Abstract

Western North America has been experiencing persistent drought exacerbated by climate change for over two decades. This extreme climate event is a clear threat to native plant communities. Artemisia tridentata is a keystone shrub species in western North America and is threatened by climate change, urbanization, and wildfire. A drought Genotype × Environment (G × E) experiment was conducted to assess phenotypic plasticity and differential gene expression in A. tridentata. The G × E experiment was performed on diploid A. tridentata seedlings from two populations (one from Idaho, USA and one from Utah, USA), which experience differing levels of drought stress during the summer months. Photosynthetic data, leaf temperature, and gene expression levels were compared between treatments and populations. The Utah population maintained higher photosynthetic rates and photosynthetic efficiency than the Idaho population under drought stress. The Utah population also exhibited far greater transcriptional plasticity than the Idaho population and expressed genes of response pathways distinct from those of the Idaho population. Populations of A. tridentata differ greatly in their drought response pathways, likely due to differences in response pathways that have evolved under distinct climatic regimes. Epigenetic processes likely contribute to the observed differences between the populations.

Although vanilla is one of the most valuable spices, there is a lack of understanding of the genomic variability of the main vanilla producing species, Vanilla planifolia, within its cultivated origin, Mexico. High genomic heterozygosity levels within the globally cultivated ‘Daphna’ genome have raised questions on the possibility of a hybrid origin and analogous genomic signatures of vanilla cultivated within its origin. This study investigated these questions by assessing whether the genomic structure of Mexican V. planifolia reflected domestication events. Whole genome re-sequencing was used to compare genome complexity between 15 cultivated accessions from different regions and gene pools. Results showed high levels of heterozygosity, ranging from 2.48% to 2.85%, in all but one accession, which exhibited a low level (0.403%). Chromosome-level comparative analyses revealed genomic variability among samples, but no signals of chromosome rearrangements. These findings support the hypotheses that cultivated vanilla resulted from hybridization and that multiple domestication events have shaped cultivated vanilla leading to the formation of landraces. High cultural diversity within this region further supports the occurrence of multiple domestication processes. These results may help to improve breeding and conservation efforts aiming to preserve the genetic diversity of this beloved spice threatened by climate change.

Although vanilla is one of the most popular flavours in the world, there is still uncertainty concerning the native distribution of the species that produces it, Vanilla planifolia. To circumscribe the native geographical extent of this economically important species more precisely, we propose a new landscape-based approach to incorporate information from open-source databases and validate occurrences. In this approach, we include metrics to account for habitat suitability and population sustainability in terms of the biotic (co-occurrence of pollinators and dispersers) and abiotic (habitat quality) factors limiting plant distributions. To further validate occurrences within the resulting distribution, we compare the presence of morphologically similar wild relatives, assess the heterogeneity of ecological niches and verify the correct identification of herbarium specimens. Results from this approach suggest that V. planifolia has a larger geographical distribution than previously recognized; we hypothesize that populations naturally dispersed from Mesoamerica and became established in South America (with a south-eastern limit in Brazil). The recognition of an improved estimate of the distribution of this species will increase the accuracy of predictive models, promote further species circumscription, improve the efficacy of conservation strategies, and help to ensure the sustainability of a valuable, sought-after spice.