Abstract Detail

Symbioses: Plant, Animal, and Microbe Interactions

Cullen, Nevin [1], Ashman, Tia-Lynn [2].

Contrasting patterns of floral microbiome assembly in two clades of elemental hyperaccumulating plants.

Flowers host communities of bacteria and fungi, yet we have a nascent understanding of factors driving variation among plant species. Although we might expect microbiomes to differ in composition among hosts based on host relatedness, species with unique floral chemistry, like metal hyperaccumulators, may uniquely filter their floral microbiome leading to high divergence. Alternatively, geographic distance may structure microbiome composition among host plants as it impacts microbe dispersal. To shed light on drivers of floral microbiome variation, we compared floral bacterial and fungal communities within two clades of Brassicaceae (where hyperaccumulation is widespread) – Streptanthus from the Sierra Nevada Mountains and Stanleya from deserts of eastern CA and southern NV. We sampled flowers of 3-6 populations/species of a focal hyperaccumulator, which sequesters high levels of Ni (Streptanthus polygaloides) or Se (Stanleya pinnata), and two non-accumulating relatives of each focal species. Within each clade we tested whether host species varied in microbiome 1) alpha diversity 2) beta diversity (community composition), and 3) whether host phylogenetic distance, geographic distance, or floral chemistry were stronger drivers of microbiome composition. We characterized bacterial and fungal epiphyte communities with amplicon sequencing of 16S rRNA and ITS regions of DNA, respectively. We characterized floral chemistry with ICP-MS and host relatedness with a molecular phylogeny of Brassicaceae. Streptanthus hosts varied significantly in microbial alpha diversity (with the hyperaccumulator being most diverse) and community composition, while Stanleyoid hosts did not differ in alpha diversity or composition. Floral chemistry was the strongest driver of variation in bacterial and fungal community composition, being stronger among Streptanthus species than Stanleyoids. In Stanleyoid bacterial communities, little variation was explained by any predictors, while chemistry was more important in driving compositional variation among Stanleyoid fungal communites. In Streptanthus bacterial and fungal communities, floral chemistry explained the more variation than geography or phylogeny – specifically, nickel concentrations were correlated with compositional differences between S. polygaloides and its relatives. This pattern was not observed with selenium in Stanleya pinnata. While floral elemental composition seems broadly important in shaping floral microbiome composition, there are clear clade-level differences in the influence chemistry has over microbial communities. Hyperaccumulation appears to uniquely structure the floral microbiome of the nickel hyperaccumulator, but not the selenium hyperaccumulator, suggesting microbes may vary in their interactions with floral toxins. Further research investigating floral microbiome variation within hyperaccumulators is warranted.

1 - University of Pittsburgh, Biological Sciences, Clapp Hall, 4249 Fifth Ave, room 211/216, Pittsburgh, PA, 15260, United States
2 - Department Of Biological Sciences, 1252 Bellerock Street, Pittsburgh, PA, 15217, United States

Abiotic stress
community assembly
California Floristic Province
Heavy Metal.

Presentation Type: Oral Paper
Number: SYM2002
Abstract ID:536
Candidate for Awards:None

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