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Population Establishment (population + establishment)
Selected AbstractsPopulation consequences of maternal effects: sex-bias in egg-laying order facilitates divergence in sexual dimorphism between bird populationsJOURNAL OF EVOLUTIONARY BIOLOGY, Issue 6 2002A. V. Badyaev Abstract When costs and benefits of raising sons and daughters differ between environments, parents may be selected to modify their investment into male and female offspring. In two recently colonized environments, breeding female house finches (Carpodacus mexicanus) modified the sex and growth of their offspring in relation to the order in which eggs were laid in a clutch. Here we show that, in both populations, these maternal effects strongly biased frequency distribution of tarsus size of fully grown males and females and ultimately produced population divergence in this trait. Although in each population, male and female offspring show a wide range of growth patterns, maternal modifications of sex-ratio in relation to egg-laying order resulted in under-representation of the morphologies that were selected against and over-representation of morphologies that were favoured by the local selection on juveniles. The result of these maternal adjustments was fast phenotypic change in sexual size dimorphism within and between populations. Maternal manipulations of offspring morphologies may be especially important at the initial stages of population establishment in the novel environments and may have facilitated recent colonization of much of North America by the house finch. [source] Acer negundo invasion along a successional gradient: early direct facilitation by native pioneers and late indirect facilitation by conspecificsNEW PHYTOLOGIST, Issue 3 2010Patrick Saccone Summary ,Here, we analysed the role of direct and indirect plant interactions in the invasion process of Acer negundo along a natural successional gradient in the Middle Rhone floodplain (France). We addressed two questions: What are the responses of the invasive Acer seedlings to native communities' effects along the successional gradient? What are the effects of the invasive Acer adult trees on the native communities? ,In the three communities (Salix, Acer and Fraxinus stands) we transplanted juveniles of the invasive and juveniles of the natives within the forest and in experimental gaps, and with and without the herb layer. We also quantified changes in understory functional composition, light, nitrogen and moisture among treatments. ,Acer seedlings were directly facilitated for survival in the Salix and Acer communities and indirectly facilitated for growth by adult Acer through the reduction of the abundance of highly competitive herbaceous competitors. ,We conclude that direct facilitation by the tree canopy of the native pioneer Salix is very likely the main biotic process that induced colonization of the invasive Acer in the floodplain and that indirect facilitation by adult conspecifics contributed to population establishment. [source] Reproductive assurance through self-fertilization does not vary with population size in the alien invasive plant Datura stramoniumOIKOS, Issue 8 2007Mark van Kleunen Autonomous self-fertilization is suggested to be associated with invasiveness in plants because it offers reproductive assurance when there is a shortage of suitable mates or pollinators. Given that shortages of mates and pollinators are a common cause of Allee effects in small plant populations, we predict that the benefits of self-fertilization in terms of reproductive assurance should be greatest in small populations. We tested this idea for the invasive herb Datura stramonium, a self-fertilizing species which is also cross-pollinated to some extent by insects (mainly hawkmoths and honeybees). During two consecutive years, we studied 20 and 55 populations, respectively, of different sizes. Untreated flowers of D. stramonium showed high levels of fruit and seed set in all populations studied. Although, fruit and seed set were generally reduced by about 90% in flowers in which self-fertilization was prevented through emasculation, this effect did not vary according to population size. By using a natural color (anthocyanin) dimorphism in 12 populations, we showed that the average outcrossing rate was low (1.3%) and that there was no relationship between outcrossing rate and population size. Pollen removal from flowers also did not vary according to population size, suggesting that the pollinator visitation rate is not lower in small populations. However, decreasing deviations of observed from expected fruit set with population size imply that small populations may have an increased chance of extinction due to demographic stochasticity. Overall, our results suggest that reproductive assurance through self-fertilization in invasive plants may be important for all stages of population establishment, and not just in the founder population. [source] Allozyme diversity and history of distribution expansion in the maritime perennial plant Hedyotis strigulosa (Rubiaceae), distributed over the wide latitudes in the Japanese ArchipelagoBIOLOGICAL JOURNAL OF THE LINNEAN SOCIETY, Issue 4 2008MASAYUKI MAKI Allozyme diversity was examined in 30 populations of the maritime perennial plant Hedyotis strigulosa var. parviflora, which is distributed from subtropical islands to the central mainland of Japan. Genetic diversity within populations tended to be larger in southern island populations than in northern mainland populations. In the southern part of the distribution, the population size is generally large and populations are distributed more continuously than in the northern area, resulting in the larger effective size of southern populations as a whole. These factors play a major role in maintaining greater genetic diversity in the southern populations. By contrast, genetic diversity in the northern populations is very low, probably resulting from bottlenecks of population establishments during recolonization from refugial area to the northern areas. Geographically close populations were located near each other in the multidimensional scaling and the phenogram based on genetic distances, suggesting that gene flow among remote populations is rather limited. The pattern of genetic diversity in H. strigulosa var. parviflora is likely caused by the distribution expansion of the species; in the last glacier era, the species was restricted to the southern area; its advance to the northern area is relatively recent. Another variety endemic only to the Daito Islands, H. strigulosa var. luxurians, has lower genetic diversity than H. strigulosa var. parviflora and has genetically diverged from H. strigulosa var. parviflora. © 2008 The Linnean Society of London, Biological Journal of the Linnean Society, 2008, 93, 679,688. [source] | ||||||||||