seed-grown reinwardtiana

[agustinfranco]

Hi Michael:

I was attempting to answer to your query when i was interrupted.
What i was trying to say is that regardless the numbers of chromosomes and polyploidy present in any plant, successive back crosses will ultimately lead to homozygotes for several genes which in turn makes the seed non viable than outcrossed specimens. It may not happen in F1 or F2 crosses, but F3's 4's etc.

Gus

[phissionkorps]

Again...not always. You can't say with certainty that it will indeed result in more homozygosity. A heterozygous population when backcrossed to either homozygous parent will be homozygous for the parental traits. This is of course, assuming that the first hybrid A x B is heterozygous for the trait of interest, one of the parents is homozygous for the trait of interest, the appearance of said trait is controlled by a single autosomal allele, and A x B is crossed back only to one of the parents, instead of using a different plant.

which in turn makes the seed non viable than outcrossed specimens

There's absolutely no proof or reason to think this happens in this genus, especially when you consider that there are absolutely no postzygotic mechanisms to prevent hybridization.

[agustinfranco]

It's easy to deny a hypothesis, but can you actually provide one?

esa.confex.com/esa/2003/techprogram/paper_11682.htm

This is just one, and i have more. Regarding postzygotic mechanisms, there must be in present in nepenthes too, but it's faulty. as the viable seed from some hybrid crosses is very small percentage wise while others is non existent or excessively existent!.

[phissionkorps]

That paper (or I guess abstract rather) just says one kind of insect does better on inbred plants, and one does better on outbred plants. What's the point? I mean the paper is about insect feeding strategy, not the issue we are discussing, which is how quickly homozygosity will accrue in a population.

The only insinuation of postzygotic mechanisms I've found in Nepenthes is with one certain cross....and I honestly can't remember what it was. I want to say spathulata x ventricosa, but that can't be right, since there are a ton of Indah running around, and at least a couple other clones of the same cross (from different grexes, on different continents). Either way, EP proposed that these 2 plants couldn't hybridize, since they had tried it about 5 times and it had failed every time. However, a grower from Japan posted a pic of rather healthy and large plant on pitcherplants, and in the following couple weeks I saw a few more pictures of the same cross. Obviously that case doesn't count then, and I haven't seen another that seemed even half as strong.

When you try to cross 2 plants and fail, that doesn't automatically mean there is a mechanism against it. Remember that neo seed that went around a while back? Ripe, healthy looking seed pods contained infertile seed from a neo x neo cross. Surely neo doesn't have a mechanism against itself. I know someone here who has tried to make boschiana seed a couple of times and failed. That doesn't mean boschiana has a mechanism against itself either, only that he need to pollinate 2 or 3 times a day over the course of a couple days.

Diminished amount of embryo production is also not an appropriate thing to label as a post-zygotic mechanism against hybridization. Maybe in Nepenthes female plants are more costly to produce (this is almost always the case for all life), and maybe the seed of certain crosses just happens to be 90% or more female? Therefore, it would take more energy, and the plant would produce less seed. Maybe the pollen used was old, improperly stored, etc? It's a stretch of the imagination to say that decreased seed production in Nepenthes can be labeled a post-zygotic mechanism unless you do the same exact cross with different plants multiple times, count every single seed produced, sow them, count germination and damp-off rate, grow them out to maturity, and record the gender of all of them.

[agustinfranco]

My guess is that you are throwing too many "MAYBES" without evidence. The fact is that inbred plants are more susceptible to insect attacks and there is also a paper where it shows that seed viability in general is decreased. The situation in the wild is the following: you almost always find plant populations belonging to a couple of species without any hybrids between the two. In other cases, yes you find a couple of hybrids around between the two.

Therefore, there must be mechanisms for species preservation in place. Whether there are postzygotic or due to environmental pressure ie, the presence of specific insects attracted to the flowers at specific times of the year, sure, but one can't deny that if there is no control for hybrid production in the wild, then we must be flooded with natural hybrids. My question to you is: well Where are they ?

Gus

[phissionkorps]

The reason I throw the "maybes" out there, is that to me, you seem convinced of certain scenarios/situations, which are not always true, and have little or no backing in their application to these discussions.

The fact is that inbred plants are more susceptible to insect attacks and there is also a paper where it shows that seed viability in general is decreased

Show me a paper that proves that hybrid NEPENTHES seed viability is decreased. If you find one about sunflowers, or cotton, or beans...that doesn't prove anything in this regard. What is generally true is not always true, and what is true for Asteraceae...well, you get the point. We can't go running around comparing Magnoliids to Rosids I, or monocots to dicots...as they say, "apples to oranges" so to speak. And again, show me a paper that says inbred NEPENTHES are more susceptible to being destroyed by insects. Surely, you can't think that hybrids would flourish in the wild, but insects destroy almost all of them except the what....78 or so natural hybrids that exist??? If you read the paper/abstract, you'd see that it says, and I quote:

We found that both specialist tortoise beetles and generalist armyworms performed better when reared on outbred plants, but that aphid density increased significantly faster on inbred plants

But wait...you said that its a "fact" that inbred plants are more susceptible to insect attack. So who's wrong...you, or your source?

The situation in the wild is the following: you almost always find plant populations belonging to a couple of species without any hybrids between the two. In other cases, yes you find a couple of hybrids around between the two.

And, you also find hybrid populations (which are sometimes standalone). There are many, many hookeriana populations, kuchingensis, trichocarpa, etc.

but one can't deny that if there is no control for hybrid production in the wild

I never said there is NO control, just no obvious (or anywhere near effectual) post-zygotic control. We're not flooded with natural hybrids because, mainly, not too many species are found sympatrically (a species alone, or with one, maybe 2 other species, rarely more), and they flower at different times of the year. IIRC, amp flowers in January in the wild. If it was located sympatrically with 40 other species that all flowered from March to November, well then we probably wouldn't see many, if any, natural hybrids. I've researched enough pollination ecology/syndromes to say with some certainty that every Nepenthes isn't going to have a relationship with only a single pollinator, which is exclusive to it. Some may have a few (2 or 3) different ones, but that's as far as thats going to go. The structure of the flowers automatically rules out birds, most species don't flower close to the ground, which rules out beetles (for most species), the flowers aren't bright white, which rules out moths, and they don't smell like a turd, so it can't be flies either. Since they're also not sexually deceptive, the most likely effective pollinator of most, if not all species are female Hymenoptera.

[agustinfranco]

why don't you show me a paper where nepenthes seed viability remains the same or increased? you asked for too many proofs. I showed you a paper, you just showed me your thoughts!. I know that under artificial conditions, depending on the species used and the type of hybrids produced the amount of seed per cross varies a lot and that is using a controlled environment. I have done a couple of crosses myself with 6-8 hybrids and the amount of viable seed varied from maxima X sanguinea being the most fertile to (fusca) X (spectabilis X aristo) being the most infertile. By the way the spectabilis X aristo cross performed better with thorelli X aristo than with fusca. I had 5 times the number of seedlings in the latter than the former. Nothing went wrong. It's just that there are unknown mechanisms that will not allowed such a massive production of seed in some cases as opposed to getting a thousand or more viable seed. If you ask EP how they priced their plants, they'll tell you that the price is based on the number of viable seedlings available per cross. If you expect to get thousands o seedlings every time you make a cross, that simply is not going to happen.

With regards to the neo Xneo cross that will never germinate. How sure are you that the seed was viable to begin with?. whether the person got it from one plant or 20 plants?. If he/she got it from one plant..then how could you expect to prove a point based on one female plant?

With 130 or so species, why you have to mention the well known hybrids: how about
spectabilis X lavicola or rafflesiana X hirsutas etc. I am not denying the fact that there are natural hybrids around, but let's generalize a bit more and as i noted some time ago, don't use the exceptions but the general findings instead.

Hybridization in nepenthes has been misconceived as a free for all event, but we should ask ourselves how many viable seedlings we get per cross. Lets' not forget that we have hybrid vigour displaying in some hybrids and not in others and that's what differentiates between hybrid of some species and not in others

Gus

[phissionkorps]

Nep seed viability won't stay the same or increase, that's just the nature of the genus. Regardless what hybrid is made, what species seed is produced, etc....it's just not going to happen.

Interesting that you had more success with thorelii x aristo. My thorelii x aristo had pollen
problems (as in...barely made any).

I don't know how many plants the neo seed came from, but I'm almost certain from more than one. The person that collected them was in a neo population, and the seed pods didn't look like anything was wrong with them. Just something to note: most neo seed from what I understand is destroyed before dehiscence (caterpillar or something or other).

how about
spectabilis X lavicola or rafflesiana X hirsutas etc.

What about them? So there aren't that many, but that could be due to any number of factors. The most likely is that the species flower at different times of the year. Second most likely, is that there may be relatively low numbers of lavicola in spectabilis habitat, etc. I would find it much less believable that they readily hybridize at least semi-frequently, and some sort of post-zygotic mechanism is in place, and that powerful. I'm not discounting it entirely, as it's certianly possible, just not very probable IMO.

I see it as sort of a free for all, in the sense that, at the present time, there are no know species that absolutely will not produce viable seed. Again, I'll refer to the fact that some crosses may result in mostly more costly female offspring, leading the plant to produce less seed. Until someone dedicates a couple decades to finding out, we're not going to know for sure.

Can you give me an example of a hybrid that is less vigorous/harder to care for than either of the parents? That's a starting point, but I'd be more impressed with an example of one that is harder to grow than both parents. Muluensis x lowii is easier than both parents, izumiae x truncata is easier than both parents, etc.

[agustinfranco]

sure: veitchii X hurrelliana, being a hybrid is a pain in the &^%$%^ to grow it. I don't know about hurrelliana but veitchii is sure easy to grow. bellii X sibuyanensis is not an easy to grow hybrid either. The proof relies on the countless posts by experienced growers like TonyC and others who complain about them. On the other hand, we have weeds like most maxima hybrids, thorelli X aristo, X Ventrata, and ventricosa X talangensis that i'd bet you they'll grow in the desert if planted there.

Gus

[phissionkorps]

FWIW, I found sibuyanensis easier than bellii. Perhaps a product of my conditions (I've had two different bellii). I've never grown hurrellliana either, but veitchii for me has been ultra-slow, but steady. I haven't grown either of the hybrids you mentioned either, so I can't comment on their difficulty.

My thorelii x aristo was about the easiest plant I had. It flowered about 4 consecutive times, never produced pollen, and now is about to die. It started going black after the 4th spike, so I made an emergency cutting which doesn't look like it has any inclination to root.

i'd bet you they'll grow in the desert if planted there.

Unfortunately, even ventrata has been killed off by the wasteland style conditions of my part of the world.

[agustinfranco]

If you like weed like plants. ventricosa X talangensis will not disappoint you. Another one i'd highly recommend is X Wrigleyana. This plant is as you may know a combination of 3 lowlands: mirabilis, rafflesiana, and ampullaria but it pitchers all year round: in cold weather down to 7-8 C and of course in summer as long as they are exposed to fair amounts of light.

I also find spectabilis X spathulata very robust. It does not grow as fast as thorelli X aristo, but it does well all year round in Oz.