Speciation + Evolution = More Diversity

Hey Coyote, And I don't think you will get one. Or try to divert the discussion to another topic, like what the definitions of the words are. Given that they (rarely) understand genetics and (rarely) have any knowledge of the fossil record, it is not possible for them to provide evidence that they do not know. They go on the assumption that there were an original set of organisms, and then assume that this is supported by evidence.That is one of the reasons I want to focus this thread of the evidence of step by step evolution after speciation. Pelycodus is good for showing how evolution results in speciation, but the data seems to stop there.I found an on-line copy of a paper by Gingrich with a review of the fossil data for pelycodus and another version of his chart: SYSTEMATICS, PHYLOGENY, AND EVOLUTION OF EARLY EOCENE ADAPIDAE (MAMMALIA, PRIMATES) IN NORTH AMERICA
Vol. 24, No. 22, p. 245-279 (13 text-figs.) August 15,1977I want to quote one particular section as it mirrors what I've said:

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Given the pattern of phylogeny in text-fig. 10, and the details of morphological change discussed in the section of this paper on systematics, it is possible to subdivide each lineage into a sequence of valid species. Pelycodus ralstoni evolved into P. mckennai, which evolved into P. trigonodus, and SO forth. While the distinction between lineages is nonarbitrary, it must be emphasized that the exact boundary between successive species within a lineage is arbitrary (although each species as a whole can be distinguished morphologically). No natural breaks are obvious, and it is necessary for ease of discussion and for use in biostratigraphy to make essentially artificial boundaries between species. It turns out, largely for historical reasons, that these correspond fairly well with established subdivisions of the Wasatchian (Sand Coulee, lower Gray Bull, etc. - which themselves are poorly defined at present). Since the boundaries between time successive species must be time-parallel to make taxonomic diversity reflect biological diversity, the successive species of Pelycodus can potentially serve as a useful substitute in zonation of the Wasatchian, pending a full scale faunal study of this interval of evolutionary history. In this connection it is important to emphasize that the distinctions between species are based on comparisons of whole samples from each locality, and the transitions between species appear in every case to be continuous and gradual. Thus any zonation based on Pelycodus could be used, at best, to subdivide the Wasatchian into five subunits.
(p273)

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Here's the graphic:

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Our primary interest in studying Pelycodus and Copelemur has not been biostratigraphic zonation of the Wasatchian, but rather the patterns of phylogeny and evolution exhibited by these genera. The genealogical relationships of the species of Copelemur are still somewhat obscure, owing to the inadequate stratigraphic record of these species. The only reasonably certain relationship is the ancestor-descendant relationship of C. feretutus and C. consortutus. Within Pelycodus, on the other hand, we can be much more certain about genealogical relationships. The four species from P. ralstoni to P. abditus appear to be a single ancestor-descendant sequence, with P. abditus giving rise to both P. frugivoms and P. jarrovii.

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It looks like biostratigraphy is the direction to go, in order to find this kind of data organization.I found some information on Notharctus here
Page not Found | NYCEPIt does seem to discuss later evolution, but I could not tie it into the biostratigraphy above.Enjoy.Edited by RAZD, : notharctus

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Thanks onifre Quick answer - evolution: adapting to more than one ecosystem. A species population inhabiting two or more ecosystems will undergo different selection pressure in each one. If interruption of gene flow, or "reproductive isolation," occurs, then divergence can reach the point that daughter species do not interbreed when they have the opportunity.See

Definition of Species for more.

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Could you give a more laymen explanation, please?

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See asian greenish warblers, California Ensatina salamanders, discussion of ring species and article on Ring species as bridges between microevolution and speciation for more information.

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Rather than speciation branching in time these can be thought of as speciation branching in space.

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Does this mean the species know which members within their group are better suited for survival and they hangout together insuring a better success rate? Like some elitist group of birds weeding out lesser members, eventually leading to a parent/daughter population split?

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It is not unusual for a species to inhabit several ecologies, making partial adaptations to each. If there is sufficient separation between ecologies, they can form hybrid zones in between pockets of relatively stable ecologies. The populations in those pockets will tend to adapt specifically to that pocket ecology, even though they can still share gene flow through the hybrid zones, eventually around to the other varieties.

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There is also an effect called the "Wallace Effect" (Alfred Russel Wallace was the "other" Darwin ... and is sometimes called the "father of biogeography": the "Wallace Line" is also named after him):

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The Wallace Effect is the hypothesis that natural selection can contribute to the reproductive isolation of incipient species by encouraging varieties to develop barriers to hybridization.

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Note that this means that a species in a stable environment will tend to select for the most average phenotype, and thus stay relatively the same from generation to generation (stasis in the punk-eek terminology).

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When two varieties of a species had diverged beyond a certain point, each adapted to particular conditions, hybrid offspring would be less well adapted than either parent form. At that point natural selection will tend to eliminate the hybrids. Under such conditions natural selection would also favor the development of barriers to hybridization, since individuals that avoided hybrid matings would tend to have more fit offspring. This would contribute to the reproductive isolation of the two incipient species. [1]

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Note how this ties in to the ring species issue discussed above, with varieties separated by small hybrid zones: incipient speciation.

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If that is right, my next question would be, wouldn't that almost guarantee the parent populations extinction, since it's a split of better suited species from their lesser suited kin?

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Depends on how you view extinction: they continue in each daughter population. Now it may be possible for an intermediate daughter population to go extinct, could even be due to competition from the end varieties if they overlap far enough, and that would de facto leave the remaining varieties - the ones that don't interbreed - as new species.

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Cannot mate or choose not to mate due to selective reproduction?

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Yes. It doesn't matter as the result is the same: the daughter populations no longer share mutations by gene flow, and thus diverge from generation to generation.

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I hope when you're done weeding out the creationist babel you can continue with a more detailed explanations, thanks for another great thread.

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I don't have too much trouble with creationist babel comments that discuss the topic, only when they try to move the topic to something else or dodge the issues. They can assert silly things, such as genetic barriers, just as anyone without a full understanding of biology (and that includes me) can, and it provides a "teaching\learning opportunity" which can benefit others.

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For instance, it seems I am going to have to "bone-up" on Biostratigraphy to be able to go further with the available information on evolution after speciation, and be able to show how step by step, generation to generation, greater diversification of descendant lineages is achieved after speciation.

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Biostratigraphy is the branch of stratigraphy which focuses on correlating and assigning relative ages of rock strata by using the fossil assemblages contained within them. Usually the aim is correlation, demonstrating that a particular horizon in one geological section represents the same period of time as another horizon at some other section. The fossils are useful because sediments of the same age can look completely different because of local variations in the sedimentary environment.

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Biostratigraphy takes the relative age relationships of layers, by the principle of superposition, and then finds the fossils that show the succession of life from generation to generation, from layer to layer, and looks for fossils that are specific to a single layer to then use as an "index fossil" to compare ages of layers in other locations.

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Except that I want to turn it around and look at the original stratigraphic data points that establish the lineage of the fossils in time. I want to find the succession of forms of life in the different layers, as was done for Pelycodus above, extending further than a single speciation event. Strato-biology anyone?

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We know from Pelycodus that as species evolve over time that they become different from their ancestors, and at some point reach sufficient difference that we poor humans need to arbitrarily divide them into different species to discuss those differences.

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This would also occur after speciation, and because there is no sharing of genes\mutations\hereditary traits between the two new species that each will go through this process in different ways.

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The questions are: how far does this divergence go, and how fast does it get there?

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Enjoy.

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Edited by RAZD, : deleted dupes

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Hey Coyote, Yes, it correlates age, location and fossil diversity in one simple graphic.Of course paleontologists do this with individual finds: the document the dates, the sedimentary layers, the locations, and the ecology with each fossil found.Another presentation that is similar, but the geographic information is presented more as a schematic than the actual layer by layer used by Gingrich is the horse evolution: And it only shows Genus stages with actual fossils. Imagine this with the same detail as in Pelycodus. We know there is a lot of information available, it is more a matter of making the correlation than finding the data. Stratigraphic framework of early Pliocene fossil localities along the north bank of the Cimarron River, Meade County, Kansas

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Abstract

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The stratigraphy of early Pliocene (early Blancan) fossiliferous sediments exposed in canyons along the north bank of the Cimarron River in Meade County, Kansas is described as part of a larger, ongoing project to create a refined biostratigraphic model for late Neogene and Pleistocene mammalian fossil localities from the Meade Basin. Because the utility of previously named formation and member names is questionable, we introduce a set of informal names for stratigraphic units in our study area. Sediments in the region are up to 34 m thick, and include a basal sand and gravel (?Bishop gravel?) at least 9 m thick, overlain by up to 17 m of lightto pinkish-gray, fine-grained sand and silt, with interbedded calcium carbonate layers. These fine-grained sediments are overlain in turn by a second, 8.5 m-thick sand and gravel (?Wolf gravel?) that is itself overlain by about 5 m of calcareous silts culminating in a thick caliche. The stratigraphic positions of fifteen fossil localities, some with rich vertebrate assemblages, were determined in this study. The sites are found in a variety of sediments representing fluvial, pond, spring, and sinkhole depositional environments. Rodent fossils are especially common, and certain taxa, such as the geomyids, sigmodontines, and arvicolids, support the stratigraphic hypothesis based on field mapping. This combined stratigraphic and faunal information provides an essential part of the early Pliocene component of the Meade Basin Neogene and Pleistocene faunal database, to be used to examine the history of biological diversity in southwestern Kansas.

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Introduction

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The purpose of this paper is to present the stratigraphic framework of rocks previously referred to the Pliocene Rexroad Formation in canyons immediately north of the Cimarron River in southern Meade County, Kansas (figure 1). This project is part of a larger effort to develop a refined biostratigraphic model for the entire Meade Basin, leading eventually to a detailed examination of small mammal community evolution over at least the past five million years. In a series of studies from 1936 until his death in 1973, the late C.W. Hibbard and his students provided a faunal and stratigraphic succession for the basin (see bibliography of C.W. Hibbard in Smith and Friedland, 1975). The lowest part of this succession includes mammalian assemblages from the Rexroad Formation and rocks referred to the Rexroad Formation. Most of these older assemblages were recovered from localities in upland areas away from the Cimarron River where stratigraphic correlation is very difficult because the sites are located in small outcrops isolated by ranchand farmlands. Early in this project we recognized that the longest sections and more extensive exposure in relatively deep canyons along the Cimarron River might provide a superposed series of mammalian localities from which a more refined biostratigraphy could be determined.

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Sounds like the stuff we want, but no graphic presentation.Enjoy.Edited by RAZD, : spEdited by RAZD, : added info after horse chart

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Onifre Either. Reproductive isolation has occurred and the two populations now reproduce and evolve independently. Not hybrid species, hybrid zones. It is still one species until isolation occurs. The zones will be eliminated as hybrids become less viable than either of the two daughter populations. As the numbers decrease the zones will cease to exist, completing the reproductive isolation of the two daughter populations. Irrelevant to this thread.The point here is that speciation has occurred. How does this effect the evolution of the two (or more) daughter species to evolve further.If you want to discuss speciation, I suggest a new thread.Enjoy.

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Thank onifre, brief asides are not a problem. Ok. Now what we want to look at on this thread is what happens after speciation (however it happens, however you define it). What we have are these somewhat unique conditions that don't apply to the normal evolution of species over time:(1) near or overlapping ecology
(2) near or overlapping behavior
(3) smaller difference between the daughter populations than between either one and all other speciesWhat this implies to me is high competition for survival, and thus high selection pressure to become more different from the other population, or the probability that one or the other will go extinct is high.When we look at speciation (and evolution in it's aftermath) chronologically, as shown by Pelycodus we see: Where I have taken the liberty of drawing my own lines over fig.10 from Gingrich's paper. This is more representative, imho, of the actual course of events: not a linear trend, not a "punk-eek" picture, but one of adaptation from generation to generation under changing conditions and different rates of evolution, and some back and forth (non-directional) adaptations.Part of the changing conditions is the existence of other daughter populations after speciation, with competition for living space and competition for food sources.In this picture we see 3 different speciation events. The first one has a short lived branch to Copelemur praetutus (in green), probably because there was not enough separation between it and Pelycodus trigonodus, and going smaller was too difficult for survival. The second branch (in purple) is similar, except that Copelemur feretutus seems to have had room to go smaller, to Copelemur consortutus. There also seems to be a small branch in between that was reabsorbed into the species population by the next level.It appears that as the basal Pelycodus group tends towards larger body size (See Cope's Law), that there is more opportunity for a smaller primate to live in the same area, perhaps taking advantage of food sources high in the trees or at the ends of tree branches that the larger primates cannot reach. It is also likely that branching to a smaller form is easier than a larger one as (a) the trend already is to get larger, and we may already be seeing the maximum rate for this species to grow in size, and (b) the population is very likely already "pre-adapted" to take advantage of the smaller form, as they have inherited traits from smaller forms that could still be useful.Next we see another speciation branch, where Pelycodus abditus divides into Pelycodus jarrovii (still in red) and the smaller Pelycodus frugivorus (in blue). P. frugivorus is in the middle between P. jarrovii and C. consortutus, but is able to drive C. consortutus out, and then keep getting smaller to diverge more from P. jarrovii.All very exciting, however we are still left with two similar primates, P. frugivorus and P. jarrovii. P. jarrovii continues to grow in size and gets reclassified as a new genus, Notharctus (another arbitrary distinction, similar to arbitrary speciation, as are all higher taxon designations). P. frugivorus continues as a smaller primate.The question is: what becomes of the P. frugivorus and P. jarrovii lineages later in time? Just how diverse do they end up?Well one answer is all the primates alive today, from monkeys to humans, but that is for later.When we look at speciation (and evolution in it's aftermath) spatially, as shown by the Asia Greenish Warbler we see:Greenish warblers

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Greenish warblers (Phylloscopus trochiloides) inhabit forests across much of northern and central Asia. In central Siberia, two distinct forms of greenish warbler coexist without interbreeding, and therefore these forms can be considered distinct species.

Map of Asia showing the six subspecies of the greenish warbler described by Ticehurst in 1938. The crosshatched blue and red area in central Siberia shows the contact zone between viridanus and plumbeitarsus, which do not interbreed. Colors grade together where Ticehurst described gradual morphological change. The gap in northern China is most likely the result of habitat destruction.

Ecology and body shape/size

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Given the differences between the two northern forms viridanus and plumbeitarsus in plumage, songs, and genetics, we might expect them to also differ in ecological and morphological traits. Surprisingly, the two northern forms of greenish warbler differ little in habitat preference and body shape and size. However, viridanus and plumbeitarsus do differ from southern forms in these traits. The northern forms are about 10% smaller in body size than the southern forms, and the northern forms inhabit much denser forest at lower elevation than the southern forms. The northern forms also must migrate much further to their wintering grounds in southern Asia. So it appears that during both northward expansions there was parallel evolution of smaller body size and different habitat preferences, even though there was divergence in traits used in communication (plumage and song).

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So the two forms are similar in size, habitat and basic ecology (food sources, predators etc). What strikes me here, is that in the absence of the other variety, each would be able to take advantage of the opportunity of the other's habitat, but that the amount of overlap is small: as narrow or narrower than the hybrid zones between the other varieties. It clearly appears, imho, that they see each other as competitors, and thus block such spreading and co-habitation.Again, we see two species just after speciation, and the question is: what becomes of the P.t.viridanus and P.t.plumbeitarsus lineages later in time? Just how diverse will they end up? Will one drive the other out? Will the other evolve to take advantage of a different ecology so that there is less competition?EnjoyEdited by RAZD, : addedEdited by RAZD, : narrow vs small

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interrelation in Message 1 of Is natural selection enough to explain asks Natural selection alone, no. Evolution in general, yes.See Message 1 for more detail.Enjoy.Edited by RAZD, : esig

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