Phlorotannin allocation among tissues of northeastern pacific kelps and rockweeds

Optimal defense theory (ODT) predicts antiherbivore defensive compounds wil l be allocated so that the most valuable or most susceptible tissues will b e best defended. The growth-differentiation balance hypothesis (GDBH) predi cts that defense allocation will be a result of trade-offs between growth a nd defense. Thus, these two theories predict opposite allocation patterns w ith respect to "valuable," actively growing meristematic and reproductive t issues, ODT predicts that meristems and reproductive tissues should have hi gher defense levels than non meristematic vegetative tissues; the GDBH pred icts the defense levels of meristems and reproductive tissues will be lower than vegetative tissues. We examined allocation patterns of phlorotannins in 21 species of kelps (Order Laminariales) and rockweeds (Order Fucales) f rom nine sites on the west coast of the United States to determine if alloc ation patterns better matched the predictions of ODT or the GDBH and to loo k for differences in allocation patterns among sites. Within-species differ ences in phlorotannin levels occurred in 10 of the 21 species examined. Mer istems of both kelps and rockweeds had higher phlorotannin levels than nonm eristematic vegetative tissues, consistent with ODT, Phlorotannin levels in reproductive tissues of kelps were higher than vegetative tissues, but lev els in reproductive tissues of rockweeds were lower than vegetative tissues , indicating that allocation strategies may follow taxonomic Lines. Allocat ion patterns differed among sites in four of the 16 species collected from more than one site. Differences in allocation patterns among sites were usu ally changes in the ratios of phlorotannins in well-defended compared to po orly defended tissues, rather than changes in which tissues were well defen ded or poorly defended. We concluded that environmental variability can hav e large effects on the concentration of phlorotannins in algae but has limi ted effects on allocation patterns among tissues.