Hexbyte Glen Cove Male Y chromosome facilitates the evolution of sex differences in body size thumbnail

Hexbyte Glen Cove Male Y chromosome facilitates the evolution of sex differences in body size

Hexbyte Glen Cove

Credit: Pixabay/CC0 Public Domain

Females and males differ in many ways and yet they share the same genome. The only exception is the male Y chromosome. Using beetles as a study system, new research from Uppsala University, now published in Nature Ecology & Evolution, shows that despite the Y chromosome containing very few genes, it can dramatically change male body size and thus facilitate the evolution of sex differences.

Females and males typically differ in many ways in their morphology, physiology and behavior. How such sex differences, known as sexual dimorphism, evolve is a puzzle because females and males share the same set of genes and an in one sex should cause a correlated change even in the other sex, thereby preventing sex differences from evolving. The new study shows that even small amounts of genetic differences between the sexes can facilitate the evolution of sexual dimorphism such that it can evolve in just a few generations.

“Our experiments show that the autosomes as well as both sex chromosomes, the X and Y, can harbor important for sexual dimorphism, but the Y chromosome alone can alter the sex difference in size by as much as 30 percent. This is remarkable because in these beetles the Y chromosome contains just a handful of genes and represents a very small fraction of the genome, just like in humans. Many have thought that the Y only affects the most important reproductive processes in males, namely sperm production. Our findings suggest that the Y chromosome may have a broader role than previously appreciated,” says Philipp Kaufmann, a Ph.D. student at the Uppsala University’s Department of Ecology and Genetics and the first author of the study.

The evolution of sexual dimorphism is however not only dependent on where in the genome genetic variation resides, but also on how natural and can act on it. With the help of lab evolution, the research team showed that sexual size dimorphism could evolve when selecting on male size, but that when selection acted only on females, the shared part of the genome caused a correlated evolutionary response in males preventing dimorphism from evolving.

“The most drastic change in sexual dimorphism, an increase by 50 percent in only ten generations, occurred when we applied selection sexually antagonistically—favoring the opposite body size in the two sexes. This shows that under right kind of selection sex differences can clearly evolve rapidly, perhaps more easily than was previously thought,” says Elina Immonen, Assistant Professor at the Department of Ecology and Genetics, Uppsala University, and the principle investigator of the study.

“Combining information of what kind of genetic variation is available to selection with different forms of selection is a powerful way to test the determinants of evolution of sex differences. By isolating the effect of Y chromosome variation from the rest of the genome, we could directly demonstrate how large the effect of the Y chromosome is, something we didn’t expect to see when we started the work and this has helped understand how has evolved in this species. Future work will tell us more regarding how the Y chromosome can have such a large effect on males and how general its role is in the evolution of sex differences across taxa,” Immonen concludes.

More about the experiments

In their study, the researchers characterized the genetic architecture of body size in males and females by creating a large pedigree of over 8,000 beetles (the seed beetle Callosobruchus maculatus). This multi-generational family tree was used to quantify autosomal and sex chromosome linked genetic variation in body size. The use of artificial selection allowed testing how different forms of selection affect the of size dimorphism and included selection acting only on , only on females, or acting sexually antagonistically (in the opposite directions) in the two sexes. After ten generations of selection, the sexual size dimorphism was compared between the selection lines and the ancestral pedigree population. These two experiments clearly indicated that the Y chromosome play an important role in determining male response to . In order to test further the effect of the Y linked variation in isolation from variation in the rest of the genome, the research team carried out a third experiment. They isolated the effect of the Y chromosome on sexual size in these beetles by introducing the different Y into a genetically identical background. In other words, creating beetles that are identical twins to each other except for the Y chromosome.

More information:
Philipp Kaufmann et al, Rapid evolution of sexual size dimorphism facilitated by Y-linked genetic variance, Nature Ecology & Evolution (2021). DOI: 10.1038/s41559-021-01530-z

Male Y chromosome fac

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Hexbyte Glen Cove Big data-derived tool facilitates closer monitoring of recovery from natural disasters thumbnail

Hexbyte Glen Cove Big data-derived tool facilitates closer monitoring of recovery from natural disasters

Hexbyte Glen Cove

Credit: CC0 Public Domain

By analyzing peoples’ visitation patterns to essential establishments like pharmacies, religious centers and grocery stores during Hurricane Harvey, researchers at Texas A&M University have developed a framework to assess the recovery of communities after natural disasters in near real time. They said the information gleaned from their analysis would help federal agencies allocate resources equitably among communities ailing from a disaster.

“Neighboring communities can be impacted very differently after a natural catastrophic event,” said Dr. Ali Mostafavi, associate professor in the Zachry Department of Civil and Environmental Engineering and director of the Urban Resilience.AI Lab. “And so, we need to identify which areas can recover faster than others and which areas are impacted more than others so that we can allocate more resources to areas that need them more.”

The researchers have reported their findings in the Journal of The Royal Society Interface.

The metric that is conventionally used to quantify how communities bounce back from nature-caused setbacks is called resilience and is defined as the ability of a community to return to its pre-disaster state. And so, to measure resilience, factors like the accessibility and distribution of resources, connection between residents within a community and the level of community preparedness for an unforeseen disaster are critical.

The standard way of obtaining data needed to estimate resilience is through surveys. The questions considered, among many others, are how and to what extent businesses or households were affected by the natural disaster and the stage of recovery. However, Mostafavi said these survey-based methods, although extremely useful, take a long time to conduct, with the results of the survey becoming available many months after the disaster.

“For allocating funds, recovery information is actually needed in a faster and more near real-time fashion for communities that are trailing in the recovery process,” said Mostafavi. “The solution, we thought, was to look for emerging sources of data other than surveys that could provide more granular insights into community recovery at a scale not previously investigated.”

Mostafavi and his collaborators turned to community-level , particularly the information collected by companies that keep track of visits to locations within a perimeter from anonymized cell phone data. In particular, the researchers partnered with a company called SafeGraph to obtain location data for the people in Harris County, Texas, around the time of Hurricane Harvey. As a first step, they determined “points of interest” corresponding to the locations of establishments, like hospitals, gas stations and stores, that might experience a change in visitor traffic due to the hurricane.

Next, the researchers mined the big data and obtained the number of visits to each point of interest before and during the hurricane. For different communities in Harris County, they calculated the time taken for the visits to return to the pre-disaster level and the general resilience, that is, the combined resilience of each point of interest based on the percent change in the number of visits due to the hurricane.

Their analysis revealed that communities that had low resilience also experienced more flooding. However, their results also showed that the level of impact did not necessarily correlate with recovery.

“It’s intuitive to assume, for example, that businesses impacted more will have slower recovery, which actually wasn’t the case,” said Mostafavi. “There were places where visits dropped significantly, but they recovered fast. But then others that were impacted less but took longer to recover, which indicated the importance of both time and general in evaluating a community’s recovery.”

The researchers also noted that another important finding was that the areas that are in close proximity to those that had flooding are also impacted, suggesting that the spatial reach of flooding goes beyond flooded areas.

“Although we focused on Hurricane Harvey for this study, our framework is applicable for any other natural disaster as well,” said Mostafavi. “But as a next step, we’d like to create an intelligent dashboard that would display the rate of recovery and impacts in different areas in near real time and also predict the likelihood of future access disruption and patterns after a heavy downpour.”

More information:
Cristian Podesta et al, Quantifying community resilience based on fluctuations in visits to points-of-interest derived from digital trace data, Journal of The Royal Society Interface (2021). DOI: 10.1098/rsif.2021.0158

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