Ramet dynamics for the clonal seaweed Pterocladiella capillacea (Rhodophyta): A comparison with Chondrus crispus and with Mazzaella cornucopiae (Gigartinales)
R. Scrosati et E. Serviere-zaragoza, Ramet dynamics for the clonal seaweed Pterocladiella capillacea (Rhodophyta): A comparison with Chondrus crispus and with Mazzaella cornucopiae (Gigartinales), J PHYCOLOGY, 36(6), 2000, pp. 1061-1068
Little is known about the dynamics and the ecological interactions among ra
mets: (fronds) from populations of clonal red seaweeds. Small ramets are ve
ry difficult to tag, so their growth cannot be monitored directly, The temp
oral variation of the relationship between stand biomass and ramet density
offers information on ramet performance. We calculated this relationship fo
r an intertidal population of Pterocladiella capillacea (Gmelin) Santelices
et Hommersand (Gelidiales) from Baja California, Mexico. Biomass and densi
ty were positively correlated on an annual basis, indicating that biomass a
ccumulated without involving self-thinning among ramets, This contrasts wit
h nonclonal seaweeds, for which self-thinning among individuals occurs duri
ng growth, but agrees with other clonal red seaweeds, such as Chondrus cris
pus Stackhouse and Mazzaella cornucopiae (Postels ef Ruprecht) Hommersand (
both Gigartinales), The growth pattern for these members of the Gelidiales
and of the Gigartinales holds despite differences in holdfast morphology an
d ramet branching degree and despite differences in the capacity of coalesc
ence during early stages, known only for the Gigartinales, The positive slo
pe for the dynamic biomass-density relationship, on a bilogarithmic scale,
was statistically steeper for M, cornucopiae than For P. capillacea and for
C, crispus. This suggests that the addition of new ramets during the growt
h season may be relatively more beneficial for biomass accumulation rates f
or M, cornucopiae, This would be expected for high-intertidal species subje
cted to strong abiotic stress, for which ramet crowding constitutes a key p
rotection, Pterocladiella capillacea occurs at the mid-intertidal zone and
C, crispus at the subtidal zone, so ramets would be relatively less importa
nt in that respect.