The Birth and Fate of New Generic Names
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THE BIRTH AND FATE OF NEW GENERIC NAMES D Jean Lodge & Andrus Voitk No student of natural history can have escaped the proliferation of new names in the last few decades, certainly evident in mycology. Of course, the most obvious need for a new name comes about when an organism is discovered whose existence was hitherto unknown, i.e. a species, genus, or larger group new to science. However, for the layman the sudden profusion of new names for seemingly old organisms or groups of organisms is causing some confusion and consternation, particularly when several names replace a former single name. In this discussion we shall use genera as an example to show how new names (new genera) come about and what happens to them after introduction. In order to understand the organisms aside). Phylogeny supported Harmaja’s one, new branches appear. Signifi cantly with which we share this world, we observations, lending more weight to divergent new branches may be have tried to classify them, putting his decision to consider them different considered separate entities and given like with like in the belief that likeness genera. Hence, it is likely that more a new genus name, or they might be indicates relatedness. It follows that taxonomists will accept the derived recognized at a lower rank such as when we fi nd consistent differences genus Cystodermella. If its use becomes subgenus or section. A prolifi c amount between organisms, in order to accepted practice, Cystodermella will be of molecular genetic investigation keep like with like we also separate considered a good genus in the sense is discovering much unsuspected out differing groups. An example that it is generally accepted as standing branching within groups, i.e. new of this process was provided in a apart from its original “parent” genus, potential derived genera. This is why so recent OMPHALINA article devoted Cystoderma. many new names are proposed. 1 to Cystoderma. Careful study of the In mycology there are no absolute Now that we know how such names genus Cystoderma led Harri Harmaja criteria that must be met to designate come about, let us see what their to conclude that it contained two a new genus. Every taxonomist is free fate is. As an example, let us consider different groups of mushrooms, to describe observed differences— the previous article, where one of us those with amyloid spores and those macroscopic, microscopic, ecological, (DJL) describes the derived genera 2 without. To him these differences were chemical or phylogenetic—and she and her coworkers supported suffi ciently signifi cant to warrant placing propose a derived genus with a with molecular phylogeny in the each in its own genus. This was done by new name. Phylogeny has, however, former genus Hygrocybe. Excluding leaving the mushrooms with amyloid certain guidelines. Since the aim is to Cuphophyllus, they supported six spores in the original genus Cystoderma, lump like with like, a genus should be derived genera of which only one was and creating a new derivative or monophyletic—that is, “pure”; it should ‘new’. Since there are no absolute segregate genus, Cystodermella, for not contain other genera within it (that criteria for naming new genera, this the species with inamyloid spores. would make it polyphyletic). Thus, new becomes an active decision of each Not all taxonomists agreed that this genera are proposed when a genus is taxonomist. As with all decisions, there difference was suffi cient to justify the found to be polyphyletic, i.e. contain is judgment and opinion involved, rank of a new genus, and therefore within it one or more other genera. both of which may vary with different some continued to use the genus At the same time, new genera cannot observers. This means that there are name Cystoderma for both groups. be created within existing genera, but choices, fi rst for the investigator and Saar studied the molecular phylogeny must stand on their own. second for the users. To explore these of these mushrooms and discovered choices, we chose Figure 1, adapted that phylogenetically the amyloid- Current taxonomy is based on phylogenetics, comparative analysis from that article, but pared of individual spored group and the inamyloid- species, and trimmed of all branches spored group have travelled along of genetic regions. The results can be illustrated by clade trees that not pertaining to Hygrocybe, as it has different evolutionary pathways from been known in its wide sense for the 3 trace the likely evolutionary path and a common progenitor. In other last few decades. The branch that leads words, the two differ genetically, as show the relation of genera to each other—snippets from the Tree of Life. us to this group is A, arising from the well as in the ability of their spores root. to react to Iodine (rare exceptions When genetic differences are found within genera previously thought to be Let us fi rst deal with the genus 8 OMPHALINA Cuphophyllus, shown on branch X. rise off the B-X axis—the others have the only reasonable option seems to Lodge mentioned that its acceptance just been removed in our illustration be to accept Cuphophyllus as a good as a good genus apart from Hygrocybe for simplicity. As mentioned, if we wish genus. was unavoidable. At one time species to consider all the illustrated genera as Now, let us turn to Branch B. It of Cuphophyllus were considered one large genus, we need to include all splits into branches C and D. To part of the larger genus Hygrocybe. the intervening genera as well and the our knowledge, there are no other However, Lodge’s article (see the name would have to be Hygrophorus intervening branches, so that one phylogeny diagram in that article) rather than Hygrocybe as it is the oldest valid option is to consider everything presents phylogenetic evidence that genus name in that group. That would on these branches as one genus. This the entire genus Hygrophorus, as well as create a very large genus, containing produces a genus not too dissimilar the smaller genera of Chrysomphalina, very many discrete groups that differ from one earlier version of Hygrocybe, Lichenomphalia, Arrhenia, Cantharellula signifi cantly in appearance, lifestyle and when most of what is now known as and Pseudoarmiraliella come between genetic make-up. For most people this Cuphophyllus was considered a separate branch X and Branch B. In other words, is not a useful grouping of like with like. genus, at that time called Camarophyllus. B and X are not the only branches that Therefore, with the current information This concept of Hygrocybe has worked Hygrocybe Neohygrocybe Porpolomopsis Humidicutis Gliophorus Chromosera Gloioxanthomyces Cuphophyllus OMPHALINA 9 are chemically unrelated and give the species in branches E and F very different appearances. These considerations may infl uence you to separate genetically unlike groups. If you decide to separate E and F, you are automatically accepting Neohygrocybe as a valid genus. Your decision then is what to do with branch H. You may lump all into one genus (Gliophorus, named in 1958, which has priority over Humidicutis named the following year in 1959, and the limits of the Same phylogram as on the previous page, genus would have to be expanded so that you can follow the text without to absorb Gliophorus species). If not, having to fl ip pages. you automatically accept Gliophorus as valid. Your last decision is whether to lump Porpolomopsis and Humidicutis, or accept both as valid genera. Each branch is well supported but the split that separates the two branches is not statistically signifi cant, and they are morphologically similar. If you have come this far, why not go for broke and in the pastpast, and mamay contincontinue e to do a lot of value al e on ssuch ch fi ndings,ndin s you o accept these as valid genera as well? so. However, Lodge and coworkers would likely support distinguishing Should you reject this split, you would have demonstrated a split of branch between the two genera. You could join several mycologists who previously B into C and D. Branch D has good summon support in the different placed species of the younger genus, statistical support (indicated by a thick habitat and looks of the two genera. Porpolomopsis, in the older of the two line), which means that the likelihood is Gloioxanthomyces has a gelatinized named genera, Humidicutis. The type over 70% that this genetic separation is gill edge, similar to Hygrocybe laeta species of Porpolomopsis (Hygrocybe a consistent or “true” fi nding. Because (Gliophorus laetus), but the cells that calyptriformis) has never been placed in we can also identify other consistent make up the fl esh are distinctive. Humidicutis but was thought to belong differences between the genera on Or you may opt to continue to Hygrocybe in branch E because it’s branch D and those on branch C, considering differences in species of conical pileus with a splitting margin you may decide to acknowledge this Gloioxanthomyces and Chromosera as resembles that of Hygrocybe conica difference, in order to keep like with minor, concluding that such differences (the type species of Hygrocybe). like. are reasonable between otherwise H./P. calyptriformis would need to be If you opt to accept the split, your similar species within one somewhat transferred to Humidicutis in order to next choice is to decide what to do diverse genus. Note that branch D is recognize the entire branch I as a single with the genera on branches C and a sister to C, containing all the other genus. genera. Therefore, you can lump D. Both are independent branches, so Among this confusing profusion of branches K and L or choose both, but that a decision on one does not affect permutations and combinations, three not select only one.