Interactive effects of keystone rodents on the structure of desert grassland arthropod communities

Certain species play particularly large roles in ecosystems, and are often referred to as keystones. However, little is known about the interactive effects of these species where they co-occur. Prairie dogs ( Cynomys spp.) and banner-tailed kangaroo rats Dipodomys spectabilis are commonly considered keystone species of grassland ecosystems, creating a mosaic of unique habitats on the landscape through ecosystem engineering and herbivory. We examined the separate and interactive effects of these species on the structure of grassland arthropod communities. We conducted a cross-site study at two locations in the northern Chihuahuan Desert, and evaluated the impacts of these rodents on ground-dwelling arthropod and grasshopper communities in areas where prairie dogs and kangaroo rats co-occurred compared to areas where each rodent species occurred alone. Our results demonstrate that prairie dogs ( C. gunnisoni and C. ludovicianus ) and banner-tailed kangaroo rats had keystone-level impacts on arthropod communities both separately and interactively. Their burrow systems provided important habitats for multiple trophic and taxonomic groups of arthropods, and increased overall arthropod abundance and species richness. Many arthropods also were attracted to the aboveground habitats around the mounds and across the landscapes where the rodents occurred. Detritivores, predators, ants, grasshoppers, and rare rodent burrow inhabitants were especially associated with prairie dog and kangaroo rat activity. The impacts of prairie dogs and kangaroo rats were unique, and the habitats they created supported different assemblages of arthropods. Where both rodent species co-occurred, there was greater heterogeneity and arthropod diversity on the landscape. Our results suggest that the interaction of multiple keystones, especially those with engineering roles, results in unique and more diverse communities in time and space.     

Mite and insect zonation on a Marion Island rocky shore: a quantitative approach

This study provides the first quantitative analysis of the littoral and supralittoral insect and mite assemblages of sub-Antarctic Marion Island. Seventeen mite species (126,203 individuals) from 11 families were found on the shore at Macaroni Bay. Three families dominated the assemblages in both abundance and diversity: the Hyadesiidae, Ameronothridae and Halacaridae. Six insect species from three orders were found on the shore. Species richness increased from one in the littoral, to four and two species in the Mastodia and Caloplaca zones, respectively. The littoral chironomid midge Telmatogeton amphibius was the most abundant insect species, constituting 80% of all insects counted. Arthropod assemblages corresponded closely to the cryptogam-dominated zonation patterns previously identified for the Marion Island shore. This clear association between arthropod and cryptogam zonation patterns provided a clear indication of habitat specificity in many of the species, and a quantitative analysis of habitat specificity on a species by species basis supported this idea. The specificity of most species to the shore, which forms part of the epilithic biotope, is most likely a consequence of the considerable age of this biotope compared to the younger, post-glacial vascular vegetation. Tourist species, i.e. species transient to an assemblage, inflated species richness in zones and the distribution ranges of species across zones. It is suggested that previous qualitative analyses of shoreline arthropod communities may have overestimated species ranges and richnesses because of the inclusion of tourist species. It is suggested that if a sound understanding of patterns in, and processes underlying Antarctic arthropod assemblages is to be achieved, quantitative analyses must be expanded in the region. Accepted: 14 May 2000     

Tree hybridization and genotypic variation drive cryptic speciation of a specialist mite herbivore

Few studies have investigated the roles that plant hybridization and individual plant genotype play in promoting population divergence within arthropod species. Using nrDNA sequence information and reciprocal transfer experiments, we examined how tree cross type (i.e., pure Populus angustifolia and P. angustifolia x P. fremontii F(1) type hybrids) and individual tree genotype influence host race formation in the bud-galling mite Aceria parapopuli. Three main findings emerged: (1) Strong genetic differentiation of mite populations found on pure P. angustifolia and F(1) type hybrids indicates that these mites represent morphologically cryptic species. (2) Within the F(1) type hybrids, population genetic analyses indicate migration among individual trees; however, (3) transfer experiments show that the mites found on heavily infested F(1) type trees perform best on their natal host genotype, suggesting that genetic interactions between mites and their host trees drive population structure, local adaptation, and host race formation. These findings argue that hybridization and genotypic differences in foundation tree species may drive herbivore population structure, and have evolutionary consequences for dependent arthropod species.     

Further studies of Dirofilaria roemeri (Nematoda: Filarioidea) in naturally and experimentally infected Macropodidae.

Larval development of D. roemeri occurs in the subcutaneous and intermuscular connective tissue and intramuscularly in the pelvic region and hind limbs of the wallaroo and eastern grey kangaroo. Host response to developing larvae is not evident at 1, 14 and 28 days. The development of D. roemeri in the red kangaroo exhibits features previously observed in both normal and abnormal hosts. Low-level blood microfilaraemia of brief duration occurs in the red kangaroo, which may act as a secondary reservoir of infection for other kangaroo and wallaby species. Among commercially harvested Macropodidae in Queensland there is a greater prevalence of D. roemeri in wallaroos and grey kangaroos than in red kangaroos. Infection is most prevalent in animals from south-central and south-western districts.     

Epifaunistic arthropod parasites of the four-striped mouse, Rhabdomys pumilio, in the Western Cape Province, South Africa

Flea, lice, mite, and tick species associated with 510 Rhabdomys pumilio were collected at 9 localities in the Western Cape Province, South Africa. The aims of the study were first to quantify the species richness, prevalence, and relative mean intensity of infestation of epifaunistic arthropod species associated with R. pumilio, and second to determine temporal variations in the mean abundance of the parasitic arthropods. Each mouse was examined under a stereoscopic microscope and its parasites were removed, identified, and quantified. The epifaunal population was made up of more than 25,000 individuals and included 8 flea, 1 sucking louse, 11 mite, and 13 ixodid tick species. Female-biased sex ratios were noted for 9 (30%) of the ectoparasite species. Three undescribed mite and 1 undescribed tick species were recovered, and new locality records for 2 flea, the louse, and 2 mite species were documented. A phoretic host association between a nonparasitic mite species, Psylloglyphus uilenbergi kivuensis, and 3 flea species, Chiastopsylla rossi, Hypsophthalmus temporis, and Listropsylla agrippinae, was recorded. The mean abundance of the parasitic mite and insect species were higher during the cold wet season, whereas ticks were more numerous during the warm dry months. The large number of ectoparasite species on R. pumilio, a locally abundant and regionally widespread species, is of medical and veterinary importance particularly in relation to the transmission of pathogens such as Anaplasma marginale, Babesia caballi, and Babesia canis to domestic animals; Rickettsia conori; Yersinia pestis; and the viral disease Crimean-Congo hemorrhagic fever to humans.     

Distribution of the bacterial symbiont Cardinium in arthropods

Abstract 'Candidatus Cardinium', a recently described bacterium from the Bacteroidetes group, is involved in diverse reproduction alterations of its arthropod hosts, including cytoplasmic incompatibility, parthenogenesis and feminization. To estimate the incidence rate of Cardinium and explore the limits of its host range, 99 insect and mite species were screened, using primers designed to amplify a portion of Cardinium 16S ribosomal DNA (rDNA). These arthropods were also screened for the presence of the better-known reproductive manipulator, Wolbachia. Six per cent of the species screened tested positive for Cardinium, compared with 24% positive for Wolbachia. Of the 85 insects screened, Cardinium was found in four parasitic wasp species and one armoured scale insect. Of the 14 mite species examined, one predatory mite was found to carry the symbiont. A phylogenetic analysis of all known Cardinium 16S rDNA sequences shows that distantly related arthropods can harbour closely related symbionts, a pattern typical of horizontal transmission. However, closely related Cardinium were found to cluster among closely related hosts, suggesting host specialization and horizontal transmission among closely related hosts. Finally, the primers used revealed the presence of a second lineage of Bacteroidetes symbionts, not related to Cardinium, in two insect species. This second symbiont lineage is closely allied with other arthropod symbionts, such as Blattabacterium, the primary symbionts of cockroaches, and male-killing symbionts of ladybird beetles. The combined data suggest the presence of a diverse assemblage of arthropod-associated Bacteroidetes bacteria that are likely to strongly influence their hosts' biology.     

Geographical structuring of feather mite assemblages from the Australian brush-turkey (Aves: Megapodiidae)

Populations of a host species may exhibit different assemblages of parasites and other symbionts. The loss of certain species of symbionts (lineage sorting, or "missing-the-boat") is a mechanism by which geographical variation in symbiont assemblages can arise. We studied feather mites and lice from Australian brush-turkeys (Aves: Megapodiidae: Alectura lathami) and expected to observe geographical structuring in arthropod assemblages for several reasons. First, because the brush-turkey is a sedentary ground-dwelling bird, we predicted that geographically close host populations should share more similar arthropod assemblages than distant ones. Second, because brush-turkeys do not brood their young, vertical transfer of arthropods is unlikely, and brush-turkeys probably acquire their mites and lice at social maturity through contact with other birds. Young birds could disperse and found new populations without carrying complete sets of symbionts. We predicted that young birds would have fewer species of arthropods than older birds; in addition, we expected that males (which are polygynous) would have more species than females. Birds were sampled from 12 sites (=populations) along the east coast of Queensland, Australia, that were separated by a distance of 12.5-2,005 km. In total, 5 species of mites from the Pterolichidae and 1 species from the Ascouracaridae were found. Two species of lice were collected but in numbers too low to be statistically useful. Differentiation of mite assemblages was evident; in particular, Leipobius sp. showed 100% prevalence in 3 host populations and 0% in the remaining 9. A dendrogram of brush-turkey populations based on mite assemblages showed 2 geographically correlated clusters of sites, plus 1 cluster that contained 2 sites near Brisbane and 1 approximately at a distance of 1,000 km. There was no strong effect of host age or sex on number of mite species carried. Horizontal transfer of feather mites by hippoboscid flies, in addition to physical contact between hosts, may play a role in homogenizing symbiont assemblages within populations.     

Abundances and host relationships of chigger mites in Yunnan Province,China

This paper reports on ectoparasitic chigger mites found on small mammals in Yunnan Province, southwest China. Data were accumulated from 19 investigation sites (counties) between 2001 and 2009. A total of 10 222 small mammal hosts were captured and identified; these represented 62 species, 34 genera and 11 families in five orders. From the body surfaces of these 10 222 hosts, a total of 92 990 chigger mites were collected and identified microscopically. These represented 224 species, 22 genera and three subfamilies in the family Trombiculidae (Trombidiformes). Small mammals were commonly found to be infested by chigger mites and most host species harboured several species of mite. The species diversity of chigger mites in Yunnan was much higher than diversities reported previously in other provinces of China and in other countries. A single species of rodent, Eothenomys miletus (Rodentia: Cricetidae), carried 111 species of chigger mite, thus demonstrating the highest species diversity and heaviest mite infestation of all recorded hosts. This diversity is exceptional compared with that of other ectoparasites. Of the total 224 mite species, 21 species accounted for 82.2% of all mites counted. Two species acting as major vectors for scrub typhus (tsutsugamushi disease), Leptotrombidium scutellare and Leptotrombidium deliense, were identified as the dominant mite species in this sample. In addition to these two major vectors, 12 potential or suspected vector species were found. Most species of chigger mite had a wide range of hosts and low host specificity. For example, L. scutellare parasitized 30 species of host. The low host specificity of chigger mites may increase their probability of encountering humans, as well as their transmission of scrub typhus among different hosts. Hierarchical clustering analysis showed that similarities between different chigger mite communities on the 18 main species of small mammal host did not accord with the taxonomic affinity of the hosts. This suggests that the distribution of chigger mites may be strongly influenced by the environment in which hosts live.     

Cardinium symbionts cause cytoplasmic incompatibility in spider mites

Intracellular symbiotic bacteria belonging to the Cytophaga-Flavobacterium-Bacteroides lineage have recently been described and are widely distributed in arthropod species. The newly discovered bacteria, named Cardinium sp, cause the expression of various reproductive alterations in their arthropod hosts, including cytoplasmic incompatibility (CI), induction of parthenogenesis and feminization of genetic males. We detected 16S ribosomal DNA sequences similar to those of Cardinium from seven populations of five spider mite species, suggesting a broad distribution of infection of Cardinium in spider mites. To clarify the effect of Cardinium on the reproductive traits of the infected spider mites, infected mites were crossed with uninfected mites for each population. In one of the populations, Eotetranychus suginamensis, CI was induced when infected males were crossed with uninfected females. The other six populations of four species showed no reproductive abnormalities in the F(1) generation, but the possibility of CI effects in the F(2) generation remains to be tested. One species of spider mite, Tetranychus pueraricola, harbored both Cardinium and Wolbachia, but these symbionts seemed to have no effect on the reproduction of the host, even when the host was infected independently with each symbiont.     

Contrasting diversity dynamics of phoretic mites and beetles associated with vertebrate carrion

Carrion is an ephemeral and nutrient-rich resource that attracts a diverse array of arthropods as it decomposes. Carrion-associated mites often disperse between animal carcasses using phoresy, the transport of one species by another. Yet few studies have contrasted the dynamics of mite assemblages with other insect taxa present at carrion. We examined and compared the changes in abundance, species richness and composition of mite and beetle assemblages sampled at kangaroo carcasses in a grassy eucalypt woodland at four different times over a 6-month period. We found that the majority of mites were phoretic, with the mesostigmatid genera Uroseius (Uropodidae), Macrocheles (Macrochelidae) and Parasitus (Parasitidae) the most abundant taxa (excluding astigmatid mites). Abundance and richness patterns of mites and beetles were very different, with mites reaching peak abundance and richness at weeks 6 and 12, and beetles at weeks 1 and 6. Both mites and beetles showed clear successional patterns via changes in species presence and relative abundance. Our study shows that mesostigmatid mite assemblages have a delay in peak abundance and richness relative to beetle assemblages. This suggests that differences in dispersal and reproductive traits of arthropods may contribute to the contrasting diversity dynamics of carrion arthropod communities, and further highlights the role of carrion as a driver of diversity and heterogeneity in ecosystems.     

Mechanisms for the keystone status of kangaroo rats: graminivory rather than granivory?

Graminivory by kangaroo rats (Dipodomys spp.) was investigated as a potential mechanism for the keystone role of these rodents in the dynamics of desert grasslands. Experiments confirmed that Ord's kangaroo rats (Dipodomys ordii) cut and consumed a large proportion of the tillers of three Chihuahuan Desert tussock-forming grass species. Field observations indicated that the characteristically cut grass tillers were absent from all-rodent and medium-sized kangaroo rat exclosures, but were frequent in large-sized kangaroo rat and rabbit exclosures, indicating that the medium-sized kangaroo rats (D. ordii, D. merriami) were responsible for grass cutting. Tiller waste as a percentage of peak standing crop ranged from 7% in grassland habitats to 0.7% in Flourensia cernua shrubland. Of the 13 species of perennial, tussock-forming grasses measured, only one, Muhlenbergia porteri, had no tillers cut by kangaroo rats. This study demonstrates that the keystone role of kangaroo rats in Chihuahuan Desert grassland ecosystems is probably the result of their graminivory. Received: 28 October 1996 / Accepted: 26 February 1997     

Mites associated with stored grain commodities in Benin, West Africa

After insects, mites are the major arthropod pests that inhabit stored agricultural products worldwide. To determine the acarofauna that infests cowpea, maize, paddy rice and sorghum in Benin (West Africa), surveys were conducted in some principal markets (Dantokpa, Glazoue and Parakou) of this country. A total of 555 samples of grains and debris were collected in May and September 2011. More than 56 species belonging to 24 mite families were recorded in the four products. These mite species included predators, parasites, fungivorous, phytophagous and other groups whose feeding habits are not well known. The family Cheyletidae was the most prevalent and the most diverse predatory mite family encountered, in which Cheyletus malaccensis Oudemans was the most abundant species. Several families of mite pests and mites responsible for allergies (Acaridae, Glycyphagidae, Pyroglyphidae, Pyemotidae and Saproglyphidae) were also detected. The three most dominant and frequent species were C. malaccensis, Suidasia nesbitti (Hughes) and Suidasia sp. Statistical analysis showed that densities of these three mite species were higher in Parakou than in Glazoue and Dantokpa, on one hand, and higher in debris than in grains, on the other hand. The densities of S. nesbitti and Suidasia sp. decreased significantly during the dry season, whereas C. malaccensis remained stable throughout the two samplings. Of all grains, sorghum was the least infested with mites. This study shows that in Benin mites are present in stored agricultural products to which they cause serious damage, and may cause various allergies to people.     

Parasitic and phoretic arthropods of sylvatic and commensal white-footed mice (Peromyscus leucopus) in central Tennessee, with notes on Lyme disease

Sixteen species of parasitic or phoretic arthropods were collected from 56 white-footed mice, Peromyscus leucopus, live-trapped in central Tennessee from April through November 1987. Arthropod infestation was compared for mice taken from sylvatic (woodland) versus commensal (household) habitats. Three species were recorded from hosts in both habitats: the sucking louse Hoplopleura hesperomydis, the flea Epitedia wenmanni, and the laelapid mite Androlaelaps casalis. Twelve of the 13 remaining arthropod species were taken only from mice trapped in woodland whereas the phoretic glycyphagid mite Glycyphagus hypudaei was collected only from commensal mice. Arthropod faunas on commensal hosts clearly were impoverished. The 12 additional arthropod species recorded from the woodland mice consisted of 1 nidicolous beetle, Leptinus orientamericanus; 1 bot, Cuterebra fontinella; 3 fleas, Ctenophthalmus pseudagyrtes, Orchopeas leucopus and Peromyscopsylla scotti; 1 tick, Dermacentor variabilis; 2 mesostigmatid mites, Androlaelaps fahrenholzi and Ornithonyssus bacoti; 3 chiggers, Comatacarus americanus, Euschoengastia peromysci, and Leptotrombidium peromysci; and 1 undescribed pygmephorid mite of the genus Pygmephorus. Two nymphal and 100 larval D. variabilis were examined for spirochetes and found to be uninfected.     

Seasonal occurrence of key arthropod pests and associated natural enemies in Alabama Satsuma citrus

Six Alabama Satsuma mandarin orchards (four conventionally sprayed and two unsprayed) were surveyed during 2005 and 2006 to determine the population dynamics of arthropod pests and their natural enemies. Twenty-eight arthropod pest species were encountered; the major foliage pests were citrus whitefly, Dialeurodes citri (Ashmead); purple scale, Lepidosaphes beckii (Newman); Glover scale, L. gloveri (Packard); and citrus red mite, Panonychus citri (McGregor). Two distinct population peaks were recorded for citrus whitefly at most locations. The most important direct sources of citrus whitefly mortality were parasitism by Encarsia lahorensis (Howard) and infection by the pathogenic fungus, Aschersonia aleyrodis Webber. In general, all stages of both scale insects (purple scale and Glover scale) were present in the orchards year-round, indicative of overlapping generations; however, the highest densities were recorded during the early season. Citrus whitefly, purple scale, and Glover scale were more abundant on leaves collected from the interior of the tree canopy than in the exterior canopy. Citrus red mite densities were highest in the spring, with populations declining at the start of the summer, and were more abundant in the exterior canopy than in the interior canopy. The most important natural enemies of citrus red mite were predatory mites belonging to several families, of which Typhlodromalus peregrinus Muma (Phytoseiidae) was the predominant species. Major differences were recorded in the relative abundance of different arthropod pest species in the orchards: citrus whitefly, purple scale, and Glover scale predominated in the unsprayed orchards, whereas citrus red mite infestations were more severe in the sprayed orchards. The results are discussed in relation to the possible effect of orchard management practices on abundance of the major pests.     

Unexpected bird–feather mite associations revealed by DNA metabarcoding uncovers a dynamic ecoevolutionary scenario

The high relevance of host‐switching for the diversification of highly host‐specific symbionts (i.e., those commonly inhabiting a single host species) demands a better understanding of host‐switching dynamics at an ecological scale. Here, we used DNA metabarcoding to study feather mites on passerine birds in Spain, sequencing mtDNA (COI) for 25,540 individual mites (representing 64 species) from 1,130 birds (representing 71 species). Surprisingly, 1,228 (4.8%) mites from 84 (7.4%) birds were found on host species that were not the expected to be a host according to a recent bird–feather mite associations catalog. Unexpected associations were widespread across studied mite (40.6%) and bird (43.7%) species and showed smaller average infrapopulation sizes than typical associations. Unexpected mite species colonized hosts being distantly related to the set of their usual hosts, but with similar body size. The network of bird–mite associations was modular (i.e., some groups of bird and mite species tended to be more associated with each other than with the others), with 75.9% of the unexpected associations appearing within the module of the typical hosts of the mite species. Lastly, 68.4% of mite species found on unexpected hosts showed signatures of genetic differentiation, and we found evidence for reproduction or the potential for it in many of the unexpected associations. Results show host colonization as a common phenomenon even for these putatively highly host‐specific symbionts. Thus, host‐switching by feather mites, rather than a rare phenomenon, appears as a relatively frequent phenomenon shaped by ecological filters such as host morphology and is revealed as a fundamental component for a dynamic coevolutionary and codiversification scenario.     

Incidence of a new sex-ratio-distorting endosymbiotic bacterium among arthropods

Many intracellular micro-organisms are now known to cause reproductive abnormalities and other phenomena in their hosts. The endosymbiont Wolbachia is the best known of these reproductive manipulators owing to its extremely high incidence among arthropods and the diverse host effects it has been implicated as causing. However, recent evidence suggests that another intracellular bacterium, a Cytophaga-like organism (CLO), may also induce several reproductive effects in its hosts. Here, we present the first survey of arthropod hosts for infection by the CLO. We use a sensitive hemi-nested polymerase chain reaction method to screen 223 species from 20 arthropod orders for infection by the CLO and Wolbachia. The results indicate that, although not as prevalent as Wolbachia, the CLO infects a significant number of arthropod hosts (ca. 7.2%). In addition, double infections of the CLO and Wolbachia were found in individuals of seven arthropod species. Sequencing analysis of the 16S rDNA region of the CLO indicates evidence for horizontal transmission of the CLO strains. We discuss these results with reference to future studies on host effects induced by intracellular micro-organisms.     

Diversity and phylogenetic relationships of Wolbachia in Drosophila and other native Hawaiian insects

Wolbachia is a genus of parasitic alphaproteobacteria found in arthropods and nematodes, and represents on of the most common, widespread endosymbionts known. Wolbachia affects a variety of reproductive functions in its host (e.g., male killing, cytoplasmic incompatibility, parthenogenesis), which have the potential to dramatically impact host evolution and species formation. Here, we present the first broad-scale study to screen natural populations of native Hawaiian insects for Wolbachia, focusing on the endemic Diptera. Results indicate that Wolbachia infects native Hawaiian taxa, with alleles spanning phylogenetic supergroups, A and B. The overall frequency of Wolbachia incidene in Hawaiian insects was 14%. The incidence of infection in native Hawaiian Diptera was 11% for individuals and 12% for all species screened. Wolbachia was not detected in two large, widespread Hawaiian dipteran families—Dolichopodidae (44 spp screened) and Limoniidae (12 spp screened). Incidence of infection within endemic Hawaiian lineages that carry Wolbachia was 18% in Drosophilidae species, 25% in Caliphoridae species, > 90% in Nesophrosyne species, 20% in Drosophila dasycnemia and 100% in Nesophrosyne craterigena. Twenty unique alleles were recovered in this study, of which 18 are newly recorded. Screening of endemic populations of D. dasycnemia across Hawaii Island revealed 4 unique alleles. Phylogenetic relationships and allele diversity provide evidence for horizontal transfer of Wolbachia among Hawaiian arthropod lineages.     

Diversity and phylogenetic relationships of Wolbachia in Drosophila and other native Hawaiian insects

Wolbachia is a genus of parasitic alphaproteobacteria found in arthropods and nematodes, and represents on of the most common, widespread endosymbionts known. Wolbachia affects a variety of reproductive functions in its host (e.g., male killing, cytoplasmic incompatibility, parthenogenesis), which have the potential to dramatically impact host evolution and species formation. Here, we present the first broad-scale study to screen natural populations of native Hawaiian insects for Wolbachia, focusing on the endemic Diptera. Results indicate that Wolbachia infects native Hawaiian taxa, with alleles spanning phylogenetic supergroups, A and B. The overall frequency of Wolbachia incidene in Hawaiian insects was 14%. The incidence of infection in native Hawaiian Diptera was 11% for individuals and 12% for all species screened. Wolbachia was not detected in two large, widespread Hawaiian dipteran families—Dolichopodidae (44 spp screened) and Limoniidae (12 spp screened). Incidence of infection within endemic Hawaiian lineages that carry Wolbachia was 18% in Drosophilidae species, 25% in Caliphoridae species, > 90% in Nesophrosyne species, 20% in Drosophila dasycnemia and 100% in Nesophrosyne craterigena. Twenty unique alleles were recovered in this study, of which 18 are newly recorded. Screening of endemic populations of D. dasycnemia across Hawaii Island revealed 4 unique alleles. Phylogenetic relationships and allele diversity provide evidence for horizontal transfer of Wolbachia among Hawaiian arthropod lineages.     

猕猴桃园节肢动物群落重建及主要类群的生态位

为研究猕猴桃节肢动物群落重建过程和主要类群生态位移,本试验系统调查野生猕猴桃和人工栽植不同树龄(3年、9年、14年)猕猴桃园节肢动物群落,测定群落特征指标和主要类群的时空生态位。结果表明,群落包含3纲15目74科,约90种。不同桃园节肢动物群落的主要类群不同,各类群占群落总数的比例差异显著,野生猕猴桃园群落中各类群分布较均匀,栽植桃园群落中害虫比例较大。野生猕猴桃园和栽植猕猴桃园之间,群落的多样性指数、均匀度和优势度差异均极显著,群落稳定性表现为野生>9年>14年>3年。各类群的时空二维生态位也会随着栽植时间增长发生变化：蜘蛛和蝇类的生态位在不同树龄的猕猴桃园中都保持在较高水平;人工栽植初期,山楂叶螨和叶蝉占据的时空生态位较宽,成为优势类群,小薪甲与山楂叶螨生态位重叠较大,竞争激烈;随后,小薪甲和瘿蚊的时空二维生态位逐渐增大,到14年桃园中已经取代了山楂叶螨和叶蝉,成为主要害虫。总之,人工干扰的节肢动物群落重建是一个次级演替过程,与自然生态系统群落明显不同。     

Three new species of Eimeria from Bolivian marsupials

Faecal samples collected from 300 Bolivian marsupials (Didelphimorphia: Didelphidae) between 1984 and 1993 were examined for coccidian parasites. Sporulated oocysts were present in the faeces of 50 (17%) marsupials representing 11 genera and 22 species. Three new species of Eimeria are described and named from six host species. One species occurred in Marmosops dorothea, Monodelphis domestica and Thylamys venustus, another in Micoureus constantiae constantiae and Micoureus constantiae budini and a third in Marmosops dorothea. A discriminant analysis performed on five quantitative oocyst measurements revealed similarities between the first and third Eimeria species because of similar sizes and shapes of the oocysts, whereas the second Eimeria species was structurally discrete. The Eimeria that infects multiple hosts may be a common widespread species. Future surveys are advised for a thorough assessment of the coccidian biodiversity within Bolivian marsupials.