social behavior - symbioses - plant-insect interactions - human pregnancy
Over my career, I've mostly followed my interests, but I've been guided by mentors, collaborators and students. This means we've had to learn something about ecology and behavioral ecology, molecular biology, chemistry, and of course evolution.
Social aphids defend their kin from predators. They can tell us about evolutionary convergence in sociality, as well as unique aspects of social evolution
We've worked on social behavior in insects. Mostly, we've focused on aphids - one of the curiosities among the social insects. For years, I have been motivated to use aphids to test general theories about social evolution. There are multiple origins of social behavior in aphids. Those that are social vary themselves how "complex" their behavior and societies are. You can use that variation to do really powerful comparative evaluations of many kinds of questions.
This comparative focus culminated in an edited volume with Dustin Rubenstein, from Cambridge University Press. Social aphids do really strange things. For one, they attack other insects. This is a very odd behavior for a plant-feeding bug. Of course, aphids are fascinating in their own right. For such small sap-sucking and pestiferous insects, they have been surprisingly important in diverse areas of organismal biology. Even fruit flies are not models for both insect evo-devo and insect symbioses.
The kinds of questions we have asked about sociality in aphids:
What is the kin structure of groups of aphid groups? In other words, is the neighborhood itself structured?
What is the evolutionary history of cheating in aphid societies?
How costly is cheating to aphid groups?
For aphid species that vary in social behavior, how effective are they at defending themselves from predators?
What is the mechanistic basis of effective defense against predators? Can we use the comparative potential of social and non-social behaviors in aphids to identify the key changes involved in colony defense?
And yes, we've studied symbiotic and mutualistic interactions, not working with aphids, but rather with another tiny insect - gall midges. Many have truly crazy, complex interactions with other species - with plants, fungi, and parasitic wasps for starters, often at the same time (the so-called "ambrosia gallers"). Many groups are hyper-diverse, like those in the genus Asteromyia.
These interactions are likely key to understanding their diversity. Our last paper with gall midges, led by Jeremy Heath and John Stireman, addressed the question about the relative roles of bottom-up (resources) versus top-down (natural enemies) factors in driving adaptive radiations, something we all have been thinking about for a long time. Which is more important in gall midges? Read the paper!
Gall midges have complex interactions with plants, fungi and natural enemies. They can tell us about how species interactions shape biological diversification
The kinds of questions we have asked about Asteromyia gall midges, goldenrod, and fungal symbioses:
How diverse is the gall midge Asteromyia carbonifera? is there evidence of cryptic diversity?
What is the relationship between Asteromyia and host plant diversity?
What is the relationship between gall midge diversity and the diversity of their fungal symbionts? Is there evidence of co-evolution?
Is Asteromyia undergoing an adaptive radiation on goldenrod?
How has lateral gene flow contributed to facilitating the interaction between insects and their fungal symbionts?
Insects on plants that express toxic defenses can tell us about how animals adapt to challenging environments
And related to our work with gall midges, we've studied plant-insect interactions, most recently working on milkweed and the oleander aphid. Stephanie Birnbaum in my lab spearheaded efforts to unlock some of the mysteries of how these aphids manage life on such toxic host plants.
In particular, we were interested in the role of variation in gene expression in the oleander aphid's ability to manage the challenging task of feeding on milkweeds that vary in toxicity.
But my interests in plant-insect interactions go back to my MSc days, when I worked with the milkweed leaf beetle, which also manages that same difficult task.
The kinds of questions we have asked about interactions between oleander aphids and milkweeds:
What mechanisms allow aphids to succeed on milkweeds that vary in toxicity?
How does variation in gene expression facilitate adaptation to environmental challenges?
How does plasticity in gene expression evolve in response to natural and synthetic xenobiotics, and are there synergies between the two? Do they evolve in the same way and direction?
And finally, we've worked on human pregnancy, as part of a big collaboration with the March of Dimes, led by Lou Muglia now with the Burroughs Wellcome Fund. Antonis Rokas, Tony Capra, myself and many others have been working hard to understand the evolution of birth timing in humans, in order fight the scourge of pre-term birth.
Understanding how pregnancy evolves and varies across mammals helps us to understand adverse outcomes in human pregnancy.
The kinds of questions we have asked about pregnancy, birth-timing and disease in humans:
Can we create a gene-centered database that helps to identify the loci underlying risk for pre-term birth?
Is there evidence of recent positive selection on enhancers in the human genome? How do these signatures vary across tissues?
Can we define a way to use integrated, diverse datatypes in order to prioritize genes for disease discovery?
Is there evidence of positive selection on genes involved in human sialic acid biology?
Have diverse modes of selection shaped the evolution of genes involved in pre-term birth?
