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A method for simple assessment of cold sensitivity in insects

100%

Nadolski J. , Bańbura J.

Polish Journal of Ecology

2010

tom Vol. 58, nr 1

187-190

A simple index of sensitivity to frost in insects for the general use in ecological studies was introduced. The index is based on a cooling experiment that leads to the estimation of the subzero temperature at which 50% of a sample of particular species life form individuals are killed within 24 hours. By analogy to toxicology, such an estimate was called LTemp[50]. We present the method using our results from a series of simple cooling experiments conducted on larval gooseberry sawflies Nematus ribesii (Scopoli) and imagine queens, workers and males of the hornet Vespa crabro L. LTemp50 indices were -7.2[degrees]C for gooseberry sawfly larvae and ranged from -5.0[degrees]C for male hornets to -9.1[degrees]C for queen hornets. These differences seem to reflect reasonably the specific thermal environment adaptations of the studied insects.

Long-term changes in the size, structure and location of whiskered tern Chlidonias hybrida (L.) nests in deteriorating environmental conditions of a North African lake

80%

Bakaria F. , Benyacoub S. , Gauthier-Clerc M. , Bańbura J.

tom Vol. 57, nr 4

749-759

Long-term changes in wetland habitats have been lately reported all over the world. Global warming and, in particular, irrigation and eutrophication of shallow lakes cause changes in vegetation, often in directions differing from the natural ecological succession. As a result, from the viewpoint of waterbirds, their nesting habitats deteriorate, which leads to changes in their breeding biology and distribution. In this paper the nesting of Whiskered Tern Chlidonias hybrida (L.) was studied in changing habitat of Lake Tonga, the El-Kala National Park, NE Algeria in 1996 and 2005.2006. Since the 1960s, there has been a clear trend of extensive development of emergent and floating-leaved vegetation, with up to 80% of the lake surface being currently covered during summer. Nesting colonies of Whiskered Terns are mostly connected with beds of the white water-lily (Nymphaea alba L.). The average distance of breeding colonies from the shore line increased from 176 m in 1966 to 786 m in 2005 and 933 m in 2006. Over the study period, average nest size got twice smaller. Nest diameter was on the average 470 mm in 1996 and 236 mm in 2005.2006. The nests also changed shape and composition. The size and shape of nests were correlated with measures of their composition. Variables characterizing size, shape and composition of nests indeed differed in response to ecological variation of habitat between and within years. Our results suggest that the main function of Whiskered Tern nests is providing a firm support for eggs, incubating adults and young nestlings, which would correspond to the nest support hypothesis of Collias and Collias (1984). Nest size was influenced by ecological conditions in two ways: directly, by changing the availability of construction materials, and indirectly, by changing the distribution of colonies and, thus, physical conditions for nests. We also suggest that some components of the changes in nest size, shape and composition may be linked with the social and sexual signaling system of Whiskered Terns.