Under stress conditions, the organisms begin to a lesser extent to suffer the consequences of competition with other species.
According to Darwin, under adverse environmental conditions — in deserts, permafrost zones and salt marshes — a leading role in limiting the growth and reproduction of plants and animals play temperature and other climatic factors. However, when these factors close to their optimum, at the forefront are the relationships between the organisms. Darwin believed that, in the case of plants this is due to the increase of species diversity and density of their growth.
The researchers studied the population dynamics of the hibiscus Hibiscus meyeri on three field sites located in Central Kenya (Africa) with various humidity for four years. In accordance with the predictions of Darwin, the pollination by insects, eating herbivores and competition with other herbs and shrubs played an important role in the delimitation of the area of hibiscus in moist areas. But on dry territories the same factors to a lesser extent influenced the distribution of plants.
According to scientists, the density of vegetation and species diversity is simply not important for the distribution of hibiscus, growing in adverse climatic conditions. These factors may remain at the same level in different areas, but the low humidity is at the forefront, limiting the growth, survival and reproduction.
In the modern theory of evolution, taking into account genetics and embryology, Darwin’s ideas about the leading role of the struggle for survival and natural selection were reconsidered, although still in its basis. So, in 1960, was developed the neutral theory of evolution, according to which in small populations natural selection does not take place, and new features arise as a result of random, not having use of mutations.
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