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Altitudinal gradients in a volcanic island : effect on biodiversity and species richness of the dipteran fauna

Ferreira T., Ribeiro E., Duarte-Rodrigues P. P., Boavida M.

Polish Journal of Ecology

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2012

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Vol. 60, nr 3

591-599

EN

Although research on environmental gradients is relatively common, the altitudinal gradient is one of the least explored. The discrepancies between earlier studies attributing highest diversity to lowest altitude and more recent studies where this altitudinal pattern is not maintained justify the pertinence of investigating the way diversity gradually changes with altitude. The studied altitudinal gradient is located inside the volcanic cone, on one of volcanic island Azores, and the investigated altitudes were 450, 600 and 800 meters a.s.l. Malaise traps were used to capture insects and Diptera were selected for this study. Application of the Zipt-Mandelbrot model to rank-abundance curves of Diptera sampled at three different altitudes, as well as analyses of richness, diversity and evenness, led to the conclusion that medium altitude was the stratum with the highest niche diversity, the highest specific diversity and the highest predictability. Non-metric multidimensional scaling allowed an excellent separation of the three altitudes sampled, suggesting that habitat characteristics significantly differ with altitude. The study, undertaken in a volcanic island of the Azores, Atlantic Ocean, will have heuristic interest to the scientific community in general and especially to those researchers studying environmental gradients. The results of this research will underpin further work on the insect biodiversity in the Azores Archipelago.

2

Body size distributions of eastern European Diptera

Ulrich W., Szpila K.

Polish Journal of Ecology

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2008

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Vol. 56, nr 4

557-568

EN

Weight distributions of Eastern European Diptera (estimated from 7966 species body length data compiled from Stackelberg and Nartshuk 1969, 1970) differ from respective distributions of Coleoptera and Hymenoptera. Nematoceran size distributions were predominantly right skewed while the Brachycera tended to have symmetric and left skewed distributions. Skeweness of size distributions was for Nematocera positively and for Brachycera negatively correlated with genus mean body weight. Genera of smaller mean body weight were significantly species richer than larger sized genera. Our findings are consistent with an evolutionary model that assumes body size dependent speciation and extinction rates.

3

Chaoborus flavicans in the food web - competitor or resource for fish?

Pekcan-Hekim Zeynep, Liljendahl-Nurminen Anne, Horppila Jukka

Polish Journal of Ecology

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2006

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Vol. 54, nr 4

701-707

EN

In lakes, chaoborids can be a food resource and also act as competitors for planktivorous fish. Usually their density varies reciprocally with the density of planktivorous fish, which forage on chaoborids. Results from Lake Hiidenvesi show, however, that in deep clay-turbid lakes chaoborids may be the main regulators of herbivorous zooplankton although the density of planktivorous fish is high. This is because turbidity reduces the feeding efficiency of fish while the feeding of chaoborids is not affected by the high turbidity levels.

4

Adaptations of pupae of Chironomidae (Insecta: Diptera) to oxygen-poor habitats

Marziali Laura, Lencioni Valeria, Rossaro Bruno

Polish Journal of Ecology

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2006

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Vol. 54, nr 4

687-693

EN

Morphological, behavioural and physiological adaptations of chironomids pupae to oxygen-poor habitats, such as the profundal zone of lakes, are discussed. Lentic and oxyregulator species possess developed respiratory organs (thoracic horns) and an extensive anal fringe to perform respiratory movements, whereas in rheophilic and oxy-conformer species these structures are reduced or absent. This led to the hypothesis that the number of thoracic horn branches, the number of anal macrosetae and the body size could consititute a measure of a species' oxygen requirements. These characters were analyzed in 12 species groups collected in 39 Italian lakes. Numbers were correlated to the optimum value of oxygen level, total phosphorus concentration and transparency calculated for each taxon. Taxa with plumose thoracic horns, extensive anal fringe and large body size (Chironomus) inhabited habitats poorer in oxygen than those inhabited by taxa with less extensive respiratory surface and fringe and small body size (Paratendipes, Polypedilum, Microtendipes). Stictochironomus was less tolerant than expected. Further studies are needed into the physiological adaptations of chironomid pupae.