|
Post by marka on Jul 16, 2009 13:35:11 GMT -10
I'm not so in agreement that seeds were dispersed by a bird's feet. The chances for a host of species to migrate and establish themselves when a male and female are needed to make seeds and perpetuate the species. I am still of the belief that nepenthes were already in place and not moved great distances/ Why would a nepenthes end up on a coral atoll unless it was there to begin with. Traveling to far reaching destinations only makes sense if seeds had a sticky gummy attachment mechanism. If seeds had burrs or appendages that made them stick to feathers, this would be more if a traveling advantage than just small dusty seeds attaching themselves to a bird's feet. Our native Bidens that most species have appendages for sticking to feathers have lost this attachment in natural evolutionary trends. I don't believe seeds would have a mechanism for travel since almost all nepenthes seeds are uniform in appearance and shortly dispersed. I do believe that nepenthes had to develop whether they could adapt to highland or lowland conditions. If we're led to believe that seed dispersal by birds is possible, then we should also consider the notion that highland species have traveled to lowland conditions and vice verse. As many bird species migrate from cooler temperate regions to warmer tropical ones. For seed dispersal to allow travel from one climatic condition to another, this seems a bit far fetched. M I cant agree with your logic, many species have established themselves on isolated islands by the chance relocation of individual male and female individuals, its doesn't have to happen very often, you just need two unlikely events to occur at the same time, which by the law of probability will happen, sooner or later. Note that i suggested dispersal by waterfowl for the case of Mirabilis only. I don't understand what point you are making about different climatic zones and birds, what I am suggesting is that Mirabilis possibly has a unique dispersal mechanism which accounts for its wide distribution. Or how else do you explain the dispersal,when as you say most seeds dont go very far. They could not have evolved over such a wide area at the same time, without evolving into separate species unless the seeds is dispersed over wide areas quite regularly, or its a very young species with efficient seed dispersal. I don't believe it can be an older species as it doesn't fit the usual habitat requirements of the vast majority of nepenthes species, and would have speciated more than it has.
|
|
|
Post by leilani on Jul 17, 2009 0:47:35 GMT -10
Tanks for bringing this thread back to life marka. Your post forced me to read it all again. I have a few comments on some of the posts ....
*(Dave Evans)
This is an interesting inference:
Some species survive longer than others but all species end in extinction. The reasoning would be that the longer a species has been around the closer it is to extinction. This is, mathematically, true. The trouble is that the reverse inference, that the closer a species is to extinction the older it must be, is clearly false.
*(Dave Evans) Does diversity of form suggest relative age?
This is the “species variation criteria” I mentioned at the start of this thread, i.e., that the longer a species has been in existence the longer it has had to produce greater variation or specialization.
Much like the previous suggestion the inference is trivially true as stated but false in the other direction. Although, we can say that variation is a factor of time ( ... again, trivially true), we cannot say that greater relative time necessitates greater variation. Some species may evolve and diversify relatively quickly while others may change very little over vast numbers of years. The causes of “varietal diversification” and “ecological specialization” must be manifold and, certainly require some increment of time but “more time” or “longer periods of time” does not necessarily imply greater diversification (or distribution).
*(rainforest) Fluid viscosity as an evolutionary advancement
This is an interesting thought. I wonder how much the viscosity is controlled by the plant itself and how much by infauna and environmental factors?
*(rainforest)
To “find new ground for prey”. I think I tend to underestimate the agressiveness of these plants in regard to their “persuit” of prey. Nepenthes traps seem so passive that its easy to forget that they are no less active than other cps in their efforts to kill.
*(rainforest)
Another interesting suggestion. But does greater variation, specialization and adaptation really imply greater relative age?
*(rainforest)
I like your suggestions regarding the functional advantages of a ventricose pitcher structure.
*(marka)
This sound like like it should be true but, as I have mentioned before, I have some trouble with the competition metaphor when talking about two species of Nepenthes sharing a territory. I also have a problem with the phrase “specialized” with reference to the various pitcher forms. Other than a suggested preference (?) by N. albomarginata for termites I can think of no Nepenthes that “specializes” in any particular prey. There is great variation in pitcher morphology but, other than the suggestion that ground pitchers attract crawlers and upper pitcher attract fliers, I find it hard to think of these morphological variations as “specializations”.
*(marka)
It seem to me that you are using “specialized” and “highly evolved” to mean the same thing. In which case, it would be self-evident. Again, it seems to me that it takes time for a plant to develope variations, adaptation or specializations but that this tells us nothing about its age relative to a more stable form. Time certainly necessitates change but knowing this is insufficient to speculation about relative degrees of change.
*(marka)
This could go a long way toward explaining the wide distribution of N. mirabilis. On the other hand, I am not sure how this suggests N. mirabilis to be a newer species. Surely, there have always been rivers and waterways.
*(marka)
|
|
|
Post by marka on Jul 17, 2009 8:32:26 GMT -10
The majority of Nepenthes won't and cant grow in similar conditions as Mirabilis, even species that can grow in wet soils in nature, ampullaria, gracilis etc quickly expire if the soil is really kept waterlogged. Mirabilis is possibly unique in tolerating and even growing with anaerobic conditions at the roots, at least far longer than any other nepenthes species.
Maybe Bicals can do this as well i'm not sure, or possibly Madagsacariensis, although they seem to do better if the soil is not permanently wet. Even so, Mirabilis is on the extreme end of this evolutionary path compared to other nepenthes, suggesting the possibility that it is more recent.
If the populations in southern china and northern Australia were very old, you would perhaps expect to see a wider range of variations, or even that they had become distinct species, this maybe happening but not so much as you might expect for a very old plant.
It all depends on what you think the original proto-nepenthes plant's typical growing conditions were like. Of course it could have been a swamp dweller and all the cliff face dwelling species evolved from that, but in my mind at least it seems less likely.
|
|
|
Post by leilani on Jul 17, 2009 10:00:35 GMT -10
Good morning marka!
*(marka)
Although what you suggest would seem to be true I am not satisfied that this premise supports the conclusion. First of all, although most Nepenthes don’t like waterlogged conditions their tolerance of such conditions is pretty good. (I once grew a N. ventrata in nothing but water for almost two years before it expired.)
Granted that N. mirabilis is more tolerant of wet conditions than most Nepenthes species I don’t see this as offering much support to the conclusion that it is a newer species. A similar argument could be designed for N. villosa. N. villosa grows under much colder conditions than most Nepenthes will tolerate. Does that imply that it is a newer (or older) species?
There might even be an argument that goes something like this:
Life and evolution love water. That all life forms spring from wet environments and that drought tolerance is an advanced evolutionary development. This premise might be used to suggest the opposite of your conclusion, i.e., that warm tolerant species must have evolved first.
I tend to think of N. mirabilis as an older species for the following reasons:
It is possibly suggested by most of the criteria I listed at the beginning of this thread .... "Wide and diverse distribution", "hybrid dominance", "species variation", "seedling ontogeny" and the presence of "archaic traits".
To this we might add the following possible criteria: "water and heat tolerance". The argument would go something like that suggested above. Namely, that life and diversity arise most often in warm and wet conditions and that, therefore, those species best adapted to these condition are somehow closer to ancestral plants than those that have evolved to tolerate dry and cold environments. Why not?
|
|
|
Post by marka on Jul 17, 2009 11:02:33 GMT -10
I agree your arguments are valid, however my own view would be that Nepenthes evolved in a niche habitat, probably wet hill sides / cliff faces, where nutrients are poor, with the combined ability to catch prey and hold water in times of short drought, they have advantages over other plants. Mirabilis may well be in the process of devolving to utilise less niche habitats and gaining wider distribution as a result.
I know what your saying about cuttings in water, but if the water is kept relatively fresh and free of organic matter its probably not anaerobic.
"It is possibly suggested by most of the criteria I listed at the beginning of this thread .... "Wide and diverse distribution", "hybrid dominance", "species variation", "seedling ontogeny" and the presence of "archaic traits". "
Grasses are new species by and large and have very wide distribution. Species variation can be due to rapid evolution in a new species (look at humans), and who defines what an archaic trait is?
Mirabilis may even be more primitive than other nepenthes but still a new species, depending on what it evolved from.
|
|
|
Post by rainforest on Jul 24, 2009 13:03:21 GMT -10
First of all, I do not believe that grasses are a newer plant form in evolution. The simplicity of a chance pollination would never work unless the species was well established in communities so timed flowering or wind pollination could occur.
I still believe that mirabilis is perhaps the oldest species of nepenthes and has survived in the many regions it occupies. This species has many many variations leading me to believe that this species had several million years to think about what prey it wants to capture, where they want to occupy and what form they will take up. N. rowanae, sp. Viking, ssp echinostoma, et al are all forms of mirabilis. A new species just doesn't take these advanced forms from being the first one on the block. They had an experience of time to commit themselves to what they were evolved to. It's odd that N. mirabilis hasn't traveled and become a highland evolutionary form. Birds do fly highland and many water fowl also migrate between temperate and tropical climates, yet we do not see any unusual forms of mirabilis growing with rajah or other successful highland species. N. mirabilis would have had to be in place on each respective island prior to Pangea breaking up and spreading. This may sound a bit far fetched but nepenthes do show primitive flowering mechanism of dioeciousness and yet specialized in creating nectar rewards with attractive evolved leaves-pitchers. m
|
|
Dave Evans
Nobiles
dpevans_at_rci.rutgers.edu
Posts: 490
|
Post by Dave Evans on Jul 24, 2009 16:22:23 GMT -10
I believe N. mirabilis to be one of the newest species, because it is wide spread. Species tend to follow trends in distribution with new ones reaching far and wide and then later speciating. The species which appear to be directly related to N. mirabilis, like N. tenax are not directly related to mirabilis, but did evolve from the same parent species N. mirabilis did. I have seen many remarks about how it appears this species or that species has recently come out of N. mirabilis, I really doubt these scenarios.
This seems much more likely to me: proto-mirabilis spread far and wide. Something changed and it then broke up into several species and most of these became fairly isolated, many dieing out. Then N. mirabilis evolved and started spreading, probably when sea levels were very low at the height of one of the last ice ages and managed to reach as far and wide, perhaps even further than proto-mirabilis did. If N. mirabilis were older as compared to other Nepenthes, it would be more like N. maxima or N. rafflesiana with a seemly endless supply of diversity.
You can think of species spreading in similar fashion to how ripples spread out when you drop rocks into smooth water. Of course the topography Nepenthes are dealing with is much more complicated than the smooth surface of calm water, but general concept is valid.
The wave moves outward and things it encounters in the water can slightly modify the wave as it moves, but one portion of the wave can still be identified as being a part of the whole wave. N. tenax and N. rowanae are remnants of previous waves and N. mirabilis is the new wave and it currently appears to have reached the edge of the lake, so-to-speak. Now I think it will break up with different populations becoming more specialized just like N. maxima already has.
|
|
|
Post by rainforest on Jul 24, 2009 16:47:32 GMT -10
The same ripple wave example can be said about N. mirabilis as it specializes (i.e. N. sp. Viking, N. rowanae, N. m v. echinostoma, etc.) as each has specialized in their respective region (as would your example of N. maxima and rafflesiana). I would say that N. maxima and rafflesiana are newer species since their localities are more remote and this variation is probably due to their adapting environment as it has changed in this relative new era. You would see a bloom of variations within a region if the species is newer, as each tries to find accommodations for their colorations and forms as it searches out their new environment. Like so many of the dinosaurs trying out all sorts of variations. A more streamlined version where characteristics are rather uniform and consistent are characteristics of an established colony of species. For N. mirabilis to be in so many diverse locations and far away places separated by vast oceans only suggest that this species has been around for a very long time. This makes more sense than water fowl trying to relocate to new regions of untried and unweary occurrences of success or failures. Nature doesn't guess at surviving. The reason why N. mirabilis is where it is in so many different places is because they have been successful in their survival and ability to reproduce and sustain their livelihood. Food, water, light, etc. have been a part of their existence for a very long time. They are not pick up and go species which adapt to the wind of chance. Theirs is a tried and true existence.
M
|
|
Dave Evans
Nobiles
dpevans_at_rci.rutgers.edu
Posts: 490
|
Post by Dave Evans on Jul 24, 2009 17:54:26 GMT -10
The same ripple wave example can be said about N. mirabilis as it specializes (i.e. N. sp. Viking, N. rowanae, N. m v. echinostoma, etc.) as each has specialized in their respective region (as would your example of N. maxima and rafflesiana). The problem I have with this theory is most of these species also occur with or near the current version of N. mirabilis. I think the only one which doesn't is N. mirabilis var. echinostoma. So how could different species diverge from one species and the previous species still be extant and living close to or even in the same habitat as the species it evolved from? The only way I can see this happening is if each of them arrived at their current locations at different times so they were already different species when the next wave arrived. One of things about evolution is it tends to dead end. Simpler versions of lifeforms can stay small and as generalists occupy a large area. Probably N. mirabilis did evolve from a simple species and did not "de-evolve" to become a generalist, it just evolved from another generalist type species. Once something becomes highly specialized it tends to become dependent on that specific type of habitat. When the habitat changes too much it goes extinct because it's specialized adaptations don't work well in the new habitat, while the generalist can still adapt to new conditions. A good example is the dodo bird. It was highly specialized to its island life, but it could not adjust to new predators due to the changes which previously allowed it to take over a new niche, while most birds that aren't so specialized and they can still evade new predators; thus it evolved into a dead end. Its internal changes that allowed it to fit perfectly into its niche left it without the ability to have a chance in new conditions.
|
|
Dave Evans
Nobiles
dpevans_at_rci.rutgers.edu
Posts: 490
|
Post by Dave Evans on Jul 24, 2009 21:18:44 GMT -10
*(Dave Evans) This is an interesting inference: Some species survive longer than others but all species end in extinction. The reasoning would be that the longer a species has been around the closer it is to extinction. This is, mathematically, true. The trouble is that the reverse inference, that the closer a species is to extinction the older it must be, is clearly false. *(Dave Evans) Does diversity of form suggest relative age? This is the “species variation criteria” I mentioned at the start of this thread, i.e., that the longer a species has been in existence the longer it has had to produce greater variation or specialization. Much like the previous suggestion the inference is trivially true as stated but false in the other direction. Although, we can say that variation is a factor of time ( ... again, trivially true), we cannot say that greater relative time necessitates greater variation. Some species may evolve and diversify relatively quickly while others may change very little over vast numbers of years. The causes of “varietal diversification” and “ecological specialization” must be manifold and, certainly require some increment of time but “more time” or “longer periods of time” does not necessarily imply greater diversification (or distribution). Hmm... Well let use humans as an example: our population has been expanding and we have not been evolving during this time frame. We used to share the Earth with more than one species of human, but we probably killed them off, just like we are currently killing off the rest of the primates so as time goes forward we are reducing the diversity of primates as a whole, but over time we should see an increase our own diversity because our numbers continues to increase and there are more chances for increased diversity over a shorter period of time. We're still in the expansion stage of our population growth as a species and if we keep our technology we will not diverge because anyone can move anywhere and mate with whoever they feel like. Our species started to diversify slightly making adaptations to local conditions, but this was stopped cold by technology at least several 100's of years ago. So we have been expanding our territory by using technology to artificially make us generalists that can survive conditions that should kill us. I don't think Nepenthes species kill each other off, like primates do; but I do think the pattern is the same. The generalist spreads far and wide and later becomes different specialists. If we lost our technology the same thing would happen to us and maybe other primates would have a chance to expand their territories and possibly diversify as well. Also, all species do not end in extinction or the only life on earth would currently be rather simple. It is probably more accurate to say all specialist species end in extinction while generalists continue to give rise to new specialists as well as new generalists.
|
|
|
Post by marka on Jul 25, 2009 5:01:21 GMT -10
First of all, I do not believe that grasses are a newer plant form in evolution. The simplicity of a chance pollination would never work unless the species was well established in communities so timed flowering or wind pollination could occur. The simplicity of a chance pollination has to apply regradless of the age of the species, whatever the age, same problem. I still believe that mirabilis is perhaps the oldest species of nepenthes and has survived in the many regions it occupies. This species has many many variations leading me to believe that this species had several million years to think about what prey it wants to capture, where they want to occupy and what form they will take up. N. rowanae, sp. Viking, ssp echinostoma, et al are all forms of mirabilis. A new species just doesn't take these advanced forms from being the first one on the block. They had an experience of time to commit themselves to what they were evolved to. It's odd that N. mirabilis hasn't traveled and become a highland evolutionary form. Birds do fly highland and many water fowl also migrate between temperate and tropical climates, yet we do not see any unusual forms of mirabilis growing with rajah or other successful highland species. N. mirabilis would have had to be in place on each respective island prior to Pangea breaking up and spreading. This may sound a bit far fetched but nepenthes do show primitive flowering mechanism of dioeciousness and yet specialized in creating nectar rewards with attractive evolved leaves-pitchers. m The problem is with this argument is that we seem to regard evolution as a slow process, when ireality it can be blindingly fast. New species have been documented to evolve within decades. Arent all Nepenthes dioeciousness? Even in the UK, lowland ducks do not visit upland bogs, period. No nepenthes is temperate, even if they live close to temperate climates, but mirabilis is the closest thing we have to a temperate nepenthes. I dont see any logic in your arguments at this point.
|
|
|
Post by rsivertsen on Jul 25, 2009 5:22:43 GMT -10
No nepenthes is temperate, even if they live close to temperate climates, but mirabilis is the closest thing we have to a temperate nepenthes. I can't agree with that; I've had N. mirabilis (several different forms) along with dozens of other highland and lowland species, and N. mirabilis is very sensitive to cold temperatures, and one of the first things to get adversely effected when temps drop below 40F, and die with the first (even mild surface) frosts, while other plants take a hit, but recover, and some highland species, never even slow down. Even a few established N. truncata plants have taken a mild frost without too much damage. - Rich
|
|
|
Post by marka on Jul 25, 2009 5:50:45 GMT -10
And yet it is the only nepenthes that grows in a lowland subtropical/warm temperate climate and survives light frosts in the wild. THe clones from warmer climates are less tolerant...
|
|
|
Post by rainforest on Jul 25, 2009 8:43:39 GMT -10
Nepenthes are subtropical. They do not fall in the temperate zones but live under the tropical-subtropical belt.
I don't see how the human example is pertinent since the human race is very young.
Sphagnum is found everywhere but it isn't a new development. So what's your point? The Galapagos tortoise is found on all the small islands, but we know that this isn't a new species development, we see that each island has its own form/race of the species. As each island has its own species of finch, the opuntia that grows on each island is different and have adapted to different forms by evolutionary standards. Yet the closest species of each would come from their closest continent, but that hasn't proven that giant tortoises originated from their continental divides. No closest appearing species of the animals and plants for that matter seems to originate from their continental counterparts. Why would tortoises from the mainland encompassing Geochelone evolve into something rather different in form to a larger species on a smaller land mass with less food supplies UNLESS they were there to begin with. With lower sea levels, land bridges and shallow sea mounts would make these islands one large land mass. A rising of the sea level would separate many of the mountains of these islands into separate islands where they shared one big land mass. Evolution wouldn't take that long to maintain each respective species to stay within the confines of its genetic make up. As do N. mirabilis, keeping the form that it had when they were all one land mass. N. mirabilis has been able to keep it's form and been adaptive to so many variables not because it is new, but rather because they have been around. Pitcher dimorphism, some with deciduous root stocks, others with resistance to sea water. This is not a new developmental phase but one where the plant has adapted to a wide range of conditions by being exposed to it, for a very long time. For species to evolve around atolls where the rising and dropping of sea level or the infrequencies of tsunami's have allowed this species to adapt and survive where they grow. N. sp. Viking have been swallowed up by the recent tsunami, yet they have flourished where other plants have not come back. This would not be a"new" development for this species unless they have been around a while to adapt to these infrequent rising and dropping of sea level.
The dodo bird was extinct due to man. And while introduced predators (dogs, rats) may have also contributed to their demise, this was not due to evolutionary extinction. T-Rex didn't just drop out of the sky. The herbivores had time to evolve with defenses as did the top predators develop more skills in hunting them.
Is this FACT or OPINION? I do not know which form of mirabilis is subject to FROST. What region are you referring to? What form of mirabilis receives frost in habitat.
Regarding the OPINION that if N. mirabilis has evolved into a more "evolved" state and would not persist as the original form, that wouldn't hold true with regard to finding N. mirabilis and N. sp. Viking growing in the same region. Interestingly the mirabilis found in these regions also exhibit their dormant rootstock (as do N. thorelii, smilesii, kampotiana, etc.) from this regional habitat. Not something I would say could develop in a couple of decades.
My theory is that N. mirabilis were in place well before birds flew in those regions. There is nothing attracting birds to nepenthes especially for dispersing seeds. N. lowii may be the closest bird attractant but don't see how they can aid in seed distribution. N. mirabilis were already in place by growing in a large land mass area. These land masses separated by rising sea levels and continental drift theory to separate them, yet kept them in place adapting to its environment. This is more a likely possibility than birds dispersing seeds abroad. Why would lowland birds who live in a tropical climate migrate or need to fly to another lowland region if they are successful in their own? That doesn't make any sense. Birds will migrate if their region experiences a climate change or seasonal change annually. We have a several seasonal birds that can stay here the year around if they wanted to. But they do migrate to other regions during the opposite seasons. So the bird theory is of little significance.
Dioecious flowering is an older method of pollination in plants. Most of the older species which have been around for millions of years exhibit this form of pollination. Cycads is an example of dioecious flowering habit.
M
|
|
Dave Evans
Nobiles
dpevans_at_rci.rutgers.edu
Posts: 490
|
Post by Dave Evans on Jul 25, 2009 9:34:02 GMT -10
N. mirabilis has unknown northern limit on its range because it is also found in China. What is very unfortunate is the Chinese are destroying their environment faster than any other group has and only have plans to increase the level of destruction. Oh they are also giving Indonesia a lot of financial incentives to also destroy their forests and replace them with palm oil. Based on known species densities, it can be reasonable to extrapolate that there probably are further unknown species living in China. The dodo was killed by cats dogs and humans. Explain how the new predator species in its environment didn't kill them off, please. "Fact or opinion?" Dude, do you have a clue what you're saying? The dodo went extinct because its previous adaptations left it completely vulnerable to new predators--this includes humans. I bet dodo tasted pretty good
|
|