Pollen morphology of tribes Alsineae and Sperguleae (Caryophyllaceae) and its systematic significance

Pollen morphology of 79 species, one subspecies and eight varieties representing nine genera of tribe Alsineae and two of tribe Sperguleae was studied using light microscopy (LM) and scanning electron microscopy (SEM). Among them, 53 species and eight varieties (22 species of which are endemic to China) were reported for the first time. The results demonstrate that the number of pores, the pollen surface ornamentation and the density of microechini have important systematic significance. The surface ornamentation can be divided into three types, namely microechinate-perforate, microechinate-punctate, and microechinate-punctate-perforate. Pollen characteristics support: (i) isolation of <i>Arenaria</i> subgenus <i>Odontostemma</i> from <i>Arenaria</i> and reclassification of <i>Arenaria</i> subgenus <i>Odontostemma</i> to <i>Odontostemma</i>; (ii) isolation of <i>Cerastium</i> subgenus <i>Dichodon</i> from <i>Cerastium</i> and reclassification of <i>Cerastium</i> subgenus <i>Dichodon</i> to <i>Dichodon</i>; (iii) isolation of <i>Minuartia</i> subgenus <i>Rhodalsine</i> from <i>Minuartia</i> and reclassification of <i>Minuartia</i> subgenus <i>Rhodalsine</i> to <i>Rhodalsine</i>; (iv) isolation of <i>Rhodalsine</i> from tribe Alsineae and reclassification of <i>Rhodalsine</i> into tribe Sperguleae; and (v) isolation of <i>Sagina</i> from tribe Alsineae. In addition, the relationships of <i>Arenaria</i> subgenus <i>Eremogone</i> and <i>Arenaria</i> subgenus <i>Eremogoneastrum</i> to tribe Alsineae need to be further studied. Furthermore, pollen characteristics indicate that tribe Alsineae is more evolved than tribe Sperguleae.