Biology subjects

Lehmann, P.

Publications and source records attributed to Lehmann, P..

5 recordsLinked to original sources

bioRxiv2024

Covariation between metabolic and radioactive dose rates in Chornobyl rodents

High metabolic rate may provide fitness benefits for individuals. But high metabolic rates incur energetic costs and the need to ingest more food, increasing the risks of ingesting harmful substances from the environment. How organisms respond to elevated levels of ionizing radiation is an important question in the light of increasing pollution from nuclear accidents and waste, as well as ever-increasing reliance on radiation in medical diagnostics and therapies. We investigated how limits to metabolic rate, and aerobic metabolic scope (ceiling of energetic activity above maintenance levels), of wild rodents inhabiting a gradient of radioactive contamination from the Chernobyl accident covary with the biological burden of radionuclides in their bodies. Our results demonstrate that high biological dose rate correlates with high self-maintenance and low aerobic capacity in adults. In contrast, in subadults high dose rate correlates with high aerobic capacity. Consequently, high dose rate correlates with low aerobic scope in adults, but with high aerobic scope in subadults. Despite the uncertainty of the causal mechanisms, whether the dose rate affects the metabolic rate, the reverse or the reciprocal feedback prevail, it can be hypothesized that metabolic down-regulation could contribute to protection against radioactive exposure. Yet, metabolic down-regulation might be constrained by developmental obligations. Understanding the physiological mechanisms affecting responses to radiation exposure is key for risk assessment of environmental contamination, radiotherapies, and space exploration, and may help to rectify discordant opinions concerning the effects of radiation on the ecology of organisms living in Chornobyl.

ecology↗

bioRxiv2019

Coevolution between life-history and metabolic rate depends on ontogenetic stage

Metabolic rate is considered to determine the energetic investment placed into life-history traits, regulating the speed of an organisms life-cycle and forming the so called \"pace-of-life\". However, how metabolic rate and life-history traits co-evolve remains unclear. For instance, the energetic demands of life-history traits, including the number of energy allocation trade-offs, is unlikely to remain constant over ontogeny. Therefore, the predicted coevolution between metabolic rate and life-history could be specific to particular ontogenetic stages, rather than a stable property of an organism. Here, we test the ontogenetic dependency of the coevolution between metabolic rate and the pace of life-history, under strictly standardized conditions using 30 species of killifish, which are either annual species adapted to ephemeral pools or non-annual species inhabiting more permanent waterbodies. Standard metabolic rates were estimated at three ontogenetic stages, together with relevant life-history traits, i.e. growth (juveniles), maturity (young adults), and reproductive rate (reproductive adults). Life-history traits largely followed predicted pace-of-life patterns, with overall faster/higher rates in annual species. The divergences in life-history traits across species tended to increase over ontogeny, being smallest during juvenile growth and largest in reproductive adults. However, associations between life-history strategy and metabolic rate followed a reversed pattern, being strongest in juveniles, but lowest in reproductive adults. Our results are concordant with the number of energetic trade-offs increasing over ontogeny, which results in a stronger covariation between physiology and life-history traits earlier in ontogeny.

evolutionary biology↗

bioRxiv2019

Developmental plasticity in metabolism but not in energy reserve accumulation in a seasonally polyphenic butterfly

The evolution of seasonal polyphenisms (discrete phenotypes in different annual generations) associated with alternative developmental pathways of diapause (overwintering) and direct development is favoured in temperate insects. Seasonal life history polyphenisms are common and include faster growth and development under direct development than diapause. However, the physiological underpinnings of this difference remain poorly known despite its significance for understanding the evolution of polyphenisms. We measured respiration and metabolic rates through the penultimate and final larval instars in the butterfly Pieris napi and show that directly developing larvae grew and developed faster and had a higher metabolic rate than larvae entering pupal diapause. The metabolic divergence appeared only in the final instar, that is, after the induction of developmental pathway that takes place in the penultimate instar in P. napi. The accumulation of fat reserves during the final larval instar was similar under diapause and direct development, which was unexpected as diapause is predicted to select for exaggerated reserve accumulation. This suggests that overwinter survival may be more dependent on metabolic suppression during diapause than the size of energy reserves. The results, nevertheless, demonstrate that physiological changes coincide with the divergence of life histories between the alternative developmental pathways, thus elucidating the proximate basis of seasonal life history polyphenisms. Summary statementThe switch between diapause and direct development results in developmental pre-diapause plasticity in life history and metabolism but not in reserve accumulation in a seasonally polyphenic butterfly.

evolutionary biology↗

bioRxiv2018

A female alternative life-history strategy arose via novel recruitment of homeobox gene, BarH-1

Tradeoffs affect resource allocation during development and result in fitness consequences that drive the evolution of life history strategies. Yet despite their importance, we know little about the mechanisms underlying life history tradeoffs in wild populations. Many species of Colias butterflies exhibit an alternative life history strategy (ALHS) where females divert resources from wing pigment synthesis to reproductive and somatic development. Due to this reallocation, a wing color polymorphism is associated with the ALHS: individuals have either yellow/orange or white wings. Here we map the genetic basis of the ALHS switch in Colias crocea to a transposable element insertion downstream of the Colias homolog of BarH-1, a homeobox transcription factor. Using CRISPR/Cas9 gene editing, antibody staining, and electron microscopy we find morph-specific specific expression of BarH-1 suppresses the formation of pigment granules in wing scales. Lipid and transcriptome analyses reveal physiological differences associated with the ALHS. These findings characterize a novel mechanism for a female-limited ALHS and show that the switch arises via recruitment of a transcription factor previously known for its function in cell fate determination in pigment cells of the retina.

genomics↗

bioRxiv2018

Complex responses of global insect pests to climate change

Insect pests strongly affect the productivity and profitability of agriculture and forestry. Despite the well-known sensitivity of insects to abiotic effects such as temperature, their potential responses to ongoing climate change remain unclear. Here we compile and review documented climate change responses of 31 of the globally most impactful phytophagous insect pests, focussing on species for which long-term, high-quality data are available. Most of the selected species show at least one response affecting their severity as pests, including changes in geographic range, population dynamics, life-history traits, and/or trophic interactions. Of the studied pests, 41% only show responses that are linked to increased pest severity, 4% only show responses of decreased severity, whereas importantly 55%, the majority of studied pests, show mixed responses including both increased and decreased severity under ongoing climate change. Variability in impact is further supported by a thermal sensitivity analysis showing little benefit of climate warming in relation to the optimal developmental temperatures for the majority of these pests under both current climate and future projections. Overall the results show that calculating the net effect of climate change on phytophagous insect pest impact is far from straightforward. The documented variation in responses, e.g. between agricultural and forest pests, indicates that efforts to mitigate undesirable climate change effects must target individual species, taking into account the complex ecological and evolutionary mechanisms underlying their responses.

ecology↗