Aristolochia mishuyacensis (Aristolochiaceae), a new record for Ecuador, with taxonomic notes

ABSTRACT Aristolochia mishuyacensis is recorded for the first time in the Ecuadorian Amazon. Two specimens were collected in two banks of black water tributaries of the Yasuní river, Yasuní National Park. This species is currently distributed in Bolivia, Brazil, Colombia, Ecuador, and Peru, below 200 m. An updated description and images of the species are provided, and its relationships with other species are discussed.


Introduction
Aristolochia L., the largest genus of the family Aristolochiaceae, comprises~500 species [1,2]. The genus presents a pantropical distribution that extends to the subtropics, Mediterranean zones, and some temperate areas [3][4][5][6]. Aristolochia can be recognized by its alternate, distichous leaves, usually with cordate-lobate base and palmate venation; zygomorphic apetalous flowers with a showy petaloid calyx formed by three fused sepals and differentiated into a basal utricle, a median tube, and an expanded distal limb; a gynostemium formed by the fusion of anthers and stigmas; and an inferior ovary that develops into a septicidal cylindrical capsule [3,4,7]. Pollination in Aristolochia is carried out by flies and beetles [8]. The genus has floral adaptations for brood site mimicry, especially scents and sometimes the appearance of carrion, dung, and fungi [9], a pollination syndrome known as sapromyiophily [10].
During the first comprehensive botanical expedition of the Yasuní river, an undercollected area in the Yasuní National Park, we collected Aristolochia mishuyacensis O.C. Schmidt, which is the first record of the species to the Ecuadorian flora (Figures 1 and  2). Here, we update and illustrate the description of the species, as fruits and seeds were not described before [3,17]. Additionally, we provide a map of distribution and comments on its relationships with other species.

Distribution and habitat
Primary or secondary, flooding Amazonian forests at elevations below 200 m of southern Colombia, eastern Ecuador, northern Peru, Brazil, and Bolivia ( Figure 2). In Ecuador, A. mishuyacensis was collected on vegetation growing along the banks of black water tributaries that flow into the Yasuní river. According to [19], an area dominated by "bosque siempreverde de tierras bajas del Napo-Curaray (BsTa02)". According to the field notes of the specimens Pérez et al. 9637 and 10862, it grows associated with tree species including the palms Astrocaryum jauari Mart. and Bactris riparia Mart., the legume Macrolobium acaciifolium (Benth.) Benth., and the Rubiaceae Bothriospora corymbosa (Benth.) Hook. f. and Rosenbergiodendron longiflorum (Ruiz & Pav.) Fagerl.

Phenology
The species has been collected in flower from March to May, July, October, and November, and sets fruits in March and from July to October.

Vernacular name
Aristolochia mishuyacensis is locally known as "zapatito de difunto" in Peru and "saragosa" in Ecuador.
williamsii O.C. Schmidt [17], but the same author provided a new name two years later [21], given that the former name was already in use for another species. It is related to the remaining species that conform the informal group Pseudostipulosae proposed by Hoehne [22], which comprises approximately 60 species of Aristolochia, all of them restricted to the neotropics. The diagnostic trait for these species is the atypical development of the prophyll (first or basal-most leaf) of each vegetative shoot. These prophylls are sessile or nearly so, considerably smaller than the normal leaves, and remain in contact to the shoot axis, giving thus the appearance of (false) stipules. Aristolochia mishuyacensis is easily distinguished from the remaining pseudostipulate-bearing species by the ovate to slightly hastate leaf blade, the bilabiate limb with its upper lip ovate, cucullate and prolonged into a long tapering cauda to 85 × 0.1-0.3 cm (Figure 1). The latter character is found also in four pseudostipulatebearing species: Aristolochia paulistana Hoehne, Aristolochia pohliana Duch. and Aristolochia weddellii Duch. from Brazil, as well as Aristolochia trilobata L., which is widely distributed in the neotropics. However, A. mishuyacensis differs from A. paulistana in the leaf consistency and shape (membranaceous and deeply cordate vs. chartaceous to coriaceous and truncate or nearly so, respectively). It differs from A. pohliana in the leaf and perianth shape (leaves ovate to narrowly ovate and lower lip of the perianth broadly ovate, 1-2 × 1.0-1.5 cm vs. leaves broadly ovate and lower lip of the perianth 3.5-4.5 × 2 cm, respectively). A. mishuyacensis differs from A. weddellii primarily in the seeds, which are winged in the former and not winged in the latter. Finally, it differs from A. trilobata by its entire leaves vs. the deeply lobed leaves in the latter species.
The morphology of capsules and seeds of Aristolochia mishuyacensis facilitates anemochory. The capsules are formed upside-down in the distal portions of the climbing shoots, which usually reach the forest canopy. The capsules dehisce acropetally and acquire a basket-shaped due to the incomplete separation of the six carpels, which remain apically fused at the level of the rostrum. The position and opening of the capsules expose the numerous flat, winged seeds to the wind, promoting long-distance dispersal.