Franca Guidali

Song perception among incipient species as a mechanism for reproductive isolation.

Many functions in behavioural processes of small passerines are regulated via vocal messages. Song plays an important role in the development of reproductive barriers and thus playback experiments can often be used for investigating the potential for reproductive isolation through behavioural mechanisms. Moltoni’s warbler Sylvia (cantillans) moltonii is characterized by diagnostic vocalizations and a peculiar pattern of distribution, being parapatric and partly sympatric with the nominate Sylvia c. cantillans. With this work, we test whether these two closely related taxa react equally to their own song and to the song of the other taxon, shedding light on whether they perceive each other’s songs as coming from the same species. We carried out 184 playback experiments within the mainland range of the two forms. We judged the response of the bird on a scale of scores. Each taxon responded more strongly to playback when faced with the song of its own taxon. This held true when applied only to males or females. Additionally, birds tested for both songs showed a stronger response to the song of their own taxon. The distributional context (sympatry vs. allopatry) did not affect bird response. Results indicate that a certain degree of reproductive isolation between the two taxa (because of diverged mate recognition systems) already exists; consistently with genetic data and with the peculiar pattern of distribution; this suggests that the two taxa have reached species status.

Diet and trophic niche overlap of two ranid species in northern Italy

Abstract Diet of two syntopic populations of Rana dalmatina and R. synklepton esculenta were studied in order to collect data about competition and niche overlap in relation to habitats frequented. Field observations confirm previous ecological researches and show that the former species has a short aquatic phase during the mating period; it lives in woods after breeding relatively far from water. The edible frog, on the contrary, remains near damp areas during the whole activity period. Trophic niche breadth proved greater in R. dalmatina than in R. synklepton esculenta. Niche overlap between species was low, because of the different kind of habitats frequented, while that between sexes was low in R. dalmatina, because males and females show different activity patterns during the year. On the contrary, overlap was complete in R. synklepton esculenta. No correlation was found between the size of frogs and preys. In conclusion, frogs are opportunistic predators and our results suggest that maintaining a highly diversified habitat is useful for avoiding competition between species.

Syntopic Taxa in the Sylvia cantillans Species Complex

Abstract. Distributional relationships among closely related taxa can provide key information about the levels of their reproductive isolation or compatibility, and thus the stage of speciation process. Here, we present new information on the sites where two taxa traditionally considered as subspecies of the Subalpine Warbler Sylvia cantillans, S. c. cantillans and S. (c.) moltonii, breed sympatrically in mainland Italy. We analyse geographic distribution and behaviour as well as other characteristics shown by these warblers in the areas of contact. The distributional pattern shown by these taxa, which is partly sympatric with syntopic breeding, and the apparent lack of interbreeding, strongly suggest that they behave as different species, confirming previous findings about genetic divergence and differential song perception.

Multilevel habitat preferences of Apodemus sylvaticus and Clethrionomys glareolus in an intensively cultivated agricultural landscape

Small mammals are considered good model species for assessing the global effects of habitat loss and fragmentation in agricultural landscapes. With the aim of investigating the composition and habitat preferences of the small mammal community in an intensively cultivated area, we sampled the three main “macro-habitats” (wood patches, poplar plantations and crops) available on the western plain of the River Po (North Italy). The influence of habitat variables on each species’ occurrence was assessed at three different scales of observation: “macro-habitat”, “micro-habitat” (i.e. vegetation layers at trap sites) and the landscape level (i.e. land cover in plots of 500 m radius centred on each trap line). Overall, 3344 trap-nights yielded 169 Apodemus sylvaticus, 28 Clethrionomys glareolus and two Sorex araneus. The first species was dominant in all macro-habitats, while the other two species were trapped only in residual wood patches. The thickness of the fine litter was the main micro-habitat factor affecting the occurrence of both C. glareolus and A. sylvaticus in woods, while sites with herbaceous vegetation cover were preferred by the latter species in poplar plantations. Intraclass correlation coefficients showed that sites with thick litter or high herb cover were neither exclusive nor predominant in wood patches and poplar plantations, respectively, suggesting that the choice for micro-habitat parameters is subordinate to that of macro-habitat characteristics, mainly tree and shrub cover. At the landscape scale, no habitat variable affected the occurrence of both species. At the macro-habitat level, the strong selection for wood patches by both wood mice and bank voles and the negligible occurrence of small mammals in cultivated plots pointed out the major role for conservation played by residual semi-natural habitats in agricultural landscapes.

Differences in the dimensions of diurnal and nocturnal pellets of the barn owl, Tyto alba

Abstract Linear dimensions and weight of barn owl pellets collected at a hay‐loft and at a roost‐site were examined. Pellets ejected in the hayloft during nocturnal hunting activity were significantly smaller and lighter than those ejected at the roost‐site during resting periods in daylight hours. This observation is in agreement with the “pelote diurne et pelote nocturne” theory suggested by Guerin (1932). Linear dimensions and weight of pellets varied from one to another season. Thus, it was suggested that the feeding tactics exhibited by barn owls may affect the content and the linear dimensions and weight of pellets; moreover, it was pointed out that further studies are necessary on pellet characteristics in habitats where barn owl faces spatial and temporal variations in the availability of its most important food resources.