Genetic Variation: Its role in adaptive phenotypic variation and its erosion in threatened species

Abstract

In a changing climate, rapid adaptation may be crucial for survival. Genetic diversity is the main source for evolutionary changes prevailing in populations. Intraspecific variation allows populations to adapt to environmental changes. Maintaining this variation is vital for biodiversity’s long-term conservation. Yet, genetic information is only incorporated in 17% of conservation plans in Europe (Pierson et al., 2016). Moreover, there is an ongoing decline in insect populations over the world. To make more assertive conservation plans and management it is necessary to acknowledge how the erosion of genetic diversity affects the population’s adaptive potential. In this study, we assessed if genetic diversity has been reduced due to habitat fragmentation after the 1950s by using whole-genome resequencing data to measure heterozygosity from historical and modern individuals of threatened butterfly species, Phengaris alcon, Phengaris arions, and Scolitantides orion. Genetic diversity, estimated as heterozygosity, was lower in the modern samples than in the historical samples for the threatened species. To investigate if a reduction in genetic diversity can affect the adaptive potential of a species, we also assessed if reduced genetic diversity in more isolated populations has phenotypic consequences in the habitat generalist Polyommatus icarus. We tested this by studying the variation in wing color, and the ability to respond adaptively through altered temperatures in a continuous and a more isolated population. While we found small differences in genetic diversity, the slightly lower genetic diversity in the more isolated population was not reflected in reduced phenotypic variation or ability to respond adaptively to a rise in temperature. This could potentially be due to the differences in genetic variation between the two population types being too small to result in phenotypic consequences or the plasticity being only weakly genetically determined. In conclusion, my findings suggest that the genetic diversity in rare butterfly species has been negatively affected by anthropogenic changes. Future studies addressing whether reductions in genetic diversity result in reduced evolutionary potential should use a larger span of levels in genetic diversity.

Popular Abstract

Have you ever wondered why are everyone and everything a little bit different? All the species look different from one another although some are more similar. Every living thing has a unique code on them called DNA and it is formed by genes. Genes tell our bodies how to function. This code has small differences between every individual which makes us look different or similar to others. This is called genetic diversity. Genetic diversity is very important because it gives the species a better possibility to survive. However, if the populations become small and isolated, genetic diversity can be lost, which will decrease the species’ possibilities of survival.

In the early 1900s, natural habitats were big and well connected, big populations of butterflies used to live and had high genetic diversity. When agriculture started an intensification around the 1950s, natural habitats were made smaller or lost, making the butterflies populations become smaller and isolated, and in consequence, having a lower genetic diversity. We looked into the DNA of three different species of butterflies (Phengaris alcon, Phengaris arion, and Solitantides orion), we used 3 individuals from a museum collection of the early 1900s and 3 individuals from a private collector of the early 2000s to investigate if these butterflies had lost genetic diversity. Our results showed that the modern individuals did, in fact, lose genetic diversity when comparing them to the old individuals.

We wanted to know if this loss of genetic diversity also occurred in isolated populations of the same species, for that we used another butterfly species, Polyommatus icarus also known as the common. blue, which is widespread across Sweden. We compared the DNA of a big and continuous population in southern Scania and one small and isolated population surrounded by forest in Småland. We also looked into the DNA of the individuals of both populations. We saw that the continuous population had higher genetic diversity than the isolated population as we expected.

Finally, the female butterflies of the common blue, have differences in the color of their wings. The colors can be used as signals, camouflage or to attract their partners. In this species, we don’t know what the reason for the color variation is, but we know it can vary depending on the temperatures of the environments they are born in. We made an experiment raising butterflies at two different temperatures, 18 and 26C until they became adults. We measured the amount of blue their wings had with the help of a program called Image J. We wanted to see if the population with less genetic variation had less differences in the variation of color on the wings. But we found that both populations of the common blue had no difference in how much their wings varied in color. Possibly because their differences in genetic diversity weren’t that big.

With this study, we can reinforce the importance of considering genetic diversity when we make plans to save populations of living beings. Our world is in constant change, climate change is affecting the natural habitats and the populations that live in them. We have to continue studying and looking for ways to conserve species and their genetic diversity.

• author: Torres Lara, Ana Sofia
• supervisor: Anna Runemark; Zachary Nolen; Magne Friberg
• organization: Degree Projects in Biology
• course: BION03 20211
• year: 2022
• type: H2 - Master's Degree (Two Years)
• subject: Biology and Life Sciences
• language: English
• id: 9103232
• date added to LUP: 2022-11-16 09:19:16
• date last changed: 2022-11-16 09:19:16