SIX WEEKS

I am Cynthia McAlister, a biology graduate student at Sul Ross State University (SRSU). Last summer I was offered the marvelous opportunity to work on a project that beautifully meshes my long-time interest in botany with a new fascination—the insect world. For two years I will work with the Chihuahuan Desert Research Institute (CDRI) and SRSU studying the structure and diversity of insect pollinator communities of the CDRI Botanical Gardens on a project called What’s the Buzz? My graduate thesis will be based on the data I collect. I am delighted to have been asked to participate in this venture and excited about the many questions to be addressed by it.

For the past six weeks I have been working in the Botanical Gardens. I have observed the plants in flower and the insects visiting them, and tried out various data gathering and measuring techniques. This article briefly outlines what I have observed and begins a consideration about the goals of the project and how I intend to achieve them.

This year the rains started about the same time my work began. I found such abundant blooms and myriad insect visitors that at first the project seemed overwhelming. So many plants were blooming: guayule, prairie zinnia, a dozen species of Salvia, hummingbird-bush, yellow bells, and Senna. Texas kidneywood was a riot of blooms, and wildflowers were scattered all around. I walked around with my field notebook just trying to make sense of the variety of flowers in the botanical gardens. Insects zipped everywhere; at first I could make out only bees and butterflies. I collected everything I could catch.

Soon I began to recognize microgardens within the gardens. In my notes I have labeled them: the ceniza garden, the Salvia garden, the Pavilion garden. Some plants, such as all the individual Texas kidneywoods (Eysenhardtia texana), constitute gardens unto themselves. The Baccharis and the Adolphia are also microgardens. Scientists think of the group of insects attracted by a plant as its pollinator community. For my thesis I plan to define and compare the structure and diversity of the microgarden communities.

On a sunny, hot and humid September morning, kidneywood, like an alien mega-port, thrums with a constant traffic of insects arriving, fueling, and departing. Among the visitors are: elongate twig-like blister beetles; buoyant terra-cotta colored Queen butterflies; and Tarantula hawks—alarmingly large wasps with shiny blue-black bodies and fiery orange wings. Bee-mimic hover flies whiz around the flowers, then stop suddenly, with wings beating too fast to see, they hover momentarily choosing a flower from which to feed. Small bees with showy black and white striped abdomens move amongst the blooms buzzing between flowers, landing to feed quietly. Some have green eyes, others have yellow faces. They dig shallow nests in the ground and so are called digger bees. There are also many European honeybees. For the past six weeks the kidneywoods have been cloaked in spiky inflorescences of fragrant white flowers. The trees seethe with activity; from several feet away I can hear the hum of bees. Closer in, the air vibrates as hundreds of insect wings propel the beasts on their search for sustenance. The community of pollinators attracted by kidneywood is not only large but also diverse. I have observed over twenty different kinds of insects visiting it.

A very different example is the pollinator community of ceniza, or barometer bush (Leucophyllum frutescens), in the ceniza garden. For much of the late summer the ceniza were covered with a blanket of pinky purple flowers and droned with insect activity. However, unlike kidneywood, nearly all visitors were honeybees.

In the Salvia garden the structure of the pollinator community is somewhere between the diversity of kidneywood and the uniformity of ceniza. A dozen species of Salvia, crowded together in a lovely triangular raised bed, form an aromatic profusion of color. Here I found several different bees, including two kinds of bumblebees, two kinds of digger bees, and large shiny-black carpenter bees. Only rarely did a honeybee make a brief visit.

Based on my early observations, I predict that each plant supports a unique pollinator community. I am also interested in the pollinator community of the gardens as a whole. I expect, as the vegetation in the gardens reflects that of the northern Chihuahuan Desert, I will find the gardens’ pollinator community mirrors the pollinator community of the desert.

Gathering data suitable for scientific publication calls for forethought. How will the term "pollinator" be defined for this project; should ants be considered? What about thrips? How efficient is a particular insect at pollinating; do nectar robbers also pollinate? A Biostatistical Analysis course at SRSU is helping me think about how to quantify my observations. It is one thing to say that a shrub "seethes" with activity and quite another to make reasonable estimates of numbers of insects busy around a shrub during a given time. However, quantification of data allows the statistical comparisons I need to conclude my thesis.

Why are certain insects attracted to certain plants? How dependent is a plant upon a given pollinator? By studying pollinators of the gardens, I hope to understand more clearly the relationships between insects and the plants they visit. I will be working with Dr. Cathryn Hoyt and SRSU Biology professor, Dr. Chris Ritzi, to carve out manageable study questions suitable for my thesis. In the meantime, I continue to observe and collect in the Gardens, pin insects in the lab, research the literature on pollination ecology in the library and appreciate this opportunity to study one of Nature’s intriguing symbioses.