|Are Bladderwrack (Fucus vesiculosus L.) holdfasts that support several fronds composed of one or several genetic individuals?|Malm, T.; Kautsky, L. (2004). Are Bladderwrack (Fucus vesiculosus L.) holdfasts that support several fronds composed of one or several genetic individuals? Aquat. Bot. 80(3): 221-226. dx.doi.org/10.1016/j.aquabot.2004.10.001
In: Aquatic Botany. Elsevier Science: Tokyo; Oxford; New York; London; Amsterdam. ISSN 0304-3770, more
Holdfasts; Regeneration; Survival; Marine
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This study examined the capacity of Fucus vesiculosus L. to propagate vegetatively, and estimated the proportion of F. vesiculosus holdfasts comprising more than one genetic individual. The investigation was conducted in the summer of 1999 in two distinct areas, both situated at the latitude of 58°N: the marine Swedish North Sea coast, and the non-tidal, brackish (6 S) Baltic Sea coast. Both field surveys of natural populations and tank experiments investigating regeneration from cut holdfasts were conducted. The proportion of holdfasts carrying both male and female reproductive fronds was estimated at various locations along the wave exposure gradient. These proportions were multiplied by a factor of 2, to correct for holdfasts comprising more than one genetic individual of the same sex. Holdfasts from the North Sea coast, growing at wave-exposed and wave-sheltered sites, uniformly had one reproductive frond per holdfast. Holdfasts at moderately exposed sites averaged 1.4 ± 0.2 reproductive fronds each; 44.1 ± 5.0% of the holdfasts with more than one reproductive frond each comprised more than one genetic individual. On the Baltic Sea coast, the number of reproductive fronds per holdfast (4.1 ± 0.2) varied little from one site to another, but the number of holdfasts comprising more than one genetic individual was significantly lower at the sheltered (4 ± 0.5%) than at the wave-exposed sites (22.1 ± 1.2%). Experimentally cut F. vesiculosus holdfasts from the Baltic Sea coast produced significantly more fronds per holdfast (30.1 ± 3.2) than did holdfasts from the North Sea coast (7.8 ± 0.8) after 4 months of growth. The results suggest that the high proportion of holdfasts comprising more than one genetic individual should be taken into account in studies where a correct estimate of the number of genetic individuals is essential for the calculation of population structure and dynamics.