Ecophenotypic variation  Ecophenotypic variation ("ecophenotype") refers to phenotypical variation as a function of life station. In wide-ranging species, the contributions of heredity and environment are not always certain, but their interplay can sometimes be determined by experiment. Plants display the most obvious examples of ecophenotypic variation. One example are trees growing in the woods developing long straight trunks, with branching crowns high in the canopy, while the same species growing alone in the open develops a spreading form, branching much lower to the ground. Genotypes often have much flexibility in the modification and expression of phenotypes; in many organisms these phenotypes are very different under varying environmental conditions. The plant "Hieracium umbellatum" is found growing in two different habitats in Sweden. One habitat is rocky sea-side cliffs, where the plants are bushy with broad leaves and expanded inflorescences; the other is among sand dunes where the plants grow prostrate with narrow leaves and compact inflorescences. These habitats alternate along the coast of Sweden and the habitat that the seeds of "H. umbellatum" land in determines the phenotype that grows. Invasive plants such as the honeysuckle can thrive by altering their morphology in response to changes in the environment, which gives them a competitive advantage. Another example of a plants phenotypic reaction and adaptation with its environment is how Thlaspi caerulescens can absorb the metals in the soil to use to its advantage in defending against harmful microbes and bacteria in its leaves. The more immediate responses shown by vascular plants to their environment, for instance a vine's ability to conform to the wall or tree upon which it grows, are not usually considered ecophenotypic, even though the mechanisms may be related. Since animals are far less plastic than plants, ecophenotypic variation is noteworthy. When encountered, it can cause confusion in identification if it is not anticipated. The most obvious examples are again common observations, as the dwarfing of aquarium fish living in a restricted environment. In asexual reproduction, the parent passes on the entire genome to the next generation. Mutations to the genes are the only source of genetic variation. In sexual reproduction, each parent contributes half of his or her genome to the offspring; thus the offspring contain a mixture of genetic material. Adaptations are traits that increase fitness, the driving force for natural selection. The level of fitness associated with an allele can only be ascertained by comparison with alternate alleles.