ISSN:0024-4066    

DOI:10.1111/j.1095-8312.1990.tb00529.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

Littorina saxatilisOlivi (1792), the rough winkle, is highly polymorphic in shell colour. Shell colour frequencies were studied at six locations in south‐western Wales, U.K., each at a geological contact between red sandstone and grey limestone or volcanic rock. At each site shell colour frequencies were determined in samples from the contact zone and on red or grey rock on either side. Highly significant associations were found between shell colour frequencies and substrate colour. Grey shells were always more common on grey rock than on red rock, and brown shells were usually more common on red than on grey rock, suggesting selection for cryptic colouration. Shell colour frequency differences were also found between replicate samples taken only 5 m apart from the same kind of rock, and between samples from the same kind of rock at the six study sites. These latter differences suggest that selection for camouflage is not the only factor involved in maintaining shell colour polymorphism in this specie

ISSN:0024-4066    

DOI:10.1111/j.1095-8312.1990.tb00530.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

Relative to body size, the frill of the Australian agamid lizardChlamydosaurus kingiiis one of the largest and most spectacular display structures seen in any animal species. More than 300 hours observation of free‐ranging lizards, combined with data on museum specimens, revealed that the frill is used primarily for intraspecific communication and predator deterrence. Earlier hypotheses on alternative uses for the frill (gliding, food storage, thermoregulation or auditory enhancement) are not supported. The folded frill may also enhance camouflage, but this is probably a fortuitous effect rather than an adaptation.Male frillnecks frequently display and fight during the mating season. Male displays are highly stereotyped, and involve repeated partial erection of the frill, head‐bobbing, tail‐lashing, and waving of forelimbs. Both males and females erect the frill during social encounters, and in response to potential predators. Males grow larger than females and have larger heads than do females at the same body size, but no dimorphism is apparent in the relative size of the frill. The extreme development of the display structure in this species may be due to general allometric relationships, as well as to ecological features that have intensified the action of sexual selection inChlamydos

ISSN:0024-4066    

DOI:10.1111/j.1095-8312.1990.tb00531.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

Fluctuating asymmetry, or random deviations from bilateral symmetry, has been widely used as a measure of developmental stability. The relationship between fluctuating asymmetry (FA) and allozymic heterozygosity was evaluated using 18 natural populations of pocket gophers (Thomomys bottae). Heterozygosity in local populations of pocket gophers ranges over more than an order of magnitude (1.5—18.4%), making this burrowing rodent particularly apt for such studies. Two measures of FA in mensural skull characters were examined: absolute deviations between left and right sides and the variance of signed differences. After log transformations, levels of FA among individuals and populations were not related to size. Repeated‐measures analyses of variance showed that FA was significant relative to measurement error, both across populations and within them. Asymmetries of different characters were uncorrelated, despite positive significant correlations among the characters themselves. FA levels varied only slightly among populations of gophers, and this variation was not significant for most characters. FA levels of populations were not correlated with allozymic heterozygosity, and analyses of variance in FA employing heterozygosity were not significant. Heterozygosity levels in these rodents appear more strongly related to aspects of population history (especially effective size and gene flow) than to developmental stability. Because so many genomic and environmental factors can affect morphological variation, caution is needed in interpreting correlations between genetic and phenetic variat

ISSN:0024-4066    

DOI:10.1111/j.1095-8312.1990.tb00532.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

Most male frogs in the genusPhysalaemusproduce a whine‐like advertisement call. MaleP. pustulosus, however, add chucks to the call. This enhances the attractiveness of the call to females, and has evolved under the influence of sexual selection despite the increased predation risk from the frog‐eating bat (Trachops cirrhosus). This complex call is unusual, if not unique, among anurans because the two call components overlap in time. Here we investigate the morphological changes responsible for the production of complex calls.ThePhysalaemus purtulosusspecies group consists of four species.Physalaemus pustulosusandP. petersiare sister species, and recently it has been shown thatP. petersiproduces chucks.Physalaemus coloradorumandP. purtulatusare sister species and neither is known to produce chucks. Two laryngeal characters vary within the species group.Physalaemus pustulosushas a large fibrous mass (FMI), whose vibration is responsible for production of the chuck. This mass is much smaller in the other three species. InP. pustulosusandP. petersithe FMI is anchored dorsally, deep within the bronchial process, the attachment is more extensive inP. pustulosus.NeitherP. pustulatus nor P. coloradorumhave such a dorsal attachment associated with their FMI. This character is responsible for allowing the FMI to vibrate independently of the vocal cords, that is, for the production of the complex call. Thus the morphological changes responsible for the evolution of this unusual behavioural innovation, the complex call, are gradual, and almost trival, in nature. This study also shows that the primitive condition of the larynx of theP. pustulosusandP. petersiancestor, was predisposed to the production of complex calls.We also document ontogenetic and sexually dimorphic patterns in larynx struct

ISSN:0024-4066    

DOI:10.1111/j.1095-8312.1990.tb00533.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

In adult endotherms—birds and mammals—mortality rates are lower in flying than non‐flying species. Rates vary with size, but allowing for this they are higher in penguins than flying birds, and in rodents than bats. These observations are most simply explained in terms of predation since flight, allowing movement in three dimensions, increases the chances of escape.There are various problems in obtaining and comparing data on rates of mortality and this partly explains a wide scattering of points. Nevertheless the main results are statistically significant, mostly at P<0.001. Amongst birds, there are several other significant differences. Mortality rates are lower at lower latitudes, and in aquatic compared to terrestrial species, with cliff‐nesters having lower rates than other aquatic birds and co‐operative breeders than other terrestrial ones. No latitudinal effect was detected in mammals. The exceptionally low rates of mortality in bats and swifts are attributed to their being particularly hard

ISSN:0024-4066    

DOI:10.1111/j.1095-8312.1990.tb00534.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

The two parts of this paper work towards the common aim of setting contexts for and documenting explanations based on historical contingencies. The first part is a review of area effects inCepaea. We discuss the original definitions and explanations, emphasizing the debate of adaptationistvsstochastic approaches, but arguing that the contrast of historical contingencyvs. selective fit to environment forms a more fruitful and fundamental context in discussing the origin of area effects. We argue that contingencies of bottlenecks and opening of formerly unsuited habitats may explain the classic area effects ofCepaeabetter than selectionist accounts originally proposed.The second part is a documentation of an area effect withinCerion columnaon the northern coast of Great Inagua, Bahamas. Historical explanations are often plagued by insufficiency of preserved information, but the Inagua example provides an unusual density of data, with several independent criteria all pointing to the same conclusion. Shells in the area effect are squat and flat‐topped in contrast with typical populations of long, thin, tapering shells living both east and west of the area effect. The flat‐topped area effect is a result of introgression with a propagule of theC. dimidiatumstock (living on nearby Cuba, and most apically flattened of allCerion). Fossils of this propagule were found fully cemented into highly indurated fossil soil crusts within the region of the current area effect. Multivariate morphometry, based on complex patterns of covariation, not just intermediacy in single characters, identifies the area effect samples as hybrids between this propagule and typicalC. columna. Genetic analysis has identified three unexpected alleles in area effect samples only, and in no other snails of any otherCeriontaxon anywhere else on Inagua. We hypothesize that the flattopped area effect did not arise as a selective response to local environments withinC. columna, but by introgression from a fortuitously introduced propagule of theC. dimidiaiumcomplex. The unexpected alleles therefore represent genetic phantoms ofC. dimidiatum'sformer presence or are hybrizymes—novel alleles produced by interspecific hybridi

ISSN:0024-4066    

DOI:10.1111/j.1095-8312.1990.tb00535.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

ISSN:0024-4066    

DOI:10.1111/j.1095-8312.1990.tb00529a.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY