Meeting Abstract
Tigriopus californicus copepods are small benthic crustaceans with high levels of genetic structure among sites in coastal California and Oregon. Divergence in mitochondrial genotypes has been shown to be as high as 20% between California populations. Crosses among these genetically divergent populations produce hybrids with reduced fitness due to incompatibilities in co-functioning mitochondrial and nuclear OXPHOS proteins. Thus, post-zygotic fitness effects likely play a role in isolating copepod populations. Here we tested the hypothesis that pre-zygotic mechanism may also play a role in isolating copepod populations. Various copepod species, including T. californicus, have been documented to use chemical signals in mate choice. While avoidance of inbreeding has been demonstrated experimentally in genus Tigriopus, mate choice to avoid outbreeding beyond population boundaries has not been well studied. We first examined the hybrid viability in crosses between widely geographically separated T. californicus populations: Santa Cruz, CA (SCN) x Seal Rock, OR (SR) (1046 km), and Abalone Cove, CA (AB) x Seal Rock, OR (1524 km). We found that offspring from both crosses showed decreased survival rates, extended development times, and increased sterility when compared to control crosses (SR x SR). Given the fitness cost to hybrid pairing, we predicted that males would preferentially clasp same-population females versus other-population females. Preliminary data suggest that male copepods use chemical cues to avoid mating outside of local population boundaries.
