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Post by unclemasa on Aug 20, 2008 20:21:17 GMT -10
Assuming some basic premises of Darwinian evolution it if reasonable to suggest that all present day species of Nepenthes are descended from some (one or more) ancestral populations or founding members of Nepenthaceae.
Which are the older and which are the relatively newer species?
I have a few ideas here and would, for your entertainment, suggest that N. mirabilis and N. truncata are relatively old species. I won't tell you my reasons for suggesting this just now as I would like to hear what any of you brave enough to speculate have to say first.
Dave (Evans) ... In a recent post on pitcherplants.com you seem to suggest that you believe N. albomarginata to be a relatively old species because of its apparent dominance in hybrid combinations. Am i correct? Would you care to go further out on a limb with this?
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Dave Evans
Nobiles
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Posts: 490
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Post by Dave Evans on Aug 21, 2008 12:05:18 GMT -10
Yes, I think so. It has a fairly wide, but extremely patchy distribution. The same can be said of _N. campanulata_. This pattern seems to indicate to me, that the species spread out long ago and have been present where you now see them for a long, long time and do not represent a more recent dispersal.
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Post by unclemasa on Aug 28, 2008 0:59:23 GMT -10
In the future, genetic analysis will clear up many of the mysteries of Nepenthes evolution. In the mean time, I can think of only about a half dozen criteria that might be used as possible indicators of the relative ages of the many different species of Nepenthes.
1. Wide or diverse distribution:
It seem like a reasonable avenue of thought to suggest that species that enjoy a wide geographic distribution might be older than species with a very limited range. The simple assumption being that gaining wide geographic distribution is a factor of time. The longer a species has been around the longer it has had to adapt and the greater the chance to colonize larger and more distant areas.
Obviously, this assumption is not a sufficient indicator in and of itself. There are certainly many factors involved when a species is able to colonize large and diverse areas of distribution. Still, taken in conjunction with other possible indicators, a wide geographic distribution might be an indicator of the relative age of the species. This sort of argument is often coupled with appeals to continental drift evidence.
suggested species : mirabilis, rafflessiana, ampullaria, gracillis
2. Hybrid dominance:
In nature and certainly in the nursery Nepenthes hybrids have show us that some species appear to contain genetic elements ( .. relating to morphological characteristics) that are fairly consistent and seem to dominate in combination with other species. The assumption required here, in order for this to be considered a possible indication of genetic age, is that older genomes are composed of elements that, over time, have become fixed and are consistent and dominant in expression when cast in combination with those of younger or newer species.
Again, this is a very problematic assumption and based solely upon similarities in plant morphology. It is clearly true that at the heart of any genome there are fixed and dominant elements that make a creature what it is. Crossing two genetically diverse species may result in the production of plants with diverse morphological features but there are genetic elements that will and must find expression every time. Pitchers may be big or small but all Nepenthes will leaves and roots. The genetic combinations that produces a plant with leaves and roots are prerequisites of Nepenthaceae. The real question is "can we consider the morphological features of the plant (.. in particular, the pitcher) as possible indicators of the relative age of the species?"
The answer to the above question would appear to be "Yes" and, in fact, this reasoning often used, in regard to Nepenthes flowers and seed pods, to suggest that some species are older than others.
suggested species:
.... khasiana, pervillei, madagascarensis, etc. for their reproductive structures
.... and mirabilis, albomarginata, veitchii, talangensis, etc. because of their dominance in hybrid combinations
3. species variation:
Another, certainly speculative, possible avenue of inferring genetic age might be species variations. A large group of obviously related forms or variants in a single species might be considered to suggest a longer period of adaptation and thus a more distant age of origin. The assumption is the same as in the first of our possible indicators: that successful and diverse adaptation is a function of time. The longer a species has been around the longer it has had to produce variation.
Like the "Wide or diverse distribution" criteria the "species variation criteria" makes many assumptions and could hardly be considered a sufficient criteria on its own. But, also like the "diverse distribution" criteria it could conceivably be used in combination with other criteria to bolster and argument that one species is older than another.
suggested species: N. rafflesiana, mirabilis
4. Seedling ontogeny
“Ontogony” refers to the process’ of transformation undergone between the stages of conception to the development of an organisms in it’s final physical form. All animals undergo a morphogenesis wherein their physical structures are configured and reconfigured before reaching a final definitive form. Unlike animals plants to not resolve themselves to one final and definitive form but continue to grow and fill space according to environmental factors. Plants of the family Nepenthaceae in particular, reconfigure themselves several times over their life span: from seed to plantlet, to adolescent rosette, to vine and to flower.
Over recent years while in the process of raising up hybrid seedlings I have noticed on multiple occasions a most interesting phenomenon. So unusual to my thinking was what I witnessed that I began to doubt my own observations until fairly recently, when in a conversation with another breeder, I discovered that I had not been the only one to witness such developmental events.
I have not made record of these events in any systematic way as I was rather doubtful of my own observations but I have observed very young seedling, with no obvious truncata heritage, pass through a stage where they made, for a short period of time, leaves having a very distinctive truncata shape. In other circumstances I have seen seedlings, with no obvious mirabilis heritage, pass through a stage of development wherein they displayed very distinctive mirabilis-like leaves and tendrils only to have these characteristics disappear in later stages of development.
The obvious question here is “might these developmental stages in such examples be indicators of the genetic age of species like truncata and mirabilis as compared to other species?” Could these be examples of seedling ontogeny recapitulating adult phylogeny?
suggested species: N. truncata, mirabilis and perhaps rafflesiana.
5. Archaic traits
There are a few traits to be found in Nepenthes that would seem to be suggestive of a distant origin. The winged tendrils of N. mirabilis and some forms of N. rafflesiana are perhaps one such indicator. Plants that do not vine or that lack upper pitchers might also suggest a primitive origin.
As with our previously suggested criteria the assumptions are wholesale: that a clearly defined tendril and highly developed vines and upper pitchers are relatively recent adaptation of the family of plants.
suggested plants: mirabilis, rafflesiana and perhaps campanulata and ampullaria.
It is interesting that, as problematic and speculative as these criteria are, they would all seem to suggest certain lowland species like mirabilis, rafflesiana, truncata, ampullaria, gracillis, albomarginata and campanulata as being of more distant relative age.
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Post by sockhom on Aug 28, 2008 1:56:58 GMT -10
Hello Sam . What's "prevelii"? I would include N. clipeata in the group with archaic traits. Can't we also imagine that isolated species such as N. masoalensis, madagascariensis, pervillei, distillatoria, khasiana, vieillardii and maybe the papuan species are old species? We could even wonder, in that case if the paniculate inflorescence is a sign of an ancient species (Should we add N. bicalcarata? N. ampullaria?). François.
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Post by unclemasa on Aug 28, 2008 8:11:41 GMT -10
Hi François,
Damn! .... there were a lot of grammatical and spelling errors in the above post. I guess I should have gone to bed earlier.
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Post by sockhom on Aug 28, 2008 11:11:38 GMT -10
Hi Sam. I'm sorry, I didn't mean to point out any spelling errors. It didn't even scratch my mind that "prevelii" was pervillei. I guess I was tired too ;D. By the way, I mentioned isolated species... All of them look plain and didn't have to develop special features in order to struggle in competition like the species from Borneo or Sumatra. That's why I think they might be older. François.
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Post by unclemasa on Aug 28, 2008 12:42:46 GMT -10
N. clipeata is probably an older species. I'm not sure if the different tendril attachment is a primitive feature or not. It is definitely different.
The other "western" species you mention are also probably older than most species or, perhaps, just a different branch on the family tree. The differences in inflorescence structure is pretty dramatic.
I am a little confused about the idea of competition among the various species. Now, if we were talking about large cats that share a territory then, the idea of them being in competition makes some sense. On the other hand, I think plants struggle with their environments but the concept of competition between species of the same family seems rather strained to me. One species might be more successful than another without the idea that they are in competition. I see no reason why a suitable environment could not or would not support tens or even a hundred species of Nepenthes side by side. I tend to think that plants are oblivious to their neighbors and that there are plenty of insects to go around. Again, I am uncomfortable with the use of motivational language in discussions of evolution.
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Dave Evans
Nobiles
dpevans_at_rci.rutgers.edu
Posts: 490
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Post by Dave Evans on Aug 28, 2008 13:40:19 GMT -10
Hi guys,
I do not agree with the theory about the western species being "plain" because they are older, nor do I think it indicates the presence of other species caused a competition for food which resulted in the Bornean and Sumatran plants becoming more different from each other and display a greater number of differences.
First, insects are extremely plentiful. What competition could there be for prey? There are generally way more insects visiting the plants than ever get eaten. I think "competition" or rather success through ecological fitness within some of the species resulted in the extreme morphology some species display on Borneo and Sumatra--not species competing against each other.
To understand the western species, I think we need to know more about the previous/ancient geography of the region. Where Nepenthes simply much more widespread in the past and the more recent ice ages the reason for their compaction in Sunda Land? Or are the western species the result of long range dispersal directly out from Sunda and Nepenthes have only and ever been native directly to the area centered by Borneo?
Where was Madagascar several million years ago? Can we even tell with any certainty? Clearly, the Indian continent slid north into Asia, perhaps it picked up several species when it was directly west of Sumatra and most have since died out, leaving only N. khasiana in one small and protected pocket saved from temperate conditions during ice ages somehow?
Old species: N. albomarginata and N. campanulata, I infer this mostly from their patchy distributions. They are so old, they appear to be dieing out. N. lowii and it sister N. ephippeata (probably a subspecies of N. lowii) would be an old one too.
N. maxima, I include N. fusca into it. Wide distribution and it also has many close relatives. Clearly, this line of species is old and very successful. Present on Borneo, Sulawesi, New Guinea, the Moluccas and the Philippines, I think this indicates there were several radiations from within this group, the older ones have already become separate species on Borneo and are members of the N. maxima group.
N. rafflesiana, N. gracilis and N. ampullaria for reasons Sam mentions above.
N. mirabilis--a new species or an old one with a very recently expansion of its territory. If it was truly old and has been widespread for a long time, it would look more like N. maxima or N. rafflesiana with regards to having many sister species and having a lot more diversity of forms. For its wide range, it shows very little in the way of diversity. I think N. echinostoma and N. tenax (maybe N. rowanea too) could be older versions of it, not recent derivatives.
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Post by unclemasa on Aug 28, 2008 14:29:47 GMT -10
Hey Dave,
First, I want to thank you for your willingness to go out on a limb and speculate freely. I appreciate those who will benefit us with their imaginations as well as the facts they have memorized.
I am a little puzzled by what you mean when you say "patchy distribution". In the above post the suggestion was that a wide range might indicate a relatively old age. If, limited distribution is taken as an indicator of age then, things are reversed. I assume that you are suggesting that campanulata and albomarginata once had a much wider range of distribution and are now failing. (?)
N. maxima seems like a tricky one to me. It does seem to have a good number of forms and show some dominance in hybrid combinations but still only a modest range ( ... even when we include fusca). I guess it depends on what you consider to belong to the "maxima group".
N. maxima relatives in the Philippines? I'd like to hear more.
I think if I had to pick one species ( .... at least among the non-western species) as definitely old I would put my money on N. mirabilis.
Why? Although species variability might be an indicator of relative age it is certainly not necessarily so. If, it is working very well in so many environments, as N. mirabillis seem to then, no need to fancy it up. Besides, depending upon what you include in mirabilis, it could be considered one of the most variable.
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Dave Evans
Nobiles
dpevans_at_rci.rutgers.edu
Posts: 490
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Post by Dave Evans on Aug 28, 2008 21:05:23 GMT -10
Dear Masa, Well, things which have been lumped in with N. mirabilis have been getting removed from it too And most everyone seems to be in agreement with these changes. N. echinostoma was reduced to a variety of N. mirabilis but this doesn't seem correct to me. Varieties and forms occur mixed within populations of the "standard" varieties or forms. For example: Sarracenia purpurea purpurea forma heterophylla. N. echinostoma has its own range and it has been reported that it doesn't occur in mixed populations with the normal variety. If this is true, this is a classic example of a subspecies. Why? Although species variability might be an indicator of relative age it is certainly not necessarily so. If, it is working very well in so many environments, as N. mirabillis seem to then, no need to fancy it up. Besides, depending upon what you include in mirabilis, it could be considered one of the most variable. Well, I have yet to see it. I have heard this many times, but all the N. mirabilis I have seen looked very similar to me. The issue with N. mirabilis is also one relating to time, if it has been widespread for a long time; the same processes at work on the other species changing them should also apply to N. mirabilis. I suspect that plants like N. rowanae, N. tenax and possibly N. sp. Phang Nga islands and N. echinostoma would represent relics of a previous expansion of proto- N. mirabilis which then died out in most places only for its range to re-expand sometime more recently. Taken all together, it could be an older group of taxons, like with the N. maxima group. Yes, that does seem to be the case, not necessarily a larger distribution, but higher density within their respective ranges. This has to be the case, is there any other way to explain how they reached the areas where they are found without spreading to them? But now there are huge holes in those ranges where they are no longer found or at least haven't been located yet. What once were actively spreading species no longer are spreading and appear to be dying out from areas where they used to be successful. To much environmental change they cannot keep up with? Don't forget N. reinwardtiana, seems likely to be more recent, as it doesn't seem to show much diversity. I generally think this means it has recently achieved its current range, but doesn't necessarily mean it is a young species--it may have just become more successful of late.
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Dave Evans
Nobiles
dpevans_at_rci.rutgers.edu
Posts: 490
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Post by Dave Evans on Aug 28, 2008 21:30:17 GMT -10
Does anyone have photos or grow plants of N. mirabilis from China? Here is something I found which might explain a lot: www.scotese.com/indianim.htmIt would appear Nepenthes started on or west of the Indian content and jumped eastward as it slid northward, there doesn't seem to be a better explanation for their presence on Madagascar and the islands northeast of it. The western species have very restricted ranges and probably do represent left behind remnants from about 100 - 90 million years ago... I wonder what changes occurred on India as it slid northward at a very quick pace... Maybe this rapid movement and the environmental changes that must have happened helped encourage Nepenthes to diversify. And they only very recently arrived in Australia-- N. rowanae, N. tenax and then the slightly newer N. mirabilis--as it is also sliding northward, but at a much slower pace.
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Post by sockhom on Aug 28, 2008 22:42:43 GMT -10
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Post by stevestewart on Aug 29, 2008 2:55:38 GMT -10
Fun speculations! I think the distribution and presence or lack thereof, of Nepenthes species, has not only been by continental drift, but by even relatively recent events such as Super Volcanoes. One such event could easily wipe out large populations of many species and distribute the seeds of others far distances from where they began their evolutionary modifications. The center of current Nepenthes populations is very volatile, the place they actually began may have been destroyed long ago. Just food for the imagination, for fun Coevolutionary changes may be very recent in some Nepenthes species and very ancient in others. I personally think N. mirabilis is a primitive form. Take care, Steven Stewart
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Post by unclemasa on Aug 29, 2008 9:04:44 GMT -10
I've seen these maps before and if, we assume that the progressions represented in this map are linear then, each step represents about 11 million years.
If, we also assume that Nepenthes originated in the West then, the first chance for their spread to the Sunda regions takes place about 33 mya. It was also at this time that India and Borneo were as close to each other as they have ever been but even at that time there was no (and never has been ... according to this map) a land bridge between the two.
Also, it would seem that the closest that the Philippines (which seem to rise out of the ocean at about 55 mya) has ever been to the Sunda region is at a time when Nepenthes could not have even made it to the Sundas yet.
Steven .....
Postulating the spread of Nepenthes via super volcanic events ( .. or even giant storms) would seem at least as reasonable as their having traveled via land bridges. Nepenthes seeds are very light and I can imagine seed material blown high into the atmosphere along with ash and then finding its way to other regions ...... but it is a reach.
As for Nepenthes in Australia ..... maybe only 11 mya. (?)
It is know that some seeds reach new locations via the digestive tracts of birds and other critters but I have never heard of birds (.. or anything else) eating Nepenthes seeds. (?)
We need more data from genetic analysis!
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Post by rsivertsen on Aug 29, 2008 9:42:23 GMT -10
Postulating the spread of Nepenthes via super volcanic events ( .. or even giant storms) would seem at least as reasonable as their having traveled via land bridges. Nepenthes seeds are very light and I can imagine seed material blown high into the atmosphere along with ash and then finding its way to other regions ...... but it is a reach. I had some interesting conversations with John Turnbulll about Nepenthes seed distribution, and he mentioned that a lot of racemes he observed in the wild seemed to be infested with some larvae of some moth, or something, which would feed on the Nepenthes seed. Birds would often forage for these "worms" attempting to land on the flimsy stalks, and get their beaks and feet loaded with seed, and fly back up to a mossy post high up in the trees and feed on these larvae at their leisure; which helps explain how these plants find their way up into the canopy, instead of the forest floor. Imagine some birds getting windswept into some massive storm, or other natural event,with its feet loaded with Nepenthes seed! Have you ever noticed what happens when you touch Nepenthes seed with a wet to damp finger? It's curious that after all these years, not much study has been done on Nepenthes seed distribution, or pollination vectors. I might add here that seedling fatality must play a significant role in shaping the evolution of this genus, with each locale having different selection factors. - Rich
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