Pollen Morphology in the Genus Mimulus (Scrophulariaceae) and Its Taxonomic Significance

Abstract

The pollen morphology of 117 species and varieties of Mimulus was examined by light and scanning electron microscopy. Five major and 8 more tentative, minor types were found based on the differential correlation of aperture type, exine morphology, pollen grain diameter and other characters: type 1—synaperturate, usually ±spiraperturate, exine perforate to microreticulate with supratectal processes; type II—trocolporate, exine microreticulate (IIa and IIb, supratectal processes absent; IIa, mean polar axis 16–19 μm; IIb, mean polar axis 25–35 μrn; IIc, supratectal processes present); type III—tricolpate, colpus membrane ±psilate. exine with supratectal processes (IIIa, exine microreticulate and 1.4–2.0 μm thick, polar axis ≥ 30 μm; 111b, exine densely perforate and 2.2–2.8 μm thick, polar axis ≤ 23 μm); type IV—tricolpate, colpus covered with spinulose granules (operculate), exine microreticulate with supratectal processes; type V—5–7 stephanocolpate (Va and Vb, colpus margins ±straight and nongranular; Va, exine microreticulate with supratectal spinules; Vb, exine perforate with supratectal spinules or spinulose verrucae; Vc, colpus margins ragged and granular, exine microreticulate with supratectal processes). The pollen data correlate well with geographical and macromorphological data and, where the latter are ambiguous, often provide important clues toward the resolution of conflicting interpretations of infrageneric classification and generic delimitation.

Aflp Phylogeny of Mimulus Section Erythranthe and the Evolution of Hummingbird Pollination

“…This character is particularly useful to distinguish M. cardinalis from M. verbenaceus in Arizona, where there has been confusion in identifying these two taxa (Kearney and Peebles 1960). Support for this group can also be found in analyses of pollen morphology (Argue 1980).…”

Pollen Morphology in the Genera Monttea and Melosperma (Scrophulariaceae)

“…That of Monttea, although unusual, has been observed in several genera of this tribe. The mean diameter of the tecta1 perforations and the Pr/T ratio in M. aphylla and M. schickendantzii are small, but they are not statistically different from those found in species of Berendtiella, Leucocarpus, Mazus, or many tricolporate Mimulus, and Monttea chilensis fails to differ in either character from any genus of the Mimuleae (Table 4; Argue, 1980Argue, , 1981Argue, , 1983Argue, , 1984 (Argue, 1984). The close relationship between microreticulate and rugulate-microreticulate exines with vertically overlapping tectal elements is perhaps most apparent in the occurrence of both types in single specimens of some taxa (e.g., Mazus japonicus, Levine 280, MO; Argue, 1984).…”

“…8-12 [Vol. 72 chaena, and are common in the subgenus Synplacus of Mimulus (Argue, 1980(Argue, , 1983(Argue, , 1984. As in Monttea and Melosperma, the colpus membranes in the Mimuleae may be more or less smooth or granular.…”

“…The exine morphology observed in Melosperma is common in the Mimuleae (Argue, 1980(Argue, , 1983(Argue, , 1984. That of Monttea, although unusual, has been observed in several genera of this tribe.…”

“…Collection data and figure references for specimens examined in the present study are summarized in Table I. Methods of pollen preparation, examination, and measurement have been described previously (Argue, 1980(Argue, , 1983(Argue, , 1984. Terminology generally follows Erdtman (1952), Praglowski and Punt (1973), and Walker and Doyle (1975).…”