Host Utilization Research Articles

Host utilization is mediated by movement of pre‐feeding Phthorimaea operculella larvae in the Nicotiana tabacum agroecosystem

AbstractThe distribution of insect herbivores within their hosts can be influenced by insect preference, plant characteristics, and biotic interactions such as refuge from predation. We observed significantly more Phthorimaea operculella (Zeller) (Lepidoptera: Gelechiidae) larvae in the lower portion of commercial tobacco plants, Nicotiana tabacum L. (Solanaceae), an occasional host, and sought to explain this distribution pattern. Phthorimaea operculella are oligophagous leaf miners of solanaceous plants, including cultivated crops. Females lay their eggs in the soil beneath N. tabacum plants rather than on the foliage, forcing newly hatched larvae to search for host tissue. We hypothesized that P. operculella larvae were establishing in the lower portion of N. tabacum plants because either they gained a performance advantage, or it was the first suitable leaf material contacted. To measure within‐plant larval performance, neonates were released in cages on leaves in the upper, middle, and lower stalk positions of the plant before and after the plant flowered. Phthorimaea operculella performed significantly better on younger plants and in the top leaves. To test larval ability to move within and between plants, we removed leaves at four heights to increase the distance newly hatched larvae must travel. Larval establishment was highest on plants with no leaves removed, but larvae were able to move an average distance of over 70 cm from release point to host leaves in plants directly above the release point and adjacent plants. Phthorimaea operculella larvae appear to utilize suboptimal N. tabacum host tissue to maximize their chances of survival.

Socio-Economic Characteristics and Marketing Behaviour of Lac Growers in Raigarh District of Chhattisgarh

The study pertains to data collected from randomly selected 100 lac growers in Raigarh district of Chhattisgarh for the year 2008-09. The study indicated that 40% lac growers were medium farmers followed by small (27%), marginal (22%), semi-medium (8%) and large (3%). The majority of lac growers had education up to high school level. Share of income from lac was 17.3% and 33% of total income and farm income respectively of lac growers. In case of off-farm income, maximum income was contributed by forest produce which was 23.1% of total income of farmers. The host utilization percentage was maximum for Palas (44.3%) followed by Kusum (42.1%), other hosts (30.0%) and Ber (25.4%). About 59.0% lac growers produced lac with average production of 52.5 kg, 29.0% lac growers had average production of 135.2 kg and 12.0% lac growers had average production of 225.9 kg annually. The study of marketing behavior indicated that around 84% grower sold their produce either in village or in the market/ Haat up to 5 km radius. Grading practice was less operational in the area. Lac was used as a cash crop and majority of farmers sold lots of 5-10 kg. Around 88% farmers sold lac immediately after harvesting. Implications of the present study will be helpful in strengthening the socio-economic condition of lac growers and lac marketing scenario in Chhattisgarh.

Analysis of landscape-scale insect pest dynamics and pesticide use: an empirical and modeling study

Diverse agricultural landscapes help support many ecosystem services, including insect pest suppression. Yet questions remain about how landscape diversification affects insects with differing life histories, and how interactions between pest management and land use alter insect population dynamics. Here we introduce empirical data illustrating how population dynamics and pest management of two economically important insect pests in maize (Zea mays), the European corn borer (ECB; Ostrinia nubilalis) and the western corn rootworm (WCR; Diabrotica virgifera), may vary with land use. We then explore the role of landscape in agricultural pest suppression with a spatially explicit computational model of herbivore population dynamics that includes pest management measures and insect life-history parameters (diet breadth, dispersal distance, and reproductive rate). While field results showed that WCR densities were lower in diverse than in simple agricultural landscapes, ECB damage to maize appeared unrelated to land use. Indeed, our stable carbon isotope analysis shows that one critical difference in the life histories of the two insects is host utilization: WCR utilized non-maize hosts (0%) at a lower rate than ECB (11%). However, management for both pests was consistently related to land use: less transgenic Bt maize and less insecticide is used per maize hectare in U.S. states with less maize. Consistent with field observations, our model predicts that landscape diversification results in reduced insecticide use and suggests that specialist pests are more affected by land-use changes than generalists. The model further predicts that insects with high reproductive rates are less sensitive to land-use change than insects with low reproductive rates and that dispersal distance is not an important factor regulating densities of highly dispersive insect pests in agricultural landscapes. While our study suggests that landscape diversification may not suppress all pests, it also suggests that diverse agricultural landscapes are correlated with consistently lower pesticide usage.

Wild-Type Drosophila melanogaster as a Model Host to Analyze Nitrogen Source Dependent Virulence of Candida albicans

The fungal pathogen Candida albicans is a common cause of opportunistic infections in humans. We report that wild-type Drosophila melanogaster (OrR) flies are susceptible to virulent C. albicans infections and have established experimental conditions that enable OrR flies to serve as model hosts for studying C. albicans virulence. After injection into the thorax, wild-type C. albicans cells disseminate and invade tissues throughout the fly, leading to lethality. Similar to results obtained monitoring systemic infections in mice, well-characterized cph1Δ efg1Δ and csh3Δ fungal mutants exhibit attenuated virulence in flies. Using the OrR fly host model, we assessed the virulence of C. albicans strains individually lacking functional components of the SPS sensing pathway. In response to extracellular amino acids, the plasma membrane localized SPS-sensor (Ssy1, Ptr3, and Ssy5) activates two transcription factors (Stp1 and Stp2) to differentially control two distinct modes of nitrogen acquisition (host protein catabolism and amino acid uptake, respectively). Our results indicate that a functional SPS-sensor and Stp1 controlled genes required for host protein catabolism and utilization, including the major secreted aspartyl protease SAP2, are required to establish virulent infections. By contrast, Stp2, which activates genes required for amino acid uptake, is dispensable for virulence. These results indicate that nutrient availability within infected hosts directly influences C. albicans virulence.

Oviposition and performance in natural hosts in cactophilic Drosophila

The cactus–yeast–Drosophila model system provides an excellent opportunity to investigate the significance of ecological factors in evolution. D. buzzatii and D. koepferae are sister species, with partially overlapping distribution ranges and a certain degree of habitat overlap. The main breeding and feeding resources of D. buzzatii are the decaying cladodes of prickly pears (genus Opuntia), whereas D. koepferae utilizes mainly columnar cacti of the genera Cereus and Echinopsis. These host plants differ in their chemical composition, the microflora associated to the decaying process and patterns of spatial and temporal predictability. The aim of the present work is to investigate host plant selection and utilization of two different cactus hosts. We report the results of field and laboratory studies examining behavioral traits related to egg-laying (oviposition preference and host acceptance) and several measures of performance (viability, developmental time, wing morphology and starvation resistance) in flies reared in the two main host cacti that D. buzzatii and D. koepferae exploit in the studied area: O. sulphurea and E. terschekii. The main conclusion of our study is the clear connection between the distribution of the cactophilic species, D. buzzatii and D. koepferae, and the abundance of the two main natural hosts, which is line with the remarkable influence that cactus hosts impose on larval and adult life history traits and behavioral traits. Overall, the results of field and laboratory work point to the important role of host plant shifts in the evolutionary history of these species.

A molecular phylogeny of the Cephinae (Hymenoptera, Cephidae) based on mtDNA COI gene: a test of traditional classification.

Cephinae is traditionally divided into three tribes and about 24 genera based on morphology and host utilization. There has been no study testing the monophyly of taxa under a strict phylogenetic criterion. A molecular phylogeny of Cephinae based on a total of 68 sequences of mtDNA COI gene, representing seven genera of Cephinae, is reconstructed to test the traditional limits and relationships of taxa. Monophyly of the traditional tribes is not supported. Monophyly of the genera are largely supported except for Pachycephus. A few host shift events are suggested based on phylogenetic relationships among taxa. These results indicate that a more robust phylogeny is required for a more plausible conclusion. We also report two species of Cephus for the first time from Turkey.

Efficiency of host utilisation by coleopteran parasitoid

In insect larvae, optimising food utilisation with respect to available meals and time is essential for achieving maximum adult body size, which is a relevant proxy of fitness. We studied the efficiency of food conversion, body size, mortality, and development time in a solitary idiobiont ectoparasitoid, Brachinus explodens (Coleoptera: Carabidae), reared in the laboratory on the pupae of another carabid genus, Amara. The efficiency of conversion index (ECI – ratio of ingested to assimilated food) was, on average, 54.1±1.1% (n=76), with a minimum of 26.9% and a maximum of 81.6%. The rate of increase in biomass gained (Wgained) with biomass of the host was constant in females, but it decreased in males over the range of host body mass. Females, therefore, grew heavier from hosts of the same mass compared to males. Body length increased with the host mass and was correlated with Wgained identically for both sexes. Mortality was unaffected by the host mass, but it significantly increased below 20°C. In contrast, the development time of the feeding phase of the larva increased with the host mass at 20.3 and 23.7°C, but it remained unaffected at 26.9°C and in all three temperatures considering pupal development. Wgained increased with development time up to ca. 8days of larval feeding at 23.7°C. To our knowledge, our data are the first on food utilisation in solitary idiobiont coleopteran ectoparasitoids, and they present the highest values of ECI in insects.

Trade-offs of host use between generalist and specialist Helicoverpa sibling species: adult oviposition and larval performance

Much attention has been paid to the question of the relative importance of female behaviour versus larval feeding capacities in determining the host range of herbivorous insects. Host-use trade-offs displayed by generalist and specialist sister species of the genus Helicoverpa were evaluated to examine the relationship between maternal choice and offspring performance. The prediction of optimal oviposition theory, that females will choose to lay eggs on plants on which their offspring perform best as larvae, was tested by measuring oviposition preference and larval performance of Helicoverpa armigera and H. assulta on tobacco, sunflower, and hot pepper. These two measures were more highly correlated in the specialist H. assulta. Both species exhibited the same oviposition preference ranking: tobacco > sunflower > hot pepper. H. armigera larvae preferred sunflower, followed by tobacco and hot pepper; while H. assulta larvae preferred tobacco to sunflower and hot pepper, consistent with their mothers' oviposition preference. Duration of the total period from egg to adult emergence for each species was significantly shorter on the host plant preferred by the larvae. H. assulta had shorter larval duration and higher relative growth rate than H. armigera on tobacco and hot pepper, and vice versa for sunflower, indicating species differences in host utilization. Thus, while only the specialist H. assulta displayed the predicted optimal oviposition pattern, females of both species show the least preference for the plant on which their offspring perform worst. Selection for optimal oviposition may be stronger on the specialist, which has fewer choices and lower lifetime fecundity than the generalist.

Specialized Host Utilization of <I>Macrosiphum euphorbiae</I> on a Nonnative Weed Host, <I>Solanum sarrachoides</I>, and Competition With <I>Myzus persicae</I>

The potato aphid, Macrosiphum euphorbiae (Thomas), (Homoptera: Aphididae), is a polyphagous aphid known to feed on over 200 plant species across 20 families. Although this aphid is known as one of the potato (Solanum tuberosum L.) colonizing aphids, field observations for populations of M. euphorbiae in southern Idaho indicated that they preferentially settled and colonized hairy nightshade, Solanum sarrachoides (Sendtner), plants rather than potato plants. Laboratory investigations revealed that M. euphorbiae survived only on S. sarrachoides and not on potato. A series of subsequent laboratory experiments conducted using laboratory-reared and field-collected aphids confirmed that M. euphorbiae survived only on S. sarrachoides. Experiments also showed that M. euphorbiae produced more winged morphs (alatae) than Myzus persicae on S. sarrachoides when reared alone under similar conditions. Furthermore, we documented intraguild competition between M. euphorbiae and M. persicae on S. sarrachoides. Results suggested that M. euphorbiae can potentially suppress M. persicae on S. sarrachoides. Competition studies reiterated that M. euphorbiae produced more alatae than M. persicae. Results also indicated that M. euphorbiae may have specialized on S. sarrachoides. The loss of polyphagous abilities of this M. euphorbiae “biotype” is intriguing and the factors responsible for specialized host utilization pattern remain to be elucidated.

Foraging behaviours of Diachasmimorpha kraussii (Fullaway) (Hymenoptera: Braconidae) and its host Bactrocera tryoni (Froggatt) (Diptera: Tephritidae) in a nectarine (Prunus persica (L.) Batsch var. nectarina (Aiton) Maxim) orchard

Diachasmimorpha kraussii is a larval parasitoid of dacine fruit flies. Host utilisation behaviour, including field foraging behaviour, is poorly known in this species. The diurnal foraging behaviour of D. kraussii and one of its common hosts, Bactrocera tryoni, in a nectarine orchard was concurrently recorded. Observations of mating, resting, feeding and oviposition were taken two-hourly on 42 trees, commencing at 07:00 h and terminating at 17:30 h, for 17 days. Resting and oviposition were common events within the orchard for both species, while mating behaviours were not recorded in the orchard for either species. Feeding was not observed for D. kraussii and was rare for B. tryoni. At the level of the individual tree there was a very weak, but significant correlation between parasitoid and fly abundance over a day, but when broken down to the individual observation periods the correlations were absent, or were weakly significant in an inconsistent manner (i.e. sometimes positively correlated, sometimes negatively correlated). At the orchard level, abundance of the parasitoid was not correlated with adult fly abundance. Results suggest that D. kraussii forage independently to adult B. tryoni, a result consistent with a prediction that their foraging is largely driven by larval or plant damage cues.

Evolutionary diversification of bruchine beetles: climate-dependent traits and development associated with pest status

A number of insect species infest human households and stored foods and products, leading to their designation as pests. Until recently, little was known about the factors driving the evolution of pests that feed on stored dry foods. Here, I review the effects of changes in climate and species interactions on the evolution and ecology of beetles that feed on dried seeds/grains. My review focuses on evidence that the host utilization by part of the species in the subfamily Bruchinae (Chrysomelidae) is a preadaptation for utilizing stored dry seeds and grains, thus leading to their status as a pest. These and other stored product pest beetles retain a higher percentage of water in their body, relative to the water content of their diet, than beetles that feed on fresh crops. I review the studies that have documented adaptation, acclimation and polyphenetic response to high temperatures and desiccation and/or made direct comparisons between these traits between developmental stages, populations and among higher taxonomic groups. Finally, I review evidence for the effects of environmental change on insect host-parasitoid and competitor assemblages.

Host Utilization and Distribution of Nubenocephalid Gregarines (Eugregarinorida: Actinocephalidae) Parasitizing Argia spp. (Odonata: Zygoptera) in the Central United States

Gregarine host specificity has been the cornerstone of gregarine taxonomy for nearly a century. Several laboratory experiments have accepted strict host specificity by failure to cross-infect distantly related hosts with unrelated gregarine species. These empirical studies are not feasible for all gregarine hosts, especially nondomesticated groups. Additionally, studies of gregarine distributions have always focused on insect hosts of disparate groups, rather than targeting potential hosts species within a single genus and their congeneric gregarines. This study addresses host utilization of nubenocephalid gregarines parasitizing the odonate genus Argia (Odonata: Zygoptera: Coenagrionidae). Populations of 9 species of adult Argia were collected, dissected, and observed for gregarine infection during the April–September flight seasons in 2007 from 17 localities in the central United States. On average, 2.5 species of Argia were collected at each locality. A species of Nubenocephalus—Nubenocephalus nebraskensis, Nubenocephalus secundus, or Nubenocephalus spp.—was collected from every infected population of Argia except for the Argia vivida population at Prairie Dog Town Fork-Red River, Randall County (Co.), Texas, U.S.A. Nubenocephalus secundus utilizes at least 7 of the 9 argid hosts sampled whereas N. nebraskensis was collected from only 2 argid species. Only Argia translata was observed to host both N. secundus and N. nebraskensis. These patterns of host utilization by nubenocephalid gregarines represent an ecotypic gregarine assemblage rather than a vicariant assemblage, demonstrating that nubenocephalid gregarines do not differentiate between species of Argia as hosts.

Host Utilization of Field-Caged Native and Introduced Thistle Species by Rhinocyllus conicus

Rhinocyllus conicus Fröelich was introduced from Europe into North America as a biological control agent of the exotic weed Carduus nutans L. Concern exists over the feeding of this weevil on at least 25 species of native Cirsium thistles. Beginning in 2008, cage studies isolating adults of R. conicus on buds and flower heads of all eight thistle species (native and introduced) recorded from Tennessee were conducted to test if R. conicus could use these species for reproduction and what impacts larval feeding of R. conicus may have on seed production. Larvae of R. conicus completed development in heads of the native species C. carolinianum (Walter) Fernald and Schubert. and C. horridulum Michaux, and significant reductions in seed numbers of both species occurred during 2008. Rhinocyllus conicus oviposited on both C. carolinianum and C. horridulum at significantly greater levels than the introduced species C. arvense (L.) Scopoli and C. vulgare (Savi) Tenore. Infested heads of C. carolinianum contained numbers of R. conicus per centimeter of plant head width similar to Ca. nutans in 2008, and both native species contained numbers of R. conicus per centimeter of plant head width similar to C. arvense and C. vulgare in 2009. Body length was similar between R. conicus reared on native thistles and its target host Ca. nutans. This report is the first documentation of R. conicus feeding and reproducing on C. carolinianum and C. horridulum. Although R. conicus has been observed only on introduced thistles in naturally occurring populations in this region, the utilization of C. carolinianum and C. horridulum as host species in controlled conditions warrants continued monitoring of field populations and further investigation into factors that may influence nontarget feeding in the future.

Host Plant Phenology Affects Performance of an Invasive Weevil,Phyllobius oblongus(Coleoptera: Curculionidae), in a Northern Hardwood Forest

We investigated how host plant phenology and plant species affected longevity, reproduction, and feeding behavior of an invasive weevil. Phyllobius oblongus L. (Coleoptera: Curculionidae) is common in northern hardwood forests of the Great Lakes Region. Adults emerge in spring, feed on foliage of woody understory plants, and oviposit in the soil. Preliminary data indicate that adults often feed on sugar maple, Acer saccharum Marshall, foliage early in the season, then feed on other species such as raspberry, Rubus spp. Whether this behavior reflects temporal changes in the quality of A. saccharum tissue or merely subsequent availability of later-season plants is unknown. We tested adult P. oblongus in laboratory assays using young (newly flushed) sugar maple foliage, old (2-3 wk postflush) sugar maple foliage, and raspberry foliage. Raspberry has indeterminate growth, thus always has young foliage available for herbivores. Survival, oviposition, and leaf consumption were recorded. In performance assays under no-choice conditions, mated pairs were provided one type of host foliage for the duration of their lives. In behavioral choice tests, all three host plants were provided simultaneously and leaf area consumption was compared. Adults survived longer on and consumed greater amounts of young maple and raspberry foliage than old maple foliage. P. oblongus preferred young maple foliage to old maple foliage early in the season, however, later in the growing season weevils showed less pronounced feeding preferences. These results suggest how leaf phenology, plant species composition, and feeding plasticity in host utilization may interact to affect P. oblongus population dynamics.

The Gulf Coast Tick: A Review of the Life History, Ecology, Distribution, and Emergence as an Arthropod of Medical and Veterinary Importance

The Gulf Coast tick, Amblyomma maculatum Koch (Acari: Ixodidae), is a unique univoltine ectoparasite of seven vertebrate host classes in the Western Hemisphere that is increasingly recognized as a pest of livestock and wildlife, a vector of pathogens to humans and canines, and a putative vector of Ehrlichia ruminantium, the causal agent of heartwater, a fatal foreign animal disease of ruminants resident in the Caribbean. This review assembles current and historical literature encompassing the biology, ecology, and zoogeography of this tick and provides new assessments of changes in cyclical population distribution, habitat associations, host utilization, seasonal phenology, and life history. These assessments are pertinent to the emergence of A. maculatum as a vector of veterinary and medical importance, and its pest management on livestock and other animals.

Spatially patterned guild structure in larval parasitoids of cyclically outbreaking winter moth populations

1. Wide temporal fluctuations in host abundance are a potential source of instability and stochasticity in the spatiotemporal population dynamics of associated parasitoid species. Within parasitoid guilds (i.e. parasitoids with similar modes of host utilisation), a conceivable outcome is guild organisation according to a lottery model, in which guild members attain local dominance by colonising previously emptied habitats during increasing host density, before other guild members. In the spatial dimension, an expected manifestation of such dynamics is variable guild structure even across homogeneous habitats.2. We examined the extent of large‐scale spatial patterning of guild characteristics in larval parasitoid wasps associated with cyclically outbreaking populations of the geometrid mothOperophtera brumatain northern Fennoscandia. The study was performed at the onset of the crash‐phase of the geometrid's outbreak cycle, along a 70‐km transect in costal northern Norway, characterised by largely homogeneous environmental conditions, except for a small climatic gradient.3. There was a distinct large‐scale spatial turnover in dominance among the major parasitoid groups (i.e. guild structure) inO.brumataalong the transect, whereas the total prevalence rate of the guild and its diversity showed no consistent variation. Guild structure was unrelated to host density.4. Although group‐specific responses to a slight spatial climatic gradient cannot be rejected as a causal mechanism, we conclude that our results are consistent with the expectation from large‐scale stochastic extinction‐recolonisation dynamics among functionally equivalent parasitoids relying on a host with strongly cyclic population fluctuations.

Evolution of host utilization patterns in the seed beetle genus Mimosestes Bridwell (Coleoptera: Chrysomelidae: Bruchinae)

The evolutionary history of diet breadth expansion and intergeneric host shifts in the seed beetle genus Mimosestes were reconstructed to investigate the process of host range expansion in phytophagous insects. The evolutionary correlation between diet breadth and variation in oviposition behavior of Mimosestes was also examined to estimate the process of generalist evolution within the genus. Ancestral state reconstruction based on a molecular phylogeny inferred from three mitochondrial markers (16S rRNA, 12S rRNA, and COI) and one nuclear marker (EF-1α) revealed that host utilization patterns were shaped by repeated colonizations to novel or pre-adapted host plants. Neither plant genus and species group level host conservatism nor an evolutionary tendency toward specialization was found in the genus, contrary to the expectations of plant–insect co-evolutionary theory. In addition, statistical analyses revealed that diet breadth was significantly correlated with oviposition behavior, suggesting that behavioral factors such as the oviposition preferences of female seed beetles affect the expansion of diet breadth in generalists.

Host Use of <I>Bactrocera latifrons</I>, a New Invasive Tephritid Species in Tanzania

Bactrocera latifrons (Hendel) is a pest of Asian origin, first detected in Africa in 2006. We assessed the host utilization of this quarantine pest in Morogoro region, eastern central Tanzania, by collecting a wide range of cultivated and wild host plants of species belonging to Solanaceae and Cucurbitaceae from April 2007 to April 2008. Fruit were collected from 29 plant species and varieties (16 Solanaceae and 13 Cucurbitaceae) in all agroecological zones of Morogoro region. Twelve solanaceous fruit species yielded B. latifrons of which four are new host records: Capsicum annuum L. cov. longum A. DC., Capsicum chinense Jacq., Solanum sodomeum L., and Solanum scabrum Mill. Similarly, three cucurbitaceous fruit species provided positive rearings and are new host records: Citrullus lanatus (Thunb.) Matsum & Nakai, Cucumis dipsaceus L., and Momordica cf trifoliata L. The infestation rate and incidence of the pest was mainly high in the solanaceous hosts of nightshades (Solanum nigrum L. and Solanum scabrum) and African eggplants (Solanum aethiopicum Lam. and Solanum anguivi). In a host preference study involving limited number of cultivated solanaceous crops, S. scabrum was recorded as the most preferred host. The pest has been found to outnumber Bactrocera invadens (Drew et al.), Bactrocera cucurbitae (Coquillett), and Ceratitis capitata (Wiedemann) in most of the common solanaceous hosts.

Host preference and species richness of wood-inhabiting aphyllophoraceous fungi in a cool temperate area of Japan

We examined the species richness and host utilization patterns of wood-inhabiting aphyllophoraceous fungi (polypores and related fungi) in an old-growth beech and oak forest in a cool, temperate area of Japan. Coarse woody debris (CWD) ≥ 20 cm diam within a 6 ha plot was surveyed in Sep 2002. Tree genus, diameter, decay class and tree part of CWD samples were recorded. Fruiting bodies of aphyllophoraceous fungi that arose from the CWD were surveyed three times and identified to species. In total 256 CWD samples from 12 tree genera were surveyed with Quercus being the most frequent followed by Castanea and Fagus. From 196 CWD samples we recorded 436 wood-inhabiting fungi belonging to 63 species. Fifteen fungal species had at least 10 records, with Hymenochaete rubiginosa, Daedalea dickinsii, Xylobolus frustulatus, Rigidoporus cinereus and the small form of Fomes fomentarius being the most frequent. The number of fungal species that appeared on Fagus was significantly larger than that on Castanea, when the number of fruiting bodies collected was at least 50. The occurrences of the 15 dominant fungal species, except Trametes versicolor, were related to traits of the CWD. Tree genus was a predictor variable that affected the appearance of 11 of the 15 species of wood-inhabiting fungi. Only the tree part was selected for the models of Rigidoporus eminens, Schizopora flavipora and Stereum ostrea. Our results suggest that tree genus and tree part are important factors determining fungal community structure because these were selected as complementary predictor variables. Both oak and beech appear to be the most important tree genera for maintaining wood-inhabiting fungal species richness because the fungal flora formed on oak CWD is nearly complementary to those on chestnut, with low fungal species richness.

Contrasting mtDNA diversity and population structure in a direct‐developing marine gastropod and its trematode parasites

The comparative genetic structure of hosts and their parasites has important implications for their coevolution, but has been investigated in relatively few systems. In this study, we analysed the genetic structure and diversity of the New Zealand intertidal snail Zeacumantus subcarinatus (n = 330) and two of its trematode parasites, Maritrema novaezealandensis (n = 269) and Philophthalmus sp. (n = 246), using cytochrome c oxidase subunit I gene (COI) sequences. Snails and trematodes were examined from 11 collection sites representing three regions on the South Island of New Zealand. Zeacumantus subcarinatus displayed low genetic diversity per geographic locality, strong genetic structure following an isolation by distance pattern, and low migration rates at the scale of the study. In contrast, M. novaezealandensis possessed high genetic diversity, genetic homogeneity among collection sites and high migration rates. Genetic diversity and migration rates were typically lower for Philophthalmus sp. compared to M. novaezealandensis and it displayed weak to moderate genetic structure. The observed patterns likely result from the limited dispersal ability of the direct developing snail and the utilization of bird definitive hosts by the trematodes. In addition, snails may occasionally experience long-distance dispersal. Discrepancies between trematode species may result from differences in their effective population sizes and/or life history traits.