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South indian garden plants, iit chennai
Plants have evolved to find their optimal environments. Well-watered drylands are the ancestral environments of many plants. Intense agriculture has exacerbated conditions in many parts of the world, with serious consequences for plant diversity. In the tropics, a loss of one species may trigger the collapse of an entire food web. According to the Intergovernmental Panel on Climate Change, about 75 % of the plant species currently found on earth may be lost by the year 2050, with serious effects on biodiversity, ecosystem functioning and human well-being. Recent studies have shown that climate change is already negatively impacting plant diversity and productivity. This makes understanding plant evolutionary adaptations to future climatic change an increasingly important focus. Two examples are given here: First, the performance of cultivars of wheat and barley, that are released regularly for crop improvement, when grown in conditions predicted for the future climate. Second, evolution experiments with guppies, a model species for evolutionary biology, which were set up to evaluate the effects of future climatic conditions on reproductive success. The experiments are summarized in Table 1. Table 1. Key parameters and findings from the two evolutionary experiments. Ferar et al. (2015) Experiment Design Background: Local adaptation to local conditions is a major driver of evolution and speciation. While the average rate of adaptation is between 1-2% per generation, local adaptation is relatively slow. To speed up the process, we have to breed plants that are highly adapted to their local conditions. Selection pressures have to be imposed in controlled environments, and the resulting selected plants then released into the wild and undergo natural selection. Current biotechnological approaches for crop improvement are limited to manipulating individual parts of a plant that result in only marginal improvements. Molecular breeding through recombination between highly related plants creates a new genotype that overcomes the limitations of the cultivar to be improved. It also provides insights into the genetic architecture of fitness components that might be manipulated by breeding or selection in subsequent generations. The key concept is the inherent linkage disequilibrium (LD), i.e., nonrandom association of alleles at two or more loci, and the probability that a random mutation at one of these loci will carry with it an un-random association with the mutation at the second locus. Extensive LD between loci is indicative of highly related genotypes. We use LD as a proxy for "the fitter genotype that is selected against by natural selection”. Methodology and Setup: The common ancestor of any two wheat cultivars is from the Middle East, where local adaptation probably occurred thousands of years ago. The annual cycle of wheat is composed of two phases: the vegetative phase, during which the plant develops the stem, leaves, roots and reproductive organs, and the reproductive phase, during which wheat inflorescences and fruits are produced. The interaction between these two phases can be modified by several factors, including time of day and duration of exposure to solar radiation, water availability, nitrogen fertilization and altitude. In our experiments, the factors were limited to light and water supply, nitrogen fertilization and altitude. Two factors were changed from one generation to the next: the light regime and the nitrogen fertilization. The light regime was changed from 12 hours light and 12 hours dark (12-12) to 16 hours light and 8 hours dark (16-8) because of the diurnal light-dark cycles of the two light regimes, and no nitrogen fertilization was applied at night during the 16-8 regime because of the lowered nutrient needs at night. Nitrogen fertilization was applied at night during the 12-12 regime. Plants were grown in small pots in an array of 96 microcosms in a greenhouse with an ambient light (70 lux) and temperature cycle of