Biology subjects

Hendry, T. A.

Publications and source records attributed to Hendry, T. A..

7 recordsLinked to original sources

bioRxiv2026

Natural enemies mediate the impact of plant microbiota on insect-borne virus transmission

Individual hosts can be protected from disease vectors through their microbiota, but how those benefits scale up to the host population level is rarely obvious. Disease spread may be inhibited through reduced vector visitation or amplified as vectors redirect their attention to unprotected hosts. The outcome--suppression or escalation of disease outbreaks--is likely to be influenced by natural enemies that redistribute or suppress vector populations. The challenge of determining how these processes interact across scales is exemplified by pea aphids, major virus vectors in pea crops that are commonly managed using parasitoid wasps. Recent evidence suggests that epiphytic bacteria in the genus Pseudomonas can repel or kill pea aphids, yet whether Pseudomonas-mediated protection from aphids complements or undermines parasitoid-based vector control remains unknown. We developed a multi-scale mathematical model to investigate why Pseudomonas complements versus undermines biocontrol of aphid-vectored virus outbreaks. Because Pseudomonas-induced mortality leaves aphids patchily distributed, the effect of Pseudomonas on virus outbreaks depends most strongly on how well parasitoids track aphid densities: When parasitoids efficiently locate aphids, Pseudomonas inhibits virus outbreaks by reducing aphid densities. However, when parasitoids are less efficient, they often search unproductively for aphids on Pseudomonas-inhabited plants with few aphids, slowing parasitoid population growth. Reduced parasitism intensifies aphid crowding on Pseudomonas-free plants and boosts the production of winged aphids that accelerate viral spread. Counterintuitively, the more effective Pseudomonas is at killing aphids, the more strongly it generates spatial variability and promotes virus spread. Our results show how community context dictates whether individual microbiota protection slows or accelerates viral outbreaks at the population scale.

ecology↗

bioRxiv2024

Common fluorescent Pseudomonas in the phyllosphere can influence aphid behavior in diverse ways

Bacteria in the phyllosphere, the above ground parts of plants, can have complex interactions with plants and their insect visitors. For instance, certain Pseudomonas strains change pea aphid (Acyrthosiphon pisum) feeding behavior. Aphids visually detect and avoid feeding when Pseudomonas produces a compound with blue fluorescent emissions, the siderophore pyoverdine. It is unknown how commonly such interactions occur in nature, so we investigated this potential in pea plant (Pisum sativum) phyllosphere communities. We found a diversity of Pseudomonas taxa with fluorescent potential in pea plant microbiomes. Culture isolates revealed a wide range of fluorescent emissions spectra across taxa, which produced blue to green fluorescence of varying intensities. We tested strains from across this emissions range for pea aphid behavioral responses when given a choice between plants inoculated with a fluorescent isolate or a control treatment. Consistent with previous work, we found that some isolates were avoided by aphids. Surprisingly, some isolates were actually attractive to aphids, causing up to 70% of aphids to settle and feed on bacterially treated plants. Attractive isolates produced green fluorescence in culture, suggesting that attraction could be due to aphid sensory biases. Overall, we found both isolate fluorescence in culture and siderophore potential inferred from gene content to be poor predictors of aphid behavior. We also found very high variability in responses across replicate experiments for some strains, suggesting that environmental conditions may influence outcomes. This shows that bacterial fluorescence may be common on plants and can have context-dependent impacts on herbivorous insects.

ecology↗

bioRxiv2024

Increased host diversity limits bacterial generalism but may promote microbe-microbe interactions

Host-associated bacteria vary in their host breadth, which can impact ecological interactions. By colonizing diverse hosts, host generalists can have disproportionate ecological impacts. For bacteria, host generalism may advantageous, particularly when the availability of specific hosts is variable. It is unclear how much the ability to evolve generalism, by inhabiting diverse hosts, is constrained in host-associated bacteria. We hypothesized that constraints on bacterial generalism will differ depending on the availability of specific host species. To test this, we assessed patterns of diversity and specialization in the cloacal microbiomes of reptile communities from the temperate zone to the tropics, where the diversity and abundance of host species varies substantially. Within these communities, generalist taxa tended to be Proteobacteria, whereas specialists tended to be Firmicutes. We found that bacterial generalists were less prevalent in the highest diversity host communities, and in keeping with this, Proteobacteria were less diverse in these communities. Generalist taxa became relatively less widespread across host species only in the two most diverse host communities. We therefore conclude that the constraint on generalism is not driven by absolute incompatibility with some host species, but rather from competition with host adapted specialist lineages. In the high-diversity communities, we found that the successful generalists, typically Proteobacteria, were disproportionately likely to co-occur with one another across evolutionarily disparate hosts within the community. Our data indicate that bacterial lineages can adapt to the evolutionary pressures of high diversity host communities either by specializing on hosts or by forming cohorts of co-occurring bacterial lineages.

ecology↗

bioRxiv2023

Genome evolution following an ecological shift in nectar-dwelling Acinetobacter

The bacterial genus Acinetobacter includes species found in environmental habitats like soil and water, as well as species adapted to be host-associated or pathogenic. High genetic diversity may allow for this habitat flexibility, but the specific genes underlying switches between habitats are poorly understood. One lineage of Acinetobacter has undergone a substantial habitat change by evolving from a presumed soil-dwelling ancestral state to thrive in floral nectar. Here we compared the genomes of floral-dwelling and pollinator-associated Acinetobacter, including newly described species, with genomes from relatives found in other environments to determine the genomic changes associated with this ecological shift. Following one evolutionary origin of floral nectar adaptation, nectar-dwelling Acinetobacter species have undergone reduction in genome size compared to relatives and have experienced dynamic gene gains and losses as they diversified. We found changes in gene content underlying carbohydrate metabolism and nitrogen metabolism, which we predict to be beneficial in nectar environments. Gene losses follow a pattern consistent with genome streamlining, whereas gains appear to result from both evolutionary divergence and horizontal gene transfer. Most notably, nectar-dwelling Acinetobacter acquired the ability to degrade pectin from plant pathogens and the genes underlying this ability have duplicated and are under selection within the clade. We hypothesize that this ability was a key trait for adaptation to floral nectar, as it could improve access to nutrients in the nutritionally unbalanced habitat of nectar. These results identify the genomic changes and traits coinciding with a dramatic habitat switch from soil to floral nectar.

microbiology↗

bioRxiv2022

Changes in capture availability due to infection can lead to correctable biases in population-level infectious disease parameters

Correctly identifying the strength of selection parasites impose on hosts is key to predicting epidemiological and evolutionary outcomes. However, behavioral changes due to infection can alter the capture probability of infected hosts and thereby make selection difficult to estimate by standard sampling techniques. Mark-recapture approaches, which allow researchers to determine if some groups in a population are less likely to be captured than others, can mitigate this concern. We use an individual-based simulation platform to test whether changes in capture rate due to infection can alter estimates of three key outcomes: 1) reduction in offspring numbers of infected parents, 2) the relative risk of infection for susceptible genotypes compared to resistant genotypes, and 3) change in allele frequencies between generations. We find that calculating capture probabilities using mark-recapture statistics can correctly identify biased relative risk calculations. For detecting fitness impact, the bounded nature of the distribution possible offspring numbers results in consistent underestimation of the impact of parasites on reproductive success. Researchers can mitigate many of the potential biases associated with behavioral changes due to infection by using mark-recapture techniques to calculate capture probabilities and by accounting for the shapes of the distributions they are attempting to measure.

ecology↗

bioRxiv2019

Plumage manipulation alters the integration of social behavior, physiology, internal microbiome, and fitness.

Signals often covary with physiological and behavioral traits to form an axis of integrated phenotypic variation associated with reproductive performance. This pattern of phenotypic integration could result from intrinsic between-individual differences that are causally related to signal production, physiology, and behavior. Alternatively, signal expression itself might generate dynamic feedback between physiology, behavior, and the experienced social environment, resulting in an integrated phenotype. Here, we manipulated the plumage of female tree swallows (Tachycineta bicolor) to decouple the expression of a social signal from any pre-existing behavioral or physiological differences. We collected a time series of physiological samples, monitored social interactions with a sensor network, and tracked reproductive performance. Relative to sham controls, dulled females experienced an altered social environment; overall, these females were visited more by conspecific females and less by males. Dulled females subsequently changed their own behavior by initiating fewer interactions and increasing nestling provisioning. These differences resulted in an altered internal microbiome and glucose levels and, ultimately, dulled females produced more offspring. Moreover, dulled females produced larger clutches than control females in the year after the manipulation. Thus, signal variation alone--independent from any pre-existing differences--had a sustained causal affect on a suite of integrated traits. This finding suggests that dynamic feedback may play an important role in coordinating an integrated signaling phenotype. Our results have implications for understanding how variation in signal expression arises and is maintained and the extent to which the information encoded in signals is contingent upon their use in a social environment.

zoology↗

bioRxiv2019

Insects as phyllosphere microbiome engineers: effects of aphids on a plant pathogen.

Insect herbivores are common in the phyllosphere, the above-ground parts of plants, and encounter diverse plant-associated bacteria there, yet how these organisms interact remains largely unknown. Strains of the bacterium Pseudomonas syringae grow well epiphytically and have been shown to grow within and kill hemipteran insects like the pea aphid, Acyrthosiphon pisum. Aphids are hypothesized to be an alternative host for these epiphytic bacteria but it is unclear if aphids provide fitness benefits to these bacterial pathogens. To determine if epiphytic bacteria could be adapted for infecting aphids, we characterized 21 strains of P. syringae for epiphytic ability and virulence to pea aphids and found that the two traits were positively correlated. For a subset of strains, we tested if the bacteria derived a fitness benefit from the presence of aphids. Some strains benefited significantly, with up to 18.9% higher population densities when aphids were present, and lower starting population density was predictive of higher benefit from aphid presence. However, further investigation found that honeydew, the sugary waste product of aphids, and not growth in aphids, increased P. syringae growth on leaves. This suggests that aphids may be important microbiome engineers in the phyllosphere, but evolutionarily dead-ends for epiphytic bacteria.

evolutionary biology↗