Dear Evolution students,
Thank you very much for your questions. It was interesting to get so much feedback on an article--that doesn't seem to happen very often in the "real" world. I hope that my responses are helpful to you. Above all I want to stress that I don't think I have found THE answer. Instead I simply hope to have presented an idea that some may find thought-provoking or interesting.
QUESTION 1 --------------------------------------------
Regarding her article "Naming Species" from Kyle Ashton, Ami Ben-Artzi,Todd Schlenke, Erik Wilhovsky, and Lisa Wyatt.
A) If you have a sympatric group of closely related organisms, it seemsthat it would be hard to determine which "species" (ferespecies orexclusive species) that a particular individual that you just collectedbelongs to. For example, it seems that it would be impossible to name anindividual brineshrimp to its "species" since you can't really keep trackof it and its breeding partners in a natural habitat. Is there an easyway to name this individual?
ANSWER 1A:
The criterion for determining whether a group at the species-level (by "at the species-level" I specifically mean a group within which there is interbreeding, or, equivalently, within which relationships are reticulate) is exclusive is concordance of gene genealogies. Specifically, all genes (and remember a "gene" in this context is defined to be a piece of non-recombining DNA) must have gene trees on which all genes from the members of the group form a clade. For example, all of the "X" genes from the group called "purple" must form a clade relative to all of the "X" genes from other groups AND all of the "Y" genes from purple must form a clade relative to all other "Y" genes AND all of the "Z" genes...etc. Thus, each gene tree (the tree for "X", the tree for "Y", etc.) will agree that purple's genes form a clade--> the gene trees are thus said to be concordant.
That is the criterion by which exclusivity can be determined, and there is no other. So, the way to determine whether a specific brine shrimp belongs to a ferespecies or an exclusive species is to sequence its genes, sequence the genes of members from brine shrimp species it may belong to and groups that are closely related to that one, reconstruct gene trees, and see where the individual falls out on the tree, and what the status of its group is based on those gene trees (i. e., exclusive or not?).
I grant that this is most decidedly not easy--it would take a tremendous amount of time and money. It is clearly not practical for, say, an ecologist studying brine shrimp competitive interactions to have to sequence all of the genes from hundreds to thousands of organisms in order to know what to call one particular specimen. But, here we run into an issue that I will bring up again and again in responding to your questions: the problem of practicality vs. reality. Both things are very important: to do our work we MUST have concepts and theories that work practically, but it is also important to try to understand reality. I guess what I'm saying is that yes, it's true that my criterion for naming species as either exclusive or as ferespecies is impractical. But if we are interested in species and we think genetic relationships and genetic exchange (e.g., through interbreeding) is important, and we think that those kinds of connections are important in whether the group maintains some kind of common historical tendency and fate, then defining groups based on the patterns of those connections seems reasonable. No, maybe it can't be applied to everything right now, but perhaps having THOUGHT about things this way can help clarify what we think is important about "species", what kinds of information we would LIKE to gather if and when we have enough time/money, or whatever. In short, while of course I agree that practicality is extremely important, I also don't want to give up trying to think about reality more clearly, even if it isn't practical.
B) On a related note, it seems that your naming convention calls for a newname at every node of a conventional cladogram. Assume the base"species" of this cladogram remains relatively unchanged through manybranchings off the chain. If you found a fossil of an individual of this"species", how would you decide which of the many possible names to giveit since you don't know at exactly what time it lived?
ANSWER 1B:
Fossils are definitely problematic, both because it is difficult or impossible to sequence their genes, and because, even if that were possible, it is almost certainly impossible to sequence the genes from other organisms existing at its same slice of time (that is, all of the closely-related organisms living at the same time as the fossil). One solution, however, is to place the fossil in the smallest clade to which you know it belongs. This may not be a species (whether an exclusive one or a ferespecies), it may be a larger group that consists of many species. For example, we might put a fossil lizard specimen in the clade Iguania. Thus, the specimen would not be assigned to a species taxon, but that's ok as far as I'm concerned.
QUESTION 2 --------------------------------------------
From: Lydell B Gorski, Melinda Marks, Matt Moses, Joseah Rosales, Marina Welker
I have a question concerning Anna Graybeal's paper on phylogenetics. Partof her definition of what an exclusive group is mentions that the group isnot reticulate. Then in her table including the category "ferespecies,"she lists a group who's characteristics are that they are exclusive andthey interbreed. "interbreed" is later termed to mean reticulate. Howcan this be?
ANSWER 2:
I'm curious to know where it seemed that I was saying an exclusive group is not reticulate, because that is not really accurate. Without knowing exactly which sentence you're refering to, I'll just try to clarify here: first of all, exclusive groups can be either single "species", or they can be clades. Both kinds of entities can be exclusive. An exclusive clade (e.g., a group of 25 lily species) has reticulate relationships *within* each species, but not *among* the 25 species of the clade. An exclusive species, on the other hand, has reticulate relationships among all its members (the group is freely interbreeding).
QUESTION 3 --------------------------------------------
Discussion F 11-12 Team 6: Barbara, Eric, Henry, Jackson, Jenn
In your article you mention that if a member of an exclusive species fromItaly migrates and mates with a member of a different exclusive species inBerkeley and have offspring, then both species are now ferespecies and mustbe given new names enclosed in quotes. Is that proposal feasible? What ifno one witnessed the migration of this Italian species to Berkeley and thesubsequent mating of the two species? How would all information regardinga species be monitored? How would observations be confirmed? Who would beon charge of these tasks? It would be difficult to record every possibleslight change that could occur. There is also the question of agreement inthe field on which changes where significant enough to warrant a change inname.
ANSWER 3:
Please see my response to question 1, first of all regarding how exclusivity is determined (i.e., the hybridization event doesn't necessarily have to be observed, one simply has to sequence genes), and second of all concerning the dilemma of practicality vs. reality. I agree that my ideas are not very practical to implement given current technology, but I still think they may have intellectual benefit. One thing I should note is that the example you cite, where the Italian moves to Berkeley, was meant as an extreme example to demonstrate how the concept of ferespecies works. I certainly wouldn't rule out that kind of one-time long-distance hybridization happening in the real world, but I wouldn't expect it to be a common problem.
Problems may also arise in the literature. If a species' name couldpotentially change at any given time, how would that effect previouslywritten literature which reffer to a species by its older, outdated name?Should older literature be updated? How? Would scientists who areinterested in literature outside their fields be able to understand andidentify a change in a species' name? Or would literature, then, becatering only to specialists who had access to the latest information? Thatmay become very isolating and establish barriers between individuals.
ANSWER 3, PART ii:
You are certainly right that the literature can be become very confusing, but these problems have nothing to do with my ideas, they are in fact exactly the kinds of problems we face now! Species names get changed, outdated names remain in the literature, specimens get misidentified and important information is forever buried under an incorrect name...that is the situation we have, and no one has managed to change it. It may be that we haven't come up with a better system because there isn't one that would be free of problems. For example, if we forbade changing taxon names, we would undoubtedly suffer since we couldn't correct any mistakes as we gained more information. But maybe some of you can think of something--?
QUESTION 4 --------------------------------------------
IB 160 Question for Anna Graybeal from Team 4, Assaf Cohen, Alicia Chan,Jack Chung, Nicole Shehadi, John Su:
In your Bufonidae example, why is there confusion in distinguishing betweenthe two Bufonidae asper groups? Is the problem that they are named usingbinomial nomenclature, or that they are named paraphyletically? What arethe "intellectual benefits" to which you refer, and why do they outweighthe practical costs?
ANSWER 4:
The confusion results primarily from the fact that species names are not unique, only generic names are. If we switch over to a phylogenetic system of nomenclature (as recently outlined by Kevin de Queiroz [former student of David Wake] and Jacques Gauthier [former student of Kevin Padian] in a series of papers), species names will no longer be binomials, but instead will be uninomials (single names). So, the two hypothetical species in the clade Bufonidae will have the same name (asper; now they are called Bufo asper and Pseudobufo asper). As a further complication, the genus Bufo is probably paraphyletic, meaning that its name either needs to be abandoned or re-defined. But this fact alone wouldn't cause a problem if the two species names were different.
For the second part of your question, see again my response to question 1, about practicality vs. reality. The "intellectual benefits" I'm referring to are things like being able to define species in terms of the features that we seem to think are important in their existence, i.e., gene trees and genealogical realtionships.
QUESTION 5 --------------------------------------------
We are group 2 of the 11:00 to 12:00 section.
Why should the branching off of an exclusive population from a main group(a ferospecies) result in the recognition of the main population as a newspecies if that main group really hasn't "changed"? Is there any othercriteria in recognizing a new species within a ferospecies other than adivergence of an exclusive population?
ANSWER 5:
I guess I would throw the question back at you and ask how it could be possible that the main group "really hasn't changed"? What do you mean by that? To me, if a splitting event occurs, both daughter groups are different than their ancestor, even if one daughter group consists of a very small number of organisms relative to the other daughter, even if a great deal of character evolution occurs in one daughter but not the other, etc. They are still *different* from the ancestor because they contain different subsets of the ancestors gene histories.
We are also curious about other people's response to your ideas. Can yousuggest a system to easily translate the established Linnaean taxonomynames into the new system which you have proposed?
ANSWER 5, PART ii:
de Queiroz and Gauthier have written a series of papers proposing a phylogenetic system of taxonomy, whereby taxon names are defined according to phylogenetic relationships, rather than according to characters (e.g., mammals would no longer be "defined" as tetrapods with hair and mammary glands, they would be defined as the common ancestor of monotremes, marsupials, and eutherians and all descendants of that ancestor). These ideas are heartily endorsed by some biologists (like me!), but they are far from becoming generally adopted. It will be interesting to see what happens to them over time.
QUESTION 6 --------------------------------------------
Frm group 5, discussion fri 2-3
While your new proposal categorizes species in a beneficial manner,how does it deal with the issue of potential hybridization in the field?Although "The exclusive status of a given species level group will bedestroyed by interbreeding of one of its members with any nonmemberbecause the genes of some of the group's members will share commonancestors with those from nonmembers before they share common ancestorswith those of other members." (page 245) how can we declare that twospecies are ferespecies on the one instance of hybridization, ifrealistically this will not be detected until the effects of hybridizationbecome visible--possibly to the extent that the hybridized group couldhave already attained exclusivity?
ANSWER 6:
You are right that the practical implementation of these ideas is difficult (see previous discussion of this issue under Questions 1 and 3). And in fact it's true that real instances of hybridization may be missed if the group becomes exclusive again before anyone takes a look at its gene trees. That doesn't seem like a big problem to me, though. After all, we expect any ferespecies to become exclusive eventually, provided there is no further interbreeding with non-members and no splitting events. Once the status of a group changes in reality, we simply change the status we use to describe it.
QUESTION 7 --------------------------------------------
We are group 2 at 1-2 on Friday. Here are our questions.
A. In your article "Naming Species" you state that gene genealogies can beused to determine if a set of organisms constitute an exclusive group.What level of genetic similarity (shared silent mutations, conservativeamino acid substitutions, or alleles) do you think would be sufficient todetermine if a group is exclusive?
ANSWER 7:
See my response to question 1: basically the level of genetic similarity is immaterial, what matters are the descent relationships of the genes. The gene sequences from organisms within an interbreeding group are probably highly similar to each other, but the actual levels of similarity are not important--all that matters is how closely related they are relative to gene sequences of organisms from outside the group. (There is a parallel here with a critical issue in phylogenetic taxonomy: what de Queiroz and Gauthier are saying is that we don't want to define taxon names using character states, because given the fact of evolution we expect character states to change, and that will makes our definitions useless [e.g., just because birds evolved feathers and wings and endothermy, they suddenly can't be dinosaurs, because dinosaurs are defined as lacking those things...]. Instead, we want to define taxon names based on common ancestry, because that is a property that will stay fixed through time.)
B.You say we should stop trying to define the category "species" andinstead set about recognizing the kinds of units formed by theevolutionary processes important in the diversification of life: descentand interbreeding. But aren't species and these "evolutionary units" thesame, and if not what are their differences?
ANSWER 7B:
Well in a sense I agree with you. But what I was trying to do is get around the problem of "term capture"--certain terms are so widely used (e.g., species, adaptation, homology) that everyone wants to claim them for their own personal definition. For example, I could publish "Anna's concept of homology" under a new name (e.g., "feremology", to be completely silly), but who would care? The likelihood is that few people would use the new term, and instead people would just continue to debate what the definition of homology ought to be (as an example consider that Gould and Vrba's term "exaptation", while appreciated by many, is really not often used). In order for people to listen I need to propose a new definition for the word homology. So I was just suggesting that, if possible, we stop fighting over the definition of the term species, and start thinking about what kinds of entities are important in evolution, and important for us to name or otherwise recognize.
C.Scientists have documented the evolution of parthenogenetic species fromsexual parental ancestors (in geckos) as well as the evolution of sexualspecies from asexual ancestors (in guppies). Can your naming system dealwith such situations and if so, how? You imply that asexual organisms arean evolutionary "dead end" and appear to leave it up to the reader and thescientists using your system to decide for themselves how to group them.Doesn't this make your naming system just as problematic as the biologicalspecies concept???
ANSWER 7C:
I'm very surprised to hear that you think I consider asexuals to be dead-ends. I don't think that at all! and I'm sorry if I gave that impression. See my comments below under question 12.
QUESTION 8 --------------------------------------------
This question is from Chayanin, Dan, Mike, and Serena of Team 6 - Friday2-3 Discussion:
Dr. Graybeal:In your article, "Naming Species", you do not see it necessary to includethe potential to interbreed as part of your extensive classificationapproach. This deviates from Mayr's definition of species and it seems tonarrow your perspective in species relationships. To produce a "history"instead of a "chronicle" isn't it necessary to show how multiple species(or members of one species) are related to the fullest extent?
ANSWER 8:
I'm afraid that I don't understand what you mean by "fullest extent". To me, the *potential* to interbreed does not have any impact on actual relationships. Even if two groups can interbreed, if they don't, then the status of their relationships won't change.
An aside to the above question, which you might know the answer to:How do evolutionists deduce whether a set of organisms really do have thepotential to interbreed? It seems that this information would not besomething accessible through normal scientific means.
ANSWER 8, PART ii:
You are right that evaluating the potential to interbreed is very tricky. One could imagine bringing organisms into the lab to see if they can breed there, but the lab conditions might alter things such that you aren't answering the question of whether they could breed in nature. Also, as I allude to above, it doesn't really matter if organisms have the potential to interbreed if they aren't taking advantage of that potential. I think these are some of the reasons people have had problems with this aspect of the BSC.
Our last question is that if no two species may be calledexclusive species when they both share even the least amount of geneticinformation with one another, then how is exclusivity between speciesestablished, and when? The phylogenetic tree, if carried further down, willultimately result in no exclusive species since organisms evolve from somegeneral ancestor. If our understanding of your theories about exclusivityis correct, then species do not exist!
ANSWER 8, PART iii:
I certainly never meant to say that species cannot be exclusive if they share the "least amount of genetic information." As I outline in the response to question 7A, the degree of similarity among the genes is immaterial, what matters are the phylogenetic relationships among the genes. Of course closely related (and, as you note, even distantly related) species share a great deal of genetic similarity. Maybe looking at the response to question 1 will also help clarify this point.
Also, as an attachment to our questions above, we are inserting acomment about species selection. If individual organisms, rather than thespecies, are the ones who are subjected to selective forces (ie.environment, genetic), then how can species selection exist? Thankyou very much for your time and effort!
ANSWER 8, PART iv:
The issue of species selection is hard to understand--many students in Evolution class have had trouble with it, and so have many biologists. The way I try to understand it is like this--there are three necessary elements to get selection on a trait: variation in the trait, heritability of that trait, and difference in fitness due to the trait. Is it possible to find these three things among "species" (however defined)? That is, are there traits that species either have or don't have, that vary among species, and that may cause some species to have greater fitness (e.g., give rise to more daughter species) than other species? (One weird thing here is the idea that one species could "give rise" to many daughter species...for example, I would say that once a species "speciates", it can't speciate any more, because it's no longer in existence--instead two new daughter species exist. So instead maybe the way to evaluate the "fitness" of a species is by asking if that species can be the ancestor to a larger clade than another species.) So, now we need to identify species-wide traits, and these have to be "emergent", that is, which are features of the species as a whole rather than of its component organisms (you'll get to this later in the course, or at least I think you will). Identifying appropriate emergent traits seems to be the big problem with species selection--there don't seem to be any, or at least not many sensible ones. The best example I can come up with are traits which are frequencies--e.g., a sex ratio. It is impossible for a single organism to have a sex ratio, it either is one sex or the other. But a species as a whole can have a sex ratio. So, imagine that we have 3 species, all of which have different sex ratios. And imagine that when any one of these speciates, its sex ratio is "inherited" by its daughter species. If the species with the highest sex ratio allows it to give rise to larger clades, then we could imagine that this species would leave more "descendants" in the future. Voila! selection among species! But does this really happen in nature? I don't think people have a good feel for that (I certainly don't).
QUESTION 9 -------------------------------------------
Here are the question for Anna Graybeal from group 5 in the Fri. 11-12discussion:
A. In determining exclusive groups you stated that "improper applicationof cladisitic methodology is avoided bcause gene trees, not organismtrees, are used to reveal the status of groups of organisms..." First ofall, with reducing entire organisms and species to collections andvariations of DNA, how much variation is enough for a group to beconsidered exclusive? Furthermore, paleospecies do not hold useful DNA forus to analyze (except in rare and fortunate cases). Thus we cannot use DNAfor "gene trees" to tell paleospecies apart. Our question is why you haveabandoned the use of clades to distinguish species, especially when youstate that "reality is best conceptualized via systematization..."?
ANSWER 9A:
I think I've answered (hopefully!) the first two parts of this question in responses to questions 1, 7A, 8 (on levels of variation, or degree of similarity) and 1B (on fossils). With regard to my abandoning clades...I found your comment very distressing! I don't think I've abandoned using clades at all, it's just that I'm using gene clades instead of organism clades.
B. Consider the vast number of plants that can hybridize with otherplants, for example. If such plants would then have to be considered aferespecies, wouldn't this increase the number of names needed to identifyorganisms to an impractical level? Moreover, how does your concept of aferespecies differ from a subspecies?
ANSWER 9B:
What exactly *is* the "vast number" you refer to? The lack of consideration for hybridization in plants is an objection frequently raised in discussions of species concepts, but I've never really had a good feel for how important it is. It would certainly be interesting to have more information about this. I'm not sure that having a lot of names is really a problem--if there are a lot of entities out there that we want to recognize, then we'll need a lot of names, and that seems perfectly acceptable. There are already far too many for any one person to memorize, so why bother worrying if there are even more? The difference between ferespecies and subspecies is basically that ferespecies are defined very explicitly, where the term "subspecies" has been used by many people to mean many different things. I could have used the word "subspecies" instead of ferespecies, but I avoided it because it already has so many other meanings.
QUESTION 10 ------------------------------------------
>From team 1 in section 11-12. (Rebecca, Dorothy,Robert, Hank, Julie).
With respect to Fig. 3 of your article, "Naming Species": Since thepresence or absence of interbreeding becomes a fundamental criteria used insystematization processes, how does a working evolutionary biologistpractically define interbreeding? For example, how would you classifyspecies which do not interbreed in the field, but interbreed underlaboratory conditions?
ANSWER 10:
I've touched on this issue in responses to other questions, but I'll just say again that for me what is important is ACTUAL genetic relationships, which are formed by ACTUAL interbreeding. The potential to interbreed is immaterial for my concept, and indeed I think that can be difficult to measure.
QUESTION 11 ------------------------------------------
Group 1 section 1-2pm Emily Wang, Brenda Larison, Michelle Kim, SusanHuang, Tania Kim
The pluralistic system you proposed makes theoretical sense.However we have some questions about its practical implementation.
A. We can foresee problems in implementation akin to trying toconvert the U.S. to the metric system ie.money constraint acceptability bythe scientific community, converting the current internationally acceptedsystem etc.
B. Given the number of decisions to be made about selection ofgenes to determine exclusivity (percentage of genome, part ofgenome (ie. degree of variability, under selection or not) It seems thatclassifications could still be arrived at by arbitrary decisions.
How do you propose to overcome these potential problems?
ANSWER 11:
All I can really say is that I agree with you about the potential practical difficulties, but I don't want to abandon thinking about how we might ideally like to name species, even if we can't implement those ideals perfectly in practice. (See also the responses to questions 1, 3 and 6).
QUESTION 12 ------------------------------------------
Friday3-4, group2
While we acknowledge the merit of many of your ideas concerning species, weare having trouble with their application to asexual species. First of all,"naming as taxa only those groups of asexuals (by definition exclusivegroups) deemed biologically interesting or significant" indicates a biasagainst asexual species. Many microorganisms still have not beenidentified, but we know that they play an important role in ourenvironment, our health, etc.. The whole need for changing our view onspecies is so that we can study all organisms in a more meaningful context.Your ideas do not fulfill this for many asexual microorganisms. Knowledgeof individual types of microorganisms is very important in , for example,the study of nutrient cycling, and how global change may affect microbialpopulations, and thus nutrient balance for all other life on the planet.Looking at their exclusivity- how closely they are related to eachothercompared to other groups, is not very apparent in the case of bacteria,unless we are to individually sequence each individual, etc. This does notgive us any meaningful information. The present identification ofmicroorganisms into "morphs" or "types" is already highly limiting- we needa way to differentiate these based on function, rates of performing thatfunction, etc.. How can this be incorporated into your species concept?
ANSWER 12:
I am sorry to have given the impression that I am biased against asexuals; let me assure you that is not true, at least intentionally. (Though it is true that I am more familiar with sexual taxa.) What I meant in my comment about naming only those groups deemed biologically interesting or significant was simply this: according to my definitions of exclusive species and ferespecies, it would be possible to name a new exclusive species every time an individual asexual organism gave rise to descendants (e.g., each bacterium could found a new species). But, naming all of these groups as species would be time-consuming, and in fact perhaps it is not *necessary*--we could just name those that we thought were important to talk about. The others can be parts of larger clades. So, I'm saying that if the asexual group is important (for whatever reason--because it has an interesting function, or is important in a microbial ecosystem, or whatever), then name it!
QUESTION 13 ------------------------------------------
Question from Group 3 1-2:00 section...
How do you account for hybridization and for self-pollination in regards toclassifying plants, for example as you seem to have minimized this verylikely possibility in your paper argument?
ANSWER 13:
See the response to 9B.
QUESTION 14 ------------------------------------------
Team 1 friday 3-4
Assuming that natural populations can segregate reproductively for 1, 2,10 or more generations, then once again transfer genetic material, wouldyou quantify ferespecies and exclusive species in terms of generationssince reproductive isolation? In other words, what degree of geneticexchange separates exclusive species from ferespecies designation and viceversa?
ANSWER 14:
The degree or level of genetic similarity does not affect exclusive status, though it is true that our expectations about how *long* it will take a group to become exclusive depend on generation time (given a certain population size and breeding structure, we can predict the number of generations until the group will be exclusive).
QUESTION 15 ------------------------------------------
group 5- discussion 1-2
Do you think the species concept issue can ever be resolved? i.e. Are wemoving toward a definition that researchers would be able to agree upon, oris there something inherently problematic with attempting to classifyindividuals in this way.
ANSWER 15:
No, I really don't think the issue will ever be resolved, because I don't think everyone will agree on the same definition. This is partly a sociological issue (see my comments under question 7B on "term capture"), but it's also a function of the fact that the future is unknown. There is a very interesting paper by O'Hara (Syst. Biol. 42:231-246) which makes this argument: basically he says that since all of our "species concepts" depend on expectations about what will happen in the future, all of them are problematic since the future can never be *known*.
QUESTION 16 ------------------------------------------
Question from Group 2 (Disc 2-3)
Definition of an evolutionary significant unit: "A population orgroup of populations must 1) be substantially reproductively isolated fromother populations, and 2) contribute substantially to ecological/geneticdiversity of the biological species." NMFS uses the ESU to define"species" under the Endangered Species Act. Our question to Anna is how shewould implement the concept of a ferespecies under the framework of ESApolicy.
ANSWER 16:
I really don't know how to answer this question. I think the whole issue of preserving/protecting organisms is extremely difficult. The definition of the ESU stated above sounds reasonable for conservation policy, and I don't necessarily think any extra stipulations about exclusivity etc. would need to be added.
QUESTION 17 ------------------------------------------
Section 2-3, team 4
In your paper, you state that it should be recognized that differenttypes of species exist,and that different groupings exist based on recencyof common ancestry, can we not formulate criteria for grouping asexualorganisms?
ANSWER 17:
Absolutely, and I tried to indicate some. See my response to question 12.
QUESTION 18 ------------------------------------------
Section 2-3 with Devin Team 3 Joanne, Rebecca, Dan, Cornell, Jennie
What are your thoughts on Van Valen's beliefs "(1) that genes are of minorimportance in evolution and should normally be considered there in nearlythe same degree (if not for the same reason) as other molecules, (2) thatthe control of evolution is largely by ecology and the constraints ofindividual development, and (3) that selection acts primarily onphenotypes, which are the building-blocks of communities." -Van Valen,Leigh. 1976-Taxon 25: 233-239.
ANSWER 18:
This question is very broad, and I'm not really sure what you're after. I guess I don't really agree that genes are of minor importance, though before being really adamant about that I would want to ask Van Valen exactly what he means by "gene" in this context. Likewise, I'm not sure what he means by "control of evolution", or how phenotypes are the building-blocks of communities. Perhaps if I knew more about exactly what you are wondering about it would be easier to focus my answer.
QUESTION 19 ------------------------------------------
From: carter@qal.Berkeley.EDU (Chris Carter)
A Obviously a key dilemma in the debate over what a species is or isnot is the need to bring our evolutionary conception of a species into linewith our operational use of the term in a field study. What sorts ofobservations in a field study of an organism would lead you to think it wasa ferespecies and not an exclusive species, and what tests woulddemonstrate the difference? In trying to distinguish properties andprocesses, at some point properties must be invoked to identify a processor change in it. You've used the coalescence of a proportion of genes asthe criteria for naming an exclusive species. Is it similarly possible toevaluate the coalescence of morphological or behavioral features, twoqualities more accesible to researchers, in the operational use of yoursystem?
ANSWER 19A:
This is an interesting point, because it certainly would be useful if there were other criteria besides actual gene genealogies that might "indicate" a group is likely to be exclusive. I guess if all members of a group have a particular morphological apomorphy that doesn't occur in any other taxa, that might suggest the group is exclusive (according to gene genealogies). More empirical data are needed to address this, however.
B In addition to recognizing the difference between an exclusivespecies and a ferespecies, have you considered recognizing differenceswithin the category ferespecies? For example, the entity created when twopreviously exlusive plant species hybridize is a very differentferespecies, in terms of the process that created it, than the ferespeciesthat each of the parental species represent. For one, it is a ferespeciesbecause it lost its exlusivity, and for the other it is a ferespecies atits conception. Should these different processes be recognized in yourscheme?
ANSWER 19B:
I think this sounds like a great idea--as long as it's helpful to recognize the results of different processes, I certainly support doing so.
QUESTION 20 ------------------------------------------
From: smarkos@garnet.berkeley.edu Date: Fri, 15 This is the question from team 4.
We understand the criteria used to determine that a group is exclusive -all of the members are more closely related to each other than to membersoutside of the group. We don't understand the events surrounding thespliting of an exclusive species from a fere species. Do the members ofan exclusive species become reproductively isoloated from the ferespecies? Do they develop different recognition systems? If so, asidefrom naming, how does this concept differ from other reproductive speciesconcepts?
ANSWER 20:
What I mean by a splitting event is a break in reproductive continuity: such that what was once a single reproducing group becomes two groups between which there is no reproduction. The daughter species resulting from a splitting event are likely to be ferespecies initially, and over time they are each expected to become exclusive. So, to answer your questions: yes, the two daughter species are reproductively "isolated" in the sense that are NOT interbreeding, but no, they don't necessarily evolve different recognition systems. That is, they may be capable of reproducing, but just not doing so. The exclusive species/ferespecies "concept" is different than other reproductive concepts because it is defined in terms of gene ancestry--it isn't enough that two groups are not reproducing, we also need to know about their gene genealogies to decide if they are exclusive species are ferespecies (though note that it IS enough to know that they are species of some kind).
QUESTION 21 ------------------------------------------
From: mmatocq@garnet.berkeley.edu
A. We were wondering how you came to the 50% coalescense level toidentify exclusive groups. Was that a shot in the dark or is there someempirical data on which it is based? We think that some usefulinformation could come from laboratory experiments. One could "track" theroad to exclusivity (by gene genealogies) and compare the percentages asgroups diverge (phenotypically, or even in their ability to interbreed).
ANSWER 21A:
Basically the 50% level was a shot in the dark, or maybe I'd call it an example of a cut-off point we might consider (just like any other value would be). There is very little empirical data on intraspecific gene genealogies, not to mention multiple gene genealogies from the same taxa, and I agree with you that it would be very interesting and helpful to get some!
B. Might there be special properties of (or associated with) mutuallyexclusive groups that would warrant specific classification of thesegroups?
ANSWER 21B:
I guess I could imagine the answer might be yes, but I can't think of anything right off the bat, and I would ask you what kinds of things you have in mind.
The End.