The evolution of body size: Body size is one of the most important determinants of an organism’s ecological role (Hanken and Wake 1993). Because it is correlated with physiological and fitness characters, body size has been one of the most important traits evolutionary biologists have investigated. My research explores three major stories of dramatic changes in body size: 1) Miniaturization in sympatric lineages of Aphonopelma tarantulas; 2) Sexual size dimorphism in the golden orb-weaving spiders (Nephilidae); and 3) The evolution of large body sizes as an anti-bat trait in the evolutionary “arms race” between bats and moths. Future work will utilize phylogenetics, morphometrics, and comparative genomics (de novo genome sequencing and transcriptomics) to investigate the evolutionary path of these traits, as well as the putative mechanisms and the genome regions that have provided for these changes.
Understanding how Earth's diversity has been shaped by evolution is one of the key objectives in biological research, and a compelling mechanism for engaging and educating the public. Recent advances in our capacity to collect, integrate, and analyze vast amounts of biological data (e.g., high-throughput genome sequencing and digitization of natural history collections) have revolutionized our understanding of how evolution has produced such an astonishing array of form and function. Yet despite centuries of discovery, the majority of our planet's diversity – and the hidden stories of those lineages, remains unknown. Central to discovering these stories, is our ability to confidently infer relationships across the Tree of Life.
My research uses modern computational approaches, e.g., phylogenomics and bioinformatics, to establish a foundation from which to test hypotheses about the generation and maintenance of biodiversity. By integrating genomic, morphometric, ecological, and behavioral data, I work to explain patterns across differing landscapes and time, as well as how biotic and abiotic factors have influenced speciation and extinction. While I have an organismal focus on arachnids and Lepidoptera, my research is driven by questions, such as: 1) What are the relationships within the arthropod Tree of Life?; 2) Why are particular lineages on the Tree of Life more diverse than others?; and 3) How have predator-prey interactions influenced trait and lineage diversification?
Convergent evolution: Convergence is a striking example of the power of natural selection. But is convergence a common occurrence? Evidence is mounting that it is, yet the rules that determine the patterns of convergence we see are not well understood. It is important for us to ask why convergence occurs in some cases and not others. If we rerun the “tape of life”, will the results be the same? To do this, my research combines phylogenetics, functional genomics, geometric morphometrics, and behavioral experiments to investigate the mechanisms behind these patterns. For example, future work will look to understand whether convergence is correlated with niche and/or predatory variables (e.g., community composition, distributions, interactions), and/or genomic changes (i.e., gene expression and regulation patterns) - Can we predict where hindwing tails will evolve, or putatively have evolved, in the Saturniidae moths?
Bat-Moth evolutionary "arms race": With an estimated 140,000 described species, an enormous array of wing shapes and body sizes exist across Lepidoptera. However, few studies have investigated the drivers of this spectacular morphological diversity. A major hypothesis I am working to answer is whether differences in moth wing shape and body size are associated with their primary nocturnal predators – bats, and if these trait differences relate to clade diversity. With their suite of anti-predator strategies (i.e., ears keen to a bat's ultrasonic echolocation, acrobatic evasive flight, and specialized morphology to aid in defensive flight and escape mechanisms – e.g., hindwing tails and ultrasound-producing organs that "jam" bat biosonar), moths in the superfamily Bombycoidea are an ideal system to test evolutionary hypotheses concerning the historical path of anti-bat traits.
My current NSF postdoctoral research is gathering phylogenomic data and natural history collection data to quantify body size and wing shape variation across the Bombycoidea in order to infer evolutionary relationships and test hypotheses on the interplay between wing shape, body size, and anti-bat traits. Future genomic research will continue gathering the data needed to: 1) test whether there are correlated changes between anti-bat strategies and increasing/decreasing rates of speciation or extinction; and 2) decipher the functional genomics of wing shape and body size. Future behavioral work will continue growing our bat/moth behavioral interaction datasets needed to test for and quantify the selective advantage of putative anti-bat traits.
"Nothing in evolution makes sense except when seen in the light of phylogeny."
- Jay Savage, evolutionary biologist
Systematics: My dissertation research documented the taxonomy, diversity, and distribution of the tarantula genus Aphonopelma Pocock, 1901 within the United States. Aphonopelma is a group where traditional morphological characters were generally ineffective at evaluating inter- and intraspecific variation, with the genus declared “one of the greatest known challenges to species delimitation in spiders”. The principal goal of this research was to formally resolve the species-level diversity by using an integrative approach that combined phylogenomics with morphological, geographic, and behavioral data to define species boundaries.
Future research will expand this systematic work throughout the family Theraphosidae (tarantulas), resolving relationships and attempting to explain how this family became one of the most diverse of all spiders. One important aspect of this work will be my growing collaboration with researchers in Mexico – an incredibly diverse region with a large number of species that have been overlooked, under-sampled, and undescribed. A major focus of this collaborative endeavor will be to better understand the evolution of the blind, troglophilic tarantula species of Mexico – the only place where this is known to occur. This collaboration will provide graduate students in Mexico the opportunity to be involved in modern, integrative evolutionary research (e.g., investigating the genomic pathway/s and mechanism/s for eye-loss in spiders).
Additionally, I am currently expanding my taxonomic efforts and knowledge into the Lepidoptera superfamily Bombycoidea, a group of ~6,000 described species; in particular, the less well-known families where taxonomic effort has been low (e.g., Apatelotidae, Eupterotidae, Lasiocampidae, and Phiditiidae), yet critical for better understanding the bat/moth ‘arms race’.
Phylogenomics & Genomics: During collaborative work with Alan and Emily Lemmon (Florida State University), we developed an Anchored Hybrid Enrichment (AHE) targeted sequencing probe kit for resolving the spider Tree of Life at multiple evolutionary depths. By providing a mechanism where different researchers can confidently and effectively use the same loci for independent projects, synthesizing data across research groups, we are accelerating an understanding of spider evolution. Additionally, to create the foundation for my moth research, I modified my postdoc advisor’s (Kawahara) AHE Lepidoptera kit to work more efficiently across the superfamily Bombycoidea. Future phylogenomic work will continue to utilize this AHE methodology to establish and test biodiversity hypotheses, as well as produce an open-access bioinformatics pipeline for processing and preparing AHE data.
My current and future functional genomic research investigates the evolution of body size (both in spiders and moths), eye loss (troglophilic spiders), wing shape evolution (Saturniidae moths), and the evolution of two principal sensory systems (vision and olfaction) in the Lepidoptera subfamily Bombycoidea. Currently, we are quantifying the sensory morphology of the eye and antenna, and reconstructing the evolutionary history of genes in the visual and olfactory transduction networks to test whether sensory morphology, and selection on relevant genes, changes between species that are active during the day or night. Future work will heavily utilize high-performance computing (HPC) resources to continue answering the many fascinating evolutionary and genomic questions across arthropods.
Spider Tree of Life: Spiders are a prototypical highly diverse arthropod group comprising over 45,000 described species. Diversifying since the Devonian, this ancient group plays a dominant predatory role in almost every terrestrial ecosystem. In addition to their remarkable ecological importance, diversity, and abundance, spiders are known for their extraordinary biomolecules like venoms and silks, and have become models for behavioral and evolutionary studies. Despite considerable effort, progress in spider molecular systematics has lagged behind the advances made in other comparable arthropod groups. Unfortunately, this has hindered family-level resolution, classification, and tests of important macroevolutionary hypotheses (e.g., the origin of sticky silks, various web types and hunting strategies).
Future research in my lab will continue to build upon the enormous phylogenomic datasets (both transcriptome and AHE data) currently being gathered to answer longstanding questions regarding the relationships, diversification, and evolution of spiders. Student projects will further our understanding of the spider Tree of Life (both deep and shallow evolutionary time), placing spider evolution in a more robust and confident context.