Kaufman Sylvan R, Smouse Peter E
Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, MA, 02138, USA.
Department of Ecology, Evolution & Natural Resources, Rutgers, The State University of New Jersey, 08901, New Brunswick, NJ, USA.
Oecologia. 2001 May;127(4):487-494. doi: 10.1007/s004420000621. Epub 2001 May 1.
Melaleuca quinquenervia is a wetland tree species indigenous to eastern Australia. It was separately introduced to east and west Florida as an ornamental, but has since become invasive, dominating several habitat types. We tested the predictions that (1) Australian populations would exhibit more genetic variation than Florida populations, due to founder effect, and (2) high phenotypic plasticity would be found in all populations, due to the wide range of habitats occupied. We compared the phenotypic plasticity and familial variation among three Australian populations, two east Florida, and two west Florida populations in a greenhouse experiment. We grew seedlings collected from different maternal trees in each population under two water levels and three pH levels, reflecting the natural range of water levels and soil pH in Florida and Australian Melaleuca stands. We measured leaf size and shape, growth rate and above-ground biomass of seedlings and determined the components of phenotypic variance (familial, environmental, and their interaction) using univariate and multivariate analysis of variance. All traits showed significant among-population and among-family variation, as well as significant phenotypic plasticity, in response to both water level and pH level changes. Sensitivity to pH was particularly high, presumably because plants were grown under pHs ranging from 4.7 to 7.4, and because pH can influence nutrient availability. Familial variation contains genetic variation, but it may also be confounded with maternal environmental effects. Comparing Australian to Floridian Melaleuca, amounts of familial variation and phenotypic plasticity varied by trait. Overall, Australian Melaleuca had more among-population variation than Floridian Melaleuca, presumably reflecting the wider latitudinal range and longer time for evolutionary change in Australia, but had similar amounts of among-family variation, within any one population. If maternal effects are strong, among-population differences may merely reflect greater environmental differences among Australian sites than Florida sites. Australian Melaleuca had less phenotypic plasticity, possibly due to founder effects in Florida or to subsequent adaptive evolution of phenotypic plasticity in Floridian populations. Floridian Melaleuca shows little loss of familial variation, compared to indigenous Australian populations, and that, in combination with its high phenotypic plasticity, should allow it to continue to colonize new areas successfully.
千层金是一种原产于澳大利亚东部的湿地树种。它曾作为观赏植物分别被引入佛罗里达州东部和西部，但后来成为入侵物种，在多种栖息地类型中占据主导地位。我们检验了以下预测：（1）由于奠基者效应，澳大利亚种群将比佛罗里达种群表现出更多的遗传变异；（2）由于所占据的栖息地范围广泛，所有种群都将表现出较高的表型可塑性。在一项温室实验中，我们比较了三个澳大利亚种群、两个佛罗里达州东部种群和两个佛罗里达州西部种群之间的表型可塑性和家系变异。我们在两种水位和三种pH值水平下培育从每个种群不同母树上采集的幼苗，这反映了佛罗里达州和澳大利亚千层金林分中水位和土壤pH值的自然范围。我们测量了幼苗的叶片大小和形状、生长速率和地上生物量，并使用单变量和多变量方差分析确定了表型方差的组成部分（家系、环境及其相互作用）。所有性状在种群间和家系间均表现出显著变异，并且对水位和pH值变化均表现出显著的表型可塑性。对pH值的敏感性特别高，可能是因为植物是在pH值范围为4.7至7.4的条件下生长，并且因为pH值会影响养分有效性。家系变异包含遗传变异，但也可能与母本环境效应混淆。比较澳大利亚和佛罗里达的千层金，家系变异量和表型可塑性因性状而异。总体而言，澳大利亚千层金的种群间变异比佛罗里达千层金更多，这可能反映了澳大利亚更广泛的纬度范围和更长的进化变化时间，但在任何一个种群内，家系间变异量相似。如果母本效应很强，种群间差异可能仅仅反映了澳大利亚地区之间的环境差异比佛罗里达地区更大。澳大利亚千层金的表型可塑性较小，可能是由于佛罗里达州的奠基者效应或佛罗里达种群随后表型可塑性的适应性进化。与澳大利亚本土种群相比，佛罗里达千层金的家系变异损失较小，并且这与其高表型可塑性相结合，应该使其能够继续成功地开拓新区域。
