Attack of the clones!

You get a lot of funny, some funny ha-ha, some funny sad, surveys when you work at a university because lots of younglings are engaged in what passes for research in the non-sciences.  So the Phactor gets a call; it's a survey question.  Would you eat a cloned organism?  Certainly.  So, you think cloned food is OK.  Yes, cloned food is OK.  In fact you probably do not go a day of your life without eating cloned food.  No. Yes.  What?  Let's just start with potatoes and sugar.  And what makes you think cloning is bad?  And what taking a survey rule allows you to call faculty on the phone?  It's an informal survey.  Ah, yes, so actually what you are doing is not sanctioned by the university or any faculty adviser, correct?  Thanks for your time.  Click.  At least they understand that being polite is a good policy when breaking all the other rules.  It seems that some math students got all fractionated about the idea of cloned food demonstrating their serious need of some biology courses.  They didn't know how common cloning is among plants, and to teach them about the efficiency of asexual reproduction they are sentenced to weeding my strawberry bed, as soon as they learn about species, that is.   

Tree clones: immortality and sex

The oldest organisms on Earth are clonal organisms. Plants seem to have the capacity for immortality because they have perpetually juvenile tissues (meristems) capable of continued growth, and further, certain plant cells can dedifferentiate, return to a juvenile state, for wound repair and growth. This capacity is widely used in the vegetative reproduction of economically important plants. But can a clone live forever? Probably not, but they can be very old. The Pando clone of quaking aspen in Utah is estimated to be at least 80,000 years old, and some estimates place its age as 10 times older, which would make this clone as old as our whole species! Not only is Pando impressively old, it’s big covering over 40 hectares and at over 6000 tons is the largest organism alive. Now of course one problem with being an immobile species is that the longer you live the more likely you’ll encounter some environmental disaster, a fire, a flood, a volcanic eruption, a storm, a chain saw. But clones have a sex problem. Since they are all one genetic individual although looking like a whole forest, they cannot produce seed except by exchanging pollen with another individual, and when one individual occupies the whole area that becomes less likely. Even worse recent research suggests that as the clone gets older, it loses sexual vitality because of an accumulation of mutations. These show up in pollen because pollen only has one copy of each gene so if a harmful mutation occurs it may affect the viability of the pollen, a harm that does not affect the tree because in its tissues chromosomes and genes occur in pairs. By the relatively young age of 20,000 fertility can be diminished by more than 3/4s. So the clone may live a long time, but as it ages, its ability to sire offspring and start a new individual drops, but who knows Pando may already have lots of offspring.

Extinction is forever

A news article about the rarest tree on Earth caught my eye about a month ago, and since it is still living, it is worthy of some attention. Life is a process that generates genetic and biological diversity, and also destroys it. The ultimate fate of all species is extinction, but some species have a longer run than others and the Phactor has commented about the reigning king of longevity, the cinnamon fern, before. Many species are close to extinction, and human activities are way too commonly the cause.
A couple of rare trees provide some examples of how close to extinction you can get. Pennantia baylisiana is a species of tree that has consisted of a single individual at least for the past 65 years, which grows on one of the Three Kings Islands off the coast of New Zealand. Introduced herbivores in the form of goats may be the reason only one big tree remains, but it has a sex problem. Like many other plants, it cannot pollinate itself, so while you can make cuttings and root them, they are all genetically the same individual. But there may be an out; sex determination in plants is complicated, and occasionally a female produces some male flowers or flower parts and hand pollinations have yielded some seeds (and surely you understand that designations of male and female are totally inaccurate because the flowering plants with which we are familiar are the asexual spore-producing generation). With a bit of human assistance seedlings may be produced to help repopulate the island, however, they would all be siblings, so genetic diversity would be reduced, and this is a problem for any rare species.
Another contestant for the down-but-not-out extinction sweepstakes is the King’s Lomatia a tree that grows on the southern end of Tasmannia. About 500 trees exist, but this is a clone and again one genetic individual that has survived by asexual reproducing itself for 50,000 to 150,000 years. And because it has 3 sets of chromosomes, it may be the result of a hybridization that produced a sterile “mule” that has persisted by growing as a clone. Not much hope this species will “recover” unless it undergoes a spontaneous chromosome doubling to restore fertility. Although you may be unfamiliar with it, hybridization followed by polyploidy may be one of the most common types of speciation in plants.
Clearly both trees are in the running as the rarest organisms on Earth, each reduced to a single genetic individual.

Oldest known tree

I was feeling a bit meloncholy this morning and I could not exactly figure out why. Was it the end of a sometimes frustrating, sometimes exhilarating year, or the realization that the celestial cambium has added another growth ring, and we along with it are another year older. Was it because Janice Joplin was singing Me and Bobby McGee on the radio? And then quite by chance while looking for one thing (the world's first forest) I found another.

A Norway spruce (growing in Sweden) has been identified as the oldest tree on Earth. Growing at a high latitude this is not the towering giant you might expect; it barely tops 13 feet tall. This part of the tree is not that old, and you can't find a set of growth rings you can count, but the woody root stock has been carbon dated to nearly 10,000 years old. That means this tree took root just about the time the Pleistocene glaciers were pulling back and uncovering this area.

10,000 years makes this tree the oldest living individual organism on Earth. A very impressive record, and somehow knowing this has cheered me up. Although this spruce grows in a tough area, it's primary problem is winter and winds. At this latitude and in such a sparse community, the most common environmental mishaps that threaten big, old trees (lightening, fire) are relatively rare. So by growing slow and low, it has survived millenia.

It's quite likely some clones have lived longer, much longer, but it is the clone that survives, not the individual organism. Because they reproduce asexually, while genetically the same, the members of a clone are not the origninal organism at all, but copies, so the genotype persists not the individuals. Some unicellular organisms may form clones millions of years old, but at what point have enough random changes been accumulated in different copy lineages of the originial genotype that we would judge them different organisms? I have no idea.

There are aspen and sagebrush clones that are estimated to be around 10,000 years old, but no part of the original organism persists, just the genotype. So for now a Swedish Norway spruce holds the longevity record.