Search results for "sex ratio."
showing 4 items of 104 documents
Sexual segregation of Echinorhynchus borealis von Linstow, 1901 (Acanthocephala) in the gut of burbot (Lota lota Linnaeus)
2015
Helminths often occupy defined niches in the gut of their definitive hosts. In the dioecious acanthocephalans, adult males and females usually have similar gut distributions, but sexual site segregation has been reported in at least some species. We studied the intestinal distribution of the acanthocephalan Echinorhynchus borealis von Linstow, 1901 (syn. of E. cinctulus Porta, 1905) in its definitive host, burbot (Lota lota Linnaeus). Over 80% of female worms were found in the pyloric caeca, whereas the majority of males were in the anterior two-thirds of the intestine. This difference was relatively consistent between individual fish hosts. Worms from different parts of the gut did not dif…
Impact of plant cover on the cavity-nesting ant Temnothorax crassispinus
2017
1. Plant communities influence the availability of important resources for ants, such as nest sites and food, as well as environmental conditions. Thus, plants affect the abundance and distribution of ants. 2. In a field experiment, the influence of plant cover on the settlement of nest sites and per-capita productivity of sexual individuals by the ant Temnothorax crassispinus was analysed. In July 2014, in five areas with patches of alien balsam Impatiens parviflora, and another five of native balsam I. noli-tangere, transects composed of artificial nests were established; the nest sites were situated inside patches of balsams, and outside of them. Four hundred and forty artificial nests w…
Data from: Daphnia females adjust sex allocation in response to current sex ratio and density
2019
Cyclical parthenogenesis presents an interesting challenge for the study of sex allocation, as individuals’ allocation decisions involve both the choice between sexual and asexual reproduction, and the choice between sons and daughters. Male production is therefore expected to depend on ecological and evolutionary drivers of overall investment in sex, and those influencing male reproductive value during sexual periods. We manipulated experimental populations, and made repeated observations of natural populations over their growing season, to disentangle effects of population density and the timing of sex from effects of adult sex ratio on sex allocation in cyclically parthenogenetic Daphnia…
La ecología del mirlo Turdus merula en los naranjales: un estudio a largo plazo
2015
Se estudiaron algunos aspectos demográficos y de la biología reproductiva del mirlo común Turdus merula en una superficie de 17 ha dedicada al cultivo del naranjo en la localidad valenciana de Sagunto. Mediante la aplicación mixta de la técnica de la parcela y de la búsqueda de nidos se calculó el número de parejas nidificantes desde 1975 hasta 2015 y se obtuvo información sobre el tamaño de la puesta, el éxito reproductor y las causas del fracaso de los nidos. El programa de anillamiento llevado a cabo en cuatro sesiones anuales desde el año 2000 hasta 2009 proporcionó información sobre la filopatria natal, la proporción de sexos y la supervivencia de los adultos. La variación estacional d…