RESEARCH INTERESTS
I am an ecologist interested in the ecology and evolution of species interactions and how these interactions explain the diversity of behaviors, life history strategies and forms found in nature. Much of my previous work has been in marine environments (both benthic and planktonic), but this “bigger-picture” approach allows me to consider fundamental questions wherever they take me.

My recent research lies at the intersection of studies of predator-prey interactions within the marine planktonic environment. The marine plankton is characterized by a complex cast of seasonally variable predators and prey. Some of these organisms are temporary residents of the plankton. Many nearshore animals such as crabs, some snails and worms, sea urchins, and sand dollars spend their earliest days as free-swimming larvae prior to settling to the sea floor as juveniles. Armed with little endogenous food (such as egg yolk), and most lacking obvious defenses, many planktonic larvae must feed and protect themselves before metamorphosing into an adult and settling near shore.

Below are three examples of planktonic larvae. Image A shows the larva of a checkered periwinkle snail swimming with fleshy ciliated lobes (Scale = 100 µm). Image B shows a crab larva with a much smaller larval snail lying near the tip of it's dorsal spine (Scale = 1 mm). Image C shows a larval sand dollar in the process of cloning itself following exposure to cues indicating the risk of predation (Scale = 100 µm). (All photos by D. Vaughn).

These microscopic larvae will lead very different lives than they will as adults... if they survive to adulthood. Larval mortality is estimated to be extremely high in marine planktonic environments. Although the causes of mortality are poorly understood, predation is considered a significant source of mortality for the eggs, embryos and larvae of marine organisms. With little protection and provisioning, other mechanisms may have evolved to increase survival of larval offspring during prolonged planktonic development.

Developmental plasticity is one mechanism that can counter the effects of “growing up” all alone in a risky and unpredictable planktonic environment. A particularly well-documented category of developmental plasticity is the induced defensive responses of prey organisms to predators. Inducible defenses are well documented in varied habitats to a diversity of predators and throughout development and include protective alterations in behavior, chemistry and morphology. Despite the pervasiveness of inducible defenses exhibited by organisms in all major ecosystems (terrestrial, aquatic, and marine), reports of these responses in marine planktonic animals, including marine larvae, have been limited to induced behaviors to avoid or escape predatory encounters. Rarity of predator-induced changes in the defensive morphology of marine zooplankton, such as the development of longer spines or stronger shells, would imply a difference in predation risk compared to those experienced by other aquatic and terrestrial organisms. On the other hand, the presence of such plasticity would imply that risks are modified by developmental responses. In the latter case, might these responses simply have been overlooked in marine zooplanktors?

My thesis research provides a first investigation of inducible morphological defenses in marine zooplankton, and more specifically in marine planktonic larvae. In short, I have asked – Do marine zooplankton respond to predators through induced protective changes in morphology and shifts in life histories? And if so, what is the ecological and evolutionary significance of these types of predator-induced defenses for larvae that spend the first few weeks of life growing and developing in the sea?

The results of my research suggest that predator-induced defensive responses in marine zooplanktors may be as diverse as those documented in prey organisms in other environments. In some cases the responses of marine zooplankton to predators were both unexpected and previously undocumented in any other environment. For instance, apart from sand dollar larvae, there are no other examples of cloning and reduced size as an inducible defense.

To learn more click here.

In initiating the morphological part of assessments of predator-induced behavioral, chemical and morphological defenses in marine zooplankton, the results from this research will also further our understanding of the ecological contexts that favor selection for different kinds of developmental plasticity. Future studies will reveal the frequency or scarcity of inducible defenses in marine zooplankton, thereby providing useful comparisons of the role of developmental plasticity across a myriad of habitats in the marine realm and beyond. Predator-induced defenses in marine planktonic larvae are part of that story.

LAST BUT NOT LEAST ... here is a verse from one of my favorite poems by renowned embryologist (and sometime poet), Walter Garstang. In this poem, Garstang writes of adaptive changes in the morphology and the behavior of marine larvae that may reduce vulnerability to planktonic predators. How perfect is that?