens and fishers, with particularly strong consequences for coexistence in human-dominated landscapes and at range boundaries.

Ecomorphological traits explaining the competition exclusion between Oryzias and mosqui-tofish

The theory of ecomorphology predicts that species with similar morphological traits can occupy similar ecological niche, which may cause competitive exclusion. To apply this theory into fish invasion ecology research is of significance for understanding the interaction between native and invasive species. Here, we compared the morphological difference between two native (Oryzias pectoralis, Oryzias curvinotus) and one invasive species (Gambusia affinis) to explore the competitive exclusion among them. The results showed that despite O. pectoralis and O. curvinotus were sympa-tric species, they varied in spatial distribution. Such a result supported the theory of ecomorphology, which predicts that two species with similar morphological traits might have strong competition. Moreover, their population density exhibited a significant negative relationship with that of G. affinis. The morphology of G. affinis and both Oryzias species were more similar when comparing to other fish in the assemblage. Results from the cluster analysis showed that G. affinis and Oryzias species were close in a branch, with extremely low spatial niche overlap between invasive mosquitofish and native Oryzias species. There was significant negative correlation between the population abundance of mosquitofish and Oryzias species. All the results suggested that mosquitofish led to population decline of both Oryzias species, due to the ecomorphological similarity. More studies are needed to better understand the mechanisms of G. affinis invasion in habitats of native Oryzias species.

Spatio-temporal niche of dominant shrimp species in the Zhongjieshan Islands Marine Protected Area, China

To understand the characteristics and living conditions of shrimp population in the Zhongjieshan Islands Marine Protected Area (MPA), according to the trawl survey data of the area in January, April, July and October 2018, we analyzed the spatio-temporal niche of dominant shrimp species based on the indices of relative importance, Shannon index, Pianka formula and Pearson correlation coefficient. The results showed that 16 shrimp species from 10 families and 13 genera were collected and identified. Palaemon gravier, Solenocera crassicorni, Alpheus distinguendus, Parapenaeopsis hardwickii and Alpheus japonicus were dominant species, belonging to four fami-lies and four genera. The temporal niche breadth of the dominant species varied greatly, while their spatial niche breadth was stable. The temporal niche breadth was significantly correlated with temperature suitability. The spatio-temporal niche breadth value of A. japonicus, the small shrimps, was highest. The temporal niche overlap value between P. hardwickii and S. crassicornis was the largest, indicating that the time synchronization was high and the seasonal competition was severe. There was a significant spatial niche overlap in all dominant species, indicating that the dominant species of shrimp had the same spatial homology, with strong regional competition. The spatio-temporal niche overlap value between P. hardwickii and P. gravieri was the largest, indicating that they had high similarities in physical and biological environment selecting, spawning and migratory habits, and fierce inter-specific competition. Our results could provide reference for the application of spatio-temporal niche of marine organisms.

A multi-scale, multi-species approach for assessing effectiveness of habitat and connectivity conservation for endangered felids

Habitat loss and fragmentation are major threats to global biodiversity. Felids, among the many taxa experiencing population declines and range contraction around the world, are known as ecologically and politically powerful levers in conservation programs. Many felids are wide-ranging, and therefore, identifying and conserving their core habitat patches and corridors is essential for developing an umbrella strategy for protecting co-existing species. We employed a multi-scale, multi-species approach to model habitat suitability and connectivity for six felids across Iran. We identified potential core habitats and corridors of movement. We also quantified the spatial niche overlap to estimate the most important variables of habitat selection within the guild. We evaluated the effectiveness of conservation areas in conserving habitats and connectivity. Our findings revealed that each species' habitat use was influenced in a scale-dependent manner by different sets of environmental variables. Core habitats of felids were mostly located in conservation areas. We identified a number of small core habitats for most felids outside conservation areas. Maintaining corridors and stepping stone habitat patches along corridors may be needed to facilitate movement of individuals, especially between habitat remnants in unprotected areas. Our study highlights the importance of considering multiple spatial scales in management and conservation of carnivores. Our analysis shows that habitat selection and connectivity predictions are both very sensitive to scale, and incorrect scale of analysis can result in incorrect inferences that may lead to dramatically inefficient or ineffective conservation actions.

Spatial niche partitioning among three small cetaceans in the eastern coastal area of Hokkaido, Japan

Spatial niche partitioning of marine mammals is thought to be caused by dietary differences. However, due to the difficulty involved with conducting simultaneous marine predator and prey distribution surveys at the same scale, marine mammals have not been studied alongside their prey distribution. To understand the spatial niche overlap between 3 small cetaceans observed in the eastern coastal waters of Hokkaido, Japan (Pacific white-sided dolphinLagenorhynchus obliquidens, Dall’s porpoisePhocoenoides dalli, and harbor porpoisePhocoena phocoena), and the mechanisms behind the differences in their distributions, visual and hydroacoustic surveys using a quantitative echosounder were concurrently conducted. A clear spatial niche overlap was observed between the Pacific white-sided dolphin and Dall’s porpoise, whereas the spatial overlap was moderate between the harbor porpoise and the other 2 species. In areas where Pacific white-sided dolphins were observed, potential prey was abundant in a shallower layer, at approximately 80-90 m depth. On the other hand, potential prey was more abundant in deeper layers in areas where Dall’s and harbor porpoises were observed. Water depth affected the potential prey abundance at all depth layers (0-300 m), as potential prey were more abundant in areas with a shallower water depth. Additionally, potential prey were more abundant in shallower layers (3-200 m) than in deeper layers (200-300 m), where the maximum water depth was 3000 m. The differences in spatial niche among Pacific white-sided dolphin, Dall’s porpoise, and harbor porpoise might cause their dietary differences, as they are epipelagic feeders, midwater feeders, and both epipelagic and midwater feeders, respectively.

Niches and interspecific association of dominant shrimp species in the offshore waters of southern Zhejiang Province, China

Based on data from November of 2015 (autumn), February (winter), May (spring), and August (summer) of 2016 in the offshore waters of southern Zhejiang Province, the relationships between major shrimps species were examined by niche breadth, niche overlap, variance ratio, chi-square test, association coefficient and species pair co-occurrence percentage. The results showed that temporal niche breadth of Atypopenaeus stenodactylu was the largest, spatial niche breadth of Solenocera crassicornis was the largest, and A. stenodactylu had the largest spatio-temporal niche breadth. The temporal niche overlap between Parapenaeus fissuroides and Parapenaeopsis tenella was the highest. The spatial niche overlap between Solenocera koelbeli and Penaeus chinensis, P. fissuroides and Heterocarpoides laevicarina were the highest. The spatio-temporal niche overlap between S. koelbeli and P. chinensis was the highest. The analysis of variance ratio showed that the main shrimp species were significantly positively correlated. Positive correlation existed in 13 pairs (χ2≥3.841). Results from the association coefficient (AC) and co-occurrence percentage (PC) indicated that the interspecific association tended to be positive. Our results provide supports for exploring niche breadth and niche overlap of major shrimp species and improving niche differentiation.

Sharing from the Same Bowl: Resource Partitioning between Sympatric Macaque Species in the Western Himalaya, India

Comparative studies of closely related species with similar ecological requirements are essential to understand the behavioral adaptations that allow them to live in sympatry. We investigated the mechanisms that enable the coexistence of two congeneric macaques—the Assamese macaque (Macaca assamensis) and rhesus macaque (M. mulatta)—in the Western Himalaya along the India–Nepal border in the State of Uttarakhand, India. For five months from December 2016, we collected scan samples of the behavior of one Assamese macaque group (N = 9975 samples) and two rhesus macaque groups (N = 14,402). Activity budget comparisons revealed that the former spent more time on feeding and the latter on resting and moving. Although the two species had 29 (37%) of 78 food items in common, only Mallotus philippensis and agricultural crops formed a major part of their shared diet (contributing to >1% of feeding scans). The Assamese macaque fed predominantly on leaves and had a broader niche than did the rhesus macaque, which fed mostly on fruits. We also observed differences in feeding schedules and feeding heights of the two species. The two species showed variation in home range, daily movement patterns, habitat use, and sleeping sites that need further investigation. The two species exhibited a lower dietary and spatial niche overlap in winter, a period of relatively low resource abundance than in spring. The observed differences in diet and space use suggest that the niches of the two macaques are separated in several dimensions, which may have promoted their coexistence in this region. Similar long-term studies across different habitats and seasons can improve our understanding of resource use by primates in sympatry.

Spatio-temporal variation and the use of host body surface by ectoparasites of the chelonians Phrynops geoffroanus and Mesoclemmys tuberculata in areas of the Caatinga and Atlantic Forest in northeast Brazil.

Ectoparasites such as hematophagous leeches and monogeneans are common in chelonians, occupying different parts of the body. Thus, the present study aimed to identify and describe the fauna of ectoparasites that infest Phrynops geoffroanus and Mesoclemmys tuberculata to evaluate the effect of host conditions and seasonality (dry and rainy season) on the abundance and composition of ectoparasites. We verified the presence of ectoparasites in 73.2% of the examined turtles, with four species of leeches belonging to Glossiphoniidae, Haementeria brasiliensis sensu Cordero, 1937, Helobdella cf. adiastola, Haementeria sp1., and Haementeria sp2., and one monogenean Polystomatidae, Polystomoides brasiliensis. For both chelonians, we observed a significant difference in the abundance of ectoparasites in relation to sex, biome, and season, which was unrelated to length and mass. Leeches were more frequent in the cavities of the hind limbs in P. geoffroanus, and the anterior limbs of M. tuberculata. The general spatial niche overlap of ectoparasites was high, except for that of the monogenean P. brasiliensis, which did not overlap with those of other leech species. The present study is the first report of the presence of H. brasiliensis and P. brasiliensis parasitizing M. tuberculata, and Helobdella cf. adiastola in a phoretic relationship with P. geoffroanus and M. tuberculata. Finally, the differences in infestation levels may reflect ecological factors, differences in behavioral patterns of the hosts, and different anthropic alterations suffered in the Caatinga and Atlantic Forest biomes.

Low genetic differentiation between two morphologically and ecologically distinct giant-leaved Mexican oaks

Quercus magnoliifolia and Q. resinosa are two Mexican white oak species that have been taxonomically reported to exhibit morphological similarities and possible hybridization. The objective of this study was to compare the variation in Q. magnoliifolia and Q. resinosa throughout their distribution range to identify the degree of species differentiation using morphological, ecological and genetic tools. Morphological analysis showed differentiation in leaf shape between the species corresponding to the taxonomical identification of Q. magnoliifolia and Q. resinosa in almost all cases, but intermediate individuals were identified in the middle of the species ranges. Comparison of ecological niche models for Q. magnoliifolia and Q. resinosa showed non-equivalent ecological niches, high climatic niche differences and low to moderate spatial and environmental niche overlap, mainly along the Trans-Mexican Volcanic Belt where morphologically intermediate individuals between species were more frequently located, suggesting recent hybridization by secondary contact. In contrast, we found low but significant genetic differentiation between Q. magnoliifolia and Q. resinosa and lower interspecific than intraspecific genetic differentiation, and Bayesian clustering analysis (K = 2) failed to assign each species to a unique genotype, suggesting shared ancestral variation as the cause of genetic similarity between species due to recent divergence. In conclusion, although neutral molecular markers do not distinguish the species Q. magnoliifolia and Q. resinosa, we found morphological and ecological differentiation between these oaks that provide preliminary evidence for divergent selection.

Space Partitioning among Two Sympatric Species, Sand Cat (Felis margarita) and Rüppell's Fox (Vulpes rueppellii), in a Desert Landscape in Central Iran

This study evaluates and compares habitat preferences and spatial niche breadth and overlap between two sympatrically occurring species, the sand cat (Felis margarita) and Ruppell's fox (Vulpes rueppellii), in a desert landscape of central Iran. A field survey from 2014 to 2016 was conducted to collect occurrence points for the two species as well as to identify their structural characteristics of used habitats in the occurrences points. Jacobs' index as a measure of habitat preference, Shannon and Levins' indices as measures of niche breadth, MacArthur, Levins and Pianka's indices as measures of niche overlap were calculated and interpreted. The results of this study showed that the sand cats are specifically restricted to sand dune and sabulous habitat type, whereas Ruppell's foxes have wider ecological amplitude. Sand cats only prefers sand dunes while Ruppell's foxes were found to prefer foothills, badlands, and sand dunes. Ruppell's foxes therefore had a wider niche breadth compared to the sand cats. The asymmetric MacArthur and Levins indices yielded a higher value of niche overlap for the sand cats compared to Ruppell's foxes, while the symmetric Pianka's measure of niche overlap was relatively high for both species. Such habitat preference and niche segregation between the two species may be a result of their feeding habits or the physical protective structure of their habitats attributes.

The Gray Toad-headed Agama, Phrynocephalus scutellatus, on the Iranian Plateau: The degree of niche overlap depends on the phylogenetic distance

The Gray Toad-headed Agama (Phrynocephalus scutellatus) occurs in Iran, Pakistan and Afghanistan and is represented in Iran by four distinctive genetic clades. We built distribution models for three of these clades (one clade was not included due to a low number of distribution records) using Maximum Entropy Algorithm in order to determine the contribution of ecological factors to the distribution pattern. The degree of spatial niche overlap between every pair of clades were measured using Schoener's D niche overlap metric. The results showed that at species-level climate variables (annual precipitation, annual mean temperature) were the most influential parameters determining the boundaries of the distribution in Iran. Temperature seasonality was found to be the most influential factor in the distribution of both Clade I and Clade II. However, this variable was replaced by the annual mean temperature for Clade VI. Based on the results of Schoener's D metric, Clades I and II had the lowest, and Clades II and VI the highest level of ecological niche overlap. Comparing the result of niche overlap with genetic distance between the clades, it was found that the ecologically least similar clades were those with the longer history of genetic segregation.

Earthquake-Related Changes in Species Spatial Niche Overlaps in Spring Communities

Species interactions between stygobites (obligate groundwater organisms) are poorly known, reflecting the difficulty in studying such organisms in their natural environments. Some insight can be gained from the study of the spatial variability in microcrustacean communities in groundwater-fed springs. Earthquakes can increase hydraulic conductivity in the recharge area of karstic aquifers and flow rates in discharge zones, thus dislodging stygobites from their original habitats to the spring outlets. Earthquakes are expected to alter species spatial niche overlap at the spring outlets, where stygobites coexist with non-stygobites living in benthic and subsurface habitats. We compared the abundance of stygobiotic and non-stygobiotic microcrustaceans in groundwater-fed springs before and after the 6.3-Mw earthquake that hit the karstic Gran Sasso Aquifer (Italy) in 2009. Pre-seismic (1997, 2005) overall niche overlaps were not different from null expectations, while post-seismic (2012) species mean niche overlaps were higher, following the redistribution of animals caused by the earthquake-triggered discharge. The reduced abundance of stygobites following their dislodgement from the aquifer and the concomitant displacement of non-stygobites led to a higher post-seismic co-occurrence of stygobites and non-stygobites. Changes in aquifer structure destroyed pre-seismic species segregation patterns by creating new or strengthening already existing interactions.

Climatic effects on population declines of a rare wetland species and the role of spatial and temporal isolation as barriers to hybridization

Summary Climate change and climatic extremes may affect species directly or indirectly. While direct climatic effects have been intensively studied, indirect effects, such as increasing hybridization risk, are poorly understood. The goal of our study was to analyse the impact of climate on population dynamics of a rare habitat specialist, Chorthippus montanus, as well as the fine‐scale spatial overlap with a sympatric habitat generalist, Chorthippus parallelus and the dispersion of hybrids. We were particularly interested in the role of spatiotemporal overlap on heterospecific encounter frequencies. We conducted high‐precision mark‐recapture studies on two sites over 7 years and genotyped 702 individuals of two C. montanus generations to detect hybrids. We tested the performance of three programs (structure, newhybrids and adegenet) and accepted only hybrids detected by the two best performing programs. We then tested for correlations between yearly population trends and climatic variables. Furthermore, we analysed the spatial dispersion of both taxa and the hybrids to calculate variation in spatial and temporal overlap and infer heterospecific encounter probabilities. Our results revealed that droughts during the egg phase and rainy weather during nymphal development were strongly correlated with population declines in the habitat specialist. The highest hybridization rate (19·6%) was found in the population with lowest population size. The combined effects of spatial and temporal niche overlap decreased heterospecific encounter probabilities to 4·2–7·6% compared to 20–28% and 11–19% calculated alone from phenology or spatial overlap respectively. Hybrids were detected in areas of higher heterospecific encounter probability, mainly at the edge of the specialists’ occupied habitat in areas with intermediate soil moisture conditions compared to the parental species. This illustrates that the combination of spatial and temporal segregation provides an effective barrier to hybridization. However, the high hybridization rate in one of the populations suggests that this function may decrease with decreasing population size. This supports the hypothesis that climatic extremes threaten rare species directly by reducing reproductive success and may indirectly increase hybridization risk. A lay summary is available for this article.

Ecological niche partitioning within a large predator guild in a nutrient‐limited estuary

AbstractWithin oligotrophic ecosystems, resource limitations coupled with interspecific variation in morphology, physiology, and life history traits may lead to niche partitioning among species. How generalist predators partition resources and their mechanisms, however, remain unclear across many ecosystems. We quantified niche partitioning among upper trophic level coastal and estuarine species: American alligators (Alligator mississippiensis), bull sharks (Carcharhinus leucas), common bottlenose dolphins (Tursiops truncatus), common snook (Centropomus undecimalis), and Atlantic tarpon (Megalops atlanticus) in the Shark River Estuary of the Florida Coastal Everglades, USA using acoustic telemetry, stable isotope analysis, and visual surveys, combined with published diet and life history demographic information. Spatial and isotopic niche overlap occurred among most species, with variability in partitioning among interspecific interactions. However, seasonal variability in habitat use, movements patterns, and trophic interactions may promote coexistence within this resource‐limited estuary. Beyond guild‐level niche partitioning, predators within the Shark River Estuary also exhibit partitioning within species through individual specializations and divergent phenotypes, which may lead to intraspecific variability in niche overlap with other predators. Niche differentiation expressed across multiple organizational levels (i.e., populations and communities) coupled with behavioral plasticity among predators in oligotrophic ecosystems may promote high species diversity despite resource limitations, which may be important when species respond to natural and human‐driven environmental change.

Tall Grass Invasion After Grassland Abandonment Influences the Availability of Palatable Plants for Wild Herbivores: Insight into the Conservation of the Apennine Chamois Rupicapra pyrenaica ornata

Invasion of the tall grass Brachypodium genuense was observed in an area of the central Apennines (Italy) where the population size of Apennine chamois (Rupicapra pyrenaica ornata) was in strong decline. Since this dominant tall grass threatens biodiversity and forage quality, our hypothesis was that B. genuense abundance influenced that of palatable species for the chamois, depending on their functional traits and distribution patterns. Our sampling design used plots of 10×10m and 1×1m to investigate the plant community level and fine-scale interactions. We analyzed data using correlation, generalized linear models, and redundancy analyses. We found that B. genuense can reach high abundance values on the deepest soils. Its high cover value influences plant community composition by competitive exclusion of subordinate species and suppression of functional features because of temporal or spatial niche overlap. This leads to low cover of palatable species at a fine scale, and to poor pasture quality for chamois at a wider scale. Therefore, we postulated that B. genuense invasion, enhanced by long-term grazing cessation, may reduce the availability of palatable plants for Apennine chamois, especially below the potential timberline (1900-2000m a.s.l.). The high abundance of B. genuense may amplify the effect of other negative factors, such as competition with red deer (Cervus elaphus) and climate change, in restricting the suitable habitat of the Apennine chamois to the higher sectors of the central Apennines. Thus, we suggested that B. genuense spread should be monitored carefully and plans to control its invasion should be implemented.

Resource Partitioning and Niche Overlap in Three Sympatric Species of Dragonflies (Anisoptera Libellulidae) in Anuradhapura District, Sri Lanka

Resource partitioning in ecological communities bears profound connection with the coexistence of closely related species. As a mechanism, it assists species with similar characteristics to thrive in the environments where they can utilise resources in different levels in spatial and temporal scale via niche partitioning. As ecologically important insects, dragonflies are well-studied in many aspects globally but poorly assessed locally. The current study was conducted under the main objective of identifying the mechanism of resource partitioning in three sympatric most common skimmer species; Brachythemis contaminata , Crocothemis servilia servilia and Rhyothemis variegata variegata in two tank ecosystems in Anuradhapura district, Sri Lanka. The study was conducted from May-August 2014 simultaneously in Nabadagaswewa tank (NW) and Mihintale tank (MT). Data collection was carried out 08:00 to 10:00 hrs in the morning and 13:00 to 15:00 hrs in the evening. Land-water interface at the tank was used for the study in both sites. Scan sampling was used to obtain data on resource utilisation by the three skimmer species. Randomly selected individuals were observed for 30 seconds in each observation point. Vegetation variables (bank vegetation density and height, aquatic vegetation density and height) were measured using two belt transects (25×1 m2) in both habitats. The three species were more active in the morning hours (08:00 to 10:00 hrs) and shows different levels of perch and fly heights in the morning and evening hours. R.v. variegata was recorded using heights of <100 cm in both habitats. B. contaminata and C.s. servilia showed high spatial niche overlap (Oij=0.716) in NW and in MT highest spatial niche overlap was observed between C.s. servilia and R.v. variegata (Oij=0.473). The broadest niche breadth was exhibited by C.s. servilia (B=0.46) in NW while B. contaminata showed the highest (B=0.23) in MT. R.v. variegata showed the lowest niche breadth in both habitats (NW: B = 0.39, MT: B=0.09). Relationship between the species abundance and vegetation heights and densities shows that vegetation height and bank vegetation densities were negatively correlated with the abundance of the three skimmer species. This study depicts ways of resource partitioning among the three sympatric skimmer species minimising interspecific competition and favoring their co-existence. Further, it highlights the extent of spatial niche overlap is influenced by the habitat characteristics especially the vegetation structure and resource availability. Keywords: Resource partitioning, Niche overlap, Libellulidae

Microdistributions of stoneflies of the High Tatra montane streams

Abstract Stonefly samples were collected from disturbed and undisturbed tributaries of the Tatra Mountains streams (the West Carpathians). In the autumn, at stable low discharge, the total density of stoneflies was significantly higher in the undisturbed streams. Microhabitats such as macrolithal (boulders), mesolithal (stones) and moss had higher stonefly density. Taxa of different species or genera have different demands for microhabitats. Very narrow spatial niches were found for the genera Rhabdiopteryx, Protonemura and Perlodes. The spatial niche overlap was low between the genera Rhabdiopteryx and Brachyptera, but was high between species of the Protonemura and Leucra genera. The highest biodiversity of stoneflies was on coarser substrata (except boulders) and moss, the lowest biodiversity was on the finer substrata. Among the organic substrata, a significantly lower coefficient of stonefly α-diversity variation was recorded in mosses compared to submerged wood and roots.

Population structure of a native and an alien species of snail in an urban area of the Atlantic Rainforest

Native Megalobulimus paranaguensis was identified on Brazil’s Ilha Porchat promontory, an area that Achatina fulica commonly populates. The population structures of these species were investigated for interactions. Spatial distribution, niche overlap and mark–recapture analysis were conducted. The outer lip of M. paranaguensis and environmental variables were measured. One and two abundance peaks were observed for A. fulica and M. paranaguensis, respectively. Survivorship was higher in A. fulica. Distribution was aggregate for M. paranaguensis, whereas for A. fulica it varied from random to aggregate. Both species aggregate as abundance increases. The lifespan of M. paranaguensis in this location is shorter than its lifespan in a nearby location. Achatina fulica was affected by soil temperature and humidity; M. paranaguensis was influenced by humidity. Niche overlap was random. The results show that M. paranaguensis can keep its natural activity and abundance in the presence of A. fulica, but environmental degradation impacts M. paranaguensis and should be evaluated.

Trophic and spatial niche of five gobiid fishes in Jiaozhou Bay

The food composition,spatial and trophic niche width,trophic-spatial niche overlap for five gobiid fishes in Jiaozhou Bay were studied using the Shannon-Wiener index and Pianka overlap index.The trophicspatial niche overlap was calculated to describe the relationship between feeding competition and spatial distribution of these gobiid fishes.Results showed that all the five gobiid fishes could be classified as benthic carnivorous predators.Synechogobius ommaturus fed mainly upon shrimps,polychaetes and fish.The main prey items of Amblychaeturichthys hexanema,Odontamblyopus lacepedii,Tridentiger trigonocephalus and Tridentiger barbatus were some small benthic crustaceans such as copepods,amphipods and cumacea.Among the five gobiid fishes,A.hexanema had the highest trophic niche width value(2.65) and T.trigonocephalus had the highest spatial niche width value(2.01).O.lacepedii had the lowest values of trophic niche width(1.26) and spatial niche width(0.97).The trophic niche overlap values for five gobiid fishes ranged from 0.03 to 0.64,with A.hexanema and T. barbatus having the highest trophic niche overlap value(0.64).The spatial niche overlap values were between 0.08 and 0.91,with O.lacepedii and T.barbatus having the highest spatial niche overlap value(0.91).The trophicspatial niche overlap values ranged from 0.003 2 to 0.364 8,with A.hexanema and T.barbatus having the highest trophic–spatial niche overlap value(0.3648),which may result in intensive food competition.The competitions among other gobiid fishes were reduced by partitioning of trophic and spatial niches.