TLre ancestry tf trout T that all species in that genus came from one classificatio",,",."**i,)'T:ffi:J 1T;1 common ancestral species. But we lack ur: tionary evidence in an attempt to arrange ambiguous criteria and all-encompassir: species on a family tree to denote branching definitions of the categories of classification points and degrees of evolutionary relation- Thus, a "lumper" may recognize two or threr ships. Tfaditionally, we have relied on skeletal species in a genus. A "splitter," using the sane features, anatomical characteristics, and the evidence but with different emphasis, mryi: type and arrangement of teeth for evidence. classify these same fish as two or three sub- Now, we also use more modern methods: species of one species. counting chromosomes, studying protein Controversies and disagreements regardin r patterns, and analyzing DNA. what classification scheme best reflects er-oiu- We assume that a change in a character, tionary relationships, or phylogenies, ari."e such as presence or absence of teeth on a from the fact that if the evidence used u. certain bone or on a particular part of a bone, inconclusive, it is open to individual interpre- denotes a branching sequence on the family tation. For example, the significance anc tree. Branching sequences then can be ar- magnitude of evolutionary divergence ,le- ranged in a system of classification by de- noted by a change in the size or shape of ; scending orders of relatedness. For example, bone, a change in chromosome number- the outer terminal twigs on the tree represent or a change in protein patterns might reflect living species, which are traced to a common a major branching classified as a genus or a stem branch that groups closely related branching of a lesser magnitude denotrnE species into a genus. Further down the tree, a species or even a subspecies. representing more ancient periods on the A primitive condition and an advanced o: geological time scale, branches of genera join derived condition must be established fbr to form subfamilies. Finally, the base of the each character. Otherwise the use of an)-' trunk represents the family. change in that character to denote the se- quence of branches is open to interpretation- Luuppns AND sPLrrrERS There is general agreement among modern Trrp raurr,Y TREB taxonomists that classification should reflect Uncertainry is prevalent when we try ro evolutionary relationships. That is, all species reconstmct the lineage ofthe family Salmoru- in the same genus should be more closely dae, because the fossil record is sparse and related to each other than to any species in contains large gaps. We rely on interpreta- other genera. And when we recognize a tions of the evidence from the characters u'c genus as a valid genus) we assume or denote use for classification. Tnor-r 3 SUBFAMILY GENUS SUBGENUS SPECIES z (,r r hen N gotbwcba nzrha tshawytvha hisutch m4301t Anrmhrwhus mlbiss Rainbow, cutthroat trout clarhi (Rh db drfarh or Pams a lnn ) tila chrysogaster salar trutta. .ischchon bmica matmmntus platycEhalus Salmoninae (Plnrysalrno) ohrilnnus -{lthough the oldest known salmonid fos- Acantholitgun :1. Eosalrno d.riftwoofunsis of British Colum- obtusirostris :ia. represents a species living about 45 to 50 Salmothlmus zetensis :rillion years ago, the origin of the family bwh :robably is much older, perhaps on the mag- Bmchymysaa saviwvi :rrude of 100 million years. We base this nature of the Huchen or rrimen (IIwho) Lisumption on the primitive hwho iieietal and anatomical characters of salmo- petYy, rd fishes in relation to other groups of mod- (Pamhurho) we have :rn bony (teleostean) fishes. What (Cristivomer) ,-arned from Eosohno fossils indicates that the rwrnaycush --:ree subfamilies of Salmonidae- Coregoni- (Bainw) fonrha.lis Chars &.lvehnus aae (the whitefishes), Thymallinae (gray- albus (&ltelinus) confhenws --ngs), and Salmoninae (trout, salmon, and ::rar)-were already separated from each bucomacnis malma . rher 50 million years ago. A g"p in the fossil nlpinus ::cord of about 25 million to 30 million years and others ccurs between the Eocene and Miocene Although all subfamily mem- :ns. Miocene fossils found in the western bers share certain physical also difer - nited States reveal that several major evolu- characteristics, they Jrom one another These --rnxrf branches of the subfamily Salmoni- kingdom Animalia (animals) diferences sepdrate them into :r.e were established by this time. These ex- phylum Chordata (animals with notochords and distinct gener a, sub gene r a, hollow nerve cords) :nct, fossil species represent the same genera species, and subspecies. Pacifc (animals backbones) subphylum Vertebrata with s almon ( genus O nc orhy nchus), species of trout, salmon, -: l'hich the living class Osteichthes (bony fishes) Atlantic salmon (Salmo) and :rd char are classified. Evidently, the first order Salmonifirrrnes (fishes with soft-rayed fins, chars (Salvelinus) are all clas' rajor branching, or divergence, leading to all adipose fins, and abdominal pelvic fins) sifed as Salmoninae subfamily (trout, salmon, char, whitefish, members in the species of trout, salmon, and char, is family Salmonidae family -',ing gnylings) Salmonidae, based on certain ;:naracterized by a loss ofteeth on the shaft of subfamily Salmoninae (trout, salmon, and char) phy sical similar itie s a mon g --:le vomer bone in the roof ofthe mouth and genera Owmhychus (hooked snout) them. They are further taxo- :.r a peculiar modification of lateral-line Solnn (silmon) n omic ally s ep dr ate d into Salvelinws (dwelling in springs) distinct gener 4, sub ge n er a, One branch leads to the chars of the -ales. species ryhiss, trula, fintinalis, etc. species and subspecies, on the !:nus Snlvelinus and also includes the lenok subspecies bwisi, boraieri, henshawi, etc. basis of the diferences among .: Siberia (genus Brailyrnystax) and Eurasian them. .:uchen (the largest living species of Salmoni- of the genus Hwcho). The other branch "e. trl-Har e Tnour Is 3 a E Although originally limited to of this divergence leads to the living species of subfamilies. We do not know whether this th e n or thern hemisph er e, trout and salmon. By the middle of the Mio- most ancient ancestor was freshwatcr Salmonid,s haye been success- a fully introduced into m(my cene period, the trout and salmon branch species or a marine species. AII species of parts of the southern hemi- forked again, resulting in two major groups. Salmonidae must spawn in fresh water. sphere. They inhabit cool and In the North Pacific basin of North America which would indicate a freshwater origin. cold waters; the Arctic char, a and Asia, one branch subdivided into two species member oJ the family, occurs But most also have the physiological further north than any other main evolutionary lines, one leading to capability to live in the ocean, which suggests freshwater ftsh. species of Pacific Salmon, the other to rain- that the ability to excrete salts and retain bow and cutthroat trout-all now classified water) necessary to survival in marine waters) in the genus Oncorhynchas. In the North At- has been inherited from an ancient ancestor. lantic basin of Europe, branchings of the There are some little-known, troutlike Sahno line gave rise to Atlantic salmon and species whose correct positions on the family brown trout and related species. tree are largely unknown, except that their The evolutionary line that developed per- branches belongin the subfamily Salmoninae haps I00 million years ago resulting in all of part of the tree. A peculiar species (probabll' the present species of trout, salmon, char, two species) classified in the genus Salrnothy- whitefishes, and graylings probably began lnus occ'Jrs in a few rivers on the Adriatic when the chromosome number doubled in a coast of Yugoslavia. The generic name im- common ancestral species. The chromo- plies that this fish originally was thought to somes of all species of the family Salmonidae be intermediate between trout (genus Snlrno contain about rwice the amount of DNA ofsubfamily Salmoninae) and gray'ing (genus found in related families such as the smelt Thyrnallws of subfamily Thymallinae). There family, Osmeridae. This indicates that the is no doubt that Snbnothywtws is a trout (sub- character change in the chromosomes of a family Salmoninae), but where its branching primitive ancestor occurred before the evolu- point joins the tree in relation to the Onco- tionary separation of the family into three rhynchws and Salyno branches is not clear. 4 Tnour 3a-sed on my interpretation of the evidence, In the genus SDbnl,I include six species of itituothyrnws should be connected to the varyrng degrees of relatedness. If the Tirrkish i"rinn branch. But others may disagee and ftotrt Plntysa.lwn platycephnlus is included as :-ace it further down the tree connecting to a one of the six species, there are three "good" . r*tnon ancestral stem before the separation species hghly divergent from one another- ,: rhis stem into Salm.o and Oncorhywhws. the Atlantic salmon, S. salor; the brown \nother species of dubious relationship trout, S. tn'r.ttn; and the Turkish trout, S. (P.) .,..urs onlyin Lake Ohrid, Yugoslavia, and is platycephalws. The other three recognized :-assified in the genus Acantholingon. This species are closely related to brown trout. In .:ecies formerly was classified in the genus some rivers tributary to the Adriatic Sea, the t'ritrntltyrnus, but there is little doubt that marbled trout) S. ma.rrnotatus, occurs. The -:;anthol'ingunshould be recognized as a sepa- marbled trout is a large predaceous fish reach- ::.re genus. Acantholhgcn ohridanws has a rng 23 kilograms (50 pounds) or more. Its .:leltlike appearance and has the most primi- coloration and markings differ greatly from :-!'e type of skeletal characters and dentition those of other species of Sahno.