Deguelia tenuiflora (Leguminosae, Papilionoideae), a remarkable new species from the Brazilian Amazon Rodrigo

A new species of Deguelia from north of Manaus (Amazonas state), Brazil, is described and illustrated here as Deguelia tenuiflora . It is vegetatively similar to D. amazonica , while its flowers resemble D. negrensis and D. scandens. This new species exhibits the following unique characteristics: mostly unifoliolate leaves covered abaxially by a peculiar indumentum, and calyx with vexillary lobes triangular-depressed, which allows for its recognition as a distinct species. We provide a table of characters for distinguishing the new species from congeners and a distribution map of the new taxon. :

Deguelia was reestablished by Geesink (1984), who recognized it as distinct from Derris and Lonchocarpus. Previously, most of the Deguelia species had been described in these other genera.
The genus Deguelia includes plants that are highly variable in habit, presence and type of floral dots, indumentum covering the corolla, number of ovules, and type of fruit. The genus can only be characterized by its inflorescence type: a pseudoraceme in which the secondary axes form brachyblasts (shoots with little internode elongation) containing more than five flowers (Camargo & Mansano, unpublished). Phylogenetic studies suggest a drastic reduction in the number of species in the genus, while the inflorescence type, also typical in many Phaseoleae genera, seems to Rodriguésia 73: e00172021. 2022 have appeared in Millettieae at least three different times (Camargo & Mansano, unpublished).
A recently updated analysis shows that Deguelia should be restricted to species that show a defined suite of characters, instead of just the inflorescence type (Camargo & Mansano, unpublished). That important characters defining the genus include the presence of darkened dots smaller than 0.1 mm on the calyx and corolla (although absent in one species), lack of indumentum on the corolla, a membranaceous corolla, a standard lacking basal callosities, keel petals subequal to the wings, fewer than six ovules (usually up to four), indehiscent fruits with an evident wing along the adaxial suture (lacking in one species, which bears elastically dehiscent fruits). These restrictions result in reducing the number of Deguelia species to four (Camargo & Mansano, unpublished).
A new species of Deguelia, conforming to the new circumscription, was collected by one of the authors at PDBFF (Biological Dynamics of Forest Fragments Project) north of Manaus, in an Area of Relevant Ecological Interest (ARIE) between Manaus and Rio Preto da Eva in the state of Amazonas. Here we provide a full description of the new species, its known ecological preferences, IUCN status, a distribution map, taxonomic comments, and a table of morphological characters that distinguish this species from others of the genus.

Materials and Method
The discovery of the new species occurred during an ecological study of intact and fragmented forests within the PDBFF, executed by the second author. Sterile and fertile specimens were collected and sent for identification to the first and third authors (Leguminosae specialists), who recently had completed a revision of Deguelia (Camargo & Mansano, unpublished). Once determined to be a new species, it was described using terminology based on Radford et al. (1974) and Font Quer (1985). The microscopic measurements were taken with the aid of a stereoscopic microscope and a Starfer 150 × 0.02 mm caliper. The specimens collected during the fieldwork are deposited in UEC and INPA herbaria. Preliminary values for conservation status were based on IUCN Standards and Petitions Committee (2022), and the scenarios were evaluated using the GEOCAT tool (Bachman et al. 2011 Fig. 1 The species differs from all others in the genus mainly by the presence of almost exclusively unifoliolate leaves, present on the reproductive branches and rarely up to five leaflets on sterile branches, presence of stipels and leaflets abaxially covered by a long, dense ferrugineous tomentum (unique in the genus).
The species was only found in May with flowers, in spite of being collected in almost every month of the year in sterile form. The etymology refers to its fragile flower parts, in particular the petals and staminal tube. Deguelia tenuiflora bears the following unique features: regularly unifoliolate leaves, although some sterile individuals may have 1, 3, or 5 leaflets, abaxially dense-tomentose, and a calyx with vexillary lobes triangular-depressed (Tab. 1). Vegetative morphological traits place this species closest to D. amazonica Killip, which bears very distinct flowers, with longer, purple to pink petals (versus pale cream in the new species), and a consistently higher number of leaflets (the new species normally bears just one leaflet on leaves of fertile branches and regularly bears just one leaflet on sterile branches) with a different indumentum type (short-adpressed versus longtomentose abaxially). The flowers resemble D. negrensis (Benth.) Taub. and D. scandens Aubl. but the new species can be distinguished mainly by its vexillary calyx lobe shape, and vegetative characters, in particular the presence of a dense indumentum on the abaxial surface of leaflets. The new species bears stipels, rarely seen elsewhere in the genus (only in D. amazonica in few specimens with very young leaflets, as they fall off frequently). Field censuses found consistent presence of dark red latex in stems 2 cm and larger in diameter.
Deguelia tenuiflora was frequently observed sterile and unifoliolate, being collected only one time with flowers. Few individuals were seen with up to 5 leaflets, such as R.J. Burnham