tag:blogger.com,1999:blog-5460788270738656369.post3230548091881534510..comments2023-12-24T07:02:43.274+08:00Comments on Catalogue of Organisms: How to Recognise a SpeciesChristopher Taylorhttp://www.blogger.com/profile/11075565866351612441noreply@blogger.comBlogger8125tag:blogger.com,1999:blog-5460788270738656369.post-84061901492840572302009-07-30T10:08:48.851+08:002009-07-30T10:08:48.851+08:00The cases where new species arise because copulati...The cases where new species arise because copulation is not possible anatomically between different groups as in dextral & sinistral snails are also problematic, because the differences between the 2 groups (species) could be due to just one gene. Along these lines, can great danes & chihuahua mate? If not, they should be considered 2 separate species.AYDIN ÖRSTANhttps://www.blogger.com/profile/09891160904748206385noreply@blogger.comtag:blogger.com,1999:blog-5460788270738656369.post-86417190715330933672009-07-30T09:33:18.441+08:002009-07-30T09:33:18.441+08:00Biological variation is strongly discontinuous. S...Biological variation is strongly discontinuous. Sometimes the variation is as distinct as distant islands, sometimes it is more like nearby islands united at low tide, and sometimes it is like hills connected by valleys. This biological variation is real and worth describing and discussing. <br /><br />Humans need words to discuss things, to store and retrieve information, even to think about things. So we need to name biological variation. <br /><br />We need our words, our species names, to refer to mutually exclusive units. Biology isn't that neat. <br /><br />Therefore, there will always be a tension between our human need for mutually exclusive words and the variable (discontinuous or continuous) nature of real biological diversity. In other words, the species we describe will be more or less biologicaly real, but in some cases they will also be more or less arbitrary human constructs.<br /><br />We define species concepts in terms of biological reality, but in part (only in part!) our species concepts result from our need to categorize. Therefore, we can never find a truly final, completely useful definition of the species. <br /><br />What to do? Searching for the perfect definition of the species can only get one so far.<br /><br />As a practicing plant taxonomist, I choose to take species names seriously -- they do categorize real, important biological variation -- but also lightly. I use the species concept that seems to me best for describing variation in the group I'm working with (usually some variation of the BSC or PSC). Some species names clearly refer to real biological units, no matter what species concept I use. Others are the merely the best I can do at the time. <br /><br />I consider the species names I use to be hypotheses about similarity, patterns of diversity, and relationships among population. These hypotheses will be tested both by academic botanists and by field workers. The names will be accepted or rejected on the basis of their utility for describing and reporting variation and (in well studied groups) for expressing relationships. Most species ideas will be pretty stable (even if they wander from genus to genus!). Some will alternate forever between an inclusive and a more finely split definition. <br /><br />So it goes. <br /><br />(And now it's time for me to go apply some more or less useful names to some real diversity.)Barbarahttps://www.blogger.com/profile/14484430852843017156noreply@blogger.comtag:blogger.com,1999:blog-5460788270738656369.post-13813355235175580362009-07-30T02:43:58.403+08:002009-07-30T02:43:58.403+08:00In every economy, people spend their time doing on...In every economy, people spend their time doing one thing instead of another, make one thing instead of another, deliver things here instead of there. If you ask people why, they will talk about money, but the real reasons go deeper. Money was invented to help everyone keep track.<br /><br />Species were invented to help you keep track. It's a grave error to think they're any more real than money.Unknownhttps://www.blogger.com/profile/00831355954619691739noreply@blogger.comtag:blogger.com,1999:blog-5460788270738656369.post-35324613576786400472009-07-30T00:54:18.478+08:002009-07-30T00:54:18.478+08:00Are the mathematical concepts of metrics and metri...Are the mathematical concepts of metrics and metric balls applicable?<br /><br />A metric is a function which takes two objects as its arguments and returns the distance between them as a nonnegative real number. For example, an organism metric would quantify some sort of "distance" between two organisms.<br /><br />A metric ball is the set of all objects less than a certain distance from a "central" object. For example, the 1000000-ball centered at me in metric <i>d</i> is the set of all organisms, <i>x</i>, such that <i>d</i>(<i>x</i>, me) < 1000000. The radius of this ball is 1000000.<br /><br />The concept of a metric ball seems very similar to the concept of a typological, rank-based taxon to me. Type ≅ center and radius ≅ rank. The only differences are: 1) metric balls with different centers and the same radius can overlap, and 2) the type of a rank-based taxon is not necessarily "at the center".<br /><br />There may be ways of dealing with the differences. The question I'm interested in is, which metrics are 1) informative, and 2) practical?Mike Keeseyhttps://www.blogger.com/profile/00147156174467903264noreply@blogger.comtag:blogger.com,1999:blog-5460788270738656369.post-73036269988690743252009-07-29T19:06:47.877+08:002009-07-29T19:06:47.877+08:00First off, only one of the three "phylogeneti...First off, only one of the three "phylogenetic" species concepts is diagnostic (autapomorphic). The other is a lineage conception that is (usually) held to be monophyletic (not always, though), which I call the phylogenetic taxon conception. The third, rarely used, is the Hennigian conception in which species are interspeciation segments.<br /><br />As to asexual organisms, they only do not fall into species if you a priori define species as necessarily the outcome of a certain kind of process (reproductive compatibility). But maybe there are many kinds of species (Wilkins 2003 :-) )...<br /><br />And maybe there's an inverse relationship between gene exchange and ecological adaptation that explains why asexual organisms fall into clusters (Wilkins 2008)...<br /><br />Wilkins, John S. 2003. How to be a chaste species pluralist-realist: The origins of species modes and the Synapomorphic Species Concept. Biology and Philosophy 18:621-638.<br />———. 2007. The Concept and Causes of Microbial Species. Studies in History and Philosophy of the Life Sciences 28 (3):389-408.John S. Wilkinshttps://www.blogger.com/profile/04417266986565803683noreply@blogger.comtag:blogger.com,1999:blog-5460788270738656369.post-51230078427331401832009-07-29T17:13:21.278+08:002009-07-29T17:13:21.278+08:00John, I will accept your verdict of sloppy usage o...John, I will accept your verdict of sloppy usage of the word "hypothesis" with all due apologies. Perhaps a more accurate way to put it is that a species represents an observed pattern (as you said), and the <i>publication</i> of a species represents a prediction (is that more correct) that further observations will continue to fit that pattern? Anyway, the point I was trying to make was that any species identification is always open to challenge.<br /><br />I certainly don't see how a species could be an explanation, any more than "I am wearing a red shirt" is an explanation.<br /><br />Psi - phylogenetic species concepts don't have as much of a problem with asexual taxa as biological species concepts, because the PSC recognises a species as a diagnostic cluster. It's probably still not perfect, though, because depending on how you define "diagnostic" you could potentially end up with some <i>very</i> small species.Christopher Taylorhttps://www.blogger.com/profile/11075565866351612441noreply@blogger.comtag:blogger.com,1999:blog-5460788270738656369.post-74215863920326984492009-07-29T15:11:12.597+08:002009-07-29T15:11:12.597+08:00K, so what about the other 99% of life, which are ...K, so what about the other 99% of life, which are mostly asexual? =D<br /><br />They do seem to fall into more or less discrete patterns... perhaps reflecting stable points in the 'design space', but rigid pop gen definitions don't work very well there...<br /><br />My head hurts. Why does our brain insist on categorising everything to death? Seriously, as if learning about the whole infinite electron distribution cloud wasn't painful enough... XPPsi Wavefunctionhttps://www.blogger.com/profile/10829712736757471647noreply@blogger.comtag:blogger.com,1999:blog-5460788270738656369.post-57763919706512095432009-07-29T14:29:48.849+08:002009-07-29T14:29:48.849+08:00a species represents a hypothesis
No, I don't...<i>a species represents a hypothesis</i><br /><br />No, I don't agree. It represents an observed pattern. The hypothesis is that it is formed by such and so a process. The claim that all or most species are formed by that set of processes is a theory.<br /><br />Neither does a species represent an explanation, for the same reason (contra Fitzhugh):<br /><br />Fitzhugh, Kirk. 2009. Species as Explanatory Hypotheses: Refinements and Implications. Acta Biotheoretica 57 (1):201-248.John S. Wilkinshttps://www.blogger.com/profile/04417266986565803683noreply@blogger.com