Re-discovery of Catasetum mojuense (Orchidaceae: Catasetinae), a poorly-known Amazonian species

The re-discovery of Catasetum mojuense A.T. Oliveira & J.B.F. Silva (Orchidaceae), an Amazonian species described in 1999 from the State of Pará, Brazil, is reported. In addition to geographic distribution data, a morphological description, taxonomical and ecological comments, conservation status assessment and photographs of C. mojuense are also provided. The species is characterised by having epiphytic habit, non-resupinate staminate flowers, brown-spotted petals, galeiform and smooth (no ribs) lip, lateral lobes with sparsely short-fimbriate margins and convergent antennae. Catasetum mojuense is morphologically similar to Catasetum discolor (Lindl.) Lindl, but is easily distinguished by the longer sepals and petals and the spotted petals on the staminate flowers. The new locality of occurence for C. mojuense is approximately 190 km east of the type locality, also in the State of Pará. The species is assessed as Critically Endangered. Habitat depletion and the limited number of sites of occurrence are the main concern for the conservation of C. mojuense.

The genus Catasetum Rich. ex Kunth (Epidendroideae, Cymbidieae, Catasetinae) comprises at least 130 species and dozens of natural hybrids and is distributed from México to Argentina, but has its greatest diversity in the Brazilian Amazon (Romero and Carnevali 2009;Flora do Brasil 2020), from where several new taxa have been described recently (e.g. Petini-Benelli 2016a; Petini-Benelli and Soares-Lopes 2017; Valsko et al. 2019). Catasetum is characterised by robust pseudobulbs, plicate leaves, basal and racemose inflorescence and commonly unisexual and dimorphic flowers. Species of the genus are mainly distinguished by characteristics of the staminate flowers (Romero and Carnevali 2009;Valsko et al. 2019).
Within the scope of the long-term project "Flora do Pará: Orchidaceae", a collected individual of Catasetum was found to represent the second herbarium record of C. mojuense A.T. Oliveira & J.B.F. Silva, a poorly-known Amazonian species. In addition to geographic distribution data, a morphological description, taxonomical and ecological comments, conservation status assessment and photographs of the species are also provided.
The individual was initially cultivated in the orchidarium of Universidade Federal Rural da Amazônia and flowered in August 2019, October 2019 and January 2020 ( Fig. 1), when finally it was pressed according to Petini-Benelli (2016b) and deposited at herbarium HCP (acronym according to Thiers 2020). The specimen (R.S. Miranda & F.A. Silva s.n., HCP 405) was identified through consultation of specialised literature on the genus, such as Oliveira and Silva (1998), and analysis of protologues of species closely related to C. mojuense. The collections of the Amazonian herbaria HBRA, HCJS, HCP, HF, HIFPA, HSTM, IAN, MFS and MG were also consulted. Digital databases CRIA (2020) and JABOT (2020) were also checked, but proved uninformative. Coordinates of the type locality were inferred using specimen label information (Magdalena et al. 2018). Area of Occupancy (AOO) was calculated using the online platform Geospatial Conservation Assessment Tool (GeoCAT) and was based on a defined cell width of 2 km (Bachman et al. 2011  only one flower positioned at the apex of the inflorescence. Catasetum mojuense was mistakenly described as having only one resupinate staminate flower Silva 1998 [1999]), possibly due to the bending and senescence of the collected inflorescence, but the species presents up to 15 non-resupinate staminate flowers (Fig. 1). The vegetative organs of the species (pseudobulbs and leaves) were also originally described and illustrated, although the protologue makes no mention of ex situ cultivation of parts of the holotype or the occurrence of other specimens. In any case, pseudobulbs, leaves and mainly the inflorescence of the newly-collected specimen presented larger dimensions than those described by Silva (1998 [1999]), but this may only represent discrete phenotypic variation.
The species is recognised when fertile and is characterised by non-resupinate staminate flowers, brown-spotted petals, galeiform and smooth (no ribs) lip, lateral lobes with sparsely short-fimbriate margins and convergent antennae. Catasetum mojuense is morphologically similar to Catasetum discolor (Lindl.) Lindl. (Oliveira & Silva, 1998[1999), but is easily distinguished by the longer sepals and petals (≥ 2.5 cm long vs. sepals and petals ≤ 2.1 cm long) (Pessoa et al. 2015;Flora do Brasil 2020) (Fig. 2). Based on these two records, the AOO was determined to be 8 km 2 . According to IUCN criteria (2020), C. mojuense is assessed as Critically Endangered (CR B2ab [i,ii,iii, v] + C2a[i]), since it has AOO < 10 km 2 and is restricted to only two fragmented locations, where there are certainly fewer than 250 adult specimens in total and probably fewer than 50 in each subpopulation.
The Municipalities of Moju and Capitão Poço, wherein C mojuense occurs, are predominantly covered by dense ombrophilous forest (Fig. 2) (IBGE 2019). Nevertheless, the vegetation in the two municipalities has been intensely suppressed. In Moju, pasture and secondary vegetation occupy extensive areas and selective extraction of wood and intensification of oil palm cultivation are notorious (Ferreira et al. 2017). Likewise, the vegetation of Capitão Poço has been replaced by pastures and agricultural activities, mainly for orange and pepper cultivation. Therefore, habitat depletion and the limited number of sites of occurrence are the main concerns for the conservation of C. mojuense. The new record of C. mojuense in Pará encourages continued floristic-taxonomic projects encompassing Orchidaceae in the state, especially those that include determining population sizes and establishing conservation policies for endemic or threatened species.
We thank Erik Wild for reviewing the English language and Igor Soares dos Santos for helpful suggestions.