Cololejeunea minuscula Pócs

Takashima, Tássia Toyoi Gomes, Pócs, Tamás & Ilkiu-Borges, Anna Luiza, 2024, Two remarkable liverworts from human-modified landscape in Eastern Amazonia: Cololejeunea minuscula Pócs and C. satioi sp. nov., Phytotaxa 671 (2), pp. 183-190 : 184-185

1. Cololejeunea minuscula Pócs ( Pócs & Bernecker 2009: 7)

Description and illustration:— Schuster (1980, Fig. 774, p. 1312 as Aphanolejeunea minuta R.M.Schust. ).

Material examined:— BRAZIL. Pará: Irituia, on bark in agroforestry systems, 01°41’04.6” S, 47°26’01.7” W, 9–15 m, 12 January 2021, T. T. G. Takashima & A. S. Assunção 1236, 1255, 1258, 1267, 1272, 1274 (MG). Ibid., on bark in forest with selective cutting used by Quilombolas community São José do Açaiteua, 01°40’08.0”S, 47°21‘49.9”W, 26 m, 12 January 2021, T. T. G. Takashima & S. Takashima 1344 (MG).

Discussion:— Cololejeunea minuscula has a scattered distribution in tropical America, with records from USA (Florida), Colombia, Ecuador, Peru, and southern Brazil ( Uribe & Gradstein 1998, Pócs & Bernecker 2009, Ristow et al. 2015, Gradstein 2020). Fischer (2013) registered this species from Rwanda, new to Africa. The first record of this species in Brazil was made by Ristow et al. (2015), in Paraná state, in the southern part of the country. This record, however, was overlooked and not included in important lists such as Flora and Funga of Brazil ( BFG 2021).

The collections from Irituia, northeastern Pará ( Fig. 1 ), extend the distribution of C. minuscula to the Brazilian Amazon and constitute the lowest elevational record for the species (9–26 m, measured on-site using the Garmin eTrex 10 GPS). Previously, the species had been recorded from sites at (380–) 950–1500 m, including locations in the highlands of Florida and the Andean region of Colombia. Possibly, specimens of C. minuscula have been overlooked in inventories due to the similarity in appearance with terrestrial filamentous algae ( Schuster 1980). Indeed, the species of subg. Aphanolejeunea , to which C. minuscula belongs, are among the smallest hepatics and are usually only visible in the field with a good hand lens ( Gradstein et al. 2001).

Curiously, almost all new records of C. minuscula (six specimens) were collected in agroforestry systems characterized by a mix of introduced regional fruit tree species and hardwood species, especially cocoa ( Theobroma cacao Linnaeus 1753: 782 ), Cupuaçu [ Theobroma grandiflorum ( Sprengel 1826: 332) K. Schumann 1886: 76 ], coffee ( Coffea sp. Linnaeus 1753: 172), macawood ( Platymiscium filipes Bentham 1860: 83 ), and blood ucuuba [ Virola surinamensis ( Rottbøll 1776: 13) Warburg 1897: 208 ]. Only one specimen was found in a selectively logged forest, in the same area where the new species, here described, was discovered.

Cololejeunea minuscula is a typically epiphyllous species and rarely occurs on bark ( Gradstein 2021). In this study, however, all specimens of C. minuscula were collected from bark in the understory of agroforest systems up to 1 m above ground.

Morphologically, C. minuscula is very delicate plant, 150–170 µm wide, with Aphanolejeunea - type branches and very thin stems, ca. 50 µm in diameter, consisting of five epidermal cells, lacking a medullary cell, all cells thin-walled, uniform in size, and ventral merophyte 1 cell wide. The leaf lobes are linear-lingulate to linear-lanceolate, 150–170 µm long, 85–88 µ wide, formed by 2–3 cells, margins crenulate, cells isodiametrical to slightly elongate, 13–17 × 12–16 µm. Lobules are usually not developed, but when developed, are inflated, ovate, more than 1/2 of the lobe length, 125– 133 µm long, 85–88 µm wide, keel curved, free margin incurved, tooth lobule erect, 1–2 cells. Asexual reproduction is abundant by discoid gemmae, which produce long, linear, 2-seriate thalli on gemma margins ( Schuster 1980).

Cololejeunea minuscula resembles C. gracilis ( Jovet-Ast 1947: 21) Pócs in Dauphin et al. (2008: 233) and C. papillosa (K.I. Goebel 1928: 41) Mizutani (1966: 156) , but the latter two species do not produce linear thalli on gemmae margins Cololejeunea gracilis , in addition, differs from C. minuscula in having toothed leaf margins and leaf cells being conically elevated on the dorsal surface ( Gradstein 2020).

Figures

FIGURE 1. Distribution of Cololejeunea minuscula Pócs (dots = register of occurrence).