Of hips and galls

My early education in matters of evolution came in odd order. I read about Luther Burbank while I was in 2nd grad (Golden Book Encyclopedia), but that was only a teaser. Mendel’s idealized model of transmission was used in my 8th grade math to discuss probabilities. Mr. O was not a biologist, so he repeated the old error that the numbers get better (closer to the “ideal”) with larger samples. That may be true with coin tosses, but not in heredity. Segregation Distortion is very common.

In 9th grade I learned about Dominance Modification and Canalization (both very important concepts), but 10th grade was mostly Modern Synthesis (long out of date even then) with a dollop of Quetelet’s Law (not a law) and some biased appreciation of “Hybrid” Corn. I lived in Kansas, so maybe that made some kind of sense.


Dominance Modification means that dominance is a quality of traits, not of genes. E. B. Ford demonstrated it with a cross between two varieties of the currant moth. One form has wings with a white ground color, the other has yellow. The F1 specimens are intermediate in color, but not exactly the the same. In just three generations, Ford had bred one line with white dominant over yellow, and another line with dominant yellow.


Canalization was demonstrated by Waddington with fruitflies. A strain was found that produced some offspring with broken crossveins in their wings, but only if the larvae were subjected to a period of high temperature. He selected only those with this trait, and in each successive generation the percentage of crossveinless specimens increased. After several generations, some of the flies that had not been heat shocked developed wings with broken veins. Further selection fixed the “acquired” trait as a universal feature of the strain.


These two concepts were precisely what was missing from the Modern Synthesis, with all its “random gene mutations passing through the sieve of natural selection.”

How could that work? Mutations must be more common in a population that is large. But how can the population be large if it is not already well adapted? On the other hand, a small population that is on the brink of extinction has very little chance of randomly mutating in a useful way.

But suppose that all those unnecessary random mutations are not immediately brushed aside. Instead, let their uselessness be concealed by dominance modification. Saved for a rainy day, so to speak.

And when a population is facing some unfamiliar stresses, or forced to inbreed more than usual because of declining numbers, the stresses may release some of the hidden variations. Most are probably not useful, but the frequency of old mutations being revealed is correlated with the immediate stress.

Garner and Allard (1920) introduced the concept of Photoperiodism. Along the way the found a demonstration of what I’m discussing. Radishes are not adapted to days with only 7 hours of light. "All but two of the test plants, of which there were a large number, became diseased and finally died without forming seed stalks. The two survivors developed a crown of large leaves, and the roots also reached much larger proportions than those of the controls. Apparently enlargement of the roots had not ceased as late as October 15, when one of them measured nearly 4 inches in diameter while its rosette of leaves measured 30 inches from tip to tip. Flower stems did not develop. "

Jumbo radishes that develop in very short days may not be of great value, but they do suggest one of the many ways hidden variation can be disclosed by unnatural stress.


G & A did not do any further experimenting with those two survivors. That was not what they were studying. Still, I think it would be interesting to see what might turn up in later generation.

With these principles in mind, I want to share some speculation about evolution.

Cyclic Manifestation of Sterility in Brassica Pekiensis and B. Chinensis (1922)
A. B. Stout

“It is to be noted that the complete life cycle of flowering plants involves two periods of vegetative vigor and maturity; one for the sporophyte and one for the gametophyte. The former culminates in the production of spores and the latter in the production of gametes. The generations are antithetic. In its length of life, vigor of vegetative growth, and reproductive power (number of gametes), the gametophytic phase has become relatively weak and highly specialized. In the sporophyte great vegetative vigor is correlated with great reproductive vigor in the production of spores (which are, however, in themselves asexual) and in the nurture of the gametophyte and the embryo. Sex differentiation in the great group of flowering plants has been pushed back during the progress of evolution into the sporophytic stage of the entire cycle, and here sexuality now culminates in seed formation in which the nutrition of the embryo is a most important factor. Sexual reproduction in these higher plants has become more and more inter-related with the vegetative phase of the sporophyte and subject to its internal and biogenetic regulation.”


How did the sex differentiation get pushed back? I suggest a particular sort of stress.

The Significance of Responses of the Genome to Challenge (1984)

Barbara McClintock

“One class of programmed responses to stress has received very little attention by biologists. Here a stress signal induces the cells of a plant to make a wholly new plant structure, and this to house and feed a developing insect, from egg to the emerging adult. A single Vitis plant, for example, may have on its leaves three or more distinctly different galls, each housing a different insect species. The stimulus associated with placement of the insect egg into the leaf will initiate reprogramming of the plant’s genome, forcing it to make a unique structure adapted to the needs of the developing insect. The precise structural organization of a gall that gives it individuality must start with an initial stimulus, and each species provides its own specific stimulus. For each insect species the same distinctive reprogramming of the plant genome is seen to occur year-after-year. Some of the most interesting and elaborate plant galls house developing wasps. Each wasp species selects its own responding oak species, and the gall structure that is produced is special for each wasp to oak combination. All of these galls are precisely structured, externally and internally, as a rapid examination of them will show.”


Suppose that some megaspores germinated and became parasites on the sporophyte that bore them. In some cases, the host might respond by building an “immunological structure” to isolate the invaders. I can’t get too detailed in this, but gametophytes taking control of the sporophytes genome to form fruit, is no more outlandish than wasp larvae doing the much the same thing with galls on grape leaves.

Over time, the species becomes so adapted to gametophyte-galls (so to speak) that the plants will produce them even without proper fertilization. That’s canalization!

If this model has merit, then xenia and/or metaxenia are not at all mysterious. Although the fruit technically derives from sporophytic tissue, it is under control of gametophytes, embryos and endosperms; past and present. This is no more surprising than seeing galls of three or four wasp species on a single leaf. So far as I’ve found, Swingle (1928) was the first to suggest that embryo and endosperm could be responsible for metaxenia. I like to think that it played a role in creating fruit.

Can ordinary galls become canalized? This is even more speculative.

I have never seen the rose bedeguar gall, but it was commonly mentioned in old Herbals. Hare (1818) wondered whether there might be some connection between the mossy bedeguar and the moss found on some roses. No wasps are involved with the moss rose growths, and the growths are not the same. Still, this growth seems to have been valued enough to encourage cultivation of clones that produced it.

And what was the stress? The great Holland rose, that first bore the floral moss, must have been the product of inbreeding. It probably was raised from the Damask, possibly pollinated by Rosa alba (the original Centifolia), and then inbred. Inbreeding is one way to enhance a desired trait. On the down-side, inbreeding tends to reduce vigor. Thus, crosses of the Dutch Centifolias and Mosses with the Monthly Rose and other Damasks were notably more vigorous.

Hare (1818) also wrote, “… it may be remarked that Roses have been frequently known to lose their mossy character, on being removed from an open situation in which they had previously flourished, to a shady one; the moss becoming elongated, and proceeding from a reduced number of pores.” This sounds rather like the modified moss of Perpetual Mosses, which probably were the result of crossing rather than novel sports. The earliest reports I’ve found insist that the Perpetual White Moss was raised from seed of a Monthly Rose pollinated by a white moss.

Which came first: Gall or Fruit?

Ohgue et al. (2018) wrote, “Here we report the first occurrence of such galls from thalli of a neotropical liverwort, Monoclea gottschei subsp. elongata (Marchantiophyta: Monocleaceae) from Peru. This is also the first report of animal-induced galls formed in modern thalloid liverworts.”

It appears that galls came first, which allowed the hypothetical parasitic egg sacs (female gametophytes) to borrow genetic tricks pioneered by the gall-host struggle. Of course, whatever tricks the gametophytes evolve would be added to the toolkit available to gall-builders.

I’ll bite - yet again.

Suppose that some megaspores germinated and became parasites on the sporophyte that bore them. In some cases, the host might respond by building an “immunological structure” to isolate the invaders.

Lamark can stay in his grave. My guess is that the response is archaic. While it might appear that ‘canalization’ is a short term process taking a few generations it is more likely that there has been an evolutionary game of leap-frog beginning at the dawn of eukaryotes and before. A interloper violates a plant cell wall. Those cells with a response in which the invader gets shut into the cell wall survive while the others succumb to predation. Mutate, rinse, repeat.

Mendel lives.

What a deep dive I’ve been on. While I was digging into historical matters, I got WAY behind in regards to modern research. I’ll try to catch you up.

Anyone serious about doing any plant breeding should not waste time with Mendel. He started with 34 strains of Peas, and winnowed them down to 22. He crossed, recrossed, counted and collected a mountain of data. The result was a list of 7 pairs of alternative traits.

Skipping ahead a decade, and visiting England, we meet Henry Eckford. In 1874 or 1875, he started with 10 old, inbred strains of Sweet pea. But unlike Mendel, Eckford was not content to shuffle existing traits. He wanted broader standards. He wanted larger flowers, and more than 2 or 3 to the stem. Stronger stems, of course. And vines more vigorous and floriferous than the old types.

Eckford got what he wanted and more. He also gained shades of primrose, salmon and orange. His blue selections were bluer than any blues that came before. This was the beginning of modern Sweet Peas. In 1883, the following were displayed:
Fascination, quite a new type, with a deep salmon-pink or pale rosy-lilac standard, and pale blue wings deepening in colour as the flowers age; very pretty and distinct, large, and fine.
Victoria, pale rose standard dashed with pink, white wings, with a Picotee edge of blue and the wings slightly suffused with the same; distinct and very pretty.
Bronze Prince, rich shining bronzy maroon standard, large, stout, and well formed, deep purple wings of a bright hue; very fine and striking.
Princess, white standard, flushed at the back with pale blue, the front delicate blue, while wings, with wire edge of bright blue; this is of the Butterfly type, and like that is somewhat crumpled on the petals, but it is very pretty and distinct.
Leviathan, having a very large, broad, stout standard, bright scarlet on the centre flushed with white at the side?, the wings flake with pale purple and rose; a very fine scarlet striped form, large, massive in all its parts, and very striking.
Lottie Eckford, in the way of Princess, but with the standard suffused with purple, and having a wire edge of blue to the white wings: this is very pretty indeed, but must be carefully selected in order to keep it distinct from Princess; when fixed it will make a charming, delicate variety.
Blue King, a very distinct and fine Sweet Pea, which report states very nearly gained a First-class Certificate of Merit when shown by Mr. Eckford in London a short time ago; it has a bright blue standard suffused with purple, quite blue at the back; the wings clear pale blue; very distinct and fine.
Indigo King, the stout, well-formed standard maroon-purple suffused with blue; clear indigo-blue wings; very fine and distinct, smooth, and of good form.
Salmon Queen, the standard bright salmon-carmine; very pleasing and very charming in colour, the pale wings slightly flushed with pink; very pretty, distinct, and fine.
Duchess of Albany, delicate pink standard with a slight flush of carmine; delicate blush wings; very pretty and attractive.
Grandeur, bright pale scarlet standard, which is stout, smooth, and striking; bright rosy-purple wings; very correct and fine in all its parts; a truly rich-coloured variety.
Lavender Gem, bright rose standard slightly suffused with purple, pale lavender wings; very pleasing, pretty, and distinct. This is a yearling variety, and was obtained from Grandeur crossed with a seedling blue.
Queen of Roses, also a yearling, pale bright rose standard, erect, stout, and smooth; clear, delicate, rosy-purple wings; very fine in all its parts, smooth and massive. This came from Grandeur and Bronze Prince.
Empress of India is a yearling also, having a bright pinkish-rose standard, broad and stout, the wings white, very delicately flaked with blush; this also is very pretty and distinct.
Blue Beauty, also a yearling; the standard plum-purple on a broad and smooth standard; clear blue wings; very pretty and pleasing, standard and wings forming an admirable contrast.

And as a sideline, Eckford also introduced 6 new, highly regarded strains of culinary Peas within a decade of starting his project.
This is what plant breeding is about: not merely recycling the old, but creating the new.

Can slight aberations be developed into stable traits. If you think not, then prolonged inbreeding can prove you right. But if you like to see small suggestions grow into powerful statements, outbreeding is the way.

[Burbank: Heuchera micrantha, curled leaf (1914)]
(Untitled Document)

[Burbank: White Blackberry (1914)]
(White Blackberry)

[Burbank: Stoneless Plums (1914)]

[Kunderd: Ruffled Gladiolus (1908)]
(Kunderd: Ruffled Glads)

[Beaton: Geranium spot (1861)]
(Beaton: Geranium spot (1861))

[Pansies, Tufted Pansies and Violets]
(Pansy History and Development)

[Liebman: Pink Guppies (1979)]
(Liebman: Pink Guppies (1979))

[Austin: Horned, spooned and flounced Irises (1961)]
(Austin: Horned, Spooned and Flounced Iris (1961))

Things to know about heredity.

Much of the following involves changes that are pre-programmed. This was likely “learned” or “imprinted” of “acquired” in previous experiences with familiar changes/stresses. Otherwise, the changes are stochastic rather than random. Stochastic processes are generally deterministic, but one or more variable is left to conditions (internal or external) that cannot be predicted. The “Butterfly Effect” is an example.

Just to get the terminology clear, the environment does not “cause” the bacterium to change. Rather, the bacterium experiences stress because it cannot fulfill its normal functions in the normal way. This article on Down’s Syndrome shows how the extra chromosome that triggered Down’s, provides a systemic shock that reduces the normal programming (regulation) of genes across the entire genome.


  1. Bacteria, faced with a changed environment, can alter their phenotype (including metabolism) to adapt themselves to the conditions, by reprogramming their genomes. In pathogenic species, the reprogramming adapts then to different “hosts”. Under extreme changes, the bacteria can resort to “Stochastic Variation”. In this way, the population can run through multiple changes without mutating itself into extinction. The second method by which bacteria differentiate is by rearranging or modifying a DNA sequence. Much of our current understanding of this form of differentiation comes from studies of Neisseria gonorrhoeae, which can change its pilin and other outer surface components.



Some Nuclear Bacteria that did not mutate themselves into extinction:



  1. Mitochondria are descended from bacteria. They change themselves to accommodate their altered requirements in differentiating tissues. Defects in mitochondria can have major effects on the host. In maize, a single mitochondrial mutation left the plants male sterile, and highly susceptible to Southern Corn Blight. Mootha: Mitochondria Genes (2003)

  2. Chloroplasts are descended from Cyanobacteria (formerly known as blue-green algae). They also alter themselves as required by the tissues they support.



  1. A nematode (C. elegans) can “learn” to repeat a particular pattern of expression of a foreign gene (GFP) by repeated selection.


No genes for longevity


Imprinting transmitted to next generation.

BTW: This tiny nematode carries around 400,000 small RNAs. There is a lot of comuncation going on in such little critter.

  1. Organelles in plants can control some traits involving the whole plant. In hybrids of the common bean (Phaseolus vulgaris) and the Scarlet Runner (P. multiflorus), the seed parent determines whether the F1 and subsequent generations will be hypogeal (multiflorus) or epigeal (vulgaris). In addition, the brilliant color of the Scarlet Runner develops only in the (multiflorus) cytoplasm. Otherwise, “geranium pink” is the best it can do.



And just to keep things interesting, genes (and what else?) can move among mitochondria, chloroplasts and nucleus.


I have been catching up with the newer discoveries in heredity. There is a lot to digest. Stated simply, the game is changed. A lot! Just as an analogy, suppose someone heard Chopin’s ‘Winter Wind’, and tried to understand it by dissecting a piano. He pulls out a few keys, breaks some hammers, snips a handful of wired. And all the while he overlooks the sheet music on the bench. Chromosomes are interesting. And a piano is a beautiful piece of furniture even while it refuses to Play Misty For Me.

Much remains to be learned, but some pieces are falling into place.

In 1983, Barbara McClintock received a much belated Nobel Prize for her discovery of Transposons. She called them “controlling elements”, others write “TEs”, emphasing the transposable aspect. But the Jumping Gene notion seems to have trivialized the discovery just a bit.

Some researchers thought these were parasites, or oddities of little interest. But in 2000, La Bonte wrote:

“Retrotransposons are the most abundant class of TEs in plants, ranging from a few copies/genome in Arabidopsis (Konieczny et al., 1991) to as much as 50% of the genomic content of corn (San Miguel et al., 1996).”


These elements seemed to need a severe shock to get moving. Something like exposure to X-rays, or a broken chromosome trying to reconnect.

In 2006, Fire and Mello received the Nobel Price for their discovery of RNA interference. Small bits of single-strand RNA were able to block the translation of specific RNA transcripts into the corresponding proteins. Interfering little things. But in time, other classes of small RNA became known. Some are double-strands, but all are very small.

How many?

Caenorhabditis elegans is a tiny worm, about one mm. in length. Perkel (2006) wrote: “Using massively parallel sequencing technology, David Bartel, a Howard Hughes Medical Institute Investigator at the Massachusetts Institute of Technology, and colleagues sequenced some 400,000 small RNAs from Caenorhabditis elegans, identifying 18 new microRNA genes and more than 5,000 RNAs (called 21U-RNAs) whose common features are a 5’ uridine residue, a shared upstream motif and chromosomal location, and a length of precisely 21 nucleotides.”


If chromosomes are pianos (metaphorically speaking), this little worm has a whole lot more fingers than keys.

Many of these small RNAs are involved in delivering commands to the TEs. This is the orderly program that gets an organism from egg to maturity without the trauma of X-rays. However, the same small RNAs may be conveying information about various threats; some relatively familiar, others novel.

These small RNAs really get around. They even move into ova and sperm. That is to say, the old notion that the life experiences of the Soma (body) cannot influence the heredity passed along by the Germ cells is no longer an absolute truth.

Here is a practical example of evolution without gene mutations, random or not.

Vernaz, et al. (2022), “Specifically, we focus on the extent and functional relevance of DNA methylome divergence in the very young radiation of Astatotilapia calliptera in crater Lake Masoko, southern Tanzania.”

“Epigenetic variation can alter transcription and promote phenotypic divergence between populations facing different environmental challenges. Here, we assess the epigenetic basis of diversification during the early stages of speciation. Specifically, we focus on the extent and functional relevance of DNA methylome divergence in the very young radiation of Astatotilapia calliptera in crater Lake Masoko, southern Tanzania. Our study focuses on two lake ecomorphs that diverged approximately 1,000 years ago and a population in the nearby river from which they separated approximately 10,000 years ago. The two lake ecomorphs show no fixed genetic differentiation, yet are characterized by different morphologies, depth preferences and diets.”


In other words, this evolution was driven by the altered “needs” of the fish in new environments. The adaptations were led by epigenetic adjustments, rather than by random gene mutations.

This is an important: genetic differences may follow epigenetic adaptation, rather than drag it along one mutation at a time. We should keep this in mind when considering such species as Rosa johannensis, R. Williamsii and R. Rousseauiorum. These are obviously allied with R. blanda, but thrive in calcium rich soils where R*. blanda* cannot.


There is a WHOLE lot more going on, but I’ll keep this short. One little problem is that some older research must be re-examined. Thanks to gene silencing, two specimens may carry the same gene, but one may not produce the corresponding enzyme. For example, the difference between a yellow tomato and a red one may be that a particular gene is active in one, silenced in the other.strong text


After posting about the rapid evolution of the African crater fish, I remembered that I have a similar example of the Burr Medic (Medicago polymorpha).
Del Pozo (2000)
“Flowering time appears to be a common adaptive trait in annual legumes along aridity gradients, provided that they have sufficient seed dormancy (e.g. Ehrman and Cocks, 1996; Piano et al., 1996). Here it has been shown that, along the 1000-km-long aridity gradient of the Mediterranean climate region of central Chile, clear ecotypic differentiation in the reproductive phenology of burr medic has occurred, allowing adaptation to the various bioclimatic zones present. This has occurred despite the fact that very little genetic diversity has been detected in populations from Chile (Paredes et al., pers. comm.) or from Sardinia (Bullita et al., 1994).”

Thinking more on this topic, I found another example: El-Kassaby: Phenotypic Plasticity in Western Redcedar (1999)
“Compared to its associates, western redcedar (Thuja plicata Donn) has been recognized to harbour the lowest level of genetic variability. Genetically depauperate species occupying a wide range resort to various strategies for their survival and adaptation. Phenotypic plasticity, the ability of an individual to alter its morphology/physiology in response to changes in the environment, was identified as the mechanism by which western redcedar secured its survival. Events in the species’ history, coupled with its unique reproductive biology, have allowed the perpetuation of its low genetic variability through inbreeding. Examples of phenotypic plasticity in western redcedar will be provided and a novel method for exploiting the species’ phenotypic plasticity for enhancing commercial production of seedlings will be presented.”

And then, reading a paper on the evolution of the desert pupfish species (Lema 2008), I was stopped cold by this:

"Mary Jane West-Eberhard of the Smithsonian Tropical Research Institute has pointed to one scenario whereby plasticity may lead to evolutionary divergence:

‘The origin of a new direction of adaptive evolution starts with a population of variably responsive, developmentally plastic organisms. That is, before the advent of a novel trait, there is a population of individuals that are already variable, and differentially responsive, or capable of producing phenotypic variants under the influence of new inputs from the genome and the environment. Variability in responsiveness is due partly to genetic variation and partly to variations in the developmental plasticity of phenotype structure, physiology, and behavior that arise during development. …’ "

This is pretty close to being a modern restatement of the Baldwin Effect (Baldwin, 1896; Morgan, 1896; Osborn, 1896). Genotype-Phenotype Map, Baldwin Effect

In other words, evolution is not necessarily dragged forwards by a long and improbable series of random gene mutations. Adaptation may come first. Subsequent mutations are preserved or eliminated depending on how they affect the programmed adaptations.

Long ago I wondered how crossbreeding, inbreeding and change in environment could all provoke increased variation. And many years later, I had to add unripe seeds to the list. Van Mons did some remarkable work with Pears, Apple, Peaches, Roses etc. By using unripe seeds. Some of his pears are still grown.

West-Eberhard’s statement brought it all together for me. Stress reveals Phenotypic Plasticity. This stress may result from prolonged inbreeding, subjecting a population to novel conditions, crowding, reducing nourishment in the seeds, among many other things.

I have old reports that cutting away part of the endosperm or cotyledons of seeds can result in dwarf plants. A quick Google search led me to Yam et al. (2012), who found that removing various quantities of the endosperm of (Hordeum spontaneum) resulted in an INCREASED tolerance for salt. At least for one accession.

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