Abstract
We investigated the pollen morphology of eight species of Acalypha occurring in Bahia State, Brazil. Flower buds were collected from specimens deposited in the CEPEC and HUEFS herbaria. Pollen samples were acetolyzed and analyzed using both light and scanning electron microscopy. The pollen grains examined using optical microscopy were found to be small and brevicolporate, with three to six apertures and elevations and fastigium, and had a psilate to scabrate exine. Scanning electron microscopy revealed the presence of supratectal elements and Ubisch bodies, and evidenced three pollen types based mainly on exine ornamentation: microrugulate-scabrate (slightly rugulate-scabrate), areolate-rugulate, and microechinate. This study provides new data and new interpretations of pollen morphology for the genus Acalypha, with comments on the palynological relationships between Acalypha and its sister group Mareya, and the next most closely related genus (Spathiostemon).
Highlights
The family Euphorbiaceae has cosmopolitan distribution, occurring mainly in tropical areas (Heywood et al 2007)
We investigated the pollen morphology of eight species of Acalypha occurring in Bahia State, Brazil
The present research focused on the pollen morphology of species occurring in Bahia State, Brazil, based on surveys of herbaria and consultations of the specialized literature (Pax & Hoffman 1924; Sousa et al 2019; Flora do Brasil 2020 2018), including Acalypha almadinensis, A. amblyodonta, A. brasiliensis, A. communis, A. klotzschii, A. multicaulis, A. poiretti, and A. villosa
Summary
The family Euphorbiaceae has cosmopolitan distribution, occurring mainly in tropical areas (Heywood et al 2007). In Brazil, Euphorbiaceae is represented by 950 species distributed within 64 genera that grow in varied habits and different vegetation types (Flora do Brasil 2020 2018). According to Cardiel et al (2015), the genus Acalypha is the third-largest genus of Euphorbiaceae, comprising approximately 500 species with pantropical distributions and with high degrees of endemism in the Americas; few of its species reach temperate regions. One of the most complete and accepted taxonomic treatments of Acalypha is that of Pax & Hoffman (1924), which considered 390 species. Species segregations mainly consider the inflorescence, indumentum, stipules, and leaf venation (Seberg 1984). According to Wurdack et al (2005), the sister group of Acalypha is the genus Mareya, with the most closely related genus being Spathiostemon
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