My research interests broadly include topics in ecology, systematics, and evolution using molecular and morphological approaches. I primarily focus on historical biogeography, population genetics, intraspecific variation, and biomechanics. I’m interested in nearly every aspect of flattie spider (selenopidae) biology, but am also interested in dictynoid spiders and anthicid beetles, and broader questions have led me to publish papers on mutillid wasps and even vertebrates. All of my work is heavily field based; I have done field work all over, and I love it.

Phylogenetic systematics and biogeography of selenopids and related spiders

In my doctoral thesis work, I studied the molecular systematics and biogeography of Caribbean Selenops spiders (Crews and Gillespie 2010). I also revised the genus in North America, Central America, and the Caribbean, describing 21 new species (Crews 2011). As a post-doctoral researcher at the Western Australian Museum, I described several new genera and 40 new species of selenopids in the Australasian region (Crews and Harvey 2011, Crews 2013).

I am currently studying the molecular systematics of selenopids to test biogeographic hypotheses in Australia. This research involves expeditions to underexplored regions of Australia to locate and describe new selenopid species. Additionally, many Australian selenopid species are known from a single, poorly-preserved specimen and, for many, only a single sex is described. Thus, one of my objectives is to enhance taxonomic information and museum collections with new material and descriptions of series that include both sexes. A two month trip around Western Australia and the Northern Territory in 2016 funded by a National Geographic Society Waitt Grant uncovered several new species I am currently describing. Collection of molecular data from these specimens will allow us to put forth a hypothesis of evolutionary relationships for the group as well as test hypotheses about the roles of biogeography and climate in the diversification of biota across the Australian continent.

Although selenopid spiders are rather large and can occur in human dwellings and urban areas, most are described from a single sex only and I see undescribed species often. I’m always happy to collaborate on any aspect of selenopid biology, including species discovery and description.

Other aspects of selenopids I’m currently working on are:

-mating behavior in multiple genera and species, with Nicole VanderSal Jensen

-vision, with Benji Kessler and Damian Elias

-biomechanics, with Joe Spagna and Andrew Spence

-internal anatomy, with Facundo Labarque

-genera delimitation, with Matt Van Dam and Lauren Esposito


Male Selenops submaculosus, Florida
Flattie spider, being flat, Bahamas
Undescribed female Selenopid guarding her eggsac
Karaops ellenae, Western Australia


Role of ecological constraints in shaping biodiversity in the desert southwest of North America

Saltonia incerta, once thought to be extinct, is a spider found only beneath the salt crust of salt flats in the desert southwest of North America. When I first began researching this species, there were only a few specimens in museum collections from only three localities, and two of these localities are now under water because of human development. Through an extensive series of field surveys, I located Saltonia in 17 salt flats throughout the southwest discovering robust populations at some sites. However, these continue to be threatened by habitat alteration. Genetic data indicate significant population structure and very low to non-existent migration among these sites. This work provides a mechanistic understanding of how population connectivity has been impacted by the aridification of the American Southwest. The rather remarkable fact that salt flats may act as refugia for terrestrial species is a novel finding (Crews and Gillespie 2014), and suggests several interesting avenues for future study. These include conducting long term population assessments to determine how habitat disturbance affects arthropod populations in these special habitats.

Tanarthrus eating fly on salt flat, New Mexico
Saltonia incerta, Death Valley National Park
Collecting on Wilcox Playa, Arizona.