Kordas Rebecca L, Dudgeon Steve
Department of Biology, California State University, Northridge, CA, 91330-8303, USA.
Oecologia. 2009 Jan;158(4):717-31. doi: 10.1007/s00442-008-1183-y. Epub 2008 Oct 31.
The strength by which species interact can vary throughout their ontogeny, as environments vary in space and time, and with the density of their populations. Characterizing strengths of interaction in situ for even a small number of species is logistically difficult and may apply only to those conditions under which the estimates were derived. We sought to combine data from field experiments estimating interaction strength of life stages of the barnacle, Semibalanus balanoides, on germlings of Ascophyllum nodosum, with a model that explored the consequences of variability at per capita and per population levels to the abundance of year-old algal recruits. We further simulated how this interaction affected fucoid germling abundance as the timing of their respective settlements varied relative to one another, as occurs regionally across the Gulf of Maine, USA. Juvenile S. balanoides have a weak estimated per capita effect on germlings. Germling populations are sensitive to variation in per capita effects of juvenile barnacles because of the typically large population sizes of the latter. However, high mortality of juvenile barnacles weakens the population interaction strength over time. Adult barnacles probably weakly facilitate fucoid germlings, but greater survival of adults sustains the strength of that interaction at the population level. Germling abundance is positively associated with densities of adult barnacles and negatively associated with that of juvenile barnacles. Metamorphosing cyprid larvae have the strongest per capita effect on germling abundance, but the interaction between the two stages is so short-lived that germling abundance is altered little. Variation in the timing of barnacle and A. nodosum settlement relative to one another had very little influence on the abundance of yearling germlings. Interactions between barnacles and germlings may influence the demographic structure of A. nodosum populations and the persistence of fucoid-dominated communities on sheltered rocky shores in New England.
由于环境在空间和时间上存在差异，且物种种群密度也有所不同，物种间相互作用的强度在其个体发育过程中可能会发生变化。即使对于少数物种，在原位表征相互作用强度在逻辑上也很困难，而且可能仅适用于得出估计值的那些条件。我们试图将来自实地实验的数据与一个模型相结合，该实地实验估计了藤壶（Semibalanus balanoides）各生命阶段对泡叶藻（Ascophyllum nodosum）幼体的相互作用强度，该模型探讨了人均水平和种群水平的变异性对一岁龄藻类新苗丰度的影响。我们进一步模拟了随着藤壶和泡叶藻各自附着时间相对于彼此的变化，这种相互作用如何影响岩藻幼体的丰度，美国缅因湾各地均会出现这种区域差异。估计幼年藤壶对幼体的人均影响较弱。幼体种群对幼年藤壶人均影响的变化很敏感，因为幼年藤壶的种群规模通常很大。然而，幼年藤壶的高死亡率会随着时间的推移削弱种群间的相互作用强度。成年藤壶可能对岩藻幼体有微弱的促进作用，但成年藤壶更高的存活率维持了种群水平上这种相互作用的强度。幼体丰度与成年藤壶的密度呈正相关，与幼年藤壶的密度呈负相关。变态期的金星幼虫对幼体丰度的人均影响最强，但这两个阶段之间的相互作用持续时间很短，因此幼体丰度几乎没有变化。藤壶和泡叶藻附着时间相对于彼此的变化对一岁龄幼体的丰度影响很小。藤壶和幼体之间的相互作用可能会影响泡叶藻种群的人口结构以及新英格兰受庇护岩石海岸上以岩藻为主的群落的持久性。
