Pollen morphology, exine structure, and systematics of Acalyphoideae (Euphorbiaceae), part 3: Tribes Epiprineae ( Epiprinus, Symphyllia, Adenochlaena, Cleidiocarpon, Koilodepas, Cladogynos, Cephalocrotonopsis, Cephalocroton, Cephalomappa), Adelieae ( Adelia, Crotonogynopsis, Enriquebeltrania, Lasiocroton, Leucocroton), Alchorneae ( Orfilea, Alchornea, Coelebogyne, Aparisthmium, Bocquillonia, Conceveiba, Gavarretia), Acalypheae pro parte ( Ricinus, Adriana, Mercurialis, Leidesia, Dysopsis, Wetria, Cleidion, Sampantaea, Macaranga)

Abstract

This is the third paper of an extensive study of pollen morphology and exine structure of Acalyphoideae (Euphorbiaceae) following the most recent system of Webster. Pollen from 120 collections representing 96 species and 30 genera is described and illustrated with light microscopy, scanning and transmission electron microscopy. These taxa are from tribes Epiprineae, Adelieae, Alchorneae, and Acalypheae pro parte. Pollen of eight genera, Epiprinus, Symphyllia, Adenochlaena, Cleidiocarpon, Koilodepas, Cladogynos, Cephalocrotonopsis and Cephalocroton, of the nine assigned to Epiprinae share 3-colporate apertures, microreticulate, punctate or deeply punctate tecta, well developed or prominent columellae ( Koilodepas excepted) and thin foot layers; pollen of the ninth genus, Cephalomappa, has porelike colpi, a coarsely reticulate exine, irregular columellae and an irregular foot layer. Of the five genera assigned to Adelieae, pollen of Adelia, Lasiocroton and Leucocroton is similar: 3-colp(oroid)ate with stratified opercula, crotonoid tecta and thin foot layers; grains of Enriquebeltrania and Crotonogynopsis lack opercula and the latter has a distinctive infratectum of poorly differentiated columellae. All genera examined of tribe Alchorneae, seven of the nine, have exines with unstratified opercula and elongated columellae near the endoaperture. Exines of subtribe Alchorneinae ( Orfilea, Alchornea, Coelebogyne, Aparisthmium, Bocquillonia) have complex infratecta of poorly differentiated columellae, whereas pollen of Conceveiba and Gavarretia, the two genera examined of the three assigned to subtribe Conceveibinae, has a single layer of short columellae and almost identical tectal morphology. In the large tribe Acalypheae, pollen of the first six of the 11 subtribes was examined. Pollen of Ricinus (Ricininae) and Adriana (Adrianinae) share indistinguishable exine structures and tecta. Pollen of Mercurialis and Leidesia of subtribe Mercurialinae and pollen of Dysopsis of subtribe Dysopsidinae are almost identical: finely reticulate tecta, very thin apertural endexines, elongate columellae, and channeled/perforate foot layers. All three genera of subtribe Cleidiinae have grains that are 3-colporate and have complete tecta; pollen of Wetria has a tectum morphology very similar to that of Ricinus and Adriana; pollen of Cleidion is 3-brevicolporate with microrugulose or punctate tecta, and has threadlike non-apertural endexines and foot layers, and thick tecta; exines of Sampantaea have an endexine throughout the grain, thin foot layers, very short columellae and a thick continuous tectum. Pollen of Macaranga of subtribe Macaranginae is small, 3-colporate with poorly defined endoapertures, and an exine structure characterized by thin foot layers, short columellae, and thick tecta. Pollen data support: the concept of the subtribe Epiprininae, but indicate that subtribe Cephalomappinae ( Cephalomappa) is not related and should be considered for separate tribal status; a close relationship among Adelia, Lasiocroton and Leucocroton, but not with the two remaining members of Adelieae, Enriquebeltrania and Crotonogynopsis, which do not appear to be closely related to each other; the present concept of Alchorneae and subtribes Alchorneinae and Conceveibinae. Within the genera examined of the first six subtribes of Acalypheae, the pollen data: support a close relationship between the monogeneric subtribes Ricininae and Adrianinae; indicate a close relationship between subtribes Mercurialinae ( Mercurialis, Leidesia) and Dysopsidinae ( Dysopsis); suggest that Wetria is not closely related to Cleidion or Sampantaea (Cleidiinae); tentatively support the concept of Macaranginae as comprising only Macaranga.