摘要:

The feeding‐associated morphological structures of the twoGaleichthysspecies were found to be similar in all respects. Interspecific competition for food was avoided through habitat separation. Habitat preference, as established by dietary analysis and fishing trials, was based on substratum type.Galeichthys felicepsfed over sandy and muddy substrata in marine and estuarine environments, whileG. aterfed exclusively over marine reefs. The two species have different caudal fin structures which are probably evolutionary responses to habitat‐associated behavioural requirements in the two different environments.The diets of the two species were investigated and compared using calorific values of prey items. While both species fed predominantly on benthic crustaceans, polychaetes and molluscs, little dietary overlap occurred at the species level. In the estuarine environment,G. felicepsfed mainly on the anomuransUpogebia africanaandCalianassa kraussi, crabsHymenosoma orbiculareandCleislosoma edwardsii, and several isopod species. In the marine environmentG. felicepsfed mainly on two species of crabs,Thaumastoplax spiralisandGoneplax angulata, the echiuridOchaetostoma capenseand the sedentary polychaeteSternaspsis scutata.A high incidence of teleost scales in the diet ofG. felicepsjuveniles was found to be a consequence of scavenging rather than a lepidophagous habit.Galeichthys aterfed widely on several reef‐associated crabs, isopods, polychaetes and cephal

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1990.tb03990.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

Females of the carpenter beeXylocopa (Neoxylocopa) varipunctaPatton exhibit highly active mate choice. During the spring in central Arizona, males of this species hover at shrubs and trees on or near ridgelines in late afternoons. Occasionally, females fly to and closely approach pheromone‐releasing males on their territories, but in 65 of 85 approaches the female left without copulating. Some females visited several males in a few minutes. Copulation only occurred when the female landed on a spot that the resident male rubbed with his body upon the female's arrival. Males did not attempt to disrupt courtship or copulation by other males. In 1988 one creosote bush proved especially attractive to males, as measured by the frequency with which the site was occupied simultaneously by more than one male. The majority of close approaches by females occurred in this one bush. Simultaneous occupation of hovering sites was very rare in 1989. In this year, there was a weak but significant correlation between the frequency with which different sites were visited by intruder males and by females. These results support the hypothesis that males are able to identify locations most likely to attract potential mate

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1990.tb03991.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

The gekkonid genusPhelsumais unique in possessing hypertrophied distal chondroepiphyses on the antepenultimate and penultimate phalanges of digits two to five of both manus and pes. These epiphyses have relationships with the adhesive systems of the digits which suggest that they play a role in enhancing the effectiveness of adhesion. It is suggested that the hypertrophied chondroepiphyses result from alterations in developmental timing and the suppression of the elaboration of secondary centres of ossification. They may be at least partially analogous to the intercalary elements of hylid and other frogs. The presence of hypertrophied chondroepiphyses inPhelsuma ocellatafurther strengthens the case that this species belongs to the genusPhelsumaand not to the southern African genusRhoptropus.

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1990.tb03992.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

A community of small rodents was studied in the woodland savanna of Liwonde National Park, Malawi from September 1984 to June 1985. Seven species were recorded on two 11 ha grids, using a capture‐mark‐release technique. Three species (Aelhomys chrysophilus, Acomys spinosissimusandTatera leucogasler) comprised 78% of all trapped individuals. Average population numbers fluctuated from 3 to 17 individuals/ha. The grid with the densest vegetation supported the greatest number of individuals. Highest population numbers occurred in the mid‐dry season (when the grids appeared to act as refugia) and in the early wet season (due to recruitment of young animals). Areas which had been burned during the dry season did not support as many individuals as unburnt areas. Population survival rates were low, with only about 50% of individuals surviving to the following month. The number of individuals/ha in Liwonde NP was lower than in similar habitats in other parts of eastern Africa, probably because of the shorter rainfall season and the consequent strong seasonal fluctuations in food resources, reduced opportunity for reproduction, and overall low productivity of the ecos

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1990.tb03993.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

The Neotropical cichlid fishCichlasoma citrinellumexhibits a distinct trophic polymorphism in the structure of its pharyngeal jaws. Fish have either strong, sturdy molariform pharyngeal jaws or weak papilliform jaws. Intermediate forms are rare among adults. Ontogenetically, however, all fish start as papilliform morphs. Differences in morphology and allometry between morphs in external measurements (25 measurements) and measurements of the lower pharyngeal jaws (nine measurements) were analysed using a multivariate morphometric approach. The ontogenetic growth trajectories for the pharyngeal jaws of the respective morphs start to diverge early in ontogeny and therefore seem to preclude the existence of adult intermediate morphs. The isometric growth of the tooth diameter in molariform morphs (in relation to standard length), versus its relatively retarded (negatively allometric) growth in the papilliform morph, is the main cause for the development of distinct trophic morphs in pharyngeal‐jaw morphology. At approximately 50 mm standard length, both pharyngeal morphs can be discerned clearly. In this study only larger fish of determined pharyngeal‐jaw morphology were considered (n= 30 for molariform morphs,n= 31 for papilliform morphs). External morphology differs between morphs as well, but less perceptibly. Principal‐components analyses revealed that only a few measures load highly on PC2 and therefore account for most of the differences between the two trophic morphs in the shape of the external morphology. Molariform morphs have blunter, shorter snouts, larger eyes and deeper, shorter bodies than papilliform morphs.The two external morphologies resemble other known limnetic and benthic body shapes of polymorphic species of fishes, and are believed to enhance the ecological separation of the two pharyngeal‐jaw morphs. Evolutionary implications of ontogenetic changes and adult differences in morphology and trophic polymorphism are manifold. The alternative adaptations in this polymorphic species will decrease intraspecific competition by differential niche utilization and habitat choice, thus allowing for larger population sizes. Alternative adaptations may eventually lead to genetic isolation and possibly speciation of the two trophic

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1990.tb03994.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

Parotid salivation was stimulated in anaesthetized koalas by intravenous infusion of carbamylcholine chloride to ascertain flow rates, composition and possible adaptations of salivary function to a diet of eucalypt leaves. Maximum fluid secretion rates per gram tissue (62.0 ± 4.89 μl/g gland/min) were very low but, because the gland is relatively large, maximum flow rates (1.14 ± 0.105 ml min−1) were comparable with other herbivores when scaled for animal size. Salivary concentrations of protein (1.34 ± 0.165 to 3.35 ± 0.298 g 1−1), Na (42.0 ± 4.19 to 142.9 ± 1.78 mmol 1−1), Ca (0.97 ± 0.152 to 2.21 ± 0.300 mmol 1−1), HCO3(14.3 ± 2.18 to 78.4 ± 2.48 mmol 1−1), Cl (10.6 ± 1.29 to 58.6 ± 1.16 mmol 1−1) and the osmolality (107.0 ± 7.67 to 273.9 ± 1.31 mosmol kg−1) were positively correlated with salivary flow rate. The concentrations of urea (4.22 ± 0.345 to 1.71 ± 0.386 mmol 1−1), K. (25.1 ± 3.04 to 8.92 ± 0.71 mmol 1−1), Mg (206.1 ± 42.78 to 18.3 ± 0.64 μmol 1−1), H+ (273.6±51.23 to 17.5 ± 1.16 μmol 1−1) and PO4(29.6 ± 2.78 to 4.3 ± 0.39mmol 1−1) were negatively correlated with flow rate. The functional significance of the high buffer capacity of the saliva is unclear as koalas do not foregut ferment. The saliva lacked amylase activity entirely and plasma amylase activity was very low indicating low production rates by other tissues, both of which are probable adaptations to the low starch levels of the eucalypt diet. Salivary Na/K ratios were unaltered by aldosterone infusion (3 h at 5 and 50 μg h−1) which was interpreted as an indication that the koala gland, like the macropod parotid, requires long expos

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1990.tb03995.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

Small mammals in a high‐altitude grassland area close to Mexico City were studied. Populations of 10 species were censused using live traps in 48 sample quadrats. Within each quadrat, vegetation characterization, including complete floristic listings, cover values for species and layers and values of habitat modification, were assessed. Habitats were described according to plant communities identified using ordination and classification methods. Nine different plant communities were obtained. Densities and abundance of all small mammal species were calculated for each of the habitats classified.Peromyscus alsloniwas the most abundant species in all habitats, reaching maximum densities of 55 ha−1inpine forest with dense ground and herb layer. Peromyscus melanotisalso occurred in all habitats but at lower densities (maximum 29 ha−1).Reithrodontomys megalotiswas found in all habitats except intall dense grassland.Densities for this species were generally low (1‐9 ha−1) but reached 19 ha−1inshort dense grassland.All other species were largely absent from 4–8 habitats and showed very low densities (0.75–4 ha−1). The densities of the more abundant species were largely correlated with more open habitats and higher indices of habitat modification. Lower altitude grassland habitats have a greater abundance of small mammals and a higher species richness than the medium and higher altitude, physiognomically more complex habitats. Species richness was highest intall pine‐alder forest with a species‐rich, dense herb layerand lowest inpine forest with dense ground and herb layers.Species richness was positively correlated with overall

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1990.tb03996.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1990.tb03997.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1990.tb03998.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1990.tb03999.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY