Structure in a desert rodent community: use of space around Dipodomys spectabilis mounds

Summary In an earlier paper (Bowers et al. 1987) we reported patterns of microhabitat use by desert rodents among 0.25-ha plots where seeds were added or certain rodent species removed. We used the results to make inferences about the spatial organization of the whole rodent community. Here we change our focus to test for spatial usage patterns at a smaller (within-plot) scale. Specifically, we examine to what extent spatial use varies with proximity to mounded burrows of the large kangaroo rat, Dipodomys spectabilis. Capture frequency of five of nine rodent species was correlated with distance from D. spectabilis mounds, while six species showed correlations with vegetative cover that also increased with distance from mounds. In general, sites nearer mounds were underutilized, and sites further away overutilized by the rodent community as a whole. Logistic regression analyses showed for six species that vegetative cover and particularly, distance to nearest mound accounted for more of the variation in whether a station captured a species than did plot-to-plot (i.e., treatment) effects. Similar analyses using two plots where D. spectabilis was removed (where vacant mounds persited for years) suggested that the selection of microhabitats with contrasting vegetation structure was more pronounced in the absence than in the presence of D. spectabilis, and that in most cases distance from mounds was important only if mounds were occupied. Spatial structure in this community appears to revolve around the occupation of space by dominant individuals that partially modify/obscure large scale patterns involving the selection of particular structural microhabitats.     

Small-scale indirect effects determine the outcome of a tripartite plant–disperser–granivore interaction

The microhabitat in which plants grow affects the outcome of their interactions with animals, particularly non-specialist consumers. Nevertheless, as most research on this topic has dealt with either mutualists or antagonists, little is known about the indirect effects of plant microhabitats on the outcome of tripartite interactions involving plants and both mutualists (e.g. seed dispersers) and antagonists (e.g. granivores). During three consecutive years, we analysed small-scale variations in the interaction of a perennial myrmecochore, Helleborus foetidus, with its seed dispersers and consumers as a function of the intensity of plant cover. Most seeds were released during the day and were rapidly removed by ants. Nevertheless, the proportion of ant-removed seeds was higher for plants located in open microhabitats than for plants surrounded by dense vegetation and rocky cover. Ant sampling revealed that seed removers were equally abundant, irrespective of the level of cover. By contrast, a few tiny ant species that feed on the reward without transporting the seeds were more abundant in highly covered microhabitats, irrespective of hellebore diaspore availability. These “cheaters” decrease the chance of removal by removers and increase the probability of seeds remaining on the ground until night, when granivore mice Apodemus sylvaticus become active. Mice also preferred foraging in covered microhabitats, where they consumed a larger proportion of seeds. Therefore, the density of cover indirectly increased seed predation risk by attracting more seed predators and cheater ants that contribute to increase seed availability for seed predators. Our results emphasize the importance of considering the indirect effects of plant microhabitat on their dispersal success. They highlight the indirect effect of cheaters that are likely to interfere in mutualisms and may lead to their collapse unless external factors such as spatio-temporal heterogeneity in seed availability constrain their effect. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Microhabitat use in coexisting desert rodents—The role of population density

Summary Among some species of Sonoran Desert rodents microhabitat differences are density dependent. I studied the differences in microhabitat use among four species of heteromyid rodents (Dipodomys merriami, Perognathus amplus, P. baileyi, and P. penicillatus) at low and at high population densities. Microhabitats are defined by the abundance and size distribution of desert shrubs. During a period of low population density the rodent species showed substantial microhabitat differentiation. Following a large increase in pocket mouse (Perognathus spp.) numbers differences in microhabitat use between species disappeared. The lack of microhabitat differentiation at high density is due to microhabitat shifts rather than an expansion in the number of microhabitats used. The shifts lead to increased similarity among species in microhabitat use. Microhabitat overlap is not constant but it is highly variable and sensitive to changes in rodent abundance.     

What are the consequences of ant–seed interactions on the abundance of two dry-fruited shrubs in a Mediterranean scrub?

Strong interactions between dry-fruited shrubs and seed-harvesting ants are expected in early successional scrubs, where both groups have a major presence. We have analysed the implications of the seed characteristics of two dry-fruited shrub species (Coronilla minima and Dorycnium pentaphyllum) on seed predation and dispersal mediated by harvester ants and the consequences of these processes on spatio-temporal patterns of plant abundance in a heterogeneous environment. We found that large C. minima seeds were collected much more (39%) than small D. pentaphyllum seeds (2%). However, not all of the removed seeds of these plant species were consumed, and 12.8% of the seeds were lost along the trails, which increased dispersal distances compared with abiotic dispersal alone. Seed dropping occurred among all microhabitats of the two plant species, but especially in open microhabitats, which are the most suitable ones for plant establishment. The two plant species increased their presence in the study area during the study period: C. minima in open microhabitats and D. pentaphyllum in high vegetation. The large size of C. minima seeds probably limited the primary seed dispersal of this species, but may have allowed strong interaction with ants. Thus, seed dispersal by ants resulted in C. minima seeds reaching more suitable microhabitats by means of increasing dispersal distance and redistribution among microhabitats. In contrast, the smaller size of D. pentaphyllum seeds arguably allows abiotic seed dispersal over longer distances and colonization of all types of microhabitats, although it probably also limits their interaction with ants and, consequently, their redistribution in suitable microhabitats. We suggest that dyszoochory could contribute to the success of plant species with different seed characteristics in scrub habitats where seeds are abundantly collected by seed-harvesting ants.     

The effects of food presentation and microhabitat upon resource monopoly in a ground-foraging ant (Hymenoptera: Formicidae) community

In Neotropical wet forests several species of omnivorous, resource-defending ants, live and forage in close proximity to one another. Although the forest floor is heterogeneous in microhabitat and food quantity, little is known about the impact of microhabitat and food variation upon resource monopoly among ants. We investigated how food type and microhabitat influence food monopoly in resource-defending ants in old-growth tropical wet forest in the Caribbean lowlands of Costa Rica. We measured several microhabitat characteristics at 66 points in a 0.5 hectare plot, and baited each point with two categories of tuna bait. These baits were presented in "split" and "clumped" arrangements. We measured the frequency of bait monopoly by a single species, as well as the number of recruited ant foragers at a bait. Out of five common species, two (Wasmannia auropunctata and Pheidole simonsi) more frequently monopolized one bait type over the other, and one (P. simonsi) recruited more ants to the split baits. We then considered the recruitment response by all ant species in the community. We found that the frequency of monopoly, sharing, and the absence of ants at a given point in the rainforest differed with bait type. The frequency of monopoly was associated with microhabitat type in two out of eight microhabitat variables (leaf litter depth and palms); variation in two other types (canopy tree distance and leafcutter ant trails) was associated with changes in forager number. In at least two ant species, food presentation affected monopoly at baits; among all resource-defending ants, the microhabitats where ants foraged for food and the type of food located determined in part the frequency of monopoly and the number of foragers at the food item. These results suggest that the location and presentation of food items determines in part which ant species will utilize the resource.     

Post-dispersal seed predation and the establishment of vertebrate dispersed plants in Mediterranean scrublands

The post-dispersal fate of seeds and fruit (diaspores) of three vertebrate-dispersed trees, Crataegus monogyna, Prunus mahaleb and Taxus baccata, was studied in the Andalusian highlands, south-eastern Spain. Exclosures were used to quantify separately the impact of vertebrates and invertebrates on seed removal in relation to diaspore density and microhabitat. The three plant species showed marked differences in the percentage of diaspores removed, ranging from only 5% for C. monogyna to 87% for T. baccata. Although chaffinches (Fringilla coelebs) fed on diaspores, rodents (Apodemus sylvaticus) were the main vertebrate removers of seed and fruit. Two species of ant (Cataglyphis velox and Aphaenogaster iberica) were the only invertebrates observed to remove diaspores. However, the impact of ants was strongly seasonal and they only removed P. mahaleb fruit to any significant extent. While removal of seed by rodents was equivalent to predation, ants were responsible for secondary dispersal. However, their role was limited to infrequent, small-scale redistribution of fruit in the vicinity of parent trees. Rodents and ants differed in their use of different microhabitats. Rodents foraged mostly beneath trees and low shrubs and avoided open areas while the reverse was true of ants. Thus, patterns of post-dispersal seed removal will be contigent on the relative abundance and distribution of ants and rodents. Studies which neglect to quantify separately the impacts of these two guilds of seed removers may fail to elucidate the mechanisms underlying patterns of post-dispersal seed removal. The coincidence of both increased seed deposition by the main avian dispersers (Turdus spp.) and increased seed predation with increasing vegetation height suggested that selection pressures other than post-dispersal seed predation shape the spatial pattern of seed dispersal. Rather than providing a means of escaping post-dispersal seed predators, dispersal appears to direct seeds to microhabitats most suitable for seedling survival. Nevertheless, the reliance of most vertebrate-dispersed trees on regeneration by seed and the absence of persistent soil seed banks imply that post-dispersal seed predators may exert a strong influence on the demography of the plants whose seeds they consume. Even where microsites are limited, the coincidence of the most suitable microhabitats for seedling establishment with those where seed predation is highest provide a means by which selective seed predators can influence community composition. Received: 19 August 1996 / Accepted: 25 January 1997     

Influence of small-scale disturbances by kangaroo rats on Chihuahuan Desert ants

Banner-tailed kangaroo rats (Dipodomys spectabilis) are prominent ecosystem engineers that build large mounds that influence the spatial structuring of fungi, plants, and some ground-dwelling animals. Ants are diverse and functionally important components of arid ecosystems; some species are also ecosystem engineers. We investigated the effects of patch disturbances created by D. spectabilis mounds on ant assemblages in a Chihuahuan Desert grassland in southern New Mexico by using pitfall traps in a paired design (mound vs. matrix). Although the disturbances did not alter species richness or harbor unique ant communities relative to the matrix, they did alter species composition; the abundances of 6 of 26 species were affected. The disturbances might also act to disrupt spatial patterning of ants caused by other environmental gradients. In contrast to previous investigations of larger-scale disturbances, we detected no effects of the disturbances on ants at the functional-group level. Whether ant communities respond to disturbance at a functional-group or within-functional-group level may depend on the size and intensity of the disturbance. Useful functional-group schemes also may be scale-dependent, however, or species may respond idiosyncratically. Interactions between disturbance-generating mammals and ants may produce a nested spatial structure of patches. Received: 11 October 1999 / Accepted: 11 March 2000     

An Experimental Study of Competition Between Seed-eating Desert Rodents and Ants

Reciprocal increases in rodent and ant densities on 0.1 ha plotsfrom which the other taxon had been excluded demonstrate thatthese distantly related desert granivores compete for seeds.Relative to unmanipulated control plots, numbers of ant coloniesincreased 71% on plots where rodents were excluded; rodentsincreased 20% in numbers of individuals and 29% in biomass inthe absence of ants. Comparisons of seed levels in the soiland of annual plant densities on experimental and control plotsprovide evidence that the rodent and ant populations are limitedby and compete for food. Greater numbers of seeds and annualsoccurred on plots where rodents and ants had been excluded thanon plots where both taxa were present. Particular species ofannuals were reduced in density by foraging of rodents. Antsincreased species diversity by differentially harvesting seedsof the most common species. Results of these and other recentstudies suggest that competition among distantly related organismsplays a major role in the organization of ecological communities.     

Functional extinction of a desert rodent: implications for seed fate and vegetation dynamics

Population declines of once‐abundant species have often preceded understanding of their roles within ecosystems. Consequently, important drivers of environmental change may remain undiagnosed because we simply do not know how species that are now rare or extinct shaped ecosystems in the past. Australia's desert rodents are thought to have little numerical impact on seed fate and vegetation recruitment when compared with ants or with desert rodents on other continents. However most research on granivory by Australian desert rodents has occurred in areas where rodents were rare or functionally extinct. Here we ask if the paradigm that rodents are relatively un‐important granivores in Australian deserts is an artefact of their historical decline. In the Strzelecki Desert, the endangered rodent, Notomys fuscus is rare where introduced mesopredators are abundant but common where dingoes (an apex predator) suppress mesopredator populations. We used foraging trays to compare rates of seed removal for a common shrub (Dodonaea viscosa angustissima hopbush) between areas where N. fuscus, hopbush shrubs and their seedlings were rare and common and found that seed removal was consistently higher where rodents were common and hopbush rare. By excluding ants and rodents from foraging trays we show that ants removed more seeds than rodents where rodents were rare but rodents removed far more seeds than ants where rodents were common. By manipulating rodents’ access to the soil seed‐bank we show that hopbush seeds persisted in greater numbers where rodents were excluded than where they had access. Our results support the hypothesis that granivory by rodents may once have been a far more important process influencing the fate of seeds and shaping plant communities in arid Australia and suggest that dingo extirpation has cascading effects on shrub seeds. Our study highlights that functional extinction of rodents may be an under‐appreciated driver of vegetation change.     

Microhabitat selection in two species of heteromyid rodents

Summary An experiment was conducted to determine the microhabitat preferences of two heteromyid rodents, Dipodomys ordi and Perognathus flavus. This experiment used marked seeds and the atomic absorption spectrophotometer in order to study the environment as a mosiac of microhabitats. The results of our analysis indicate that these two heteromyids are microhabitat selectors. The preferences of the rodents are D. ordi: grass habitat 0.0%, near grass habitat 22.5%, open habitat 77.4% and P. flavus: grass habitat 46.2%, near grass habitat 32.2%, open habitat 21.4%. The overlap between the two species is only 0.43.     

Mechanisms affecting the fate of Prosopis flexuosa (Fabaceae,Mimosoideae) seeds during early secondary dispersal in the Monte Desert,Argentina

Abstract The fate of seeds during secondary dispersal is largely unknown for most species in most ecosystems. This paper deals with sources of seed output of Prosopis flexuosa D.C. (Fabaceae, Mimosoideae) from the surface soil seed‐bank. Prosopis flexuosa is the main tree species in the central Monte Desert, Argentina. In spite of occasional high fruit production, P. flexuosa seeds are not usually found in the soil, suggesting that this species does not form a persistent soil seed‐bank. The magnitude of removal by animals and germination of P. flexuosa seeds was experimentally analysed during the first stage of secondary dispersal (early autumn). The proportion of seeds removed by granivores was assessed by offering different types of diaspores: free seeds, seeds inside intact endocarps, pod segments consisting of 2–3 seeds, and seeds from faeces of one herbivorous hystricognath rodent, the mara (Dolichotis patagonum). The proportion of seeds lost through germination was measured for seeds inside intact endocarps, seeds inside artificially broken endocarps, and free seeds. Removal by ants and mammals is the main factor limiting the formation of a persistent soil seed‐bank of P. flexuosa: >90% of the offered seeds were removed within 24 h of exposure to granivores in three of four treatments. Seeds from the faeces of maras, on the other hand, were less vulnerable to granivory than were other types of diaspores. These results suggest that herbivory might be an indirect mechanism promoting seed longevity in the soil (and likely germination) by discouraging granivore attack. On the other hand, germination did not seem to have an important postdispersal impact on the persistence of P. flexuosa seeds in the soil. Both direct and indirect interactions between vertebrate herbivores and plants may foster P. flexuosa's seed germination in some South American arid zones.     

Chimpanzee (Pan troglodytes) Seed Dispersal in an Afromontane Forest: Microhabitat Influences on the Postdispersal Fate of Large Seeds1

We examined the postdispersal fate of large seeds (≥5 mm) dispersed by chimpanzees in an afromontane forest to evaluate aspects of the effectiveness of seed dispersal by chimpanzees, Pan troglodytes. We assessed the influence of six microhabitat characteristics on seed persistence and germination in seeds dispersed in chimpanzee feces and “wadges.” A total of 257 fecal samples and 56 wadges were located over a 4‐mo period by tracking a semi‐habituated chimpanzee community on day follows. Forty‐nine (19.1%) of the fecal samples contained large seeds from five different tree species. The majority of fecal samples with seeds contained seeds from the mature forest tree Olea capensis (Oleaceae) (83.7%). Forty‐two wadges (75%) contained seeds from the mature forest tree Syzygium guineense (Myrtaceae). Seeds were monitored at their deposition site for removal and germination up to 49 d following deposition. We collected data on the microhabitat surrounding each fecal and wadge sample. Multivariate analyses indicated that while fecal and wadge samples were not clustered into particular microhabitats, there was little overlap in the microhabitats in which wadges and fecal samples were deposited. Significantly more seeds persisted over 49 d in wadges (67.9%) than in feces (30.3%). Elevation was the only microhabitat variable determined to have a significant influence on seed persistence, whereas slope was determined to have a significant influence on germination.     

Clump size selection: A field test with two species of Dipodomys

Summary Seed distribution (clump size) selection has been proposed as a possible mechanism of resource subdivision for competing heteromyid rodent species. To test this hypothesis, field experiments were conducted over two years during both richer and sparser seasons of the year. None of the predictions derived from the hypothesis were supported by our results. Though some selectivity was displayed by both Dipodomys spectabilis and D. merriami, the patterns of selectivity did not match the expected patterns. Our results further indicate that clump selection may be influenced by variables other than the density of seeds within a clump. These results have led us to conclude that clump size selection is unlikely to play a role in the coexistence of different species of the genus Dipodomys.     

A multi-species assessment of post-dispersal seed predation in the central Chilean Andes

BACKGROUND AND AIMS: Post-dispersal seed predation in alpine communities has received little attention despite evidence that seeds removed by granivores can decrease plant recruitment into ecosystems. Moreover, few studies have assessed the effects of removal of seeds of a range of species after dispersal on the seeds remaining in ecosystems. A comparison was made of the magnitude of seed removal by ants and birds of nine different shrubby-, herbaceous- and cushion-plant species in the central Chilean Andes in order to assess the interactions between birds, ants and wind, and the types of seeds. METHODS: A total of 324 soil-covered plates, each containing 50 seeds of one species, were placed in the field at an altitude of 2700 m and assigned to one of four treatments: control, exclusion of ants, birds, and both. The design also allowed the effects of wind to be assessed. Seed removal from plates was monitored over 20 d. KEY RESULTS: Mean accumulative seed removal by granivores averaged over all nine species combined was 25%. However, large differences between species were evident, with limited seed removal (3-11%) in three herbaceous species (Alstroemeria pallida, Sisyrinchium arenarium, Pozoa coriacea), moderate (18-33%) in five species, including a shrub (Chuquiraga oppositifolia), two herbs (Taraxacum officinale, Rhodophiala rhodolirion), and two cushion-plants (Laretia acaulis, Azorella monantha), and substantial (78%) in the shrub Anarthrophyllum cumingii. The magnitudes of losses caused by birds compared with ants did not differ for the majority of species, although removal by birds was greater than by ants in A. cumingii, and smaller for C. oppositifolia. CONCLUSIONS: Post-dispersal seed removal is shown to be an important cause of decreased potential plant species recruitment into alpine ecosystems. The substantial differences in the magnitude of seed losses to ants and birds demonstrate the need for evaluation of seed removal on a wide range of species in any given ecosystem.     

Competitive release in microhabitat use among coexisting desert rodents: a natural experiment

Summary Competitive release among desert rodents on sand dunes of differing species richness was examined in the Great Basin and Mohave Deserts, USA. Expansions in microhabitat use were exhibited by the kangaroo rats Dipodomys ordii and D. merriami (granivorous heteromyid rodents, weighing 49 and 42 g, respectively) as the number of coexisting heteromyid species decreased geographically. Perognathus longimembris, the only common small heteromyid species (7 g) exhibited no competitive release. This may be due either to the absence of competitive interactions that affect the use of space by P. longimembris or to an unacceptable increase in risk of predation that precludes the use of more open microhabitats even in the absence of kangaroo rats. The breadth of microhabitat use of an omnivorous cricetid, Peromyscus maniculatus, decreased as the density of Perognathus longimembris increased, and increased as the density of conspecifics increased. The evidence for competitive release in Dipodomys and not in Perognathus is consistent with the hypothesis that species in the same guild and of similar size compete more intensely than species of disparate size.     

Response of lizard community structure to desert grassland restoration mediated by a keystone rodent

Many grasslands in the Chihuahuan Desert have transformed to shrublands dominated by creosotebush (Larrea tridentata). Grassland restoration efforts have been directed at controlling creosotebush by applying herbicide over large spatial scales. However, we have a limited understanding of how landscape-scale restoration affects biodiversity. We examined whether restoration treatments in southern New Mexico, USA have influenced the community structure of lizards, which are sensitive to shrub encroachment. We compared lizard community structure on 21 areas treated with herbicide from 7 to 29 years ago with paired untreated areas that were dominated by shrubs and matched by geomorphology, soils, and elevation. To examine mechanisms underlying responses to restoration, we tested whether the abundance of a grassland specialist, Aspidoscelis uniparens, depended on time since treatment, treatment area and isolation, and local habitat quality. Because lizards use rodent burrows as habitat, we tested whether community structure and A. uniparens abundance depended on the abundance of the keystone rodent, Dipodomys spectabilis. Treated areas had reduced shrub cover and increased grass cover compared to untreated areas. Lizard community composition differed strongly between areas, with four species responding to treatments. Divergence in community composition between treated–untreated pairs was greatest for old treatments (≥22 years), and community composition was influenced by D. spectabilis. In particular, the abundance of A. uniparens was greatest on old treatments with a high density of D. spectabilis. Overall, our results demonstrate lizard community structure responds to grassland restoration efforts, and keystone species can shape restoration outcomes. Reestablishment of keystone species may be a critical constraint on the recovery of animal biodiversity after habitat restoration.     

Effect of three mound-building ant species on the formation of soil seed bank in mountain grassland

The effect of three ant species (Lasius flavus, Formica spp., Tetramorium caespitum) on soil seed bank formation was studied in temperate mountain grassland. Seed removal experiments, analysis of soil seed content and seed survival experiments were carried out to evaluate the influence of ground ants on the seed fate. In the seed removal experiment seeds of 16 species, including 5 species with elaiosome-bearing seeds (myrmecochores), were exposed and their removal followed for 39 h. On average, ants removed 63.8% of myrmecochorous seeds and 10.9% of seeds without adaptation to ant dispersal. Analysis of soil seed content revealed that myrmecochores, in spite of expectations that they would accumulate in nests of seed dispersing ants, were most abundant in the soil of control plots. Evidence on seed relocation to the ant nests was obtained from a comparison of mounds of seed dispersing and seed non-dispersing ant species, as more seeds were found in the mounds of Formica spp. and Tetramorium caespitum (seed dispersers) in comparison with the mounds of Lasius favus (non-disperser).The soil seed bank of the compared microhabitats (control plots and mounds of 3 ant species) differed in their species composition, seed abundance and vertical distribution. The most distinct qualitative differences were between seed flora of control plots and mounds of Tetramorium caespitum. Control plots had approximately 30,000 propagules per m², which was double the number of seeds found in the ant mounds. In control plots, abundance and diversity of seeds steeply declined with depth; this trend was not observed in the mounds probably due to bioturbation. In the seed survival experiment, more seeds (2 out of 3 species) survived in control plots, which may also contribute to the higher seed abundance in this microhabitat.This study showed that seed relocation by ants does not contribute significantly to seed bank build-up at this study site. Ants may, however, increase the regeneration success of myrmecochores, mainly by dispersal for distance and placement in a larger spectrum of microsites, in contrast to species not adapted for myrmecochory.     

Effects of bannertail kangaroo rat mounds on small-scale plant community structure

The effects of bannertail kangaroo rat (Dipodomys spectabilis) mounds and associated soil-surface disturbance on plant species composition and diversity in the Chihuahuan Desert were examined with multivariate analysis. Kangaroo rat mounds created disturbance gaps and contributed to local species diversity by creating microhabitats that supported unique plant communities. These microhabitats supported populations of species that were relatively rare in surrounding areas. The diversity observed at the whole habitat level resulted from (1) local spatial heterogeneity, because the mounds offered microenvironments with distinctive nutrient, water, and light conditions; and (2) local patterning of disturbance, because the digging and traffic of the kangaroo rats maintained high levels of soil disturbance at and near the mounds. At a finer scale, species diversity was highest in the area immediately adjacent to active and inactive mounds, and was lower on both the highly disturbed soil of the mounds and in the relatively undisturbed area between mounds. Lowest species diversity occurred on inactive mounds. Annual plant biomass was much greater on mounds than in inter-mound areas. The results support the predictions that intermediate levels of disturbance and small-scale environmental heterogeneity contribute to supporting high species diversity.     

Microhabitat characteristics of Akodon montensis,a reservoir for hantavirus,and hantaviral seroprevalence in an Atlantic forest site in eastern Paraguay

Hantaviruses may cause serious disease when transmitted to humans by their rodent hosts. Since their emergence in the Americas in 1993, there have been extensive efforts to understand the role of environmental factors on the presence of these viruses in their host rodent populations. HPS outbreaks have been linked to precipitation, but climatic factors alone have not been sufficient to predict the spatial‐temporal dynamics of the environment‐reservoir‐virus system. Using a series of mark‐recapture sampling sites located at the Mbaracayú Biosphere Reserve, an Atlantic Forest site in eastern Paraguay, we investigated the hypothesis that microhabitat might also influence the prevalence of Jaborá hantavirus within populations of its reservoir species, Akodon montensis. Seven trapping sessions were conducted during 2005‐2006 at four sites chosen to capture variable microhabitat conditions within the study site. Analysis of microhabitat preferences showed that A. montensis preferred areas with little forest overstory and denser vegetation cover on and near the ground. Moreover, there was a significant difference in the microhabitat occupied by antibody‐positive vs antibody‐negative rodents, indicating that microhabitats with greater overstory cover may promote transmission and maintenance of hantavirus in A. montensis.     

不同生境和季节社鼠与大林姬鼠的微生境选择比较

微生境选择分化是生境相似的物种间共存的重要原因。社鼠和大林姬鼠为北京东灵山地区常见鼠种,生境需求、活动节律及食物组成等相似,但二者共存的原因尚不清楚。2016—2017年,我们对北京东灵山地区社鼠和大林姬鼠的微生境选择进行了研究。不同季节和生境类型中,社鼠和大林姬鼠微生境选择存在明显分化。灌丛生境中,春季社鼠偏好于乔木密度、草本盖度更高和落叶盖度相对偏低的微生境,而大林姬鼠选择郁闭度、落叶盖度较高而草本盖度较低的微生境;主成分分析表明,地表覆盖物是影响二者微生境选择的主要因素;秋季社鼠喜好乔木种类多、灌木密度和草本盖度更高的微生境,而大林姬鼠选择乔木胸径、灌木距离、落叶盖度和空地比例更高的微生境,食物丰富度是影响社鼠和大林姬鼠微生境选择的主要因素。弃耕地生境中,春季社鼠倾向于灌木密度和草本盖度较高的微生境,而大林姬鼠首选郁闭度、乔木胸径、落叶盖度较大而草本盖度较低的微生境,地表覆盖物是影响二者微生境选择的主要因素;秋季社鼠偏好郁闭度和落叶盖度都相对较低的微生境,大林姬鼠则相反,食物多度是影响二者微生境选择的主要因素。次生林生境中,春季因样本量太少,未作分析;秋季社鼠优先选择灌木密度、灌木基径和草本盖度更高的微生境,大林姬鼠更倾向乔木胸径、落叶盖度较高,而灌木密度、草本盖度较低的微生境,地表覆盖物是影响二者微生境选择的主要因素。结果表明,不同生境和季节,两种鼠的微生境选择具有明显分化,这可能是二者共存的重要原因之一。