Community level phylogenetic diversity does not differ between rare and common lineages across tallgrass prairies in northern Great Plains
Creators: name: Herzog, Sarah
name: Latvis, Maribeth
Publisher: name: Zenodo
Year: 2022
Subjects: grassland
rare species
redundancy
Conservation

description: In some cases, rare lineages provide resistance to invasions, serve as keystone species, and contribute unique functional or phylogenetic diversity to their communities. In other cases, rare species may be functionally redundant with common species and do not significantly contribute to phylogenetic diversity. How rare and common species coexist and contribute to local species pools may depend upon attributes of their communities and remains an open question in ecology. Niche differentiation has served as an explanation for species coexistence, and phylogenetic relatedness provides a means to approximate how ecologically similar species are to each other. To explore the contribution of rare species to community phylogenetic diversity, we sampled twenty-one plant communities across the Prairie Coteau ecoregion, home of the largest tracts of untilled northern tallgrass prairie and of high conservation concern. We used breakpoint analysis through iterative addition of less abundant species to the phylogenetic tree for each community. We also assessed the phylogenetic signal of abundance classes using Blomberg's K statistic and calculated the phylogenetic similarity between rare and common species using a phylogenetic beta diversity metric (D<sub>nn</sub>). To estimate the phylogenetic structuring of these prairie communities, we calculated two common metrics that capture evolutionary relatedness between species (MPD, and MNTD) and examine the correlation between these metrics and species richness. Overall, we found rare species do not contribute higher levels of phylogenetic diversity than more common species in the Prairie Coteau ecoregion. Eight of 21 communities had significant breakpoints, where the addition of a less common species resulted in a shift in phylogenetic diversity, with only four communities having an increasing trend for the rarest species. Phylogenetic signal for abundance was low and unsignificant across 18 communities, while four sites did show significant low phylogenetic signal. We additionally found our communities had lower phylogenetic diversity than expected from the regional species pool. Finally, we found weak to no correlation when using MPD and MNTD. Our results indicate niche differentiation does not explain rare species persistence in tallgrass prairies. We found species were more closely related than expected from random community assembly, suggesting high functional redundancy within this system. This is promising for the long term viability of this ecosystem, but only insofar as enough species remain in the system to create redundancy. With ongoing biodiversity loss, it is essential we understand the role rare species play in their communities. Phylogenetic diversity could be an important tool for researchers and managers to utilize for conservation of critically threatened systems such as tallgrass prairies.
description: R is required to use code.Funding provided by: U.S. Department of Agriculture<br>Crossref Funder Registry ID: http://dx.doi.org/10.13039/100000199<br>Award Number: NIFA 1016764