Phenotypic polymorphism (PP) is an organism’s ability to change its phenotype in response to changes in the environment. PP occurs when genes interact with environmental cues. Thus, the two cannot be separated. Many factors, both internal and external, can trigger PP. pathogen presence etc.) Externally (E.g. photoperiod etc.). Cues can be harmful stimuli that have no effect on individuals but cause adaptive plasticity. For example, photoperiod. But they also predict future environmental conditions. In contrast, toxins and other harmful agents are also considered stimuli. It has been proven that organisms with phenotypicplasticity are adaptive. All living creatures are subject to abiotic as well as biotic influences. Individuals can only adapt to changing environments by changing their phenotype. This phenomenon has been observed in various organisms. Insects have also been extensively studied. Butterflies in a variety of seasonal environments and with shorter generation times are also phenotypically flexible for different traits.
The temperate butterfly studies are comparatively more extensive than the tropical butterflies. Studies have shown most swallowtails possess a dimorphic trait of pupal coloration. (Green and Brown), but Danaus Chrysippus exhibits both pink and a green pupa. The environment in nature is different depending on the season. For example, in one season, there is a lot of greenery, such as grasses and leaves, while in another, it is much less. The color of the substrate is crucial for the immobile pupa’s survival. Green pupas can blend in well with green backgrounds and are undetectable by predators. Brown coloration, however, can be more advantageous if there is less greenery, or the substrate is not green. This color dimorphism, which is a seasonally changing heterogeneous backdrop, helps the pupae to survive this critical life stage. While there is considerable research on environmental variables affecting phenotypes and plasticity, it has yet to be explored. In my thesis, i will explore tropical butterfly color plasticity in relation to environmental factors including different pupation surfaces (grasses), and the genetics behind it.
Task One. Project 1: Genetic basis for the color plasticity of Mycalesis minus pupae
Overview: The environmental factors that affect the color of pupal are not all-encompassing. This phenomenon has been observed in many studies on different swallowtail butterflies, such as P. zelicaon and P. polyxenes. The color of the offspring that are produced from artificial selections is similar to that of their parents. Some studies indicated that pupal plasticity could be inherited. This model states that the ability of a pupa to be green or brown depends on a heritable phenotypic factor. A larva which is highly sensitive to green can be less affected when the environment cues that induce brown coloration are present. The intensity of the inducing stimulus is important, but it varies depending on the species and population because ecological conditions vary. Mycalesis minus, a tropical Nymphalidae monarch butterfly, has pupal color plasticity that is both green and a brown. In studies, it was found that under low relative humidity conditions, 20% of the pupae were brown and 80% were green. In conditions of high relative humidities (i.e. In laboratory experiments, it was also found that pupae of all colors can be formed under varying environmental conditions and substrates. Brown pupae, however, are only present in specific conditions. The number of pupae is low when RH is high and the only place they form are off leaf substrates. My question is: Is the “sensitivity” to produce a certain color heritable among Mycalesis minus butterflies?
Hypothesis 1 If “sensitivity” was heritable then certain lines of brown and green pupae would produce more green pupae in the following generations.
Hypothesis 2. Green pupae will produce more off-leaf green pupae over the next generations as compared with green pupae of leaf substrate. I am running a series of artificial-selection experiments. In order to test my “Hypothesis 1”, a chamber where the relative humidity has been set at 60% is used. This results in a high number of brown and green pupae. The green and brown pupae will then be separated. Adults born from brown or green pupae must be raised separately. Filtering will take place for each generation based on the pupal colour (green or a brown). The experiment will run for a minimum of ten generations. Work completed and work in progress: I began with 25 brown pupae for “Hypothesis 1”. I obtained 15 adults from the first generation (F0), but their larvae are extremely small. The next (F1) generations produced no brown pupae, only green ones. I have an abundance of eggs, so I would like to repeat the experiment on a much larger sample. In order to test “Hypothesis 2, I started my experiment by placing a single wandering larva in a round cage that was empty. In the first test, I placed six larvae inside identical round cages of the same height and shape. These cages then went into the 60% RH chamber. On the cage net, I saw 3 green pupae form and 3 other larvae were dead. I’m testing it again on a large scale.
Task 2. Effect of host plant differences on pupal colour plasticity. It has been demonstrated that the color, texture, smoothness and structure of the pupation substrate affects pupal colour plasticity. Mycalesis minus pupal colors polymorphism has been studied in the past on maize plants. Since maize does not grow in a wild state where they can pupate, I am looking for patterns of pupation substrates for grasses that are commonly found. Some local grasses can be identified by the flower seed morphology. (Examples- Eleusine sp. Ragi or Wheat can also be compared. Some of the grasses have a horizontal growth pattern, while others grow vertically. The stems and leaves of the grasses vary in many aspects, including shape, texture, smoothness. As the soil is a different color than the leaves or stems, the distance between the soil and the substrates for pupation may have an effect on coloration. According to my hypothesis, grasses growing close to ground (horizontally) will produce more brown larvae than grasses growing vertically. Work in Progress and Work Done: Identifications of wild grasses have been made. I am currently trying to grow these grasses under laboratory conditions.
My future goal is to… Artificial selection experiment to determine pupal color dimorphism in Danus chryssippus. 2. You can find out the evolutionary history of pupal pigmentation by examining the butterfly tree. Currently, a literature review is being conducted on the butterfly pupal colour plasticity. First semester course work: I’ve completed two classes (BIO4202and BIO4207). The 1st Semester SGPA is 8.