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HUMMINGBIRD DISPERSAL OF DELPHINIUM CARDINALE POLLEN TREATED WITH RADIOACTIVE IODINE
Author(s) -
Schlising Robert A.,
Turpin Randolph A.
Publication year - 1971
Publication title -
american journal of botany
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.218
H-Index - 151
eISSN - 1537-2197
pISSN - 0002-9122
DOI - 10.1002/j.1537-2197.1971.tb09989.x
Subject(s) - pollen , biology , herbaceous plant , botany , delphinium , population , biological dispersal , pollen source , perennial plant , stamen , horticulture , pollinator , pollination , demography , sociology
A new technique has been employed to trace pollen dispersal in populations of Delphinium cardinale (Ranunculaceae), a herbaceous perennial native to southern California. Radioactive iodine (I 131 ) was applied directly to fresh pollen on stamens of living plants and subsequently traced and recorded on other plants in the field. While absolute amounts of I 131 or pollen dispersed were not determined, monitor detection showed that radioactive pollen was dispersed to open flowers (more often to the brightest flowers higher on the plants), and not randomly to stems or unopened flower buds. All dispersal was attributed to hummingbirds—the only observed flower visitors and pollen vectors for these plants. One very dense Delphinium population had almost 140 lambda of I 131 applied over 8 days to 76 flowers on six plants in the center of an area 22 m in diam. One fourth of this area monitored after 30 hr showed radioactive pollen on flowers of 8.9% of the 271 flowering stems; 8 days after the first application of I 131 another fourth of the area showed radioactivity on flowers of 58.2% of the 323 stems in it. A second study area 22 m in diam had 18 lambda of I 131 applied to 18 flowers on one plant in the center; 64.2% of all (137) flowering stems in the area had radioactive pollen detectable 24 hr later. It is clear that pollen from very few flowers and plants can quickly reach a large proportion of the individuals in such populations. The strongly protandrous nature of the flowers, the frequent flower visits of nectar‐gathering hummingbirds, and the regular adhering of pollen to birds' chins suggest that cross pollination (xenogamy) regularly occurs in these delphiniums. Further study of such pollen vectors' habits and flight patterns, while using pollen tagged with I 131 , should lead to quantitative expressions of pollen (and gene) dispersal within and among spatially separated plant populations such as these.