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Community Ecology
Authors: J. H. Fischer, C. F. McCauley, D. P. Armstrong, I. Debski, and H. U. Wittmer

Abstract

Seabirds are considered ecosystem engineers, because they facilitate ecosystem functioning (e.g., nutrient cycling), crucial for other marine and terrestrial species, including reptiles. However, studies of seabird-reptile interactions are limited. Here, we assessed the influence of the ‘Critically Endangered’ Whenua Hou Diving Petrel (Pelecanoides whenuahouensis) on the occurrence of two threatened skinks, Stewart Island green skink (Oligosoma aff. chloronoton) and southern grass skink (O. aff. polychroma). We surveyed skinks for 26 consecutive days at 51 sites with and 48 sites without Diving Petrel burrows in the dunes on Codfish Island (Whenua Hou), New Zealand. We used occupancy modelling to assess the influence of burrows on the occurrence of skinks, while accounting for other factors affecting occupancy (Ψ) and detection probabilities (p). Diving Petrel burrows had a contrasting effect on the occurrence of skinks. On average, Ψ̂ of Stewart Island green skinks was 114% higher at sites with burrows compared to sites without, while Ψ̂ of southern grass skinks was only 2% higher. Occurrence of both skinks was negatively influenced by the presence of the other skink species. On average p̂ were low: 0.013 and 0.038 for Stewart Island green and southern grass skinks, respectively. Stewart Island green skinks appear attracted to burrows, which might facilitate thermoregulation (i.e., shelter from temperature extremes). The larger Stewart Island green skinks may subsequently exclude the smaller southern grass skinks at burrows, causing the contrasting relationships. We suggest that these interspecific interactions should be considered when implementing conservation management, e.g., through the order of species reintroductions.

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The effects of two light intensities on the concentration of several flavonoids were investigated in the cotyledons of common buckwheat seedlings. The study was performed on four days old seedlings of cvs. Hruszowska, Panda, Kora and Red Corolla. One group of seedlings was grown under exposure to 180 ± 20 μmol · m−2 · s−1 photosynthetically active radiation, whereas the other group was exposed to 360 ± 20 μmol · m−2 · s−1. The experiment lasted 5 days. The results revealed that light intensity induces changes in the levels of flavonols and flavones. Increased light intensity contributed to a decrease in the concentrations of all flavone C-glucosides: orientin (luteolin-8-C-glucoside) and iso-orientin (luteolin-6-C-glucoside), and apigenin: vitexin (apigenin-8-C-glucoside) and iso-vitexin (apigenin-6-C-glucoside). Simultaneously, a substantial increase in the content of flavonols, i.e. quercetin O-glycosides, was found. To the best of our knowledge, this is the first evidence to demonstrate the contrary responses of plant flavonols and flavones to light intensity. The content of anthocyanin also increased under exposure to higher light intensity. Our results indicate that quercetin O-glycosides can play a similar role to anthocyanins in the cotyledons of common buckwheat seedlings. Results of correlation analysis indicate that the increase in flavonol and anthocyanin concentrations in response to higher light intensity is maintained through reduced accumulation of flavones and proanthocyanidins.

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