Systematic Zoology

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Print ISSN: 0039-7989
The generic name Ichthyosporidium Caullery and Mesnil, 1905, was created for two original species. One of them was probably a fungus and the other a protozoan, but neither was ever designated as type-species. In subsequent studies this name has been applied by some authors to organisms known to be fungi and by other authors to quite different organisms which are generally conceded to be protozoans. In this study the protozoan originally included in the genus, 7. phymogenes, later corrected to I. giganteum (Thelohan, 1895) Swarczewsky, 1914, is selected as type-species and the generic name is thereby reserved for the protozoans. The other original species, I. gasterophUum C. and M., 1905, is transferred to genus Ichthyophonus Plehn and Mulsow, 1911.
Evidence is presented for the thesis that a taxometric analysis using haphazardly assembled, equally weighted characters results in a haphazard classification, at least in the Basidiomycetes. We consider that not all characters, in the currently accepted sense of that word, contain equal amounts of phylogenetic information, and that a proper taxonomic value can be placed on each character only if its degree of conservatism within the group is understood. So far, not only has it been impossible to instruct a computer to take conservatism into consideration, but also the limitations of the taxonomist's knowledge about homology and analogy in the fungi restrict his ability to designate characters in taxometric terms.
Species of birds sympatric on islands frequently differ from each other in bill length by a larger amount than do their mainland relatives. Differences between similar species in body size, as indicated by wing length, are smaller than differences in bill length. This suggests that a major adaptation of island birds to potential competitors is a change in feeding habitats. An alternative explanation of the bill features of island birds, that they have been selected for a species recognition function, may be applicable in some instances. But since pairs of species are usually different in plumage features, as well as song and behaviour, species recognition is probably achieved most frequently by these means and not by bill size or shape. Some data show that homogeneric species differ in numbers by a greater amount on islands than on the mainland. Differences in numbers and bill characteristics support the suggestion that for sustained coexistence the requirement of mutual ecological independence of closely related species is often greater on islands than on a mainland. This results from the restricted variety of resources and area of islands.
Wilkinson, Chris. (Department of Biological Sciences, Portsmouth Polytechnic, U.K.) 1970. Adding a point to a principal coordinates analysis. Syst. Zool., 19:258–263.—A new numerical method is given which is of value to taxonomists. It enables further species to be added to a previous principal coordinates analysis in order to find their phenetic relationships with the original set of species.
Chromosome numbers are reported for 30 species representing eight families of anurans. These, together with previously published records, provide some evidence of trends in numbers of chromosomes at the family level. With the exception of two genera of leptodactylids, diploid numbers range from 20 to 36 and haploid numbers, from 10 to 18 in anurans studied to date.
The relationships of 42 Canadian species of the mosquito genus Aedes were investigated by numerotaxonomic techniques, using the method of matching coefficients. Good agreement with conventional taxonomic arrangements was found when (1) adult mosquitoes and (2) adults and larvae together were considered, but with (3) larvae alone, the agreement was unsatisfactory. The prospects of numerical methods in taxonomy are briefly considered.
Sarich, Vincent M. (Dept. Anthropology, U. Calif., Berkeley 94720) 1969. Pinniped origins and the rate of evolution of carnivore albumins. Syst. Zool., 18:286–295. [Immunology; albumins; pinnipeds; phylogeny; evolution].—Data resulting from an immunological study of relationships among fissiped and pinniped albumins show that albumin evolution has occurred in a regular fashion in these taxa. This finding allows the conclusion that the pinnipeds share much more recent common ancestry with the canoids than either group does with the feloids. It is pointed out that it now appears possible to develop an internally consistent quantitative phylogeny for a group of species through the immunological study of a single protein found in that group.
Small specimens can be stored safely in vials, tightly stoppered with cotton and placed upside down in a larger jar. Due to the unavailability of tight jars, methods used in several institutions to prevent alcohol loss have been tried out. Either plastic tape (3M no. 472) or dipping in plastic coating (Uniroyal Adhesive no. 6273) appreciably slows evaporation. Seventy to eighty per cent alcohol is the best preservative; 40-70% isopropyl alcohol seems an excellent substitute, and is easily obtained. Methods of reconditioning dried specimens are controversial. All locality labels should be typed or mimeographed or the labels can be photo-offset, or Xerox copied on good bond paper.
In female Tetraopes tetraophthalmus there is significant heterogeneity in allometric growth ratios of prothoracic tubercle size and prothorax width among different areas of the range. This suggests that different relative growth rates in the formation of the adult prothorax may have been selectively favored in different areas of the range. However, males do not show the effect. Furthermore, the relationship between individual and population allomorphosis is also strikingly different in the two sexes; estimates of growth ratios at these two levels are similar in females, very dissimilar in males.
-Haploid karyotypes (c-metaphase) of S. clarki (above; UAZ No. 16238) and S. magister (below; UAZ No. 16233). Note the abundance of uniarmed chromosomes in clarki, accompanied by a high number (n = 20), in sharp contrast to the abundance of biarmed chromosomes in magister, accompanied by a low number (n = 13). Lines represent 10 IA. 
-Haploid karyotypes of S. magister (left chromosome of each "pair") and S. clarki [right chromosome(s) of each "pair"] with the chromosomes of clarki arranged to demonstrate how centric fusion of particular elements could have resulted in derivation of the karyotype of magister. Chromosomes illustrated here are the apparent homologues (from the same cell of each species) of those illustrated and correspondingly numbered in Fig. 1. Disparity in centromere positions in the largest "pair" (upper left) suggests that centric fusion was followed by an unequal pericentric inversion. 
Karyotype evolution apparently involving Robertsonian centric fusion of chromosomes in iguanid reptilian species (Sceloporus clarki and Sceloporus magister) is consistent with the recent evidence pertaining to the evolution of North American Desert species of animals and plants derived from tropical and subtropical communities of the Madro-Tertiary Geoflora during the evolution of the North American Desert.
Qualitative identification and quantitative estimation both of aromatic biogenic amines and pharmacologically active polypeptides in the skin of amphibians appear to offer a valuable contribution to studies in taxonomy and evolution of this vertebrate class. Several examples of the accordance of the biochemical data herein reported with the data of traditional taxonomy are described for the neotropical family of frogs Leptodactylidae, but particular emphasis is laid on the striking correspondence between the systemic distribution of the spectra of biogenic amines and morphological taxonomy which is demonstrated by the species of the genus Leptodactylus.
Fitch, W. M. (Dept. Physiological Chetn., U. Wisconsin, Madison 53706) 1970. Distinguishing homologous from analogous proteins. Syst. Zool., 19:99–113.—This work provides a means by which it is possible to determine whether two groups of related proteins have a common ancestor or are of independent origin. A set of 16 random amino acid sequences were shown to be unrelated by this method. A set of 16 real but presumably unrelated proteins gave a similar result. A set of 24 model proteins which was composed of two independently evolving groups, converging toward the same chemical goal, was correctly shown to be convergently related, with the probability that the result was due to chance being <10−21. A set of 24 cytochromes composed of 5 fungi and 19 metazoans was shown to be divergently related, with the probability that the result was due to chance being < 10−9. A process was described which leads to the absolute minimum of nucleotide replacements required to account for the divergent descent of a set of genes given a particular topology for the tree depicting their ancestral relations. It was also shown that the convergent processes could realistically lead to amino acid sequences which would produce positive tests for relatedness, not only by a chemical criterion, but by a genetic (nucleotide sequence) criterion as well. Finally, a realistic case is indicated where truly homologous traits, behaving in a perfectly expectable way, may nevertheless lead to a ludicrous phylogeny.
Nomenclatural procedures in animal taxonomy, especially the application of priority rules in the vast entomological literature, are oppressively inefficient and becoming more so with the passage of time. The authors suggest that the problem be solved in a simple but radical way, by the device of officially recognizing selected monographs as the "new Linnaeus" of the group treated by the monograph. No publication prior to the monograph could then affect nomenclatural usage in the group, but a new monograph could supplant it.
Antitropical distributions of continental shelf, Indo-West Pacific species are probably not due to transgression of the tropics during the glacial periods, isothermic submergence, island integration, rising Neogene temperatures, or the Mesozoic dispersal of fragments from a Pacific continental mass. Characteristics of common antitropical patterns, plus information from systematic works on a variety of animal and plant groups, indicate that the long discarded “relict theory” of Théel (1885) appears to best fit the evidence, for it provides a mechanism whereby antitropical distributions may be brought about. The relict theory is compatible with the concept that the East Indies part of the Indo-West Pacific has been functioning as a center of evolutionary origin. It suggests that antitropical and associated disjunct patterns are produced as an older species, that has spread out to occupy a broad range, loses ground and gradually becomes supplanted by a younger species that had subsequently evolved in the East Indies. As this process goes on, the older species becomes restricted to a few isolated localities on the fringe of its original range. These isolates are often found to the north and south of the equatorial region but may include relict populations at the western edge of the Indian Ocean.
Louis Agassiz was under the false impression that the shells of brachiopods were lateral in position and that the group was related to mollusks. N. S. Shaler considered the shells to be anterior and posterior in position. E. S. Morse proved that the shells are dorsal and ventral, and showed that brachiopods form a distinct group somewhat related to tubicolous annelids. Journal records of Morse give historical sidelights which illuminate his controversy with Agassiz. Morse's classification of Brachiopoda became one of his principal contributions to zoology.
Schnell, Gary D. (Dept. Zoology, Univ. Oklahoma, Norman, Okla. 73069) 1970. A phenetic study of the suborder Lari (Aves)/II. Phenograms, discussion, and conclusions. Syst. Zool., 19:264–302 [Phenetics; numerical taxonomy; multivariate; Lari; cluster analysis].—Phenetic affinities of the 93 species of skuas, gulls, terns, and skimmers in the suborder Lari (Charadriiformes: Aves) are described in detail. Methods and materials, as well as the results of principal components analyses, were given in Part I (Schnell, 1970). In this paper the 18 phenograms resulting from the use of different character suites (51 skeletal, 72 external, and both combined), transformations, and clustering methods are presented and analyzed. A classification of these resulting classifications (clustering basic similarity matrices or cophenetic values on the basis of correlations between classifications) is used to indicate which methods and character suites give similar results. The phenograms have also been compared with the classifications of Peters (1934) and Moynihan (1959) for the Lari. For analyses that included suites of highly correlated characters, correlation matrices were found to be relatively more robust than distances, being affected less by transformations or the use of different character suites. Also, when particularly divergent classifications occurred, this was partly due to divergent basic similarity matrices, but the clustering procedures added additional differences. The placing (or forcing) of OTUs into a hierarchical system of clusters (rather than just analyzing basic similarity matrices) resulted in an indication of relationships between OTUs more in accord with the opinions of previous workers, who also represented relationships in a hierarchy. The determination of the “best” overall phenetic classification, for use when one is in need of a single measure of similarity, is discussed and a set of guides is suggested to aid in the selection of such a classification. Some cladistic speculations are given and the relative positioning and stability of clusters is discussed. When analyzing data with high correlations between characters, the use of adaptive hierarchical clustering schemes that take into account possible trends in variation found within clusters is strongly recommended, and the value of multiple classifications to represent affinities is stressed. Principal component models, where no assumption is made that OTUs must fall into clusters, were particularly useful in representing relationships. The analysis of external characters resulted in phenograms that showed some similarity to those based on skeletal measurements. However, there were significant differences, indicating support for only a weak version of the nonspecificity hypothesis. A morphological description, using numerous characters, should be particularly valuable to current and future workers conducting various types of comparative studies (e.g., behavioral, ecological) within this taxon. It seems obvious that accurate and detailed morphometric description at the interspecific level is as important in the sound development of evolutionary theory as quantitative studies of intraspecific (e.g., geographic) variation.
Immunologic analyses of serum proteins, studies of karyotypes, and morphology of spermatozoa reveal that vampire bats (family Desmodontidae) are more closely related to members of the family Phyllostomatidae than is suggested by conventional morphological characters. Immunologic tests show Desmodus to be related to the Phyllostomatidae through the subfamilies Phyllostomatinae and Glossophaginae. When fundamental and diploid numbers of chromosomes are plotted, two monotypic desmodontid genera (Desmodus and Diaemus) have karyotypic values that fall in the area of highest concentration of phyllostomatids. Spermatozoa of Desmodus and the third monotypic desmodontid genus, Diphylla, are indistinguishable in general morphology from those of representatives of five subfamilies of phyllostomatids. It is suggested that the vampires may represent only a subfamily of the Phyllostomatidae.
Geophysical maps depicting continental movement have consistently shown India, as it moved northward, to be located far out in the Tethys Sea. India split off from the African east coast about 148 m.y.a. From that time onward, according to almost all geophysical accounts, India was isolated from all other continents until the early Miocene when it made contact with Eurasia. But the biological data, both fossil and Recent, indicate that this concept cannot be correct. If India had really existed as an isolated, oceanic continent for about 100 m.y., it should have developed a peculiar biota with many endemic genera and families in its terrestrial and shallow marine habitats. But there are virtually no remains of organisms indicating that India was isolated for any substantial time (millions of years). Instead, we find that almost all Indian taxa were possessed in common with other continents. As time went on, the northern relationships became stronger and the southern ones weaker. Most of the recent geophysical accounts show India not making contact with Eurasia until the early Miocene, but fossil materials show that this event must have taken place by the early Eocene. It has been postulated that, as India moved northward, it created a biogeographic barrier that separated marine fish populations and resulted in the east-west provinces that are now apparent in the Indian Ocean. At the same time, the barrier effect was supposed to have resulted in the formation of sister species that are now located far apart. Information currently available indicates that most living, tropical marine species are probably not over 3 m.y. old. Consequently, the northward movement of India, which took place primarily between 148 and 50 m.y.a., could have no bearing on the relationships of modern species.
Inglis, W. Grant (South Australia Museum, Adelaide, Australia) 1970. The purpose and judgements of biological classifications. Syst. Zool., 19:240–250.—Biological classifications are judged by assessing their predictive value against the co-variance of character-states in organisms not previously studied or against the classification of some character-states not previously studied in the organisms classified. As a corollary, taxonomists, judging by their published work, aim to produce that classification which maximises the concordance of the classifications of single characters or, put another equivalent way, which maximises the character correlations of the organisms being classified. Such classifications are then assumed to be inductive and, therefore, predictive and this predictive content is tested. It is argued that the sole operational aim of taxonomy is the production of maximally concordant, and so predictive, classifications which can be explained by the fact of evolution. The reversal of this explanatory role wherein it is claimed that phylogenies can be studied by erecting such classifications has obscured rather than clarified discussion of classification. It is further argued that because all the characters in a given organism are not correlated some weighting of characters is inevitable in producing general classifications and that the taximetric approach has obscured the discussion of classification by erecting a series of axioms which make the testing of any classification depend upon the method by which it was constructed rather than upon the form of the classification itself.
The general structure of taxonomic data sets, the alpha and beta elements of this structure, the departures of this structure from randomness, and the rationale by which departures are viewed as historical evidence have been demonstrated. An operational method for selecting character sets is illustrated, an estimate of the genealogy that produced the species is derived from these sets, and this estimate is presented as a phylogeny In addition, I have demonstrated a method that discloses a stable structure that is relatively insensitive to distortion through addition of new data. Still further, I have shown a procedure that produced clusters of species having phenetic properties that are at least as good as those of clusters produced by direct phenetic methods. It has been demonstrated that different characters have different predictive properties, that different character states of the same character have different predictive properties, and that, in general, derivative states are the sole bearers of valid historical information. Taxonomists cannot, with propriety, weight either characters or character states. They must select and evaluate sets of character states, and this evaluation should be carried out every time new data, breaking established character sets, are incorporated into data tables.
This paper consists primarily of an inquiry into the logical status and the epistemological role of nomenifers (literally, “name-bearers” type specimens). The three major codes of biological nomenclature are ambiguous or misleading or equivocal regarding nomenifers, as evidenced by varying interpretations given by different writers. One important issue which can be isolated is the following: if, as the codes and some writers say, the name is “attached” to the nomenifer, it would seem that the name is a proper name. To know the proper name of a nomenifer would be quite useless scientifically; the practices of biologists would be inconsistent with such a view, since class names are needed for science. To clarify this distinction, the differences between class (common, general) names and proper names are examined. There are at least two differences: proper names name individuals and have no intension; class names name groups (or classes) and have intension. A second difficulty, namely, the difference between attaching a name to a description (a set of words) or to an organism (or class of organisms), is pointed out. A further issue, brought out by noting several writer's views, is the unsettledness regarding whether a type specimen must be typical of its species or only an example of its species. Yet another issue, the alleged diremption between nomenclature and taxonomy, is considered with the conclusion that a total separateness does not exist. Our own view of the epistemological role of the nomenifer is that it, like any other member of the species, can serve to ostensively define the name of the species; the nomenifer is different only in being the “official” instance of the species named by the original investigator and, as such, is required to be included in whatever group is called by that name. Consequently, the nomenifer has no privileged logical status; it is a member of a class like any other member of that class. It bears a name by virtue of its membership in the class but, unlike other members of that class, its name cannot change as long as there is a class with that name.
Chromosomes from 14 species representing the six subgenera of the ground squirrel genus Spermophilus are evaluated as indicators of taxonomic relationships. The diploid number and karyotype of S. franklini (2n = 42), subgenus Poliocitellus, are described here for the first time, together with supplementary chromosomal characters from S. beecheyi (2n = 38) and S. variegatus (2n = 38), subgenus Otospermophilus, and S. lateralis (2n = 42), subgenus Callospermophilus. Chromosomal characters are diagnostic at the subgeneric level in Poliocitellus, Otospermorphilus, Xerospermophilus, Callospermophilus, and Ictidomys. The subgenus Spermophilus cannot be differentiated at this level because of a striking degree of interspecific variation (2n = 30-46). An evaluation of possible mechanisms for karyotype evolution within the genus Spermophilus provides additional taxonomic data. The subgenera Ictidomys and Poliocitellus appear to share an equally close chromosomal relationship to Spermophilus. Because more complex chromosomal rearrangements must be postulated to explain the differences observed between Callospermophilus, Otospermophilus, and Xerospermophilus greater evolutionary divergence may exist between these taxa than between Ictidomys, Spermophilus, and Poliocitellus.
The obstacles which have prevented the haplosporidans from fitting into the classification prepared by the Committee on Taxonomy and Taxonomic Problems of the Society of Protozoologists have no objective basis but are essentially semantic in nature. The resemblance between the different kinds of filaments in spores is largely verbal. Therefore, the notion that the presence or absence of a "filament" is the essential character for segregating different groups of sporozoans into subphyla should be rejected. Then, if the subphylum names Sporozoa Leuckart, 1879, and Cnidospora Doflein, 1901, are replaced with the appropriate ones, Rhabdogena Delage and Herouard, 1896, and Amoebogena Delage and Herouard, 1896, all obstacles to putting the order Haplosporida Caullery and Mesnil, 1899, into a satisfactory position are removed. Likewise, it then becomes logically possible to put the order Paramyxida Chatton, 1911, into the classification. Accordingly, these two orders are placed in subphylum Amoebogena, in classes Microsporea Corliss and Levine, 1963, and Myxosporea Butschli, 1881, respectively. The latter class, having two groups of orders which are in sharp contrast to each other with respect to structural complexity, is here divided into two subclasses, Myxosporia Butschli, 1881, (with orders Myxosporida Butschli, 1881, and Actinomyxida Stolc, 1889) and Paramyxia (with orders Paramyxida Chatton, 1911, and Helicosporida Kudo, 1931). It is suggested that the older name Sporozoa Leuckart, 1879, be used (after appropriate change of ending) to replace the class name Telosporea Schaudinn, 1900, and that the latter be discarded.
Immunological comparisons of beetles involving 66 species from 24 families were made by photodensitometrically measuring the precipitin zones that developed in agar-gels. Comparisons at the intrageneric and intergeneric levels were most suitable for study using the photodensitometric technique, and results obtained at these levels agreed with predicted results based on morphological studies. Unusually high immunological correspondences of Melanotus (Family Elateridae) and Oryzaephilus (Family Cucujidae) to Tenebrio molitor suggested previously unsuspected relationships. The high degree of reciprocal correspondence between members of the families Cerambycidae and Chrysomelidae indicated that relegation of these families to subfamilial status would be reasonable. An interfamilial cluster analysis revealed systematically useful data.
Immunological precipitin tests were used to determine relative serological propinquity of four subgenera of Spermophilus (Otospermophilus, Callospermophilus, Spermophilus, and Ictidomys). Serum from another sciurid genus, Sciurus, was cross-reacted with antiserum against each of the subgenera of Spermophilus.
A method of equalized scaling is proposed for taxonomic or classificatory systems, designed so that problems involving a mixed set of variables (some quantitative and others multistate qualitative) can be handled automatically and so that variables of neither class will unduly dominate the classifying process. The method is formulated in terms of Euclidean distance in n-dimensional space but is easily adapted to a system using similarity coefficients. Other advantages of the method are discussed.
Evolution is neither an autonomous sequence of spontaneous organic changes nor a predictable chain of unalterable reactions of organisms to their environment and its changes; hence ecological factors are neither just the background for evolution nor do they determine it directly and unequivocally. The contribution of ecological factors to the timing and the direction of evolution depends upon the role they assume, or are allotted, in the life history of the species in question. The adaptation of species to momentary relationships with their particular environments may preadapt them to the establishment of new ecological relationships, Preadaptation is achieved when new or even existing components of the organism's environment acquire additional or totally novel roles in the ecological niches of these organisms, i.e., when the organism interacts with parts of its environment in new and different ways. The exploitation of the evolutionary opportunities emerging from the interaction between organic and environmental diversity involves both chance and choice. The central role of behavior permits the element of choice; the importance of choice in evolution increases with increasing complexity of animals and their behavior. The role of ecological factors in evolution must be investigated by clarifying the multiple feedback relationships between structure, habit, and habitat.
The practical application of electrophoretic analyses of proteins of mammalian sera and hemoglobins by simple methods is described. Twenty–five taxonomic relationships, most of which have been controversial, are reviewed, and decisions based on blood proteins and hemoglobins are given. In 19 instances clarifications of relationships were obtained, but in 6 instances the proteins did not help.
The process of natural selection operates at the population and species levels, but its effects are seen at all levels of organization. Directional selection is the primary mechanism for changes that result in the evolution of higher levels. The effectiveness of natural selection can be measured by three types of evolutionary rates: taxonomic, morphological, and biological (species origin). The most useful rate is that of species origin, which can be compared with rates obtained from experimental or mathematical models. The rates computed from the fossil record of many Pleistocene mammals are higher than those derived from models. The history of several well-known vertebrate lineages clearly demonstrates that higher levels of organization evolve by means of microevolutionary processes rather than by special genetic and selective mechanisms. Phenotypic variation observed in phyletic lines does not give a direct index of the genetic variability underlying the phenotype.
The transition from one higher level of organization to another always involves some form of biological improvement for the same or a new way of life. Except in rare cases when a single lineage attains a new level, the transition is expressed in terms of similar adaptations (broad adaptations) that evolve more or less in parallel in lineages of common ancestry. Within the limitations imposed by ancestry, canalization and directional selection, experimentation with various combinations of primitive, intermediate, and advanced characters will lead to both niche adaptation and to broad adaptation. Broad adaptations may evolve at different rates and times in related lineages, but they are, in effect, responsible for the recognition of a higher level. The partly opportunistic nature of this process implies that these lineages will approach or enter a new level with varying degrees of success. A particular higher level of organization may therefore have a multiple origin even though it has a monophyletic origin at a particular lower level.
A rearrangement of Orders, Suborders, Families, and Subfamilies is essayed for those Sarcodina of the Superorder Lobida, as included in the Subclass Cyclia, Class Hydraulea, within a classification for the Sarcodina based on mechanisms of movement. The genera included are listed with the designation of each familial group; but the families are not given names. The problem of naming families, using those within the Lobida as examples, is discussed, with emphasis on the need to use logic, whether or not the International Rules of Nomenclature provide for or permit it. An example is given of the confusion sometimes occurring due to impedance of logic by the rigidity of rules. Some other difficulties are considered. It is concluded that the extension of the Rule of Priority to include names of family groups imposes a rigidity of mental behavior which is often counter to logic in the naming of families, especially new ones based on new approaches and/or new data. It is further concluded that the Rule of Priority cannot be supported by the authors for any familial group or higher taxon.
Crusafont-Pairo, M. and S. Reguant (Chair of Paleontology, University of Barcelona, Spain and Instituto Jaime Almera, C. S. I. C, Barcelona, Spain) 1970. The nomenclature of intermediate forms. Syst. Zool., 19:254–257.—An open nomenclature is proposed for intermediate forms, especially those situated between two successive species, which indicates both between what species said intermediate forms are found and their sequence in the evolutionary line. This makes unnecessary the creation of waagenons or successional subspecies in continuous phyletic lineages
Contemporary population and developmental genetics sees no problem in finding mechanisms adequate to effect a change from one level of adaptive organization to another. Natural populations contain sufficient genetic variability to respond to directed selection for a change in the mean of almost any character. Such responses usually come by the accumulation of small increments and can be attributed to shifts in the frequencies of different alleles in polygenic systems. The extent of the response to persistent selection depends on whether the remainder of the genome adjusts to include the new mean in an integrated whole. The greater the change and the more fundamental the reorganization, the lower the probability of occurrence. Hence the prediction of such events with any degree of precision presents difficulties close to insuperable.
The northern form of the common grackle, Q. q. versicolor, mhabiting pine forest and mixed pine-hardwood forest, ranges south in Louisiana to the latitude of Baton Rouge, Opelousas, and De Ridder, where it interbreeds freely in a narrow zone with the southern form, Q. q. quiscula, inhabiting cypress-tupelogum swamp forest and coastal marshes, to produce viable and fertile hybrids. Analysis of geographical variation in four color characters in 637 males from 21 sample areas in Louisiana and the application of discriminant function analysis to form a weighted hybrid index demonstrate that a complete transition in color characters between Q. q. versicolor and Q q. quiscula occurs between 30⚬ and 31⚬ N latitude. Populations of the northern form are only slightly introgressed with genes from Q q. quiscula, whereas those of the southern form are heavily introgressed with genes from Q. q. versicolor Geographical variation in characters of size is smoothly clinal, lacking the step-cline feature seen in characters of color. The position and width of the hybrid zone in Louisiana is related to the pattern of distribution of the major vegetation types. Where the mixed pine-hardwood habitat of Q q. versicolor contacts the cypress-tupelogum habitat of Q q. quiscula, the zone is 15 miles wide, but it widens to 40 miles where the two habitat types are separated by areas of disturbed bottomland hardwood forest. A comparison of morphological variation in material taken in the period 1890-1942 with that taken in the period 1962-1965 demonstrates that, since the 1930's, the zone of hybridization in Louisiana has shifted northward approximately 20 miles. Apparently the northward shift was not accompanied by a change in the width of the zone. In the absence of evidence of the functioning of reproductive isolating mechanisms, the extraordinary narrowness and temporal stability of width of the zone of hybridization can only be explained in terms of the hybrid inferiority hypothesis.
A factor analysis with a Varimax rotation of the initial solution was applied to a system of 27 dental and cranial measurements in the house mouse. Five common “factors” were identified with respect to the 27 variables. These factors in decreasing order of their contribution to the total variation, were width, anterior length, posterior length, skull and M3. The proportion of the total variance accounted for by the total communality was 73.99%.
Kirsch, J. A. W. (Department of Zoology, Univ. Kansas, Lawrence, 66044) 1969. Serological data and phylogenetic inference: the problem of rates of change. Syst. Zool., 18:296–311 [Immunology; cladistics, phylogeny, evolutionary rate; Marsupialia].—Inferences about the evolutionary history of a group based upon studies of its living members can only be made utilizing assumptions about evolutionary rates. One such assumption current among biochemists and serologists is that biochemical evolution has been steady and the same in all lineages. If this were so, cladistic relationships could easily be inferred from phenetics. The assumption of strict time-dependency may be interpreted either as a deterministic or as a stochastic statement. In the former case, the form of phenetic groups is logically determined in ways incompatible with the results of serological studies; this is illustrated by examples from the comparative serology of marsupials. A simple computer model for the evolution of a group of hypothetical taxa of known phylogeny, operating according to the rules of a stochastic interpretation of time-dependency, generates data about those taxa very like empirical data on marsupials. However, the inferred cladistics of the hypothetical group are incorrect in many details, and this is indicated by the incompatibility of phenograms representing the affinities of the taxa with their known cladistics. It is not claimed that the model reproduces the conditions of antigen evolution, but that it does indicate that such evolution, if time-dependent, must be so in a stochastic rather than a deterministic sense; and further, that having introduced chance as a factor in the evolution of biochemical characters, one has only a probability of inferring the correct phylogeny of a group from the resulting data about the similarities of contemporaneous taxa.
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James Farris
  • American Museum of Natural History
F. James Rohlf
  • State University of New York
Norman I. Platnick
  • American Museum of Natural History
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  • Florida State University