Lejeunea (sect. Echinocolea) Gradst.

[Clade V]Lejeunea sect. Echinocolea(R. M. Schust.) Gradst. (Gradstein 2018: 7) Echinocolea R. M. Schust. (Schuster 1963: 125) Type species Lejeunea asperrima Spruce. Description Plants very delicate, less than 1 mm wide. Stems with only 3–7 rows of medullary cells. Leaf lobes with a very narrow base (abruptly dilated beyond the keel), dorsal leaf surface and margins with projecting, often spinose mammillae with thickened outer walls. Cuticle smooth. Oil bodies finely granular, few (1–4) per cell, often brownish. Gynoecia with one sterile or fertile innovation, bracts and bracteole broadly connate. Perianths inflated, 5 - keeled, keels crenate to ciliate-laciniate. Asexual reproduction by caducous leaves, cladia, and strap-shaped gemmae. Distribution Neotropical. Species Lejeunea asperrima, L. subspathulata Spruce. Further species (not sequenced) Lejeunea asprella Spruce, L. meridensis Ilk. - Borg. Notes Lejeunea sect. Echinocolea is a robust lineage, being sister to sect. Crossotolejeunea and sharing ciliate-laciniate perianths and finely granular oil bodies with the latter section. The section differs from sect. Crossotolejeunea in the much smaller plants with leaf lobes narrowed at the base and ornamented on the dorsal surface and margins, a smooth cuticle, and an abundance of modes of vegetative reproduction. Unexpectedly, L. reinerae from eastern Malesia, the only paleotropical species of Lejeunea with a roughened dorsal leaf surface and having been placed in Echinocolea in the past, was not resolved in sect. Echinocolea despite its close similarity to L. asperrima (Ilkiu-Borges 2005). Instead, the species was found in subg. Crossotolejeunea in a moderately supported sister relationship to L. patersonii from Malesia. The latter species approaches L. reinerae in having strongly crenulate leaf margins, but the dorsal leaf surface of L. patersonii is smooth, the leaf base is not highly narrow, and the outer walls of the projecting leaf margin cells are not thickened. The position of L. reinerae in the sect. Crossotolejeunea clade indicates that the peculiar leaf shape and ornamented leaf surface of sect. Echinocolea are homoplasious characters. Reference Ilkiu-Borges (2005).