Identifying the factors affecting populations is essential for understanding contemporary issues that influence biodiversity, such as climate change, habitat destruction, and the spread of invasive species, and for providing solutions to mitigate these issues. In population biology, spatial modularity occurs when habitats are highly connected to other habitats from movement of individuals but only weakly connected to the remaining habitats in the landscape. This modular structure creates population aggregations at a scale that has been previously ignored in field ecology and yet it is predicted to have strong implications for the persistence and connectivity of populations. This Early Concept Grant for Exploratory Research (EAGER) assessed the causes and consequences of spatial modularity for populations by manipulating habitat (prickly pear cactus; Opuntia humifusa) for a pest insect, a cactus-feeding true bug (Family Coreidae; Chelinidea vittiger). By using field experiments, mark-recapture data, and modeling, two major objectives were addressed: 1) understand the consequences of spatial modularity for populations undergoing habitat loss, the greatest near-term threat to biodiversity; and 2) identify the causes of spatial modularity, which will provide key information for conservation and management. Over the course of the investigation, over 8000 C. vittiger in 15 landscapes that underwent habitat loss and fragmentation were marked and tracked to interpret reproduction and survival. In all landscapes, substantial spatial modularity occurred, where movements of individuals were highly clustered across habitat. These patterns were identified through the development of novel analytical methods relevant to animal populations. This consistent pattern highlighted the ubiquitous nature of modularity in populations. The causes of these patterns were largely driven by variation in vegetation between habitat patches (or the 'matrix'). This mechanism illustrates how environmental conditions surrounding habitats can have large impacts on movements of animals, influencing the connectedness of local populations. Ultimately, habitat loss and fragmentation had strong effects on populations, where loss and fragmentation reduced survival and reproduction, leading to lower population size. These results will provide much needed insight to limiting the negative effects of habitat destruction on populations and results may transcend ecology by being relevant to other fields that use network approaches to assess the stability of systems, such as the internet and transportation infrastructure. The methods and ideas generated from this project were used to inform conservation practitioners through an organized symposium and training workshop, as well as train a new generation of students in the STEM disciplines.  

Last Modified: 10/27/2016
Modified by: Robert J Fletcher