Peperomia is one of the largest genera of basal angiosperms, with about 1,600 species, distributed pantropically. The Brazilian oceanic island of Trindade is located about 1,200km off the Brazilian coast; its maximum altitude is 620ma.s.l. and its area is 9.28km². Among the 113 species of vascular plants reported for Trindade Island there are two species of Peperomia: Peperomia beckeri, an endemic species known only from the type specimen; and Peperomia glabella.We re-evaluated specimens attributed to P. glabella from Trindade Island and compared them to specimens from the continent. The comparison included morphological analyses of the vegetative and reproductive organs, and a molecular phylogenetic study using the molecular markers trnK/matK and ITS. The trnK/matK marker showed significant differences between Peperomia from the mainland and Trindade. Together, these studies showed that the Peperomia occurring on Trindade is a species that differs both from those previously recorded on Trindade Island and from those on the continent, leading us to describe a new species. Peperomia segregata is endemic to Trindade, and would likely be considered critically endangered according to the IUCN criteria.

Ataxonomic revision of Trisetum sect. Acrospelion is presented.We include descriptions and synonyms of each taxon from a study of 670 vouchers from 45 herbaria. Detailed morphometric descriptions, illustrations, distribution maps, identification key, and habitat data are given for each taxon. Twelve names are lectotypified: Aira halleri Honck., Avena argentea Willd., Avena brevifolia Host, Avena daenensis Boiss., Avena distichophylla Vill., Trisetum argenteum var. parviflorum Parl., Trisetum cavanillesianum Borja & Font Quer, Trisetum distichophyllum subsp. delphinense Beauverd, Trisetum macrotrichum Hack., Trisetum rigidum var. molle Somm. & Levier, Trisetum rigidum var. ovale Somm. & Levier, and Trisetum teberdense var. brevifolium Kharadze. We recognize seven species of Trisetum into the section, which is endemic to Eurasia: T. argenteum, T. buschianum Seredin, T. distichophyllum (Vill.) P. Beauv., T. macrotrichum, T. rigidum (M. Bieb.) Roem. & Schult., T. tamonanteae Marrero Rodr. & S. Scholz, and T. velutinum Boiss. Morphometric variation of the main characters is shown by box plots. The highest diversity is located in the Caucasian Mountains and the Alps, where two species were found in each area. Additionally, one species is endemic to the Canary Islands, a second to southeastern Spain, and a third to the Carpathian Mountains. In contrast with some regional treatments, T. persicum Chrtek is considered a synonym of T. rigidum (M. Bieb.) Roem. & Schult., and T. cavanillesianum Borja & Font Quer a synonym of T. velutinum Boiss. Trisetum rigidum subsp. teberdense (Litv.) Tzvelev and T. buschianum subsp. transcaucasicum (Seredin)Mosul. are recognized as subspecies. Vegetative propagation has been observed for the first time in specimens of T. rigidum and T. velutinum.

An endemic morning glory of southwestern New Mexico, Ipomoea gilana, known only from the Black Range of the Gila National Forest, is described and distinguished from a close phylogenetic associate, Ipomoea orizabensis (Ipomoea series Tyrianthinae), from mid-elevation mountains (800–2,000 m) of Mexico and Central America. The new species resembles I. lindheimeri (Ipomoea section Pharbitis) superficially, but molecular studies indicate closer relationships with I. orizabensis. Ipomoea gilana has slightly succulent leaf blades, nocturnal anthesis, light blue corollas, slightly exserted, subequal stamens with filaments inserted 2 cm above the base of the corolla tube and three-locular capsules. Ipomoea orizabensis s. l. has membranous leaf blades, diurnal anthesis, ruddy magenta corollas with unequal, included stamens inserted less than 1 cm from the base of the corolla tube and two-locular capsules. The new species is illustrated and a table of differences between the three species is provided.

Cleome, as traditionally defined, is not monophyletic and we here work towards taxonomic revisions for the Cleomaceae where genera reflect morphologically diagnosable monophyletic groups based on previous phylogenetic studies. We provide morphological characters to distinguish eight genera of predominantly African distribution, four of which are new to science: Coalisina, Dipterygium, Gilgella, Kersia, Puccionia, Sieruela, Stylidocleome, and Thulinella. We present new combinations in these genera for 52 species, four subspecies, and seven varieties. Two hundred and thirteen nomenclatural synonyms (homotypic and heterotypic) are treated, as well as nine generic synonyms. Fifty-one lectotypes are designated and two neotypes are created. A key is provided for all 13 genera (native and introduced) found in Africa.

Novel molecular data and morphological studies have provided support for the segregation of numerous genera from Cleome s. l. (Cleomaceae). Corynandra has been proposed as a segregate genus including Indian and Australian species based on floral and seed morphology. Contrasting seed coat micro-morphology between Indian and Australian species included in Corynandra raised questions over the monophyly of that genus concept. Relationships among the Indian and Australian species remain unclear due to limited sampling in previous molecular analyses. We expanded the sampling of taxa from India and Australia in order to clarify relationships between these species and the circumscription of Corynandra. Comprehensive sampling of Indian and Australian species formed three well-supported clades based on analyses of molecular sequence data and we conclude that Corynandra is not related to the Australian species. The genus Arivela Raf. is reinstated for the majority of Australian species. The new genus Areocleome is described to accommodate the unusual Australian C4 species Cleome oxalidea. The following new combinations are made: Areocleome oxalidea, Arivela arenitensis, Arivela bundeica, Arivela cleomoides, Arivela insolata, Arivela kenneallyi, Arivela limmenensis, Arivela linophylla, Arivela lophosperma, Arivela microaustralica, Arivela tetrandra, Arivela uncifera, Corynandra aspera, and Corynandra simplicifolia. Arivela microphylla is raised to species level and provided with a new combination.

Ladenbergia shawistigma (Rubiaceae) is a new species from the Andean tepuis on the boundary of Loreto and San Martin departments in Peru. This new species is morphologically similar to L. moritziana and L. pauciflora, which are distributed in the Andean regions of Venezuela and Colombia, respectively. Ladenbergia shawistigma can be distinguished from these by the inflorescence resembling an umbelliform cyme with a short peduncle and three sessile flowers; hypanthium puberulous outside; small and deeply lobed calyx; and hirsute style. Ladenbergia shawistigma is only known from the Cordillera Escalera, Loreto, Peru.

Schlechteranthus subgenus Microphyllus is a recently erected subgenus, which is revised here for the first time. The subgenus is comprised of nine succulent species, including a new species S. parvus, and is endemic to the arid part of the Greater Cape Floristic Region. Schlechteranthus subgenus Microphyllus can be distinguished from subgenus Schlechteranthus by the smaller leaves (3.5–5.0 × 4–6 mm vs. 5–30 × 3.5–9.0 mm) and smaller capsules (2–6 × 2–6mmvs. 6–11 × 4–9 mm), with seven to nine locules and small closing bodies that block one third of the locule (vs. 10 to 12 locules and closing bodies that block three quarters of the locule). Differences in leaf shape, degree of fusion, and arrangement, as well as inflorescence and spine structure were identified as important characters in distinguishing species in the subgenus. Schlechteranthus parvus, S. pungens, S. spinescens, and S. stylosus all share the presence of spines, caducous bracteoles, and cymose inflorescences. Maps illustrating species richness hotspots within a quarter degree square were produced for the genus and subgenera respectively. A key to the subgenera in Schlechteranthus and a comprehensive taxonomic treatment of subgenus Microphyllus is presented, including a key to the species, descriptions, figures illustrating diagnostic characters, and distribution maps.

Gaps between molecular ages and fossils undermine the validity of time-calibrated molecular phylogenies. An example of the time gap surrounds the age of angiosperms' origin. We calculate molecular ages of the earliest flowering plant lineages using 22 fossil calibrations (101 genera, 40 families). Our results reveal the origin of angiosperms at the late Permian, ∼275 million years ago. Different prior probability curves of molecular age calculations on dense calibration point distributions had little effect on overall age estimates compared to the effects of altered calibration points. The same is true for reasonable root age constraints. We conclude that our age estimates based on multiple datasets, priors, and calibration points are robust and the true ages are likely between our extremes. Our results, when integrated with the ecophysiological evolution of early angiosperms, imply that the ecology of the earliest angiosperms is critical to understand the pre-Cretaceous evolution of flowering plants.

The present paper describes and illustrates two new species of Chusquea subg. Magnifoliae in Peru, C. longipedicellata and C. rugoloana. Keys for the identification of species, based on vegetative and reproductive characters, as well as a comparative table with morphological diagnostic features are included. Additional micromorphological characters of the spikelets and leaves are considered, and a complete description of foliar anatomy is presented. Also, some remarks about the characteristics of the phytogeographical regions and the ecology of these new species are provided.

Maytenus species are distributed in the New World from Argentina to the U. S. A. The genus delimitation has been controversial, especially in relation to the inclusion of Gymnosporia. Maytenus has been treated in a broad sense such that it was considered widely distributed in tropics and subtropics worldwide. Even in its current restricted circumscription, the genus remains paraphyletic with Fraunhofera and Plenckia nested within it. We increased taxon sampling relative to previous studies and sampled species representing the greatest morphological diversity from throughout the geographic distribution in order to confidently delimit monophyletic genera. The phylogenywas inferred using nuclear (ITS and 26S rDNA) and plastid (matK and trnL-F) gene regions together with morphological characters. The species currently recognized as Maytenus were resolved in three distinct clades. Delimitation of a single large genus, by including Fraunhofera and Plenckia within Maytenus, would result in a morphologically heterogeneous group. Instead we segregated Maytenus into two genera, re-established Tricerma, and maintain Fraunhofera and Plenckia as distinct genera. All of these genera are morphologically distinct from each other, primarily based on fruit characters. A total of 123 new combinations under the generic name Monteverdia are provided for species in the clade that does not contain the type of Maytenus.

The genus Cynometra (Leguminosae, Detarioideae) is a large, pantropical group of woody plants ranging in size from 5–50 m. While many recent advances have been made in higher level legume systematics, many large genera still require more study to test their monophyly. Further, its relationship to the much smaller Pacific genus Maniltoa is unclear. Here we present the first broadly-sampled phylogeny of Cynometra and Maniltoa, based on molecular data from three chloroplast loci: matK, the trnL intron, and the trnL intergenic spacer. Our analyses indicate that Cynometra is not monophyletic as currently circumscribed, as several researchers had previously suspected. We recover two strongly supported clades of Cynometra s. l.; one that is most closely related to a clade consisting of the genera Dicymbe and Polystemonanthus and is composed of exclusively African taxa, and another clade that is pantropical and is nested in a larger clade with the Scorodolphoeus group and the genera Normandiodendron, Neochevalierodendron, and Zenkerella. Futhermore, the genus Maniltoa is nested within the pantropical Cynometra clade and is also non-monophyletic. The two clades are each supported by several morphological characters that can be used to distinguish between them (e.g. inflorescence structure, pedicel articulation, fruit dehiscence). These results will be used to modify the classification by moving the relevant African taxa to a new genus and placing Maniltoa in synonymy with Cynometra.

Species delimitation in Pinaceae is often challenged by limited morphological differentiation and introgression. In Tsuga (hemlocks), species delimitation has been most challenging among northeastern Asian taxa, where the species are weakly marked morphologically and range in number from three to five in previous studies. Two low-copy nuclear four-coumarase-ligase (4CL) genes andmorphology strongly support a clade of the Japanese endemic T. diversifolia and T. sieboldii from Japan and Ulleung island (Ulleungdo) in Korea. This clade is here referred to as the oceanic hemlocks. 4CL strongly supports a sister-group relationship of the widespread northeastern Asian T. chinensis and eastern North American T. caroliniana. In contrast, chloroplast genomes, which are markedly reduced in Tsuga and relatives, strongly support Japanese T. sieboldii as sister to T. chinensis and moderately support T. caroliniana as sister to a clade of T. diversifolia and hemlocks fromUlleungdo. These divergent topologies suggest chloroplast capture of T. chinensis by Japanese T. sieboldii. Ulleungdo hemlocks are distinct from other northeastern Asian species in leaf and cone morphology and phenologically in common-garden observations. We therefore describe these hemlocks as a new species, T. ulleungensis.

The moonwort genus, Botrychium s. s., includes diploid and polyploid taxa that occur primarily in the northern hemisphere. Their evolutionary history, morphologically cryptic taxa and deep divergence of the family in the phylogeny of ferns has long fascinated pteridologists. Previous molecular studies did not include a complete taxonomic sampling of the taxa in the genus, nor multiple specimens from throughout the known geographical range of each taxon. Therefore, to investigate evolutionary relationships of the major clades of Botrychium s. s., we increased both taxonomic representativeness (multiple accessions per taxa), as well as phylogenetic resolution by including additional new chloroplast markers. To confirm identification and provide evidence from both maternal and paternal parentage of allopolyploids, we also included specimens that have been characterized by allozyme profiles determined by electrophoretic analysis of 20 nuclear enzyme loci for each taxon. We analyzed four chloroplast regions (matK intron, trnH^GUG—psbA, andtrnL^UAA—trnF^GAA intergenic spacers, and rpL16 intron region) of 365 specimens fromAsia, Europe, North America, Oceania, and South America, sampling the geographical range of 34 of 35 accepted Botrychium s. s. taxa and thirteen putatively new taxa. We conducted a phylogenetic analysis of maternal lineages based on 2,385 aligned nucleotides using maximum likelihood and Bayesian inference to explore genetic diversity and phylogenetic relationships among taxa. We found strong support for themonophyly of three major clades: Lanceolatum, Lunaria, and Simplex-Campestre, and resolved 15 subclades. Our results suggest multiple origins for at least four polyploid taxa (B. boreale, B. michiganense, B. yaaxudakeit, and B. watertonense). The Simplex-Campestre clade had the largest number of species, despite having a similar total number of haplotypes as the Lunaria clade (62 and 59, respectively), which has the broadest worldwide distribution. In total, our new molecular phylogeny comprises 47 taxa, of which thirteen are discussed for possible taxonomic recognition.

Otatea is one of the five genera recognized in Guaduinae, a Neotropical subtribe belonging to tribe Bambuseae (tropical woody bamboos) and subfamily Bambusoideae (Poaceae). Otatea currently has 11 described species, all of which are adapted to dry habitats, and all of which are present in Mexico. Only Otatea fimbriata is reported for Mexico, Central America, and Colombia. A previous phylogenetic analysis demonstrated that the only Colombian population of O. fimbriata (located in Norte de Santander) was closely related to the rest of this widespread species. However, further morphological evidence from the recent flowering of cultivated plants from the wild Colombian population allowed its unambiguous separation from the rest of the populations of O. fimbriata. The Colombian population differs from O. fimbriata in having short and few oral setae on the culm leaves, longer spikelets with five to seven florets per spikelet, and longer glumes, lemmas, and paleas. This new evidence therefore leads us to propose a new species endemic to Colombia; in this manuscript, we describe and illustrate O. colombiana and compare it with its closely related species, O. fimbriata. Only a single locality, located in a non-protected area, is known for O. colombiana with the single population consisting of a few hundred plants. Thus we suggest that if a Red List evaluation of this species were performed, it would be assigned to the Critically Endangered category, following the categories and criteria of the International Union of Conservation of Nature's Red List.

Aeschynomene fluvialis, a new species from the North region of Brazil, is described and illustrated here and has its morphological relationships, systematic position, geographic distribution, ecology, conservation status, and period of flowering and fruiting provided. It can be differentiated from its congeners, especially A. pratensis and A. montevidensis, by a set of characters such as cespitose habit, venation and margin of leaflets, size of flowers, diadelphous androecium, and loment characters. A key to identify all Aeschynomene species with medifixed stipules, fruit with articles separated by septa, and bilabiate calyx, which are common in swampy or aquatic environments from the North region of Brazil, is also provided.

Vauquelinia corymbosa (Pyreae, Rosaceae) is a shrubby sclerophyllous species largely restricted to the Chihuahuan Desert, distributed from Texas, Coahuila, and along the Sierra Madre Oriental to Hidalgo. According to a previous taxonomic revision, it comprises six subspecies. Vauquelinia corymbosa has noteworthy morphological variation, mostly in leaf characters, and the majority of its subspecies are restricted to certain areas of the desert. In this study, based on 16 morphometric characters and four anatomical characters collected from 201 specimens of the six subspecies throughout their distribution range,we ran a number of uni-, multivariate, and phylogenetic analyses to determine how many species can be recognized in this species complex. We also analyzed the gaps in morphology across geography to identify whether gaps in morphometric characters are indeed useful to separate species or if they are the result of variation related to geography. The results of the analyses coincided in recognizing that subsp. angustifolia should be considered a separate species and that the remaining subspecies are part of Vauquelinia corymbosa with remarkable morphological variation. Vauquelinia angustifolia has diagnostic characters such as very narrow leaves (0.4–0.6 cm at the middle and 0.2–0.4 cm at the base) and short petioles (1–1.5 cm) and it is restricted to the northeastern region of the Chihuahuan Desert.

This morphologically-based study of the New World genus Cuphea section Brachyandra is part of a revision-in-progress of the 1903 monograph of Cuphea by E. Koehne. The section is narrowly defined here as comprising annual and perennial herbs and subshrubs with floral tubes 3–9(-11.5) mm long, stamens deeply inserted, and anthers positioned proximal to the sinuses of the sepals. Thirteen species and three varieties are recognized. Four species are widely distributed in the New World, five are endemic to the Caribbean region, and four species and two varieties are restricted to South America. The revision includes a morphological overview, seed oil composition and chromosome number data, a key to the species, species descriptions, illustrations, and distribution maps. Neotypes are designated for: Cuphea balsamona Cham. and Schltdl., C. fuscinervis Koehne, C. urens Koehne, and Lythrum carthagenense Jacq. Lectotypes are designated for: Cuphea section Brachyandra Koehne, C.calophylla Cham. and Schltdl., C. calophylla var. calophylla f. deformis Koehne, C. orthodisca Koehne, C. anisophylla Hemsl., C. mesostemon Koehne, C. elliptica Koehne, and C. pustulata Koehne. New combinations are: C. calophylla var. fuscinervis (Koehne) S. A. Graham and C. calophylla var. mesostemon (Koehne) S. A. Graham. Relationships of the species are discussed based on evidence from morphology and available molecular phylogenetic studies. The section, although narrowly defined, remains polyphyletic. It is represented by at least three lineages differing in pollen and seed morphology, and occurring in three of the five major clades of the genus. Two of the three lineages, with South American origins, have given rise to the five species of sect. Brachyandra endemic to the Antilles.

Two major obstacles to quantifying biodiversity are reticulate evolution and the evolution of genetically distinct but morphologically overlapping cryptic species. The Spiranthes cernua species complex (Orchidaceae) has defied satisfactory species delineation, often described as intractable, due to morphological variability within species, overall morphological similarity between species, possible cryptic speciation, and suspected hybridization. Weutilized low copy nuclear, nuclear ribosomal, and chloroplast molecular phylogenetic datasets, in addition to expansive field and herbarium research, to clarify long-standing questions regarding species boundaries within the S. cernua species complex. Our results justify: 1) narrowing the concept of S. cernua; 2) the description of a new cryptic species, Spiranthes arcisepala; 3) the description of a new geographically restricted species of cryptic and ancient hybrid origin, Spiranthes niklasii (S. cernua × S. ovalis); 4) a new combination for a biogeographically specific cryptic species of ancient hybrid origin, Spiranthes incurva (S. cernua×S. magnicamporum); and 5) the description of a new localized hybrid, Spiranthes ×kapnosperia (S. cernua × S. ochroleuca). We also propose formal synonymization of federally endangered Spiranthes parksii under S. cernua s. s. Our research clarifies species boundaries within this challenging group, and is the first to use molecular phylogenetic data to support hybridization as an evolutionary force within the S. cernua species complex.

Cephalocereus, Neobuxbaumia, and Pseudomitrocereus (Cactaceae, Cactoideae, Echinocereeae) are related genera of columnar cacti native to Mexico with current ambiguous circumscription. We applied maximum parsimony and Bayesian inference methods to reconstruct the phylogeny of the Cephalocereus group using molecular data from seven chloroplast regions (petL-psbE, psbA-trnH, rpl16, rpl32-trnLUAG, trnL-F, trnQrps16, andycf1), simple coded indels, and 46 structural characters. The Cephalocereus group was recovered as monophyletic with high support values, whereas Neobuxbaumia appeared as paraphyletic, due to the polyphyly of Cephalocereus and the derived position of Pseudomitrocereus within this group. Topology was mostly congruent among the different phylogenetic methods explored, and three pervasive clades were observed. Two structural characters were confirmed as synapomorphies for the Cephalocereus group: prismatic crystals in the dermal system and a perianth woody cap persistent in the fruit. The derived position of Pseudomitrocereus suggests that new hypotheses must be explored regarding the possible hybrid origin of this taxon. We propose the transfer of all species of Neobuxbaumia, Cephalocereus, and Pseudomitrocereus to a single genus, in which Cephalocereus takes priority over the other names. Based on our results, a new circumscription for Cephalocereus is proposed, including a taxonomic synthesis, two new combinations (Cephalocereus multiareolatus and Cephalocereus sanchezmejoradae), and a key for species.

A new species of Passiflora (supersection Laurifolia, series Laurifoliae) from the Andean region of Colombia is described and illustrated using morphological descriptors analysis. This species is closely related to P. popenovii Killip and can be recognized mainly by its purple stem, leaf size (125–165 × 50–79 mm), biglandular petioles, pedicel length (8–10 mm), bracts light green, glandless, flowers length (28–30 mm), corona filaments in five series, minute-filiform inner filaments length (1–4 mm), fimbriate purplish operculum margin, staminal filaments length (6.8–7.1 mm), ovary glabrous, yellow mature fruits mottled with irregular white dots, lightly pubescent, and total soluble solids content in fruit juice (13.5%–14.3%). The newly identified species P. gustaviana grows on the slopes of high mountains between 1,900 and 2,309mabove sea level, with an annual mean temperature of 16.2°C. It is considered a new endemic species of Colombia and may be regarded as endangered (EN) because of its limited occurrence. This new species constitutes an important unexploited genetic resource useful for the improvement of cultivated Passiflora species.

A taxonomic revision of Trisetum sect. Sibirica is presented. We include descriptions and synonyms of each taxon from a study of 450 vouchers from 35 herbaria. Detailed morphometric descriptions, illustrations, distribution maps, identification key, and habitat data are given for each taxon. An identification key for all taxa of Trisetum sect. Sibirica is provided. Morphometric variation of the main characters is shown by box plots. Six names are lectotypified. We recognize six species of Trisetum in the section: T. aeneum, T. bifidum, T. henryi, T. scitulum, T. sibiricum, and T. turcicum. Two infraspecific taxa of T. sibiricum are recognized (T. sibiricum subsp. sibiricum and T. sibiricum subsp. litorale), while T. pauciflorum, T. sikkimense, and T. umbratile are reduced to synonyms of T. sibiricum subsp. sibiricum. Four of the six species of Trisetum sect. Sibirica are endemic to Eastern Asia and New Guinea, while T. turcicum grows in Turkey, the Caucasus, and Northern Iran, and T. sibiricum is widespread from Eastern Europe to Alaska and Canada.

Croton longicarpus (Euphorbiaceae), a new species from southern Brazil, is here described and illustrated. The new species occurs in open vegetation and at the edges of Araucaria forest. The analysis of herbarium collections and observations from populations in the field indicate that the species has characters in common with members of Croton section Lamprocroton. The new species differs from other species in this section by its unusually elongated ovary and fruit, the narrowly spatulate sepals of the pistillate flowers, and long inflorescences.

Miconia bradeana is described from the state of Rio de Janeiro, in southeastern Brazil. It is endemic to the municipality of Santa Maria Madalena and to the Brazilian Atlantic Forest, occurring in dense montane tropical rainforest. The main diagnostic characteristics of this new species are the rigid-membranaceous to chartaceous and narrowly elliptic to lanceolate leaves, 5(-6)-merous flowers, well-defined, deltoid calyx lobes, apiculate petals, stamens 14–16, connectives with dorsal-basal, usually glandulose appendages, and glandulose ovary apex. Miconia bradeana is an endangered (EN) species.

Buddleja bordignonii is a new species from southern Brazil. This species belongs to Buddleja sect. Buddleja ser. Thyrsoides, and is morphologically similar to B. cuneata, from which it can be distinguished by its leaves with attenuate base, leaf shape and length/width ratio, its longer peduncle of cymes, and pedicellate flowers. The species is restricted to one location in the Midwest region of Rio Grande do Sul, occurring in rocky shrublands in the municipality of Jari. We present here a morphological description, illustration and photographs of the new species. Also. we propose the inclusion of B. bordignonii in the IUCN Red List of Threatened Species in the critically endangered (CR) category since its habitat has been drastically reduced by human activity.

A new species was collected during a fern expedition in the Nuluhon Trusmadi Forest Reserve, Sabah, Borneo. Morphologically, it is similar to both Pteris decrescens Christ and P. parviloba Christ but can be distinguished by frond characters. Specifically, the new species differs from the other two species by having basiscopic secondary pinnae (vs. without basiscopic secondary pinnae), petiolulate pinnae (vs. sessile pinnae), without bristles on the stipes (vs. with bristles on the stipes), a crenate margin of the pinna-segment apex (vs. a serrate apex), and entire pseudoindusia (vs. ciliate pseudoindusia). Furthermore, P. decrescens and P. parviloba differ in the number of lateral pinnae (5 or 6 vs. 8–16 pairs) and the length of the basal pinna-segments being shortest or longest of all lateral pinnae. Two plastid genes, rbcL and matK, were used to decipher their phylogenetic relationships. The new species was resolved in different clades from P. decrescens and P. parviloba, providing further support of its uniqueness. The morphology, illustrations, ecology, and distribution of the new species are provided. We also found that the type materials of P. decrescens included two different species, P. decrescens and P. parviloba.A lectotype of P. decrescens was therefore designated. Based on the results of this study, P. decrescens and P. parviloba are re-circumscribed, and the new species is described as P. borneensis sp. nov.