摘要:

Sexual dimorphism in size and plumage was investigated in the lek‐breeding Jackson's widowbirdEuplectes jacksoni.Size dimorphism was evident from the sexual difference in tarsus length, reflecting skeletal body size. The long tail and the wide collar of breeding plumaged males were obvious secondary sex traits, but the wing was also longer than in subadults and might likewise be sexually selected (i.e. not merely a byproduct of body size). Possibly, the increased wingspan functions to save energy during the jump display. To reveal intrasexual selection, courtholders were compared with floaters (nuptial males captured off the leks), and were found to be larger in body size, wing length, collar and tail. The roles of inter‐and intrasexual selection are discussed with reference to previously demonstrated female choice, and new results indicating competition for access to leks: quick reoccupation of deserted display courts, frequent observations of intruders and a finding that central males were more aggressive than peripherals. Observations imply that the collar is an agonistic signal that is neutral with respect to female choice. Possible contributions of natural selection to the sexual dimorphism are also conside

ISSN:0024-4066    

DOI:10.1111/j.1095-8312.1993.tb00681.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

The disjunct geographic distribution of plethodontid salamanders of the genusDesmognathusprovides excellent opportunities to test whether populations diverge in mate recognition systems so as to result in sexual incompatibility. Previous work has shown that sexual incompatibility may exist both among conspecific populations and between different species in this genus. Populations of the Santeetlah dusky salamander,Desmognathus santeetlah, are found at higher elevations in three mountain ranges in the southern Appalachian Mountains of eastern North America, where they are sympatric with congeneric species of similar body size. We report that statistically significant levels of sexual incompatibility exist among populations ofD. santeetlahcollected from across the species' range. Contrary to popular belief, but in accord with a growing body of empirical literature, aspects of mate recognition systems can diverge among conspecific populations of salamanders, resulting in incidental sexual incompatibility.

ISSN:0024-4066    

DOI:10.1111/j.1095-8312.1993.tb00682.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

We evaluate the arguments and evidence for a terrestrial vs an aquatic origin for the Insecta. The evidence falls into three categories: (1) evidence that does not support one view more than the other; (2) speculative evidence, which should carry little weight; and (3) evidence that does support one view more than the other. Category 1 includes evidence from locomotory and osmoregulatory systems; plausible functions have been proposed for ‘protowings’ in both aquatic and terrestrial environments, while locomotory and osmoregulatory mechanisms of insects shed little light on their origins. Fossils, phylogenetic speculation, gill structure and life histories fall into category 2, in which, although speculative, the evidence favours a terrestrial origin. The earliest fossil hexapods were apparently terrestrial and unequivocally aquatic hexapods do not appear until 60–70 million years later, while sister‐group relationships point to a terrestrial life style from at least the Hexapoda‐Myriapoda stem group. The great variation in gill structure, even within orders, suggests convergence, and the more or less completely aquatic life histories are better interpreted as steps towards independence from land, rather than signs of an aquatic origin. Category 3 includes evidence from the tracheal system. In order to have evolved in water, a tracheal system must have first invaginated, then connected with the body wall for gas exchange with the water, and thirdly connected with the internal organs. It is difficult to envisage functions for the first two stages; on the other hand, the system could have readily evolved on land by invagination of respiratory surfaces, and then have been modified to effect gas exchange in water

ISSN:0024-4066    

DOI:10.1111/j.1095-8312.1993.tb00683.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

The growing interest in using phylogenies to test evolutionary hypotheses has focused attention on the need for robust estimates of phylogenetic history. Whether specific branching structures are correct summaries of evolutionary history can be estimated only through the examination of congruence of many sets of characters. After consideration of practical and philosophical aspects of congruence, I conclude that taxonomic congruence (analysis of congruence of topologies produced from independent datasets) is preferable to character congruence (analysis of congruence between individual characters) for estimating accuracy of phylogenetic hypotheses. Existing methods for examining taxonomic congruence are discussed and the combinable components approach, when preceded by application of rigorous statistical manipulations (e.g. jackknifing or bootstrapping), found most appropriate. Implementation of the method of combinable components is described, and is demonstrated using published data forMenidiaandRana.The robust branching structure resulting from this analysis (a phylogenetic framework) contains those nodes (phylogenetic hypotheses) that are strongly supported by at least one dataset and are consistent with all others. This approach is the most appropriate/conservative for testing hypotheses about evolutionary history.

ISSN:0024-4066    

DOI:10.1111/j.1095-8312.1993.tb00684.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

Geographic variation in both the colour and pattern of carotenoid plumage pigmentation displayed by males in two subspecies of house finches (Carpodacus mexicanus frontalisandC. m. griscom) was quantified. The extent of ventral carotenoid pigmentation (patch size) differed markedly between these two subspecies;frontalismales from the U.S. (New York, Michigan, California and Hawaii) displayed a medium patch extending from their throats to their lower bellies, whilegriscomimales sampled in Guerrero, Mexico displayed small patches restricted to their throats.Frontalismales sampled in Michigan and New York andgriscomimales were relatively bright in colouration, whilefrontalismales sampled in Hawaii were relatively drab. Populations offrontalisin California showed substantial local variation in average male colouration: in two areas only 12 km apart males were as colourful and as drab as any population sampled. In aviary experiments in which they were fed either a plain seed diet or a diet supplemented with red carotenoid pigments during moult, males from all populations converged on a similar appearance, except thatgriscomimales attained a brighter plumage thanfrontalismales when their diet was supplemented with red pigments. Regardless of diet, the difference in patch sizebetween frontalisandgriscomimales persisted after moult in captivity. The author concludes that the difference in patch size betweenfrontalisandgriscomimales reflects genetic differences between these populations, but that the differences in the mean plumage colouration of males among populations reflect differences in the access that males have to carotenoid pigments during moult.

ISSN:0024-4066    

DOI:10.1111/j.1095-8312.1993.tb00685.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

Competition theory is the focus of much debate among both neontologists and palaeontologists. This paper explores the expansion of competition theory into macroevolution, since this is the relevant context for palaeobiologists, and challenges the contention that microevolutionary processes are generally inappropriate to the interpretation of macroevolutionary pattern. We show that the term ‘interspecific competition’ is imprecise, since it conflates processes operating at various hierarchical levels, and recommend a terminological change in accordance with hierarchy theory. Finally, we reassess the role of competition and its absence in radiations. Since evolutionary novelties must be fixed at speciation, and speciation occurs in response to habitat destruction rather than the freeing of ecological space, we believe the role of competition to be minimal in both radiation and the generation of nove

ISSN:0024-4066    

DOI:10.1111/j.1095-8312.1993.tb00686.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

ISSN:0024-4066    

DOI:10.1111/j.1095-8312.1993.tb00680.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY