Using stylized agent-based models for population–environment research: a case study from the Galápagos Islands

Agent Based Models (ABMs) are powerful tools for population-environment research but are subject to trade-offs between model complexity and abstraction. This study strikes a compromise between abstract and highly specified ABMs by designing a spatially explicit, stylized ABM and using it to explore policy scenarios in a setting that is facing substantial conservation and development challenges. Specifically, we present an ABM that reflects key Land Use / Land Cover (LULC) dynamics and livelihood decisions on Isabela Island in the Galápagos Archipelago of Ecuador. We implement the model using the NetLogo software platform, a free program that requires relatively little programming experience. The landscape is composed of a satellite-derived distribution of a problematic invasive species (common guava) and a stylized representation of the Galápagos National Park, the community of Puerto Villamil, the agricultural zone, and the marine area. The agent module is based on publicly available data and household interviews, and represents the primary livelihoods of the population in the Galápagos Islands – tourism, fisheries, and agriculture. We use the model to enact hypothetical agricultural subsidy scenarios aimed at controlling invasive guava and assess the resulting population and land cover dynamics. Findings suggest that spatially explicit, stylized ABMs have considerable utility, particularly during preliminary stages of research, as platforms for (1) sharpening conceptualizations of population-environment systems, (2) testing alternative scenarios, and (3) uncovering critical data gaps

Mapping habitat quality in conservation's neglected geography

This thesis describes conceptual and methodological work that aims to advance the science of modeling and mapping wildlife habitat in human-modified landscapes. First, I review how researchers have defined and measured the quality of wildlife habitat over the past four decades. I then demonstrate a new approach to quantifying habitat quality by modeling habitat for the federally endangered Red-cockaded Woodpecker (Picoides borealis, RCW) across the Onslow Bight, a one million hectare region of North Carolina's coastal plain. Next, I describe the development and operation of a GIS toolbox for ArcGIS 9.3, called "Connect", designed to help conservation practitioners incorporate habitat connectivity considerations into land management and land-use planning. In two stakeholder-driven case studies, I use the Connect tools to prioritize private land parcels for connectivity conservation in fragmented habitats around Fort Bragg, NC, and evaluate the effectiveness of a proposed corridor in promoting dispersal for RCW in the face of urban development

A landscape approach to forecasting climate change impacts on geographic ranges and phenologies of plants in the Washington Cascades

Thesis (Ph.D.)--University of Washington, 2017-12As the pace of environmental change accelerates, biologists are transforming the discipline of ecology from a fundamentally descriptive science to one that can be used to generate skillful forecasts. Although important progress is being made, this work is stymied by (1) our limited understanding of the physical and biological processes involved, (2) our limited knowledge of how those processes vary across space, and (3) our ignorance of the feedbacks between ecological change and human society. In this work, we aim to contribute new process understanding, conceptual frameworks, and quantitative tools that help to alleviate these three limitations and advance our ability to forecast the impacts of climate change on plants in the Cascade Range (Washington, USA), where rapidly changing climate and hydrology pose unique risks to features of ecosystems that are economically and culturally important. Chapter one concerns the fundamental ecological processes that maintain the geographic range limits of plants, focusing on the role of climate and disturbance in setting contemporary range limits and mediating the response of those ranges to a warmer climate. As a study system, we used two species of yellow monkeyflower (Erythranthe spp.) that have similar habitat requirements, but strikingly different elevation ranges in Mt. Rainier National Park. We combined data from a large-scale transplant experiment and a multi-year observational study using a spatial population model. We found that the ranges of these two closely related and ecological similar species responded very differently to changes in climate, and we forecast that ranges will shift downhill for one species under some scenarios. This work illustrates the importance of accounting for landscape-scale processes in generating skillful forecasts of species range shifts. Chapter two focuses on forecasting how climate change will affect the landscape patterns of reproductive synchrony (landscape flowering phenology) in plants across networks of habitat patches. In this work, we use previously estimated relationships between climate and flowering time, as well as spatially extensive datasets on species distributions and microclimates, to predict spatial patterns of landscape phenology across Mt. Rainier throughout the growing seasons of 2009 - 2015. We found that unusually early snow melt in low elevation meadows in 2015 caused many species to bloom out of sync across their elevation ranges, decreasing the potential for pollen dispersal between meadows. Because 2015 conditions were similar to those expected by the late 21st century under unabated climate change (early low-elevation snow melt, warm spring temperatures), this raises the possibility that climate change could be an agent of population fragmentation in this system. Finally, chapter three considers how warming climates affect the relationships between ecosystems and their social and management context. Specifically, we use thousands of geolocated photos uploaded to the social media platform Flickr to track interactions between recreational visitors and the plant phenology of subalpine and alpine ecosystems in the Washington Cascades, where spectacular wildflower displays draw millions of visitors each year, and generate tens of millions of dollars of economic activity. We found that the timing of recreational visits to subalpine ecosystems at Mt. Rainier National Park was substantially less sensitive to variation in climate than the timing of wildflower displays. This led to pronounced mismatches between visitor and wildflower activity in the climate-change analog conditions experienced in 2015 at our sites. Overall, this work illustrates how a landscape approach can help to overcome the challenges associated with forecasting ecological responses to environmental change

Mitochondrial DNA alignment

Mitochondrial DNA alignment (ND1 gene) in phylip format

Data from: Evidence for concerted movement of nuclear and mitochondrial clines in a lizard hybrid zone

Moving hybrid zones provide compelling examples of evolution in action, yet long-term studies that test the assumptions of hybrid zone stability are rare. Using replicated transect samples collected over a 10 year interval from 2002 to 2012, we find evidence for concerted movement of genetic clines in a plateau fence lizard hybrid zone (Sceloporus tristichus) in Arizona. Cline-fitting analyses of SNP and mtDNA data both provide evidence that the hybrid zone shifted northward by approximately two kilometres during the 10 year interval. For each sampling period, the mtDNA cline centre is displaced from the SNP cline centre and maintaining an introgression distance of approximately 3 km. The northward expansion of juniper trees into the Little Colorado River Basin in the early 1900s provides a plausible mechanism for hybrid zone formation and movement, and a broad-scale quantification of recent land cover change provides support for increased woody species encroachment at the southern end of the hybrid zone. However, population processes can also contribute to hybrid zone movement, and the current stability of the ecotone habitats in the centre of the hybrid zone suggests that movement could decelerate in the future

Unlinked SNP, phylip

Unlinked SNPs in phylip format

Unlinked SNPs, alleles

Unlinked SNPs, alleles, for Structure and Adegenet analyses

Data and scripts for the field experiment evaluating freezing potential and recruitment under early snowmelt

Data and scripts for the field experiment evaluating freezing potential and recruitment under early snowmeltScript for the field experiment analysesSnowmelt and freezing degree data from the five gardens.germination and survival data from the field experiment</p

Code and data suppporting "Theobald, Breckheimer, and HilleRisLambers. 2017. Climate drives phenological reassembly of a mountain wildflower meadow community. In Press. Ecology

Identical to v1.0, but a new release is required for Zenodo archiving and DOI assignment