摘要:

Factors affecting the distribution and numbers of the neotropical mud‐waspsZeta abdominale(Drury) in Jamaica andZ. canaliculatum(Oliv.) in Trinidad are discussed. Rainfall was a limiting factor in both aspects of the ecology of the two species. In Jamaica,Z. abdominalewas virtually absent from rainfall zones>2540 mm m.a.p. (mean annual precipitation), whereas in Trinidad,Z. canaliculatumhardly inhabited those localities of>2250 mm m.a.p. Furthermore, the local populations were progressively smaller and more scattered in wetter areas, because consistent rainfall and overcast conditions may result in reduced nesting activity. However, in a favourable locality, numbers may be temporarily increased after rainfall which boosts food supply (caterpillars).Developmental mortality, at 57.68% and 57.2896 respectively was remarkably similar inZ. abdominaleandZ. canaliculatum. The important predators within the cells wereMelittobiasp. (hawaiiensiscomplex) (Eulophidae) andAmobia fioridensisTownsend (Miltogramminae). InZeta abdominaletotal developmental mortality was positively correlated with log,0(no. of cells) at different sites; averaging only 33.3% for small populations, but 77.4% for large ones.Regulation at low numbers (Z. abdominale) was probably achieved by harsh physical factors, causing low fecundity, but great survival in the cells and high emigration rate. WhereZ. abdominalewas numerous, the physical environment was favourable, but developmental mortality was so high, that it is necessary to postulate the immigration of many nesting female

ISSN:0024-4066    

DOI:10.1111/j.1095-8312.1979.tb00026.x

出版商:Blackwell Publishing Ltd    

年代:1979

数据来源: WILEY

摘要:

The dominant view of tetrapod otic evolution–the “standard view”–holds that the tympanum developed very early in tetrapod history and is homologous in all tetrapods and that the opercular process of the rhipidistian hyomandibula is homologous to the tympanic process of the stapes in lower tetrapods. Under that view, the labyrinthodont amphibians of the Paleozoic are usually considered ancestral to reptiles, and thus the “otic notch” of labyrinthodonts and the tympanum it presumably contained form the starting‐point for middle ear evolution in reptiles.Four problems have classically been identified with the standard view: the differing relationships of the internal mandibular branch of N. VII (chorda tympani) to the processes of the stapes in amniotes and anurans; the differing orientations of the stapes in key fossil and living groups; the location of the tympanum in early fossil reptiles; and the transferral of the tympanum, during the origin of mammals, from the stapes to the articular bone of the lower jaw. An examination of these problems and of the solutions proposed under the standard view reveals thead hoc, and therefore unsatisfactory, nature of the proposed solutions.To organize and review alternative hypotheses of otic evolution an analytical table is constructed, using three characters (tympanic process, Nerve VII, tympanum), each with two possible states. A total of eight hypotheses about middle ear evolution are possible under this system, one of which is the standard view. The seven “non‐standard” hypotheses, only five of which have been argued in the literature, are briefly examined. Six of the “non‐standard” hypotheses appear unattractive for various reasons, including reliance onad hocarguments. The seventh was first proposed by Gaupp in 1898. It is today almost universally ignored but apparently largely for historical rather than scientific reasons. This hypothesis, her called the “alternative view”, appears to rest on assumptions equally as plausible as those of the standard view. Moreover, it offers a solution of the problems associated with the standard view without, apparently, raising any similarly serious problems.This paper compares the standard and alternative views of middle ear evolution in detail. Comparison proceeds on two levels. On one level, they are compared in terms of the hypotheses of phyletic tetrapod relationships each promotes and how strongly each supports its hypothesis. Both views promote the same hypothesis of tetrapod relationships. The alternative view is the more parsimonious, but the difference is not considered sufficient to provide a choice.On another level, the two views are compared in terms of their implications for: (1) the evolution of relative and absolute auditory perceptive ability; (2) the origin of reptiles; (3) the evolution of the suspensorium and cranial kinesis; and (4) the origin and evolution of recent amphibians. The nature of the data required for a test of the implications of the two views is specified in each case. Where data are available. the alternative view is consistent and the standard view is inconsistent with these data.We conclude that the alternative view is the preferable hypothesis of middle‐ear evolution. This conclusion implies the following: the tympanic membranes and the tympanic processes of the stapes in recent mammals, reptiles + birds. and frogs. are not homologous; the evolution of “special periotic systems” in the ancestors of amphibians and amniotes were independent events and preceded the evolution of tympanic membranes; the amphibian tympanic membrane. probably including that of labyrinthodonts. is not ancestral to that of amniotes. and that labyiinthodonts with an otic notch are not suitable as amniote ancestors; the stapes of early reptiles functioned primarily as part of the jaw suspension rather than in hearing; the mechanisms and abilities of sound perception in recent tetrapods are likely to be diverse rather than forming parts of a cline; and the lack of a tympanum in Gymnophiona and Caudata may be a

ISSN:0024-4066    

DOI:10.1111/j.1095-8312.1979.tb00027.x

出版商:Blackwell Publishing Ltd    

年代:1979

数据来源: WILEY

摘要:

This study was undertaken to examine the present condition of the lakes and to assess the likely consequences of increased use for recreation. Some physical and chemical aspects of the lakes and their waters were measured and the macrophytes, phytoplankton and larger invertebrates were surveyed in June and July 1973. The type of recreation enjoyed at each lake was also recorded. The lakes were all oligotrophic but the three larger ones had higher levels of nitrogen and in one case, zinc in their waters; these lakes were also the most intensively used for recreation. The variations between the biota of the different lakes, as summarized by means of ordination and classification techniques, were found to be related to the sizes of the lakes and in some cases to the lake chemistry. The relationships between the groups of living organisms, and between them and their environment, were examined more closely by means of a series of regression analyses, the results of which also suggested that lake size, as well as chemistry, had an important effect on the biota. We concluded that man had affected the lake chemistry and we predicted that if recreation activity was allowed to increase the biota of the smaller lakes would be degraded by pollution and by mechanical damage to the macrophytes.

ISSN:0024-4066    

DOI:10.1111/j.1095-8312.1979.tb00028.x

出版商:Blackwell Publishing Ltd    

年代:1979

数据来源: WILEY

ISSN:0024-4066    

DOI:10.1111/j.1095-8312.1979.tb00026a.x

出版商:Blackwell Publishing Ltd    

年代:1979

数据来源: WILEY