Biology subjects

Ali, J. G.

Publications and source records attributed to Ali, J. G..

3 recordsLinked to original sources

bioRxiv2026

Phyllosphere bacterial communities in milkweeds: composition diverge as the season progresses, and links to cardenolides and arthropods depend on host identity

Leaf bacterial communities shape plant defense and interactions with herbivores, yet how host filtering and stochastic processes assemble them remains unclear. We predicted that host identity, chemistry, and arthropods structure them, and that stochastic and deterministic contributions shift seasonally. Across one growing season we sampled leaf bacteria monthly and arthropods weekly on four Asclepias species (Apocynaceae: A. curassavica, A. incarnata, A. syriaca, A. tuberosa) spanning a cardenolide gradient. We sequenced 16S rRNA genes and quantified selection and dispersal contributions to turnover using null models. Host identity shaped bacterial richness and composition, with A. tuberosa hosting the richest communities, and both richness and phylogenetic diversity rose through the season. Early on, homogenizing dispersal made communities more similar among plants; by mid-season no single process dominated turnover, and by late season dispersal limitation prevailed. Homogeneous selection was episodic, not sustained, and arthropod associations were host-specific, negatively so on A. syriaca. Phyllosphere assembly thus shifts from convergence to divergence in one season: young leaves recruit from a shared pool delivered by wind, rain, and arthropods, whereas exchange among ageing plants declines and communities drift apart. Herbivores arriving late meet plant-specific microbial environments, so microbial mediation of herbivory should be host-specific and seasonally contingent.

ecology↗

bioRxiv2026

Drought disrupts volatile-mediated predator foraging and oviposition, weakening trait-mediated top-down control

O_LIDrought is a major abiotic stressor that can restructure trophic interactions by limiting herbivore success and disrupting chemical signaling between plants and natural enemies. In tritrophic systems, plant volatiles guide natural enemy foraging and reproductive investment, often scaling with herbivore density; however, it is unclear whether drought alters this relationship and weakens top-down control. C_LIO_LIUsing a tomato-aphid-ladybeetle system, we tested how drought and herbivore density jointly affect plant VOC emissions, predator behavior, and aphid dynamics. We manipulated water availability (well-watered vs. drought) and aphid density (low vs. high), and measured plant physiology, volatile profiles, predator visitation and oviposition, and aphid responses. C_LIO_LIDrought reduced stomatal conductance, plant biomass, and both total and compositional output of VOCs. Emission of key predator-attracting compounds (e.g., methyl salicylate, {beta}-myrcene) peaked in well-watered, high-density plants but was suppressed under drought. C_LIO_LILadybeetle visitation increased with aphid density but declined under drought, reflecting conserved shifts in volatile cues. Oviposition was concentrated on well-watered, high-density plants and associated with specific compounds (e.g., methyl salicylate, carvacrol), while others (e.g., cymene-7-ol, para, 1-octanol) were negatively associated. C_LIO_LIAphid suppression by predators occurred only under well-watered, high-density conditions. Under drought, aphid growth was already constrained, and predators had little additional effect on their abundance. However, both drought and predator presence influenced aphid demography, increasing production of dispersive alates. C_LIO_LIThese findings underscore the sensitivity of chemically mediated trophic interactions to environmental stress. Increased drought disrupts plant signaling, reducing natural enemy effectiveness, weakening biocontrol, and shifting herbivore population structure. Understanding how stress alters cue reliability is key to predicting community dynamics and managing ecosystem functions under stress. C_LI

ecology↗

bioRxiv2026

Domestication drives changes in floral functional traits that impact generalist pollinator visitation

Crop domestication is an evolutionary process that has led to extraordinary plant phenotypic changes in response to artificial selection. The extent to which domestication has altered floral phenotypes and the implications of these changes for plant-pollinator interactions remain unclear. Here, we characterized the floral phenotypes of wild and domesticated species in the genus Cucurbita (squash and pumpkins) and quantified their relative attractiveness to generalist and specialist pollinators. Our results show that functional floral traits change with domestication and that some of these changes impact the visitation of generalist pollinators but not specialists. Crops displayed larger flowers with shorter anthers and wider corollas, lower volatile richness, higher sugar content in pollen, and lower sucrose:glucose ratios in nectar. These trait shifts were associated with pollinator behavior in generalist pollinators, which preferentially visited domesticated flowers. We demonstrate that domestication alters functional plant traits and that these changes affect generalist pollinator preference in agricultural settings.

ecology↗