Saturday, 24 April 2021

Unintelligent Designer Update - The Pea Aphid Blunders.

Pea aphid, Acyrthosiphon pisum

Credit: Shipher Wu (photograph) and Gee-way Lin (aphid provision),
National Taiwan University.
Source: Wikipedia
CC BY 2.5,
Defense Mechanisms in Aphids Can Become a Double-edged Sword, Sharpened by the Seasons | Now | Drexel University

A paper published a few days ago, should be giving Intelligent [sic] Design advocates nightmares, if they had the intellectual integrity to read it. It highlights several instances where basic creationist dogma is refuted by observable reality.

First a little bit of background: pea aphids (Acyrthosiphon pisum) are sap-sucking insects that live on members of the pea family of plants such as alfalfa. They are predated on by a parasitoid wasp (Aphidius ervi) that lays its eggs in the living aphid, which is then consumed alive by the grubs of the wasp. However, they have living in their cells a common endosymbiotic bacterium (Hamiltonella defensa) which provides them with some protection against the wasps in that it prevents the grubs from developing.

These bacteria are inherited exclusively through the female line, being passed to the next generation in the female gamete, or via the cells when the females reproduce parthenogenically (as they normally do) similar to how mitochondria are inherited. Throughout the summer, pea aphids reproduce parthenogenically and can produce about 13 generations in a year, being capable of reproducing 10-12 days after birth. In colder climates reproduction is sexual at the end of summer, via fertilized eggs which over-winter. In warm climates the females continue to reproduce parthenogenically all year round and in intermediate climates a mixture of adult females and fertilized eggs over-winter.

This very high generation rate means evolution can be readily observed so this species was used by researchers at Drexel University to investigate the evolutionary forces at work in this relationship between the endosymbiotic bacterium, the parasitoid wasp and the pea aphid.

Their findings were published a few days ago in the journal Molecular Ecology, sadly behind a paywall. However, the Drexel University news item has the details:
Researchers at Drexel are studying pea aphids to understand how temperature and seasonality can be driving forces in evolution.

Photo credit: Drexel University/Linyao Peng
Evolution is unfolding in real time within many natural animal populations and researchers are now observing how this influences biodiversity in the field. In a newly published study in Molecular Ecology a team of Drexel University scientists examined the biological variations in pea aphids, insects that reproduce frequently enough to evolve before our eyes, by tracing the prevalence of their protective endosymbiont, Hamiltonella defensa, which the insects use to ward off parasitoid wasps.

“We know that certain organisms have many generations in a season, and we know sometimes it just takes a handful of generations for evolution to unfold; and aphids are one of those types of organisms,” explained Jacob A. Russell, PhD, a professor in the College of Arts and Sciences, and senior author on the study.

We know that certain organisms have many generations in a season, and we know sometimes it just takes a handful of generations for evolution to unfold; and aphids are one of those types of organisms.

In essence, these [endosymbiotic] bacteria are inherited like mitochondrial DNA and because of this, they can serve as part of the pea aphid's adaptive arsenal, acting alongside the many thousands of genes in this sap-feeding insect's genome.

Professor Dr. Jacob A. Russell, Corresponding author.
Department of Biology
Drexel University
Philadelphia, PA, USA
Like many insects, aphids play host to symbiotic bacteria – or endosymbionts – in their blood and internal tissues. While their full range of impacts is not yet understood, these bacteria typically provide some defense against environmental pressures, like parasites and parasitoids – parasites that kill their hosts. Hamiltonella defensa, the endosymbiont focused on in this study, for instance, wards off parasitoids in pea aphids. But these bacteria are also of interest to researchers because they are heritable — passed on from females to their offspring.

“In essence, these bacteria are inherited like mitochondrial DNA and because of this, they can serve as part of the pea aphid's adaptive arsenal, acting alongside the many thousands of genes in this sap-feeding insect's genome,” said Russell.

Andrew Smith, PhD, a former Drexel graduate and current Rodale Institute Chief Scientist, led the research efforts that enabled the biologists to get a closer look at the natural forces shaping Hamiltonella prevalence. It was their hope that, through repeated field collections and routine
We were motivated to try to understand why this one endosymbiont is maintained in these populations, why is it never lost and why it doesn’t just go to 100% frequency. One idea is there must be some times when it helps the aphid, as well as times when it is slightly harmful.

There’s this ‘rent’ that the aphid has to pay to the endosymbiont just to sustain its populations. In the lab, we initially thought the aphids with the endosymbiont would be worse off than the aphids that did not have the endosymbiont due to this ‘rent’ concept.

[Our results suggest] the cost of ‘rent’ is higher for aphids harboring these endosymbionts when it’s cool. [I think] it’s actually pretty useful for the aphids to have these endosymbionts when it’s warm.

Professor Dr. Jacob A. Russell, Corresponding author.
molecular screening, they could shed light on the evolutionary forces affecting aphids in real time.

“We were motivated to try to understand why this one endosymbiont is maintained in these populations, why is it never lost and why it doesn’t just go to 100% frequency,” said Russell. “One idea is there must be some times when it helps the aphid, as well as times when it is slightly harmful.”

To supplement their aphid collection and endosymbiont screening, the field team studied a range of environmental variables within the same alfalfa fields, including the prevalence of Aphidius ervi, a parasitoid wasp introduced in the United States to control populations of the pea aphid, which was once a threat to crops, including alfalfa. The wasps kill aphids by laying eggs inside them. Intriguingly, Hamiltonella endosymbionts prevents young wasp development, but they also come with a cost, according to the researchers.

“There’s this ‘rent’ that the aphid has to pay to the endosymbiont just to sustain its populations,” said Russell. “In the lab, we initially thought the aphids with the endosymbiont would be worse off than the aphids that did not have the endosymbiont due to this ‘rent’ concept.”

Drexel researchers are studying generational variations in symbiotic bacteria found in pea aphids.

Photo: Drexel University/Alex Wild
This concept, that aphids with Hamiltonella endosymbionts were worse off than those without them in the absence of the wasps, was supported by prior lab experiments. But despite this expectation, the authors found no significant relationship between wasp prevalence and endosymbionts. But they did see aphid populations evolving over time – with the endosymbiont’s prevalence shifting rapidly, on several occasions. Correlating most clearly with these shifts was the temperature of the aphids’ surrounding environment.

Their results suggest “the cost of ‘rent’ is higher for aphids harboring these endosymbionts when it’s cool,” said Russell, who thinks “it’s actually pretty useful for the aphids to have these endosymbionts when it’s warm.”

The authors conclude that the endosymbiont’s dynamics, and hence real time evolution of the pea aphid, likely result from an evolutionary phenomenon known as “balancing selection,” which happens due to changing costs and benefits of harboring the endosymbiont at different temperatures.

This would render Hamiltonella as a fair weather friend, useful when it’s warm, and harmful when it’s not. Though the mechanism of this seasonality remains undetermined, their results suggest that temperature could serve as a major factor in conjuring the occurrence of Hamiltonella endosymbionts in aphids.

This discovery was only possible because the team made its observations in the field. “We tend to do our lab experiments in these pretty one-dimensional lab environments and temperature is held constant,” said Russell, “so those lab findings might not be fully transferable,”.

This work provides one of the first examples of a study on seasonal insect adaptation that’s enabled not by variation in insect genes, but by variation in their endosymbionts. As such, it is among the first to show that maternally transmitted microbes – found in most insect species – respond to the pendulum-like nature of changing environments across the seasons.

Given the longer-term trends in global climate, it is possible, too, that endosymbionts may govern the future success of insect species in our rapidly warming world.
The first problem for creationists then is this observable evolution taking place over a very short period of time, making this species an ideal experimental subject. This is not supposed to happen according to standard creationist dogma because evolution is 'impossible' and any change requires a magic entity to make it happen.

The second problem is the fact that the explanation of these results by the team are entirely dependent on the Theory of Evolution by Natural Selection, yet creationists are required to believe that theory is now widely rejected by scientists and is about to be replaced by the religious notion of Intelligent [sic] Design, complete with its mysteries, unproven creative entity and unfalsifiability - the first scientific theory ever to be replaced by a Bronze Age superstition from the Middle East (or from anywhere else).

The third problem; especially acute for Intelligent [sic] Design Creationists, is actually a number of related problems:
  1. Why would an intelligent designer design a parasitoid wasp to lay its eggs in the body of the pea aphid, then provide the pea aphid with an endosymbiotic bacterium to prevent the wasp grubs developing?
  2. Why would an intelligent designer constantly rearrange things so it looked like there was a correspondence between ambient temperature and the prevalence of these endosymbionts?
  3. Is this supposed designer:
    • Confused?
    • Stupid?
    • Amnesiac?
    • Suffering from multiple personality disorder?
    • Trying to fool scientists into thinking phenomena like this are the result of an entirely natural, unguided and unintelligent process?
Answers below, please. And try not to betray the religious fundamentalism in creationism by referring to a 'divine plan which it's not given to mankind to understand', or some sort of prohibition on trying to understand the 'mind of God', because that would make officials at the Discovery Institute, still trying to sell ID as real science, cry.

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