The maintenance of intraspecific biodiversity: the interplay of selection on resource use and on natural enemy resistance in the pea aphid

Biodiversity has both intraspecific and interspecific components, and speciation is the process through which the former is converted to the latter. Ecological factors can cause population divergence and differentiation. In this paper, we investigate the interplay between top-down effects from natural enemies and bottom-up effects from host plants in an aphid model system. Pea aphids, Acyrthosiphon pisum, are known to form host-adapted races on Trifolium and Medicago. Here, replicate clones of pea aphids collected from a broader set of five host plant genera are screened for their performance on the same set of host plants and also for their resistance to four natural enemies: the parasitoids Aphidius eadyi and Aphidius ervi, and the entomopathogenic fungi Pandora (=Erynia) neoaphidis and Zoophthora phalloides. The populations showed clear adaptation to their host plant from which they were collected, but they also performed well on Vicia. Performance on the other three plant species was poor. The aphid population collected from Lotus was significantly better at defending itself against the parasitoid A. eadyi, and there was a tendency for the clones from Trifolium to be resistant to the pathogen P. neoaphidis. These patterns highlight the importance of understanding the ecological processes influencing speciation in the context of the web of ecological adaptations within which a species is embedded.     

Prevalences of fungal pathogens and othernatural enemies of cereal aphids (Homoptera:Aphididae) in wheat under dryland and irrigatedconditions in South Africa

Surveys were conducted in the summer andwinter rainfall wheat producing regions of SouthAfrica in a first attempt to investigate theidentity and impact of entomopathogenic fungi withinthe cereal aphid complex. Wheat produced underdryland and irrigated conditions was surveyed duringthe 1996 and 1997 seasons. Six cereal aphid specieswere recorded of which the Russian wheat aphid, Diuraphis noxia, was the most abundantunder dryland conditions in the summer rainfallregion as opposed to the oat aphid, Rhopalosiphum padi, in the winter rainfallregion. Rose grain aphid, Metopolophiumdirhodum, was most prevalent underirrigated conditions in the summer rainfall region.Five species of entomopathogenic fungi were recordedincluding four entomophthorales and the hyphomycete,Beauveria bassiana. TheEntomophthorales included Pandora neoaphidis, Conidiobolus obscurus, C.thromboides, and Entomophthoraplanchoniana. Pandora neoaphidis wasthe most important etiological agent recorded fromD. noxia, with up to 50% mycosis recordedunder dryland conditions in the Bethlehem summerrainfall region. Similarly, P. neoaphidis wasthe most prevalent species within populations ofM. dirhodum. under irrigated conditions in theBergville/Winterton summer rainfall region (up to77% mycosis). However, mycoses of R. padi didnot exceed 1.7% in samples from these areas,suggesting that R. padi may be lesssusceptible to P. neoaphidis than M.dirhodum. Epizootics in populations of D.noxia under dryland conditions in both the winterand summer rainfall regions indicated a high levelof susceptibility to P. neoaphidis.Occurrences of hymenopterous parasitoids andpredators in populations of D. noxia were low,although a parasitism level of 25% was recorded inone small sample of R. padi collected from anirrigated field in the summer rainfall region.     

The partial characterisation of endoproteases and exoproteases from three species of entomopathogenic entomophthorales and two species of deuteromycetes

The entomopathogenic entomophthoraceae (zygomycotina) Erynia rhizospora, Erynia dipterigena, and Erynia neoaphidis and the deuteromycete Aspergillus flavus produced single novel endoproteases (pI ca. 9) with activity against trypsin and chymotrypsin substrates. In contrast, the deuteromycete Paecilomyces farinosus produced a chymotrypsin (pI ca. 10).Inhibitor studies confirmed that the mixed activities (purified by isoelectric focusing) were derived from single endoproteases. The most potent inhibitor was Chicken ovoinhibitor. Little or no inhibition was observed for P. farinosus endoprotease by any of the chemicals tested.Although the different fungi possessed a broad spectrum of aminopeptidase activity, 3 species (E. rhizospora, E. dipterigena, and A. flavus) showed a preference for leucine at the N-terminal position and 2 species (E. neoaphidis and P. farinosus) showed maximal activity against arginine. Inhibitor studies confirmed these aminopeptidases as metallo-enzymes.     

Extracellular chitinase production by some members of the saprophytic Entomophthorales group

Thirteen strains were isolated from different habitats, belonging to two genera, namely Conidiobolus and Basidiobolus, related to saprophytic Entomophthorales. Chitin flake colonization and agar-well diffusion tests were used to screen potential extracellular chitinase-producing strains in plate assays. Preliminary screening resulted in five chitinase producers that were further studied quantitatively. Results indicated that studied isolates of this group produced chitinase at different levels in chitin-containing as well as non-chitin-containing medium. Conidiobolus coronatus was found to be the most significant chitinase producer, giving 0.261 U/ml using colloidal chitin as a carbon source, among the isolates under study. This communication also reports the chitinolytic activity of Basidiobolus haptoporus, the effect of environmental and nutritional parameters on chitinase production, and utilization of fungal biomass as a carbon source, which hitherto had not been elaborated from this genus.     

Toxic Pseudo-nitzschia multistriata (Bacillariophyceae) from the Gulf of Naples: morphology,toxin analysis and phylogenetic relationships with other Pseudo-nitzschia species

The genus Pseudo-nitzschia includes several species capable of producing domoic acid, the causative agent of Amnesic Shellfish Poisoning. Some of these species have been recorded frequently in the Gulf of Naples. For one of the species, P. multistriata, which has been recurrently found in our sampling area since 1995, this is the first report for European waters. Here we provide further details on the fine structure of this species. Pseudo-nitzschia multistriata was the only one found to produce domoic acid among all the Pseudo-nitzschia species from the Gulf of Naples, and this finding raises the number of potentially toxic species in this genus to nine. Phylogenetic relationships among several Pseudo-nitzschia species were assessed using the hypervariable domains (D1–D3) of the large subunit (LSU) rDNA. The match between the phylogeny obtained and important taxonomic characters used in this genus are discussed. Results show that P. multistriata clusters with wider species lacking a central larger interspace in the raphe. Close genetic relationships were determined between P. fraudulenta and P. subfraudulenta, and between P. pungens and P. multiseries. Genetic differences among these pairs of species are comparable to those among isolates of P. pseudodelicatissima from the Gulf of Naples, indicating high intraspecific genetic diversity of Pseudo-nitzschia species in the relatively conserved LSU region. This could explain the problematic results obtained when testing a match between species-specific Pseudo-nitzschia LSU probes and our sequences.     

Resistance to a fungal pathogen and host plant specialization in the pea aphid

Herbivores that show host race formation on different plant species have proven to be valuable model systems for studying the evolution of specialization and speciation. Here, we use the pea aphid, Acyrthosiphon pisum, to investigate a possible link between specialization on two host plant species, Lotus uliginosus and Trifolium pratense, and resistance to a natural enemy, the fungal pathogen Erynia neoaphidis. Pea aphids collected on either plant species in the field showed in most cases poor survival on the alternate host plant. Furthermore, pea aphids specialized on T. pratense were very resistant to E. neoaphidis, whereas aphids specialized on L. uliginosus were susceptible. This susceptibility was not influenced by the actual food plant on which the assays were conducted. We discuss how selection from natural enemies may influence the process of specialization and race formation, and how specialization can affect the evolution of resistance.     

A PCR-based tool for the cultivation-independent monitoring of Pandora neoaphidis

Pandora neoaphidis is one of the most important fungal pathogens of aphids and has a great potential for use in biocontrol. Little is known on how this fungus persists in an area and in particular on its overwintering strategies. It is hypothesized that natural areas play an important role for survival and that soil may serve as a source of inoculum for new aphid populations in spring. To test these hypotheses, a cultivation-independent PCR-based diagnostic tool was developed, that allows the detection of P. neoaphidis in the environment. Two P. neoaphidis specific PCR primer pairs were designed, targeting sequences in the ribosomal RNA gene cluster. Specificity of both primer pairs was demonstrated with P. neoaphidis and non-target close entomophthoralean relatives. Moreover, single amplicons of expected sizes were obtained with both primer pairs from various environmental sample types, including aphid cadavers, plant material, and soil. The PCR-based diagnostic tool was applied to investigate the persistence of P. neoaphidis in soil samples obtained in 2004/2005 from a nettle field harboring infected aphids in fall 2004. P. neoaphidis was detected in every sample collected in November 2004 and March 2005, suggesting an overwintering stage of P. neoaphidis in top soil layers. The developed cultivation-independent PCR-based tool will be valuable for further investigation of the ecology of P. neoaphidis and for the development and future implementation of management strategies against aphids involving conservation biocontrol.     

ANATOMICALLY PRESERVED SEED CONES OF THE PINACEAE FROM THE EARLY CRETACEOUS OF VIRGINIA

A collection of anatomically preserved conifer cones from the Early Cretaceous of Virginia contains two new species of the extinct pinaceous genus Pityostrobus. Superficially, the fossil cones resemble those of modern species of Picea. However, the fossils reveal such a peculiar mixture of anatomical features that they cannot be assigned to any extant genus of the Pinaceae. One of the new species, Pityostrobus hueberi, is most comparable with Pityostrobus corneti Alvin from the Early Cretaceous of Belgium. Pityostrobus virginiana, the other new species, differs from all other members of the genus in only slight—but nonetheless significant—attributes. Pityostrobus hueberi and P. virginiana are the first species of this genus to be reported from Early Cretaceous sediments of the North American Atlantic Coastal Plain. As such, they increase our knowledge of the structural variation exhibited by ancient members of the Pinaceae.     

Phycodrys valentinae sp. nov. (Delesseriaceae, Rhodophyta) with Discussion of Other Species of the Phycodrys Genus from the North Pacific

A new species Phycodrys valentinae Seliv. et Zhigad. from the northwest of the Bering Sea, distinct from other species of the genus Phycodrys by the presence of a distromatic lamina and by the arrangement of basal generative prolifications, was described. Based on the analysis of the morphological and anatomic traits of species of the genus Phycodrys, P. serratiloba (Rupr.) A. Zin., which was considered as synonym of P. riggii Gardn. to the present [27, 28, 30], was reinstated as an independent species. The taxonomic status of other representatives of the genus Phycodrys of the studied region is considered. In our opinion, five species of the genus Phycodrys (P. serratiloba, P. riggii, P. amchitkensis, P. vinogradovae, and P. valentinae) grow in the seas of the Russian Far East.     

Novel morphological and genetic tools to discriminate species among the family Plumatellidae (Phylactolaemata,Bryozoa)

Some species of the freshwater bryozoans (Bryozoa, Phylactolaemata) belonging to the genus Plumatella are remarkably difficult to identify because of the large similarity of superficial architecture of their statoblasts. The examination of statoblasts by scanning electron microscope (SEM) has in fact resolved only some taxonomic questions. In this article, the authors report on novel morphological and molecular traits to discriminate among ten species of Plumatellidae (P. viganoi, P. repens, P. geimermassardi, P. rugosa, P. reticulata, P. casmiana, P. fungosa, P. emarginata, P. vaihiriae, and Hyalinella punctata). The former traits are based on shape, number, and position of annular chamber pores, whereas the latter reside on amplification and sequence analysis of the Internal Transcribed Spacer (ITS) region of nuclear rDNA. The successful amplification of ITS region from statoblasts and zooidial tubules allowed us to sequence this region on all the species investigated. The ITS sequences showed the presence of sufficient and informative polymorphisms to discriminate among morphologically similar species. It is noteworthy that the resulting ITS phylogenetic tree largely corroborated the distinction of at least two groups of freshwater bryozoans inferred on the basis of the annular chamber pore morphology. This study provides innovative approaches to reliably characterize freshwater bryozoans species and gain more insight into their taxonomy, phylogenetic relationship, and biodiversity.     

中国东部暖温带地区土壤中的皮司霉属（丝孢纲）真菌

报道从中国东部暖温带地区诸省（市）土壤中分离到的皮司霉属 Pithomyces 真菌的两个新种：长棒孢皮司霉 Pithomyces longiclavisporus和淡色皮司霉Pithomyces pallidus,及两个中国新记录种：卡罗皮司霉 Pithomyces karoo和帕夫皮司霉Pithomyces pavgii;对另外三个已知种亦作了分离地点和生境的引证。研究过的标本（干制培养物）与活菌种保存在山东农业大学植物病理学标本室（HSAUP）。     

Biodegradation of γ-hexachlorocyclohexane (Lindane) by a non-white rot fungus conidiobolus 03-1-56 isolated from litter

Biodegradation of chlorinated pesticide γ-hexachlorocyclohexane (lindane) by a nonwhite rot fungus Conidiobolus 03-1-56 is reported for the first time. Conidiobolus 03-1-56, a phycomyceteous fungus isolated from litter, completely degraded lindane on the 5th day of incubation in the culture medium, and GC-ECD studies confirmed that lindane removal did not occur via adsorption on the fungal biomass. Degradation studies using different medium compositions showed that nitrogen/carbon limiting conditions (stress conditions) and presence of veratryl alcohol, induced the secretion of extracellular oxidative enzymes, which enhanced the rate of lindance biodegradation. Under optimum nutrient-limiting conditions, GC-ECD and GC-MS analysis showed complete absence of any degradation metabolite, indicating that lindane was completely mineralized. Assays for tannic acid utilization and lignin peroxidase showed similar enzymatic profiles between Conidiobolus 03-1-56 and standard white rot fungi Pleurotus ostreatus 1200 and Trametes versicolor 1086. Although Conidiobolus 03-1-56 showed a reduced enzyme activity compared to white rot fungi, preliminary evidence indicates that enzymes responsible for lignin degradation by white rots play a key role in lindane degradation by Conidiobolus 03-1-56.     

A new diatom (Bacillariophyceae) genus with two new species from New Mexico,USA

A new diatom (Bacillariophyceae) genus and two new species are described from the arid region of the North American southwest. The new genus, Playaensis, and new species, P. circumfimbria and P. furtiva, are distinguished by frustule morphology and autecology. Playaensis possesses unique, narrowly lunate longitudinal ribs bordering the raphe and spathulate spines, but their evolutionary relationship to known genera is unclear. In Payton Lake, New Mexico, P. circumfimbria and P. furtiva are rare in the diatom community, and their geographic and geological extent are not known, but they may be restricted to alkaline, slightly saline lakes of the region.     

A new species of petalosporus

Summary A new species ofPetalosporus, P. anodosus, is described and illustrated. Two isolates representing this species were isolated from dung in California. The new species differs from the only other species of the genus,P. nodulosus, by the lack of thick-walled peridial hyphae with enlargements at the septa and by the absence of disarticulation of peridial elements. Peridial hyphae inP. anodosus have walls which are somewhat thickened and the cells are often variable in diameter. Conglomerate ascospores usually assume the petaloid arrangement characteristic of the genus.     

A new species and new records of lithodid crabs (Crustacea: Decapoda: Lithodidae) from the Crozet and Kerguelen Islands area (Subantarctica)

Four species of lithodid crabs from waters (240–2,005 m) in the Crozet and Kerguelen Islands area were studied. One new species, Neolithodes duhameli, is described. Three other species, N. capensis Stebbing, Paralomis anamerae Macpherson and P. birsteini Macpherson are reported for the first time from these localities. The new species, N. duhameli (620–1,500 m), is the fourth representative of the genus in Subantarctic waters and belongs to the group of species possessing a carapace, chelipeds and walking legs covered with numerous spinules or spiniform granules in addition to spines. However, the new species is distinguishable from others in the genus by the long, strong spines on the carapace and pereiopods. The finding of two species of Paralomis clearly extends their geographic ranges in the Southern Ocean: P. anamerae was previously known only in waters of the Falkland Islands and the circumpolar distribution of P. birsteini is supported. The observation of N. capensis also extends its previously described range from South Africa, in the Cape region, to Subantarctic waters. As a result of this study, 14 species of the family Lithodidae are now known from Antarctic and Subantarctic waters; and most can be considered endemic to these waters.     

Conservation biological control with the fungal pathogen Pandora neoaphidis: implications of aphid species, host plant and predator foraging

Abstract 1 Pandora neoaphidis is an important aphid‐specific fungal pathogen in temperate agroecosystems. Laboratory studies were carried out to obtain baseline data on factors that may affect its performance in conservation biological control. 2 Virulence of P. neoaphidis was assessed in dose–response bioassays against Microlophium carnosum on nettle, Uroleucon jaceae on knapweed, Acyrthosiphon pisum on bean and bird's‐foot trefoil Lotus corniculatus, and Metopolophium dirhodum on barley and Yorkshire fog Holcus lanatus. The most susceptible aphid was A. pisum feeding on bean with an LD₅₀ of 19 conidia per mm², whereas U. jaceae had an LD₅₀ of 104 conidia per mm² and was least susceptible to infection. 3 The presence of foraging adult ladybirds, Coccinella septempunctata, increased transmission of P. neoaphidis from infected cadavers to apterae of M. carnosum, U. jacea, and A. pisum by 7–30% at the largest cadaver density tested. Adult coccinellids that had previously foraged on nettle, knapweed, bean or bird's‐foot trefoil transfered conidia to A. pisum on bean and induced infections in 2–13% of aphids. 4 Conidia of P. neoaphidis dispersed passively in the airstream from sporulating M. carnosum cadavers on nettle plants and initiated infections in A. pisum colonies feeding on bean (4–33%) or M. dirhodum on barley (3%) located within 1.0 m of the nettle source. 5 The results suggest that M. carnosum and A. pisum may be more useful as reservoirs for P. neoaphidis in noncrop and crop areas than U. jaceae or M. dirhodum, and infection and dispersal between habitats could be enhanced in the presence of coccinellids.     

Two new species of <Emphasis Type="Italic">Conidiobolus</Emphasis> occurring in Anhui,China

Two new species of Conidiobolus were isolated from Anhui Province, China. A polyphasic taxonomic approach comprising morphological characteristics and molecular data (the nuclear large subunit of ribosomal DNA and the translation elongation factor 1 alpha gene sequences) was applied to determine their novel taxonomic status in the genus Conidiobolus. The new species C. mirabilis is a sister group to C. thromoides, but morphologically differs by smaller primary conidia and a unique formation of zygospores among two to four adjacent hyphal segments. The other new species C. pachyzygosporus characterized with thick-walled zygospores is phylogenetically closely related to C. antarcticus, C. couchii, and C. osmodes.     

Detecting Invasions of Marine Organisms: Kamptozoan Case Histories

Detecting marine invasions can be challenging, especially for lesser-known taxa, and requires (a) thorough field surveys of the region of interest for members of the taxon, (b) systematic analyses to identify all species found, (c) literature searches for the worldwide distribution of these species and for previous records of the taxon in this region, and (d) application of rigorous criteria to assess whether each species found is native or introduced. We carried out these steps in order to detect and document kamptozoan (entoproct) invasions on the American mid-Atlantic coast. We report on the occurrence of two colonial kamptozoans (Barentsia benedeni, Loxosomatoides laevis) in Chesapeake Bay (Maryland and Virginia, USA). On the American Atlantic coast, B. benedeni had previously only been reported from Massachusetts, although this species has a worldwide distribution in bays and harbors. The genus Loxosomatoides had not previously been reported from North America and L. laevis was known only from India. Since the genus Loxosomatoides was very poorly characterized, we briefly review all four of its species, which differ only slightly from each other. We have also synonymized L. japonicum with L. laevis. We did not find any of the kamptozoan species previously recorded in surveys of Chesapeake Bay and the American Atlantic coast. This is the first detailed consideration of anthropogenic influences on kamptozoan distributions, and we emphasize that most kamptozoan species are cryptogenic pending further investigation.