Patterns Of Host Association Research Articles

A global phylogeny of leafmining Ectoedemia moths (Lepidoptera: Nepticulidae): exploring host plant family shifts and allopatry as drivers of speciation.

BackgroundHost association patterns in Ectoedemia (Lepidoptera: Nepticulidae) are also encountered in other insect groups with intimate plant relationships, including a high degree of monophagy, a preference for ecologically dominant plant families (e.g. Fagaceae, Rosaceae, Salicaceae, and Betulaceae) and a tendency for related insect species to feed on related host plant species. The evolutionary processes underlying these patterns are only partly understood, we therefore assessed the role of allopatry and host plant family shifts in speciation within Ectoedemia.MethodologySix nuclear and mitochondrial DNA markers with a total aligned length of 3692 base pairs were used to infer phylogenetic relationships among 92 species belonging to the subgenus Ectoedemia of the genus Ectoedemia, representing a thorough taxon sampling with a global coverage. The results support monophyletic species groups that are congruent with published findings based on morphology. We used the obtained phylogeny to explore host plant family association and geographical distribution to investigate if host shifts and allopatry have been instrumental in the speciation of these leafmining insects.SignificanceWe found that, even though most species within species groups commonly feed on plants from one family, shifts to a distantly related host family have occasionally occurred throughout the phylogeny and such shifts are most commonly observed towards Betulaceae. The largest radiations have occurred within species groups that feed on Fagaceae, Rosaceae, and Salicaceae. Most species are restricted to one of the seven global biogeographic regions, but within species groups representatives are commonly found in different biogeographic regions. Although we find general patterns with regard to host use and biogeography, there are differences between clades that suggest that different drivers of speciation, and perhaps drivers that we did not examine, have shaped diversity patterns in different clades.

Ancient association with Fagaceae in the aphid tribe Greenideini (Hemiptera: Aphididae: Greenideinae)

AbstractAphids are intimately associated with their host plants. Evolutionary lability of host association is common within heteroecious aphid lineages, whereas our knowledge of host‐use evolution in non‐host‐alternating aphids is limited. In the present study, we construct the first detailed molecular phylogeny of the monoecious aphid tribe Greenideini based on three mitochondrial genes (COI, COII and Cytb) and one nuclear gene (EF‐1α), and investigated its history of host association. Maximum likelihood and Bayesian phylogenies strongly support the monophyly of Greenideini and most constituent genera. Divergence time estimates and character reconstructions suggest that Greenideini may have originated during the Late Cretaceous to early Paleogene, which accompanies the origin of its ancestral host, members of the family Fagaceae. Colonisation of novel host plants has occurred multiple times during the evolutionary history of Greenideini, thereby leading to current patterns of host association. We suggest that directly shifting to novel hosts, together with expanding host range onto pre‐existing, unused plants, has probably promoted diversification in this tribe.

Population structure of Spodoptera frugiperda maize and rice host forms in South America: are they host strains?

AbstractDetermining which factors contribute to the formation and maintenance of genetic divergence to evaluate their relative importance as a cause of biological differentiation is among the major challenges in evolutionary biology. In Spodoptera frugiperda (Smith) (Lepidoptera: Noctuidae) two host strains have been recognized in the 1980s: the corn‐strain prefers maize, sorghum, and cotton, whereas the rice‐strain prefers rice and wild grasses. However, it is not clear to what extent these so‐called ‘strains’, which have also been called ‘host races’ or even ‘sibling species’, are really associated with host plants. Due to the indeterminate evolutionary status, we will use the term ‘host forms’ (sensu Funk). Here, we characterized populations collected from maize, rice, and wild grasses from three countries in South America. Using two mitochondrial cytochrome oxidase I (mtCOI) markers and 10 polymorphisms in the triose phosphate isomerase (Tpi) gene, we found various patterns of host association. Two hundred twenty‐seven nuclear amplified fragment length polymorphisms (AFLPs) markers revealed significant genetic differentiation among populations, which was generally correlated to the host from which the larvae were collected. Using a multivariate discriminant analysis and a Bayesian clustering approach, we found that individuals could be grouped into 2–5 genetically distinct clusters, depending on the method. Together, our results indicate that although host‐associated differentiation is present in this species, it does not account for all observable genetic variation and other factors must be maintaining genetic differentiation between these forms. Therefore, the term ‘host strains’ should be abandoned and ‘host forms’ should be used instead for S. frugiperda.

Molecular insight into systematics, host associations, life cycles and geographic distribution of the nematode family Rhabdiasidae

Rhabdiasidae Railliet, 1915 is a globally distributed group of up to 100 known species of nematodes parasitic in amphibians and reptiles. This work presents the results of a molecular phylogenetic analysis of 36 species of Rhabdiasidae from reptiles and amphibians from six continents. New DNA sequences encompassing partial 18S rDNA, ITS1, 5.8S rDNA, ITS2 and partial 28S rDNA regions of nuclear ribosomal DNA were obtained from 27 species and pre-existing sequences for nine species were incorporated. The broad taxonomic, host and geographical coverage of the specimens allowed us to address long-standing questions in rhabdiasid systematics, evolution, geographic distribution, and patterns of host association. Our analysis demonstrated that rhabdiasids parasitic in snakes are an independent genus sister to the rest of the Rhabdiasidae, a status supported by life cycle data. Based on the combined evidence of molecular phylogeny, morphology and life cycle characteristics, a new genus Serpentirhabdias gen. nov. with the type species Serpentirhabdias elaphe (Sharpilo, 1976) comb. nov. is established. The phylogeny supports the monophyly of Entomelas Travassos, 1930, Pneumonema Johnston, 1916 and the largest genus of the family, Rhabdias Stiles and Hassall, 1905. DNA sequence comparisons demonstrate the presence of more than one species in the previously monotypic Pneumonema from Australian scincid lizards. The distribution of some morphological characters in the genus Rhabdias shows little consistency within the phylogenetic tree topology, in particular the apical structures widely used in rhabdiasid systematics. Our data suggest that some of the characters, while valuable for species differentiation, are not appropriate for differentiation among higher taxa and are of limited phylogenetic utility. Rhabdias is the only genus with a cosmopolitan distribution, but some of the lineages within Rhabdias are distributed on a single continent or a group of adjacent zoogeographical regions. Serpentirhabdias, Entomelas and Pneumonema show rather strict specificity to their host groups. The evolution of the Rhabdiasidae clearly included multiple host switching events among different orders and families of amphibians as well as switching between amphibians and squamatan reptiles. Only a few smaller lineages of Rhabdias demonstrate relatively strict associations with a certain group of hosts.

Specialised host-use and phenophase tracking in restio leafhoppers (Cicadellidae: Cephalelini) in the Cape Floristic Region

The Cape Floristic Region (CFR) has exceptionally high plant diversity, but because there are so few studies on insect diversity and diet breadth, little is known about the relationship between plant and insect diversity. One possibility is that plant and insect diversity in the CFR are linked through host specialisation. Alternatively, the nutrient-poor soils of the CFR may favour generalist feeding strategies with insects tracking the favourable phenophases of a variety of host plants. We studied Cephalelus, a genus of leafhoppers apparently specialised on the Restionaceae, a diverse and dominant plant family in the CFR. We examined patterns of Cephalelus host association at a single site during a 24 month field survey to determine whether Cephalelus diversity is related to the partitioning of host plant or temporal niches; or whether Cephalelus tracks the most nutritive phenophases of restios by temporal host-switching. Seven Cephalelus species were recorded which varied in their seasonal abundance patterns. The majority of these species exhibited specialised host use on different Restionaceae species, with the exception of C. pickeri. This species specialised on two host plants. The populations of two dominant species, C.pickeri and C.uncinatus, tracked the phenology of their primary host plants but not of the Restionaceae in general. To conclude; we find no evidence for host-switching or generalism in Cephalelus. Instead, they appear to be host-specialised, suggesting coupling between their diversity and that of their host plants; the Restionaceae in the CFR.

Ignite ESA Session 13: Ecological Analysis Using Network Science and Graph Theory

The complex, interconnected structure and function of ecological systems is apparent in their countless direct and indirect pathways of energy (e.g., a food web), mass (e.g., a movement corridor), and information (e.g., a social network). This Ignite ESA Session united multiple fields of ecology through the lens of a single, rapidly evolving, analytical framework: network analysis. This session examined basic and applied ecological problems in both naturally formed and anthropogenically altered networks of interactions. In particular, diverse examples were presented from disease transmission, social behavior, mutualistic interactions, and species migration. The five-minute, Ignite ESA format provided a fitting outlet for rapid presentation of methods, and opened lines of communication between somewhat disparate fields of study.

Social network analysis of wild chimpanzees provides insights for predicting infectious disease risk

1. Heterogeneity in host association patterns can alter pathogen transmission and strategies for control. Great apes are highly social and endangered animals that have experienced substantial population declines from directly transmitted pathogens; as such, network approaches to quantify contact heterogeneity could be crucially important for predicting infection probability and outbreak size following pathogen introduction, especially owing to challenges in collecting real-time infection data for endangered wildlife. 2. We present here the first study using network analysis to quantify contact heterogeneity in wild apes, with applications for predicting community-wide infectious disease risk. Specifically, within a wild chimpanzee community, we ask how associations between individuals vary over time, and we identify traits of highly connected individuals that might contribute disproportionately to pathogen spread. 3. We used field observations of behavioural encounters in a habituated wild chimpanzee community in Kibale National Park, Uganda to construct monthly party level (i.e. subgroup) and close-contact (i.e. ≤ 5 m) association networks over a 9-month period. 4. Network analysis revealed that networks were highly dynamic over time. In particular, oestrous events significantly increased pairwise party associations, suggesting that community-wide disease outbreaks should be more likely to occur when many females are in oestrus. 5. Bayesian models and permutation tests identified traits of chimpanzees that were highly connected within the network. Individuals with large families (i.e. mothers and their juveniles) that range in the core of the community territory and to a lesser extent high-ranking males were central to association networks, and thus represent the most important individuals to target for disease intervention strategies. 6. Overall, we show striking temporal variation in network structure and traits that predict association patterns in a wild chimpanzee community. These empirically-derived networks can inform dynamic models of pathogen transmission and have practical applications for infectious disease management of endangered wildlife species.

Larval morphology and host use confirms ecotypic variation in Cactoblastis cactorum (Berg)

Despite their recognized importance in the literature, the contribution of native-range species interactions to invasion success has been inadequately studied. Previous authors have suggested that biases in the sampling of propagules from the native range might influence invasion success, but most contemporary invasion hypotheses focus on the development of novel interactions or a release from native consumers and competitors. When ecotypic variation exists in native host-consumer associations, the specific pattern of sampling across ecotypes could determine invasion success, especially when the genetic diversity among exotic propagules is low. The South American cactus moth, Cactoblastis cactorum (Berg), is an oligophagous consumer whose larvae feed on prickly pear cacti (subfamily Opuntioideae). The moth was collected from a small geographic area along the Argentina-Uruguay border in 1925 and was introduced to multiple continents as a biological control species, which has subsequently invaded North America. Here we show that groups defined by genetic structure in this species’ native range are concordant with distinct patterns of host association and larval morphology. Furthermore, in Florida populations, morphological traits have diverged from those found in the native range, and patterns of host association suggest that strong biases in host preference also occur in invasive populations. The documented history of C. cactorum introductions confirms that multiple attempts were made to export the moth, but that only a single ecotype was exported successfully. Additional work will be necessary to determine whether the observed host biases in North America reflect a rapid adaptation to naive hosts or a conservation of traits related to specific aspects of the host-consumer association.

The challenge of understanding the origin, pathways and extent of fungal invasions: global populations of the Neofusicoccum parvum–N. ribis species complex

AbstractAimCryptic species in the Neofusicoccum parvum–N. ribis species complex have only recently been described, invalidating previous interpretations on host and geographical distribution. This study aimed to characterize the diversity and distribution of these species and to understand the patterns of host association, likely origins and their patterns of spread.LocationAustralia, Brazil, Cameroon, Chile, China, Colombia, Ethiopia, France, Greece, India, Indonesia, Iran, Italy, Japan, Kenya, Mexico, New Zealand, Panama, Portugal, Puerto Rico, South Africa, South Korea, Spain, Swaziland, Taiwan, Thailand, Uganda, United States of America, Uruguay, Zambia and Zimbabwe.MethodsUsing the unique polymorphisms that separate species within the complex, we evaluated sequence search results available in public and in our own databases. In addition, the global distribution of diversity of N. parvum was analysed using seven microsatellite markers.ResultsNeofusicoccum parvum is found in 90 hosts across six continents and 29 countries. Neofusicoccum kwambonambiense is found on four continents, six countries and on 14 hosts; N. occulatum is found on four continents, four countries and on 11 hosts; N. umdonicola is found on two continents, countries and hosts; N. cordaticola is found on three continents, countries and hosts; N. batangarum is found on two continents, three countries and three hosts; and N. ribis is found on one host in one country. Population genetic analysis of the global N. parvum population reflects admixture and repeat introductions.Main conclusionsThis study illustrates the unfettered and frequent movement of latent pathogens across international borders. Amongst the species in the N. parvum–N. ribis complex, N. parvum is the most widespread and has been reported on the majority of the hosts studied. The current dispersal of N. parvum and its sister species is probably due to repeated introductions of plant material into new growing areas, with Eucalyptus and Vitis vinifera being two prominent candidates for material transfer.

Diversity and distribution of co-infecting Botryosphaeriaceae from Eucalyptus grandis and Syzygium cordatum in South Africa

Species in the fungal family Botryosphaeriaceae are latent pathogens on woody trees. These fungi often have a wide host range, which can include native and introduced hosts in an area. Multi-locus DNA sequence identification on a recent collection of Botryosphaeriaceae from Eucalyptus grandis and Syzygium cordatum trees in South Africa revealed cross-infectivity of several species, novel host associations and new country reports. Neofusicoccum eucalyptorum, Neofusicoccum kwambonambiense, Neofusicoccum parvum, Neofusicoccum australe and Lasiodiplodia pseudotheobromae were identified from both tree species, with L. pseudotheobromae and N. eucalyptorum isolated for the first time from S. cordatum, similar to N. kwambonambiense from Eucalyptus. This also represents the first report of L. pseudotheobromae from South Africa. Botryosphaeriaceae species on Eucalyptus species and S. cordatum are fairly well known from South Africa. However, this study revealed new associations, indicating that conclusions should not be generalized and that more intensive sampling from different areas and over time is likely to reveal distinct species and host association patterns.

The global phylogeny of the subfamily Sycoryctinae (Pteromalidae): Parasites of an obligate mutualism

The inflorescences of fig trees (Ficus, Moraceae) host well-defined, host plant specific wasp communities that lend themselves to tests of hypotheses on insect diversification. We provide the first estimate of the global molecular phylogeny for the Sycoryctinae – a large subfamily of fig wasps consisting mainly of parasitoids of fig-pollinating wasps. We find strong support for a large Old World clade that contains eight of the eleven genera, in the tribes Sycoryctini and Philotrypesini. The sister taxon is tribe Apocryptini, comprising the genera Apocrypta and Bouceka. Finally, a new tribe, Critogastrini, is raised for the genus Critogaster, sister to all other sycoryctines. At the genus level, we found a general pattern of strong host conservatism, in which closely related wasps associate with closely related figs. Despite this, there is also evidence for multiple host shifts between more distantly related figs in some wasp genera (especially Philotrypesis). We estimate Sycoryctinae to have originated 49–64Ma, after the initial co-radiation of the host figs and pollinators. Further, conservative assumptions in our analyses probably overestimate the age of the sycoryctines. Together, patterns of host association, evidence for a mix of host constraints and host shifting, and molecular dating suggest that sycoryctine parasites radiated through delayed phylogenetic tracking of their hosts. This contributes to the growing body of literature suggesting that coevolving parasites often radiate after their hosts.

Host Association of Spodoptera frugiperda (Lepidoptera: Noctuidae) Corn and Rice Strains in Argentina, Brazil, and Paraguay

Spodoptera frugiperda (J.E. Smith) is composed of two genetically distinct strains, the so-called corn strain and the rice strain. Whether the two strains differ in their host use is unclear, because laboratory experiments have not been able to show consistent host performance or preference differences between them, and field studies showed high rates of hybridization, as well as some degree asymmetric host use. To determine the distribution of the two strains and their association with host plants, we collected fall armyworm larvae from different crops (corn, rice, alfalfa, and sorghum) and grasses in 15 different localities over 4 yr in Argentina, Brazil, and Paraguay. The strain identity was analyzed using two polymorphisms in the mitochondrial cytochrome oxidase subunit I gene. We identified the corn and rice haplotypes and three types of populations were characterized based on the frequencies of the individuals that belonged to any of these haplotypes: in 44% of populations the corn haplotype predominated, in 44% of populations the rice haplotype was the most frequent, and 11% of populations showed both haplotypes at similar proportions. In total, eight populations (47%) showed the expected pattern, two populations (12%) were polymorphic within the same field, and seven populations (41%) showed the inverse pattern. Taken together, there was no consistent pattern of host association between the two sympatric genotypes and their respective host plants. This investigation supports the need for additional studies to determine which other forces keep the genotypes separate, and what is the degree of genetic differentiation between these populations.

Molecular phylogeny and divergence times of Hormaphidinae (Hemiptera: Aphididae) indicate Late Cretaceous tribal diversification

The aphid subfamily Hormaphidinae is a good candidate for the study of the evolution of insect - plant relationships. Most hormaphidine species depend on woody primary host plants and woody or herbaceous secondary host plants, and represent high host specificity, especially to their primary hosts. No detailed molecular phylogeny of Hormaphidinae has been reported, and the taxonomic positions of some taxa in this group remain unclear. To reconstruct major phylogenetic relationships and to understand the evolution of host association patterns for major lineages, we present the first detailed molecular phylogeny of Hormaphidinae, as inferred from nuclear and mitochondrial DNA sequences, using maximum parsimony, maximum likelihood, and Bayesian methods. The monophyly of Hormaphidinae and its three traditional tribes was supported, and a sister relationship between Hormaphidini and Nipponaphidini was suggested. Most inner relationships within tribes were also supported, and some novel relationships were revealed. Two subtribes of Cerataphidini are proposed. Divergence times estimated using a Bayesian approach indicate that tribal diversifications occurred during the Late Cretaceous and were coincident with the appearance of their primary host plants. The current pattern of secondary host association for the three tribes may have evolved in different time ranges.

The distinctive population structure ofColletotrichumspecies associated with olive anthracnose in the Algarve region of Portugal reflects a host–pathogen diversity hot spot

Anthracnose (Colletotrichum spp.) is an important disease of olive fruits. Diversity and biogeographic relationships of the olive anthracnose pathogens in the Algarve (Portugal) were investigated, along with host association patterns and disease levels during 2004-2007, to test the hypothesis that this region is a host-pathogen diversity hot spot. Diverse Colletotrichum acutatum and Colletotrichum gloeosporioides populations were identified based on rRNA-internal transcribed spacer and partial beta-tubulin 2 gene sequences of 95 isolates. Spatial and temporal variations in the occurrence of the eight genetic entities of the pathogens were linked to olive biogeography. Disease occurrence patterns suggest that C. acutatum populations are more stable pathogens, while C. gloeosporioides populations appear to be more influenced by favourable conditions. Three unique C. acutatum populations were identified, but none of the eight populations were dominant, with the most frequent type representing only 27%. Thus, the population structure of olive anthracnose pathogens in the Algarve is distinct from other parts of Portugal and other world locations, where only one or two genetic entities are dominant. This pattern and level of genetic diversity in a restricted area, where oleaster (wild olive tree), ancient landraces and modern cultivars of olive occur in close proximity, suggests the Algarve as a centre of diversity of the anthracnose pathogens and corroborates recent work suggesting western Mediterranean as an important centre of olive diversity and domestication.

Social play in dogs: Individual variation and change over time

Diagnosis is often equated with identification or detection when discussing parasitic diseases. Unfortunately, these are not necessarily mutually exclusive activities; diseases and infections are generally diagnosed and organisms are identified. Diagnosis is commonly predicated upon some clinical signs; in an effort to determine the causative agent, identification of genera and species is subsequently performed. Both identification and diagnosis play critical roles in managing an infection, and involve the interplay of direct and indirect methods of detection, particularly in light of the complex and expanding problem of drug-resistance in parasites. Accurate and authoritative identification that is cost- and time-effective, based on structural and molecular attributes of specimens, provides a foundation for defining parasite diversity and changing patterns of geographical distribution, host association and emergence of disease. Most techniques developed thus far have been grounded in assumptions based on strict host associations between Haemonchus contortus and small ruminants, that is, sheep and goats, and between Haemonchus placei and bovids. Current research and increasing empirical evidence of natural infections in the field demonstrates that this assumption misrepresents the host associations for these species of Haemonchus. Furthermore, the capacity of H. contortus to utilize a considerably broad spectrum of ungulate hosts is reflected in our understanding of the role of anthropogenic forcing, the ‘breakdown’ of ecological isolation, global introduction and host switching as determinants of distribution. Nuanced insights about distribution, host association and epidemiology have emerged over the past 30 years, coincidently with the development of increasingly robust means for parasite identification. In this review and for the sake of argument, we would like to delineate the diagnosis of haemonchosis from the identification of the specific pathogen. As a foundation for exploring host and parasite biology, we will examine the evolution of methods for distinguishing H. contortus from other common gastrointestinal nematodes of agriculturally significant and free-ranging wild ruminants using morphological, molecular and/or immunological methods for studies at the species and genus levels.

Campylobacter genotypes from food animals, environmental sources and clinical disease in Scotland 2005/6

A nationwide multi-locus sequence typing (MLST) survey was implemented to analyze patterns of host association among Campylobacter jejuni and Campylobacter coli isolates from clinical disease in Scotland (July 2005–September 2006), food animals (chickens, cattle, sheep, pigs and turkey), non-food animals (wild birds) and the environment. Sequence types (STs) were determined for 5247 clinical isolates and 999 from potential disease sources (augmented with 2420 published STs). Certain STs were over represented among particular sample sets/host groups. These host-associated STs were identified for all sample groups in both Campylobacter species and host associated clonal complexes (groups of related STs) were characterized for C. jejuni. Some genealogical lineages were present in both human disease and food animal samples. This provided evidence for the relative importance of different infection routes/food animal sources in human disease. These results show robust associations of particular genotypes with potential infection sources supporting the contention that contaminated poultry is a major source of human disease.

Revision of Eminoculus Schuh (Heteroptera: Miridae: Phylinae) from South Africa, with the Description of Five New Species

Abstract Eminoculus Schuh is revised and an updated diagnosis is presented for the genus. Seven species are recognized, five of which are described as new. Diagnoses, digital habitus photographs, illustrations of male and female genitalic structures, keys to both the males and females, and detailed locality are provided. Scanning micrographs of diagnostic morphological structures—the head, pronotum, scent-gland evaporatory area, vestiture, and pretarsus—are included for four species. A phylogenetic analysis is presented, using the South African species Lasiolabopella capeneri Schuh and the Nearctic Chlamydatus keltoni Schuh and Schwartz as outgroups. Host data are presented for 6 species, and patterns of host association with the “mesem” clade of the Aizoaceae are discussed.

SPECIALIZATION AND GEOGRAPHIC ISOLATION AMONGWOLBACHIASYMBIONTS FROM ANTS AND LYCAENID BUTTERFLIES

Wolbachia are the most prevalent and influential bacteria described among the insects to date. But despite their significance, we lack an understanding of their evolutionary histories. To describe the evolution of symbioses between Wolbachia and their hosts, we surveyed global collections of two diverse families of insects, the ants and lycaenid butterflies. In total, 54 Wolbachia isolates were typed using a Multi Locus Sequence Typing (MLST) approach, in which five unlinked loci were sequenced and analyzed to decipher evolutionary patterns. AMOVA and phylogenetic analyses demonstrated that related Wolbachia commonly infect related hosts, revealing a pattern of host association that was strongest among strains from the ants. A review of the literature indicated that horizontal transfer is most successful when Wolbachia move between related hosts, suggesting that patterns of host association are driven by specialization on a common physiological background. Aside from providing the broadest and strongest evidence to date for Wolbachia specialization, our findings also reveal that strains from New World ants differ markedly from those in ants from other locations. We, therefore, conclude that both geographic and phylogenetic barriers have promoted evolutionary divergence among these influential symbionts.

Host and habitat preferences of polypore fungi in Micronesian tropical flooded forests

The distribution and ecological impacts of plant-associated fungi is determined in large part by their degree of specificity for particular host species or environmental conditions. Here we evaluate the host and habitat preferences among the Aphyllophorales, a guild of wood-decay basidiomycete fungi usually considered to be host generalists. We determined the patterns of host association in three well-defined, floristically distinct, tropical wetlands — freshwater forested wetlands, saltwater mangrove forests, and peatlands with scattered trees — on the islands of Kosrae and Pohnpei in the Federated States of Micronesia. Of 33 fungal species, 20 were locally rare. Of the 11 species sufficiently common to evaluate habitat specificity, nine showed significant habitat preferences. Of eight species common enough to evaluate within-habitat host specificity, six showed strong host preferences. All except one of the nine habitat-specialized fungi showed either statistically significant host specificity or strong numerical biases toward single host species. Our results suggest that host preferences may be important in shaping the assemblages of wood-decay fungi, and that the effect of environment on the distribution of susceptible plant species, rather on the fungi themselves, may ultimately drive the apparent habitat specificity of many fungi.

Phylogeny of the Botryosphaeriaceae reveals patterns of host association

Three anamorph genera of the Botryosphaeriaceae namely Diplodia, Lasiodiplodia and Dothiorella have typically dark, ovoid conidia with thick walls, and are consequently difficult to distinguish from each other. These genera are well-known pathogens of especially pine species. We generated a multiple gene genealogy to resolve the phylogenetic relationships of Botryosphaeriaceae with dark conidial anamorphs, and mapped host associations based on this phylogeny. The multiple gene genealogy separated Diplodia, Lasiodiplodia and Dothiorella and it revealed trends in the patterns of host association. The data set was expanded to include more lineages of the Botryosphaeriaceae, and included all isolates from different host species for which ITS sequence data are available. Results indicate that Diplodia species occur mainly on gymnosperms, with a few species on both gymnosperms and angiosperms. Lasiodiplodia species occur equally on both gymnosperms and angiosperms, Dothiorella species are restricted to angiosperms and Neofusicoccum species occur mainly on angiosperms with rare reports on Southern Hemisphere gymnosperms. Botryosphaeria species with Fusicoccum anamorphs occur mostly on angiosperms with rare reports on gymnosperms. Ancestral state reconstruction suggests that a putative ancestor of the Botryosphaeriaceae most likely evolved on the angiosperms. Another interesting observation was that both host generalist and specialist species were observed in all the lineages of the Botryosphaeriaceae, with little evidence of host associated co-evolution.