Flea Assemblages Research Articles

Nestedness and β-diversity in ectoparasite assemblages of small mammalian hosts: effects of parasite affinity, host biology and scale

We asked whether (a) variation in species composition of parasite assemblages on the same host species follows a non-random pattern and (b) if so, manifestation of this non-randomness across space and time differs among parasites, hosts and scales. We assessed nestedness and its contribution to β-diversity of fleas and gamasid mite assemblages exploiting small mammals across three scales: (a) within the same region across different locations; (b) within the same location across different times and (c) across distinct geographic regions. We estimated (a) the degree of nestedness (NCOL) and (b) the proportional contribution of nestedness to the total amount of β-diversity across locations, times and regions (βNESP). In the majority of host species, parasite assemblages were nested significantly across all three scales. In mites, but not fleas, NCOL correlated with the contribution of nestedness to the total amount of β-diversity. In fleas, NCOL did not differ among assemblages at the two local scales, but was significantly lower at regional scale. In mites, NCOL was the highest in assemblages at local spatial scale. βNESP was significantly higher (a) in flea than in mite assemblages at both local scales and (b) in mite than in flea assemblages at regional scale. In fleas, βNESP was higher at both local scales, whereas in mites it was higher at both local temporal and regional scales. Sheltering habits and geographic range of a host species did not affect either NCOL or βNESP in flea assemblages, but both metrics significantly decreased with an increase of geographic range of a host species in mite assemblages. We conclude that flea and mite assemblages across host populations at smaller and larger spatial scales and at temporal scale were characterized by nestedness which, in turn, contributed to an important degree to the total amount of β-diversity of these assemblages.

Rodent and Flea Abundance Fail to Predict a Plague Epizootic in Black-Tailed Prairie Dogs

Small rodents are purported to be enzootic hosts of Yersinia pestis and may serve as sources of infection to prairie dogs or other epizootic hosts by direct or flea-mediated transmission. Recent research has shown that small rodent species composition and small rodent flea assemblages are influenced by the presence of prairie dogs, with higher relative abundance of both small rodents and fleas at prairie dog colony sites compared to grasslands without prairie dogs. However, it is unclear if increased rodent or flea abundance predisposes prairie dogs to infection with Y. pestis. We tracked rodent and flea occurrence for 3 years at a number of prairie dog colony sites in Boulder County, Colorado, before, during, and after a local plague epizootic to see if high rodent or flea abundance was associated with plague-affected colonies when compared to colonies that escaped infection. We found no difference in preepizootic rodent abundance or flea prevalence or abundance between plague-positive and plague-negative colonies. Further, we saw no significant before-plague/after-plague change in these metrics at either plague-positive or plague-negative sites. We did, however, find that small rodent species assemblages changed in the year following prairie dog die-offs at plague-affected colonies when compared to unaffected colonies. In light of previous research from this system that has shown that landscape features and proximity to recently plagued colonies are significant predictors of plague occurrence in prairie dogs, we suggest that landscape context is more important to local plague occurrence than are characteristics of rodent or flea species assemblages.

Are local plague endemicity and ecological characteristics of vectors and reservoirs related? A case study in north-east Tanzania

Abstract The pattern of plague endemicity in Tanzania is characterized by continuous re-appearance of the disease in some locations, while in other neighbouring villages the disease has never or seldom been observed. To understand the reasons for this pattern, we studied small mammal and flea species composition, diversity and relative abundances in two plague-endemic and two plague-free locations. We asked (a) whether fleas more abundant in plague-endemic locations differ in their characteristic abundance and the degree of their host specificity from fleas more abundant in plague-free locations and (b) whether hosts most abundant in plague- endemic locations differ in the diversity of their flea assemblages from hosts most abundant in plague-free locations. We characterized (a) each host species by species richness and degree of taxonomic relatedness of its flea assemblages and (b) each flea species by its mean abundance and size, and degree of taxonomic relatedness of its host spectrum and compared their relative abundances between locations. No significant difference between plague- endemic and plague-free locations in either host density or any variable related to flea abundance or diversity was found. However, there was marginally significant effect of taxonomic distinctness of a flea assemblage harboured by a host on its probability to be more abundant in either plague-endemic or plague-free locations. Furthermore, hosts more abundant in plague-endemic locations tended to harbour closely-related fleas. Finally. while opportunistic and specialist fleas were equally distributed in both sets of locations, fleas exploiting distantly-related hosts were found mainly in plague-free locations during the rainy season. We suggest that the observed patterns might arise due to seasonal and spatial differences in local microclimatic conditions and landscape connectivity.

Seasonal and habitat dependence of fleas parasitic on small mammals in Tanzania

We investigated host and flea species composition across different habitats during dry and rainy seasons in the Western Usambara Mountains in Tanzania. During both seasons, similarity in flea species composition increased with an increase in the similarity in host species composition. Nevertheless, between-season within-habitat as well as within-season between-habitat similarity in host species composition was higher than similarity in flea species composition. Ordination of habitats according to their host and flea species composition demonstrated that the pattern of between-habitat similarity in both host and flea species composition varied seasonally. Despite the relatively rich mammal and flea fauna of the study region, the major contribution to variation in species composition between seasons and among habitats was due to a few species only. Flea assemblages on Lophuromys kilonzoi Verheyen et al., 2007 and Praomys delectorum Thomas, 1910 in different habitats were equally similar in either season. In contrast, flea assemblages on Mastomys natalensis (Smith, 1834) occurring in different habitats were more similar in the dry than in the rainy season, whereas the opposite was the case for fleas on Grammomys sp. In different hosts, the main differences in species composition of flea assemblages between seasons as well as among habitats were due to different flea species. Although our results support the earlier idea that parasite species composition is determined by both host species composition and habitat properties, the former appears to explain variance in flea species composition between localities in the tropics better than between localities in temperate and arid zones.

Geographic patterns of diversification: an example with ectoparasitic insects

On any spatial scale, the species composition of a taxonomic group often departs from a phylogenetically random subset drawn from the pool of species available on a higher scale. Analysis of the uneven representation of related lineages in different assemblages can reveal the action of various forces shaping their diversification. For any assemblage, unequal diversification among lineages can be estimated using diversity skewness, an index of the balance of a phylogenetic tree whose values increase with increasing differences in diversification rates among tree branches. We tested for geographical patterns in the diversity skewness of flea assemblages parasitic on small mammals in 26 distinct geographic localities from the Palaearctic and 15 from the Nearctic. Overall, diversity skewness of the Nearctic flea assemblage was unexpectedly high compared to that of the global flea fauna, whereas that of the Palaearctic did not depart from the expectations of a null model. On a smaller scale, the diversity skewness of local flea assemblages was sometimes lower, sometimes higher, but, in most of the 41 localities, it did not differ significantly from that of random subsets taken from the species pool available on the larger spatial scale (either the world fauna or that of the biogeographical realm, i.e. Palaearctic or Nearctic). More importantly, among Palaearctic assemblages, diversity skewness increased with increasing latitude and/or decreasing mean air temperatures. The different patterns observed in the Palaearctic and Nearctic may be in part due the fact that flea diversification appears to have been more intense in the former than the latter, and to differences between them in relief and glacial history. Temperature-driven speciation rates may well explain the latitudinal gradient in diversity skewness in the Palaearctic. The results illustrate the action of various biogeographical processes in shaping the uneven differentiation of flea lineages on different spatial scales. © 2008 The Linnean Society of London, Biological Journal of the Linnean Society, 2008, 95, 807–814.

Fleas parasitizing domestic dogs in Spain

In addition to their importance to veterinary clinical practice as ectoparasites, fleas of domestic dogs are of special concern because they can be vectors of disease, including zoonoses. Flea assemblages parasitizing domestic dogs usually comprise several flea species whose distribution is determined by factors acting at several scales. Knowledge of these factors will aid in assessment of the distribution patterns of flea parasitism, and is an important tool in developing control strategies and in evaluation of flea-borne disease risk in dogs and humans. In this survey we used data from 744 domestic dogs from 79 localities in Spain to explore the associations between the abundance of flea species, host-dependent factors (sex and age), and host habitat factors including abode (farm, house with garden, apartment), location (urban or rural), the presence of other pets, and dog activity (measured as the frequency with which dogs left their abode). We also considered environmental factors including the time of year and mean annual temperature and rainfall. Variations in flea community structure at infracommunity and component community levels were also explored. Four flea species were found parasitizing dogs. Ctenocephalides felis was the most abundant (88.02% of fleas identified), followed by Ctenocephalides canis (10.38%), Pulex irritans (1.47%) and Echidnophaga gallinacea (0.13%). Overall flea abundance was higher on dogs living on farms than in apartments, as was the abundance of Ct. felis, Ct. canis and P. irritans. Ct. felis was more abundant on dogs living in houses than in apartments, but the reverse was found for P. irritans. Overall flea abundance and Ct. canis abundance were highest in rural areas, whereas the presence of other pets sharing the abode was associated with higher overall flea abundance and Ct. felis abundance. Only P. irritans abundance was positively related to the activity of dogs. Ct. canis and P. irritans abundances were higher during the warm period of the year. Mean annual temperature was negatively correlated with overall, Ct. canis and P. irritans abundances, but positively related to Ct. felis abundance. Annual rainfall was negatively correlated with Ct. canis and P. irritans abundances. Variations in the number of flea species found on a dog reflected the abundance distribution patterns for each species and their associations with host habitat and environmental factors. At the component community level, flea species richness was inversely related to annual mean temperature. The structure of flea assemblages on dogs was mainly associated with host habitat and environmental variables, and not with host-dependent variables. However, a large amount of variation in flea abundance remained unexplained, suggesting the effect of other non-controlled factors.

Are ectoparasite communities structured? Species co‐occurrence, temporal variation and null models

1. We studied temporal variation in the structure of flea communities on small mammalian hosts from eastern Slovakia using null models. We asked (a) whether flea co-occurrences in infracommunities (in the individual hosts) in different hosts as well as in the component communities (in the host species) demonstrate a non-random pattern; (b) whether this pattern is indicative of either positive or negative flea species interactions; (c) whether this pattern varies temporally; and (d) whether the expression of this pattern is related to population size of either fleas or hosts or both. 2. We constructed a presence/absence matrix of flea species for each temporal sample of a host species and calculated four metrics of co-occurrence, namely the C-score, the number of checkerboard species pairs, the number of species combinations and the variance ratio (V-ratio). Then we compared these metrics with the respective indices calculated for 5000 null matrices that were assembled randomly using two algorithms, namely fixed-fixed (FF) and fixed-equiprobable (FE). 3. Most co-occurrence metrics calculated for real data did not differ significantly from the metrics calculated for simulated matrices using the FF algorithm. However, the indices observed for 42 of 75 presence/absence matrices differed significantly from the null expectations for the FE models. Non-randomness was detected mainly by the C-score and V-ratio metrics. In all cases, the direction of non-randomness was the same, namely the aggregation, not competition, of flea species in host individuals and host species. 4. The inclusion or exclusion of the uninfested hosts in the FE models did not affect the results for individual host species. However, exclusion of the uninfested host species led to the acceptance of the null hypothesis for only six of 13 temporal samples of the component flea communities for which non-randomness was detected when the uninfested hosts were included in the analysis. 5. In most host species, the absolute values of the standardized size effect of both the C-score and V-ratio increased with an increase in host density and a concomitant decrease in flea abundance and prevalence. 6. Results of this study demonstrated that (a) flea assemblages on small mammalian hosts were structured at some times, whereas they appeared to be randomly assembled at other times; (b) whenever non-randomness of flea co-occurrences was detected, it suggested aggregation but never segregation of flea species in host individuals or populations; and (c) the expression of structure in flea assemblages depended on the level of density of both fleas and hosts.

Temporal dynamics of a T-cell mediated immune response in desert rodents

Immunocompetence, the general capacity of an individual host to mount an immune response against pathogens, is commonly assessed by the response to a challenge of the immune system by injection of phytohaemagglutinin (PHA). The response to PHA is commonly considered a reliable estimate of the T-cell mediated immune response. We investigated the temporal pattern of the PHA response in 10 rodent species from the Negev desert, Israel. We hypothesized that the temporal dynamics of the PHA response would differ among species with different natural patterns of flea parasitism. We injected PHA subcutaneously in the footpad of each rodent and measured its PHA response 6, 24 and 48 h after injection. Rodent species showed two types of PHA response. One type was rapid and characteristic of rodents that had either species-poor flea assemblages, or that are rarely attacked by fleas. This response peaked approximately 6 h after PHA injection. The second type of response was delayed and was typical of rodents that have either species-rich flea assemblages or high abundance and prevalence of fleas or both. Their response to PHA peaked 24 h after injection. Furthermore, rodents that responded promptly had a lower maximum response than rodents with a delayed response. Our results suggest the occurrence of a trade-off between intensity and latency of the PHA response and, therefore, the necessity to account for the relationship between maximum PHA response and time after injection when making interspecific comparisons of immunocompetence.

Habitat variation in species composition of flea assemblages on small mammals in central Europe

AbstractWe studied patterns of variation in species composition of flea assemblages on small mammals across different habitats of Slovakia and compared flea species composition within and across host species among habitats. We asked (1) how variable the composition of flea assemblages is among different populations of the same host occurring in different habitats and (2) whether the composition of flea assemblages in a habitat is affected either by species composition of hosts or by environmental affinities of this habitat. Between‐habitat similarity in flea species composition increased with an increase in the similarity in host species composition. Species richness of flea assemblages of a host species correlated positively with mean number of cohabitating host species but not with the number of habitats occupied by a host species. Results of the ordination of flea collections from each individual host demonstrated that the first five principal components explained most of the variance in species composition of flea assemblages. The segregation between rodent and insectivore flea assemblages was easily discerned from the ordination diagram when flea assemblages were plotted according to their hosts. When flea assemblages were plotted according to their habitat affinities, the distinction of habitats based on variation in flea composition was not as clear. The results of ANOVA of each principal component showed the significant effect of both host species and habitat type. The variation in each principal component was explained better by the factor of host species compared with the factor of habitat type. Multidimensional scaling of flea assemblages within host species across habitats demonstrated that among‐habitat variation in flea composition was manifested differently in different hosts.

Aggregation and species coexistence in fleas parasitic on small mammals

The aggregation model of coexistence states that species coexistence is facilitated if interspecific aggregation is reduced relative to intraspecific aggregation. We investigated the relationship between intraspecific and interspecific aggregation in 17 component communities (the flea assemblage of a host population) of fleas parasitic on small mammals and hypothesized that interspecific interactions should be reduced relative to intraspecific interactions, facilitating species coexistence. We predicted that the reduction of the level of interspecific aggregation in relation to the level of intraspecific aggregation would be positively correlated with total flea abundance and species richness of flea assemblages. We also expected that the higher degree of facilitation of flea coexistence would be affected by host parameters such as body mass, basal metabolic rate (BMR) and depth and complexity of burrows. Results of this study supported the aggregation model of coexistence and demonstrated that, in general, a) conspecific fleas were aggregated across their hosts; b) flea assemblages were not dominated by negative interspecific interactions; and c) the level of interspecific aggregation in flea assemblages was reduced in relation to the level of intraspecific aggregation. Intraspecific aggregation tended to be correlated positively to body mass, burrow complexity and mass‐independent BMR of a host. Positive interspecific associations of fleas tended to occur more frequently in species‐rich flea assemblages and/or in larger hosts possessing deep complex burrows. Intraspecific aggregation increased relative to interspecific aggregation when species richness of flea infracommunities (the flea assemblage of a host individual) and component communities increased. We conclude that the pattern of flea coexistence is related both to the structure of flea communities and affinities of host species.

Nested pattern in flea assemblages across the host's geographic range

Understanding non‐random patterns in the taxonomic composition of communities occurring in insular or fragmented habitats remains a major goal of ecology. Nested subset patterns are one possible departure from random community assembly that has been reported for communities of both free‐living and parasitic animals. Here, we investigate the effects of extrinsic factors on the occurrence of nestedness among the assemblages of fleas found in different populations of the same host species, using data on 25 mammalian host species. The patterns of flea species composition among host populations spanned the entire spectrum from significantly nested to significantly anti‐nested. After controlling for host phylogeny, we found that across host species, the tendency for flea assemblages to approach nestedness increased with increasing host geographic range size and with decreasing latitude of the host's geographic range. This tendency also decreased with an increase in a composite variable combining data on mean January and July temperature. The number of closely‐related mammalian species living in sympatry with a given host species had no influence on whether or not the structure of flea assemblages among its populations departed from randomness. We propose explanations for these results that include: the possible gradual loss of flea species as a host expands its range from its initial area of origin, the lack of specific flea faunas in narrowly‐distributed host species, interspecific differences in the dispersal abilities of flea species becoming amplified in hosts with broad geographical ranges, and the effect of latitude, climate and environment on the probabilities of host‐switching and extinction in fleas. Overall, our results suggest that the structure of flea assemblages in mammalian hosts may be driven by features of host biology.

Abundance patterns and coexistence processes in communities of fleas parasitic on small mammals

The abundance of a given species in a community is likely to depend on both the total abundance and diversity of other species making up that community. A large number of co‐occurring individuals or co‐occurring species may decrease the abundance of any given species via diffuse competition; however, indirect interactions among many co‐occurring species can have positive effects on a focal species. The existence of diffuse competition and facilitation remain difficult to demonstrate in natural communities. Here, we use data on communities of fleas ectoparasitic on small mammals from 27 distinct geographical regions to test whether the abundance of any given flea species in a community is affected by either the total abundance of all other co‐occurring flea species, or the species richness and/or taxonomic diversity of the flea community. At all scales of analysis, i.e. whether we compared the same flea species on different host species, or different flea species, two consistent results emerged. First, the abundance of a given flea species correlates positively with the total abundance of all other co‐occurring flea species in the community. Second, the abundance of any given flea species correlates negatively with either the species richness or taxonomic diversity of the flea community. The results do not support the existence of diffuse competition in these assemblages, because the more individuals of other flea species are present on a host population, the more individuals of the focal species are there as well. Instead, we propose explanations involving either apparent facilitation among flea species via suppression of host immune defenses, or niche filtering processes acting to restrict the taxonomic composition and abundance of flea assemblages.

Spatial variation in species diversity and composition of flea assemblages in small mammalian hosts: geographical distance or faunal similarity?

AbstractAim Spatial variation in the diversity of fleas parasitic on small mammals was examined to answer three questions. (1) Is the diversity of flea assemblages repeatable among populations of the same host species? (2) Does similarity in the composition of flea assemblages among populations of the same host species decay with geographical distance, with decreasing similarity in the composition of local host faunas, or with both? (3) Does the diversity of flea assemblages correlate with climatic variables?Location The study used previously published data on 69 species of small mammals and their fleas from 24 different regions of the Holarctic.Methods The diversity of flea assemblages was measured as both species richness and the average taxonomic distinctness of their component species. Similarity between flea assemblages was measured using both the Jaccard and Morisita–Horn indices, whereas similarity in the composition of host faunas between regions (host ‘faunal’ distance) was quantified using the Jaccard index. Where appropriate, a correction was made for the potentially confounding influence of phylogeny using the independent contrasts method.Results Flea species richness varied less within than among host species, and is thus a repeatable host species character; the same was not true of the taxonomic distinctness of flea assemblages. In almost all host species found in at least five regions, similarity in flea assemblages decreased with increases in either or both geographical and faunal distance. In most host species, the diversity of flea assemblages correlated with one or more climatic variable, in particular mean winter temperature.Main conclusions Spatial variation in flea diversity among populations of the same mammal species is constrained by the fact that it appears to be a species character, but is also driven by local climatic conditions. The results highlight how ecological processes interact with co‐evolutionary history to determine local parasite biodiversity.

Diversification of ectoparasite assemblages and climate: an example with fleas parasitic on small mammals

ABSTRACTAim We studied the relationships between the numbers of species and numbers of higher taxa (genera, tribes, subfamilies and families) in flea assemblages of small mammalian hosts with the aims of: (a) comparing these relationships across different regions, and (b) testing the hypothesis that flea assemblages in warmer regions diversify mainly via intrahost speciation, whereas those in colder regions diversify mainly via host switching.Location The study used previously published data on flea assemblages on small mammalian hosts from 25 different regions of the Holarctic.Methods The number of flea genera, tribes, subfamilies or families in an assemblage (host species) was plotted against the number of flea species in this assemblage for each region separately, and a power function was fitted to the resulting relationships. Then, the values of the exponent of the power function for a region were regressed against the mean annual temperature in this region, across all regions.Results The relationships between the number of flea species and the numbers of flea genera, tribes, subfamilies or families on a host species in each region were found to be well described by simple power functions. The exponent of the power function of the relationship between the number of flea species and the number of flea genera per host tended to decrease with increasing local mean annual temperature. When two apparent outliers from the trend (corresponding to regions where sampling was not performed as in other regions) were omitted from the analysis, the negative relationship between temperature and the exponent of the power function between the number of flea species and number of flea genera per host became highly significant. No relationship was found between the values of the exponents of the power functions between the number of flea species and the number of flea tribes, subfamilies or families per host, and the mean local annual temperature.Main conclusions The results suggest that the diversification of flea assemblages is associated with climatic variables. In warm regions, the greater number of congeneric species per flea assemblage, reflected by the lower exponent of the power function, may well be the outcome of intrahost speciation. This indicates that, as regional temperature increases, intrahost speciation becomes a relatively more important mode of diversification than acquisition of fleas via host switching.

Flea species richness and parameters of host body, host geography and host ‘milieu’

Summary 1 We have assessed how different host parameters affect species richness of flea assemblages using the independent contrasts method. Three groups of host parameters were examined. The first group included host body parameters (body size, basal and average daily metabolic rates), the second group included parameters of geographical range size and position of this range in relation to the equator (latitude) and the third group comprised parameters related to the number of sympatric closely related species. 2 None of the host body parameters correlated with species richness of flea assemblages. 3 Flea species richness increased with an increase in latitude of the geographical range centre of a host as well as with an increase in a composite variable that described the size of the geographical range. 4 The number of sympatric closely related species both across the entire geographical range and locally was correlated positively with species richness of fleas. 5 Our results show that species richness of ectoparasites is affected little by parameters of the host body and to a greater extent by parameters related to the host environment.

Relationship between host diversity and parasite diversity: flea assemblages on small mammals

AbstractAim We examined the relationship between host species richness and parasite species richness using simultaneously collected data on small mammals (Insectivora, Rodentia and Lagomorpha) and their flea parasites.Location The study used previously published data on small mammals and their fleas from 37 different regions. All the world's main geographical regions other than Australasia and Wallacea were represented in the study, i.e. neotropical, nearctic, palaearctic, oriental and afrotropical realms.Methods We controlled the data for the area sampled and sampling effort and then tested this relationship using both cross‐region conventional analysis and the independent contrasts method (to control for the effects of biogeographic historical relationships among different regions). Brooks parsimony analysis was used to construct a region cladogram based on the presence/absence of a host species and host phylogeny.Results Both cross‐region and independent contrasts analyses showed a positive correlation between host species richness and flea species richness. Conventional cross‐region regression under‐ or overestimated fleas species richness in the majority of regions.Main conclusions When the regression derived by the independent contrasts method was mapped onto the original tip data space, points that deviated significantly from the regression originated from Kenya, Mississippi and southern California (lower than expected flea richness) and Chile, Idaho, south‐western California and Kyrgyzstan (higher than expected flea richness). These deviations can be explained by the environmental mediation of host–flea relationships and by a degree of environmental variety in sampled areas.

Immune responses to fleas in two rodent species differing in natural prevalence of infestation and diversity of flea assemblages.

We studied in vivo immune response to fleas in two gerbils, Gerbillus dasyurus and Gerbillus andersoni allenbyi, which differed in their natural species richness of flea assemblages and prevalence of infestation. G.dasyurus is parasitized naturally by several flea species, but the prevalence of infestation is low, whereas G. a. allenbyi is parasitized by a single flea species, with high prevalence of infestation. We hypothesized that immunological parameters and the cell-mediated specific immune response to an antigen from an unfamiliar flea species differ between the two gerbil species. Parasitized and control gerbils of both species demonstrated similar, relatively low levels of spontaneous glucose consumption. The same was true for the phytohemagglutinin treatment. Responses to antigen from unfamiliar flea species were higher than both spontaneous glucose consumption and response to phytohemagglutinin in parasitized and control G. a. allenbyi and parasitized G. dasyurus. However, no significant difference in the spontaneous blast transformation index and responses to both phytohemagglutinin and flea antigen was found in control G. dasyurus. The number of white blood cells was significantly lower in control than in parasitized G. dasyurus, whereas no difference in the number of white blood cells was found between control and parasitized G. a. allenbyi. The levels of circulating immune complexes and concentrations of immunoglobulins did not differ between parasitized and control individuals in both species. Phagocytic activity was significantly higher in males than in females of G. a. allenbyi but not of G. dasyurus. In addition, phagocytes of G. dasyurus appeared to be significantly more active than those of G. a. allenbyi.

Host–habitat relations as an important determinant of spatial distribution of flea assemblages (Siphonaptera) on rodents in the Negev Desert

We studied flea assemblages on rodents in different habitats of the Ramon erosion cirque in the Negev Desert to examine whether host-habitat relations influence flea spatial distribution. Eleven flea species parasitizing 12 rodent species were recorded. There was significant positive relationship between flea species richness and body mass of the host species; no relationships were found between relative richness of flea assemblage and either the number of habitats occupied by the host species or the size of host geographical range. The differences in pattern of flea parasitism among habitat types within host species were determined by both environmental features of a habitat and the specific pattern of habitat use by rodents. There was replacement of Xenopsylla conformis by Xenopsylla ramesis on Meriones crassus and Gerbillus dasyurus among different habitats. The results of ordination of the flea collections from each individual host demonstrated that the flea assemblages were segregated mainly along 4 axes, which explained 86% of total variance. Each of the ordination axes corresponded with a change in flea species composition. The directions of these changes were (1) among-hosts within a habitat and (2) among-habitats within a host.