Pathogens of the bark beetle Ips cembrae: microsporidia and gregarines also known from other Ips species

The objective of the current study was to identify pathogens of the large larch bark beetle, Ips cembrae, which is a secondary pest that has produced several local outbreaks across Europe in recent years. Beetles were collected from pheromone traps, trap trees and emergence traps (Larix decidua) during 2007 to 2011 at 10 study sites in central Europe. A total of 3379 mature and callow beetles were examined with a light microscope, and only two microsporidian pathogens [Chytridiopsis typographi and a diplokaryotic microsporidium (probably Nosema sp.)] and two gregarines (Gregarina typographi and Mattesia schwenkei) were found. Within the I. cembrae populations, the infection rate for C. typographi ranged from 2 to 58%. Nosema sp. occurred in only two beetles in 2007 (at two study sites). G. typographi was recorded only in Austria and Croatia and only in 1–2% of the beetles in those countries. Mattesia schwenkei was observed solely in Croatia in 0.6% of the beetles in that country. Only one fungal pathogen in the genus Fusarium was found and only in two mature beetles (0.7%) in 2010. The pathogen species found during our study of I. cembrae were very similar to the pathogens previously identified for Ips typographus. No species‐specific pathogen was detected.     

The comparative prevalence and demographic impact of two pathogens in swarming Ips typographus adults: a quantitative analysis of long term trapping data

• 1 Adult Ips typographus were collected using pheromone traps at a locality in the eastern part of Austria between 1995 and 2004. The occurrence of two pathogens, Gregarina typographi and Chytridiopsis typographi, was determined throughout the period of beetle swarming activities. Weekly and annual data sets were then analysed by smoothing statistical techniques and epidemiological models.
• 2 The pathogens spread differently within the beetle population with respect to their biological characteristics: infectious forms of C. typographi were immediately available after their development in the insect's gut, but not those of G. typographi.
• 3 Both of the pathogens had a low prevalence in swarming beetles, especially C. typographi, and there was no evidence of a between‐year or within‐year epidemiological process. Conversely, it was shown that G. typographi has a positive effect on the rate of increase of trapped beetles.
• 4 Fitting a nonlinear model to the data suggested that: (i) this was due to a higher catch ability of beetles infected with G. typographi than of healthy beetles; (ii) when this effect is taken into account, G. typographi induces a specific within‐year low mortality in beetle populations; and (iii) beetle populations increase naturally within a year, despite their infection by both pathogens. No clear effect of C. typographi was detected in the trapped data set when the prevalence of this species was high in beetle populations collected from trees.
• 5 It is hypothesized that both pathogens induce different behavioural effects on their host, resulting in: (i) favouring the trapping of G. typographi‐infected beetles and (ii) hindering the capture of C. typographi‐infected individuals. This could be the result of both of the pathogens having an opposite effect on the flight abilities of beetles and/or on the beetles' response to the aggregation pheromones used in the traps.

     

Nematodes associated with Ips cembrae (Coleoptera: Curculionidae): comparison of generations,sexes and sampling methods

A study of nematodes associated with the large larch bark beetle Ips cembrae (Heer 1836) was carried out at three locations in the Czech Republic. The proportion of beetles infested by endoparasitic nematodes (representatives of genera Contortylenchus, Parasitylenchus, Cryptaphelenchus and Parasitorhabditis) ranged from 29.9 to 50.9%. Significant differences were determined in nematode infestation levels among locations, generations and sampling methods. No differences were found in infestation rates between males and females. The percentage of bark beetles with phoretic nematodes ranged from 18 to 42.9%. Phoretic nematodes directly found under elytra, on wings and between body segments of the bark beetles belong to the genus Micoletzkya. However, adults and juveniles of other two phoretic species Laimaphelenchus penardi and Bursaphelenchus sp. were found in the gallery frass of I. cembrae. Infestation by phoretic nematodes positively correlated with the presence of mites under elytra.     

Nematodes associated with the double‐spined bark beetle Ips duplicatus (Coleoptera: Curculionidae) in central Europe

Ips duplicatus (Sahlberg) is an important forest pest in central Europe, but its nematode associates have seldom been studied. Therefore, nematodes associated with I. duplicatus were determined at three localities in the Czech Republic. The percentage of beetles with phoretic nematodes ranged from 18 to 65%. Micoletzkya buetschlii and other phoretic nematodes were found under elytra, on wings, and between body segments. The percentage of beetles with nematodes in the haemocoel ranged from 3 to 30%, and the nematodes included Contortylenchus diplogaster and Parasitylenchus cf. aculeatus. Juveniles of Parasitorhabditis obtusa (Fuchs 1915) were found in the intestines of 0–16% of the beetles. The most abundant species in I. duplicatus galleries were P. obtusa and M. buetschlii. Cryptaphelenchus sp., Parasitaphelenchus sp. and unidentified tylenchid juveniles also were found in the galleries. The percentage of beetles with nematodes was greater in the overwintering than in the offspring generation, and numbers of nematodes per gallery increased with gallery development.     

Infections with the ascomycete fungus Metschnikowia typographi sp.nov. in the bark beetles Ips typographus and Ips amitinus (Coleoptera, Scolytidae)

The ascomycete fungus Metschnikowia typographi sp.nov. is described. It infects the spruce bark beetles Ips typographus L. and Ips amitinus Eichl. Masses of vegetative cells and navicular asci (I. typographus 13-17 x 2 microns; I. amitinus 17-22 x 2 microns) were found in cells of the midgut epithelium and in the body cavity of infected beetles. Each ascus contains two needle-shaped ascospores flattened in the central part, 0.5-1.5 x 0.3 x 13-15 microns and pointed at both ends. The parasitic species of Metschnikowia, M. bicuspidata, M. artemiae, M. unicuspidata, M. wickerhami and M. typographi are discussed as a special group of the genus characterized by morphological characters.     

Methane indicator values for peatlands: a comparison of species and functional groups

Previous studies have shown a correspondence between the abundance of particular plant species and methane flux. Here, we apply multivariate analyses, and weighted averaging, to assess the suitability of vegetation composition as a predictor of methane flux. We developed a functional classification of the vegetation, in terms of a number of plant traits expected to influence methane production and transport, and compared this with a purely taxonomic classification at species level and higher. We applied weighted averaging and indirect and direct ordination approaches to six sites in the United Kingdom, and found good relationships between methane flux and vegetation composition (classified both taxonomically and functionally). Plant species and functional groups also showed meaningful responses to management and experimental treatments. In addition to the United Kingdom, we applied the functional group classification across different geographical regions (Canada and the Netherlands) to assess the generality of the method. Again, the relationship appeared good at the site level, suggesting some general applicability of the functional classification. The method seems to have the potential for incorporation into large‐scale (national) greenhouse gas accounting programmes (in relation to peatland condition/management) using vegetation mapping schemes. The results presented here strongly suggest that robust predictive models can be derived using plant species data (for use in national‐scale studies). For trans‐national‐scale studies, where the taxonomic assemblage of vegetation differs widely between study sites, a functional classification of plant species data provides an appropriate basis for predictive models of methane flux.     

Emergence patterns of univoltine and bivoltine Ips typographus (L.) populations and associated natural enemies

Control measures aiming at reducing bark beetle populations and preserving their natural enemies require a sound knowledge on their overwintering and emergence behaviour. These behavioural traits were investigated in univoltine and bivoltine populations of the European spruce bark beetle (Ips typographus [L.], Coleoptera: Scolytinae) and its predators and parasitoids over several consecutive years. In univoltine populations, roughly 50% of the bark beetles left their brood trees in fall together with most parasitoids and some significant predatory flies and beetles. In bivoltine populations, <10% of the second bark beetle generation emerged in fall and the remainder overwintered under the bark of their brood trees. Likewise, most predatory beetles and flies spent wintertime with their prey under the bark, while most parasitic wasps emerged in fall. The spring emergence of bivoltine predatory beetles was found to occur up to 3 weeks earlier than that of I. typographus, while that of the predatory flies and the parasitoids was delayed by up to 1 month. In univoltine populations, the bark beetles emerged several weeks prior to most antagonistic taxa. In the heat year 2003, three I. typographus generations were produced at the lower location, 36% of the third generation emerged in fall, while the proportions of overwintering predators remained largely the same as in previous years. Similar to their host, more parasitoids left their brood trees in fall after warm years. The results show that sanitation felling during winter probably kills most bark beetles in bivoltine populations, but also eliminates many natural enemies. In univoltine populations, sanitation felling might be less detrimental to both I. typographus and natural enemies because a fair fraction of their populations will already have left the trees before cutting. Warmer climates may affect the interactions of bark beetles and natural enemies and thus the impact of control measures.     

Welcome back Janolidae and Antiopella: Improving the understanding of Janolidae and Madrellidae (Cladobranchia,Heterobranchia) with description of four new species

Proctonotidae and Madrellidae are families that belong to the suborder Cladobranchia. Historically, both have been the subjects of taxonomic confusion. Thus, Proctonotidae Gray, 1853, was subsequently named as Zephyrinidae Iredale and O'Donoghue, 1923 and Janolidae Pruvot‐Fol, 1933, but currently both are considered as synonyms of Proctonotidae. On the other hand, Alder and Hancock (1864) erected the genus Madrella in Proctonotidae. Here, we completed a detailed morphological and molecular study of four apparently undescribed species of Madrellidae and Proctonotidae from the Indo‐Pacific. We performed a maximum likelihood and Bayesian inference phylogenetic analyses using two mitochondrial and one nuclear genes to improve the understanding of the families. Prompted by our results, Janolidae is removed from synonymy with Proctonotidae. Within Janolidae, there are two well‐supported clades. One includes species with smooth cerata that are found in the Atlantic and eastern Pacific Oceans. The taxa in this clade include the type species of Antiopella and several other species. We resurrect Antiopella as the valid name for this clade. The sister clade to Antiopella includes a variety of taxa with species that have been traditionally included in Janolus Bergh, 1884 and Bonisa Gosliner, 1981. Further systematic revision requires more comprehensive taxon sampling. The new species discovered have clear morphological differences and strong molecular support. They include Madrella amphora Pola and Gosliner sp. nov. , Janolus tricellariodes Pola and Gosliner sp. nov. , Janolus flavoanulatus Pola and Gosliner sp. nov., and Janolus incrustans Pola and Gosliner sp. nov.     

The genus Pseudo-nitzschia (Bacillariophyceae) in a temperate estuary with description of two new species: Pseudo-nitzschia plurisecta sp. nov. and Pseudo-nitzschia abrensis sp. nov.

The genus Pseudo‐nitzschia contains potentially toxic species of problematic taxonomy, making it one of the most intensively studied diatom genera. The study of 35 clonal strains isolated from the Bilbao estuary, an area that experiences recurrent blooms of Pseudo‐nitzschia, revealed the presence of two new species, P. abrensis and P. plurisecta, differing from their congeners in both morphology and gene sequence. The morphological features were analyzed by LM and EM, whereas molecular analyses were based on the internal transcribed spacer (ITS) and large subunit (LSU) regions of the rDNA. P. plurisecta appears closely related to P. cuspidata/P. pseudodelicatissima in the phylogenetic tree, whereas P. abrensis forms a moderately supported clade with P. heimii/P. subpacifica and P. caciantha/P. circumpora. Comparison of the secondary structure of ITS2 regions reveals marked differences in the most highly conserved regions among related taxa. Morphologically, the new species differ from their closest congeners in the arrangement of the poroid sectors and the density of valve striae and fibulae. The two species share similar pigment composition, and belong to the group of Pseudo‐nitzschia species containing only chlorophyll c₂ and c₃.     

Postovipositional development of the sand snake Psammophis sibilans (Serpentes:Lamprophiidae) in comparison with other snake species

Characterizing and comparing developmental progress across different species helps to interpret how different or similar body forms evolved. We present an embryonic table for the oviparous African Sand Snake Psammophis sibilans from the Lamprophidae family, describing its postovipositional in ovo development. Psammophis is a good model of a genus that is widely distributed in Africa and Asia and includes 22 species. We describe ten embryonic stages based on the development of externally visible morphological characteristics such as; pharyngeal arches, facial processes, eyes, scales, body pigmentation and body colour pattern development. This study discusses the development of this snake and compares it with that of the closely related brown house snake Lamprophis fulliginosus (Lamprophidae) and the medically important venomous cobras Naja haje haje and Naja kaouthia from the sister lineage Elapidae. The distantly related basal snake Python sebae, which displays different morphology and behaviour, was chosen for deeper insight into the evolution of body structures within the snake clade. We found interspecific differences in the relative stage of development of embryonic structures at the time of oviposition and during postovipositional embryonic development. One of the outcomes of this study is that embryonic structures such as the pharyngeal processes, eye pigmentation and scales are interspecifically conservative in regard to timing of morphodifferentiation, while body pigmentation, colour and colour pattern are interspecifically plastic in their temporospatial development.     

Proposing a new hypothesis: Rickettsia spp. as a mechanism maintaining parapatry between two Australian reptile tick species

This study investigates two parasitic reptile ticks — Bothriocroton hydrosauri and Amblyomma limbatum — of the sleepy lizard (Tiliqua rugosa) that abut at a 1–2 km wide parapatric boundary in South Australia. Long‐term research has investigated potential mechanisms to explain the maintenance of this boundary but has not uncovered why the distribution of A. limbatum does not extend further south. It has been previously hypothesised that pathogens may be responsible for maintaining parapatric boundaries. Rickettsia spp. has previously been reported in B. hydrosauri ticks. This study explored whether Rickettsia spp. occurs in co‐occurring A. limbatum. We observed that Rickettsia spp. was absent from all A. limbatum ticks and that 83% of examined B. hydrosauri were found to be positive with a spotted fever group Rickettsia strain. This study puts forward the hypothesis that Rickettsia spp. could contribute to the maintenance of the Mt Mary parapatric boundary between these two tick species. Further work is required to determine whether Rickettsia spp. can be transmitted from B. hydrosauri to A. limbatum and — if transmission can occur — to explore whether Rickettsia is lethal to A. limbatum ticks.     

Phorid species from Acromyrmex’s hosts and effect on their survival of two fungi proposed for the control of leafcutter ants

Phorid flies (Diptera: Phoridae, Metopinini) are natural enemies of leafcutter ants (Hymenoptera: Formicidae, Attini), which are among the most important pests in the Neotropical region. These parasitoids lay their eggs inside worker ants, causing the death of the parasitized ants, and the oviposition attacks on foraging workers interfere with the collection of vegetal material used in fungal gardens, thereby affecting the whole colony. However, because of the large number of ants per colony, more than one type of biological control agent is needed to have a significant impact. We collected parasitized leafcutter ants Acromyrmex lundii (Guérin‐Méneville), Acromyrmex heyeri (Forel), and Acromyrmex ambiguus (Emery) from various places in Argentina and reared their parasitoids. We recorded developmental times, host and phorid sizes, and other aspects of the biology of the phorids Apocephalus neivai Borgmeier, Apocephalus noetingerorum Brown & Disney, Myrmosicarius gracilipes Borgmeier, Myrmosicarius catharinensis Borgmeier, Myrmosicarius crudelis Borgmeier, and Myrmosicarius cristobalensis Disney et al. This is the first record of A. ambiguus, an important pest of pine plantations, being a host of phorids. We found the first cases of gregarious parasitoidism of a parasitoid with no‐free pupae: M. catharinensis on A. lundii ants. We also evaluated the effect on pupal survival of two cosmopolitan fungi, Beauveria bassiana (Balsamo) Vuill. and Trichoderma lentiforme (Rehm) Chaverri et al., which are also considered as potential biological control agents of leafcutter ants. Suspensions of conidia were tested on Myrmosicarius and Apocephalus parasitoid pupae of different ages. No negative effect on pupal survival was found under either fungal treatment. Therefore, the use of both natural enemies separately but simultaneously, or the introduction of fungi‐inoculated pupae in the pest habitats, seems to be a promising strategy for the multiple biological control of leafcutter ants.     

Evaluating the capacity of plant DNA barcodes to discriminate species of cotton (Gossypium: Malvaceae)

Although two plastid regions have been adopted as the standard markers for plant DNA barcoding, their limited resolution has provoked the consideration of other gene regions, especially in taxonomically diverse genera. The genus Gossypium (cotton) includes eight diploid genome groups (A–G, and K) and five allotetraploid species which are difficult to discriminate morphologically. In this study, we tested the effectiveness of three widely used markers (matK, rbcL, and ITS2) in the discrimination of 20 diploid and five tetraploid species of cotton. Sequences were analysed locus‐wise and in combinations to determine the most effective strategy for species identification. Sequence recovery was high, ranging from 92% to 100% with mean pairwise interspecific distance highest for ITS2 (3.68%) and lowest for rbcL (0.43%). At a 0.5% threshold, the combination of matK+ITS2 produced the greatest number of species clusters. Based on ‘best match’ analysis, the combination of matK+ITS2 was best, while based on ‘all species barcodes’ analysis, ITS2 gave the highest percentage of correct species identifications (98.93%). The combination of sequences for all three markers produced the best resolved tree. The disparity index test based on matK+rbcL+ITS2 was significant (P < 0.05) for a higher number of species pairs than the individual gene sequences. Although all three barcodes separated the species with respect to their genome type, no single combination of barcodes could differentiate all the Gossypium species, and tetraploid species were particularly difficult.     

Dietary specialization and the effects of plant species on potential multitrophic interactions of three species of nymphaline caterpillars

The diet breadth of insect herbivores influences their response to variation in plant quality, and these bitrophic interactions have implications for the higher‐level trophic interactions between herbivores and their natural enemies. In this comparative study, we examined the role of host plant species and plant secondary chemistry on the potential interactions between three species of nymphaline caterpillars and their natural enemies. The caterpillar species (all Lepidoptera: Nymphalidae) varied in their degree of specialization: the buckeye, Junonia coenia Hübner, is a specialist on plants that contain iridoid glycosides (IGs); the white peacock, Anartia jatrophae L., feeds on plants in five families, some of which contain IGs and some of which do not; and the painted lady, Vanessa cardui L., is a generalist, feeding on plants in at least 15 families. Each species was reared on leaves of an introduced host plant, Plantago lanceolata L. (Plantaginaceae), which produces two IGs, aucubin and catalpol, and on another plant species that is a common host plant. These alternate host plants were Plantago major L. (Plantaginaceae) for J. coenia, Bacopa monnieri (L.) Pennell (Plantaginaceae) for A. jatrophae, and Malva parviflora L. (Malvaceae) for V. cardui. We examined growth, sequestration, and immune response of these caterpillars on the different host plant species. Junonia coenia developed more rapidly and sequestered higher IG concentrations when reared on P. lanceolata, whereas both other species grew more slowly on P. lanceolata. Host plant did not influence immune response of J. coenia or A. jatrophae, whereas V. cardui immune response was weaker when reared on P. lanceolata. Junonia coenia was most efficient at IG sequestration and A. jatrophae was least efficient, when all three species were reared on P. lanceolata. These results indicate that diet breadth may play an important role in structuring tritrophic interactions, and this role should be further explored.     

Efficient distinction of invasive aquatic plant species from non‐invasive related species using DNA barcoding

Biological invasions are regarded as threats to global biodiversity. Among invasive aliens, a number of plant species belonging to the genera Myriophyllum, Ludwigia and Cabomba, and to the Hydrocharitaceae family pose a particular ecological threat to water bodies. Therefore, one would try to prevent them from entering a country. However, many related species are commercially traded, and distinguishing invasive from non‐invasive species based on morphology alone is often difficult for plants in a vegetative stage. In this regard, DNA barcoding could become a good alternative. In this study, 242 samples belonging to 26 species from 10 genera of aquatic plants were assessed using the chloroplast loci trnH‐psbA, matK and rbcL. Despite testing a large number of primer sets and several PCR protocols, the matK locus could not be amplified or sequenced reliably and therefore was left out of the analysis. Using the other two loci, eight invasive species could be distinguished from their respective related species, a ninth one failed to produce sequences of sufficient quality. Based on the criteria of universal application, high sequence divergence and level of species discrimination, the trnH‐psbA noncoding spacer was the best performing barcode in the aquatic plant species studied. Thus, DNA barcoding may be helpful with enforcing a ban on trade of such invasive species, such as is already in place in the Netherlands. This will become even more so once DNA barcoding would be turned into machinery routinely operable by a nonspecialist in botany and molecular genetics.     

Taxonomic revision of the humpback dolphins (Sousa spp.), and description of a new species from Australia

The taxonomy of the humpback dolphin genus Sousa has been controversial and unsettled for centuries, but recent work indicates that there are several valid species. A review of multiple lines of evidence from skeletal morphology, external morphology, coloration, molecular genetics, and biogeography, in combination provides strong support for the recognition of four species of Sousa. These include S. teuszii (Kükenthal, 1892), a species with uniform gray coloration and a prominent dorsal hump, which is found in the Atlantic Ocean off West Africa. The species S. plumbea (G. Cuvier, 1829) has similar external appearance to S. teuszii, but has a more pointed dorsal fin. It occurs in the Indian Ocean from South Africa to Myanmar (Burma). The original taxon, S. chinensis (Osbeck, 1765), is reserved for the species that has a larger dorsal fin with no prominent hump, and largely white adult coloration. It ranges from eastern India to central China and throughout Southeast Asia. Finally, we describe a new species of Sousa, the Australian humpback dolphin, which occurs in the waters of the Sahul Shelf from northern Australia to southern New Guinea. It has a lower dorsal fin, more extensive dark color on the body, and a dorsal “cape.” It is separated from the Indo‐Pacific humpback dolphin by a wide distributional gap that coincides with Wallace's Line.     

Capture efficiency and trophic adaptations of a specialist and generalist predator: A comparison

Specialist true predators are expected to exhibit higher capture efficiencies for the capture of larger and dangerous prey than generalist predators due to their possession of specialized morphological and behavioral adaptations. We used an araneophagous spider (Lampona murina) and a generalist spider (Drassodes lapidosus) as phylogenetically related model species and investigated their realized and fundamental trophic niches and their efficacy with respect to prey capture and prey handling. The trophic niche of both species confirmed that Lampona had a narrow trophic niche with a predominance of spider prey (including conspecifics), while the niche of Drassodes was wide, without any preference. DNA analysis of the gut contents of Lampona spiders collected in the field revealed that spiders form a significant part of its natural diet. Lampona captured significantly larger prey than itself and the prey captured by Drassodes. As concerns hunting strategy, Lampona grasped the prey with two pairs of legs possessing scopulae, whereas Drassodes immobilized prey with silk. Lampona possess forelegs equipped with scopulae and a thicker cuticle similar to other nonrelated araneophagous spiders. Lampona fed for a longer time and extracted more nutrients than Drassodes. We show that specialized behavioral and morphological adaptations altogether increase the hunting efficiency of specialists when compared to generalists.