Patterns Of Host Association Research Articles

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.

Biodiversity, host specificity, and dominance by eusocial species among sponge‐dwelling alpheid shrimp on the Belize Barrier Reef

ABSTRACTAlpheid shrimp represent an abundant and diverse, but poorly characterized, component of the cryptic biodiversity of coral reefs worldwide. Sponge‐inhabiting alpheids provide a promising model system for exploring patterns of cryptic reef biodiversity because their habitats (hosts) are discrete and qualitatively distinct units. We tabulated data from 14 years of collections at Carrie Bow Cay, Belize to quantify patterns of diversity, host specificity, and dominance among sponge‐dwelling shrimp (Synalpheus), with special attention to eusocial species. From > 600 sampled sponges of 17 species, we recognized at least 36 Synalpheus shrimp species. Of these, 15 (42%) were new to science. Species accumulation curves suggest that we have sampled most of the Synalpheus diversity at Carrie Bow Cay. Diversity of sponge‐dwelling Synalpheus was slightly higher in shallow water, probably because of greater habitat diversity, than in deep water. Host specificity was surprisingly high, with > 50% of all shrimp species found in only a single sponge species each, although some shrimp species used as many as six hosts. Cohabitation of individual sponges by multiple shrimp species was rarer than expected by chance, supporting previous distributional and behavioural evidence that competition for hosts is strong and moulds patterns of host association. The fauna of most well‐sampled sponge species was dominated, both in numbers of individuals and in frequency of occurrence, by eusocial species. Eusocial shrimp species also inhabited a significantly greater number of sponge species than did non‐social shrimp. Consequently, > 65% of shrimp in our quantitative samples belonged to the four eusocial species, and on a per‐species basis, eusocial species were 17 times as abundant as non‐social species. Our data suggest that the highly diverse sponge‐dwelling shrimp assemblage of the Belize Barrier Reef is structured by competition, and that eusociality has allowed a small number of species to dominate the sponge resource.

Radiation of gall midges (Diptera: Cecidomyiidae) in Japan

Summary Based on literature surveys and morphological and DNA sequencing data, we examined patterns of host association at the generic level for the Japanese gall midges. Many examples of association of a gall midge genus with a particular host plant genus are known. We found that associations exist between Rabdophaga and Salix, Hartigiola and Fagus , Rhopalomyia and Artemisia, and Daphnephila and Machilus , whereas the host range of some large genera, such as Asphondylia , Contarinia , Dasineura , and Lasioptera spans different plant families. Most Rabdophaga and some Rhopalomyia species seem to have colonized the Japanese Archipelago after radiation in the Eurasian Continent. Daphnephila came to Japan from the Oriental Region where they radiated on Machilus . Most Fagus gall midges seem to have diversified on relic Fagus species in the eastern Palearctic Region. Some Hartigiola species appear to have radiated in the Japanese Archipelago. Although Asphondylia has a wide host range at the generic level, most Japanese Asphondylia species and segregates are close to each other genetically, which means they are now spreading to various plant genera.

Genotypic and phenotypic diversity in Colletotrichum acutatum, a cosmopolitan pathogen causing anthracnose on a wide range of hosts

SUMMARY Colletotrichum acutatum causes anthracnose on a wide range of hosts including woody and herbaceous crops, ornamentals, fruits and conifers. Almond, citrus, lupin, olive and strawberry are some of the crops in which C. acutatum diseases are economically important. With the application of molecular markers and diagnostic PCR over the last 10-15 years, C. acutatum was identified as a major pathogen on a number of hosts instead of or along with C. gloeosporioides. C. acutatum displays high levels of genotypic and phenotypic diversity. The global populations of this cosmopolitan pathogen fit into at least eight distinct molecular groups, A1-A8, which show some degree of correlation with the morphological characteristics and varying patterns of host association and geographical distribution. The pathogen has complex epidemiology, exhibiting pathogenic and non-pathogenic lifestyles on target hosts, non-target crops and weeds. C. acutatum populations also show pathogenic variability and cross-infection potential in relation to a number of hosts. Molecular genetic tools are being developed to investigate the pathogenicity mechanisms of this key pathogen. This article mainly focuses on the global population diversity in C. acutatum, pathogen epidemiology and diagnosis, host colonization processes, and the development of tools for the identification and analysis of genes associated with pathogenicity. Background information on the pathogen origin, host range, disease symptoms and disease management strategies is also provided.

Molecular systematics of rhizobia based on maximum likelihood and Bayesian phylogenies inferred from rrs, atpD, recA and nifH sequences, and their use in the classification of Sesbania microsymbionts from Venezuelan wetlands

A well-resolved rhizobial species phylogeny with 51 haplotypes was inferred from a combined atpD+ recA data set using Bayesian inference with best-fit, gene-specific substitution models. Relatively dense taxon sampling for the genera Rhizobium and Mesorhizobium was achieved by generating atpD and recA sequences for six type and 24 reference strains not previously available in GenBank. This phylogeny was used to classify nine nodule isolates from Sesbania exasperata, S. punicea and S. sericea plants native to seasonally flooded areas of Venezuela, and compared with a PCR-RFLP analysis of rrs plus rrl genes and large maximum likelihood rrs and nifH phylogenies. We show that rrs phylogenies are particularly sensitive to strain choice due to the high levels of sequence mosaicism found at this locus. All analyses consistently identified the Sesbania isolates as Mesorhizobium plurifarium or Rhizobium huautlense. Host range experiments on ten legume species coupled with plasmid profiling uncovered potential novel biovarieties of both species. This study demonstrates the wide geographic and environmental distribution of M. plurifarium, that R. galegae and R. huautlense are sister lineages, and the synonymy of R. gallicum, R. mongolense and R. yanglingense. Complex and diverse phylogeographic, inheritance and host-association patterns were found for the symbiotic nifH locus. The results and the analytical approaches used herein are discussed in the context of rhizobial taxonomy and molecular systematics.

Associations between mycophagous Drosophila and their Howardula nematode parasites: a worldwide phylogenetic shuffle

Little is known about what determines patterns of host association of horizontally transmitted parasites over evolutionary timescales. We examine the evolution of associations between mushroom-feeding Drosophila flies (Diptera: Drosophilidae), particularly in the quinaria and testacea species groups, and their horizontally transmitted Howardula nematode parasites (Tylenchida: Allantonematidae). Howardula species were identified by molecular characterization of nematodes collected from wild-caught flies. In addition, DNA sequence data is used to infer the phylogenetic relationships of both host Drosophila (mtDNA: COI, II, III) and their Howardula parasites (rDNA: 18S, ITS1; mtDNA: COI). Host and parasite phylogenies are not congruent, with patterns of host association resulting from frequent and sometimes rapid host colonizations. Drosophila-parasitic Howardula are not monophyletic, and host switches have occurred between Drosophila and distantly related mycophagous sphaerocerid flies. There is evidence for some phylogenetic association between parasites and hosts, with some nematode clades associated with certain host lineages. Overall, these host associations are highly dynamic, and appear to be driven by a combination of repeated opportunities for host colonization due to shared breeding sites and large potential host ranges of the nematodes.

Molecular diversity of arbuscular mycorrhizal fungi and patterns of host association over time and space in a tropical forest.

We have used molecular techniques to investigate the diversity and distribution of the arbuscular mycorrhizal (AM) fungi colonizing tree seedling roots in the tropical forest on Barro Colorado Island (BCI), Republic of Panama. In the first year, we sampled newly emergent seedlings of the understory treelet Faramea occidentalis and the canopy emergent Tetragastris panamensis, from mixed seedling carpets at each of two sites. The following year we sampled surviving seedlings from these cohorts. The roots of 48 plants were analysed using AM fungal-specific primers to amplify and clone partial small subunit (SSU) ribosomal RNA gene sequences. Over 1300 clones were screened for random fragment length polymorphism (RFLP) variation and 7% of these were sequenced. Compared with AM fungal communities sampled from temperate habitats using the same method, the overall diversity was high, with a total of 30 AM fungal types identified. Seventeen of these types have not been recorded previously, with the remainder being similar to types reported from temperate habitats. The tropical mycorrhizal population showed significant spatial heterogeneity and nonrandom associations with the different hosts. Moreover there was a strong shift in the mycorrhizal communities over time. AM fungal types that were dominant in the newly germinated seedlings were almost entirely replaced by previously rare types in the surviving seedlings the following year. The high diversity and huge variation detected across time points, sites and hosts, implies that the AM fungal types are ecologically distinct and thus may have the potential to influence recruitment and host composition in tropical forests.

GEOGRAPHIC VARIATION IN HOST SPECIFICITY REVEALS HOST RANGE EVOLUTION INUROLEUCON AMBROSIAEAPHIDS

Some herbivorous insect taxa that exhibit otherwise conservative patterns of host association include species or populations with atypical host specificities. These species provide special opportunities to study the evolution of host range. Uroleucon ambrosiae aphids present an example. Most Uroleucon species are monophagous on particular host plants from the Asteraceae, and U. ambrosiae appears to specialize on the giant ragweed, Ambrosia trifida, in eastern North America. In the American Southwest, however, U. ambrosiae uses a variety of asteraceous taxa as hosts. For the present study, we assayed host-associated behaviors of U. ambrosiae from both eastern and southwestern regions of the United States on each of four asteraceous genera. Data from choice and no-choice experiments and electrical penetration graph analyses revealed highly significant differences in the acceptability of the four test plants. Plant taxa were ranked in the same order across multiple behavioral assays by aphids from both regions. However, eastern and southwestern aphids exhibited significantly different patterns of behavior. Ambrosia was the most highly accepted plant by aphids from both regions, but southwestern aphids accepted the other test plants more readily than did eastern aphids, indicating geographic variation in degree of host specificity. This regional differentiation held for aphids reared under controlled conditions for the EPG studies, indicating a genetic basis for population divergence in U. ambrosiae host-use traits. We speculate that the generalism within U. ambrosiae is an evolutionarily derived trait and represents an ecological adaptation to the scattered and unpredictable distribution of the preferred A. trifida host in the arid American Southwest.

Revision of the Euops quadrifasciculatus-group (Coleoptera : Curculionoidea : Attelabidae) from the Australian region, with a discussion of shifts between Nothofagus and Eucalyptus host plants

This revision of the ‘quadrifasciculatus-group’ of Euops Schoenherr contains four previously described species for which lectotypes are designated: Euops bakewelli Jekel, E. corrugatus Lea, E. insularis Voss and E. quadrifasciculatus Lea. Six species are described as new: Euops goilala, sp. nov., E. hoppla, sp. nov., E. lakekamuensis, sp. nov., E. micros, sp. nov., E. oberprieleri, sp. nov. and E. reidi, sp. nov. Detailed descriptions are provided for all species, the characters relevant for their identification are illustrated, and a key for their identification is given. The group is known from Australia, New Guinea and the Kei islands of Maluku. The record of E. insularis Voss for Aru Island is not valid. Two Australian species (E. bakewelli and E. oberprieleri) are reported from Eucalypus host plants, one Papuan species (E. lakekamuensis) is known from another myrtacean host, and for the remainder of the quadrifasciculatus-group no host data are available. The sister-group of the quadrifasciculatus-group, the pygmaeus-group of New Guinea, feeds exclusively on Nothofagus. Three different scenarios are proposed, which could have led to the observed pattern of host association; they are discussed in the light of present knowledge on phylogeny and zoogeography of Euops.

Generic Phylogeny of North American Depressariinae (Lepidoptera: Elachistidae) and Hypotheses About Coevolution

Although a considerable amount of ecological information is known about interactions between Depressaria species and their apiaceous/asteraceous host plants, this information has lacked a phylogenetic context; such a context is important in understanding the evolutionary history and phylogenetic trajectory of plant/insect interactions in general. Accordingly, we undertook an examination of the generic phylogeny of North American Depressariinae, using morphological characters of the larvae, pupae, and adults. Two different parsimony analyses yielded the same tree topology, with a consistency index over 88 and retention index between 90 and 91. This tree provided no evidence of congruent cladogenesis in this group. Host shifts between unrelated host plant families, particularly reversions to ancestral host plant groups, are abundant. Association with plants in Apiaceae and Asteraceae has apparently led to rapid speciation; the two most species-rich taxa, Depressaria Haworth and Agonopterix HA¼bner, are dominated by species that feed on these families. Because Agonopterix and Depressaria are not sister groups, the Apiaceae must have been colonized independently at least twice by Depressariinae. The best explanation for the pattern of host association seen for genera of depressariine elachistids is that of sequential colonization of related plant groups. This finding is consistent with other findings to date—that congruent cladogenesis is a phenomenon most likely to occur within genera, not at the family or subfamily level

Gall‐inducing insects provide insights into plant systematic relationships

Field surveys of cynipid gall-inducer occurrences on Quercus species were conducted in Florida, North Carolina, and Pennsylvania, USA. All cynipids demonstrated strong host species and organ fidelity. One result of this specialization is effective niche partitioning among cynipids. The host-association patterns of these specialist herbivores should reflect similarities among oaks, thus we clustered oak species according to their cynipid distributions. Cynipids distinguished small differences among their hosts. A dendrogram of oak species based on cynipid distributions was largely congruent with botanical arrangernents. Cynipid occurrences offer information helpful to resolving some aspects of oak systematics. Collaborative efforts between taxonomic botanists and entomologists will be useful in resolving a variety of plant and insect systematic problems.

HOST-PLANT SWITCHES AND THE EVOLUTION OF CHEMICAL DEFENSE AND LIFE HISTORY IN THE LEAF BEETLE GENUS OREINA.

Insect-plant interactions have played a prominent role in investigating phylogenetic constraints in the evolution of ecological traits. The patterns of host association among specialized insects have often been described as highly conservative, yet not all specialized herbivorous insect lineages display the same degree of fidelity to their host plants. In this paper, we present an estimate of the evolutionary history of the leaf beetle genus Oreina. This genus displays an amazing flexibility in several aspects of its ecology and life history: (1) host plant switches in Oreina occurred between plant families or distantly related tribes within families and thereby to more distantly related plants than in several model systems that have contributed to the idea of parallel cladogenesis; (2) all species of the genus are chemically defended, but within the genus a transition between autogenous production of defensive toxins and sequestration of secondary plant compounds has occurred; and (3) reproductive strategies in the genus range from oviparity to viviparity including all intermediates that could allow the gradual evolution of viviparity. Cladistic analysis of 18 allozyme loci found two most parsimonious trees that differ only in the branching of one species. According to this phylogeny estimate, Oreina species were originally associated with Asteraceae, with an inclusion of Apiaceae in the diet of one oligophagous species and an independent switch to Apiaceae in a derived clade. The original mode of defense appears to be the autogenous production of cardenolides as previously postulated; the additional sequestration of pyrrolizidine alkaloids could have either originated at the base of the genus or have arisen three times independently in all species that switched to plants containing these compounds. Viviparity apparently evolved twice in the genus, once without matrotrophy, through a retention of the eggs inside the female's oviducts, and once in combination with matrotrophy. We hypothesize that the combination of autogenous defense and a life history that involves mobile externally feeding larvae allowed these beetles to switch host plants more readily than has been reported for highly conservative systems.

Evolution of Ticks

Evolutionary patterns in ticks have traditionally been cast in terms of host associations. Largely untested assumptions of cospeciation and observations of current host associations are used to estimate the age of different taxa. Several recent phylogenetic studies of supraspecific relationships in ticks, based on both morphological and DNA-sequence data, allow the first rigorous testing of these assumptions. Reanalysis of patterns of tick-host associations suggests that the perception of host specificity in ticks may be an artifact of incomplete sampling. An analysis of tick-host and -habitat associations and biogeographical patterns, in the context of the newly derived phylogenies, suggests that much of the existing host-association patterns may be explained as artifacts of biogeography and ecological specificity.

Evolution of Ticks

Evolutionary patterns in ticks have traditionally been cast in terms of host associations. Largely untested assumptions of cospeciation and observations of current host associations are used to estimate the age of different taxa. Several recent phylogenetic studies of supraspecific relationships in ticks, based on both morphological and DNA-sequence data, allow the first rigorous testing of these assumptions. Reanalysis of patterns of tick-host associations suggests that the perception of host specificity in ticks may be an artifact of incomplete sampling. An analysis of tick-host and -habitat associations and biogeographical patterns, in the context of the newly derived phylogenies, suggests that much of the existing host-association patterns may be explained as artifacts of biogeography and ecological specificity.

Lithinine moths on ferns: a phylogenetic study of insect-plant interactions

We examine host association patterns in pteridophagous moths of the tribe Lithinini (Lepidoptera: Geometridae). This represents the first study where the host associations of oligophagous, pteridophagous Lepidoptera are analysed in a phylogenetic context. We compare the observed phylogenetic patterns of lithinine moths and their hosts with the contrasting coevolutionary scenarios proposed by Mitter et ai, and discuss the support for various hypotheses relative to Thompson's concept of coevolution as ‘escape with radiation’, and the chemical facilitation model of Jermy. The patterns observed support a scenario where host shifting subsequent to a single colonization event has resulted in lack of strict concordance (i.e. parallel cladogenesis) between moth and fern phylogenies.

Are ant-aphid associations a tritrophic interaction? Oleander aphids and Argentine ants.

Oleander aphids, (Aphis nerii), which are sporadically tended by ants, were used as a moded system to examine whether host plant factors associated with feeding site influenced the formation of ant-aphid associations. Seasonal patterns of host plant utilization and association with attendant ants were examined through bi-weekly censuses of the aphid population feeding on thirty ornamental oleander plands (Nerium oleander) in northern California in 1985 and 1986. Colonies occurred on both developing and senescing plant terminals, including leaf tips, floral structures, and pods. Aphids preferentially colonized leaf terminals early in the season, but showed no preference for feeding site during later periods. Argentine ants (Iridomyrmex humilis) occasionally tended aphid colonies. Colonies on floral tips were three to four times more likely to attract ants than colonies on leaf tips, even though the latter frequently contained more aphids. Ants showed a positive recruitment response to colonies on floral tips, with a significant correlation between colony size and number of ants. There was no recruitment response to colonies on leaf tips. These patterns were reproducible over two years despite large fluctuations in both aphid population density and ant activity. In a laboratory bioassay of aphid palatability, the generalist predator,Hippodamia convergens, took significantly more aphids reared on floral tips compared to those reared on leaf tips. The patterns reported here support the hypothesis that tritrophic factors may be important in modifying higher level arthropod mutualisms.

HOST-PLANT RELATIONSHIPS IN THE PAPILIONIDAE (LEPIDOPTERA): PARALLEL CLADOGENESIS OR COLONIZATION?

Abstract- Stepwise coevolution, as defined by Ehrlich and Raven (1964) and others, can be equated with parallel cladogenesis or association by descent (Mitter and Brooks, 1983). I review the insect/plant literature and discuss recent cladistic findings for the Papilionidae, and compare two contrasting theories: 1) that insect/host associations have evolved through parallel cladogenesis; or 2) that insects have 'colonized' their hosts subsequent to plant cladogenesis. I conclude that no documented examples of parallel cladogenesis between insects and plants are known. The swallowtail cladograms instead offer evidence in support of the second theory. They suggest that host association patterns in the Papilionidae have resulted from repeated colonization of plants belonging to a relatively small number of families. I discuss data which indicate that plant secondary chemicals have been important 'barriers' to colonization (sensu Ehrlich and Raven, 1964), and have in large part mediated host switching in the Papilionidae.