Palynological characterisation of the Androcallis, Microcallis, and Monticola sections of the genus Calliandra Benth. (Leguminosae - Mimosoid Clade) present in north-eastern Brazil

Abstract

In Brazil, the genus Calliandra Benth. (Caesalpinioideae; Leguminosae) comprises 74 species, of which 59 are endemic; the north-eastern region stands out as its largest dispersal centre. Calliandra species display a pollen dispersal unit (polyad) formed by eight calymmate, ellipsoid pollen grains, with a uniplanar arrangement and bilateral symmetry. Pollen units of native and ornamental Calliandra species present in north-eastern Brazil were analysed to provide subsidies for studies on the ecology and taxonomy of the genus. Pollen morphometric data of 25 species and two varieties were used to characterise the genus into different Calliandra sections. The pollen material analysed was acetolysed, then measured, described, and photomicrographed under light microscopy (LM). Quantitative data were submitted to descriptive statistical treatments. In the Calliandra sect. Androcallis and C. sect. Monticola, polyads tended to be larger in length and width than those in the C. sect. Microcallis. In the C. sect. Monticola, an appendage was present in the most acute region of the apical pollen grain. Quantitative data showed that the largest polyad occurred in C. macrocalyx var. macrocalyx, with dimensions of 250 µm × 150 µm, and the smallest polyad occurred in C. leptopoda, with 117.5 µm × 65 µm. Based on the data obtained for polyad length, it was possible to differentiate the species into distinct groups within and between sections studied.