摘要:

The problems associated with the identification of lepidopterous fossils (Insecta) are discussed. The origins and evolution of scales in the Amphiesmenoptera (Lepidoptera + Trichoptera) is considered. An illustrated review of the 19 Mesozoic insects described as lepidopterous is given and their identity discussed. Ample evidence of diversity of Lepidoptera in the Cretaceous, evidence (two specimens) of their presence in the Jurassic and some evidence of their presence in the Triassic is given.

ISSN:0024-4066    

DOI:10.1111/j.1095-8312.1986.tb01756.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY

摘要:

The relationship between sexual size dimorphism, body‐weight and different reproductive traits (e.g. clutch size, egg weight and incubation period) in relation to mating system and forms of parental care was studied in waders. Two hypotheses were examined. (1) Sexual size dimorphism is correlated with the intensity of sexual selection. (2) The degree of sexual size dimorphism is the result of an interrelationship between the reproductive strategy of the female and her body size. In the polygynous species the male was significantly larger than the female. This is consistent with the sexual selection hypothesis. However, among waders, a positive correlation exists between egg weight, clutch mass and body‐weight. Selection for small eggs or a short incubation period may therefore have an influence on female body‐weight. If the lack of paternal care reduces the female's possibility for producing large eggs or incubating a large clutch mass, we would expect a selection pressure for small female size among polygynous species. Thus, large sexual size dimorphism among polygynous waders may be a result of selection for small female size to lack of paternal care, or selection for large male size due to intramale competition or a female preference for large‐sized males. In multiple‐clutch species (viz. species in which the female regularly lays more than one clutch during the season) egg weight was low both for a given female and male body‐weight. The low egg weight of multiple‐clutch species is assumed to be a result of the constraints placed on the female from producing several clutches during a single br

ISSN:0024-4066    

DOI:10.1111/j.1095-8312.1986.tb01757.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY

摘要:

Males of the coenagrionid damselfliesArgia moesta, A. sedula and hchnura ramburiiuse similar penis morphology to remove and/or reposition sperm of previous males from the storage organs of females prior to inseminating them. Although the species vary in the degree to which sperm is removed from or packed into the spermatheca, in all three species, sperm is removed from the bursa copulatrix. Since sperm in the bursa probably has priority in fertilizing eggs in at least the first oviposition after mating, sperm precedence can be estimated as the percentage of sperm (by volume) in the bursa belonging to the last male to mate. Estimated sperm precedence for these species is approximately 71% for Argia sedula, 82% forI. ramburiiand 93% forA. moesta.These results, combined with similar ones for other damselflies clearly indicate that the ability to displace sperm may be widespread among temperate‐zone Zygoptera. Species with each of the four major variations in damselfly penis structure have now been shown to displace sperm using this morphology. The systematic distribution of these major variants suggests several origins of sperm displacement ability within the Zygoptera. Whether or not all damselflies are capable of sperm displacement depends on both the presence of micro‐structures used in sperm removal or repositioning and on the presence of sperm of previous males in mating females. It is possible, therefore, to predict that sperm displacement occurs in a damselfly if (1) females mate more than once, (2) mating females store sperm in organs accessible to penis morphology, (3) the distal segment of the male penis has structures similar to those known to be involved in sperm removal or repositioning, and (4) oviposition occurs in tandem or with the male non‐contact guarding his

ISSN:0024-4066    

DOI:10.1111/j.1095-8312.1986.tb01758.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY

摘要:

Among the breeding birds of an English oakwood studied over a period of 27 years, five species averaged more than 10 pairs. Two of these populations, the robin and especially the wren, crashed after the extreme winter 1962–1963, whereas the populations of three other (group II) species did not crash. In stepwise multiple regressions between per‐capita growth rate,r, and four winter temperatures, population size and year, population size was selected in all species. Winter temperatures were selected only in robin and wren. The residual variation of r which remained after the selected variables were used in a multiple regression equation was randomly distributed around zero in the three group II species. In the robin and wren, however, the residual values for the years following the cold winter were significantly higher compared to those in the years before it. This suggests that something changed either in the environment or in the birds. Robin residuals after the cold winter returned towards zero, whereas wren residuals remained at the new high level. I argue that these results can best be explained through assuming that catastrophic winter mortality was non‐random and could have caused micro‐evolutionary changes in life‐histo

ISSN:0024-4066    

DOI:10.1111/j.1095-8312.1986.tb01759.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY

摘要:

The karyotype ofCepaea vindobonensis(Pfeiffer) (2n= 50) is defined and compared with those ofC. sylvatica(Draparnaud),C. nemoralis(L.) andC. hortensis(Müller).Cepaea vindobonesisshares its chromosome number withC. sylvatica.The genusCepaeathus consists of two pairs of species, one with 2n= 50 the other with 2n= 44. The karyotype ofC. vindobonensisis distinct from that ofC. sylvaticaas it lacks any discontinuity in its range of chromosome length and has all three of its longest chromosome pairs nearly identical. The two 2n= 50 species both have an unusual meiotic bivalent showing a ‘satellite‐type’ structure. It is apparent that the 2n= 50 species are more closely related to each other than to the 2n= 44 species. No precise definition of the evolutionary history can be given but a working hypothesis is sug

ISSN:0024-4066    

DOI:10.1111/j.1095-8312.1986.tb01760.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY

摘要:

Biologists have conclusively failed to arrive at a generally acceptable definition of sexual reproduction. Because of this, several reproductive processes are seen as sexual by some authors but as asexual by others. Included among these are automictic methods of reproduction. Automixis describes several reproductive processes whereby a new individual derives from a product or products of a single meiotically dividing cell. Several forms involve an episode of nuclear fusion and it is argued that, because of this, they should be seen as sexual processes irrespective of whether the fusing bodies are differentiated as gametes or are simply meiotic tetrad nuclei. Other forms involve no episode of nuclear fusion and it is argued that, because of this, they should be seen as asexual processes. These latter forms involve the generation of diploid eggs either by restitutional meioses, or by an endomitotic event preceding or following a reductional meiosis, or involve the generation of a diploid embryo by the fusion of cleavage division nuclei in a haploid embryo; in each case the egg develops parthenogenetically.In addition to the disagreement that exists over the reproductive status of automixis, considerable confusion exists over its taxonomic distribution. It is often described as being restricted to a few species of insects, where it is parthenogenetic, but in factde range of taxa, including both isogamous and anisogamous plants and fungi, where it may be either parthenogenetic or non‐parthenogenetic. This confusion results both from a failure of many biologists writing on this subject to adequately consider the variation in life‐cycles existing between major taxa and from a general failure by botanists and mycologists to distinguish between automixis and autogamous forms of self‐fertilization (in which the fusing nuclei derive from different meioses). It is further compounded by a proliferation of synonyms for automictic processes. Thus in a number of publications automictic processes are variously described as being matromorphic, thelytokous, parthenogamic, autogamic or apomictic rather than as being autom

ISSN:0024-4066    

DOI:10.1111/j.1095-8312.1986.tb01761.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY