Biology subjects

Oersted, M.

Publications and source records attributed to Oersted, M..

3 recordsLinked to original sources

bioRxiv2024

Endosymbionts impact ladybird predation rates of aphids in a temperature-dependent manner

Aphids are worldwide pests causing major economic losses to growers. Current management strategies rely heavily on pesticides, but some effective pesticides are being withdrawn and the efficiency of remaining pesticides is also decreasing as aphids build up resistance. Biological control using predators can provide a sustainable alternative to pesticides under some circumstances, while the deliberate introduction of facultative bacterial endosymbionts that induce host fitness costs and reduce plant virus transmission provides another potential future strategy to combat aphid pests. However, new control options should not be antagonistic, with the concern that the effectiveness of biocontrol might be altered by endosymbiont presence in hosts. We, therefore, tested if predation by two aphidophagous ladybirds, Adalia bipunctata and Harmonia conformis, on the green peach aphid, Myzus persicae, and the oat aphid, Rhopalosiphum padi, was affected by transinfected Rickettsiella viridis and both native and transinfected Regiella insecticola endosymbionts at different temperatures. The predation rate of aphids infected by either endosymbiont was higher at 14 {degrees} C than the rate for uninfected aphids of both species, but the opposite pattern was apparent at 20 {degrees}C and for one host-endosymbiont combination at 26 {degrees}C. Overall, the results showed that higher temperatures increased predation, while differences between intermediate and low temperatures were species-dependent. No transmission of endosymbionts from aphid to ladybird through predation was detected. These findings point to a lack of consistent effects of the investigated endosymbionts on predation rates in these major aphid pests. The temperature dependence of endosymbiont-predation interactions suggests that the impact of seasonal climate should be considered when assessing the potential of endosymbionts in a biological control setting. HIGHLIGHTS- Aphid endosymbiont effects on ladybird predation rates are temperature-dependent - Ladybird predation rate of aphids increases as temperature rises - Prey (aphid) endosymbionts are not transferred to predators (ladybirds)

ecology↗

bioRxiv2024

Application of the thermal death time model in predicting thermal damage accumulation in plants

O_LIThe thermal death time (TDT) model suggests that the duration an organism can tolerate thermal stress decreases exponentially as the intensity of the temperature becomes more extreme. This model has been used to predict damage accumulation in ectotherm animals and plants under fluctuating thermal conditions. However, the critical assumption of the TDT model, which is additive damage accumulation, remains unverified for plants. C_LIO_LIWe assessed thermal damage in Thymus vulgaris under different heat and cold treatments and used TDT models to predict time to thermal failure of PSII. Additionally, thermal tolerance estimates from previous studies were used to create TDT models to assess the applicability of this framework in plants. C_LIO_LIWe show that thermal damage obtained at different stress intensities and durations is additive for both heat and cold stress, and that the TDT model can predict damage accumulation at both temperature extremes. Data from previous studies indicate a broad applicability of this approach across species, traits, and environments. C_LIO_LIThe TDT framework reveals a thermal tolerance landscape describing the exponential relationship between exposure duration, stress intensity and damage accumulation in plants. This thermal sensitivity emphasizes the potential impact of future thermal extremes on the mortality and distribution of plant species. C_LI HighlightThis study highlights the applicability of the thermal death time model to plants, unveiling a distinct thermal tolerance landscape, extending across species and traits for assessing thermal stress impacts.

plant biology↗

bioRxiv2021

Population bottlenecks constrain microbiome diversity and host genetic variation impeding fitness

It is becoming increasingly clear that microbial symbionts influence key aspects of their hosts fitness, and vice versa. This may fundamentally change our thinking about how microbes and hosts interact in influencing fitness and adaptation to changing environments. Here we explore how reductions in population size commonly experienced by threatened species influence microbiome diversity. Consequences of such reductions are normally interpreted in terms of a loss of genetic variation, increased inbreeding and associated inbreeding depression. However, fitness effects of population bottlenecks might also be mediated through microbiome diversity, such as through loss of functionally important microbes. Here we utilise 50 Drosophila melanogaster lines with different histories of population bottlenecks to explore these questions. The lines were phenotyped for egg-to-adult viability and their genomes sequenced to estimate genetic variation. The bacterial 16S rRNA gene was amplified in these lines to investigate microbial diversity. We found that 1) host population bottlenecks constrained microbiome richness and diversity, 2) core microbiomes of hosts with low genetic variation were constituted from subsets of microbiomes found in flies with higher genetic variation, 3) both microbiome diversity and host genetic variation contributed to host population fitness, 4) connectivity and robustness of bacterial networks was low in the inbred lines regardless of host genetic variation, 5) reduced microbial diversity was associated with weaker evolutionary responses of hosts in stressful environments, and 6) these effects were unrelated to Wolbachia density. These findings suggest that population bottlenecks reduce hologenomic variation (combined host and microbial genetic variation). Thus, while the current biodiversity crisis focuses on population sizes and genetic variation of eukaryotes, an additional focal point should be the microbial diversity carried by the eukaryotes, which in turn may influence host fitness and adaptability with consequences for the persistence of populations. Author summaryIt is becoming increasingly clear that organisms and the microbes that live on or in them - their microbiome - affect each other in profound ways that we are just beginning to understand. For instance, a diverse microbiome can help maintain metabolic functions or fight pathogens causing diseases. A disrupted microbiome may be especially critical for animals and plants that occur in low numbers because of threats from e.g. human exploitation or climate change, as they may already suffer from genetic challenges such as inbreeding and reduced evolutionary potential. The importance of such a reduction in population size, called a bottleneck, on the microbial diversity and the potential interactive effects on host health remains unexplored. Here we experimentally test these associations by investigating the microbiomes of 50 inbred or non-inbred populations of vinegar flies. We found that restricting the population size constrain the hosts genetic variation and simultaneously decreases the diversity of the microbiome that they harbor, and that both effects were detrimental to host fitness. The microbial communities in inbred host populations were less robust than in their non-inbred counterparts, suggesting that we should increasingly consider the microbiome diversity, which may ultimately influence the health and persistence of threatened species.

evolutionary biology↗