Abstract Detail

Symbioses: Plant, Animal, and Microbe Interactions

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

Floral microbiome differs between metal hyperaccumulating and related non-accumulating species: implications for reproductive isolation.

Differences in floral traits can contribute to reproductive isolation. Divergence in floral color, nectar quality and scent can attract different pollinator fauna, reducing intermating between divergent plants. Bacteria and fungi living on flowers (collectively, the floral microbiome) can biochemically alter traits like nectar sugar content and floral scent, which in turn can change the attractiveness of flowers to pollinators. Yet the role that floral microbiomes play in reproductive isolation is not known, begging the question: Is the floral microbiome a missing piece of the speciation puzzle? We examine this broader question in elemental hyperaccumulating plant species. These live in heavy metal-rich soils and accumulate metal at extraordinary concentrations, making their tissue toxic to some pollinators, herbivores and microbes. Moreover, metals in hyperaccumulators can influence the composition of their pollinators, and the leaves and roots of some hyperaccumulators are known to host metal-tolerant microbes. Thus, the toxicity of metal in hyperaccumulators may shape floral microbial species composition (species that tolerate metal) or biochemical function (strains that tolerate metal), contributing to divergent pollinator fauna. Here we assess whether the evolution metal hyperaccumulation is associated with an exceptionally differentiated floral microbiome. We compare floral microbiomes of each of two independently evolved Brassicaceous hyperaccumulators from California, Streptanthus polygaloides (accumulates Ni) and Stanleya pinnata (accumulates Se), to two of their non-accumulating relatives. We sampled flowers from plants at each of 3-6 populations from the 6 host species (two trios of plant species, n = 290 individuals). By including non-accumulating relatives, we can benchmark uniqueness of hyperaccumulator microbiomes, and determine how much microbiome variation stems from a shared evolutionary history between hosts. Specifically, we test whether 1) community composition of the floral microbiome and 2) predicted microbial biochemical functions are more differentiated than expected given phylogenetic relatedness of hyperaccumulators to non-accumulating relatives. We sequenced 16S rRNA and ITS regions of DNA to characterize floral microbiomes. We compared microbiome community composition using multivariate mixed models. Results thus far show a clear difference between hyper- and non-accumulating microbial communities. For instance, the nickel hyperaccumulator Streptanthus polygaloides differed from its non-accumulating relative S. tortuosus in bacterial and fungal community composition and Shannon diversity. Notably, S. polygaloides lacked well-known nectar bacteria and yeast present in S. tortuosus including Acinetobacter nectaris and Sporobolomyces roseus. This research will elucidate the relationship between evolution of the novel trait of hyperaccumulation and the floral microbiome, and progress understanding of the microbiome’s involvement in speciation.

1 - University of Pittsburgh, Biological Sciences, 4249 Fifth Ave, Pittsburgh, PA, 15260
2 - University of Pittsburgh, Biological Sciences, 4249 Fifth Avenue, Pittsburgh, PA, 15260, USA

Keywords:
Microbiome
anthosphere
floral traits
hyperaccumulation
evolutionary ecology.

Presentation Type: Oral Paper
Session: SYMB2, Symbioses: Plant, Animal and Microbe Interactions 2
Location: /
Date: Tuesday, July 20th, 2021
Time: 1:00 PM(EDT)
Number: SYMB2003
Abstract ID:726
Candidate for Awards:None