RESEARCH
RESEARCH INTERESTS
I am a broadly trained scientist interested in the ecology, evolution, and
behavior of reptiles and amphibians. I study how spatial and temporal changes in ecology and environment influence behavior, morphology, genetic variation, and biological diversity across biological scales, from genes to species.
How do ecology and environment influence social interactions, and
what are the implications of swift environmental change on these interactions? How does behavior modify the relationship between organism and environment? To answer these questions, I use a combination of large-scale field studies, laboratory behavioral experiments, and phylogenetic comparative analyses on individuals, populations, and species of color polymorphic Podarcis lizards.
Color polymorphism has evolved in every major animal group in the tree of life, and are useful systems for studying interactions between genes, phenotypes, behavior, and the environment because morph variation in phenotype (color) has a discrete underlying genetic basis that is often genetically linked to variation in other phenotypic traits (behavior, morphology). My research goal is to understand how ecology, environment, and organism interact to generate, maintain, or erode biological variation in human-modified and natural populations.
Snaggin' Podarcis erhardii color morphs for science with Dr. Donihue (2018)
CURRENT RESEARCH
TRAIT DIFFERENCES AMONG COLOR MORPHS IN PODARCIS ERHARDII
Color polymorphism defies evolutionary expectations as striking, genetically-based phenotypic variation is maintained within a single species. Yet, color polymorphism is quite common lizards - it has evolved independently multiple times in distantly related species across the lizard family tree. Color polymorphisms offer a great opportunity to study how variation, both genetic and phenotypic, is generated, maintained, and lost in natural populations. Check out some of our published work on color morph trait differences in Aegean wall lizards (Podarcis erhardii). Our findings suggest that morph colors are related to differences in traits that are crucial for social interactions and competitive ability, illustrating the need to look beyond color when studying polymorphism evolution.
Read our paper on morph color, size, bite force, and chemical signal profiles in PeerJ
Read our paper on differential body temperature preferences between P. erhardii color morphs on bioRxiv
Read our paper on morph differences in habitat use and ectoparasite loads in Amphibia-Reptilia
More interesting work on color morph traits (aggressive behavior, microbiomes, and morphology) in collaboration with undergraduate and master's students is underway !
COLOR MORPH-CORRELATED BEHAVIOR IN PODARCIS ERHARDII
Space is a limited resource that many animals need to access for basic functions such as feeding and reproductive opportunities. Competition over access to space can induce aggressive behavior, which may result in differential access to crucial resources related to survival and fitness. The Aegean wall lizard, Podarcis erhardii, is a tri-color polymorphic lizard that eponymously inhabits dry stone walls where they display to other lizards, access food, safely thermoregulate, and shelter from predators. Adult male color morphs exhibit physical differences in size and chemical signaling profiles, but nothing is known about potential morph-specific differences in behavior. Here, we conducted the first behavioral experiments on P. erhardii color morphs to characterize morph differences in behaviors involved in accessing and occupying a limited space resource. We captured 60 adult male lizards (20 orange, 20 yellow, and 20 white) and constructed contests between individuals of each morph type. Experimental trials conducted in a neutral laboratory arena revealed that male color morphs exhibit different behaviors and abilities to access a small stone wall with a heat source. We think these alternative strategies are involved in the evolutionary maintenance of color polymorphism.
Read our paper on morph-correlated social behaviors and contest abilities in Animal Behaviour !
Read our paper on differences in color morph escape behavior in Behavioral Ecology & Sociobiology
THE EVOLUTION OF COLOR POLYMORPHISM IN THE LIZARD FAMILY LACERTIDAE
Color polymorphism – two or more heritable color phenotypes maintained within a single breeding population – is an extreme type of intra-specific diversity widespread across the tree of life but rarely studied in a comparative framework. Color polymorphism is thought to be an engine for speciation, where morph loss or divergence between distinct color morphs within a species results in the rapid evolution of new lineages, and thus, color polymorphic lineages are expected to display elevated diversification rates.
Lizards of the family Lacertidae have evolved multiple lineages with color polymorphism, but lack of a complete and robust phylogeny for the group had made comparative analysis difficult. Here, we produced a comprehensive species-level phylogeny of the lizard family Lacertidae to reconstruct the evolutionary history of color polymorphism and test if color polymorphism has been a driver of diversification. Accounting for phylogenetic uncertainty, we estimated an ancient macroevolutionary origin of color polymorphism within the Lacertini tribe (subfamily Lacertinae). Color polymorphism most likely evolved several times in the Lacertidae and has been lost at a much faster rate than gained. Evolutionary transitions to color polymorphism are associated with shifts in increased net diversification rate in this family of lizards. Taken together, our empirical results support long-standing theoretical expectations that color polymorphism is a driver of diversification.
Thanks to the Society of Systematic Biologists for funding this work! Read the full story in Systematic Biology.
GEOGRAPHIC VARIATION IN COLOR POLYMORPHISM ACROSS ISLAND POPULATIONS OF PODARCIS ERHARDII
Evolutionary theory predicts that color polymorphic species are ripe for speciation due to dramatic phenotypic variation between color morphs within and among populations. One could imagine, for example, that across an entire species' range, that color morphs might be better suited to certain environments and ecologies, or that due to random chance a color morph might be lost from a population. But how does population-level variation in color polymorphism change across an entire species distribution? And what affect does this geographic variation in morph presence have on the mode and tempo of divergence (both morphological and genetic) among populations?
TeamSavres 2017-2019 (Team Lizards in Greek) and I travelled to the very farthest reaches of the Aegean wall lizard's (Podarcis erhardii) distribution, exploring more than 40 Aegean islands by ferry, fishing boats, and kayaks, in search of wall lizards to describe and explain color morph and genetic diversity across the archipelago. So far, we've found that color morphs in P. erhardii have been completely lost from some populations, and the pattern of morph loss seems to be ordered and non-random! We are quantifying the rate of morph loss across populations. We're also using environmental and ecological data collected at each site to try to understand drivers of morph loss.
This work has been the thrill of my life, and none it would have been possible without companionship and help from all of the wonderful TeamSavres field assistants. Ευχαριστώ πολύ Adam Rosso, Indiana Madden, Cynthia Ramos, Chris Vetros, Robert Degen, Shelby Stadler, and Cole Ayton! Thanks also to lab assistants Jazmin Reyes, Mindy Fernandez, and Liz MacDonald for extracting big beautiful fragments of lizard DNA. This work is a long-term collaboration with Professor Panayiotis Pafilis at the National and Kapodistrian University of Athens.
CITY SICULUS: ITALIAN WALL LIZARDS IN THE USA
Several species of Podarcis lizards have repeatedly established thriving populations from introductions of a few individuals all over North American cities from Boston and Cincinnati to San Diego and LA and all the way up to Vancouver, often displacing native species. In San Diego and LA, introduced Italian wall lizards, Podarcis siculus, have established expanding populations that actively exclude native Western fence lizards, Sceloporus occidentalis. How do a couple of lizards from Italy explode into huge populations that push out native species that have been evolving in these places for millennia? Does Podarcis' long evolutionary history with humans give them a leg up for co-existing in cities with us? Having an understanding of the genetic, environmental, behavioral, and ecological properties of successful species invasions in cities provides insights into urban evolution and how species deal with sudden environmental change.
I am sampling Italian wall lizards at the San Pedro, LA introduction site where the population (that started with just 7 individuals) is expanding fast. So far, I've found dramatic differences in anti-predator behavior in space (from the core to the expanding edges of the population) and through time (lizards are becoming used to human presence)! We are quantifying the rate of behavior change since their introduction to LA, along with other traits. We're also using genetic, environmental, and ecological data collected at both the source (Taormina, Sicily, Italy) and introduction (San Pedro, Los Angeles, USA) sites to try to understand how wall lizards are so successful in novel environments.
This work is in collaboration with Dr. Greg Pauly at the LA County Museum of Natural History, Anusha Bishop at UC Berkeley, Bree Putman at Cal State San Bernardino, Eric Gangloff at Ohio Wesleyan University, and Peter Bednekoff at Eastern Michigan University.
RESEARCH FUNDING
Herpin' ain't easy, but it's necessary. Collecting genetic, phenotypic, and environmental data from the field is critical to advance our understanding of nature and conserving reptiles (and all biodiversity!) in a rapidly changing world. Thanks very much to the organizations that have funded TeamSavres research over the years.
