摘要:

AbstractThe relevance of the Modern Evolutionary Synthesis to the foundations of taxonomy (the construction of groups, both taxa and phyla) is reexamined. The nondimensional biological species concept, and not the multidimensional, taxonomic, species notion which is based on it, represents a culmination of an evolutionary understanding. It demonstrates how established evolutionary mechanisms acting on populations of sexually reproducing organisms provide the testable ontological basis of the species category. We question the ontology and epistemology of the phylogenetic or evolutionary species concept, and find it to be a fundamentally untenable one. We argue that at best, the phylogenetic species is a taxonomic species notion which is not a theoretical concept, and therefore should not serve as foundation for taxonomic theory in general, phylogenetics, and macroevolutionary reconstruction in particular. Although both evolutionary systematists and cladists are phylogeneticists, the reconstruction of the history of life is fundamentally different in these two approaches. We maintain that all method, including taxonomic ones, must fall out of well corroborated theory. In the case of taxonomic methodology the theoretical base must be evolutionary. The axiomatic assumptions that all phena, living and fossil, must be holophyletic taxa (species, and above), resulting from splitting events, and subsequently that evaluation of evolutionary change must be based on a taxic perspective codified by the Hennigian taxonomic species notion, are not testable premises. We discuss the relationship between some biologically, and therefore taxonomically, significant patterns in nature, and the process dependence of these patterns. Process‐free establishment of deductively tested “genealogies” is a contradiction in terms; it is impossible to “recover” phylogenetic patterns without the investment of causal and processual explanations of characters to establish well tested taxonomic properties of these (such as homologies, apomorphies, synapomorphies, or transformation series). Phylogenies of either characters or of taxa are historical‐narrative explanations (H‐N Es), based on both inductively formulated hypotheses and tested against objective, empirical evidence. We further discuss why construction of a “genealogy”, the alleged framework for “evolutionary reconstruction”, based on a taxic, cladistic outgroup comparison and aposterioriweighting of characters is circular. We define how the procedure callednull‐groupcomparison leads to the noncircular testing of the taxonomic properties of characters against which the group phylogenies must be tested. This is the only valid rooting procedure for either character or taxon evolution. While the Hennig‐principle is obviously a sound deduction from the theory of descent, cladistic reconstruction of evolutionary history itself lacks a valid methodology for testing transformation hypotheses of both characters and species. We discuss why the paleontological method is part of comparative biology with a critical time dimension ana why we believe that an “ontogenetic method” is not valid. In our view, a merger of exclusive (causal and interactive, but best described as levels of organization) and inclusive (classificatory) hierarchies has not been accomplished by a taxic scheme of evolution advocated by some. Transformational change by its very nature is not classifiable in an inclusive hierarchy, and therefore no classification can fully reflect the causal and interactive chains of events constituting phylogeny, without ignoring and contradicting large areas of corroborated evolutionary theory. Attempts to equate progressive evolutionary change with taxic schemes by Haeckelwere fundamentally flawed. His ideas found 19th century expression in a taxic perception of the evolutionary process (“phylogenesis”), a merger of typology, hierarchic and taxic notions of progress, all rooted in an ontogenetic view of phylogeny. The modern schemes of genealogical hierarchies, based on punctuation and a notion of “species” individuality, have yet to demonstrate that they hold promise beyond the Hae

ISSN:0947-5745    

DOI:10.1111/j.1439-0469.1991.tb00442.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

AbstractOn the cause of the mammalian descent of the testes (Descensus testiculorum)Two explanations have been offered for the descent of the testes in mammals, both of which are frequently cited in the literature. Mooreand co‐workers argued that the phylogenetic rise of body temperature caused the translocation of the testes. According to Portmann, the descent of the testes was due to the evolution of the scrotum as a signal. However, both the sensibility of the extra‐abdominal testes to temperature elevations and the optical effects of the scrotum can be interpreted as a consequence of testicular descent rather than as its cause.The hypothesis presented in this paper suggests a new adaptive explanation for the descent of the testes in mammals and regards its development as an example of evolutionary compromise. Obvious disadvantages such as reduced protection of the extra‐abdominal testes, “perforation” of the inguinal abdominal wall, and an increased loss of heat from the body core have to be outbalanced by a strong selective advantage. This advantage is seen in the development of a completely new, fast mode of locomotion ‐ the gallop. The strong flexions and extensions of the vertebral column during gallop should cause intense fluctuations of intra‐abdominal pressure. Fluctuations of intra‐abdominal pressure severely impede continuous flow of blood in the abdominal veins. Periodically reduced venous drainage resulting in fluctuations of intra‐testicular pressure would impair the process of spermiohistogenesis, which is dependent on an absolutely constant pressure within the testis. Thus, it is the displacement of the pressure sensitive testes out of the abdominal cavity that allows for the evolution of a fast mode of locomotion accompanied by strong fluctuations of intraabdominal pressure.In the course of the phylogenetic translocation of the testes increasing specializations of the testicular blood vessels occur. In mammals possessing a scrotum the return flow of venous blood from the extra‐abdominal testes to the abdominal cavity is supported by utilizing the energy of the arterial pulse (‘peripheral arterial pump’).A model for the successive stages of the descent of the testes is illustrated in Figures 7–10. The morphological changes related to the phylogenetic descent of the testes, such as the specialization of the testicular blood vessels, the forming of a cremasteric sack in the inguinal region, and the differentiation of the inguinal or perineal integument into a scrotum can all be interpreted as serving one purpose: they aid in maintaining a constant intra‐testicular pressure in spite of increasing fluctuations of intra‐abdominal pressure and venous blood flow during the evolution of the gallop.Although the blood vessels of the spermatic chord basically serve the same functions, they show markedly different specializations in Marsupials and Eutherians. This indicates that the descent of the testes has occurred independently, at least, in these two groups.The explanation put forward here postulates a causal relationship between the mode of locomotion and the position of the testes. Mammals possessing testes wnich reside permanently within the abdominal cavity (‘Testiconda’) cannot gallop, whereas mammals with the ability to gallop must have (periodical or permanent) extr

ISSN:0947-5745    

DOI:10.1111/j.1439-0469.1991.tb00443.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

AbstractEleven isozyme systems were investigated in wild boar (Sus scrofa ferusL.) by means of horizontal starch gel‐electrophoresis using liver and kidney extracts. Samples of 103 specimen that originated from three adjunct localities from Rhineland‐Palatinate (Fed. Rep. Germany) were analysed. AAT, ACO, GDH, GPDH, LDH, ME, MPI, MR, PGDH, and PGI were invariant. Genetic polymorphism is described for PGM. The genetic polymorphism atPgm2is explained by a biallelic model. Observed genotypic structure did not differ significantly from Hardy‐Wein‐berg‐proportions at this gene locus. The degree of heterozygosity is 58,3 % and Wright's Fixation Index F =–0.166 atPgm2.The allelic structure at this gene locus differed to a great extent from that found in domestic swine, i. e. in domestic swine the faster migratingPgm2allozyme was only found in relative low frequencies compared to wild boar. The genetic polymorphisms were moderate in the wild boar population compared to electrophoretic data of other ani

ISSN:0947-5745    

DOI:10.1111/j.1439-0469.1991.tb00444.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

AbstractPresented is the karyotype ofSorex araneusfrom 4 trapping sites in southwestern Germany. From this species nearly 20 chromosomal races have so far been described. In the study area autosomal numbers of 2na= 22–24 were recorded. The characteristical metacentricsjl,hi, gm, krand the acrocentricsn, o, p, qwere identified by G‐banding. The elementkrshows Robertsonian polymorphism. The metacentrics only allow a classification of the studied populations as chromosomal race “Vaud” from Switzerland. The postglacial recolonization and the possible presence of other chromosomal races in the central and northern parts of Germany are briefly discussed.Different selection pressures act on metacentrics and acrocentrics in central populations of a chromosomal race in contrast to those living in contact zones of different chromosomal races. It is suggested that the smaller autosomal arms are subject to weaker selection pressure to be fixed as metac

ISSN:0947-5745    

DOI:10.1111/j.1439-0469.1991.tb00445.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

ISSN:0947-5745    

DOI:10.1111/j.1439-0469.1991.tb00446.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY