Flora of the Spix and Martius expedition in Piauí: a 200 year later parallel

The floristic composition of a place can be changed by human actions, such as agricultural activities, farming, and construction and by natural factors, such as soil type, phenology, and fires. This study recorded the current flora of the region traveled by J. B . von Spix and C. F. P. von Martius in Piauí state, Brazil, comparing the data with species from the same region described in the Flora Brasiliensis. Data were collected in May 2019. A total of 157 species belonging to 113 genera and 36 families were catalogued. The presence of endemic species from the Caatinga and Cerrado biomes and the first occurrence of Chorchorus hirtus L. in the state were recorded. In the Flora Brasiliensis, 166 species, 107 genera, and 38 families were listed for Piauí. When comparing the species recorded in Flora Brasiliensis with the survey carried out in this study, 200 years later, at a family level, Fabaceae, Poaceae, and Malvaceae had the largest number of species, but the listed species did not show high correlation. It is believed that mainly environmental changes, such as reduction of areas with aquatic vegetation, growth of cities, and anthropogenic actions, such as deforestation in the area covered by the European researchers are reasons for the discrepancy in the listed flora.


Introduction
The vegetation of Piauí is characterized by mosaics; distribution of species has been driven by climate and geological conditions and influence of other domains, such as: Amazonia, the Northeast, and the Brazilian highlands (Farias & Castro 2004).
Three main types of vegetation formations are distinguishable: the Caatinga, with approximately 49.6 % (12,478,363 ha); the Cerrado, with approximately 47 %, 33 % of which corresponding to the core domain area (8,349,759 ha) and 14 % (3,507,107 ha) to transition areas; and the remaining area, with less than 3 % (738,156 ha) corresponds to transitional forests with high biodiversity and significant heterogeneity, where species from different floristic domains (Amazon, Cerrado, Caatinga, and Atlantic Forest) are found (Castro 2020, Santos 2021).
Flora diversity is an important component of ecosystems (Hua et al. 2022).
Studies on floristic composition are important for knowing and understanding vegetation structure and dynamics and gather qualitative and quantitative information about the studied areas, especially regarding geographic distribution of species and their abundance in different locations (Souza et al. 2017, Vasconcelos et al. 2017).The floristic composition of a place can be changed by human activities, including livestock, agriculture, and construction, and by natural factors, such as fires and the vegetation phenology over dry and rainy seasons (Silva et al. 2010).Fire disturbance, for example, alters soil-vegetation associations, regulating the structural nature of these communities (Lira-Martins et al. 2022).
The year of 2019 marked the bicentenary of a visit to the state of Piauí, Brazil, by the scientific expedition of the naturalists Johann Baptist von Spix (zoologist) and Carl Friedrich Philipp von Martius (botanist).These researchers traveled about 500 km through the territory of Piauí, from southeast to northwest, during April and May 1819 (Spix & Martius 1981).Martius collected many species that were later recorded in the Flora Brasiliensis, which is the most important basis for studies of the Brazilian flora.The species recorded in the work are a testament to the biological richness of Brazil and the state of Piauí.
Despite the floristic abundance evidenced in the different botanical excursions undertaken since the 19th century by foreign botanists such as Martius (Spix & Martius 1981) and George Gardner (Gardner 1975) and, more recently, in many studies carried out within the scope of postgraduate and undergraduate programs at Brazilian universities, no floristic study of similar scope, covering so many areas of Piauí, has been carried out.Consequently, there are still many gaps in the information about the native flora of the state.Thus, due to the importance and floristic richness of the major vegetational domains of Piauí (Caatinga and Cerrado-Caatinga transitional vegetation).
In this context, the study has as its central question: Does the current record of species maintain similarity with what was collected for the region according to Flora Brasiliensis records?The hypothesis defended is that natural factors, environmental alterations provoked by the growing development, environmental degradation and intensified deforestation in Brazil from the 20th century onwards, led to a change in the current flora of the region covered by Spix and Martius.Thus, the present study aimed to record the current flora of the area in Piauí through which Spix and Martius traveled, and compare the new data with the species of the same region described in the Flora Brasiliensis.

Study area
The study area was in the Semiarid macroregion, which presents Caatinga vegetation (predominant) and Cerrado-Caatinga transitional vegetation.The municipalities in which the study was carry out were selected considering the current political-geographical division of Piauí, following the route described by Spix & Martius (1981) (Fig. 1), and confirmed by Lima (2005) and Silva (2017).The area currently corresponds to the municipalities of Conceição do Canindé, Simplício Mendes, Campinas do Piauí, Santo Inácio do Piauí, Colônia do Piauí, Oeiras, Santa Rosa do Piauí, Cajazeiras do Piauí, Arraial, Francisco Ayres, and Regeneração, all located in the Canindé River basin (Fig. 2).

Collection of botanical material
The revisiting of the Spix and Martius expedition route was carried out by a field excursion in May 2019, the same period as the 1819 expedition.The collections of botanical material were carried out at random stops on the route through Caatinga and Cerrado-Caatinga transitional vegetation, including streams and river banks, mainly on the banks of the Canindé River, as it was the place focused by the Martius collection, according to reports of the work.The botanical material from the current expedition was processed using usual botanical techniques (Mori et al. 1989) and identified using identification keys, original descriptions, specialized bibliography, comparison with the TEPB collection (acronyms according to Thiers, continuously updated), and digital collections available in the databases Reflora -Virtual Herbarium (Flora do Brasil 2020), Species Link (CRIA 2021), POWO (2021 andTropicos.org (2021); duplicates of samples from taxa that present greater difficulty in identification were sent to specialists.Dried specimens were incorporated into the HDELTA collection (acronyms according to Thiers, continuously updated).
The listing of taxa was based on the Angiosperm Phylogeny Group (APG IV 2016), and the spelling of taxon names and life forms of the species followed the Flora e Funga do Brasil (2021) website.All collections of the collected specimens were georeferenced.

Floristic Survey of the Flora Brasiliensis
A survey of the plants from Piauí collected by Martius in 1819 and recorded in the Flora Brasiliensis was carried out, using the resources of the websites CRIA (2021) and BHL (2020), where the work is available online.The 15 volumes of the work were analyzed page by page and relevant families and botanical species were arranged in electronic spreadsheets and tables.After surveying the flora, the botanical nomenclature of all species was updated, according to the online databases POWO (2021) and Flora e Funga do Brasil (2021).The list of species was organized in electronic spreadsheets and tables for counting and comparison with the flora inventoried in the present work.

Results and Discussion
The current sample of the floristic composition presented 157 species, distributed into 113 genera and 36 families.Considering the life forms of the species, herbs were the most representative (Tab.1).Considering the 36 families found in the survey, those with the most species were Fabaceae (38 species), Malvaceae (16 species), Poaceae (14 species) and Euphorbiaceae (9 species).The genera with most species were Cyperus autor and Sida autor, with five species each and Ipomoea L., Mimosa autor, and Senna autor, with four species each.
The family with the largest number of endemic species was Fabaceae (n = 4), is considered the best represented family of the Caatinga and has the most significant number of endemic species (Córdula et al. 2014, Fernandes et al. 2020, Barreto, Fernandes & Queiroz 2020).
This survey recorded the first occurrence of the species Corchorus hirtus L. (Malvaceae) in the state of Piauí (Sá et al. 2021), contributing to expanding information about the geographic distribution of this species and the floristic richness of the state.
Expanding the floristic list of Piauí is an important potential objective for future studies.The results of the present study reinforce the need for further studies for the state flora, since no floristic and taxonomic studies in the studied semiarid region were found in the literature.
The floristic survey of species in Piauí conducted by Martius and published in the Flora Brasiliensis recorded 164 species, distributed into 115 genera and 39 families.After the nomenclatural update of these data, the 164 species were distributed into 107 genera and 38 families (Tab.2).The most representative families were Fabaceae (43 species), Poaceae (29 species), Malvaceae (nine species), and Asteraceae (eight species).The first three were the most representative families recorded by Martius and remained the same in the present collection in 2019.(Giulietti el al. 2004) and Magonia pubescens, which is endemic to the Cerrado biome (Castro 2007).
The flora collected by Martius includes plants from aquatic and swamp environments belonging to the Bryophyta, Pterophyta, and Magnoliophyta divisions, in addition to plants recognized as aquatic macrophytes.It is noteworthy that the wetlands of the region such as the Canindé River and the streams, the main collection sites for Martius (Spix & Martius, 1981), were largely converted into areas for agricultural development, urban areas, civil construction, among others.others.In addition, the high rainfall variability has been affecting the availability of water resources, being reduced in quantity and quality in the regions of the Brazilian Northeast, mainly in the semiarid region (Silva et al. 2023), factors that contributed to the little similarity between the inventoried flora in 1819 with the flora of 2019.
Regarding the structure and life forms/habit of the species, it appears that Martius collected more herbs, shrubs, and subshrubs.His list presented few tree species in relation to the current flora collected.He also collected palm species, which were his preferred ones, according to his reports (Fig. 3).In this study, specimens of palm trees were not collected because they were not in a reproductive state.The habit classification of the species was carried out according to the Flora e Funga do Brasil (2020).

Conclusions
The vegetation along the Spix and Martius 1819 expedition route includes representative species of the Caatinga and Cerrado biomes.Comparing the results of 2019 to the flora collected by Martius, there was little similarity, except at family level.Martius collected many macrophyte species.Considering that the present study is a comparison between two flora surveys in the same area carried out 200 years apart, environmental factors, especially anthropogenic changes, may have altered the flora composition of the region, contributing to the difference between the two inventories.
The list of families and species recorded in the present study indicates that the studied area, in the Semiarid region of Brazil, might have a higher floristic diversity than previously thought, since new species have been recorded during the study, such as Corchorus hirtus, and endemic species.

Figure 1 .
Figure 1.Representative image of the original route of the Spix and Martius expedition in Brazil from 1817 to 1820 and in Piauí in 1819.Source: Brasilianische Reise 1817 -1820: Carl Philipp von Martius.Geburtstag photograph by Jorg Helbig (1994).

Figure 2 .
Figure 2. Representative map of the botanical collection points in the bicentenary excursion following the route of the Spix and Martius expedition through the state of Piauí, Brazil.

Figure 3 .
Figure 3. Habit of species collected by Martius in 1819 and by the 2019 expedition, in Piauí, according to the Flora e Funga do Brasil (2020).

Table 1 -
Composition and habit of the flora sampled in the Spix and Martius expedition route in the state of Piauí, Brazil.