Summer Science Research at Bryn Mawr

'Williams, Dr. Neal' Archive

The Wildlife of “ Lake Vickers ”: A Biodiversity Survey of the Campus Pond

Posted May 26, 2010

In winter of 2000-2001, the College built a water catchment pond behind Rhoads Hall to retain runoff water from local-area drainage systems as well as from the College grounds. This pond has three inlets, one from the Shipley School and nearby area, one from a storm drain on Wyndon Avenue and one inlet from a convergence of pipes beneath the College grounds that flows into the pond below the surface of the pond. Water exits the pond through a single pipe on the end of the pond opposite the inflow. In addition to providing a water control mechanism, the pond was intended to provide a habitat for native plants and animals. Native plants were introduced as part of the construction plan, but no proposal was made for restoration of other native species. Such a “field of dreams” strategy of restoring structural vegetation with the tacit assumption that other species will arrive on their own is a common approach in restoration ecology. Although other researchers at the College have made regular studies of chemistry and water flow, no surveys of biodiversity have been performed since initial construction. I will survey the plants, algae, invertebrates, mammals, herpetofauna and birds that inhabit the pond and the surrounding area and create a database that can be used by future researchers. Particular areas of focus will be the main inlet pipe, a wash coming from the city no. 2 inlet storm drain on Wyndon Avenue , and two paths through the waterline vegetation created and highly traveled by resident Canada geese. Since these are the most obvious sources of incoming water and runoff containing substances like vegetation and earth, they have a great deal of influence over the pond content.

Pollination of Crops by Native Bees

Posted May 26, 2010

Pollination is an essential part of food production. Humans depend on the fruits of flowering plants to fulfill much of their nutritional needs. Because over 66% of pollination relies on insects, primarily bees 1 , their presence is necessary for setting fruit on crops. Most farmers rely on managed honey bee colonies to pollinate their crops. However, recent declines in honey bee populations due to disease, pesticides and other factors have increased the economic burden to maintain these colonies on farms 2 . Although honey bees contribute a large part to crop production, native bees also help in this effort. In addition, some native bees are better pollinators of crops than honey bees. Therefore, an understanding of how native bee populations are contributing to crop pollination will provide an assessment of their role on agricultural lands.

Crop Pollination by Bees as a Function of Farm Surroundings

Posted May 26, 2010

Pollination is essential for crop production; the quality and amount of pollination directly affects the quality and amount of resulting crops, and thus the profit a farmer can make from a given harvest. Crop pollination is provided primarily by managed colonies of honey bees and a diverse set of native bees. The contributions of the latter remain largely unrecognized and for the most part have not been quantified. These native bees can be viewed as providing a potentially valuable benefit to humanity, a so called ecosystem service. The diversity and of bees on farms has been shown to be affected by surrounding landscape. More complicated and developed land results in a lower diversity and abundance of bees (Klein et al. 2000; Steffan-Dewenter et al. 2001). There is evidence that this ultimately results in lower quality pollination (Kremen et al. 2002).

Ecological compensation mechanisms within pollinator communities in the face of species loss

Posted May 13, 2010

Ecosystem services are processes and contributions from the natural world that are essential to human well-being. Among the most important of these services is pollination, which is provided primarily by bees and is required for the successful production of half of the world’s crops. Recent declines in managed honeybees and concerns about food security in an increasingly populous world make it imperative that we understand the role of other wild bee species and the factors that influence pollination to ensure stable pollination. A series of recent articles suggest that pollination, like other ecosystem services, is dependent upon diversity and abundance of species within a system, thus loss of biodiversity may severely impact crop pollination and production. This may occur because the total level of pollination service provided depends on the number of individual bees visiting a crop and on the amount of pollination each individual provides.

Identifying resource distributions within a floral community

Posted May 10, 2010

In most flowering plant communities, individual species are visited by a diversity of pollinators, primarily bees. Surprisingly little is known about the factors that determine to which plant species the pollinators visit. Although we tend to view bees as pollinators, they visit flowers to collect food– pollen and nectar– that they provide their offspring. Many factors ultimately influence the number of offspring a bee produces, but in a simple sense more resources of higher quality translate into a larger brood. As a result we expect bees to visit plants with higher quality of resources. Scaling up to the whole community, if we determine the resource qualities among plants species, we can gain insight into a key mechanism underlying the visitation patterns of pollinators.

The Effect of Development Intensity on Bombus Species Richness

Posted May 10, 2010

In recent decades the Philadelphia area has experienced rapid and extensive developmental growth, and development continues to expand into surrounding green areas. In the last ten years alone, what used to be the outer suburbs, interspersed with wooded areas and ringed by agriculture, has seen the quick construction of large housing developments, retail outlets, and the widening of roads to increase traffic capacity. This rapid land conversion could have many ecological consequences, including a negative effect on bumblebee (Bombus spp.) populations. It is the goal of this study to evaluate species composition in different landscape matrices in order to determine the effect development intensity in the surrounding landscape may have on species richness and the presence of particular bumble bee species. The study will take place from the beginning of June to the middle of August 2006 in Philadelphia, Montgomery, Chester, Delaware and Bucks counties in Pennsylvania.

The pollinator effectiveness of specialists versus generalists on Sphaeralcea laxa

Posted May 7, 2010

Within pollinator communities subsets of pollinators exist. Specialists include pollinators that limit their visitation to only one plant species, and generalists include those that visit a variety of plant species. Because they visit primarily a single plant species, specialist pollinators would, at first, appear to be a highly effective pollinator. However, specialist pollinators have been shown to visit plant species that are also visited by abundant and diverse generalist pollinators (Hurd 1975). As a result, the contribution of generalists may overwhelm the role of specialists (Thompson and Pellmyr 1992). In order to quantify the value of specialist and generalists to the reproductive success of the host plant species, we compared the effectiveness and rates of visitation by generalists and specialist bees visiting Sphaeralcea laxa, a plant native to the Chihuahuan Desert. Fieldwork centers and sites are located in the upper Chihuahuan Desert near the intersection of the Mexican states of Sonora and Chihuahua, and the U.S. states of Arizona and New Mexico.

The Importance of Natural Habitat to the Pollination of Watermelon and Cherry Tomato

Posted May 7, 2010

More than 66% of the crops worldwide are insect pollinated with bees often being the most important pollinator. Although honey bees have been considered the cornerstone of agricultural pollination in the USA, an increasing number of studies suggest that native bees also provide pollination services. Because these species are not managed, their contribution to crop pollination may vary with the area and the proximity of natural habitat to farm sites. Studies in California suggest that the amount and stability of pollination from native bees increased with the area of upland habitat 1. Surveys of bees from central Europe show that the overall species richness and abundance of native bee species decrease as more land is lost to commercial or residential development.2 As the colonies of managed European honeybees (Apis mellifera) steadily decline3 in the US, the importance of native bees as crop pollinators increases. Because natural habitat provides nesting resources for native bees, potentially the dependency of crops on bee pollinators might provide viable incentives for the conservation of natural areas to procure the needed pollination services from native bees.

Effectiveness of Native Bees as Pollinators

Posted May 7, 2010

Pollination is an ecological service essential to the fertilization of many agricultural crops. These crops require a pollinator in order to reproduce, and for many crops, this pollinator is a bee. Bees are particularly adept at pollination, and in the case of many crops, the presence of bees is essential to their success. Among these crops are watermelon (Citrullus lanatus) and cherry tomatoes (Lycopersicon esculentum), which feature as the target crops in our study. In order to ensure a higher yield, many farmers manage honeybees (Apis mellifera), investing time and money into their care, with the expectation that these colonies will effectively pollinate the farm’s crops. Unfortunately, the honeybee populations, both domesticated and feral, have declined by 50-70% since 1946 (USDA 1980; data from 1980-2001, E. Mussen, personal communication). In light of this drastic drop in honeybee colonies, focus has been shifted to the ability of native pollinators to fertilize crops.