A checklist of Asteraceae from Pedra do Lagarto, Santa Maria, Rio Grande do Sul, Brazil

1 Laboratório de Estudos em Vegetação Campestre, Instituto de Biociências, Universidade Federal do Rio Grande do Sul. Av. Bento Gonçalves, 9500, Prédio 43431, Agronomia, Porto Alegre, RS, Brazil. 2 Laboratório de Taxonomia Vegetal, Centro de Ciências Naturais e Exatas, Universidade Federal de Santa Maria, Avenida Roraima, 1000, prédio 16, Camobi, Santa Maria, RS, Brazil. Corresponding author: Juliana Schaefer, julianaschaeferbio@gmail.com


Introduction
The Pedra do Lagarto is located in the Santo Antão District, a rural area of the municipality of Santa Maria, Rio Grande do Sul state, Brazil.According to Fortes (1959), this municipality is in the physiographic region of the Central Depression.The typical vegetation has a unique appearance due to a transition between the Atlantic Forest biome, which has dense forests on the slopes of Serra Geral, and the Pampa biome, which primarily includes grasslands.As cited by Marchiori (2009), predominantly herbaceous and shrubby species with cespitose patterns are characteristic in this region.The physiognomy is diverse, grouping numerous grasses, a large contingent of Asteraceae and Apiaceae, and in some places, also the dwarf Myrtaceae species (Marchiori 2009).
Grasslands are natural ecosystems that comprise a wealth of species, predominantly characterized by grasses, which form a continuous landscape and determine the physiognomy of the countryside.However, composite plants are often intermingled with these species, increasing the species richness (Boldrini et al. 2015).In addition to sheltering a large contingent of South Riograndense flora, these grasslands are also source of genetic resources (Welker and Longhi-Wagner 2007), including many endangered species.More than 500 endemic species, which are endangered due to the suppression of native grasslands, have been catalogued (Vélez-Martin et al. 2015).
Asteraceae encompasses about 24.000 species, classified into 1600-1700 genera (Funk et al. 2009) with worldwide distribution except for Antarctica.Its species comprise about 8% to 10% of the angiosperm diversity described worldwide (Funk et al. 2009).In Rio Grande do Sul, 135 genera and 587 species have been confirmed (Flora do Brasil 2017), with 480 occurring in open areas (Boldrini et al. 2015).
Several morphological characteristics in Asteraceae support its monophyly, including the presence of highly modified heads, which include 1 or more series of involucral bracts, a bicarpelar and inferior ovarium (that develops into a cypsela), and connate anthers (Jansen and Palmer 1987).According to Cronquist (1981), the evolutionary success of this family can be attributed, in part, to the development of a chemical defense system, that includes the production of very derived secondary compounds, as well as its great dispersal capacity due to the presence of fruits with feathery pappus, appendages, and adherence structures (Venable and Leblin 1983, cited by Cancelli et al. 2006).Due to these last mentioned dispersal mechanisms, this family plays an important role in the recovery of degraded areas, with pioneer species colonizing degraded environments, such as in clearings and at forest edges (Heiden et al. 2007).Moreover, having been commonly used in folk medicine, this family has been extensively studied as a rich source of secondary metabolites that have pharmaceutical or industrial potential.
According to Nakajima and Semir (2001), Brazil is a hotspot for Asteraceae diversity, and thus, there is a need for intensive floristic surveys, especially in the grasslands, where most of composite taxa occur.Taking this into account, this study aims to survey the Asteraceae from the Pedra do Lagarto, a hill in the state of Rio Grande do Sul, Brazil.Although there are plenty of floristic surveys focusing an arboreal species (see Alberti et al. 2000, Machado and Longhi 1990, Budke et al. 2004, Longhi et al. 1999), little is known about the grassland flora in this region.In addition, this study expands the knowledge of the distribution of Asteraceae species in the state, thus contributing to conservation of especially threatened and seldom collected species.

Methods
Study site.The Pedra do Lagarto Hill is located in the District of Santo Antão, between the geographical coordinates 29°33′ S -34°00′ S and 053°35′ -054°08′ W, at the north of the city of Santa Maria (Fig. 1).The characteristic landscape of the area consists of hills with sandstone outcrops and forest remnants interspersed with grasslands, which is the predominant vegetation in the region (Fig. 2A, B).
The climate is mesothermal and humid, Cfa, according to the Köppen classification.It can be characterized as subtropical humid, with hot summers and without a dry season (Heldwein et al. 2009).The annual average temperature is 22 °C; however, there are large temperature fluctuations that characterize a transitional climate.The rainfall routine, according to the National Institute of Meteorology (INMET), is isoigro, i.e., normal rainfall values are well distributed throughout the year.
Floristic study.The floristic survey was carried out between August 2014 and September 2015, in 17 field expeditions, with an approximate interval of 15 days between each field trip.Samples were used a random walk method (Filgueiras et al. 1994), with changes that included additional collections over previously established lines.In addition, there were 2 extra collections on 2 adjacent hills.The specimens were collected in their reproductive stage, prepared for the herbarium according to the recommended standard methods for angiosperms, and identified with the

Discussion
The species of Asteraceae recorded in this study site are mostly typical of the grasslands of the Central Depression, such as Baccharis articulata (Fig. 3C), Vernonanthura nudiflora, Senecio brasiliensis, and Aspilia montevidensis (Fig. 7B).Nonetheless, due to, the gradient of habitats, such as wetlands, forest remnants, dry grasslands, and rocky outcrops, a great floristic diversity was found.
Asteraceae is the family with the highest diversity in Rio Grande do Sul (Boldrini et al. 2015), with 89 species considered endangered, according to the state list (SEMA 2014).As found in this study, the Asteraceae mainly inhabit grasslands, which according to Overbeck et al. (2007), suffers continuous pressure from human activities such as agriculture and forestry.
Moquiniastrum mollissimum is a species endemic to the central-eastern region of Rio Grande do Sul and was considered "probably extinct" until 2009, when it was found on the side of a granite hill in Viamão (Mondin 2009).In contrast, in the municipality of Santa Maria, the last known record of this species was about 60 years ago.This species was found in grasslands with sandstone outcrops, forming a large population.The place itself supports many plants, including rare or endangered species of other families, such as Mandevilla coccinea (Hook & Arn.) Woodson (Apocynaceae), Hesperozygis ringens (Benth.)Epling (Lamiaceae), Echinopsis oxygona (Link & Otto) Pfeiffer.& Otto (Cactaceae), Parodia ottonis (Lehm.)P. N. Taylor (Cactaceae), Parodia linkii (Lehm.)R. Kiesling (Cactaceae), and Dyckia ibicuiensis Strehm (Bromeliaceae).
Calea clematidea was recorded not only from "Pedra do Lagarto", but also in the adjacent hills, exhibiting Table 1.List of the species identified at the study site, ordered by tribe.Vouchers, habit and habitat are presented for each species.The habit was described according to observations in the study site, eventually completed with information from the literature (in this case, a reference is cited).dense populations and blooming continuously.On the other hand, Aldama megapotamica, endemic to the state, has a restricted distribution to the physiographic regions of Central Depression and Eastern Plateau (Mondin 2004).Isostigma peucedanifolium, Trixis pallida, and Chromolaena angusticeps were found only as scattered individuals.Achyrocline anabelae was found restricted to the top of the hill, which could be considered as an "inselberg", due to its rocky elevation that emerges between the forest remnant and the rural environment.

Species
According to Porembski (2007), rocky outcrops form arid environments that develops centers of diversity for certain types of plants, and often act as spatial refuges for different floras (Clarke 2002), a factor that could explain the relatively high number of endemic and/or threatened taxa found in the study region.
Heterocondylus decipiens, according to Matzenbacher (1979), is a species with a few occurrences in the state, usually limited to the northeastern part.However, this species may be under-collected, due to its morphological resemblance to Campuloclinium macrocephalum.
Taxa such as Conyza, Gamochaeta, Tagetes, Porophyllum, Bidens pilosa, Praxelis clematidea, Baccharis anomala, B. dracunculifolia, B. spicata, B. punctulata, and Solidago chilensis were collected mainly in environments where human influence is intense, such as borders of fields and surrounding small farms.In this context, it is noteworthy that the study area is located next to some Pinus L. plantations (Fig. 2A), a typical suppression of grasslands currently occurring in the state.According to Ziller and Zalba (2008), the expansion of exotic tree cultures is a drastic change in landscape structure and ecological processes, as it generates a significant source of propagules which often results in the establishment of invasive populations in natural remnants.Thus, the risk of losing locally adapted and the species and the native vegetation progressively advances, by the decrease in the size of natural populations.

Figure 1 .
Figure 1.Map of the site of study: location in South America and Brazil, and a detail of the site of study in Santo Antão District, Santa Maria.

Figure 2 .
Figure 2. Study site "Pedra do Lagarto".A. View of the sandstone conglomerate of the Pedra do Lagarto.B. General view of the site of study and borders, showing the native grasslands, a native forest fragment and a Pinus plantation in the adjacent area.