A new species, Leucheria peteroana sp. nov., endemic to a restricted area of the Andes of Central Chile, is here described. Using newly sequenced nDNA and cpDNA data, the phylogenetic affinities of Leucheria and closely related taxa within Nassauvieae are revisited. This new species shows a unique set of characters that clearly distinguish it from other species of Leucheria. Phylogenetic analyses place this perennial species close to annual species found in the pre-Andean environments of Central Chile. A detailed description, distribution map, insights about its habitat, conservation status, and photographs are provided.

Andes, Asteraceae, Laguna Teno, Leucheria, Maule, Nassauvieae, taxonomy

The genus Leucheria Lag. is one of the largest genera within the Nassauvieae tribe. It occurs in the Southern Cone of South America, distributed across Peru, Bolivia, Chile, and Argentina, including the Falkland Islands (Crisci 1976; Katinas et al. 2022). Most species are found within the Patagonian-Andean and Subantarctic Phytogeographic domains (Cabrera and Willink 1973). Leucheria has a rich and complex taxonomic history. For a complete and detailed history of its taxonomy, see Crisci (1976). In the latter work, the first modern revision of the genus, 46 species were recognized. Since Crisci (1976), at least three new species (Katinas et al. 2008a; Katinas et al. 2018; Lavandero et al. 2020) and a new variety (Ratto et al. 2014), which was later elevated to species level (Jara-Arancio et al. 2019), have been described. A recent work by Apodaca et al. (2021) made a significant reclassification, synonymizing 10 annual species of Leucheria into Leucheria tomentosa (Less.) Crisci. In the most recent taxonomic synopsis by Katinas et al. (2022), the number of species of Leucheria was reduced to 29. More recently, Muñoz-Schick and Moreira (2022) included Leucheria graui Katinas, M. C. Tellería, & Crisci within the synonymy of Leucheria apiifolia Phil., further reducing the current number of accepted species of Leucheria to 28.

The diversity center of Leucheria overlaps with the Central and Southern Chilean biodiversity hotspot (Moreira-Muñoz et al. 2012), one of 35 world biodiversity hotspots recognized by Myers et al. (2000) and later by Mittermeier et al. (2005), due to their great diversity and high levels of endemism, combined with a past and ongoing loss of habitat and biodiversity (Myers et al. 2000). Central Chile features a Mediterranean-type climate, although significant climatic heterogeneity exists due to latitudinal and altitudinal gradients, ranging from sea-level to up to 6570 m (Armesto et al. 2007; Luebert and Pliscoff 2017). The extraordinary environmental heterogeneity in this region, along with fluctuating changes due to the glacial history throughout the Quaternary, may have led to the higher species diversity and endemism observed in this area (Arroyo et al. 1995; Villagrán 1995).

Phylogenetic relationships within Nassauvieae have been the subject of several studies, from Phenetics (Crisci 1974) to Phylogenomics (Zhang et al. 2024). In particular, the relationship of Leucheria to Oxyphyllum and Marticorenia was earlier suggested by Crisci (1980). Hellwig (1985) suggested a close relationship of Leucheria to Moscharia, later questioned by Katinas (1994). Early molecular studies, based on the ndhF gene of the chloroplast genome, suggested a close relationship to Jungia L.f. (Kim et al. 2002). Subsequently, Panero and Funk (2008), using 10 chloroplast loci, found Leucheria as sister to a clade formed by Nassauvia, Perezia, Acourtia, Dolichlasium, Trixis and Jungia. However, Panero and Funk (2008) only sampled 9 genera within Nassauvieae. A broader sampling was used by Katinas et al. (2008c) where Leucheria is placed as sister to Polyachyrus, and this clade appears as sister to Moscharia, using both nuclear ITS and the chloroplast trnL-trnF intergenic spacer. Luebert et al. (2009) examined the relationships of monotypic Oxyphyllum within Mutisieae. By using the plastid rbcL and ndhF genes, the trnL-trnF spacer and nuclear ITS region, their work supported the close relationship of Oxyphyllum to Leucheria and Polyachyrus. More recently, Jara-Arancio et al. (2017), based on a broader sampling within Nassauvieae, and using the ITS region and two chloroplast intergenic spacers, placed Leucheria as sister to a clade formed by Moscharia and Marticorenia. More recent studies, using target capture methods (Mandel et al. 2019) and phylotranscriptomics (Zhang et al. 2021; Zhang et al. 2024), have only used a limited sampling within the tribe. Until now, generic and infrageneric relationships within Nassauvieae remain unresolved, with at least two genera, Criscia and Cephalopappus, without any genetic information available.

In the context of a modern taxonomic revision of the genus, unusual specimens of Leucheria were collected in the vicinity of the Lagunas del Teno (35°11'15"S, 70°33'33"W), in the Andes of the Maule Region of Chile. This area is characterized by a steep topography, with elevations up to 4112 m above sea level (Volcán Azufre). This area of the Andes Mountain range is characterized by active volcanic activity, with six volcanic complexes actively monitored in the present (SERNAGEOMIN 2018). Although several botanical collections have been made around this area, most were done near roads, which are limited to a few Andean Mountain passes and international border crossings between Chile and Argentina.

This work aims to describe a new species of Leucheria, providing a distribution map as well as information on its habitat, ecology and phenology. A provisional assessment of its conservation status is also provided. We further investigated its phylogenetic affinities, aiming to re-evaluate the phylogeny of Leucheria presented by Jara-Arancio et al. (2017), and the systematics and taxonomy of the most recent taxonomic synopsis of the genus by Katinas et al. (2022).

Chloroplast markers and the nuclear ribosomal cistron regions have been extensively used to infer phylogenetic relationships within Nassauvieae (Katinas et al. 2008c; Jara-Arancio et al. 2017; Jara-Arancio et al. 2018; Sancho et al. 2018; Nicola et al. 2019). However, not all studies documented the topological incongruences between the chloroplast and nuclear ribosomal cistron. Moreover, only a few of these studies explicitly performed tests to evaluate incongruence between nuclear and chloroplast partitions. In the present study, we have confirmed that there are several topological incongruences between these two datasets for Nassauvieae at both generic and infrageneric level. These results suggest that any systematic study and reclassification proposal within Nassauvieae using these datasets alone or combined should be taken into consideration with caution.

In the present study, Leucheria, as recognized by Crisci (1976) and more recently by Katinas et al. (2022), appears to be paraphyletic, including the morphologically distinct genus Polyachyrus. This result was not shown by Jara-Arancio et al. (2017), as it did not include any sample of Polyachyrus. Additionally, the position of Oxyphyllum as sister to Leucheria + Polyachyrus clade was not retrieved by Jara-Arancio et al. (2017), as it also did not include Oxyphyllum in the sampling. Our analyses, including 25 of the 27 accepted genera of Nassauvieae, consistently retrieved a clade comprising Leucheria, Moscharia, Marticorenia, Oxyphyllum and Polyachyrus.

Within Leucheria, an interesting finding is that our phylogenetic results are more consistent with the taxonomy proposed by Crisci (1976) than the recent proposal by Katinas et al. (2022), which dramatically reduced the number of accepted species of Leucheria. The synonymization of Leucheria millefolium into Leucheria purpurea is not supported by our phylogenetic analyses. Likewise, the synonymization of Leucheria garciana into Leucheria gilliesii is also not supported by the present work. The proposal of lumping 10 species of Leucheria into Leucheria tomentosa by Apodaca et al. (2021), including all the former annual species recognized by Crisci (1976) is here contested. Based on morphology and the revision and comparison of our own field collections with the type specimens, we sampled at least six taxa recognized as annuals by Crisci (1976), and lumped into Leucheria tomentosa by Apodaca et al. (2021). Interestingly, our phylogenetic results indicate that Leucheria tomentosa, as recognized by Katinas et al. (2022), is not monophyletic, suggesting that an important taxonomic work on this group needs to be done, considering both field, herbarium and phylogenetic evidence available (Lavandero et al., in prep.). An unexpected finding was that the new species Leucheria peteroana, is sister to a clade comprised by two annual species found in the Mediterranean region of Central Chile, Leucheria glandulosa and the poorly collected Leucheria glabriuscula. Although these three species have little in common morphologically, it is noteworthy that Leucheria glandulosa has pink anther appendages, whereas the sister clade comprises species with only blue anther appendages. This character, although rarely recorded on herbarium sheets, is taxonomically important. Likewise, Leucheria glabriuscula has a similar pappus, with long pectines (~300–400 µm long), an unusual character within the genus.

The discovery of a new species of Leucheria, restricted to a small region of the Andes of Central Chile highlights the importance of more field sampling, even for widely collected genera. Most herbarium collections, including those in Chile, have a significant collection bias (Daru et al. 2017; Hughes et al. 2021), particularly noticeable in areas with harsh topography and lack of roads, as most of the Andes Mountain range. The access to the Lagunas del Teno, and therefore, the finding of Leucheria peteroana, was only possible because there is an unpaved road that leads to a dam that controls the water flow from the lake, used for irrigation (Caputo et al. 2013). This area is also known to harbour several rarely collected species, such as Calceolaria williamsii Phil. and Leucheria apiifolia. As more fieldwork is done in remote areas of the Andes, it is more likely that new species will be found, particularly those with restricted distributions or with very specific requirements, as confirmed by recent additions to the Andean flora of Chile (Villarroel et al. 2021, 2022; Menegoz et al. 2024).

This work highlights the importance of taxonomic revisions that integrate herbarium studies, field collections and ecology, along with a robust phylogenetic framework, especially for diverse and complex genera, such as Leucheria. Revisions made solely on herbarium species may leave behind important characters that are only visible when dealing with live plants in the field, such as life form, growth habit, texture, odours and colours that eventually fade once pressed. A fully resolved phylogeny of Leucheria is still lacking, and its monophyly has been put to the test by our results. In future works, we will aim to resolve the systematics of Nassauvieae, particularly Leucheria and closely related genera, based on low-copy nuclear genes, following a target capture approach (Mandel et al. 2014).

We are grateful to the curators and staff of CONC and SGO herbaria. We would like to thank Ludovica Santilli, for her help during fieldwork and for carefully revising the manuscript. We would like to thank Dr. Nicolás García and one anonymous reviewer for their helpful comments on the submitted manuscript. We thank Gioconda Peralta and Loreto Carrasco of the Plataformas UC de Secuenciación y Tecnologías Ómicas, Pontificia Universidad Católica de Chile for laboratory support and expert capillary electrophoresis analysis. We would like to thank Joaquín E. Sepúlveda and Guillermo Debandi for sharing photos of Leucheria amoena and Leucheria candidissima, respectively.