Gretchen LeBuhn

A meta-analysis of bees' responses to anthropogenic disturbance

Pollinators may be declining globally, a matter of concern because animal pollination is required by most of the worlds plant species, including many crop plants. Human land use and the loss of native habitats is thought to be an important driver of decline for wild, native pollinators, yet the findings of published studies on this topic have never been quantitatively synthesized. Here we use meta-analysis to synthesize the literature on how bees, the most important group of pollinators, are affected by human disturbances such as habitat loss, grazing, logging, and agriculture. We obtained 130 effect sizes from 54 published studies recording bee abundance and/or species richness as a function of human disturbance. Both bee abundance and species richness were significantly, negatively affected by disturbance. However, the magnitude of the effects was not large. Furthermore, the only disturbance type showing a significant negative effect, habitat loss and fragmentation, was statistically significant only in systems where very little natural habitat remains. Therefore, it would be premature to draw conclusions about habitat loss having caused global pollinator decline without first assessing the extent to which the existing studies represent the status of global ecosystems. Future pollinator declines seem likely given forecasts of increasing land-use change.

Spatial patterns of bee captures in North American bowl trapping surveys

Abstract.  1. Bowl and pan traps are now commonly used to capture bees (Hymenoptera: Apiformes) for research and surveys.

The influence of urban park characteristics on ant (Hymenoptera, Formicidae) communities

As rapid urbanization continues, existing natural areas within urban zones will play a critical role in safeguarding remaining biodiversity. Ants are an integral part of almost every terrestrial ecosystem, including urban environments, and understanding which environmental characteristics influence their persistence is critical. In this study, 24 protected natural areas within urban parks including mosaic, scrub, herbaceous and forest habitats were surveyed for ants with 563 pitfall traps. The data provide insights into the distribution and abundance of ant fauna in San Francisco natural areas, as well as which characteristics of parks have the most influence on ant community composition. A total of 2,068 ant individuals representing 15 species were collected. A regression analysis revealed that urban forests reduced ant richness and abundance and that there was little or no impact of the Argentine ant on native ants. Natural area size and shape were not important in explaining variations in overall ant species richness and abundance, with many smaller natural areas harboring ant populations that are just as diverse and robust as larger areas.

Mining photo-sharing websites to study ecological phenomena

The popularity of social media websites like Flickr and Twitter has created enormous collections of user-generated content online. Latent in these content collections are observations of the world: each photo is a visual snapshot of what the world looked like at a particular point in time and space, for example, while each tweet is a textual expression of the state of a person and his or her environment. Aggregating these observations across millions of social sharing users could lead to new techniques for large-scale monitoring of the state of the world and how it is changing over time. In this paper we step towards that goal, showing that by analyzing the tags and image features of geo-tagged, time-stamped photos we can measure and quantify the occurrence of ecological phenomena including ground snow cover, snow fall and vegetation density. We compare several techniques for dealing with the large degree of noise in the dataset, and show how machine learning can be used to reduce errors caused by misleading tags and ambiguous visual content. We evaluate the accuracy of these techniques by comparing to ground truth data collected both by surface stations and by Earth-observing satellites. Besides the immediate application to ecology, our study gives insight into how to accurately crowd-source other types of information from large, noisy social sharing datasets.

Insects and plants: engaging undergraduates in authentic research through citizen science

Many citizen-science programs – including the Monarch Larva Monitoring Project and the Great Sunflower Project – are managed by university researchers, and this connection has facilitated the involvement of undergraduate students in project design, data collection and management, and independent research. Here, we describe the benefits of undergraduate involvement, and encourage citizen-science coordinators and college faculty to increase the use of citizen science and citizen-science data in undergraduate training.

A sensitivity analysis of pollen-dispensing schedules

Without changing their allocation to male function, plants can increase male fitness by increasing the number of visits they receive, attracting more efficient pollinators, or by changing their schedule of dispensing of pollen to floral visitors. We explore the strength of selection on the different components of pollen-dispensing schedules using sensitivity analysis. We find that changes in both the efficiency of pollinators and the expected mean number of visits produce large changes in male fitness. Our results suggest there may be strong selection on features that allow pollen to be available to multiple visitors and that selection is probably weak for mechanisms that would promote near optimal dispensing schedules.

Warbling Vireo reproductive success and nest-site characteristics in the northern Sierra Nevada, California

Abstract Over the past 20 yr Warbling Vireo (Vireo gilvus) populations have declined in California. We monitored Warbling Vireo nests in the high elevations of the northern Sierra Nevada in the Tahoe National Forest near Truckee, California. Nest survivorship was low (29.9% Mayfield estimate) compared to Warbling Vireo populations outside of California, but similar to levels reported for other California populations. Brown-headed Cowbird (Molothrus ater) parasitism in the study population was low (7%). Warbling Vireo nest fate was related to nest-site location; successful nests in lodgepole pine (Pinus contorta) were situated on the west or “warmer” side of the tree, in the outer periphery of the foliage, and in areas with slightly less canopy cover compared to unsuccessful nests. These features of the nest site may help reduce the threat of predation and combat cold stress. Our results argue that Warbling Vireos in the northern Sierra Nevada have low nest survivorship (similar to populations in other areas of the state), and that successful nests are often found on thin branches well removed from the main stem.

Patterns of Bat Distribution and Foraging Activity in a Highly Urbanized Temperate Environment

Understanding how to manage biodiversity in urban areas will become increasingly important as density of humans residing in urban centers increases and urban areas expand. While considerable research has documented the shifts in biodiversity along urbanization gradients, much less work has focused on how characteristics of dense urban centers, effectively novel environments, influence behavior and biodiversity. Urban bats in San Francisco provide an opportunity to document changes in behavior and biodiversity to very high-density development. We studied (1) the distribution and abundance of bat foraging activity in natural areas; and (2) characteristics of natural areas that influence the observed patterns of distribution and foraging activity. We conducted acoustic surveys of twenty-two parks during 2008–2009. We confirmed the presence of four species of bats (Tadarida brasiliensis, Myotis yumanensis, Lasiurus blossevillii, and M. lucifugus). T. brasiliensis were found in all parks, while M. yumanensis occurred in 36% of parks. Results indicate that proximity to water, park size, and amount of forest edge best explained overall foraging activity. Proximity to water best explained species richness. M. yumanensis activity was best explained by reduced proportion of native vegetation as well as proximity to water. Activity was year round but diminished in December. We show that although bats are present even in very densely populated urban centers, there is a large reduction in species richness compared to that of outlying areas, and that most habitat factors explaining their community composition and activity patterns are similar to those documented in less urbanized environments.

Collectively Improving Our Teaching: Attempting Biology Department–wide Professional Development in Scientific Teaching

A collaborative professional development program that engaged nearly 90% of faculty in a biology department in more than 40 hours of training on scientific teaching was instituted. Participating instructors integrated active learning in their courses, as shown through a variety of methods, and reported positive effects on teaching and departmental community.

A Science Products Inventory for Citizen-Science Planning and Evaluation

Abstract Citizen science involves a range of practices involving public participation in scientific knowledge production, but outcomes evaluation is complicated by the diversity of the goals and forms of citizen science. Publications and citations are not adequate metrics to describe citizen-science productivity. We address this gap by contributing a science products inventory (SPI) tool, iteratively developed through an expert panel and case studies, intended to support general-purpose planning and evaluation of citizen-science projects with respect to science productivity. The SPI includes a collection of items for tracking the production of science outputs and data practices, which are described and illustrated with examples. Several opportunities for further development of the initial inventory are highlighted, as well as potential for using the inventory as a tool to guide project management, funding, and research on citizen science.