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opencc-zeroDec 2022View details →

Data from: A well-studied parasitoid fly of field crickets uses multiple alternative hosts in its introduced range

Organisms and their natural enemies can have dynamic coevolutionary trajectories, but anthropogenic effects like species introductions interrupt existing coevolutionary relationships. For parasites in particular, if they are introduced to a location without their hosts, they can only persist in the new environment if alternative hosts are 1) present, 2) detectable to parasites, and 3) capable of sustaining parasites. The circumstances surrounding the addition of alternative hosts to a parasite's repertoire are rarely observed. The parasitoid fly Ormia ochracea locates its field cricket hosts by orienting acoustically to their conspicuous mating songs. In Hawaii, O. ochracea is only known to parasitize one species, Teleogryllus oceanicus, but rapid evolution of T. oceanicus mating song over the past 20 years has led to several prevalent morphs of the cricket that produce no song or novel songs that the flies cannot detect. Yet flies persist in populations that lack ancestral singing T. oceanicus, prompting us to investigate the possibility of alternative hosts in Hawaii. We demonstrate first that three potential alternative hosts (Gryllodes sigillatus, Gryllus bimaculatus, and Modicogryllus pacificus) are present. Second, O. ochracea exhibits a positive phonotactic response to all three species' songs in the field and in the lab. And third, O. ochracea can successfully develop to pupae and emerge as adults in all three species. Our discovery of alternative hosts for O. ochracea in Hawaii infuses the system with intriguing complexity and offers extensive opportunities for future work.

opencc-zeroSep 2023View details →

Host-enemy interactions provide limited biotic resistance for a range-expanding species via reduced apparent competition

Aim: As species' ranges shift poleward in response to anthropogenic change, they may lose antagonistic interactions if they move into less diverse communities, fail to interact with novel populations or species effectively, or if ancestral interacting populations or species fail to shift synchronously. We leveraged a poleward range expansion in a tractable insect host-enemy community to uncover mechanisms by which altered antagonistic interactions between native and recipient communities contributed to "high niche opportunities" (limited biotic resistance) for a range-expanding insect. Location: North America, Pacific Northwest Methods: We created quantitative insect host-enemy interaction networks by sampling oak gall wasps on 400 trees of a dominant oak species in the native and expanded range of a range-expanding gall wasp species. We compared host-enemy network structure between regions. We measured traits (phenology, morphology) of galls and interacting parasitoids, predicting greater trait divergence in the expanded range. We measured function relating to host control and explored if altered interactions and traits contributed to reduced function or biotic resistance. Results: Interaction networks had fewer species in the expanded range and lower complementarity of parasitoid assemblages among host species. While networks were more generalized, interactions with the range-expanding species were more specialized in the expanded range. Specialist enemies effectively tracked the range-expanding host, and there was reduced apparent competition with co-occurring hosts by shared generalist enemies. Phenological divergence of enemy assemblages interacting with the range-expanding and co-occurring hosts was greater in the expanded range, potentially contributing to weak apparent competition. Biotic resistance was lower in the expanded range, where fewer parasitoids emerged from galls of the range-expanding host. Main conclusions: Changes in interactions with generalist enemies created high niche opportunities, and limited biotic resistance, suggesting weak apparent competition may be a mechanism of enemy release for range-expanding insects embedded within generalist enemy networks.

publicJan 2025View details →

Data from: The role of host-range expansion and co-speciation in host-parasite associations with the divergence of the great tit species complex

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publicDec 2022View details →

Data from: A well-studied parasitoid fly of field crickets uses multiple alternative hosts in its introduced range

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publicNov 2024View details →

Rapid evolution of host repertoire and geographic range in a young and diverse genus of montane butterflies

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publicSep 2023View details →

Host-enemy interactions provide limited biotic resistance for a range-expanding species via reduced apparent competition

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opencc-zeroJul 2020View details →

Data from: Tradeoffs with growth limit host range in complex life cycle helminths

Parasitic worms with complex life cycles have several developmental stages, with each stage creating opportunities to infect additional host species. Using a dataset for 973 species of trophically transmitted acanthocephalans, cestodes, and nematodes, we confirmed that worms with longer life cycles (i.e. more successive hosts) infect a greater diversity of host species and taxa (after controlling for study effort). Generalism at the stage level was highest for 'middle' life stages, the second and third intermediate hosts of long life cycles. By simulating life cycles in real food webs, we found that middle stages had more potential host species to infect, suggesting that opportunity constrains generalism. However, parasites usually infected fewer host species than expected from simulated cycles, suggesting generalism also has costs. There was no tradeoff in generalism from one stage to the next, but worms spent less time growing and developing in stages where they infected more taxonomically diverse hosts. Our results demonstrate that life cycle complexity favors high generalism, and host use across life stages is determined by both ecological opportunity and life history tradeoffs.

opencc-zeroFeb 2020View details →

Data from: The evolution of parasite host range in heterogeneous host populations

Theory on the evolution of niche width argues that resource heterogeneity selects for niche breadth. For parasites, this theory predicts that parasite populations will evolve, or maintain, broader host ranges when selected in genetically diverse host populations relative to homogeneous host populations. To test this prediction, we selected the bacterial parasite Serratia marcescens to kill Caenorhabditis elegans in populations that were genetically heterogeneous (50% mix of two experimental genotypes) or homogeneous (100% of either genotype). After 20 rounds of selection, we compared the host range of selected parasites by measuring parasite fitness (i.e. virulence, the selected fitness trait) on the two focal host genotypes and on a novel host genotype. As predicted, heterogeneous host populations selected for parasites with a broader host range: these parasite populations gained or maintained virulence on all host genotypes. This result contrasted with selection in homogeneous populations of one host genotype. Here, host range contracted, with parasite populations gaining virulence on the focal host genotype and losing virulence on the novel host genotype. This pattern was not, however, repeated with selection in homogeneous populations of the second host genotype: these parasite populations did not gain virulence on the focal host genotype, nor did they lose virulence on the novel host genotype. Our results indicate that host heterogeneity can maintain broader host ranges in parasite populations. Individual host genotypes, however, vary in the degree to which they select for specialization in parasite populations.

opencc-zeroSep 2020View details →

Cuscuta sect. Californicae (Convolvulaceae) revisited: 'cryptic' speciation and host range differentiation

Cuscuta californica complex (sensu lato, s.l.) is a western North American group of species in which the infrastaminal scales are reduced, making the morphological delimitation of species particularly challenging. A revision of this group was prompted by the discovery of an apparent new species from central California based primarily on molecular means. Prompted by this finding, the morphological limits of C. californica s.l. species were comprehensively re-evaluated through a morphometric study. DNA sequences from plastid (trnL–F region and rbcL), nuclear ribosomal ITS and 26S rDNA, as well as a low-copy nuclear pentatricopeptide repeat (PPR) gene were used to reconstruct evolutionary relationships among taxa. Last but not least, the host range of relevant taxa was determined using herbarium specimens. Molecular results strongly supported the new species, C. difficilis, which was found to be morphologically separated from C. brachycalyx only by subtle calyx lobe and corolla tube shape differences. Despite sharing some of the hosts, all the members of C. californica s.l. exhibited a differentiation of their host ranges. An identification key and description of the new species were provided together with a discussion on the systematics and host range of C. californica s.l.. Hybridization, accompanied by plastid capture, was suggested as a possible mechanism of speciation for C. brachycalyx.

opencc-zeroDec 2017View details →

Data from: Is there a disease-free halo at species range limits? The co-distribution of anther-smut disease and its host species

1. While disease is widely recognized as affecting host population size, it has rarely been considered to play a role in determining host range limits. Many diseases may not be able to persist near the range limit if host population density falls below the critical threshold level for pathogen invasion. However, in vector- and sexually-transmitted diseases, pathogen transmission may be largely independent of host density and theory demonstrates that diseases with frequency-dependent transmission may persist in small populations near the range limit. 2. Empirical studies of disease at species range limits have lagged behind the theory, and to date, no previous study has tested the hypothesis that vector or sexually transmitted diseases can be maintained at host range limits. 3. We studied the distribution of anther-smut disease, a sterilizing pollinator-transmitted disease, on four alpine plant species to determine whether disease was present at the host range limits. 4. We found that host abundance declined towards the elevational range limits, and disease extended to the most extreme elevational range limits in three of the four host species. Maximum likelihood estimation of the magnitude of the disease-free halo showed that it was small or non-existent for all host species. Moreover, disease prevalence within populations was often higher nearer the host's range limit than in the range center and was independent of host density. 5. Synthesis: Our results show that diseases where transmission is frequency-dependent have the potential to affect host distributions not just in theory, but also in real world populations.

opencc-zeroDec 2023View details →

Impact of climate on a host-hyperparasite interaction on Arabica coffee in its native range

Natural enemies of plant pathogens might play an important role in controlling plant disease levels in natural and agricultural systems. Yet, plant pathogen-natural enemy interactions might be sensitive to climatic changes. Understanding the relationship between climate, plant pathogens, and their natural enemies is thus important for developing climate-resilient, sustainable agriculture. To this aim, we recorded shade cover, daily minimum and maximum temperature, relative humidity, coffee leaf rust, and its hyperparasite at 58 sites in southwestern Ethiopia during the dry and wet season for two years. Coffee leaf rust severity was positively related to the maximum temperature. Hyperparasite severity was higher when the minimum temperature was low (i.e. in places with cold night temperatures). While canopy cover did not have a direct effect on rust severity, it reduced rust severity indirectly by lowering the maximum temperature. Canopy cover had a direct positive effect on the hyperparasite severity during one surveying period. Synthesis and applications. Our findings highlight that coffee leaf rust and its hyperparasite are both affected by shade cover and temperature, but in different ways. On the one hand, these niche differences lead to the worrying prediction that levels of coffee leaf rust will increase, and its hyperparasite will decrease, with climate change. On the other hand, these niche differences between coffee leaf rust and its hyperparasite provide opportunities to develop strategies to manage the environment (such as shade cover and microclimate) in such a way that the rust is disfavored and the hyperparasite is favored.

opencc-zeroJan 2024View details →

High-resolution environmental and host-related factors impacting questing Ixodes scapularis at their northern range edge

The geographic range of tick populations has expanded in Canada due to climate warming and the associated poleward range shifts of their vertebrate hosts. Abiotic factors, such as temperature, precipitation, and snow, are known to directly affect tick abundance. Yet, biotic factors, such as the abundance and diversity of mammal hosts, may also alter tick abundance and consequent tick-borne disease risk. Here, we incorporated host surveillance data with high-resolution environmental data to evaluate the combined impact of abiotic and biotic factors on questing Ixodes scapularis abundance in Ontario and Quebec, Canada. High-resolution abiotic factors were derived from remote sensing satellites and meteorological towers, while biotic factors related to mammal hosts were derived from active surveillance data that we collected in the field. Generalized additive models were used to determine the relative importance of abiotic and biotic factors on questing I. scapularis abundance. Combinations of abiotic and biotic factors were identified as important drivers of abundances of questing I. scapularis. Positive and negative linear relationships were found for questing I. scapularis abundance with precipitation and accumulated snow, but no effect was found for the relative abundance of white-footed mice. Positive relationships were also identified between questing I. scapularis abundance with monthly mean precipitation and mammal species richness. Therefore, future studies that assess I. scapularis should incorporate host surveillance data with high-resolution environmental factors to determine the key drivers impacting the abundance and geographic spread of tick populations and tick-borne pathogens.

opencc-by-4.0Feb 2022View details →

Physiological host range of three Trissolcus parasitoids in New Zealand

This archive contains a 'data' folder holding an Excel workbook with the results of no-choice oviposition experiments conducted with Trissolcus basalis (Wollaston) & Trissolcus oenone (Dodd) (Scelionidae: Hymenoptera) and New Zealand species of Pentatomidae. Trissolcus basalis is a biological control agent released in New Zealand in 1949 against Nezara viridula L., and Trissolcus oenone is a native parasitoid also present in Australia. This is the first time the physiological host ranges of each parasitoid have been established quantitatively in New Zealand, and for Trissolcus basalis, this study provides a retrospective view of its physiological host range after 80 years in the country. This workbook also contains a second sheet holding a combined dataset - a combination of results from the previously mentioned study and those from: "Experimental assessment of the biosafety of Trissolcus japonicus in New Zealand, prior to the anticipated arrival of the invasive pest Halyomorpha halys" (DOI: 10.1007/s10526-019-09949-x). The archive also contains a 'src' folder containing an R markdown file with the R code used to perform analyses.

opencc-zeroJun 2022View details →

Cross-continental comparison of parasite communities in a wide-ranging carnivore suggests associations with prey diversity and host density

Parasites are integral to ecosystem functioning yet often overlooked. Improved understanding of host-parasite associations is important, particularly for wide-ranging species for which host range shifts and climate change could alter host-parasite interactions and their effects on ecosystem function. Among the most widely distributed mammals with diverse diets, grey wolves (Canis lupus) host parasites that are transmitted among canids and via prey species. Grey wolf-parasite associations may therefore influence the population dynamics and ecological functions of both wolves and their prey. Our goal was to identify large-scale processes that shape host-parasite interactions across populations, with the grey wolf as a model organism. By compiling data from various studies, we examined the faecal prevalence of gastrointestinal parasites in six wolf populations from two continents in relation to wolf density, diet diversity, and other ecological conditions. As expected, we found that the faecal prevalence of parasites transmitted directly to wolves via contact with other canids or their excreta was positively associated with wolf density. Contrary to our expectations, the faecal prevalence of parasites transmitted via prey was negatively associated with prey diversity. We also found that parasite communities reflected landscape characteristics and specific prey items available to wolves. Several parasite taxa identified in this study, including hookworms and coccidian protozoans, can cause morbidity and mortality in canids, especially in pups, or in combination with other stressors. The density-prevalence relationship for parasites with simple lifecycles may reflect a regulatory role of gastrointestinal parasites on wolf populations. Our result that faecal prevalence of parasites was lower in wolves with more diverse diets could provide insight into the mechanisms by which biodiversity may regulate disease. A diverse suite of predator-prey interactions could regulate the effects of parasitism on prey populations and mitigate the transmission of infectious agents, including zoonoses, spread via trophic interactions.

opencc-by-4.0Nov 2018View details →

Fig. 4 in A study of Cactoblastis cactorum (Lepidoptera: Pyralidae) in its native range: further insights into life cycle, larval identification, developmental parameters, natural enemies, and damage to the host plant Opuntia ficus-indica (Caryophyllales: Cactaceae)

Fig. 4. Number of eggs across months for all sampling sites from Tucumán.

opencc-by-4.0Jul 2024View details →

Fusarium Genomes and their Host Ranges

This Appendix dataset accompanies a review of Fusarium genomes and their respective host ranges, entitled 'Navigating the Fusarium species complex: Host-Range Plasticity and Genome Variations', published in Fungal Biology (https://doi.org/10.1016/j.funbio.2024.07.004). The information within this dataset was correct as of March 2024 and includes information on Species, NCBI identifier, Assigned Phylogenetic Clade, The number of genomes available on NCBI, Ungapped Genome Size, Number of Chromosomes, Number of Core and Lineage Specific (LS) Chromosomes (by karyotyping), the Sequencing Methodology and Source. It also includes an extensive, but not universal, curation of known host ranges for each species. It is our hope that by making this dataset freely available it will encourage and inspire further research into the Fusarium genus.

opencc-by-4.0May 2021View details →

Figure 1 in New adult host records for three Buprestidae (Coleoptera) rarely encountered in the United States and significant extension of the known geographic range of Agrilus pilosicollis Fisher

Figure 1. Agrilus langei Obenberger ♂. a) Dorsal view. b) Ventral view. c) Lat-