Date of Award:

8-2022

Document Type:

Thesis

Degree Name:

Master of Science (MS)

Department:

Biology

Committee Chair(s)

Karen Kapheim

Committee

Karen Kapheim

Committee

Theresa Pitts-Singer

Committee

Kezia Manlove

Abstract

Most bees are solitary and important contributors to pollination of a variety of crops. Solitary bees do not live in colonies. Instead, females work individually to construct nests and provision nutrients for each offspring. However, solitary bees can be difficult to manage, especially on a large scale like honey bees, because of differences in how species provision for their offspring and construct nests. Variations in the timing of offspring development to adulthood even within species makes commercial management difficult. Variations in reproductive strategy, like how many offspring to make, how much provision to give each, and when to make them can be influenced by external factors like changes in day length or temperature. Variations in reproductive strategy can also occur based on the maternal environment, or condition of the mother and what she experiences. Some bees halt their development when resources are scarce or weather is not favorable entering a state called diapause. In one species of solitary bees, the alfalfa leafcutting bee (ALCB), Megachile rotundata, some offspring forgo pausing their development and instead emerge as adults the same generation they were born. This results in a loss of pollinators for the following growing season.

ALCB are the most managed solitary species and one common management practice for ALCBs is to slow their development in the spring to better align crop bloom and bee emergence, though the effects of this practice are not well known. This is done by placing bees, after they complete diapause, into cool temperatures to slow their development. From preliminary data we found that cool stalling decreases maternal nutritional condition by reducing the amount of lipids. We hypothesized that the loss of bees in the same season they were laid is due to a maternal effect as a result from the practice of cool stalling, but what this maternal effect is and how it passes to offspring is unknown.

We set up an experiment to investigate the effects of maternal nutritional condition on offspring outcome and diapause. We found that external factors like photoperiod and time of season were always significant predictors of offspring development and outcome. We found that females that experienced longer times in cool stalling had less lipids, produced fewer offspring and made smaller provisions for their offspring. These females that experienced longer cool stalling also made fewer diapausing offspring, specifically fewer female diapausing offspring. We also found maternal nutritional condition reflected in offspring development and outcome through differences in mass provision sizes. Cool stalling decreases maternal nutritional condition and the poor condition leads to less offspring overall and specifically fewer female bees, pollinators, for the next season.

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