New pollen analyses of species belonging to the genus Dicranostyles Benth. - Convolvulaceae Pollen of Dicranostyles (Convolvulaceae)

Convolvulaceae is a widely distributed family with its highest species richness in tropical regions. Among its 12 tribes, Maripeae comprises three neotropical genera, including Dicranostyles Benth., with 16 species distributed throughout the Amazon Rainforest. This study characterizes the pollen morphology of Dicranostyles, providing palynological data for future studies on pollen evolution within Maripeae and comparative analyses across Convolvulaceae. Pollen grains were prepared using the acetolysis method, and surface ornamentation was examined through scanning electron microscopy (SEM). The genus showed considerable variation in pollen grain size and shape, as well as amb types ranging from subtriangular to subcircular. SEM analysis revealed the presence of a perforate tectum with microechinate ornamentation, one of the key diagnostic features of the genus. In all species, the sexine is thicker than the nexine, with conspicuous columellae. A consistent tricolpate aperture type (3-zonocolpate) was observed across all species, suggesting its potential as a diagnostic feature for the genus, especially when associated with other palynological traits (tectum, shape). These characteristics reinforce the close morphological relationships among the genera of Maripeae and support the affinity of the tribe within the Dicranostyloideae clade.

Keywords:
Lianas; Maripeae; Microechinate; Pollen; Tricolpate