Acanthaceae from Cuiabá lowlands, Mato Grosso, Brazil: a vegetational mosaic extending from Chapada dos Guimarães to Pantanal

Abstract This study presents a taxonomic survey of the species of Acanthaceae in the Cuiabá lowlands, an area encompassing several habitats, from rock outcrops in Chapada dos Guiamarães to the periodically flooded forest areas in the Pantanal. Herbarium collections were analyzed and 13 field expeditions were carried out to visit different phytophysiognomies and ecosystems. The family is represented by 31 species and 12 genera, the most diverse being Justicia (10 species) and Ruellia (eight species). Additionally, Dicliptera squarrosa, Dyschoriste schottiana, Ruellia blechum, R. jussieuoides, and R. trachyphylla are newly recorded in the state of Mato Grosso. The number of species is higher if compared with other taxonomic studies of Acanthaceae in Central-Western Brazil. Despite the area being overlooked by the botanical community, we expect our results will instigate further taxonomic studies in the area. This study provides an identification key, short descriptions, comments on taxonomy and distribution, and photographs.


Introduction
Acanthaceae, a member of Lamiales (APG IV 2016), contains about 250 genera and 4,000 species (Wasshausen & Wood 2004;Tripp & McDade 2014;Manzitto-Tripp et al. 2022).The family is pantropically distributed, with centers of diversity in tropical and subtropical regions of Africa (including Madagascar), Indo-Malaysia and the Neotropical region.In the Neotropical region, Brazil, the Andes, and Central America are remarkably species rich (Grant 1955;Wasshausen & Wood 2004;Daniel 2009).In Brazil, 47 genera Rodriguésia 74: e00612022.2023 and 499 species are recorded, while 21 genera and 153 species occur in the Central-West region (Flora e Funga do Brasil 2020, continuously updated).For the state of Mato Grosso, where no taxonomic studies focusing on Acanthaceae have been conducted, 88 species distributed in 14 genera are recorded (Flora e Funga do Brasil 2020, continuously updated).
Members of Acanthaceae can grow as lianas, herbs, or rarely trees.Most species have simple and opposite leaves, and cystoliths are present in some groups, such as Ruellieae.The inflorescences are morphologically diverse and considered one of the more taxonomically useful features of the group.The flowers are hermaphroditic, generally colorful and showy, the corolla is sympetalous, the stamens are more frequently 2 or 4 and epipetalous, and the ovary is superior (Wasshausen & Wood 2004;McDade et al. 2008;Braz & Azevedo 2016).
Flora brasiliensis (Nees 1847a) is still the only family-wide study of Brazilian Acanthaceae but it lacks an identification key.Many changes in genus and species delimitation have occurred since the XIX century and a large number of new species were described in the past decade in South America and Brazil (Kameyama 2008;Braz & Monteiro 2006;Côrtes & Rapini 2011;Wood 2012;Indriunas & Kameyama 2012;Wasshausen 2013;Alcantara et al. 2020), which indicates the need for new taxonomic studies of Brazilian Acanthaceae.Compared to other large Angiosperm families, relatively few studies focused on local floras have been published for Acanthaceae in Brazil, among these, most were developed in areas of Atlantic forest (e.g., Wasshausen & Smith 1969;Harvey & Wasshausen 1995;Braz et al. 2002;Kameyama 1995Kameyama , 2003Kameyama , 2006Kameyama , 2009;;Silva et al. 2010;Côrtes & Rapini 2013;Monteiro et al. 2018;Macedo et al. 2020;Hammes et al. 2021;Alcantara & Alves 2022), and despite presumedly presenting a high number of species and genera (Flora e Funga do Brasil 2020, continuously updated), studies on Acanthaceae in the Central-West region are even more scarce (Rodrigues 2017;Sartin 2015;Vilar 2009).
The present study is a taxonomic survey of the species of Acanthaceae in the Cuiabá lowlands, an area that includes a wide range of habitats where the diversity of the family has never been al.2016 ;Vilar 2009;Wasshausen & Wood 2004;Oliveira & Andrade 2000;Schmidt-Lebuhn et al. 2007;Zanatta 2019;Alcantara & Alves 2022), and comparison with photographs of type specimens when available online (Tropics, JStorPlants, Reflora).The specimens were deposited in the UFMT herbarium, and duplicates were sent to RB and SP (acronyms follow Thiers, continuously updated).Acanthaceae specimens previously collected in the study area and deposited in herbarium collections were analyzed, identified, and included in the examined material.

Results and Discussion
In this study we record 31 species of Acanthaceae in the Cuiabá lowlands.The species are distributed in 12 genera (Aphelandra, Dicliptera, Dyschoriste, Elytraria, Hygrophila, Justicia, Lepidagathis, Mendoncia, Pseuderanthemum, Ruellia, Staurogyne, and Stenandrium), the most diverse being Justicia (10 species) and Ruellia (eight species).Although the studied area represents only 9.4% of the area of the state of Mato Grosso, the number of species represents approximately 36% of the total of Acanthaceae species recorded in the state (Flora e Funga do Brasil 2020, continuously updated).This study also contributes with five new records for the flora of Mato Grosso: Dicliptera squarrosa Nees (1847a: 161), Dyschoriste schottiana (Nees) Kobuski (1928: 30), Ruellia blechum L. (1759: 1120), R. jussieuoides Schltdl. & Cham. (1831: 370) and R. trachyphylla Lindau (1898: 46).Most species in the area have their flowering and fruiting period in the dry season (June-October).Areas of shaded forest (mostly "cerradão" and gallery forests) are more diverse than open areas such as cerrado s.s. and campos rupestres (20 species vs. 11 species).Based on observation, the most frequent genera are Justicia and Ruellia in forest areas, and Ruellia and Stenandrium in Cerrado s.s..
The municipalities with the largest number of species were Cuiabá (13 species) and Chapada dos Guimarães (11 species), showing a strongly biased historical collection effort in the vicinity of the Universidade Federal do Mato Grosso campus.Only a single species was recorded for Acorizal, Campo Verde, and Planalto da Serra.This indicates that, even with our own collection effort, field work is still needed in these areas, which is impaired by scarce funding, difficult access and the lack of research infrastructure.Similarly, biased results were reported by Siqueira et al. (2014) and Pessoa et al. (2022) for orchids.
Most of the species recorded in the area are endemic to South America (24 species, 75%), among these, seven (ca. 22%) are endemic to Brazil: Dyschoriste schottiana, Justicia lavandulifolia Pohl ex Nees (1847b: 348), J. rectiflora (Lindau) V.A. Graham (988: 614), Ruellia neesiana Lindau (1895: 310), R. costata Lindau (1900: 195), R. trachyphylla, and Stenandrium hirsutum Nees & Mart (1847a: 77).Only three species have their distribution restricted to the Central-West Region: J. rectiflora (Lindau) V.A.W. Graham (1988: 614), R. neesiana and R. trachyphylla.There are one   (1903: 633), that, although occurring in other countries, are recorded in Brazil only in the state of Mato Grosso (Flora e Funga do Brasil 2020, continuously updated).All species have collections records in the Cerrado, 12 species occur exclusively in the Cerrado, 11 species occur both in the Cerrado and Amazon and seven species have records in both the Cerrado and Pantanal (Flora e Funga do Brasil 2020, continuously updated).Based on the evidence for Acanthaceae, we can describe the Cuiabá lowlands as an ecotone zone, and although most recorded species have wide ranges, the presence of restricted species or only with confirmed records in Brazil in the state of Mato Grosso highlights the importance of the area for conservation.
The number of species found (31) is higher than that found in other taxonomic studies on Acanthaceae in surrounding areas.Vilar (2009) found 28 in Distrito Federal and Silva & Bonadeu (2019) found 11 species in Colorado do Oeste, in the state of Rondônia.It is important to highlight that a long-term plant taxonomy project has been conducted in Distrito Federal (Cavalcanti & Batista 2009, 2010;Cavalcanti & Silva 2011;Cavalcanti & Dias 2012).The situation for Mato Grosso and the Cuiabá lowlands is the opposite, the area has been neglected by the botanical community in the last century.Our results instigate new studies in the area and show potential unknown plant diversity in the state.We suggest further studies in the area to increase the knowledge of its interesting flora.
Dicliptera squarrosa can easily be confused with D. sexangularis, differing from it by the axillary inflorescence (vs.terminal) and by its anthers with strongly asymmetrical thecae (vs.symmetrical).The species has eight synonyms (BFG 2015(BFG , 2018)), reflecting wide morphological variation for this species.It was collected in a forested area in the study region.Kobuski, Ann. Missouri Bot. Gard. 15: 30. 1928.
Elytraria imbricata is very distinct among the species of Acanthaceae in the study area by the small flowers that are only comparable in size with J. comata, and from which it can be distinguished by the stem branch shape (cylindrical vs. quadrangular), and the blueish purple corolla (vs.white with purple dots).It was collected in open disturbed areas.Nees & T. Nees, Pl. Hort. Bonn. Icon.: 7. 1824. Figure in: Monteiro et al. (2018).
Justicia asclepiadea can be confused in the study area with J. nodicaulis, differing by the linear-lanceolate floral bracts (vs.oblanceolate).It was collected in open areas.The species was recorded in Bolivia and Brazil (BFG 2015(BFG , 2018;;Wasshausen & Wood 2004).In Brazil it is found in the states of Mato Grosso and Goiás (BFG 2015(BFG , 2018)).In the study area we found it in Chapada dos Guimarães and Poconé.
Justicia chapadensis can be confused with J. warmingii in the study area but differs by the 5-lobed calyx (vs.4-lobed).It was collected in forested areas.

Justicia lavandulifolia
Justicia lavandulifolia is similar to J. laevilinguis in the study area but differs by the 4-lobed calyx (vs.5-lobed).It was collected in open areas.
Justicia nodicaulis can be confused with J. asclepiadea in the study area, differing by the oblanceolate floral bracts (vs.linear-lanceolate).It was collected in forested areas.

Zocal et al. 56 (UFMT).
The species was recorded in Argentina, Brazil, and Paraguay (BFG 2015(BFG , 2018;;Zuloaga et al. 2008).In Brazil it is found only in the state of Mato Grosso, but probably also occurs in Goiás, Mato Grosso do Sul and Tocantins (BFG 2015(BFG , 2018)).In the study area we found it in Várzea Grande.
Justicia rectiflora is easily distinguished from other Justicia in the study area by its long (1.8-3.6 cm long) and showy yellow corolla.It was collected in a forested area.
In the study area, Justicia warmingii can be confused with J. chapadensis but differs by the 4-lobed calyx (vs.5-lobed).It was collected in forested areas.
Lepidagathis floribunda is characterized by the reddish bracts that distinguish it from L. sessilifolia, from which it also differs by the acuminate leaf apex (vs.rounded, obtuse, or acute).In the study area, it was collected in forested areas, contrasting with L. sessilifolia, which is found in open areas.
Lepidagathis sessilifolia is characterized by the pink to purplish bracts that distinguish it from L. floribunda, from which it also differs by its rounded, obtuse, or acute leaf apex (vs.acuminate).In the study area it was collected in open environments, contrasting with L. floribunda, which is found in forested areas.Mart., Nov. Gen. Sp. Pl. 3: 24. 1829.
In the area, Pseuderanthemum congestum can be confused with Stenandrium hirsutum, but it is easily distinguished by the shape of the stem branches (cylindrical vs. quadrangular) and the 5-lobed calyx (vs. 4-lobed).It was collected in forested areas.
Ruellia blechum is easily distinguished from other species of Ruellia in the study area by the ovate to wide-elliptical bracts (vs.lanceolate or elliptical).It was collected in open and disturbed areas.
Ruellia brevifolia is easily distinguished from other species of Ruellia in the study area by its red flowers.Among the other red-flowered species in the area, it differs from two species of Dicliptera by the urceolate corolla (vs.2-labiate), and from Aphelandra longiflora by the shape of the stem branches (quadrangular vs. cylindrical).It was collected in open and forested areas.Lindau, Symb. Antill. 2(2): 195. 1900.
The species has 10 synonyms (BFG 2015(BFG , 2018)), reflecting wide morphological variation.In the study area, it can be confused with R. trachyphylla, from which it differs by leaf shape (ovate-lanceolate, elliptical, oblanceolate or obovate vs. narrow-lanceolate to narrow-elliptic) and shorter calyx (≤ 0.9 vs. ≥ 1.2 cm long).It is the most common species of Acanthaceae in open areas, where we observed a wide variation in leaf shape.The species was recorded in Argentina, Bolivia, Brazil, Paraguay, and Uruguay (BFG 2015(BFG , 2018;;Wasshausen & Wood 2004;Zuloaga et al. 2008).In Brazil, it is recorded in the states of Mato Grosso and Mato Grosso do Sul (BFG 2015(BFG , 2018)).In the study area, we found it in Cuiabá.

Ruellia hygrophila
Ruellia hygrophila is easily distinguished from other species of Ruellia in the study area by the leaves clustered in a rosette (vs.distributed along the stem).It was collected in open and disturbed areas.Schltdl. & Cham., Linnaea 6: 370. 1831.
In the study area, Ruellia jussieuoides can be confused with R. costata, from which it differs by the longer corolla tube (≥ 5.5 vs. ≤ 3.9).It was collected in a forested area.
Ruellia neesiana has the longest corolla tube among the species in the study area, but R. jussieuoides can sometimes overlap in length, from which R. neesiana can be distinguished by its longer calyx (≥ 2.2 vs. ≤ 2 cm long).It was collected in open areas.
The species is endemic to Brazil and recorded in the state of Goiás (BFG 2015(BFG , 2018)).We present the first record of the species in Mato Grosso, where it is found in Poconé.
Ruellia trachyphylla can be confused in the study area with R. geminiflora, from which it differs by the leaf shape (narrow-lanceolate to narrowelliptic vs. ovate-lanceolate, elliptical, oblanceolate or obovate) and longer calyx (≥ 1.2 vs. ≤ 0.9 cm long).It was collected in open areas.
The species is endemic to Brazil and recorded in the state of Amazonas, Mato Grosso and Pará (BFG 2015(BFG , 2018)).In the study area we found it in Poconé and Santo Antônio do Leverger.

Stenandrium hirsutum
The species is endemic to Brazil and recorded in the state of Goiás, Mato Grosso, Minas Gerais, and São Paulo (BFG 2015(BFG , 2018)).In the study area, we found it in Nova Brasilândia and Várzea Grande.
In the study area, Stenandrium hirsutum can be confused with Pseuderanthemum congestum, from which it can be distinguished by the shape of the stem branches (quadrangular vs. cylindrical) and the 4-lobed calyx (vs.5-lobed).It was collected in open areas.Nees, Fl. bras. 9: 75. 1847a.
Stenandrium pohlii can be easily distinguished from other Stenandrium species in the area by the rosette leaves (vs.distributed along the elongated stem).It was collected in open areas.

Figure 1
Figure 1 -a-c.Map showing the location of the study area -a.Latin America highlighting Brazil; b.Brazil highlighting Mato Grosso state; c.Mato Grosso state highlighting the Cuiabá Lowlands.
Examined material: