Biology subjects

Ehlers, B. K.

Publications and source records attributed to Ehlers, B. K..

3 recordsLinked to original sources

bioRxiv2020

Identity and provenance of neighbors, genotype-specific traits and abiotic stress affect intraspecific interactions in the annual legume Medicago truncatula

O_LIAccounting for intraspecific variation may improve our understanding of species coexistence. However, our knowledge of what factors maintain intraspecific variation is limited. We predicted that 1) a plant grows larger when with non-kin (i.e. different genotypes) than kin (i.e. same genotype) neighbors, 2) abiotic stress alters the outcome of kin vs. non-kin interactions, 3) genetic identity of plants affects composition of soil microbiome. C_LIO_LIWe set up mini-communities of Medicago truncatula, where focal genotypes were grown together with two kin or two non-kin neighbors from different origins. We analyzed how origin, identity of interacting genotypes and abiotic stress affected growth and fruit production. We also analyzed the composition of soil microbial communities. C_LIO_LIFocal plants grew larger in non-kin than in kin mini-communities. This pattern was stronger in low level of abiotic stress and when interacting genotypes were from similar origins. However, genotypic variation in growth and response to competition had a stronger effect on growth than mini-community type. Plant genotype identity did not affect soil microbiome. C_LIO_LIWe find that intraspecific variation is affected by genotype-specific traits and abiotic stress. Geographic, rather than genetic, distance among interacting genotypes affects the outcome of intraspecific interactions. C_LI

plant biology↗

bioRxiv2020

From genotype to phenotype: maintenance of a chemical polymorphism in the context of high geneflow.

A major question in evolution is how to maintain many adaptive phenotypes within a species. In Mediterranean wild thyme, a staggering number of discrete chemical phenotypes (chemotypes) coexist in close geographic proximity. Plant chemotypes are defined by the dominant monoterpene produced in their essential oil. We study the genetics of six distinct chemotypes nested within two well established ecotypes. Ecotypes, and chemotypes within ecotypes, are spatially segregated, and their distribution tracks local differences in the abiotic environment. The ecotypes have undergone a rapid shift in distribution associated with current climate change. Here, combining genomic, phenotypic, and environmental data, we show how the genetics of ecotype determination can allow for such rapid evolutionary response despite high gene flow among ecotypes. Variation in three terpene-synthase loci explains almost all variation in ecotype identity, with one single locus accounting for as much as 78% of it. Phenotypic selection on ecotypes combined with low segregating genotypic redundancy and tight genetic determination leaves a clear footprint at the genomic level: alleles associated with ecotype identity track environmental variation despite extensive gene flow. Different chemotypes, nested within each ecotype, also track environmental variation. However, in contrast to ecotypes, chemotype identity is determined by more loci and show a wider range of genotypic redundancy, which dilutes the impact of phenotypic selection on alleles associated with different chemotypes. Identifying the genetics behind this polymorphism in thyme is a crucial step towards understanding the maintenance of this widespread chemical polymorphism found in many aromatic Lamiaceae.

evolutionary biology↗

bioRxiv2019

Kin recognition and genetic variation for competitive ability in the annual legume Medicago minima

Knowing which mechanisms drive the outcome of intraspecific interactions is highly relevant for understanding diversity maintenance. Plant species that exhibit strong genetic substructure over small spatial scales may be exposed to frequent interactions with closely related individuals. Predictions of how genetic similarity may drive the outcome of intraspecific interactions are based on two contrasting theories: the resource partitioning hypothesis and kin selection theory. The first predicts that competition will be stronger among closely related conspecific (i.e. kin) because similar genotypes have similar resource requirements. The second predicts instead that competition will be reduced among kin, in order to maximize the inclusive fitness. Although efforts have been made to reconcile these two theories as non-mutually exclusive, the outcomes of intraspecific interaction studies are frequently interpreted as the results of either one or the other. We experimentally tested the hypothesis that intraspecific interactions may be driven by both genetic variation for competitive ability and reduced competition among kin. We used an annual legume, Medicago minima, to conduct two greenhouse experiments testing changes in root behaviour, above-ground growth and biomass in response to neighbour identity. We found evidence of both genetic variation for competitive ability and reduced competition among kin in some genotypes. Reduced competitive growth towards kin was found in the most competitive genotypes, suggesting that kin avoidance and competitive ability were simultaneously affecting plant behaviour and growth. With presence of both kin competition avoidance and variation for competitive ability, the outcome of intraspecific interactions will strongly depend on the local spatial genetic substructure. This is highly relevant to predict how intraspecific competition affect diversity maintenance.

ecology↗