人工柠条-荒漠草地交错带拟步甲昆虫群落多样性

选取宁夏东部盐池县人工柠条灌丛-荒漠草地交错带为研究样地,以距离梯度形式,利用巴氏诱罐法对拟步甲科昆虫群落多样性进行了调查,研究了边缘效应对拟步甲昆虫群落多样性的影响。共采集拟步甲昆虫1405只,分属8属13种。结果表明,克小鳖甲和弯齿琵甲个体数量分别占总个体数的32.74%和43.27%,为该地区的优势种类。拟步甲昆虫在人工柠条灌丛-荒漠草地交错带的分布可分为3种类型,优势种克小鳖甲和弯齿琵甲属于栖息地广布型,但二者并没有表现出十分均匀的适应性,而且他们在各样带的分布呈显著负相关,克小鳖甲的分布趋向于沙生荒漠环境,弯齿琵甲的分布趋向于柠条灌丛;常见种蒙古漠王、小皮鳖甲的分布偏向于喜好荒漠草地;异距琵甲、奥氏真土甲、网目土甲和淡红毛隐甲的分布则偏向于喜好柠条灌丛。拟步甲昆虫丰富度与Shannon-Wiener多样性沿边缘分别向柠条灌丛和荒漠草地内部降低,个体数量总体上沿柠条灌丛、交错带向荒漠草地内部降低,但各样带差异不显著。从季节动态看,荒漠草地和柠条灌丛物种多样性季节变化相似,3种生境拟步甲活动密度季节变化相似。边缘效应强度分析呈现边缘正效应。CCA排序图显示分类地位相近的物种在生态适应上具有趋同性。多元回归分析表明,植被密度影响拟步甲昆虫群落的优势种和个体数量,植被盖度和高度分别影响拟步甲群落的均匀度和丰富度。主坐标分析(PCo A)排序表明人工柠条灌丛-荒漠草地交错带的拟步甲昆虫群落组成与柠条灌丛内部没有明显分化,但趋于向柠条灌丛生境演替。     

The Balkan wet grassland vegetation: a prerequisite to better understanding of European habitat diversity

The knowledge of broad-scale floristic variation in wet grasslands, which are endangered throughout Europe, is still limited and some regions have remained unexplored so far. In addition, hitherto published phytosociological studies were concentrated at the national level and therefore national vegetation classifications are not consistent with each other. In order to overcome these shortcomings of traditional phytosociology, we gathered original data from Bulgaria and analysed them together with the data from Central Europe. We further analysed major compositional gradients within Bulgarian wet grasslands and changes in species richness along them. We sampled 164 wet grassland vegetation plots throughout Bulgaria. We further prepared a restricted data set of wet grasslands from Central-European phytosociological databases. Both data sets were merged and classified by modified TWINSPAN. Four distinct vegetation types were differentiated. Even if they correspond with traditional alliances, which are primarily drawn as geographically defined units in Western and Central Europe (sub-Mediterranean Trifolion resupinati, sub-continental Deschampsion cespitosae and Molinion caeruleae and sub-oceanic Calthion palustris), they all occur in Bulgaria. When more precise classification was applied, two types of sub-Mediterranean wet grasslands and one high-altitude type of Calthion grasslands were detected solely in Bulgaria. DCA analysis showed that altitude is a dominant gradient controlling variation in Balkan wet grasslands. The second DCA axis was interpreted as the gradient of nutrient availability. Species richness shows skewed-unimodal trends along both major gradients, with the highest species richness in intermittently wet nutrient-limited grasslands. Tukey post-hoc test of altitudinal differences amongst vegetation types is significant for all pairs of clusters, suggesting that altitudinal differentiation is responsible for co-occurrence of nearly all European types of wet grasslands in Bulgaria. Our results suggest that (1) climate is an important factor for the diversity of wet grasslands; (2) Balkan vegetation of middle altitudes matches with that of Central Europe, whereas that of the lowest altitudes corresponds rather to the sub-Mediterranean region and high mountains are specific; (3) upward shift of Central-European vegetation types in southern Europe, so often described in forest vegetation is also evident for grassland vegetation and (4) the high diversity of Balkan vegetation is determined by a diverse relief enabling confluence of habitats possessing different climatic conditions.     

A mowing experiment to evaluate the influence of management on the activity of host ants of <Emphasis Type="Italic">Maculinea</Emphasis> butterflies

Maculinea butterflies obligatory parasitize certain species of Myrmica ants. Thus, the presence of the host ant species is a limiting factor for the survival of a Maculinea population. Here, we analyse the influence of vegetation structure and ground temperature on ant diversity and abundance on Maculinea habitats, with the final aim of identifying the environmental variables determining patterns of variation in species composition in order to recommend a mowing regime that will promote our three target species: Maculinea teleius, M. nausithous and M. alcon. Experimental plots with different mowing regimes were established at eight sites in South-Eastern Germany, a region which still contains a number of relatively large, stable populations of these threatened butterfly species. Among the seven different ant species recorded, four belong to the genus Myrmica (M. scabrinodis, M. rubra, M. ruginodis and M. vandeli). Among these, M. scabrinodis results most abundant at all sites. In a CCA analysis of environmental variables recorded at the studied plots, ant species diversity appears largely determined by litter cover, mean temperature, and mean grass cover. Mowing once a year, in the second half of September, after the larvae have left their host plants, enhances the abundance of Myrmica ants in the meadows, and would be the best management compromise for all three species.     

Comparison of soil seed banks of habitats distributed along an altitudinal gradient in northern Iran

In this study we investigated the variations in soil seed banks along an altitudinal gradient in the Alborz mountains, Iran, covering three habitats from lower to upper altitudes: forest, forest-subalpine grassland ecotone and subalpine meadow. In each habitat from 1850 to 2400 m, 20 quadrats were established along four transects, and the above-ground vegetation and the germinable seed banks were determined. Results show that the similarity between seed bank and vegetation was lowest in the ecotone located at intermediate altitudes. Together with the contrasting highest density and species diversity of seeds at these altitudes, the ecotonal role of this habitat was confirmed.We found evidence that lower altitudes could act as storage for seeds of some species growing at higher altitudes; the role of the ecotone was more prominent as a reserve for the meadow plant seeds than the role of the forest as a reserve for seeds of the meadow and ecotone habitats. Soil seed banks, particularly from the ecotone, can be used for restoring vegetation in some degraded sites.     

Macroinvertebrate communities in Phragmites australis (Cav.) Trin. ex Steud. reed beds and open bank habitats in central victorian streams in Australia

Reed invasion is a common phenomenon of open streams with disturbed riparian vegetation in river catchments. Knowledge of the effects of such vegetation change on aquatic communities is fundamental to river management. Macroinvertebrate fauna in Phragmites australis (Cav.) Trin. ex Steud. and open bank habitats were examined in three rivers in central Victoria in order to understand the effect of such littoral habitat on macroinvertebrates. Data were analysed using Partially Nested Factorial ANOVA with season, river and habitats as main effects. Habitat structure had a significant effect (p<0.05) on macroinvertebrate species richness, however this was not seasonally consistent across the three rivers. There was a significant increase (p<0.05) in macroinvertebrate taxa richness in Phragmites habitats during winter and spring seasons. Total abundance of taxa showed no consistent significant differences in the two habitats. Results of Canonical Analysis of Principle Coordinates indicated significant differences (p<0.05) in macroinvertebrate assemblages between Phragmites and bare bank habitats in all seasons. Habitat selection by taxa could be related to the microphysical environment of the habitats. This study suggests that reed beds create important littoral habitat structures which support diverse macroinvertebrate assemblages.     

The effects on terrestrial arthropod communities of invasion of a coastal heath ecosystem by the exotic weed bitou bush (<Emphasis Type="Italic">Chrysanthemoides monilifera</Emphasis> ssp. <Emphasis Type="Italic">rotundata</Emphasis> L.)

Bitou bush (Chrysanthemoides monilifera ssp. rotundata) is a major environmental weed of littoral habitats on the southeastern coast of Australia. This study investigates the impacts upon selected arthropod assemblages of habitat invasion by this weed. Sixteen sites were placed at four geographic localities within nature reserves between Forster and Budgewoi on the coast of New South Wales. The sampling design included two spatial scales (between and within localities) and eight repeat samples (taken at two scales of temporal separation). Arthropods were collected from both arboreal and epigaeic micro-habitats. Specimens of ants (Hymenoptera: Formicidae), beetles (Coleoptera), true bugs (Heteroptera) and spiders (Araneae) were identified to species level. Differences in α diversity and species abundance distributions between the taxonomic assemblages are described, along with comparisons of data contrasts between bitou bush-free (“control”) and bitou bush-invaded (“impact”) habitats and between geographic localities. A subsidiary impact associated with herbicide application for control of the weed is also examined. Analysis of environmental differences indicates that bitou bush acts as a dampening agent, reducing the degree of seasonal fluctuation in factors such as leaf litter cover. Arboreal Heteroptera were the only group to show consistent evidence of significant differences in taxon richness or abundance between control and impact treatments within a locality, seen as a disruption of normal seasonal variation in diversity in bitou bush-impacted sites. Significant differences between geographic localities were more common, suggesting an effect at broader spatial scales. Evidence for arthropod assemblages characteristic of specific vegetation types was detected for several groups, as were changes in arthropod assemblage composition following application of herbicide for bitou bush control.     

Invasion of alien macroalgae in different Mediterranean habitats

The study evaluated different macroalgal invasions in the main Mediterranean coastal habitats on hard bottom. Biodiversity, species composition and structure of macroalgal assemblages were compared among non-invaded areas and areas invaded by the Chlorophyta Caulerpa racemosa var. cylindracea and by the turf-forming Rhodophyta Womersleyella setacea in three different habitats: shallow rocky bottom, deep rocky bottom and dead matte of the seagrass Posidonia oceanica. Results showed that alien macroalgae constituted a relevant component of benthic assemblages in invaded areas of the Mediterranean Sea. Assemblages invaded by Womersleyella setacea and Caulerpa racemosa showed lower values of diversity and large differences in the structure and species composition related to non-nvaded assemblages. The species that mostly suffered from invasion were erect species reproducing sexually; moreover, the dominance of W. setacea led to low abundance of native filamentous algae, while C. racemosa colonization seemed particularly threatening for encrusting algae. All the studied habitats appeared highly invasible by alien macroalgae, even if W. setacea appeared more invasive in deeper habitats, while colonization of C. racemosa seemed more serious in shallower habitats; the dead matte of P. oceanica represented a suitable substrate for the spread of both species. Differences among assemblages in different habitats were reduced in invaded areas.     

Elephant dung decomposition and coprophilous fungi in two habitats of semi-arid Botswana

In order to understand the impact of habitat changes on ecosystem processes caused by increased populations of elephants, elephant dung decomposition was studied in semi-arid Botswana. Dung decomposition rates were studied with and without the presence of arthropods, using pairs of exposed dung and dung enclosed in nylon-mesh bags, respectively. Dung decomposition rates were lower in the absence of arthropods. The rates in the late wet season were higher in the scrubland than in the woodland. In the early dry season, immediately after the wet season, the rates were higher in the woodland than in the scrubland. The difference in decomposition rates between habitats was attributed to microclimatic conditions created by vegetation cover. With regard to fungal succession, Cladosporium cladosporioides and Eurotium brefeldianum occurred only in the late stages of dung decomposition whereas Talaromyces helicus, Cercophora coprophila and Sporormiella minima occurred in all the stages. Although there was no significant difference in Shannon–Weiner fungal species diversity index between habitats, seasons, dung ages and laboratory incubation periods, there were significant differences in fungal community composition between these parameters. Species richness was higher in the late wet season than in the early dry season, indicating the importance of moist conditions for a large diversity of fungal species.     

Diversity, host, and habitat specificity of oomycete communities in declining reed stands (Phragmites australis) of a large freshwater lake

We studied the diversity of oomycetes in a declining reed belt (Phragmites australis) of Lake Constance, Germany, using conventional baiting with specific reed and standard oak baits, accompanied by molecular techniques. Apart from an Aphanomyces sp. and a Phytophthora sp., baiting from reed rhizosphere samples from flooded, as well as drier, littoral sites revealed only Pythium spp. A total of 67 oomycete isolates was classified according to PCR-RFLP banding patterns and ITS sequencing, and 18 different sequence types could be separated. The majority of these seemed previously unknown species, as indicated by the degree of similarity to those deposited in nucleotide databases. Species communities in both flooded and drier habitats or both reed and oak baits clearly differed from one another, and only few species occurred in both dry and flooded sites, or in both oak and reed baits. A frequently occurring group of related Pythium species appeared to be specifically associated with reed, and these were the only species that proved pathogenic towards this host in vitro. Our study proved that unexplored natural ecosystems harbour diverse communities of oomycete species with specific habitat and host preferences within close-by, but ecologically contrasting, sites. Among the species isolated, those associated with the predominating plant might accumulate and thus may be reed pathogens of considerable importance.     

Designing Wetlands for Amphibians: The Importance of Predatory Fish and Shallow Littoral Zones in Structuring of Amphibian Communities

Under section 401 and section 404 of the Clean Water Act, permission to degrade existing natural wetlands in the USA may be conditional on restoring or creating ‘replacement’ wetlands. Success of wetland mitigation efforts in adequately replacing lost wildlife habitats depends on our good understanding of key ecological attributes that affect the structure of wetland faunal communities. We examined the effects of the presence of predatory fish, shallow vegetated littoral zone, emergent vegetation cover, wetland age and size on amphibian diversity in 42 replacement wetlands located in the Ohio’s North Central Tillplain ecoregion. We recorded 13 species of pond-breeding amphibians, and the average local species richness (α-richness) was 4.2 ± 1.7 species per site (range 1–7). There is strong evidence for the positive association between amphibian species richness and presence of a shallow littoral zone, and the negative association with presence of predatory fish. There was no evidence for the association between species richness and age, size, amount of forest cover within 200 m, nor the amount of emergent vegetation cover at the study sites. It is estimated that local species richness in wetlands with shallows was 1.76 species higher on average than in wetlands without shallows (95% CI from 0.75 to 2.76). The presence of predatory fish was associated with an average reduction in species richness by an estimated 1.21 species (95% CI from 0.29 to 2.11). Replacement wetlands were placed in areas with little or no existing forest cover, and amphibian species associated with forested wetlands were either rare (eastern newt, spotted salamander) or not present at all (marbled salamander, wood frog). In addition, we surveyed all replacement wetlands constructed under section 401 in Ohio since 1990, and found that predatory fish were present in 52.4% of the sites and that shallows were absent from 42.7% of the sites. Our results indicate that current wetland replacement practices could have a negative effect on the amphibian diversity within our region.     

山西省辛安泉泉域大型藻类的研究

1995~2003年间,对山西省辛安泉域的藻类植物进行了4次采集,共采得藻类植物标本71号,已鉴定出的大型藻类植物36种,隶属6门, 11科, 18属。其中,以绿藻门的种类最多,有4科8属19种;其次是蓝藻门,有2科5属11种;再次为黄藻门,有2科2属3种;排在最后的是红藻门,硅藻门和轮藻门,分别仅有1科1属1种。群落主要包括4类,即刚毛藻群落(Cladophora community),无隔藻群落(Vaucheria community),水绵-双星藻群落(Spirogyra-Zygnema community)和轮藻群落(Chara community)。     

Multi-scale habitat selection and foraging ecology of the eurasian hoopoe (<Emphasis Type="Italic">Upupa epops</Emphasis>) in pine plantations

Bird conservation can be challenging in landscapes with high habitat turnover such as planted forests, especially for species that require large home ranges and juxtaposition of different habitats to complete their life cycle. The eurasian hoopoe (Upupa epops) has declined severely in western Europe but is still abundant in south-western France. We studied habitat selection of hoopoes in pine plantation forests using a multi-scale survey, including point-counts at the landscape level and radio-tracking at the home-range scale. We quantified habitat use by systematically observing bird behaviour and characterized foraging sites according to micro-habitat variables and abundance of the main prey in the study area, the pine processionary moth (Thaumetopoea pityocampa). At the landscape scale, hoopoes selected habitat mosaics of high diversity, including deciduous woods and hedgerows as main nesting sites. At the home-range scale, hoopoes showed strong selection for short grassland vegetation along sand tracks as main foraging habitats. Vegetation was significantly shorter and sparser at foraging sites than random, and foraging intensity appeared to be significantly correlated with moth winter nest abundance. Hoopoe nesting success decreased during the three study years in line with processionary moth abundance. Thus, we suggest that hoopoes need complementation between foraging and breeding habitats to establish successfully in pine plantations. Hoopoe conservation requires the maintenance of adjacent breeding (deciduous woods) and foraging habitats (short swards adjacent to plantation edges), and consequently depends on the maintenance of habitat diversity at the landscape scale.     

Habitat preferences of tree pipit ( Anthus trivialis) and meadow pipit ( A. pratensis) at sympatric and allopatric localities

Habitat preferences of the tree pipit (Anthus trivialis) and the meadow pipit (A. pratensis; Passeriformes: Motacillidae) were observed during the years 1998–1999 at three localities in the Czech Republic; two with one pipit species only, and a third with both species present. We investigated one of the possible mechanisms allowing syntopic coexistence—different habitat selection. We characterised territories of each pipit pair by the habitats present in the territory (defined by dominant plant composition) and by quantitative parameters (territory size, height and density of the vegetation, number of look-outs of different height categories, and proportion of wet ground). Tree pipits preferred significantly higher vegetation of lower density than meadow pipits, and there was generally a higher number of high look-outs in their territories. However, in some of the preferred territories at the allopatric locality of the tree pipit, steep hill slopes could well substitute for higher look-outs, which were almost absent. The two pipit species at the sympatric locality occupied very different habitats, which was also reflected in quantitative parameters of their territories. The available data of pipit habitat at different European localities show that the two species can occupy a much wider range of habitats. The habitat separation in sympatry might therefore be one of the mechanisms allowing syntopic coexistence of both species.Communicated by F. Bairlein     

Biogeography and ecology of Anostraca (Crustacea) in middle Paroo catchment of the Australian arid-zone

Fourteen species of Branchinella and one each of Parartemia, Streptocephalus (Parastreptocephalus) and an undescribed branchipodid genus occur in a limited area (2000 km²) of the Paroo in northwestern New South Wales and southwestern Queensland. Syntopic coexistence was common (55% of collections) but to a large degree species interactions are minimized by habitat factors of turbidity, salinity and length of the wet phase in decreasing order of importance, and by a species factor of relative size. Discrete habitats such as claypans had a similar species composition each time they filled, but creek pools and other connected sites had variable species composition over time. The high biodiversity is explained by the presence of many distinct types of wetlands, each with their own characteristic anostracans.     

Bird community variation across <Emphasis Type="Italic">Polylepis</Emphasis> woodland fragments and matrix habitats: implications for biodiversity conservation within a high Andean landscape

The scattered and dwindling Polylepis woodlands of the high Andean global hotspot have been identified as being of particular importance to biodiversity conservation, and yet little is known of the make-up of their faunal communities, how these vary across landscapes, and how well species might tolerate matrix/edge habitats. We examined the bird communities and vegetation characteristics of Polylepis woodlands and the surrounding matrix habitats at three sites in the Cordillera Vilcanota, southern Perú (3,400–4,500 m). The vegetation structure of woodlands varied significantly across the three sites but all were dominated by two Polylepis tree species, with mossy ground cover. Matrix habitats were treeless and dominated by ground-level puna grass-steppe or boulder scree vegetation. Bird species richness and diversity, encounter rates and the number of globally-threatened and restricted-range bird species were consistently higher in the Polylepis forests, than in matrix habitat. We used canonical correspondence analysis (CCA) to identify habitat gradients across the landscape, and to classify bird species according to their association with Polylepis, the matrix or Polylepis-matrix interface. There were few matrix-restricted bird species, but around half the bird community, including fourteen threatened or restricted-range species, were Polylepis-dependant. Many of these species had very narrow niches. The Polylepis-matrix interface was dominated by species traditionally considered invasive ecological generalists. Our study illustrates the overriding importance of Polylepis interior habitats, indicating that conservation strategies for high Andean birds must focus on patch size maintenance/enlargement, enhancement of within-patch habitat quality, and efforts to safeguard connectivity of suitable habitat across what is essentially an inhospitable puna/scree matrix.     

垫状植物囊种草对群落物种多样性的影响

在甘肃盐池湾国家级自然保护区内海拔4137 m处,选择典型的囊种草垫状植被设置研究样地,研究了垫状植物囊种草对群落物种组成和群落物种多样性的影响,并且定量的研究了囊种草对群落物种丰富度的影响能力和维持潜力。研究结果表明:囊种草为群落中增加了新的植物种类,并且提高了部分生境一般种的多度;囊种草的出现提高了群落物种密度和物种丰富度,进而提高了群落物种多样性;囊种草斑块的增加将会引起景观水平物种丰富度的增加,表明囊种草具有为群落中引入新的植物种类进而提高群落物种丰富度的能力;在景观水平,囊种草所创造的生境多样性则成为一种保障,可以维持景观中物种丰富度从而降低物种损失的风险,表明囊种草具有较高的群落物种丰富度维持潜力。     

Community homogenization and the invasiveness of commensal species in Mediterranean afforested landscapes

The ecological consequences of homogenization remain relatively unexplored. One example of landscape-homogenizing is the establishment of plantations. We studied the effect of human-made forests by contrasting plant and small-mammal community composition between planted tree stands and adjacent natural habitat in two different Mediterranean habitats in Israel: (1) inland habitat where we focused on pine (Pinus halepensis) and carob (Ceratonia siliqua) stands, and (2) coastal sand dune habitat where we focused on planted acacia (Acacia saligna) stands. We first wanted to verify whether planted trees modify plant species composition, and second, if and how the small-mammal community is affected by the different habitat conditions created in plantations with different canopy cover. We were especially interested in the abundance of the commensal house mouse (Mus musculus). All tree stands underwent biotic homogenization indicated by abundance of house mice coupled with lower diversity of indigenous vegetation and small-mammal abundances and diversities. Habitat structural diversity was positively related with small-mammals diversity and was lower in artificial tree stands in both habitats. Our results suggest that using the abundance of commensal generalist species such as the house mouse relative to other more specialist small-mammals is a good approach to determine ecosystem integrity. Pre-commercial thinning treatment is a potential management tool to maintain a proportion of native tree species within the canopy of planted tree stands. However, until sufficient data is available for making generalizations, the exact level of thinning necessary to reverse the homogenization processes in man-made plantations and keeping indigenous small-mammal communities diverse and less prone to invasion must be determined empirically.     

The role of the hemiparasitic annual Rhinanthus minor in determining grassland community structure

Summary Rhinanthus minor (yellow-rattle) is a widespread hemiparasitic plant of grassland habitats throughout Great Britain. It is usually considered to be indicative of species-rich grassland, but in a survey of 14 habitats throughout Britain it was found that R. minor at the time of flowering normally occupied relatively low-diversity patches within areas of high diversity as determined by the number of species, Simpson's Index and the Shannon-Wiener Index. Following the death of adult plants of R. minor in the summer it was shown that the pattern of species diversity changed such that by the time R. minor germinated in the following spring the differences between the areas containing and not containing R. minor were much less distinct. A perturbation experiment in which R. minor was removed from four sites indicated that the effect of the removal of R. minor on the development of community structure over the next year was to increase species diversity on three of the sites and decrease it on the fourth. Those species which responded to the removal of R. minor by an increase in abundance were shown to be preferred hosts. All three lines of evidence point to the fact R. minor has a significant effect on the species diversity of the communities in which it grows by selectively parasitizing components of the flora and modifying the competitive relationships between plants. However, as the communities generally responded to the removal of R. minor by an increase in diversity and as the general survey indicated that R. minor is generally associated with areas of low diversity it would appear that the plants which are selectively parasitized are generally not the competitive dominants in the community.     

Ecological significance of light controlled seed germination in two contrasting tropical habitats

Summary The effects of temperature, photoperiod, phytochrome photoreversion and the response to a R/FR ratio gradient were investigated in seeds of four species from two contrasting tropical habitats; two species from a rain forest (Cecropia obtusifolia and Piper umbellatum) and two from a high altitude lava field covered by low vegetation (Buddleja cordata and Chenopodium ambrosioides). In the rain forest seed species the photoblastic response seems to be adapted to light quality changes due to canopy destruction, on the other hand, the lava field seed species seem to be adapted to instantaneous light stimulus such as would be produced by the sudden exposure of a buried seed to the soil surface light environment.     

Invasion of an exotic forb impacts reproductive success and site fidelity of a migratory songbird

Although exotic plant invasions threaten natural systems worldwide, we know little about the specific ecological impacts of invaders, including the magnitude of effects and underlying mechanisms. Exotic plants are likely to impact higher trophic levels when they overrun native plant communities, affecting habitat quality for breeding songbirds by altering food availability and/or nest predation levels. We studied chipping sparrows (Spizella passerina) breeding in savannas that were either dominated by native vegetation or invaded by spotted knapweed (Centaurea maculosa), an exotic forb that substantially reduces diversity and abundance of native herbaceous plant species. Chipping sparrows primarily nest in trees but forage on the ground, consuming seeds and arthropods. We found that predation rates did not differ between nests at knapweed and native sites. However, initiation of first nests was delayed at knapweed versus native sites, an effect frequently associated with low food availability. Our seasonal fecundity model indicated that breeding delays could translate to diminished fecundity, including dramatic declines in the incidence of double brooding. Site fidelity of breeding adults was also substantially reduced in knapweed compared to native habitats, as measured by return rates and shifts in territory locations between years. Declines in reproductive success and site fidelity were greater for yearling versus older birds, and knapweed invasion appeared to exacerbate differences between age classes. In addition, grasshoppers, which represent an important prey resource, were substantially reduced in knapweed versus native habitats. Our results strongly suggest that knapweed invasion can impact chipping sparrow populations by reducing food availability. Food chain effects may be an important mechanism by which strong plant invaders impact songbirds and other consumers.