Size does matter, but not only size: Two alternative dispersal strategies for viviparous mangrove propagules

作者：De Ryck Dennis J R^*; Robert Elisabeth M R; Schmitz Nele; Van der Stocken Tom; Di Nitto Diana; Dahdouh Guebas Farid; Koedam Nico

来源：Aquatic Botany, 2012, 103: 66-73.

DOI：10.1016/j.aquabot.2012.06.005

• Ceriops tagal
• Rhizophora mucronata
• Long-distance dispersal
• Hydrochory
• Predation
• Propagule density
• Propagule size
• Tracking
• Vivipary
• Root-growth

We studied the propagules of two widespread mangrove species, Ceriops toga! and Rhizophora mucronata, that are similar in shape but differ in other morpho-anatomical features (average length is 23.1 +/- 2.2 cm and 44.4 +/- 4.3 cm, resp., n = 180). We hypothesized the propagules of both species to have a different hydrodynamic behavior and establishing capacity, resulting in a different dispersal strategy. More specifically, we hypothesized that C. tagal propagules have a larger dispersal capacity than those of R. mucronata. The dispersal strategies of C. tagal and R. mucronata propagules were elucidated through a combination of a propagule tracking (n = 180 per species), predation (n = 20 per species) and root-growth experiment (n = 120 per species), carried out in the field. C. toga! and R. mucronata adopted two different dispersal strategies. C. tagal releases a large number of propagules and disperses fast, having a slender morphology and low density (average p: 985.29 +/- 19.02 g L-1), as well as a high agility (smaller size) when dispersing through dense root systems. C. tagal propagules have a theoretical advantage to disperse over longer distances over the thicker, longer and denser R. mucronata propagules (average p: 1003.92 +/- 8.52 g L-1; t = 8.90, p %26lt; 0.0001, n = 197). C. tagal have, however, lower establishment chances due to slower root-growth, desiccation sensitivity and smaller size. In contrast to Ceriops%26apos; tactic of releasing high numbers of propagules and fast dispersal, R. mucronata has adopted a dispersal tactic of survival. Fewer propagules are released, but they are more resistant to predators due to their larger size and they can anchor themselves faster due to quicker root-growth (Mann-Whitney U: p %26lt; 0.0001, n(Ct) = 59, n(Rm) = 57). Overall, propagule characteristics of both species result in different and alternative dispersal strategies on a local scale, contradicting our initial hypothesis. On a global scale, we hypothesize this might lead to a similar capacity for long-distance dispersal, ending in successful establishment.

• 出版日期2012-10