Research Interests

An enormous variety of marine animals spend the early parts of their lives as specialized planktonic larvae “…in an unregulated state of nature [that] is solitary, poor, nasty, brutish, and short.” (Thomas Hobbes, Leviathan). Why they do this and what are the consequences of doing something else?

In many species, adults engage in high-risk sexual behaviour by dumping their gametes into the plankton where (with luck) sperm meets egg to make zygotes. Fertilization rate is often very low, and mortality of offspring is usually very high, so females make very large numbers of tiny, cheap eggs in the hopes that a few will survive. These eggs develop into tiny, vulnerable larvae that often have distinctive adaptations for swimming, feeding, growing, and fending off predators. In some groups, these larvae are so highly specialized for planktonic life that they do not resemble the adult forms at all (for example, the animal at left is a sea urchin, about 1 mm in length, a week or so before metamorphosis into the adult form on the right).These larvae must grow (because initial egg size is much smaller than the size of juvenile stages) and growth is slow (because food particles are often very dilute in the ocean), so the planktonic stage may last weeks or months and result in dispersal and gene flow across large distances (even across ocean basins). In these species, the transition from the larval lifestyle and habitat to the adult involves complex behaviours for selection of a settlement site, followed by a dramatic metamorphosis. In many respects, these life histories are similar to wind-pollinated grasses (with aerial pollen and tiny seeds) and to insects or amphibians (with distinctive larval and adult stages).

But in many other species, often closely related to those with planktonic larvae, adults are much less cavalier about the production & protection of their offspring. These species have some combination of highly derived life history traits, often including:

• Hermaphrodite adults

• Self-fertilization

• Internal fertilization

• Complex gamete exchange (sometimes with mate selection & courtship)

• Large and expensive eggs in small clutches

• Rapid embryonic development without feeding or growth

• Limited larval dispersal

• Brood protection (in egg capsules or the body of the parent)

• Sibling cannibalism within the brood mass

• Direct development from the zygote to the adult form

• Live birth of juveniles

   

In many respects, these alternative life histories resemble terrestrial vertebrates (with development in egg shells, wombs, or pouches) and animal-pollinated plants (with direct pollen transfer).

My lab group studies the evolutionary genetics of reproductive variation, mainly in echinoderms. This work uses knowledge of reproductive traits (either measured by us or by others) set in the context of known phylogenetic relationships and ideas about the direction and pattern of evolutionary changes in modes of reproduction. We’re interested in understanding the population genetic effects of these evolutionary changes in mating system, egg size/number tradeoffs, dispersal ability, and larval morphology.

Most of our current work involves population genetics and life history evolution in asterinid sea stars like the eastern Pacific bat star Patiria miniata. We do comparative work on a variety of other species in the same family from the Indo-Pacific and the Atlantic. This work takes advantage of well-known phylogenies for asterinid species and genera with different modes of reproduction & development, including extreme forms with small, self-fertilizing hermaphrodite adults, non-planktonic larval development in egg masses or viviparous brooding with live birth. Some live bearers have direct development followed by sibling brood cannibalism in the 'womb'. 

We collaborate on this work with researchers in Canada, Australia, and at several US universities.

Prospective graduate students should have well-developed curiosity about organisms, a strong work ethic, independence, creativity, and a sense of humour. Practical skills and experience with either reproductive ecology of marine invertebrates or molecular methods for population genetics and phylogenetics help a lot. FABulous collegial support is provided by members of the organic evolution group. Contact me about opportunities for graduate study.

 For recent publications follow the link below to the FAB* website collection of PDFs.