TODD, BRENT L.1*, HENRY R. OWEN1, and JANICE M. COONS1,2. 1Department of Biological Sciences, Eastern Illinois University, Charleston 61920; 2Department of Natural Resources and Environmental Sciences, University of Illinois at Urbana-Champaign, Urbana 61801. - Pollen comparison from insect visitors to Stylisma pickeringii (Convolvulaceae), an endangered plant of Illinois sand prairies.
Stylisma pickeringii flowers are white, funnel-shaped, and have
an average corolla diameter of 1.9 cm. During summer 2001, eighteen
genera of insects visiting flowers of S. pickeringii were
collected. The collections of Heterostylum croceum, H
robustum, and Neorhyncocephalus volaticus were records in
the state of Illinois. The purpose of this study was to determine if
the six most frequent insect visitors (from most to least frequent:
Apis mellifera, Heterostylum croceum, Agapostemon
splendens, Dialictus sp., Perdita sp., and
Toxomerus marginatus) to S. pickeringii flowers were
carriers of its pollen. Pollen collected from S. pickeringii
flowers preserved in FAA was compared to pollen collected from bodies
of the insect visitors. Pollen was observed using light microscopy at
100 and 400X. S. pickeringii pollen is white or yellow-tinted
and spheroidal with an average diameter of 53.7 ± 6.5 mm. Pollen
collected from the insects also had the same color and shape. The
average diameters of pollen collected were 53.7 ± 8.6, 51.4 ± 2.0,
50.9 ± 3.3, 50.0 ± 2.8, 49.6 ± 3.9, and 49.5 ± 3.3 mm from H.
croceum, A. splendens, Perdita sp., A.
mellifera, Dialictus sp., and T. marginatus,
respectively. Although average pollen diameters varied, it appears
that pollen collected from bodies of all insects is that of S.
pickeringii. Thus, these six insects are carriers of S.
pickeringii pollen and are expected to pollinate its flowers.
Key words: Convolvulaceae, endangered plant, insects, pollen, sand prairie, Stylisma pickeringii