|
Post by stevestewart on Aug 29, 2008 10:37:15 GMT -10
Masa,
Discussing any plant species ancient vs. modern status is "a reach", no matter what plant Family is discussed. The "Whisk Fern" Psilotum nudum is thought by some botanists to be the most primitive vascular plant Family, and is thought to be the most modern fern by others. There are large amounts of fossil material of what are thought to be the first vascular land plants, and they look very similar to P. nudum. It depends on what traits are considered to be ancient. Some geneticists are now stating that Psilotum is a modern fern, with very reduced and efficient features. Two weeks ago I was looking at Wikipedia and Psilotum was stated to now being a more modern fern. Today, I wanted to post a link, and have found the information is no longer stated in such clear terms, and is now open for discussion.
Most investigators consider the more modern plants to have reduced more efficient features. Asteraceae is thought by many investigators to be advanced dicots, partly because this Family's flowers parts are reduced and in compacted heads.
If you have ever used a phylogenetic dichotomous key to vascular plants, you will find that Psilotaceae is the first Family and Asteraceae is the last. The problem is the conundrum that if a species has had given features for a long period of time those very features are efficient enough to have survived the test of time. Also the more primitive species developed without complex features, from simple single cells, into having complex interactive features that evolved slowly over time.
Are the incomplete, dioecious flowers of Nepenthes more modern and reduced, or more primitive and underdeveloped? Are carnivorous leaves advanced and continuing to become more carnivorous, or are they now primitive, non-efficient, and slowly becoming non-carnivorous, being replaced by more efficient roots, for use in better, more fertile environmental conditions?
There are no fossils of Nepenthes for us to analyze. That is why I enjoy speculating about them having once been giant aquatic Utricularia like plants with traps that closed on prehistoric prey, being blown into their now small, colorful and simple forms, by Super volcanoes! ;D
Take care, Steven Stewart
|
|
|
Post by unclemasa on Aug 29, 2008 11:00:46 GMT -10
Steven ....
You are right .... of course. I like to think that the winged mirabilis and winged rafflesiana are older but it could be that their ancestors passed through a phase with distinct tendrils and are now regaining them ( ... for whatever reason).
.... stretching like rubber man!
|
|
Dave Evans
Nobiles
dpevans_at_rci.rutgers.edu
Posts: 490
|
Post by Dave Evans on Aug 29, 2008 11:10:11 GMT -10
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. 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! Hello Sam, I think your numbers for the time line look pretty good. Now, since dinosaurs died out about 65 million years ago, and birds and mammals developed, by the time India was near Sunda, various bird species could have transported the seed on their feet to nearby islands since it wasn't a very long journey for them. Birds rarely make super long trips straight across open seas and if some were to "try" transporting Nepenthes from Sunda into India or Madagascar, it would be at least several days of flying. I think this would be far too long and the seeds would fall of of them into the sea, also as the birds would have to eat something probably from the sea they would wash the seed off as well while foraging. Temporary vectors which longer exist may have lead to the distribution we now see. I do not think it is likely Nepenthes seed would survive a trip a birds digestive tract. This can be tested out however. But they are seeds which generally need to be scarified. Seed transported as bird food have adaptations to survive these conditions. Nothing about a Nepenthes seed would seem to indicate such an adaptation.
|
|
|
Post by unclemasa on Aug 29, 2008 11:15:36 GMT -10
Rich ....
It seems I remember reading a study on Nepenthes seed dispersal somewhere ( ... maybe in one of Clarke's books). If I remember right, the range was pretty limited. However, assuming bird vectors would certainly expand the potential for wider dispersement. I'm glad you mentioned this as, most of the time, when thinking of birds, I have been assuming that the seed would have been eaten and then passed.
|
|
|
Post by unclemasa on Aug 29, 2008 11:26:32 GMT -10
Dave Evans ....
I agree. It does seem to me doubtful that Nepenthes seed would survive the digestive tracts of birds. On the other had, as you point out, millions of years ago who knows what herbivores may have dined on Nepenthes?
If I recall correctly there are a good number of bird species that are capable of very long flights over water and don't eat in the process. Still, seeds sticking to bird's feet over such long journeys does seem unlikely.
|
|
|
Post by rsivertsen on Aug 29, 2008 12:25:26 GMT -10
Nepenthes have been around and evolving for a very long time, and during their early development and distribution, may have been dependent for their pollination, as well as seed dispersal from creatures that may no longer exist! - which includes extinct birds and reptilian creatures, which may very well have had some migration patterns! - Rich
|
|
|
Post by rainforest on Jan 6, 2009 9:33:21 GMT -10
I'd like to keep this discussion going on the evolution of nepenthes.
I am still of the opinion that a species widespread such as N. mirabilis would be one of the common ancestors of todays diverse population of species. N. mirabilis has forms that may resemble new species. N. rowanae (once considered a form of mirabilis) has distinct pitchers and leaves. Similarly N. sp. Viking has peculiar coevolutionary trends closely lined with rowanae (pitcher roundness, coloration, trend in tuberous rootstock, flowering, etc.). We also know that N. mirabilis is capable of making extreme peristomes (i.e. N. m. v. echinostoma) and also taller tubular pitchers (Indo-Chinese forms) that many nepenthes follow.
If breeding dominance would be a consideration for an older species, highly developed peristomes should be considered more modern since crosses between species like macrophylla and lowii with macrophylla's prominent spiked peristome and the almost absent peristome of lowii to dominate.
But I would also place viscous fluid to be an advancement over watery fluids since it will require more specification for a plant to develop viscousness in its fluid to trap flying insects.
I am also in the belief that lowland species is older than highland species. the heavy presence of insects found in lowland areas suggest the need for carnivory higher where insects are more prevalent than higher elevations where large populations of insects appear to be fewer/scarce. But advancing peristome development to capture prey in a more competitive terrain would require fancy peristome attraction or making escape more difficult.
And while species such as N. pervillei, campanulata, etc. may appear primitive, I think these are more advanced than meets the eye.
What are your thoughts on this?
M
|
|
|
Post by unclemasa on Jan 6, 2009 23:09:20 GMT -10
Lowland / Highland arguments seem to make sense over the shorter term time scales ( .. a couple million years) but seem less helpful when talking about tens of millions of years as lowlands become highlands and highlands crumble. The assertion that peristome development can be linked to insect availability also seems to make sense but, as long as there are sufficient insects, it makes no difference. Whereas, there may be many more insects in the lowlands than in the highlands that does not mean that they are ever too few insects for Nepenthes to scratch out an existence. And while species such as N. pervillei, campanulata, etc. may appear primitive, I think these are more advanced than meets the eye. This is an interesting line of thought also. The more common line of though is that the Western species with their distinct differences in floral structure are examples of very primitive species. This is what François said earlier ... 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?). Still, for all we know, why not turn the argument around and say that these outlier species have been longer separated from the seminal population and as a result of their isolation have evolved away from the larger, more primitive, Eastern families with their shared floral structures? It is easy to get caught up in thinking about evolution as a linear progression. Neo-Darwinists like Gould were able to break out of this to some degree with theories of punctuated equilibrium, i.e., things stay the same until some significant factor changes causing perhaps many mutations at once. One might even suggest a theory of "Explosive Evolution" wherein a genome builds to a critical mass and then bursts into a thousand new combination in relatively short order. There may not be anything like a " Nepenthes Eve" or a first ancient species ( Nepenthes astralonepenthithicus ... say it! I dare you.) Maybe, a thousand species burst upon the world in relatively short order and what we see now are just fallout from that ancient explosion. It's fun to think about.
|
|
|
Post by philgreen on Jan 7, 2009 9:26:37 GMT -10
I am still of the opinion that a species widespread such as N. mirabilis would be one of the common ancestors of todays diverse population of species. M Whilst I wouldn't disagree, Bare in mind that Humans are far more wide spread than any of our close relatives such as chimps, or even the species we evolved from. Evolution tends to faviour offspring better able to survive in their environment and so more likely to flourish. But then, also species better able to cope in a more restricted habitat. Until the various tests are done to find out who is related to who, how and when anything will only ever be guess work - but still fun.
|
|
|
Post by rainforest on Jan 7, 2009 9:50:58 GMT -10
Nepenthes have occupied interesting ranges of climate and media variety. Some species are found just a stone-throw from sea water, others are found at rims of semi-dormant volcanos and others growing in water. If these collective growing variations indicate its range for survival it wouldn't be difficult to fathom that these have been around for a long time. Yet, dioecious flowering is a more primitive sexual format. This combining simple flowers with rudimentary basic tepaloid structures suggest that these are primitive even though lacking in floral advances, they have taken the cake for pitcher (leaf) modifications. No other plant family have made such advanced leaf modifications (other than droseraceae and sarraceniaceae, other cp) as to actually providing a function other than photosynthesis.
M
|
|
|
Post by stevestewart on Jan 7, 2009 11:59:28 GMT -10
Yet, dioecious flowering is a more primitive sexual format. This combining simple flowers with rudimentary basic tepaloid structures suggest that these are primitive even though lacking in floral advances, they have taken the cake for pitcher (leaf) modifications. No other plant family have made such advanced leaf modifications (other than droseraceae and sarraceniaceae, other cp) as to actually providing a function other than photosynthesis. M I agree! (and I will try to keep my imagination at bay here ) Think of the Section Bryastrum of Drosera. These little gems have modified their complete flowers, roots (prop roots) and leaf morphology while retaining the primitive non flowering plant type growth (gemma, circinate vernation) that gives them their sectional name. Flowers are considered by many plant physiologists to be the primary focal point for consideration of advanced plants, but in my mind this is somewhat arbitrary thinking, and not "fixed in stone" (except in the case of fossil records of course ;D.) Take care, Steven Stewart
|
|
jimmy
Urceolatae
Posts: 39
|
Post by jimmy on Jan 7, 2009 15:16:55 GMT -10
On the subject of highland peristome development: The development of spiked/specialized peristomes (among other traits) on highlanders is, in fact, likely related to fewer available insects. Mt. Kinabalu has only been in existence for fewer than 1 million years, whereas Nepenthes as a genus are thought to be about 120 million years old (I'll find the source and post it here soon). Of course, Nepenthes have to move up a mountain to set up shop. They evolve rapidly as they go, specializing to highland conditions...I may guess that highlands have fewer insect species and biomass, compared to lowlands, which have higher temperatures that suit higher metabolic rates for the insects. So insects should not be discounted as a factor in the evolution of more-developed peristomes in highlanders. Also, Mt. Kinabalu is speculkated to have been covered by glaciers as recently as 10,000 years ago, during the ice age. I imagine that conditions were much harsher on the Nepenthes, putting evolutionary stress upon them that could easily cause highly-adapted peristomes and plants to evolve much faster. As far as I know, insects aren't too common in arctic or antarctic glacial wilderness. That's my contribution to the speculation. I have yet to visit Borneo, but I like to think about this kind of stuff. This is indeed a wonderful thread.
|
|
|
Post by rainforest on Jan 7, 2009 16:31:06 GMT -10
The evolutionary trend we see in nepenthes is to suit their environment, find suitable/ample food and proliferate in a way to coexist with their cohabitants. This last focus is important as we see nepenthes always in unison with other plant species. I have not seen nepenthes swallow up their environment, even while growing amassed among other species, they don't choke out the competition as other weedy species do. i think this is an important evolutionary advancement that has allowed nepenthes to succeed where others have failed. While the majority of nepenthes are climbers, very few are not. The ability for nepenthes to produce less attractive uppers in liana is a trend to facilitate functional pitchers where insects still see or are attracted to green/less colorful pitchers. While not all is true on being a green upper, those that are green tend to be more productive in capturing air-born insects in a stratosphere of higher insect populations, as flying insects are higher on the scale of evolutionary trend over just crawling species. Many flying insects lack the ability to see color, they rely on UV and its lighted patterns to visualize attractants as a flower or food source for insects. To be able to vine and produce pitchers among a network of trees and branches allows nepenthes to expand into new territory to find new ground for prey. Other advances would be the attractants of odor/perfume attractants to attract the higher insect prey. Many consider lepidopteran insects to be high on the scale of insects and nepenthes that produce fragrant upper pitchers are (on my criteria list) more advanced than just pitchers that use uv light to attract prey. To follow the evolution of night flying moths and beetles to be attracted to scented pitchers is a definite evolutionary thrust over those pitchers just uing a chance mechanism to attract prey. Although a species such as N. inermis may seem haphazardly lucky to just have a sticky fluid that insects are attracted by way of light reflecting on liquid mass. Their pitchers are reduced or least developed. Either way, they are successful in obtaining prey in an openly mouthed pitcher fashion. Other species such as N. lowii has very advanced mechanisms to attract fecal matter and to evolve in a way that allows chance droppings to make a hole in one at least in a regional manner/closest to their smallish opening. N. lowii has very woody pitchers and a wide funnel form catch-all. A narrow waist for channeling matter into it and preventing rainwater from flushing its contents as seen in other species such as N. inermis and campanulata. This narrow middle girdle can also be a mechanism to prevent foraging animals from dispelling its content and tipping it out. Water and feces passes evenly by way of rainwater and water with heavier fecal matter passes easily down even in an already saturated fluid chamber.
M
|
|
|
Post by marka on Feb 1, 2009 1:58:08 GMT -10
It seems likely to me that Nepenthes originated from some Triphyophyllum like ancestor and found a niche habitat on cliff faces/mountainsides. Increased competition normally brings increased specialisation, which has pushed evolution along faster at the centre of nepenthes distribution where you have all the specialised, and therefore more highly evolved, species. As a general rule I would hold that as self evident.
Its interesting that many nepenthes grow in habitats that are in danger of drying out periodically. Whilst some have evolved tuberous rootstocks to cope with that, its obviously more difficult if you are clinging to a cliff face. Although the primary purpose of a pitcher may be to supplement feeding, a possible secondary purpose is to act as a water store. With that in mind, the need for a more viscous fluid takes on an added meaning, in that it cuts down the vapour pressure of the fluid, and therefore reduces evaporation.
I don't think its a coincidence, that a number of my plants cope with 'drought' far better when they have pitchers full of fluid.
Mirabilis I would suggest is a newer species, that has found a more efficient way of spreading. As a swamp/ditch plant, it may have latched onto a similar way of spreading common amongst aquatic plants. Seeds can disperse downstreams to some extent and be carried by water-fowl. This may explain how it has covered vast distances when other species fail to travel even short ones.
I would suggest it as a new species and rapidly spreading (geographically wise) species as it has not yet evolved into distinct species at different locations, although it appears to have started the process in some areas.
Bicalcarata is supposedly a relatively new species as its habitat did not exist 10,000 years ago, but apart from what i've read I don't have much opinion on that one.
|
|
|
Post by rainforest on Mar 17, 2009 15:11:08 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
|
|