ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1994.tb01554.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1994.tb01555.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

Polypterid fishes ventilate their lungs by recoil aspiration. Active exhalation compresses the bony scale jacket; inhalation occurs when the scale jacket recoils to its original shape. Exhalation and loading of the integument are powered by contraction of striated muscle in the lung walls. The integument of polypterid fishes consists of interlocking rhomboid scales held together by collagen fibre strands. The scales imbricate with bevelled edges, so that when the fish is at rest, its integument is circular in cross‐section and the overlapping scale edges are parallel. During exhalation, the hemicircular shape of the ventral integument is deformed, and the scales rotate slightly. As the overlapping scale edges become non parallel, the scales act as tiny levers to stretch the collagen fibres between them. When the fish opens its glottis to inhale, the stretched collagen fibres return to their rest lengths and pull the scale jacket back into a circular shape, sucking air into the lungs. Thus, despite the deformation of the integument as a whole in compression, strain energy is stored in tensile element

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1994.tb01556.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

Antler growth and form was examined for a sample of 303 sika stags(Cervus nippon)culled over an eight‐year period from a feral population in Killarney National Park, County Kerry, Ireland. Most antler measurements taken were highly correlated with each other and growth was complete after the sixth year. Few abnormalities were recorded and the degree of asymmetry in structure was less than previously reported for other sika populations. Variability in structure decreased with age and there was no effect of year of birth or cull on antler size for either adult or yearling stags. The growth pattern was similar to that of other populations except that the proportion of ‘eight pointers’ was low. An examination of antler damage was used to estimate fighting frequency across age classes. The results are discussed in relation to the genetic history of the herd and the use of antlers as weapons for intra‐specific

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1994.tb01557.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

ParagehyraAngel is a gekkonine genus endemic to Madagascar. From 1929 until the present, the genus was represented only by the holotype of the single known species.Paragehyra petiti.The type locality ofP. petitiis in the driest part of Madagascar (south‐west) where rainless periods may exceed 11 months and the original vegetation consists of thorn scrub or dry deciduous forest. No new individuals ofP. petitiwere observed. However, a second, undescribed species of the genus was discovered in October 1990 on the opposite side of the island (south‐east) in primary‐low montane rainforest. The new form was observed at four localities at the southernmost extremity of rainforest in Madag

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1994.tb01558.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

The study of the phylogenetic relationships ofHamacanthaGray. 1867 showed it to be more closely related to mycalids than to desmacellids, on the basis of its highly cavernous choanosome with stout ascending tracts of megascleres, easily detachable ectosome with a reticulation of megasclere bundles, and presence of rosettes and of true toxa. SincePozziellaTopsent, 1896 is recognized as a good genus, close toHamacantha.the family name Hamacanthidae Gray, 1872 may be retained for this assemblage. This family is the sister‐group of the Mycalidae Lundbeck, 1905 branch, and they both have Desmacellidae Ridley&Dondy, 1886 as sister‐group. A cladogram expressing these relationships is provided and compared with previous ones in the literature. Mycalidae, Hamacanthidae, Desmacellidae, Cladorhizidae and ‘guitarrids’ form a monophyletic group by sharing two derived characters: faintly‐necked styles, and sigmancistra de

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1994.tb01559.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

The pattern of the occlusal surface of 1018 first lower premolars (P3) was studied in 527 brown hares(Lepus europaeus)collected in 1988 and 1989 at 21 localities in Austria. In total, 29 variants were described. For analysis of geographic variation in the P3‐pattern, the locality samples were grouped into five regional units with respect to spatial distances and putative barriers for gene flow. From the primarily encountered variants. 15 dicholomized characters were created and their frequencies within the five regional units were calculated. Strong right/left dependencies of character states suggested a high degree of bilateral symmetry in each character. In contrast, character varied largely independently from one another. This indicated the absence of complex types of the P3.One character showed sex‐dependence but no age dependence was found. Intraregional differences in trait frequency were found in one character. Non‐metrical morphological divergence among the five regional units was revealed by using C. A. B. Smith's ‘mean measure of divergence’ and ‘percentage dissimilarity’ as distance measurements. Six pairwise morphological distances differed significantly from zero. Phenetic affinities among the five populations showed good correspondence to the geographic distribution of the samples. However, whereas the alpine chains of mountains appeared to separate the hare populations, the River Danube did not, Generally, good concordance was found between the current pattern of phenetic differentiation and earlier results of cluster analyses using non‐metrical skull traits and allozymes of the same populations. This suggested that geographic differentiation of the P3‐traits was largely due to random historical rather than to ecogenetic causes. Nevertheless, in one population the striking discordance between the three character‐systems compared could indicate some influence of a selection pressure on

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1994.tb01560.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

Müllerian mimicry, in which there is convergence in coloration between unrelated unpalatable species, should lead to uniformity in appearance, not polymorphism, and so the occurrence in tropical Africa of unrelated species of unpalatable butterflies with corresponding polymorphic colour forms suggested a problem of special evolutionary interest. Field work in Uganda and Sierra Leone in 1964 72 demonstrated a statistical association between the occurrence and relative frequencies of polymorphic forms inDanaus chrysippus(Danainae) andAcraea encedon(Acraeinae) which was deemed as confirmation of a Müllerian relationship between them. There were, however, certain anomalies which at the time remained unresolved. Later, in 1976, it was discovered that what had been calledA. encedonis in reality two sibling species.A. encedonand a new one, named asA. encedana.The two differ in the structure of both male and female genitalia and in the coloration and the food‐plants of the larvae. The recognition of the additional species has enabled a re‐assessment of the polymorphie Müllerian association withD. chrysippus.It emerges that, although there is a close qualitative and quantitative reciprocal mimetic relationship betweenA. encedanaandD. chrysippus,the relationship betweenA. encedonandD. chrysippusis much weaker, and in places non‐exitent. The possible origin of the mimetic polymorphism is discussed in terms of hybridization of previously allopatric and monomorphic populations which have met as a consequence of recent expansions of geographical range in all three species resulting from forest clearance and the spread of savanna‐like conditions in previously fore

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1994.tb01561.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

In some animals sex is determined after conception by environmental factors (environmental sex determination. ESD). In the amphipodGammarus duebenisex is reportedly determined by photoperiod: there is a higher proportion of males in broods reared under long‐day than under short‐day photoperiods. It has been proposed that this is an adaptive response to seasonal population dynamics. A test of the hypothesis would be to demonstrate changes in the degree to which sex is determined by the environment in populations from different latitudes with different dynamics. This study reports such a test. Environmental response is significantly less strong in a southern population with a long breeding season than in a northern one in which breeding is seasonally restricted. Moreover, the threshold of the ESD cue for male or female determination is not defined when the breeding season is weakly seasonal. There is a broad correlation between latitude (and hence breeding seasonality) and the strength of ESD response across a series of population studies. Similarities between theGammarussystem of sex determination and that of the Atlantic silversideMenidia menidia,a fish with thermal ESD, are discus

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1994.tb01562.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

Radio‐tracking and mark recapture methods were used to characterize the spatial organization and temporal activity patterns of free‐ranging platypuses in southern Victoria. The study area supported an estimated 1.3‐2.1 adult or subadult animals per kilometre of stream in the three summers sampled. The individual home ranges of 15 radio‐tagged animals comprised 0.33‐2.28 km of stream; animals foraging exclusively in the stream had significantly longer ranges (mean=1.40 km) than animals which also foraged in associated pond habitats (mean=0.64km). Home ranges of grown females overlapped with those of neighbouring grown females, subadult and adult males, and juveniles (

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1994.tb01563.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY