Pollen morphology of Deinostema, Geochorda, Gratiola, Ildefonsia, Sophronanthe, and Tragiola (Scrophulariaceae, Gratioleae, Gratiolinae)

Abstract

The pollen grains of Deinostema, Geochorda, Gratiola, Ildefonsia, Sophronanthe, and Tragiola are single, isopolar to anisopolar, and radially symmetrical, with three or four equally spaced meridional colpi. Pollen grains of Ildefonsia and Geochorda are semitectate with a relatively well-developed to intermediate sexine 1 (interstitium). In Ildefonsia the sexine 2 (tectum) is comprised of a complex network of vertically overlapping, interwoven muri, and a baculate sexine 3 is present. In Geochorda the muri are not vertically interwoven and the sexine 3 is absent. The grains of Deinostema, Gratiola, Sophronanthe, and Tragiola are tectate–perforate, lack a baculate sexine 3, and have a reduced to intermediate sexine 1. All of the taxa examined except Geochorda are distinguished from the Mimulinae by pollen morphology. The pollen evidence in Deinostema, Gratiola, Sophronanthe, and Tragiola correlates with the floral data and is consistent with a mutual relationship among these genera. The pollen grains of Geochorda and Ildefonsia are distinct from one another and from those of the other genera examined. Pollen of the latter is of a morphotype not previously reported in tribe Gratioleae.