> Research Interests & Current Projects:

Evolution of parental care and sibling cannibalism

My interests in the resolution of evolutionary conflict have recently led me to study parental care and sibling cannibalism in marine whelks. Many female whelks lay on hard surfaces egg cases that house developing larvae. Where rocks and algae are in short supply, whelks will sometimes lay eggs on each other.
           
Several years ago, we re-discovered a previously undocumented pattern of oviposition in a whelk (Solenosteira macrospira) from the Gulf of California: only males carry egg cases. This pattern of parental care is reminiscent of several other well-documented cases of male parental care in organisms such as giant water bugs. But what sets the scenario in Solenosteira apart from all other cases in which there is exclusive male care of offspring is that Solenosteira males have no obvious way of ensuring paternity, despite ample morphological (although not genetic) evidence from other whelks that females can store sperm. Thus, there is the potential for substantial conflict between males and females: from a female's perspective, it appears that any living male provides a suitable oviposition site, whereas a male should not care for offspring sired by another male, particularly if he cannot ensure that he garners a mating in exchange.

There is another level of conflict that occurs in Solenosteira. Because females store sperm, and (in the laboratory, at least) mate with multiple males, a single egg case, housing >100 developing larvae, contains both full- and half-sibs. From the time of oviposition to hatching, the number of larvae within an egg case declines, sometimes leaving <10 juveniles at the time of hatching. Presumably, larvae cannibalize one another (adelphophagy). As in conflicts that arise in colonies of social insects, larvae should distinguish full- from half-sibs, and preferentially consume their more distant relatives.

To understand how these conflicts between males and females, between parents and offspring, and among offspring play out, we have developed microsatellite markers that will allow us to determine the incidence of multiple paternity and maternity among egg-capsules deposited on individual males. Similarly, we are characterizing the composition of sibships within egg capsules as the larvae develop, and in so doing, determine whether adelphophagy is preferentially directed toward half-sibs. Finally, we are beginning lab and field studies of mating behavior, to evaluate how many egg-cases are laid per mating, how often matings occur, whether males exhibit any behaviors that would increase their certainty of parentage, and what determines male quality.