Natural variability in zygote dispersal ofAscophyllum nodosumat small spatial scales

Abstract

Summary1. Dispersal of propagules of marine benthic species may contribute to variation in the structure and dynamics of populations. Ascophyllum nodosum dominates the midintertidal zone of sheltered rocky shores in the north-west Atlantic, and populations often consist of large, mature individuals and few newly recruited thalli. 2. We investigated the dispersal of zygotes of A. nodosum at three sites on Swans Island, ME, USA, to determine its variability under natural conditions and to test whether limited dispersal explains recruitment patterns. 3. At each site we released artificially fertilized, marked zygotes from a single point during the rising tide, and sampled their dispersal using two methods: sampling the water column to track the dispersing cloud of zygotes; and assaying caged ceramic tiles affixed to the shore for the presence of marked zygotes. 4. At all sites, zygotes were diluted to ≤ 1·3% of the initial concentration within 8-12 min of their release. The mean direction of transport was correlated with both wind and tidal current direction at only one site. The most dense settlement occurred at this site, suggesting greater local reproductive success. 5. Regression analyses based on settlement densities suggest that a quadratic model fit the data best for all sites. Quadratic terms occurred in the direction normal to flow, and are interpreted to represent turbulent transport and diffusion. Both linear and quadratic terms were significant parallel to flow, and we ascribe these to advective transport without and with turbulent mixing, respectively. 6. The range of zygote dispersal exceeded 6 m from the source, and therefore cannot explain the exponential decline of recruits in large patches ( ≈ 10 m diameter) within adult stands of A. nodosum . 7. Migration of zygotes between populations is unlikely, but their local dispersal may strongly influence the spatial and temporal dynamics within populations.

Origin ofFucus serratus(Heterokontophyta; Fucaceae) populations in Iceland and the Faroes: a microsatellite-based assessment

“…It is dioecious, perennial (3-4 years), and reproduces sexually (annually) with no vegetative reproduction, either via holdfast sprouting or vegetative propagules (Malm et al, 2001). Dispersal of eggs is restricted to within 1-2 m of the parent (Arrontes, 1993), although distances >6 m are possible, as have been reported for F. vesiculosus and the related genus, Ascophyllum (Serra˜o et al, 1997;Dudgeon et al, 2001;Engel et al, 2005). The genetic consequences of low dispersal were demonstrated in a recent population genetic study showing that the panmictic unit for F. serratus was between 0.5 and 2 km (Coyer et al, 2003).…”

Dynamics of species interaction strength in space, time and with developmental stage

“…experimentally seeded germlings from natural settlement following deployment at field sites [40]. Zygotes were seeded at a relatively uniform density onto tiles, half of which had live barnacles established, the other half from which barnacles were removed prior to seeding.…”

Fronts, jumps and secondary introductions suggested as different invasion patterns in marine species, with an increase in spread rates over time

“…Furthermore, macrophytes have dispersal patterns that could obscure the means of range expansion. While reproductive stages are typically thought to have relatively short dispersal distances (less than 100 m, Dudgeon et al 2001), the restricted dispersal of juvenile stages can be augmented by drifting clumps of adult seaweeds; potentially over long distances (Santelices 1990;Ingolfsson 1995;Thiel 2003). The adult drifting stage is more significant if algal fragments can regenerate and re-attach to a substratum (Rodriguez 1996;ColladoVides 2001;Khou et al 2007;Fonck et al 2008).…”