Responses of two species of heathland rodents to habitat manipulation: Vegetation density thresholds and the habitat accommodation model

The abundance of two native rodent species, Rattus lutreolus and Pseudomys gracilicaudatus, has been shown to correlate with vegetation density in coastal wet heath. Fox's habitat accommodation model relates relative abundances of such small mammal species to heathland vegetation regeneration following disturbance. Implicit in the model is recognition that it is successional changes in vegetation, not time per se, that drives the responses of small mammal species along a regeneration axis. Using a brush‐cutter we deliberately removed approximately 85% of vegetation around trapping stations and recorded significant reductions in the abundance of both P. gracilicaudatus (an earlier‐stage colonizing species) and R. lutreolus (a late seral‐stage species). A significant decrease in the abundance of only the latter had been demonstrated previously when 60–70% of the vegetation had been removed. Following the brush‐cutting both species re‐entered the mammalian secondary succession at different times, first P. gracilicaudatus followed by R. lutreolus after the vegetation cover thresholds of each species had been reached. The impact of this habitat manipulation experiment was to produce a retrogression of the small mammal succession, experimentally demonstrating causality between changes in vegetation density and subsequent small mammal habitat use.     

Competitive effects of Rattus lutreolus presence on food resource use by Pseudomys gracilicaudatus

Abstract We examined faecal samples of the eastern chestnut mouse (Pseudomys gracilicaudatus) that were collected during a removal experiment conducted in a coastal heathland at Myall Lakes National Park to see whether removal of the swamp rat (Rattus lutreolus) had any effects on food resource use by P. gracilicaudatus. The results showed that, at the young successional stage of vegetation (1. 5 years since last fire), the diet of P. gracilicaudatus changed significantly after the number of R. lutreolus was significantly reduced on the experimental sites. Two months after the removal treatment was terminated there were no significant differences between the control and experimental sites. Factor analysis showed that seasonal change was significant for all three food factors on the control sites, whereas on experimental sites the change was significant only for factor 1. At the middle successional stage (3.5 years since last fire), P. gracilicaudatus showed relatively small seasonal changes on both control and experimental sites, and significant differences between the control and experimental sites did not occur until after the removal manipulation was completed, showing a delayed response. Comparisons of the young and the middle successional stages on both control and experimental sites showed that P. gracilicaudatus used proportionally different food when R. lutreolus was present, but consumed similar food when R. lutreolus was removed. These results suggest that R. lutreolus might have restricted the access of P. gracilicaudatus to better microhabitats, and hence to a better food supply. The ecological implication of these results is that the interpretation of observed population and community patterns must take into account the direct effects of species interactions.     

Small mammal succession is determined by vegetation density rather than time elapsed since disturbance

Abstract We examined post‐fire responses of two sympatric Australian rodents, Pseudomys gracilicaudatus and Rattus lutreolus, as coastal wet heath regenerated following two high intensity wildfires. Pseudomys gracilicaudatus, an early serai‐stage species, recolonized an area burnt in August 1974 after one year, but took only 3 months to recolonize another area following a wildfire in October 1994. Rattus lutreolus, a late serai‐stage specialist, took approximately 3.6 years to recolonize following wildfire in August 1974, but had recolonized after only 4 months following wildfire in October 1994. We suggest that this apparent anomaly is associated with the rate of recovery of vegetation density. When the relative abundance of each species was plotted as a function of vegetation density, the trajectories following the two wildfires were concordant. An implicit relationship exists between time since wildfire and vegetation density. We make this relationship explicit by quantifying cover requirements for each species, and show that it is the resource continuum borne of regenerating vegetation (rather than time per se) that is important in determining the timing of small mammal successional sequences.     

Habitat utilization patterns of sympatric populations of Pseudomys gracilicaudatus and Rattus lutreolus in coastal heathland: A multivariate analysis

Abstract Habitat usage characteristics of two species of native murid rodents, Pseudomys gracilicaudatus and Rattus lutreolus were investigated on an area of coastal heathland at Myall Lakes National Park. A grid of 151 trap stations comprising 17 traplines was positioned across a mosaic of habitats. At each trap station 19 structural vegetation and physical variables known to affect the microdistribution of small mammals were measured. Multivariate statistical procedures identified those microhabitat variables that contribute to individual species' habitat use and habitat partitioning, and reduce potential competition for space. Cluster analysis classified trap stations into one of six habitat types that were mapped on the study area, identifying a heterogeneous assemblage of interlocking habitats. The pattern is a consequence of topographic variation on the site and, to a lesser extent, its fire history. Trapping results show P. gracilicaudatus and R. lutreolus exhibit similar macrohabitat selection, preferring topographically low habitats, with both species predominantly occupying short dense heath with dense sedge cover. The high overlap in macrohabitat use is greatly reduced when considered trap station by trap station, so that discriminant function and multiple regression analyses demonstrate marked microhabitat selection. Elevation was a highly significant variable, accounting for 41% and 27% of the variance in the habitat used by P. gracilicaudatus and R. lutreolus, respectively. This variable represents a soil moisture gradient that determines changes in the floristic and structural components of the biotic environment. Two other structural vegetation variables and vegetation height contributed 30% of the variance in P. gracilicaudatus distribution. Sedge cover was found to be significant and explained 13% of the variance in R. lutreolus distribution. Within-habitat separation was explained best with a linear combination of variables in a discriminant function, rather than by any single variable. Differential microhabitat selection, interference competition and diet separation appear to be the major factors facilitating coexistence of these two species.     

Interspecific competition: A mechanism for rodent succession after fire in wet heathland

Abstract A competitive interaction between two species of sympatric native rodents was demonstrated experimentally in Myall Lakes National Park (NSW, Australia). The previously documented replacement of Pseudomys gracilicaudatus by Rattus lutreolus in areas of wet heath in this region implied that competition may be the mechanism facilitating this succession. We present experimental evidence to support this suggestion. Removal of the larger R. lutreolus caused a significant increase in abundance of P. gracilicaudatus on five experimental sites in comparison to five unmanipulated control sites. The sites used in this experiment were chosen from three ages of wet heath regenerating after fire. These three ages represent key stages in the replacement of P. gracilicaudatus by R. lutreolus and the occurrence of competition in each of these ages indicates that competition plays an important role in this succession. In the initial stages of the experiment when R. lutreolus were removed they were replaced by new R. lutreolus individuals. This has been interpreted as evidence of strong intraspecific competition. After removal of R. lutreolus, P. gracilicaudatus expanded its habitat range into microhabitats that had formerly been occupied by R. lutreolus and reduced its range in microhabitats previously occupied by P. gracilicaudatus. This leads us to believe that P. gracilicaudatus was occupying inferior microhabitat before the removal of R. lutreolus, which had excluded it from more preferable microhabitat.     

Mycophagy in small mammals: A comparison of the occurrence and diversity of hypogeal fungi in the diet of the long-nosed potoroo Potorous tridactylus and the bush rat Rattus fuscipes from southwestern Victoria,Australia

Abstract Three broad dietary categories—fungus, plant and arthropod—were identified from faecal samples of two species of small terrestrial mammal in forest vegetation in southwestern Victoria. Fungal material formed the major component of the diet of the long-nosed potoroo Potorous tridactylus throughout the year and of the bush rat Rattus fuscipes during autumn and winter. Fungal material was most abundant for both species during autumn and winter and significantly less common in spring and summer. These results confirm previous studies which found P. tridactylus to be highly mycophagous throughout the year and R. fuscipes to be strongly mycophagous seasonally. Particular consideration was given to the composition of fungi in the diet. Fungal spores in faecal material were assigned to spore classes, which represent one or more fungal species that have similar spore morphology. Twenty-four fungal spore classes were recorded, but for both animal species most of the fungi consumed were from seven major spore classes. The proportions of major spore classes in the diet of both animals were generally similar, even though the composition of spore classes differed markedly across seasons. Minor differences between species in the fungi consumed may be related to differences in selectivity, foraging, or microhabitat use. If fungal resources are limiting, competition for such resources may be important in this and other small mammal communities. The amount and diversity of hypogeal fungi consumed by the two animal species makes them both important spore dispersal agents in forest ecosystems. The capacity of R. fuscipes and other seasonally mycophagous mammals in this role may be more important than previously recognized, especially in habitats where species of the Potoroidae are absent.     

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.     

Seasonal Variation in the Diets of Bluefish, Pomatomus saltatrix (Pomatomidae) and Striped Weakfish, Cynoscion guatucupa (Sciaenidae) in Southern Brazil: Implications of Food Partitioning

The stomach contents of 516 Pomatomus saltatrix and 506 Cynoscion guatucupa from southern Brazil were examined. Both species preyed primarily upon teleosts and crustaceans and occasionally squid. Seasonal variation in the diet was related to prey availability in the area, confirming the opportunistic feeding behaviour of both species. During the summer, P. saltatrix preyed upon four prey species (Loligo sanpaulensis, Artemesia longinaris, Mullus argentinae and Paralonchurus brasiliensis), whereas in the autumn and winter Engraulis anchoita was the predominant prey. C. guatucupa similarly preyed upon A. longinaris and P. brasiliensis during the summer, with juvenile C. guatucupa and E. anchoita also consumed. The latter species was an important dietary constituent during other seasons, as were A. longinaris (autumn), Umbrina canosai (winter), Trachurus latami and euphausids (spring). Although P. saltatrix had a broader diet than C. guatucupa during the summer, the latter species had a broader diet overall. Diet breadths were lower from autumn to spring, due to the predominance of E. anchoita in the diet of both species. This restricted diet resulted in significant intra- and inter-specific diet overlap during the winter but, because of the seasonal abundance of E. anchoita, the high levels of diet overlap do not necessarily indicate competition.     

Feeding activity and dietary composition of roe deer at the southern edge of their range

We studied feeding activity and dietary components of hand-reared European roe deer (Capreolus capreolus) in Israel. Our ultimate goal was to assess habitat suitability for future reintroduction of the species, which has been locally extinct for nearly a century. Activity patterns, diet composition, and body mass of four does were monitored in two (fenced) typical east Mediterranean habitats: mature forest and scrubland recovering from fire. Food supplements were provided between trials. Throughout the year, the deer exhibited diurnal and nocturnal activity, mostly at dawn and dusk. Diet composition varied considerably between seasons and habitats, demonstrating the opportunistic flexibility of the deer. In both habitats, the deer fed on over 85% of the plant species but preferred a particular plant species or parts. In summer and early autumn, fruits and seeds became the dominant portion of their diet. In our semi-natural experimental setup, deer maintained body mass through the winter and spring. Weight loss occurred as the dry season advanced, but the animals rapidly regained mass when annuals and grasses became available following the first rains. In the east Mediterranean habitats, water availability seems more problematic for deer survival than food availability.     

Diet overlap between small ruminants and the European hare in a Mediterranean shrubland

Seasonal diets of goats, sheep and European hares (Lepus europaeus) were examined using microhistological analysis of feces collected when these herbivores grazed together in a typical Mediterranean shrubland. Approximately half of the total diet content of goats was shrubs (mainly kermes oak, Quercus coccifera), while that of hares was grasses (mostly brush grass, Chrysopogon gryllus). Sheep had a more balanced diet consisting mainly of grasses, forbs, and shrubs. Dietary overlap between goats and sheep was high throughout the year. In contrast, there was very low dietary overlap between small ruminants and hares. Dietary diversity was high in spring and low in winter across all species, with sheep in general displaying higher dietary diversity across all seasons than goats and hares. Goats had intermediate and hares had low dietary diversity across all seasons. Communal grazing by small ruminants and hares ensures that there is a more uniform use of the available forage resources than if a single herbivore is left to graze an area.     

Seasonal food habits of corsac and red foxes in Mongolia and the potential for competition

Competition often occurs between sympatric species that exploit similar ecological niches. Among canids, competition may be reduced by partitioning resources such as food, time, and habitat, but the mechanisms of coexistence remain poorly understood, particularly among fox species. We described the food habits of two foxes that live sympatrically across northern and central Asia, the corsac fox (Vulpes corsac) and red fox (V. vulpes), by analyzing scats collected during a field study in Mongolia. We analyzed 829 corsac and 995 red fox scats collected from April 2005 to August 2007 and tested the extent to which food partitioning occurred. The diets of both species consisted mainly of insects followed by rodents, but also included birds, reptiles, large mammal remains (carrion), plant material (including fruits and seeds), and garbage. Despite high overlap in the proportion of food items consumed, differences existed between species in overall diet with corsacs more frequently consuming beetles, but proportionally fewer crickets and large mammal remains than red foxes. We detected interspecific differences during the pup rearing and dispersal seasons, when prey was abundant, but not during the breeding season, when prey was scarce and diet overlap highest. Each species’ diet also differed seasonally and exhibited moderate overall breadth. Corsacs consumed proportionally more beetles and rodents during pup rearing and crickets during dispersal relative to other seasons, whereas red foxes consumed proportionally more crickets during pup rearing and dispersal and more rodents and large mammals during pup rearing and breeding relative to other seasons. Our results suggest that partitioning of food resources during most of the year facilitates coexistence, and that the potential for competition is highest during winter months.     

Dietary diversity of an ecological and macronutritional generalist primate in a harsh high‐latitude habitat,the Taihangshan macaque (Macaca mulatta tcheliensis)

Recent advances in niche theory have stressed the importance of understanding dietary generalism at multiple levels, including the range of habitat and foods exploited by a species, foods exploited within populations, and patterns of nutrient intake. Here we apply this framework to examine the dietary strategy of the Macaca mulatta, a primate species that is second only to humans in their breadth of geographical distribution, and occupy diverse ecological habitats from cold temperate to tropical latitudes. A recent study showed that the Taihangshan subspecies ( M. mulatta tcheliensis) in China, which is found at the northern latitudinal limit of the species range, respond to ecologically constrained interannual variation in the macronutrient ratios of the spring diet in a way that theory predicts should be associated with ecological generalism. Here we further extend this study, examining the relationships between seasonal variation in food availability and the patterns of food selection across a full year. We found that, despite the ecological and macronutritional generalism of the species, Taihangshan macaques subsist on a relatively small range of foods (57 different foods, spread across 8 categories comprising seeds, fruits, buds, flowers, leaves, herbs, young bark, and twigs), but face considerable seasonal variation in the combinations available. In spring and summer, when seeds were scarce, leaves accounted for 60.3 ± 13.8% of their diet (dry matter [DM] %), and herbs contributed 31.7 ± 22.2%. However, in autumn and winter, when seeds were abundant, they contributed 68.5 ± 22.7% of the diet while herbs accounted for 18.9 ± 12.9% on a DM. Although young bark and twigs were available in all seasons, the macaques only fed on them in winter. We present comparative data from the literature on the diets of M. mulatta and other Macaca species, to interpret this pattern of resource use within the framework of multilevel niche theory.     

Diet of the mara (Dolichotis patagonum), food availability and effects of an extended drought in Northern Patagonia (Mendoza,Argentina)

The mara is a near threatened Caviomorph, endemic to Argentina. Studies on feeding ecology allow assessment of the dietary adaptability of maras to habitat changes. The mara diet and food availability on two sampling sites, belonging to distinct landscapes of Northern Patagonia, were estimated using microhistological analysis and point-quadrat transects, over four seasons, and besides during an extended drought. Significant differences were detected by Kruskall-Wallis ANOVA, feeding selection by the χ² test, and dietary preferences by Bailey's confidence interval. Grasses dominated food availability, with Panicum and Poa as major species, followed by shrubs and scarce forbs. Plant cover and forbs increased in spring and summer. The drought caused a strong decrease in plant cover and proportion of grasses. Maras ate all grass species, most forbs and several shrubs. Grasses dominated the diet, with Poa and Panicum being the major species, supplemented by the shrubs Lycium and Prosopis. Maras ate more grasses and forbs in spring and summer, and shrubs in autumn and winter. More shrubs and forbs, and less grasses, were eaten during the drought. Plant categories were used selectively only in autumn and winter, and in the drought period, with preference for shrubs and avoidance of grasses. Bromus, Poa, Plantago and Prosopis were preferred, and Panicum avoided. The mara qualified as a grazer but shifted to a mixed feeder during the drought. Dolichotis patagonum shared habitats with several big and medium-sized herbivores and showed the highest dietary similarities with plain vizcachas, brown hares and horses. Protective measures for natural habitats are needed, given that increasing impacts on food resources and habitat quality could be threats to the survival of maras and other wild vertebrates in Northern Patagonia.     

Dietary overlap and seasonality in three species of mormoopid bats from a tropical dry forest

Competing hypotheses explaining species’ use of resources have been advanced. Resource limitations in habitat and/or food are factors that affect assemblages of species. These limitations could drive the evolution of morphological and/or behavioural specialization, permitting the coexistence of closely related species through resource partitioning and niche differentiation. Alternatively, when resources are unlimited, fluctuations in resources availability will cause concomitant shifts in resource use regardless of species identity. Here, we used next‐generation sequencing to test these hypotheses and characterize the diversity, overlap and seasonal variation in the diet of three species of insectivorous bats of the genus Pteronotus. We identified 465 prey (MOTUs) in the guano of 192 individuals. Lepidoptera and Diptera represented the most consumed insect orders. Diet of bats exhibited a moderate level of overlap, with the highest value between Pteronotus parnellii and Pteronotus personatus in the wet season. We found higher dietary overlap between species during the same seasons than within any single species across seasons. This suggests that diets of the three species are driven more by prey availability than by any particular predator‐specific characteristic. P. davyi and P. personatus increased their dietary breadth during the dry season, whereas P. parnellii diet was broader and had the highest effective number of prey species in all seasons. This supports the existence of dietary flexibility in generalist bats and dietary niche overlapping among groups of closely related species in highly seasonal ecosystems. Moreover, the abundance and availability of insect prey may drive the diet of insectivores.     

For everything a season: Smoke-induced seed germination and seedling recruitment in a Western Australian Banksia woodland

Abstract The influence of factors associated with fire on seed germination of Australian native species is generally well documented, but examples involving the use of smoke as a fire analogue for ecological research remain limited. The role of season of treatment in the efficacy of smoke as a promotive germination agent was investigated over two growing seasons using natural soil stored seedbanks in Banksia woodland near Perth, Western Australia. Smoke was applied to unburnt sites in the autumn, winter and spring of 1994. Germinant emergence and seedling survival of 37 species representing 18 families was monitored in both unburnt sites and in adjacent, recently burnt sites until the second spring after treatment (October 1995). Recruitment from seed was found to be profoundly affected by the season in which dormancy breaking treatment had been applied. The promotive effect extended beyond the initial year of application. For the majority of the species investigated, application of smoke to unburnt sites in autumn promoted a significantly greater germination response than treatment in winter or spring. In only three cases (introduced annuals, the Fabaceae and Hibbenia amplexicaulis) did autumn smoke treatment not yield better germination than in summer-burnt counterparts. However, in almost half of the cases examined, proportions of seedlings surviving past their first summer after emergence in burnt areas were consistently greater than those in smoked or untreated sites. Most notably, no seedlings emerging during the spring of the first year of study survived into the following summer. Implications of the results with respect to future seed bank research and management of native vegetation are discussed.     

Dietary breadth and resource use of François' langur in a seasonal and disturbed habitat

Previous studies of Trachypithecus species indicated that they were selective feeders that concentrated on relatively few food species/items. From January to December 2005, I quantified potential food availability and the food species/items eaten by five groups of François' langur (Trachypithecus francoisi) in the Mayanghe Nature Reserve (MNR), People's Republic of China. These langurs fed on 164 species, of which the top ten accounted for 51% of all feeding records. Langurs consumed more species (91) in the spring than in other seasons (73 summer, 75 autumn, and 67 winter), and only 38 species were consumed in all seasons. Nontree food species, such as bushes and lianas, accounted for 47% of the total feeding records and for a majority (68%) of the feeding records in winter. The annual diet consisted of leaves (64% of feeding records), fruit and seed (32%), and other nonfoliage items (4%); the langurs switched from being more folivorous in spring (93%) and summer (79%) to being more frugivorous in autumn (53%) and winter (56%). There was no correlation between the proportion of feeding records and the food availability in the most frequently consumed species, indicating that these langurs were selective feeders; there were significant correlations between consumption and abundance in both the entire set of 112 food species and the set of 86 infrequently consumed species, indicating that foods that are more available are eaten more frequently. It appeared that in the seasonal and disturbed habitat, feeding decisions and diet composition of the langur may be driven more by food availability, and less by animal's selectivity, than at other sites. The results indicate that François' langur copes with habitat alterations by broaden its dietary breadth; this has implications for the adaptive significance of dietary breadth, and has implications for future conservation strategies for species which exist in degraded habitats. Am. J. Primatol. 73:1176–1187, 2011. © 2011 Wiley Periodicals, Inc.     

Diet and feeding strategy of blackmouth catshark Galeus melastomus

Diet and feeding strategy of the blackmouth catshark Galeus melastomus in the deep waters of the eastern Ionian Sea were investigated. Sampling was carried out using experimental bottom longline fishing at depths ranging from 300 to 855 m in summer and autumn 2010. Diet variability with fish size, season, area, sex and depth zone was tested and only season was found to significantly affect the diet of the species. Of the 870 stomachs examined, only 1·4% were empty. Cumulative prey curves showed that the sample sizes were adequate to describe the main prey items of the diet for both seasons. Prey identified belonged primarily to three major groups: fishes, cephalopods and dendrobranchiatan and caridean shrimps. In autumn, the above three major groups were found as principal prey, whereas in summer cephalopods followed by fishes were the principal prey and shrimps were found as secondary prey. SIMPER analysis indicated high dissimilarity between seasons and highlighted that Sepiolidae, Myctophidae, fishes, cephalopods, shrimps and other crustaceans contributed to seasonal differences in the diet of G. melastomus. The prey diversity index was higher in autumn than in summer. A high dietary overlap was observed between the two seasons. Galeus melastomus behaved as an opportunistic predator with a variety of unimportant prey in its diet. Feeding strategy indicated that G. melastomus holds a generalist niche with a considerable specialization at the individual level. This strategy seems to be an adaptation to a food‐scarce environment, as typified in deep‐water habitats.     

Seasonal variations in food resource partitioning among four sympatric gudgeon species in the upper Yangtze River

Knowledge of food resource partitioning among sympatric fish species is crucial for understanding the potential mechanisms of species coexistence. Gudgeons (Teleostei: Cyprinidae: Gobioninae) often dominate fish assemblages in the upper Yangtze River. However, little research has been conducted on their trophic interactions. In this paper, seasonal diet and feeding strategy variations of four sympatric gudgeon species, Coreius guichenoti, Coreius heterodon, Rhinogobio ventralis, and Rhinogobio cylindricus, were investigated by analysis of intestinal tract contents, aiming to explore whether food resource partitioning occurred among them. Fish specimens were collected during spring (April–May) and autumn (August–October) in 2010 in Hejiang, a free‐flowing stretch of the upper Yangtze River. Coreius guichenoti, C. heterodon, and R. cylindricus showed omnivorous feeding habits, while R. ventralis exhibited an obligate carnivore feeding habit. Diet overlap among the four studied species was high, especially in spring. However, changes in feeding strategies were observed in autumn. Specifically, C. guichenoti and R. cylindricus expanded their dietary niche breadth and consumed detritus, Sinopotamidae or Hydropsychidae as important complementary food resources. In contrast, C. heterodon and R. ventralis reduced their dietary niche breadth and became more specialized on mussels (Limnoperna lacustris). These results confirmed that sympatric fish species can coexist with high diet overlap, and food resource partitioning among these species may also fluctuate with the seasons.     

Seasonal variation in the diet of South African Galagos

The feeding behavior and diet of two species of bushbaby, Galago senegalensisand Galago crassicaudatus,in South Africa were examined in relation to seasonal changes in climate. The populations studied were allopatric, but both fed predominantly on Acaciagum and invertebrates. Data on their diet were collected by direct observation of a radiocollared female of each species and by analysis of fecal samples. Differences in diet were found between the species within seasons and within species between the seasons. Both spent more time gum-feeding in winter than in summer. Prey size and type differed between the species in summer but converged in winter. The quantity of insects taken was fairly similar between seasons for G. senegalensisbut dropped considerably for G. crassicaudatusin winter. These observations are interpreted in terms of interspecific differences in feeding strategies, which are considered to be a function of the difference in body size of the two galago species.     

辽宁碱蓬根际土壤真菌多样性的季节变化及其耐盐性

采用稀释平板法和形态学鉴定法进行了辽宁碱蓬(Suaeda liaotungensis)根际土壤真菌的分离鉴定及季节、盐度对真菌多样性的影响分析。结果表明:春、夏、秋、冬四季辽宁碱蓬根际土壤中的真菌菌落数分别为6410、4180、5730和3340,种类分别为6属13种、9属16种、11属31种、6属12种,共分离鉴定出13属42种真菌;其根际土壤真菌的多样性指数、丰富度指数和均匀度指数,从大到小的次序均为秋夏春冬,3种指数均在秋季达到峰值;多样性指数和丰富度指数差异较大,均匀度指数波动较小,春季和冬季的均匀度指数相近。辽宁碱蓬根际土壤真菌种类明显多于无植被土壤,是无植被土壤的7倍,多样性指数和均匀度指数分别是无植被土壤的4—8倍和1—1.2倍;其根际土壤真菌优势种群包括青霉属(Penicillium)、葡萄穗霉属(Stachybotrys)、枝孢属(Cladosporium)、木霉属(Trichoderma)、曲霉属(Aspergillus)和镰孢属(Fusarium);4个季节的优势菌不尽相同,但均有一个共同的优势菌属青霉属。以Na Cl浓度梯度法制造盐胁迫生境,检测辽宁碱蓬根际土壤真菌对盐胁迫的响应,结果表明:60%左右的菌种能耐受5%以下盐度、15%左右的菌种能耐10%—20%盐度;筛选出了6株高度耐盐菌:细交链孢霉、草酸青霉、产黄青霉、烟曲霉、细极链格孢和赭曲霉,其中最高耐盐菌种赭曲霉可耐20%盐度。创新之处在于以盐度和季节为变量检测辽宁碱蓬根际土壤真菌的种群构成,为其深入研究奠定了理论基础。