# Grindelia mutabilis (Asteraceae: Astereae), a New South American Species and a Link for Synonymizing Notopappus

## TL;DR

A new plant species, Grindelia mutabilis, is discovered in Brazil and could lead to reclassifying the genus Notopappus.

## Contribution

The paper introduces a new critically endangered plant species and proposes synonymizing Notopappus under Grindelia based on morphological and phylogenetic evidence.

## Key findings

- Grindelia mutabilis is a new species found only in a specific park in Brazil.
- The species exhibits a unique combination of traits that overlap with Notopappus.
- Phylogenetic evidence supports the non-monophyly of Notopappus and its synonymization under Grindelia.

## Abstract

Grindelia mutabilis (Asteraceae, Astereae), a new species from Brazil endemic to the Espinal Ecoregion of the Río de La Plata Grasslands Bioregion and Pampa Province of the Chaco Biogeographical Domain, is proposed and illustrated. The new species is characterized by a combination of traits: small, rosette cespitose habit, linear to linear–oblanceolate leaves, light-yellow to pastel salmon ray florets, three-winged ray floret cypselae bearing a pappus of two to four elements and two-winged disc floret cypselae bearing a pappus of two elements. It has a highly restricted habitat and is known exclusively within Parque Estadual do Espinilho in Rio Grande do Sul, Brazil. Preliminary conservation assessments classify the new species as Critically Endangered. We provide illustrations and photographs, as well as a distribution map with an identification key for the South American Grindelia species with winged cypselae. The intriguing morphology of this species combines characters traditionally regarded as diagnostic for Notopappus, a genus segregated from Haplopappus and Grindelia. Previously published phylogenetic studies of related taxa indicate that the recognition of Notopappus as monophyletic is not supported and render Grindelia as non-monophyletic too. Based on this combined morphological evidence and existing phylogenetic hypotheses, we reaffirm the non-monophyly of Notopappus and formally propose its synonymization under Grindelia s.l.