GENETIC ENGINEERING

 DNA manipulation

DNA REVOLUTION is the title of an interesting update on the topic by Michael Specter in the December 2016 issue of National Geographic, pages 30-55.  The prospects of using CRISPER, for genetically modifying organisms such as mosquitoes, was discussed along with the need for understanding the benefits and dangers of such genetic manipulation.  The article following, Science vs. Mosquitoes, by Cynthia Gorney, on pages 56-59 of the same issue helps demonstrate the positive value such genetic manipulation could have.

GMO’s, or genetically modified organisms, are often assumed to be dangerous when they occur in the food chain.  Although they could be made so, they also can be harmless as food.  A high level of safety as food can be achieved if goals and procedures are appropriate.  The speed of developing beneficial traits can be much greater than with conventional breeding programs.  Waiting for natural selection to produce useful natural variants through evolution is not an assured way of getting new useful variants in our lifetime.

Some possible benefits of genetic engineering of food organisms. 

Greater yield and/or better adaptation to agricultural processes and environmental conditions may be expedited by finding useful genes for transfer from other organisms unlikely to interbreed naturally.  More success may be found by transferring genes from different strains of the same species.   Examples of expected benefits include drought resistance, stronger stems to resist breakage due to wind or heavy rain, resistance to disease organisms and insects, higher ratio of edible parts versus other structural parts, higher nutrient content, and improved flavor or other attributes.

The uniformity achieved by planting hybrid seed for crops might possibly be accomplished by genetic engineering.  The reduced variation in size and shape of plants makes it much easier to effectively harvest them by machines.

Some possible hazards of genetic engineering of organisms.

Every engineered organism released into the environment has the potential to disrupt the ecological balance achieved by natural populations in much the same way an invasive species or introduced organism may disrupt the balance.  Just as with introduced species, sometimes we like the result.  But the potential for disaster is what we fear.  There is usually no reset button we can push to start over without the disastrous introduced organism.

The relative simplicity and/or ease with which genetic manipulation can be done makes it possible for laboratory errors or contamination to result in release of dangerous GMO’s into the environment.

One of the greatest fears that made pioneers of genetic engineering pause and help put safety procedures in place with strict containment and decontamination procedures was the inadvertent release of normally benign organisms containing toxins of disease organisms.

A fear that terrorists might inadvertently destroy the world, with release of lethal organisms that do not recognize boundaries separating friends from foes, could be disastrous for civilization as we know it.  The suicidal mentality projected to that scale seems unlikely, but we seem to get a foretaste of it in past terrorism events.

Molecular biologists initiated standards for recombinant DNA research beginning over 40 years ago.  Containment and other standards were a feature incorporated in federal research grants as a consequence.  But the tremendous progress in the field has simplified the process so that it is feasible for individuals to undertake projects outside of grant supported research programs and regulated facilities.

Ecological considerations.

The success of engineered species could make their use so prevalent that related native ones might not survive.  The diversified gene pool of native species is conducive to some surviving both new and old strains of fungi, bacteria, and viruses.  If a new insect pest or a disease develops for the engineered species it could spread very rapidly through all the closely adjacent populations of it.

Diversity of species is high in most undisturbed natural communities.  As the area of a natural community is reduced, diversity is usually reduced as well.  The interdependence of species is shown by the loss of one species causing the demise of species dependent on that species.  Even predators can help preserve their prey species by keeping their numbers at reasonable levels.  Reasonable levels include population levels that do not destroy their own food supply and make infectious disease transmission more of a certainty.

The web of life encompasses more than many appreciate, but it should not be ignored.

Ethical considerations.

Genetic engineering is here.  We should insist that benefits clearly outweigh the penalties and risks of each project and that no victims are trampled in our blind enthusiasm.  Are there some things that should not be attempted?

Consider the pesky mosquitoes.  Yes, they have killed millions by their role in transmitting malaria, yellow fever, and other diseases.  Does their value in the food chain, for bats and swallows, fish and many other aquatic organisms as well as possible role in plant pollination, mean they should not be eliminated?  They probably do not play an essential role in survival of most, or perhaps all, of those organisms; that makes the targeting of particular mosquito species easier to advocate, especially using CRISPER if it leaves no toxic residues.

Presumably, CRISPER includes improved techniques for controlling mosquitoes by targeting only the species that are vectors of importance in disease transmission.  A few decades ago targeted DNA adjustments of male mosquitoes, producing only males in their offspring which would then only produce males also, was demonstrated as a way of eliminating a species in a limited study.  Since only females feed on blood needed to produce viable eggs, blood feeding and disease transmission ends.  The result would seem to be one of the least disruptive control mechanisms possible.

Because engineered species may affect other nations directly or indirectly, international agreement should be obtained if they have not already done so.  The United Nations would be a proper entity to provide oversight by establishment of an appropriate commission or process.  Genetic engineering of one's own cells for cancer treatment would be an example of an exempt activity if viral vectors are not part of the process.

I would suggest praying for divine guidance be a personal matter in our philosophical pluralistic society, although it is much needed.  Fortunately, all major elements of our society share most values in their moral codes; peace, personal freedom for all, save our environment, and help those in need seem to be givens.

Joseph Engemann      Kalamazoo, Michigan        August 25, 2016

VARIABLE RATES OF EVOLUTION

THE RATES OF EVOLUTION OF THE ISOPODS

Michigan vs. Tasmanian isopod rates of evolution

The Michigan isopod (posted 6/5/2014) with the egg appendage was able to complete two generations per year.
The Tasmanian isopod  (posted 6/1/2014) took three years to complete a generation.

Since generation time is a reasonable measure of potential evolutionary rates, there is a six-fold difference in the potential rate of change from the ancestral type between the two groups.  Thus it is reasonable to expect the Tasmanian ones have greater similarity to the common ancestor of the two groups.  The greater change in the Michigan one was reflected in the flattening of the group, the fusion of abdominal segments of the upper surface of the exoskeleton, and the development of appendages on the egg; these changes do not appear to be evident in the mostly likely ancestral types of crustaceans.

Potential rates of change are just that, potential.  Selection may keep a well-adapted set of species characteristics relatively unchanged for a longer time than expected.  In such a case, molecular changes may occur in DNA sites not readily affected by selection and thus be a better gauge of time of separation from ancestral types than indicated by unchanged anatomical features.

In ten generations, if x were the numbers of nucleotide changes per generation, the Tasmanian one could have accumulated 10x number of changes and the Michigan one 60x number of changes.  Changes to 100% of the genome would take six times longer in the slowest, so more species could be expected to develop in one with a shorter generation time, if rate of potential change were the only operative factor.

SPECIATION CONSEQUENCES OF LONG GENERATION TIME

Speciation, or development of new species, is usually thought to require geographic isolation from the ancestral type.  Species are sometimes defined as having reproductive isolation from each other.  Geographic isolation can make interbreeding impossible and has been a major factor in evolution.  But isopods having a three year generation could have three species going separate evolutionary paths in the same location.  I wondered if it may have been a factor in the presence of multiple species of similar isopods in Great Lake in the central highlands of Tasmania.  I was not able to determine that although Nicholls listed several species from Great Lake.

Cicadas, some species of which have 17-year life cycles, have developed identifiable differences in some different year-class broods found in the same location.  Speciation may have occurred in some invertebrates of the seashore based on different breeding times during the same year by selection differing at the beginning and end of the breeding season, along with higher predation on early life stages  by predators focused on the peak at the middle of the breeding season..

In addition to geographic and temporal isolation insects are spectacular in their diversity that is a result in part of rapidly gaining reproductive isolation due to specification of genetalia modifications often referred to as a "lock and key" arrangement.  As a result hybridization is prevented once genital differences are sufficient.  Insects may also be reproductively isolated by life on different- host plants or animals, or with pheromones, behavior, and microhabitat differences.

WHY DOES LONG GENERATION TIME OCCUR?

I wondered why such long generation time occurred in the Tasmanian isopods.  As a result I became sensitive to the causes of long generation time.  That followed me long after studying isopods.  I had concluded that the rapid input of much nutrients enabled Michigan isopods to specialize for rapid life cycle, with quick growth and the ability to produce many eggs to capitalize on the period of abundant food.  At the same time it enabled them to persist in the presence of high levels of predation.  So I was familiar with the biology of r- and K- selection before R. H. MacArthur and E. O. Wilson were first to write about it in such publications as their book, The Theory of Island Biogeography (1967).  Their elaboration was a valuable contribution to better understanding of the impact of ecology on evolution.

Long life, infrequent and delayed reproduction, low reproductive rates, low food supply, absence of or low predation and/or ways of avoiding predation, and slow development are all associated with K-selected extremes in the biology of a species.  Within the same habitat it is possible to have both extremes represented as in the example of the cicada with a dozen or more years needed to complete its life cycle while another heteropteran insect, the aphid, can have many generations per year.  Large size usually is accompanied by long generation time, but not always.

WHERE THE ABOVE LED ME

As a result of this interest in longevity, I was prepared in advance to recognize the extreme length of life of the pogonophorans.  Their slow evolution and ancestral role were also able to be seen due to that and the knowledge of invertebrates partially acquired by revising Hegner's Invertebrate Zoology text for its 1968 edition.  A continuing interest in animal evolution led me to recognize some of the errors infecting it now as shown in the post of May 31, 2013.

Joseph G. Engemann      June 9, 2014

EVOLUTION AND ECOLOGY

EVOLUTION AND ECOLOGY COMPLEMENT ONE ANOTHER

Ecology is the branch of science studying the relationships of the physical and biotic features of the environment.  It is primarily the study of what is happening now with organisms in respect to all features of the world around them.  Ecology goes hand in hand with evolution to give us an understanding of the world around us.

Evolution tells us more about the past and helps us understand the present.  Ecology tells us more about the present and helps us understand the past.  Both can use all other branches of science to contribute to the story.  Basics of ecology combined with the concept of natural selection are particularly valuable to understand the long term course of evolution.

Ecology

The trophic relationships (or role in the food chain) among producers (mostly plants), herbivores, carnivores, and reducers are fundamental.  If you have not studied ecology you can find out about them in a text such as the one by Dr. Richard Brewer (The Science of Ecology, 1991).  You can find out about his book on his website (http://richardbrewer.org/ ).  His blogging there has gone more to applying ecological knowledge to efforts to preserve biotic communities.  His most recent book, Conservancy: The Land Trust Movement in America (2003, Univ. Press of New England, Dartmouth College imprint) is a product of that interest.

“Jobs” of organisms in an ecological sense

The hypothetical “ecological niche”, though not necessarily a reality, is a useful concept to understand the history of evolution of biotic communities.  Following extinction events that greatly reduce the diversity of plant and/or animal communities, we find that vacated niches are refilled rather rapidly in an evolutionary sense.  But different species do the job.  The same principle is involved in marsupials providing the kangaroo and other large herbivores in Australia whereas other temperate to tropical lands have had deer and other large ungulates evolve to do that herbivore job.  

The complete story for an organism involves its physical dimensions and interactions with many other properties of the organism and its environment.  Thus as animals first emerged the early ones lacking circulatory systems had to be either very small or flattened or with most active tissues on the surface or perforated or somehow adapted to get sufficient oxygen to all tissues needing it.  As size increased they needed some means of support.  They did not know that, but those that had variation providing such needs out-competed their unchanged relatives.

Multiple functions as a base for evolution of complexity and/or primary function

Many things have more than one use.  This is an especially useful concept to help understand evolution.  An appendage can be useful for one or more functions such as movement, sensory input, respiration, feeding, defense, and reproduction.  One example; when appendages are duplicated on many segments as on an arthropod, selection can eventually result in specializations that differ on different segments.  The principle is one reason biology classes often illustrate the concept with study of a sequence including a worm, a crayfish, a grasshopper, and one or more vertebrates.

My study of isopods showed me an example of how some changes occurring in embryos were based on shifts in a tissue with multiple uses.  The realization that changes can occur in an embryo that are essentially independent of adult evolution made it easier for me to understand the reason behind blogs where I will try to explain the origin of the deuterostomes from the protostomes at the annelid level.  It was an old theory that had been abandoned due to the great difference in the embryology.  I hope to show how the shift occurred.  The Lophotrochozoa-Ecdysozoa error might not have occurred if I had been able to publicize the concept more effectively years ago.

Joseph G. Engemann     June 11, 2013