Predation due to sexual selection results in modified traits in males.

 

    An experiment showing the process of natural selection has shown that certain traits will diminish through predation. Broad-horned flour beetles are eaten by Assassin bugs, which target the larger beetles for maximum nutrition. Because of this, scientists found that predation of the beetles resulted in lower fitness for males and much greater fitness and reproductive success for females. Additionally, males that survived would have smaller bodies and mouthparts, resulting in more generations of smaller males. In this way, scientists found that sexual dimorphism diminished in more severe environments, supporting that natural selection directly resulted in the dimorphisms seen in the wild types.

This is less directly genetic, but it is interesting to note how the fitness of the species under certain conditions can influence the genetic variations and phenotypes expressed. This is a study that propels the understanding of natural selection forward (despite this actually being an artificial selection event).

Researchers Found the Genes Responsible for Changing Ground Beetle Genitalia

Japan's Carabus male beetles mate with females by inserting their chitin-covered appendage. Two pieces of the appendage break off: a sperm delivery tube and a copulatory piece. Researchers identified several genes that control the size of the male beetle's "piece" and the female beetle's pocket. Initial hypotheses demonstrated that the male and female's genes for genitals should be connected through coevolution which should show in their genome. In other words, the size and shapes of genitalia in species should be analogous because the same genes influence male and female dimorphism. However, researchers found that there is much genetic diversity between the genes that determine these beetle's genitalia sizes. The discovery is a significant case in speciation because it contributes to an old speciation model called the "Lock-and-Key Hypothesis".

The Lock-and-Key Hypothesis is a method of reproductive isolation, specifically mechanical isolation which separates a species from mating. For example, the beetles described in the article have such a large genetic diversity contributing to genitalia that some of the male appendages do not fit into females. The article states, "Out-of-sync sizes can cause ruptures, snap-offs and generally low numbers of offspring." Talk about painful! These beetles are now contributing to hybridization which can eventually evolve into a whole other species altogether. Genetic hybrids tend to be infertile, but researchers found that the hybrids of two different beetle species in Japan can produce offspring.





It is truly interesting to see evolution in motion especially with the Lock-and-Key Hypothesis. It's no secret that genitalia in male species may not fit into a female in either the same species or another. The Lock-and-Key Hypothesis was proposed over a hundred years ago, but it's often overlooked because other reproductive isolations such as gametic isolation or chromosomal differences are better modes of preventing hybridization. The discovery here is fascinating because genetic diversity actually prevented some of these beetles from mating within their own species.

Sources:
https://www.sciencenews.org/article/ground-beetle-genitals-genetics-evolution-battle-sexes
https://advances.sciencemag.org/content/5/6/eaav9939

Genetic Modifications Cause Beetle Wings to Appear on their Abdomen

The New York Times highlights an article published in the Proceedings of the National Academy of Science on how beetles can have genetically modified wings. Dr. Tomoyasu, an evolutionary biologist at the University of Miami, and David Linz have altered the common beetle to have more than two sets of wings on their back. These wings have been genetically engineered to be housed on their abdomen while the beetle is in the larva stage. Since there is a lack of fossil evidence, its hard to tell exactly when insects first took flight (estimated to be approximately 300 million years ago). Some scientists think that insect wings were formed by the fusion of two tissues. The “dual origin” hypothesis of 1974 states that the wings of insects formed when the dorsal body wall and the leg segments fused together. There is some evidence to prove this since some insects have lost the capability of their legs since they have ascended into the body, and some have had them located to their head, which created the antennas. Master switches in the beetle’s genome were manipulated which let the scientists alter which area of the body would have wing growth, however this also altered anatomical structures to the beetle that did not relate to flight at all. GFP (green fluorescent protein) was also introduced to the beetle to mark where the expressions of certain genes were relating to flight.

This article was a good read. Since working with GFP in the lab it is interesting to see the protein being used on a much larger scale level and how it can be used for genetic manipulation in the laboratory setting.

(Related Article)

The Importance of Beetles with Three Eyes to Genetics

Beetles with three eyes have the potential to further our current knowledge on genetic development and have in recent studies. Recently in Eurekalert, a press release identified that new traits had evolved through specific genes. The researchers turned off the orthodenticle genes specifically, and ended up with some fascinating results. The beetles head structure had evolved and there was either complete loss of, or the shrinkage of, their horns. In addition to this, the beetles had developed compound eyes in the middle of their heads. The same type of changes were made with another species of beetles and they did not yield the same results.

This was amazing to researches because now they could turn off the development of one major region of the head, and turn on the development of another. The researchers feel that orthodenticle genes have developed a new function which is now to instruct the development of horn and head configuration. They figured this out by mapping the regions of larval heads that would later make up the fully-matured, adult heads. They turned genes on and off to distinguish the multiple roles they have in head development. Overall, the study of beetles in relation to genetics remains to be an exciting and interesting area of study.

I find this to be incredibly compelling because if we have the potential to remove genes from a certain area and enhance or turn on the ability of others within beetles, then we probably have the capability of doing the same in humans. This could mean that we might be able to eliminate undesirable traits, or illnesses in the future and potentially offset a more positively inclined gene in return. 

Crop Pests Stopped by Plants That Cripple Attackers' RNA

Invasive species are known to be the cause of many devastating agricultural failures throughout history. One insect in particular, dubbed the "international super pest", is the Colorado potato beetle (pictured above). This beetle eats different crops all across the world, and costs the agricultural industry billions of dollars per year. The worst thing about this beetle is that it is resistant to practically every insecticide and has very few predators. The good news is scientists have finally come up with a way to protect crops from this pest.

A team of researches in Germany are using RNAi (RNA interference) to kill-off this beetle. First, the scientists found a gene that is essential to the insect; this gene codes for a "cytoskeleton protein vital to maintaining a cell's shape." Then, plants were engineered to produce a special type of RNA. When the beetle eats this plant, the plant's RNA interferes with the beetles'. In turn, the insects ribosomes are unable to read the mRNA (or messenger RNA), and code for the essential protein previously mentioned. Without that, the insect dies. 

The idea to use RNAi has been around for about a decade, however, it was unsuccessful in killing all the pests when tested years ago. This time, scientists modified the technique by inserting the plant's "instructions" for the unique RNA into their chloroplasts instead of the nucleus, which proved to work much more efficiently. This new mechanism can possibly help put a stop to crop devastation by pests in the future. The question still remaining is will the pests develop resistance to the RNAi like they have insecticides? 

I liked this article because it has brought a possible scientific solution to insects destroying crops around the world. Farmers try everything to protect their crops from being attacked by pests, but many times it makes the problem worse. For example, when an invasive insect is introduced to a crop, one possible solution is to bring a predator of that insect to the crop, too. This strategy can go very bad, very fast. If this new technique works, it could be revolutionary for farmers and consumers everywhere. 

Original Article

Related Article

Beetle defence may save lives

New antibiotic and anti-cancer chemicals may one day be synthesized using biotechnology, following CSIRO’s discovery of the three genes that combine to provide soldier beetles with their potent predator defence system. The three genes that combine to make the fatty acid soldier beetles use to ward off predators has been replicated. Because of its anti-microbial properties, the substance may be synthesised to develop antibiotics and anti-cancer chemicals for human consumption. The team found this fluid contains an exotic fatty acid called dihydromatricaria acid, or DHMA, which is one of a group called polyynes that have known anti-microbial and anti-cancer properties. While DHMA and similar polyne fatty acids are found in a wide variety of plants, fungi, liverworts, mosses, marine sponges and algae, these compounds have proved very difficult to manufacture using conventional chemical processes. However, Dr Haritos and her team have developed a way to achieve this.

Soldier beetles are the only animals reported to contain DHMA. This, together with the observation that  the beetles forage on plants (such as daisies) which contain a lot of these types of fatty acids, led to previous incorrect conclusions that the DHMA in soldier beetles was derived from their diet. "Through our research and the gene differences we have discovered, we now know soldier beetles have evolved this same defensive compound entirely independently of its production in plants and fungi," Dr Haritos said.