Professional Experience and Research Activities

The following are my professional, non-teaching experiences to date:

Present appoint

2011-present      Assistant Professor, Biology, Long Island University-Post (Brookville, NY) 
2011-present      Research Associate, Smithsonian Environmental Research Center (SERC) (Edgewater, MD)

2009-2011            Postdoctoral Fellow, Marine Science Network, Smithsonian Institution

2010-2011            Adjunct Faculty, Miami University (Miami, OH)                                                   

2010-2011            Managing Guest Editor, Biological Invasions Special Issue, Environmental Research

2009-2011            NSF Postdoctoral Scholar, Faculty Institutes for Reforming Science Teaching

2009                       Instructor, Goucher College (Towson, MD)

2007-2009            Postdoctoral Fellow, Marine Invasions Lab, SERC

2007-2008            Guest Editor, Marine Bioinvasions Issue, ICES Journal for Marine Science



As a researcher interested in global marine distribution patterns and processes, I have developed a diverse research program involving biodiversity, population genetics, parasite ecology, and biogeography—as well as the unique and integrative insight that can be gained from studying biological invasions. Recently, biological invasions have become recognized as a major contributor to the global (and often disjunct) distributions of many marine species as a result of their movement and establishment via human transport mechanisms. Invasion research is therefore important not only from a conservation perspective but can provide theoretical and practical understanding of population and community level influences of novel species, and can also serve as an important teaching tool for students and the general public. Marine invasions are a major part of human-induced global change, including population, community, and ecosystem-level shifts in marine biota, genetics, and the environment. I have examined many integrative aspects of marine invasions, focusing in three major areas: global distribution patterns (biogeography and phylogeography) of free-living and parasite species, population genetics and evolutionary mechanisms affecting native and non-native populations, and parasite ecology in native and non-native populations (including impacts on behavior and physiology). I employ marine invertebrates as model organisms as they have contributed vast numbers of introductions globally, and they also serve as hosts to marine parasites, which are a fundamental but often overlooked component of many marine systems, and which can become cryptic invaders themselves. 

The parasite group I have primarily studied are digenean trematodes, which are trophically-transmitted parasites that use multiple taxa as hosts and typically infect specific snail species as first-intermediate hosts. I have studied two major trematode life cycles, shown below. Both use Littorina spp. snails as first-intermediate hosts, crustaceans (Figure 1A) or fish (Figure 1B) as second-intermediate hosts, and seabirds as definitive hosts. 

FIGURE 1a                                                                        FIGURE 1b
Figure 1A. Trematode infection cycle for the trematode, Microphallus similiswhich uses Littorina sp. as first-intermediate hosts, the green crab (C. maenasas a second-intermediate host, and seabirds as the definitive hosts.

Figure 1B. Trematode infection cycle for the trematode, Cryptocotyle lingua, which uses Littorina sp. as first-intermediate hosts, numerous species of fish as a second-intermediate host, and seabirds as definitive hosts.

Below (Figure 2) are the three Littorina sp. I have frequently explored in the North Atlantic (demographics, biogeographies, parasites, and genetics).
 Figure 2. North Atlantic Littorina sp. snails.


This past summer (2013), I had a summer intern, Zack Holmes, who helped me re-investigate research performed by my former advisor, Dr. Jeb Byers, myself, and colleagues (Byers et. al., 2008), on the common periwinkle snail (L. littorea’s) North American distribution and parasite ecology (10 years later) to explore temporal effects of trematode prevalence in snails and correlation with definitive host abundance. We traveled from Long Island to eastern Nova Scotia, collecting samples in the low and high intertidal zone from 25 different locations along the coast. We are currently analyzing the vast amount of data we collected during the summer related to the project.

Zack in the field collecting snails!

Last summer (2012), I supervised a summer intern on a project related to the effects of parasitism on behavior and physiology in the globally invasive European green crab (Carcinus maenas) on the east coast of the US (see pictures from that endeavor below). For this project, I collaborated with Dr. Blaine Griffen, University of South Carolina, on an NSF ROA award related to his NSF-funded project. In particular, this project explores the physiological and behavioral impacts of trematode parasitism on C. maenas. It involved experimental work to create infected and uninfected treatments of the crab along an infection gradient; we then video-taped for behavior, and finally dissected all crabs (n=70) for parasite infection intensity and physiological indices. The analyses of these data are ongoing, but with this important baseline data completed, we would like to later explore possible effects of both predation (e.g., shorebirds) and competition (specifically with Hemigrapsus sanguineus) on infected versus uninfected green crabs.

These are pictures from summer 2012 research at the Isles of Shoals, where I spent about 3 weeks doing research with colleagues on the European green crab (Carcinus maenas), pictured in flow through in the last picture!

With my graduate student, Leidy Leon, I am currently working on a new project related to L. saxatilis, involving locally-adapted phenotypes (‘ecotypes’) of the crab, which depend on the environment. These ecotypes are well-studied in Europe, but little is known about them in N. America. We are examining two ecotypes in particular (‘barnacle’ and ‘typical’) in populations from Nova Scotia to Long Island (encompassing a large portion of the species’ western Atlantic range), collecting morphological/phenotypic, life history (specifically reproduction), ecological, parasite, and genetic data for each ecotype. In a long-term laboratory experiment, I am also currently examining growth in each ecotype because the two ecotypes appear to demonstrate significantly different maximal and average sizes in natural populations.

Possible 'ecotypes' of L. saxatilis in eastern North America. The first is the barnacle ecotype, which is found associated with barnacles and is typically smaller and demonstrates characteristic patterning on its shell, and the second is the 'typical' ecotype which is generally larger, shows a wide variety of colors, and is associated with rocks, cobbles, and boulders in the upper intertidal zone.

I have been involved in several different projects related to marine parasites, aquatic invasions, benthic ecology, and population genetics, which are described below. These represent select descriptions of projects I have been involved with over the past several years.

Littorina saxatilis phylogeography:
I have studied the global distribution of the rough periwinkle, L. saxatilis, including native, introduced, and cryptogenic populations in North Atlantic, South Atlantic and Pacific regions. In particular, I am involved in three collaborative efforts exploring: A) North Atlantic phylogeography of L. saxatilis (Panova et al., 2011, PLOS One) and comparative phylogeography of congener, L. littorea,  with colleagues in Sweden. B) The introduced population of L. saxatilis in San Francisco Bay on the Pacific coast to verify source, vector, and timing of introduction. C) a cryptogenic population in South Africa with colleagues at the University of Cape Town. The later two efforts are still in progress. In all of these populations, we have also collected data on parasitism to compare across regions (native, definitively introduced, and cryptogenic). See Figure 3 below. 

Figure 3. This demonstrates the regions we have collected data for the global distribution of Littorina saxatilis.

Carcinus maenas population genetics
In a project funded by the Census of Marine Life, I collaborated with colleagues on population genetics of the European green crab, Carcinus maenas, and the spread of new genotypes from Nova Scotia into the US. The manuscript for that project was published in PNAS. We have also investigated the recent introduction of the crab to Newfoundland and have used genetics, species demography, and coastal shipping records to help piece together the source, vector and timing of the introduction. Inference of source populations was possible due to an admixture zone in Nova Scotia comprised of southern and northern genotypes corresponding with the crab’s two historical introductions (Figure 4), which were also represented in Newfoundland. These data further highlight the importance of population genetics studies of invasive species as they can reveal likely sources of introduction, helping managers pinpoint populations on which to focus management efforts (Blakeslee et al. 2010, Diversity and Distributions). 
Figure 4. This figure presents Northwest Atlantic and Newfoundland haplotype frequency diagrams (pie charts) for populations include in the Blakeslee et al. (2010) study. Our investigation demonstrates the division of the crab's introduced northwest Atlantic range into three areas dominated by different haplotypes: 1) eastern Nova Scotia, representing haplotypes (blue, white, black) from the crab's secondary cryptic introduction from northern Europe; 2) central/western Nova Scotian and Canadian Bay of Fundy, representing an admixture of haplotypes from both introduction events; 3) US populations, representing haplotypes (red, pink) from the original introduction from southern Europe to mid-Atlantic and southern New England in the US (From: Blakeslee et al. 2010).

Ilyanassa obsoleta and trematode parasite population genetics:
I am also finalizing research on a host-parasite population genetics study of the highly abundant eastern mudsnail, Ilyanassa obsoleta, which was introduced to western N. America in the early-mid 1900s and is infected by just a subset of its native eastern N. American trematode parasites (Blakeslee et al., 2012). My results demonstrate a differential effect of introduction on the genetic diversity and population genetics of the host snail compared to its trematode parasites (Blakeslee et al., in prep). 

Asian shorecrab abundance, diversity, and parasites
I was also involved in a project exploring parasitism in the invasive Asian shorecrab, Hemigrapsus sanguineus, and the effects of parasitism load and diversity on competition with an older invader, Carcinus maenas (Blakeslee et al. 2009, MEPS). In Long Island, I have been collaborating with a colleague at Adelphi University, Aaren Freeman, on the distributions and demographics of native panopeid mud crabs and the invasive Asian shorecrab (H. sanguineus), which is highly abundant on Long Island shores. We are interested in possible negative interactions between the invasive on the natives, which may be resulting in reduced abundances of natives in areas where the invasive crab is especially abundant. We are also exploring the distribution and spread of a newly arrived rhizocephalan barnacle, representing a likely range expansion from invasive mid-Atlantic populations (Freeman et al., in press), which infects the native mud crabs and castrates them. We intend to continue our survey of these populations to determine if the arrival of the invasive parasite could result in community-wide impacts among these different crab species, as well as their competitors, predators, and prey.

Comparative parasite biogeographies in two invasive snail hosts:
Finally, in a comprehensive investigation of parasitism in two marine snails with overlapping native (east coast) and introduced (west coast) ranges in N. America (Figure 5a), we found that invasion history significantly affected parasite biogeographic patterns in introduced populations, which showed much lower parasite richness and prevalence for the newer invader (L. saxatilis) compared to the older invader (Ilyanassa obsoleta) (Figure 5b). This was likely influenced by several mechanistic factors, including time since introduction, vector type, propagule pressure, and host availability (Blakeslee et al., 2012). Related to this research, I am also finalizing research on a host-parasite population genetics study of the eastern mudsnail, I. obsoleta, and its trematode parasites. My results (in progress) demonstrate a differential effect of introduction on the genetic diversity and population genetics of the host snail compared to its trematode parasites (Blakeslee et al., in prep).


FIGURE 5A                                                                        FIGURE 5B

Figure 5a. This figure shows maps of sampling locations for two west coast invasive snails, Ilyanassa obsoleta (eastern mudsnail) and Littorina saxatilis (rough periwinkle), compared to their overlapping native range on the east coast of North America.

Figure 5b. The two snails show significantly different parasite richness and prevalence, which probably relates to their differing invasion histories and timing.