Photo Credit: Chris Lukhaup
Freshwater Crayfish
The goal of our research is to explore and explain patterns of biodiversity across freshwater crayfishes (also regionally known as crawfish, or crawdads). Why Crayfish? To study biodiversity, biologist often try to pick a group of organisms that exhibit a range of characteristics across species: different sizes, different shapes, different behaviors, and so on—studying a group of organisms that all look and behave the same would be no fun. And with ~700+ species of crayfish, this diversity is not too large to the point where you can never fully grasp how many species there are, but not too small that there is little to explore. We believe that crayfish fit the bill as an ideal yet underutilized system to investigate broad-scale ecological and evolutionary patterns. Furthermore, because the eastern United States is a world's most diverse region for freshwater crayfish, our backyard is a convenient location to conduct our work.
Our research takes an integrative and comparative approach to explore patterns of phenotypic diversity while paying attention to the taxonomy and natural history of the species we study. This allows our research program to answer questions using a range of techniques, including field-based behavioral observations, laboratory experiments, and even phylogenetic comparative studies. Below you will find brief description of the types of questions our lab is interested in answering.
Photo Credits: Guenter Schuster
Sexual Selection
Competition to acquire a mate has led to some of the most exaggerated and perplexing animal traits, including narwhal tusks and the tailfeathers of peacocks. However, our understanding of how these sexually selected structures evolve and diversify remains sparse. The conspicuous claws of crayfishes serve as both weapons during competition, and signals during communication, making them an ideal trait to investigate such questions. Specifically, we are interested in studying how crayfish claws have diversified in their size, their shape, and their pinching abilities across species with diverse ecologies and behaviors.
We are also interested in how competition for mating continues after reproduction via post-copulatory sexual selection.
Photo Credits: Guenter Shuester
Diversity in claw morphology across various North American crayfish species .Photo credits: Guenter Schuster.
Behavioral Ecology of Burrowing Crayfish
Photo Credits: Guenter Shuester
Opposed to most crayfish species that inhabit permanent bodies of water like streams or lakes, a unique semi-terrestrial burrowing lifestyle has evolved several times throughout the crayfish phylogeny. Due to their reclusive, underground lifestyle and ability to engineer elaborate burrows that may reach 3 m in depth, our understanding of the behavior of these species remains limited. The majority of what we know about how burrowing crayfish species interact with one another and with their environment comes from sporadic, anecdotal reports peppered throughout the scientific literature.
By combining laboratory and field experiments, we hope to shed like on the mysterious lives of the burrowing crayfishes. The start of our work on these species has been recently published in Food Webs and PLoS ONE.
(A) A typical burrowing crayfish burrow. This specific drawing depicts a burrow with multiple entrances which lead to two tunnels that connect to groundwater (depicted in blue). (B) An adult burrowing crayfish, the Little Brown Mudbug, Lacunicambarus thomai, exhibiting daylight activity outside of its burrow. The burrow’s entrance is out of sight due to the extensive leaf litter coverage. Burrow drawing by Sam Wilson. Photo of L. thomai courtesy of John Freudenstein.
Functional and Evolutionary Morphology
Historically, a lack of understanding of the phylogenetic relationships among crayfishes has made the use of modern comparative methods impossible for this group. But more recently, several crayfish phylogenies have been reconstructed, making crayfishes ripe for modern comparative investigations. We use phylogenetic comparative methods to investigate patterns of biodiversity across the crayfish phylogeny, and how these traits differ between burrowing and non-burrowing species. Much of this work is focused on understanding how crayfish claws have diversified across the crayfish phylogeny, but we are also interested in how other phenotypic characteristics, such as body size (see image on right) and life-history traits have evolved throughout crayfishes.
Ancestral reconstruction of burrowing ordered as a discrete character using maximum likelihood. Pie charts on nodes represents the likelihood of the specific ancestor being a burrower or non-burrower crayfish. Data on bars represent the average body size values for each individual species. Species are color coded based on being a burrower (brown) or a non-burrower (blue).