Evol Ecol Res 2: 627-643 (2000)     Full PDF if your library subscribes.

A phylogenetic reconsideration of the pollen starch–pollination correlation

T’ai H. Roulston¹ and Stephen L. Buchmann²

¹Department of Entomology, Auburn University, Auburn, AL 36849 and ²USDA-ARS Hayden Honey Bee Research Laboratory, 2000 E. Allen Road, Tucson, AZ 85719, USA

Address all correspondence to T’ai H. Roulston, Department of Entomology, Box 7613, North Carolina State University, Raleigh, NC 27695-7613, USA.

ABSTRACT

Mature pollen possesses or lacks starch grains. Many wind-pollinated and self-pollinated species possess starch grains. This apparent association has led some researchers to hypothesize that starchiness of pollen is functionally related to pollen consumption by pollinators. This hypothesis assumes that starchy pollens contain less oil than starchless pollens, and predicts that pollen-consuming insects will be deterred by starchy pollens because of an inability to digest starch or attraction to more oily pollens due to a greater caloric reward. We assembled a database of 207 plant species for which starchiness of pollen and pollination mode are known. We organized these species into a phylogeny based on published cladograms and tested three hypotheses concerning the concordance of pollen starch and pollination mode. We found that starchiness of pollen arose at least 19 times among the 207 species. Using the concentrated changes test, we found that starchiness of pollen did not arise unusually often in wind-pollinated lineages. We found that shifts to starchy pollen did not result in an unusual number of shifts away from bee, fly or beetle pollination. Furthermore, shifts to starchy pollen did not result in an unusual number of shifts away from pollen consumption. There is little evidence to show a general trend of starch avoidance by pollen-consuming insects. Of the three plant species containing the greatest concentration of pollen starch, among the 89 species for which starch has been quantified, corn (Zea mays) and English plantain (Plantago lanceolata) are readily collected by bees, and cattail (Typha latifolia) is commonly used in the artificial rearing of bees. Recent evidence suggests that pollen starch may relate to resistance to desiccation.

Keywords: phylogeny, pollen, pollination, pollination syndrome, starch.

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