Studying population connectivity using geochemical tags
We have used calcified (aragonite) structures in marine invertebrate and fish larvae as natural recorders of dispersal pathways. We analyze metal incorporation (e.g., Ba, Sr, Mg, Pb, Mn, Zn, Ce) into larval otoliths, statoliths (see Fig. 1) and protoconchs using inductively coupled plasma mass spectrometry (ICP-MS). We validate the use of these structures through culturing experiments that examine which factors are important in determining metal incorporation rates into hard parts.
We maintain a strong interest in examining the ecology and dispersal patterns of Kellet’s whelk, Kelletia kelletii, larvae. Kellet’s whelk is a common predatory gastropod in southern California. In the past few decades, this species extended its range from its historic northern limit at Point Conception to its present limit in Monterey Bay. My research showed that the recently established populations north of Point Conception exhibit sporadic recruitment pulses. These may be due to limits on northward dispersal of larvae by prevailing current conditions during their reproductive season. Former graduate student Sara Simmonds further validated the use of statoliths to track dispersal of this species across its entire geographic range, and along with collaborator Brian Kinlan, created a range-wide connectivity matrix for the species. In our continuing work with K. kelletii, we hope to examine the relative importance of dispersal in determining patterns in population structure across the range, and in the relative importance of linkages among populations in maintaining populations at the edges of the range.
We have also done some preliminary work with California grunion, Leuresthes tenuis, the Olympia oyster, Ostrea lurida, and the California sea hare, Aplysia californica, to demonstrate that calcified structures can be used to track dispersal and population connectivity of these species.
Studying population connectivity using genetic techniques
We collaborate with Dr. Doug Eernisse (CSU Fullerton), Dr. Crow White (Cal Poly San Luis Obispo) and Dr. Rob Toonen (U. Hawaii) to study population genetic structure of Kellet’s whelk and Olympia oysters using a variety of molecular markers including mtDNA, microsatellites, and SNPs. We use these markers to infer connectivity over ecological and evolutionary timescales.