Habitat destruction is a leading cause of species extinctions, and thus a serious conservation concern. The amount of remaining suitable habitat within a landscape, as well as the isolation of these habitat patches from one another, can have profound effects on biodiversity across a landscape. This research strives to predict how habitat destruction will alter landscape biodiversity through its effects on patch area and isolation, as well as the consequent influence on the resilience of biodiversity following habitat disturbance. Simulation modeling provides two opposing predictions for the effect of habitat destruction on landscape biodiversity. Depending on how habitat destruction alters species' immigration and extinction rates, habitat destruction can have either more severe or less severe effects on biodiversity than expected from a random-extinction model based upon the pre-destruction habitat area. Freshwater ecosystems are subject to both habitat destruction (e.g. draining of wetlands) and disturbances (e.g. contaminants), which can interact to alter patterns of their biodiversity, and are the focus of the empirical part of this study. Preliminary results from surveys of pond amphibian and invertebrate biodiversity indicate that habitat destruction will have more severe effects on biodiversity loss than expected by a random extinction model. To identify a biological mechanism behind this pattern, an experiment using artificial ponds will examine how habitat destruction can alter species immigration and extinction rates and influence the severity of landscape biodiversity loss. A second experiment will investigate how habitat destruction can affect the recovery of aquatic biodiversity following a habitat disturbance.
This project provides many opportunities to incorporate outreach to the general public, as well as to provide young scientists with genuine research experiences. Thus far, 6 undergraduate and 6 high school student interns have had hands-on field research experiences as part of this project. In addition to gaining experience in the field, students learn how to disseminate what they have learned to others. Undergraduate students have opportunities to a write senior honors thesis, while high school students act as science outreach ambassadors to their communities through formal and informal settings.
Habitat destruction is a leading cause of species extinctions, and a serious conservation concern. Habitat destruction is not only a loss of total habitat area, but also a creation of a fragmented landscape composed of isolated habitat patches. These remaining habitat patches form a metacommunity, which is a group of local communities, or patches, that are isolated from each other in space but connected through the dispersal of organisms, such as plants and animals, between patches. The size of the metacommunity after habitat destruction (i.e. the number and size of remaining patches), and the isolation of patches within it can have profound effects on biodiversity. The purpose of this research is to examine how metacommunity size affects biodiversity, and to provide insight into how the size of the metacommunity might influence the effects of future habitat destruction or disturbance. Freshwater systems are subject to both habitat destruction (e.g. draining of wetlands), and disturbances (e.g. contaminants), and are the focus of this study because of the negative effects both threats have on freshwater biodiversity. We first developed a mathematical model to obtain predictions for how changes in metacommunity size might affect species diversity. In a natural system, metacommunity size might increase species immigration rates into habitat patches through increasing the probability that dispersing organisms are intercepted by suitable habitat. When metacommunity immigration rates increase, diversity in a single habitat patch increases and fewer new species are encountered when additional patches are sampled. Conversely, metacommunity size may decrease species extinction rates in patches due to an influx of new individuals. When metacommunity extinction rates decrease there is little effect on the diversity in a single habitat patch, however new species are more likely to be encountered when new patches are sampled. If habitat patches are lost from a metacommunity due to habitat destruction, the overall affect on species diversity will depend on whether species immigration or extinction rates are more affected by metacommunity size. In order to determine if metacommunity size affects species diversity in natural systems, pond metacommunities were sampled in Missouri. Zooplankton diversity was sampled at five ponds in twelve different metacommunities during 2009 and 2010. We found that zooplankton species diversity in a pond increases when a pond is located within a larger metacommunity. However, new species are more likely to be encountered when sampling additional ponds within a small metacommunity, when compared to sampling ponds within a large metacommunity. These results provide the first example of metacommunity size affecting species diversity in a natural system and highlight the importance of considering metacommunity size when trying to understand landscape patterns of biodiversity. In addition to affecting species diversity in established metacommunities, metacommunity size can also influence the recovery and maintenance of species diversity following a habitat disturbance. The recovery and maintenance of diversity is dependent upon species interactions and a supply of individuals into the affected habitat. We used experimental aquatic plant communities to investigate the effect of an extreme heat and drought event on species diversity and the importance of dispersal for the recovery of diversity following this disturbance. Immediately after a heat and drought event during the summer of 2011, there was a significant loss in aquatic plant species diversity. This loss in plant diversity was maintained the following summer. Experimental ponds were then placed in either a control or in one of three dispersal treatments to simulate an effect of metacommunity size. Regardless of dispersal treatment, there was an increase in aquatic plant species diversity following dispersal. Future sampling of this project will determine if this recovery in aquatic plant diversity is maintained over additional seasons. The research supported by this National Science Foundation grant has benefits that extended beyond its scientific contribution of providing insights into the influence of metacommunity size on biodiversity. This research provided opportunities for undergraduate and high school students from the Saint Louis, MO area to gain hands-on research experience. In addition to gaining experience in the field, undergraduate and high school students involved in this grant learned how to disseminate what they had learned to others through complementary programs sponsored by Washington University in Saint Louis and the National Science Foundation.