Integrating the Effects of Biotic Interactions into Models of Species Distributions

The study of species geographic distributions and their environmental drivers has developed at a fast pace in recent years, owing to improvements in technology and data availability, and is increasingly relevant in this era of advancing global change. Currently, the field focuses heavily on a variety of techniques to statistically estimate species’ ranges I refer to collectively as species distribution models (SDMs). These models are now used across a wide range of disciplines, but inadequacies remain in implementation, methodology, and theory that are in need of new insight. In this thesis I will address two key shortcomings that require improvement in the field: limitations in modeling software and the lack of accounting for biotic interactions in SDMs. Current software for SDMs lags behind code-based implementation with respect to flexibility, reproducibility, and other features of open science. Biotic interactions (i.e., those between species) have traditionally been considered relevant to species’ geographic distributions only at fine spatial scales, but recent studies demonstrating their importance at the macroscale has sparked a paradigm shift. I present four chapters in this thesis: one chapter that introduces new software and three analytical chapters that explore different ways to integrate the effects of biotic interactions into SDMs. The first chapter highlights a new modular SDM software called \textit{Wallace} that enables reproducible modeling analyses in an interactive environment layered with guidance text and disseminates new tools to broader audiences. The second improves range estimates for two closely related and parapatric spiny pocket mice in South America that likely compete, one of which is labeled Threatened by the IUCN Red List. To do this, I remove areas of range overlap in SDM predictions using support vector machines. I demonstrate that the resulting range estimates are more accurate and ecologically realistic than approaches that ignore biotic interactions, and that changes to areal estimates for similar species could result in a rethinking of threat status. The third evaluates whether the addition of biotic predictor variables to abiotic SDMs increases model performance for range estimates of migrating monarch butterflies in Mexico. I create these variables from species richness estimates for mutualistic and commensal plants that provide food and shelter during the migration, and account for flowering phenology in a novel way. I found that models which combined abiotic and biotic variables had the highest performance, and those that also accounted for flowering phenology performed best of all. The fourth investigates how co-occurrence patterns change over environmental gradients for an little-studied assemblage of sympatric carnivorans in Japan that are purported competitors: invasive raccoon, native raccoon dog (tanuki), and invasive masked palm civet. I use multispecies SDMs that account for imperfect detection to determine whether there is evidence of competitive exclusion by the raccoon of the other carnivorans from suitable sites. My results show that in deep forest areas raccoon presence was strongly conditional on the presence or absence of other carnivorans, while tanuki presence was unaffected, which is contrary to our expectations based on current thought regarding these species\u27 interactions. Collectively, this thesis develops new tools and methods for SDMs, as well as specific implications for conservation and management for the three systems studied, that bolster the evidence that biotic interactions matter at the macroscale and help move the field of species geographic distributions and their environmental drivers forward. Additionally, this thesis features novel research products that hold great utility for conservation and management, including improved range estimates for a rodent of conservation concern, the first SDM for monarchs during their migration through Mexico, and the first estimates of co-occurrence patterns for invasive raccoons in Japan with tanuki and masked palm civet