PARASITES CAUSED THE PHYLOGENETIC TREE TO BRANCH

PARASITES CAUSED THE PHYLOGENETIC TREE TO BRANCH

Post #24

Donald A. Windsor

The phylogenetic tree, recently popularized by David Quammen (1), is indeed a very practical way to illustrate phylogenetic relationships. Horizontal gene transfer is described as connecting separate branches across the tree and altering evolution.

But without parasites, the tree would be just a gnarled stump, sparsely branched, parsimoniously twigged, and starkly leafless. Even though parasites can transfer genes from a host species on one branch to a host species on another branch, without parasitism there would be few, if any, branches to transfer between. Phylogenetic branches indicate that parasitism must have emerged very early in the evolution of living organisms.

The reason is that parasites prevent monopolistic monocultures. When competition and predation do not control monocultures, parasitic diseases step in. The result is biodiversity and multiple ecosystems (2).

Host species push back against parasites by rearranging their genetic material through sex. Other factors, such as environmental changes and competition, also cause sex. All of which leads to speciation and phylogenetic divergence, resulting in branching. Sex might have evolved without parasites, but parasites are the main drivers of sex because mating involves a choice of the most fit mates and a selection against unfit.

The real test of my hypothesis, stated in the title, will come when extraterrestrial life is discovered. Parasitism may be a property of life here on Earth, but it may not be universal. This is why it is so important for Earthlings not to contaminate other planets.

References cited:

1. Quammen, David. The Tangled Tree. A Radical New History of Life. New York, NY: Simon & Schuster. 2018. 462 pages.

2. Windsor, Donald A. Role of parasites in the Earth’s biosphere. paraditesdominate.blogspot.com Post#13.

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COULD A PARADIGM ABOUT PARASITES EVER SHIFT THE TRADITIONAL PARADIGM OF ECOLOGY?

COULD A PARADIGM ABOUT PARASITES EVER SHIFT

THE TRADITIONAL PARADIGM OF ECOLOGY?

Posting # 14

Donald A. Windsor

When a tree falls in the forest and no one is around to hear it, does it make a sound?

When a paradigm shifts and no one in the scientific community notices, does it make any difference?

The tree question was asked by philosopher George Berkley in 1710. I ask my my paradigm question now. The vital role of paradigm shifts in science was explained by Thomas S. Kuhn in 1962.

My paradigm about parasites was published in 1998. I was advocating a paradigm shift. The newly formed concept in my paradigm turns ecology upside down and inside out.

Here is a brief backstory. My dissertation research involved parasites, but upon leaving school in 1966 my employment dealt with other subjects. When I retired in 1994, I was curious about what when on in parasitology during the previous 28 years. So I started reading the parasitology literature where I left off. When I finished in 1997 I experienced a shocking realization. Parasite species seem to be more numerous than their host species. Moreover, the important roles that parasites play in ecosystems seemed to be woefully understated and even vastly unrecognized.

Twenty years will soon have elapsed and, while my article has been cited 197 times, ecologistsists have not yet recognized this new paradigm as a shift. Maybe they never will. Regardless of what happens, I am getting too old to ever find out. Here is a brief synopsis.

The ruling paradigm in ecology holds that our biosphere is composed of free-living (non-parasitic) organisms, with parasites merely being pesky nuisances.

My paradigm contends that parasites are ubiquitous, insidious managers of our biosphere. They do not merely freeload off their hosts – parasites regulate their hosts. When competition and predation do not reign in host populations, parasites take over and prevent monocultures. The result is biodiversity. A corollary is even more astounding; some parasites enable their hosts to avoid extinction.

The validity of my paradigm can be tested, just as any other hypothesis can. If another planet, or even an asteroid, has life, but does not have parasites, then it will have few species and have large monocultures. My paradigm contends that parasitism is a property of life on Earth. Discovery of extraterrestrial life will reveal whether parasitism is a universal property of life.

I hope my paradigm becomes the current paradigm before we contaminate other worlds with our organisms and jeopardize this test.

References cited:

Berkley, George. A Treatise Concerning the Principles of Human Knowledge. 1710.

Kuhn, Thomas S. The Structure of Scientific Revolutions. Chicago, IL: University of Chicago Press. 3^rd Edition. 1996. 212 pages.

Windsor, Donald A. Most of the species on Earth are parasites.
International Journal for Parasitology 1998 December; 28(12): 1939-1941.

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ROLE OF PARASITES IN EARTH'S BIOSPHERE

ROLE OF PARASITES IN EARTH’S BIOSPHERE

Post #13

Donald A. Windsor

Restriction of monocultures is the basic mechanism operating Earth’s biosphere.

When competition and predation do not control monocultures, parasitic diseases step in. The result is biodiversity and multiple ecosystems.

This simple explanation is based on observation. Monocultures, such as those planted by farmers, are quickly invaded by other species and attacked by numerous pests. Farmers have to be very diligent to protect their crops by using pesticides. Even then, other species manage to invade.

Our biosphere here on Earth is characterized by biodiversity, huge numbers of different species and interactions among all those species. Monocultures are rare and short-lived, found on newly formed islands and on disturbances leading to bare earth.

But what about life on other worlds? Does extraterrestrial life express itself as biodiversity or as monocultures? Do other worldly species interact in ecosystems? Or just dwell in monocultures?

Life on Earth is analogous to human economic forces. Without governmental regulation, unbridled capitalism results in a few very rich winners and vast hordes of poor losers. Our era of the robber barons in the late 1800s and early 1900s is a prime example. Parasites are similar to governmental regulations; they stifle exuberance.

Perhaps a world without parasites would be similar to unregulated capitalism, with a few very successful species and no or very few other species. Perhaps a middle class of species would have developed.

In the near future we may get an opportunity to discover extraterrestrial life. Will it be biodiverse? Or monoculturalistic? If parasites are present, so too will be biodiversity.

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