摘要:

Small mammal communities were studied in six habitats in the north Italian plain. Nine species were trapped: pygmy shrew,Sorex minutus;common shrew,Sorex araneus;lesser white toothed shrew,Crocidura suaveolens;white toothed shrew,Crocidura leucodon;harvest mouse,Micromys minutus;wood mouse,Apodemus sylraticus;bank vole,Clethrionomys glareolus;Savi pine vole,Microtus savii;water vole,Arvicola terrestris.Community diversity and species richness appeared to be related to the structural complexity of the habitat; the species composition, however differed from that usually recorded in communities in northern and central Europe. Yellow‐necked mouse,Apodemus flavicolliswas not trapped, thus confirming the absence, or scarcity, of this woodland species in the north Italian plain: common vole.Microtus arvalisand field vole,Microtus agrestis,although widely distributed and abundant in northern and central Europe were not trapped. Shrews and rodents were found to be spatially segregated. Syntopic species were clustered in eurytopic, woodland and stetopihygrophilous species; each of these groups showed a well‐defined habitat preference.

ISSN:0373-4137    

DOI:10.1080/11250009209386702

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

The organization of two birds communities (passeriformes and piriformes) has been studied at two sites in northwestern Italy in order to identify better those factors that, at different ecological levels, may afford interspecific coexistence. Apart from minor differences between the two communities mostly due to the different vegetation structure and composition of the two study areas, it has been shown that the ecological organization of these bird communities depends on common niche and habitat factors. The former mainly work to discriminate, especially in the autumn and winter, several groups of species which are both ecological and systematic assemblages, whereas the latter, independently of the above‐mentioned groups of species, further increase segregation according to habitat gradients. With regard to niche, foraging seems to discriminate groups better than do singing and resting activities.

ISSN:0373-4137    

DOI:10.1080/11250009209386703

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

Seasonal changes of the two dominant Zooplankton species in Lake Trasimeno,Bosmina longirostrisandDaphnia galeata,was studied to evaluate factors regulating plankton production and the trophic state of the lake. Weekly samples were taken from January to December 1989. Parameters of population structure (total density, and densities of eggs, juveniles, and adults) and changes in body size were studied in relation to some environmental factors. Multiple regression models were used to analyze density and body size variations to evaluate the effects of temperature and food on growth of the two populations. The statistical models showed a significant influence of temperature and food on the seasonal patterns of density and body size of both species. In comparison with previous years, in 1989 a sharp decrease in the average body size ofD. Galeatawas observed; this was determined primarily by the scarcity of food, rather than by predation. On the other hand,B. longirostrisincreased in size, being favoured by its feeding flexibility and by the composition of phytoplankton, which was made up mainly of small‐sized algae;Bosminathus became numerically dominant overDaphnia.

ISSN:0373-4137    

DOI:10.1080/11250009209386704

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

Given the widespread evidence of magnetic orientation in talitrids from Atlantic and Equatorial populations, it seemed interesting to test this ability in Mediterranean ones. This paper reports the results of orientation tests on wild caught and laboratory‐born individuals from five Italian Tyrrhenian and Adriatic populations ofTalitrus saltator(Montagu, 1808) and an Adriatic one ofTalorchestia deshayesei(Audouin, 1826). Tests were carried out in absence of visual cues with the natural magnetic field or with an artificially rotated one, and with the sun reference experimentally in conflict with the magnetic one (by block‐shifting the animals or rotating the magnetic field). On the whole, the tests failed to show magnetic orientation ability, except a weak non‐visual orientation tendency in laboratory‐born individuals of two Tyrrhenian populations. When the magnetic reference and the solar one were in conflict, the latter prevailed both for laboratory‐born and wild caught individuals. A tentative phylogenetic interpretation of the magnetic orientation in talitrids is given.

ISSN:0373-4137    

DOI:10.1080/11250009209386705

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

Larvae ofEuscorpius carpathicussettled on conspecific adults can distinguish between males and females on a chemical basis, with females being preferred to males. The preference for different females depends on their reproductive phase, with mothers being the most preferred.E. carpathicusfemales offer a better chance of survival against dehydration when mothers than before parturition, and in both cases a better one than males. This proves that the water passage is an effective specialized mechanism which appears periodically and contributes (to what extent is not known) to improving larval survival, especially in dry periods and/or environments.

ISSN:0373-4137    

DOI:10.1080/11250009209386706

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

The author discusses the significance of the ≪species problem≫ in the context of evolutionary biology and of systematics. He concludes that, contrary to current tendencies, a strongly nominalistic concept of the ≪species≫ is the only tenable one, that species cannot be conceived as individuals and that the species concept is irrelevant for evolutionary biology. Moreover a careful analysis of the species concept falsifies some of the basic tenets of Hennigian and of transformed cladism.

ISSN:0373-4137    

DOI:10.1080/11250009209386707

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

An electrophoretic study using polyacrylamide gradient gels and isoelectric focusing has confirmed that the ctenostome bryozoanAlcyonidium mytiliDalyell, 1847, to date considered a valid species, in fact comprises a number of cryptic species, of which three are present on the French, Danish, and Swedish coasts.

ISSN:0373-4137    

DOI:10.1080/11250009209386708

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

The sediments from 16 localities (8 from the Island of Elba, 3 from the Island of Giglio, and 5 from the Island of Capraia) yielded several hundreds of specimens, all identified. They belong to 28 species in 13 genera in 5 families. Of the three island, Elba, with 25 species, proved to be the richest, followed by Capraia, with 18 species, and finally by Giglio with only 8 species.Diplodasys meloriae, Tetranchyroderma quadritentaculatum,andT. sanctaecaterinaeare new to science.Tetranchyroderma cirrophorais new for the Italian fauna.

ISSN:0373-4137    

DOI:10.1080/11250009209386709

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

Twenty‐three species of chetonotid gastrotrichs are reported from three islands of the Tuscan Archipelago (Tyrrhenian Sea, Italy). The island of Elba is the largest in the archipelago and has the most sand beaches. It possesses the greatest diversity of gastrotrich fauna, with 17 known species. The island of Capraia ranks second with 12 species, and the island of Giglio is third with 8 species.Chaetonotus napoleonicusfrom the island of Elba andChaetonotus aegilonensistogether withHalichaetonotus marivagus,both from the island of Capraia, are described as new species. A clarification of the diagnostic characters ofC. atrox, C. disparandC. neptuniis given.Xenotrichula carolinensisis synonymized withX. intermedia.

ISSN:0373-4137    

DOI:10.1080/11250009209386710

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

The speciesChaetonotus lacunosusMock, 1979 is redescribed and refigured from specimens collected in littoral and shallow sublit‐toral sediments along the entire Italian coastline of the Mediterranean Sea and its adjacent waters. Six species new to science are described and figured:Chaetonotus apechochaetus, C. apolemmus, C. siciliensis, Halichaetonotus etrolomus, H. margaretae,andH. thalassopais.The proper nomenclature forHalichaetonotus decipiens(Remane, 1929) is noted, and a new combination is given:Musellifer delamarei(Renaud‐Mornant, 1968) n. comb.

ISSN:0373-4137    

DOI:10.1080/11250009209386711

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor