Taxonomic synopsis of Caryomene (Menispermaceae) in the Brazilian Amazon

ABSTRACT Caryomene comprises five species distributed in South America. For more than half a century, the genus has not received taxonomic treatment. However, many recent collections were carried out in Amazonia and new occurrences need to be inserted. The present study aimed to elaborate a synoptic treatment of the species collected in Amazonia and botanical specimens from 32 herbaria. The results pointed out the presence of five species in Amazonia, of which C. grandifolia, C. foveolada, C. olivascens and C. prumnoides are new occurrences. The states of Amazonas and Pará represent the two main distribution centers for the species. The fruit characters are the ones that best separate the species. An identification key, descriptions and illustrations of the species that occur in Amazonia are presented.


INTRODUCTION
The family Menispermaceae Jussieu comprises 72 genera and approximately 526 species, distributed mainly in the tropical regions of the world (Ortiz et al. 2016).In Brazil, it is represented by 15 genera, 108 species (29 endemic), six subspecies and seven varieties (BFG 2015).
In Menispermaceae, Caryomene Barneby & Krukoff (five species) is positioned within the tribe Anomospermeae Miers, and subfamily Menispermoideae Wang & Chen (Ortiz et al. 2016;Sousa 2016).The genus is easy to recognize due to the endocarp in the shape of an inverted "U," smooth or foveolate externally and the endosperm without an external tegumentary membrane (Barneby and Krukoff 1971;Sousa 2016).The representatives of Caryomene are distributed in South America, occurring in Bolivia, Brazil, Guyana, French Guiana, Suriname, Peru and Venezuela (Barneby 2001;MBG 2022).In Brazil, it is represented by five species (two endemic) distributed in the Amazonian phytogeographical domain, in the northern states of Amazonas, Pará and Rondônia, and the northeastern state of Maranhão (Sousa 2016;BFG 2015).
The morphological delimitation in this genus is very complex, which has resulted in confusing species with each other and with other genera (Sousa 2016).Some species treatments are incomplete, with only the description of staminate flowers or fruit, which makes it difficult to elucidate more precisely which characters are better suited for species separation (Sousa 2016).
The objective of this study was to produce an updated taxonomic treatment of Caryomene in the Brazilian Amazon, which better identifies the species and improves the knowledge about the genus in South America.

MATERIAL AND METHODS
The study was based on type material and additional specimens of Caryomene in Amazonia, mainly in the following herbaria: F, HERBAM, IAN, INPA, MG, NY, P, R, RB, UFRR, U and US (abbreviations based on Thiers 2022, continuously updated).We conducted field trips in all the Brazilian Amazonian states between January 2021 and October 2022 in order to collect fertile specimens, both in the rainy and dry seasons.Representative specimens were described and illustrated with the aid of a stereomicroscope (Leica EZ4D).The species descriptions are based on the material studied.Morphological terms follow Hickey (1973), Rizzini (1977), Jacques (2009), Ortiz et al. (2007), Wefferling et al. (2013), Ortiz et al. (2016) and Sousa (2016).Species identifications are based on the analysis of 15 types and identification keys.The following abbreviations were used: fl (flower), fr (fruit) and sn (without a number).Scanning electron microscopy (SEM) images were used to analyze and determine the types of indument and the surfaces of reproductive structures of representative specimens.The reproductive structures (flower and fruit) were cut into fragments or kept intact and were fixed, dehydrated, dried in a critical point, in an oven or under an incident light source and mounted on double-sided tape adhered to a metallic support of one cm in diameter (stub) (Bozzola and Russell 1992).After assembling the material, it was metallized with gold for two and a half minutes.The images were obtained through an electronic microscope LEO model 1450 VP at 10 KV of acceleration and recorded in digital mode, in "tiff" format.Barneby & Krukoff, Mem. New York Bot . Gard. 22(2): 52. 1971.Figure 1 (a-i) Liana 2.5-5 cm diam., scandent; rhytidome striated or fissured.Leaves alternate, distichous or spiral, basifixed; venation basal actinodromous or venation mixed (basalsuprabasal actinodromous); primary veins 5, palmatinerved ou palmati-plinerved, convex on the abaxial surface.Petiole cylindrical or flat; basal pulvinus conspicuously swollen; apical pulvinus inconspicuous.Staminate flowers diclamid; sepals 6, biseriate; petals 6, smaller than the stamens, fleshy, involute, forming a pseudo disc around the stamen; stamens 6, free; anthers transversely dehiscent.Pistillate flowers absent.Drupes in pairs or solitary in the infructescence; epicarp coriaceous; mesocarp fleshy or slender; endocarp in the shape of an inverted "U," woody, smooth or foveolate externally; endosperm ruminate in the shape of an inverted "U," without an external tegumentary membrane; condyle linear, vertical to the longitudinal axis of the seed; embryo curved in the mid region.

Caryomene
Caryomene differs from the other Anomospermeae by the organization of the endocarp, which is smooth or foveolate on the outer surface and has a row of cavities circumscribed by lamelliform teeth.In addition to the reproductive character mentioned above, Caryomene is distinguished mainly by absence of an outer membrane involving the endosperm.
Identification key to the species of Caryomene in the Brazilian Amazon Distribution: French Guiana and Brazil (Barneby and Krukoff 1971;MBG 2022).In Brazil, this species occurs only in the state of Pará (Barneby and Krukoff 1971;BFG 2015;Sousa 2016).It is peculiarly found in terra firme forest, as also reported by BFG (2015).The species was found with fruit in February, September and December.

DISCUSSION
According to Barneby and Krukoff (1971), Caryomene can be vegetatively distinguished from most Amazonian Menispermaceae by its hollow stem and by the presence of papillae inconspicuous in the midrib of the abaxial leaf surface.Sousa (2016) added that the species of the genus have petioles with wider pulvinus only at the base.In addition to the vegetative characters described for the genus in the present treatment, Caryomene can be distinguished by reproductive characters based on size and organization of the fruit: the drupes are large, endocarp thickly woody with thick-walled and horizontal dentiform plates and endosperm with no membrane lamellae (Barneby and Krukoff 1971;Sousa 2016).
The species of Caryomene are commonly confused with those of Abuta Aubl.and Anomospermum Miers, and, although these species are difficult to differentiate by their vegetative characters, they can easily be distinguished by their fruits.The drupes of Caryomene have a larger endocarp, with horizontal dentiform plates and endosperm without a membrane, since the lamellae have no exterior sac, while Anomospermum and Abuta have drupes with smaller endocarps, without horizontal dentiform plates and the endosperm composed of plates separated by membranous (Barneby and Krukoff 1971;Sousa 2016).According to the latter authors, the three genera have similar embryos, liner-vermiform, with appressed cotyledons and the endosperm folded, however the endosperm of Caryomene and Abuta forms an inverted "U", while Anomospermum has the endosperm curved in the shape of a "J".Although Caryomene and Abuta have endosperm with the same shape, they are easily differentiated, as Caryomene has petals and the endocarp is externally smooth or transversely foveolate and internally composed of lamelliform teeth, usually surrounded by interparietal cavities, while Abuta does not have petals and the endocarp it has three grooves on the outer surface of the testa, one dorsal and two laterals, and it is always smooth and entire inside.For the Amazon, this study registered the occurrence of five species with fruits fundamentally differing in their inner structure and vegetative characters that help separate the species.
Caryomene prumnoides was the first species of the genus discovered, although not the first described, chosen by Barneby and Krukoff (1971) to be the generic type of Caryomene, mainly due to the abundance of fruits.This species is well defined and easily distinguishable from other congeners by the cordiform leaf blade with a cordate or subtruncate base and exclusively by the endocarp composed of two walls and with the smooth outer surface.
Caryomene glaucescens is the only species of the genus that has a capitate condyle.According to Barneby and Krukoff (1971) this species has similarity in the leaf form with C. olivascens.However, in addition to this latter vegetative character, C. glaucescens is distinguished by presenting cylindrical petioles, puberulent abaxial surface, repand margin, prominent secondary veins on the adaxial surface, subglobous drupes, 2-4.5-mm thick, fleshy mesocarp and a double-walled, externally smooth endocarp, whereas C. olivascens has flat petioles, strigose abaxial surface, rectilinear margins, secondary veins impressed on the adaxial surface, obovoid drupes, with an almost 0-mm thick, mucilaginous mesocarp, endocarp with one wall, externally foveolate, and with claviform condyle.Barneby, when analyzing the material collected in Serra do Navio (Amapá state), suspected that it was a new species due to differences in the cavity of the endocarp, but this character is not enough to maintain it as an independent taxon, since morphological analysis revealed that it was C. olivascens, due to the similarity in diagnostic characters.
Of the five species of Caryomene analized, only C. foveolata and C. grandifolia have alternate leaves arranged on opposite sides (distichous).However, C. foveolata is easily distinguishing by presenting non canaliculated basal pulvinus, 6-15.5-cmlong leaf blades, rectilinear leaf margins and secondary veins diverging from the lower third of the blade, while C. grandifolia is recognized by having canaliculated basal pulvinus, 17.3-29.2-cmlong leaf blades, repand leaf margins and secondary veins diverging from the median region of the blade (Sousa 2016).
Among the species studied, C. grandifolia is easily identified by the large size of the leaf blade and striated rhytidome, as corroborated by Sousa (2016).Caryomene glaucescens and C. olivascens are endemic to Brazil.Caryomene foveolata is the most common in the Amazon.

CONCLUSIONS
The Amazon Rainforest is the main center of diversity for Caryomene species.Caryomene foveolata is the most common in the Brazilian Amazon.The states of Amazonas and Pará are the most species rich.There was an expansion in the geographic distribution of the genus with the inclusion of three new occurrences in the Brazilian Amazon: C. grandifolia in Pará, C. olivascens in Amapá, C. foveolada and C. prumnoides in Mato Grosso.Most species arecords occurred in terra firme forest .The leaf venation and fruit characters were the main features used to separate the species.A study of this scope will contribute to conservationist policies, use projects, management, recovery and environmental monitoring.

Figure 1 .
Figure 1.Scanning electron microscopy and morphological characterization of fruit of Caryomene Barneby & Krukoff.A -Outer surface of the sepal; B -Inner surface of the sepal; C -Sericeous indument of the sepal; D -Petals forming a pseudo disc around the stamens; E -Stamen; F -Ruminate endosperm; G -Drupe; H -Outer surface of the endocarp; I -Endocarp in longitudinal section showing the endosperm, embryo and the condyle.This figure is in color in the electronic version.