Pulsed resource availability changes dietary niche breadth and partitioning between generalist rodent consumers

Identifying the mechanisms that structure niche breadth and overlap between species is important for determining how species interact and assessing their functional role in an ecosystem. Without manipulative experiments, assessing the role of foraging ecology and interspecific competition in structuring diet is challenging. Systems with regular pulses of resources act as a natural experiment to investigate the factors that influence the dietary niches of consumers. We used natural pulses of mast‐fruiting of American beech (Fagus grandifolia) to test whether optimal foraging or competition structure the dietary niche breadth and overlap between two congener rodent species (Peromyscus leucopus and P. maniculatus), both of which are generalist consumers. We reconstructed diets seasonally over a 2‐year period using stable isotope analysis (δ¹³C, δ¹⁵N) of hair and of potential dietary items and measured niche dynamics using standard ellipse area calculated within a Bayesian framework. Changes in niche breadth were generally consistent with predictions of optimal foraging theory, with both species consuming more beechnuts (a high‐quality food resource) and having a narrower niche breadth during masting seasons compared to nonmasting seasons when dietary niches expanded and more fungi (a low‐quality food source) were consumed. In contrast, changes in dietary niche overlap were consistent with competition theory, with higher diet overlap during masting seasons than during nonmasting seasons. Overall, dietary niche dynamics were closely tied to beech masting, underscoring that food availability influences competition. Diet plasticity and niche partitioning between the two Peromyscus species may reflect differences in foraging strategies, thereby reducing competition when food availability is low. Such dietary shifts may have important implications for changes in ecosystem function, including the dispersal of fungal spores.     

MULTIDIMENSIONAL ANALYSIS OF RESOURCE UTILIZATION IN ASSEMBLAGES OF RANGELAND GRASSHOPPERS (ORTHOPTERA: ACRIDIDAE)

Abstract  A study was conducted in a typical steppe area in central Inner Mongolia to determine resource utilization in time, space, and food by grasshopper assemblages. Pattern of use for these resources was analyzed from three vegetation types by examining species-specific niche breadths, overlaps and partitions of resource utilization as well as population sizes. Popular niche indices and the principal components analysis (PCA) procedure were used to indicate the interrelations among grasshopper species. In the heterogeneous grassland environments resulting from livestock grazing, eleven grasshopper species were categorized respectively based on the 3-dimensional niche segregation and overlap degree. Population sizes were determined by the calorific values of their realized population biomass. Comparison in niche breadth displayed that species which had a broad niche along one dimension at least had a narrow niche along another one. There were sufficient differences between species for overall overlap associated with resource use to explain coexistence in the assemblages by resource segregation. Distinct rule of niche complementarity in overlap was not found. Evidence from this study implied that the species-specific use of resource may be due primarily to grasshopper adaptive differentiation and to coevolutionary interactions between grasshopper and plant rather than interspecific competition among grasshopper species.     

草原蝗虫种团资源利用的多维分析(直翅目:蝗科)(英文)

本文研究了内蒙古典型草原蝗虫在时间、空间和食物资源利用方面的特点。对于这些资源利用的格局是通过对存在于三种类型植被中蝗虫种的生态位宽度、资源利用的分化和重叠以及每种蝗虫的种群大小来分析的。常用的生态位指数和主成份分析技术用来阐明蝗虫种间的关系。在放牧形成的异质性草原环境中,11种蝗虫根据它们在三维生态位方面的分化和重叠程度被划分成数个种组。种群的大小是根据种群实际生物量所含热能值来确定的。生态位宽度比较说明,在某一维生态位宽的种,在另一维上必定变窄。生态位重叠的差异说明共存的蝗虫种在资源利用上的分化。生态位重叠的补偿规律在本项研究中并不明显。本项研究结果说明,蝗虫种资源利用的分化主要归因于蝗虫的适应性分化和蝗虫——植物协同进化的相互作用关系,而不是蝗虫种间竞争所造成的。     

Feeding patterns in grasshoppers (Orthoptera: Acrididae): Factors influencing diet specialization

Summary Diets of grasshopper species from two arid grassland communities in Trans-Pecos, Texas, were determined by gut analysis. Species-specific food plant choice and niche breadths are presented for each of these species. As a group, grasshoppers range from monophagous to polyphagous feeders although most species fall in the oligophagous to polyphagous group. Phylogenetic constraints are evident such that gomphocerinae are primarily grass feeders while melanoplinae feed predominantly on forbs; the oedipodinae show less clearcut tendencies.Feeding patterns are remarkably constant from site to site and overall, community niche breadth distributions between sites do not differ greatly. Individual species tend to eat the same plant species at various sites and maintain similar niche breadths. Species with relatively specialized diets tend to feed on predictable plant species such as grasses and long-lived perrenial forbs.Grasshopper feeding patterns present some problems to the current theory of herbivore diet specialization since forb feeding melanoplines tend to be polyphagous (contrary to predictions). Life history patterns unrelated to tracking host plants may explain some aspects of diet breadth since diet selectivities are presumably adjusted according to the probability of finding suitable food plants.     

Are howler monkey species ecologically equivalent? Trophic niche overlap in syntopic Alouatta guariba clamitans and Alouatta caraya

According to the principle of competitive exclusion, niche differentiation allows the stable coexistence of closely related species. We analyzed dietary profile and diversity, and dietary overlap between syntopic brown howlers (BR; Alouatta guariba clamitans) and black and gold howlers (BLG; A. caraya) in the Atlantic Forest of NE Argentina, with the objective of evaluating the degree of trophic niche overlap and potential interspecific competition for food. During 12 months, we collected data on feeding behavior of two groups of each howler species using the scan sampling method, together with data on food availability. Both at the group‐ and species‐level, we analyzed feeding behavior in terms of monthly percentages of time spent feeding on each food type and specific food item, dietary diversity (Shannon index H′), and we estimated dietary overlap using the percentage index and the Morisita–Horn index (C_H). Across months, both howlers showed species‐specific preferences for certain food items, and BLG had a more diverse diet (mean±SE, H′=2.77±0.08) than BR (H′=2.39±0.09). However, diets of both species overlapped extensively (percentage index=45.64±2.97%; C_H=0.6±0.05) and diets of conspecific groups did not overlap more than diets of groups of different species. Given their high degree of trophic overlap, syntopic BR and BLG meet one of the conditions necessary for interspecific food competition to occur. Although at present we lack direct evidence for interspecific competition in these howler species, we conclude that high levels of niche overlap may have an important role in maintaining the essentially parapatric distribution of howler species throughout the Neotropics. Am. J. Primatol. 72:173–186, 2010. © 2009 Wiley‐Liss, Inc.     

Comparisons of the food niches of three native and two introduced fish species in an Australian river

Synopsis The breadth, correspondence and overlap of the diets of the small and large size classes of the three native species (Galaxias occidentalis, Bostockia porosa and Edelia vittata) and two introduced species (Gambusia holbrooki and Perca fluviatilis) of fishes found in the shallows of the main channel and in the tributary creeks of a south-western Australian river have been compared in each season. Classification and ordination were used to examine the overall interrelationships of the diets across species, size groups, seasons and the location where the fish were caught (channel or creek). The smaller fish had a narrower dietary breadth than larger fish in the spring and summer, presumably reflecting the size limit imposed on prey size by their possession of a relatively small mouth in these seasons. Intraspecific dietary overlap between large and small size classes was usually high in G. occidentalis, but generally low in G. holbrooki and P. fluviatilis, and also in B. porosa and E. vittata when the difference between the lengths of the two size groups was greatest. Dietary overlap was least in autumn when the main prey taxa were most abundant. During winter, the diets of the three native species in the tributaries converged, probably reflecting a relatively low faunal diversity in these highly seasonal water bodies. The only relatively consistent interspecific overlap in diet was between B. porosa and E. vittata. Classification and ordination of the dietary samples separated G. occidentalis (which fed extensively on terrestrial organisms from the water surface) from the smaller P. fluviatilis (that concentrated on copepods in the plankton) and from B. porosa and E. vittata (which ingested primarily benthic organisms). Furthermore, B. porosa tended to ingest larger prey taxa than E. vittata. The diet of Gambusia holbrooki is sometimes dominated by terrestrial insects and at other times by benthic organisms, demonstrating that this species is an opportunistic carnivore. It is concluded that food partitioning by the three native and two introduced fish species in the Collie River is likely to be one of the principal factors facilitating the coexistence of substantial populations of these species in this system.     

荒漠草原蝗虫营养生态位及种间食物竞争模型的研究

以宁夏荒漠草原 1 2种蝗虫为对象 ,对荒漠草原蝗虫的营养生态位和种间食物竞争模型进行了研究 .采用嗉囊内含物分析技术分析了 1 2种蝗虫的取食特性和食物利用谱 ,并根据嗉囊内含物的分析结果 ,定量研究了蝗虫的营养生态位重叠和宽度 .依据生态位分化的特点 ,1 2种蝗虫可划分为 4个不同营养需求类群 :杂草取食者、杂草 禾草取食者、禾草 杂草取食者、禾草取食者 .通过蝗虫的取食频率、生物量以及种群密度 ,提出了蝗虫种间食物竞争力评估模型 ,对 1 2种蝗虫种间食物竞争的作用力进行了讨论 .     

Do selfing species have greater niche breadth? Support from ecological niche modeling

We explore the relationship between plant mating system (selfing or outcrossing) and niche breadth to gain new insights into processes that drive species distributions. Using a comparative approach with highly selfing versus highly outcrossing sister species, we test the extent to which: (1) species pairs have evolved significant niche divergence and less niche overlap, (2) selfers have wider niche breadths than outcrossers or vice versa, and (3) niches of selfers and outcrossers are defined by significant differences in environmental variables. We applied predictive ecological niche modeling approaches to estimate and contrast niche divergence, overlap and breadth, and to identify key environmental variables associated with each species’ niche for seven sister species with divergent mating systems. Data from 4862 geo-referenced herbarium occurrence records were compiled for 14 species in Collinsia and Tonella (Plantaginaceae) and 19 environmental variables associated with each record. We found sister species display significant niche divergence, though not as a function of divergence time, and overall, selfers have significantly wider niche breadths compared to their outcrossing sisters. Our results suggest that a selfing mating system likely contributes to the greater capacity to reach, reproduce, establish, and adapt to new habitats, which increases niche breadth of selfers.     

Dietary shifts in a stressed fish assemblage: Consequences of a bivalve invasion in the San Francisco Estuary

We compared dietary patterns within a temperate estuarine fish assemblage (Suisun Marsh, CA, U.S.A.) during a period of high mysid shrimp abundance and after a major decline in mysid abundance caused by the invasion of the overbite clam Potamocorbula amurensis. Prior to the invasion, high dietary overlap, high stomach fullness, and low niche breadth occurred among the fishes in spring when mysid populations were high. Dietary overlaps decreased and niche breadth increased for all species but the endemic splittail Pogonichthys macrolepidotus in fall when mysid populations were low. Eight native species exhibited lower overall collective overlaps and fuller stomachs than five alien species, suggesting more efficient resource partitioning. After mysid abundance declined, only alien striped bass Morone saxatilis preyed upon mysids in greater than trace amounts. An alien mysid became an important prey for small striped bass, but striped bass also switched to piscivory at a smaller size than when mysids were abundant. Eight of 13 species exhibited significant declines in abundance during the study period, which were concordant with the original importance of mysids in their diets. Our results suggest that altered lower food web dynamics in the San Francisco Estuary caused by the invasion of the overbite clam changed fish diets and have contributed to declines in fish abundance.     

The dietary basis for temporal partitioning: food habits of coexisting Acomys species

Two rodent species of the genus Acomys coexist on rocky terrain in the southern deserts of Israel. The common spiny mouse (A. cahirinus) is nocturnally active whereas the golden spiny mouse (A. russatus) is diurnally active. An early removal study suggested that competition accounts for this pattern of temporal partitioning: the golden spiny mouse is forced into diurnal activity by its congener. Theoretically, temporal segregation should facilitate coexistence if the shared limiting resources differ at different times (primarily among predators whose prey populations have activity rhythms), or if they are renewed within the period of the temporal segregation. We studied food preferences of the two Acomys species in a controlled cafeteria experiment in order to assess resource overlap and the potential for competition for food between the two species. We found no significant difference in food preferences between species. The dietary items preferred by both were arthropods. We also carried out a seasonal study of the percentage and identity of arthropods taken in the field by individuals of the two species. Individuals of both species took on annual average a high percentage of arthropods in their diets. Seasonal diet shifts reflect seasonal abundance of arthropods at Ein Gedi during day and night. Diurnal activity may also reduce interspecific interference competition between A. russatus and A. cahirinus. However, the strong interspecific dietary overlap in food preference, the heavy reliance on arthropods in spiny mouse diets, and the seasonal and circadian differences in arthropod consumption suggest that prey partitioning may be a viable mechanism of coexistence in this system. Received: 6 July 1998 / Accepted: 10 May 1999     

Niche compression: Two tests of an hypothesis using narrowly sympatric predator species

The compression hypothesis predicts that when two species occur together in narrow sympatry, individuals in the overlap zone will use a smaller range of habitats and a larger or unchanged range of prey than individuals in allopatry. This report attempts to validate the assumptions underlying this hypothesis, and describes two tests of the predicted resource shifts using narrowly sympatric species of predatory marsupials (Antechinus spp.). In the first test, using A. stuartii and A. flavipes, there was little correspondence between observed and predicted changes in diet and habitat use (as measured by indices of niche breadth) for populations of either species. One index of niche breadth (Levins' B) revealed no trends in resource use, but a proportional similarity index relating resource use to resource abundance consistently indicated that the niche breadths of each species were greater in allopatry than in narrow sympatry. In the second test, using A. stuartii where it occurred alone and in narrow sympatry with A. swainsonii, there was again little correspondence between observed and predicted changes in resource use for seasonal or overall data. Differences in magnitudes of niche breadths between allopatric and narrowly sympatric A. stuartii were smaller in this test than in the first. While these findings provided no support for the compression hypothesis, they suggested three situations in which the predictions of the hypothesis may generally not apply. These are:

• (i) when the predators are active, dietary generalists (diet cannot expand in sympatry);
• (ii) when one species is a markedly superior competitor to the other (the dominant species suffers little or no niche compression in sympatry); and
• (iii) when the species compete by interference rather than exploitation (one species is evicted from sympatry or both show compression in habitat use and diet).

     

Trophic interactions between brown and south polar skuas at Deception Island,Antarctica

It is broadly accepted that the brown skua (Stercorarius antarcticus lonnbergi) competitively excludes the south polar skua (S. maccormicki) from penguin colonies when breeding sympatrically, forcing the latter to feed on marine resources. The purpose of this work was to examine the diets and trophic niche breadths of each species where they co-occur and to determine the degree of overlap. To this end, we analyzed 169 pellets of brown skuas, collected in two different areas (20 individuals), and 152 of south polar skuas, collected in three different areas (18 individuals), on Deception Island, South Shetland Islands, Antarctica, during the austral summer 2000. Pellet analysis often underestimates the amount of easily digestible prey, but allows for comparisons of the relative contributions of different items in the diet. South polar skuas at our study locations consumed seven different food items and had a trophic niche breadth of 0.133 compared to brown skuas that fed on 10 different items and had a trophic niche breadth of 0.078. The niche overlap between the species was 82.1%. Penguins were the principal food source of both species, however, brown skuas fed mostly on chicks, while south polar skuas fed on adults (carcasses). The use of different age classes of penguins as a food source offers an alternative to competitive exclusion, allowing the coexistence of these species on Deception Island.     

NESTLING DIETS OF PRAIRIE PASSERINE BIRDS AT MATADOR, SASKATCHEWAN, CANADA

The nestling diets of seven species of grassland passerines were studied from gullet samples collected in 1969–1971 at Matador, Saskatchewan, Canada. Relative population densities on census plots on grazed and ungrazed prairie showed that Horned Lark Eremophila alpestris, McCown's Longspur Calcarius mccownii and Chestnut-collared Longspur C. ornatus preferred grazed areas and Sprague's Pipit Anthus spragueii, Western Meadowlark, Sturnella neglecta, Savannah Sparrow Passerculus sandwichensis and Baird's Sparrow Ammodramus bairdii preferred ungrazed prairie. Fifteen invertebrate ordinal taxa, and seeds were represented to an important extent in combined gullet contents; but two taxa, Lepidoptera (77% larvae) and grasshoppers (all Acrididae), comprised the bulk of nestling diets. Four grasshopper species contributed 70–100% of grasshoppers eaten in June-August. Overlap at the family level was also high in several other important prey. Comparison with invertebrate populations of ungrazed prairie showed that the birds ignored some abundant taxa of very small invertebrates, and apparently preferred the two least abundant groups which offered large individual prey items. Average nestling food overlap indices for the season among all species except Savannah Sparrow and Baird's Sparrow, based on taxonomic composition, was 0.85. Overlap was moderate in May and June and became very high in July and August. The number of nestlings reached a peak in June and early July when nestling food overlap was much lower than later in the season. Horned Larks avoid competition by nesting earlier than do the other species, while McCown's Longspur, which depends on grasshoppers for nestling food more than do the other species, tends to breed later in the season than the other species. Finally, data suggest that nestling food may be superabundant.     

The food niches of the invasive Dugesia tigrina (Girard) and indigenous Polycelis tennis Ijima and P. nigra (Müller) (Turbellaria; Tricladida) in a Welsh lake

The invasion of Llyn Coron in North Wales by the American immigrant Dugesia tigrina resulted in the almost entire displacement of the native Polycelis tenuis and P. nigra populations. Because competition for food is the most important factor controlling and regulating populations of British lake-dwelling triclads, the diets of the invasive and native triclads in the lake were examined in an attempt to explain the successful invasion.A serological technique, the precipitin test, identified the gut contents of field-collected triclads. Niche breadth, electivity and niche overlap indices were used in analysis of the data. A broad food niche was recorded for all the triclad species. Oligochaetes predominated in the diet of D. tigrina followed by Asellus and chironomids, in almost equal proportions, snails and caddisflies, with mayflies scarcely eaten. Both Polycelis species fed heavily on oligochaetes followed by Asellus. P. tenuis ate slightly higher proportions of chironomids and caddisflies than snails and mayflies, whilst P. nigra consumed similar proportions of these four prey taxa. Gammarus, scarce in Llyn Coron, and cladocerans were not eaten by the Polycelis species and by only a few D. tigrina.To-date there has been no apparent shift in the diet of the Polycelis species as a consequence of the invasion by D. tigrina. In the absence of any evidence for the partitioning of food on the basis of prey size or condition, the considerable overlap in the diets of D. tigrina and the Polycelis species suggests the potential for severe inter-specific competition for food. The superior exploitation by D. tigrina of the available food resource requires explanation.     

Bathymetric distribution and feeding habits of two sympatric cheilodactylid fishes at Miyake-jima,Japan

Habitats including depth, diurnal activity patterns, and diets of the two cheilodactylid fishesCheilodactylus zonatus andC. zebra were studied at Igaya Bay, Miyake-jima, Japan. Both species occurred at nearly equal densities in identical habitats and depths. They preyed on benthonic organisms from early morning to shortly before sunset, when feeding activities decreased remarkably and intraspecific social behavior greatly increased. Gut analyses showed a high degree of dietary overlap, but proportions of food items in their diets differed slightly.C. zonatus was more of a food generalist thanC. zebra, showing a higher niche breadth value.C. zebra tends to feed on epifauna, especially gammaridean amphipods and decapods, whileC. zonatus takes both epifauna and infauna including polychaetes.     

The decline of the Turtle Dove: Dietary associations with body condition and competition with other columbids analysed using high‐throughput sequencing

Dietary changes linked to the availability of anthropogenic food resources can have complex implications for species and ecosystems, especially when species are in decline. Here, we use recently developed primers targeting the ITS2 region of plants to characterize diet from faecal samples of four UK columbids, with particular focus on the European turtle dove (Streptopelia turtur), a rapidly declining obligate granivore. We examine dietary overlap between species (potential competition), associations with body condition in turtle doves and spatiotemporal variation in diet. We identified 143 taxonomic units, of which we classified 55% to species, another 34% to genus and the remaining 11% to family. We found significant dietary overlap between all columbid species, with the highest between turtle doves and stock doves (Columba oenas), then between turtle doves and woodpigeons (Columba palumbus). The lowest overlap was between woodpigeons and collared doves (Streptopelia decaocto). We show considerable change in columbid diets compared to previous studies, probably reflecting opportunistic foraging behaviour by columbids within a highly anthropogenically modified landscape, although our data for nonturtle doves should be considered preliminary. Nestling turtle doves in better condition had a higher dietary proportion of taxonomic units from natural arable plant species and a lower proportion of taxonomic units from anthropogenic food resources such as garden bird seed mixes and brassicas. This suggests that breeding ground conservation strategies for turtle doves should include provision of anthropogenic seeds for adults early in the breeding season, coupled with habitat rich in accessible seeds from arable plants once chicks have hatched.     

Seasonal Variation in Polyspecific Associations Among Callimico goeldii, Saguinus labiatus, and S. fuscicollis in Acre, Brazil

Polyspecific associations (PSA) occur when 2 or more species maintain proximity or coordinate activities. PSA may provide ecological benefits similar to those of monospecific groups, i.e., protection against predation and improved foraging efficiency, but may also impart costs, such as feeding competition. I studied 3 New World Callitrichidae—Callimico goeldii, Saguinus fuscicollis, and S. labiatus—in northwestern Brazil over 18 mo between April 1999 and August 2003, during which single primary study groups of C. goeldii, S. labiatus, and S. fuscicollis consistently associated with one another. I compared patterns of PSA participation to variation in plant diets during wet and dry seasons. All 3 species associated an average 61% of observation time, but with significant seasonal variation in PSA. During the dry season, April–September, PSA occurred significantly less frequently than during the wet season, October–March (37% vs. 88%). The variation in PSA corresponded with seasonal shifts in plant food diets, resulting in less dietary overlap among all 3 species during the dry season, particularly between Callimico goeldii and Saguinus labiatus. Dietary richness, diversity, and evenness were also lower in the dry compared to the wet season for each species. The results suggest a link between PSA participation and diet among the taxa; foraging-related costs or feeding competition may constrain PSA during the dry season.     

Food resource utilization partitioning of fifteen fish species at Bukit Merah Reservoir,Malaysia

Statistical and mathematical models have been used to measure the subtle differences in food resources utilisation of fifteen (15) fish species at Bukit Merah Reservoir, Malaysia. The models employed are niche breadth, dietary overlap indices and discriminant analysis. A diet measure based on the relative importance index of food items was used for the analysis, to correct for biases of the single indices consisting of the volumetric, numerical and occurrence frequency. Niche breadth (B_i) indicating the diversity or breadth of the food resource gradient utilized by a fish classifies species as generalized feeders (B_i > 4.5), intermediate and specialized feeders (B_i < 2). Niche overlap (O_ij) quantifying the sharing of food resource between two species varies from 0.07 to 0.81 and describes high dietary overlap (O_ij > 0.60) for most fish at the reservoir; but Trichogaster pectoralis (Anabantidae) feeding on the plankton shows relatively low dietary overlap. A scatter plot and a territorial map of the discriminatory analysis on the dietary composition result in combination an objective basis for trophic classification of the fish community, and describe (1) Osteochilus hasselti and Puntius gonionotus as herbivores, (2) Oxyeleotris marmorata, Clarias batrachus, Ophicephalus striatus, Mystus planicep, and presumably Wallago leerii and Hampala macrolepidota as carnivores, (3) Puntius schwanenfeldii, Cyclocheilichthys apogon, and presumably Labiobarbus festiva as detritivores, (4) Notopterus notopterus as a generalist, and (5) Trichogaster pectoralis as a planktivore. This multivariate analysis is relatively superior to the traditional subjective method for trophic classification and discerning subtle differences objectively, though intermingling occur.     

Dietary composition of wildebeest (Connochaetes taurinus) kongoni (Alcephalus buselaphus) and cattle (Bos indicus), grazing on a common ranch in south-central Kenya

This paper gives the results of a study conducted at Game Ranching Ltd, situated at the Athi Kapiti Plains, Kenya, to determine the dietary composition of cattle (Bos indicus L), kongoni (Alcephalus buselaphus Pallas) and wildebeest (Connochaetes taurinus Burchell), through two forage growing seasons (wet and dry). The dietary preferences and overlaps between the species were also determined. The diet preference of the three herbivores was determined using a microhistological analysis technique. The three dominant grasses in the ranch: Themeda triandra Fork, Digitaria macroblephara (Hack.) Stapf and Penisetum mezianum Leeke, formed the major diets of the animals. The browse component of the diets increased during the dry season by about 100% for all the animal species, with cattle always having twice as much browse as the wild herbivores. However, the animals selected similar diets in terms of plant species during both seasons but were more selective during the wet season. Dietary overlaps were always above 75%, but more than this during the dry season. The dietary overlaps were lower between cattle and wild herbivores than between the wild herbivores. The diet preference index for the animals differed from season to season, and from plant to plant.     

草原蝗虫营养生态位的研究*

本文采用嗉囊内含物显微分析技术系统地研究了内蒙古典型草原蝗虫的选食特性和食物利用诺。根据11种蝗虫嗉囊内含物分析的结果,定量地研究了蝗虫的营养生态位以及生态位的重叠和宽度。11-种蝗虫依据生态位分化的特点,被划分为5个不同的营养需求类群：禾草取食者、禾草-杂草取食者、杂草-禾草取食者、杂草取食者和杂食者。作者通过对蝗虫食性及生物量的研究,提出了蝗虫潜在严重值和实际严重值的概念和计算方法,也就蝗虫在草原生态系统中的相互作用关系及共存关系进行了讨论。