Date of Award:

12-2023

Document Type:

Thesis

Degree Name:

Master of Science (MS)

Department:

Biology

Committee Chair(s)

Robert Schaeffer

Committee

Robert Schaeffer

Committee

Terry Griswold

Committee

Joseph Wilson

Committee

Edward Hammill

Abstract

The Mojave Desert is one of the most biodiverse places in North America. A harsh environment with many species results in complex relationships between animals and plants. This study focuses on one bee-plant relationship, the Mojave poppy bee, and the Las Vegas Bear Poppy.

The Mojave poppy bee is rare and has only been collected from Las Vegas Bear Poppy, Dwarf Bear Poppy, and a few species of prickly poppies. A 1995 report suggested the bee was a major contributor of pollination for the Las Vegas Bear Poppy in Clark County, Nevada. More recently (2019), their local extinction in southwestern Utah was posited.

Las Vegas Bear Poppy is a rare plant in the poppy family only found in the eastern Mojave Desert where it shows a preference for sandy soil containing gypsum. It produces large amounts of pollen but does not produce nectar. A comprehensive survey of the poppy in 1993 documented numerous healthy populations. Subsequent surveys suggest populations are in decline.

Our main objectives were to find current populations of the host plant, Las Vegas Bear Poppy, in Clark County, NV, mainly in Lake Mead National Recreational Area (LMNRA) and Gold Butte National Monument (GBNM); determine the current bee visitor community associated with Las Vegas Bear Poppy populations; document presence of the Mojave poppy bee and determine whether the bee exclusively forages on the Las Vegas Bear Poppy.

The survey found small numbers of Mojave poppy bee at three sites in 2020 but none were found the following year in spite of systematic sampling across the entire flowering season that included the three sites with previous presence. Similarly intense surveys in 2022, yielded just single individuals at two of the three sites from 2020. Surveys for Las Vegas Bear Poppy populations found them no longer present at many historic locations with catastrophic declines in LMNRA in 2021 and up to 100% of some population by 2022. The bees visiting Las Vegas Bear Poppy also differed greatly on a year-to-year basis across 2020-2022, especially when compared to historic records. Analysis of pollen samples from Mojave poppy bees suggests a strong dependence on Las Vegas Bear Poppy with the vast majority of the pollen from it. Possible reasons for a small amount of pollen from other plants are discussed.

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