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Diet of five trachylepis skink species (Scincidae: Mabuyinae) in Savanna Biome of Namibia

Kopij Grzegorz

Polish Journal of Ecology

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2021

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Vol. 69, nr 3-4

183--192

EN

Lizards, especially skinks (Scincidae) occurring in arid environments constitute good study objects to test niche differentiation and other related issues of interspecific competition. Diet of five Trachylepis skink (T. punctulata, T. binotata, T. capensis, T. wahlbergii, T. damarana) was studied through stomach content analysis. Skinks were collected in savanna habitats in Namibia. In all these species, active foraging strategy predominates. All skink species preyed almost exclusively on insects. Four insect taxa comprised the bulk of diet in all five species investigated: Coleoptera, Orthoptera, Isoptera, Hymenoptera (Formicidae) and larvae. Their overall contribution ranged from 72.2% to 100.0% of all prey items in the diet of particular skink species. Most prey items were below 10 mm long, some were 11-20 mm in length. Both males and females fed on the same prey groups, but there were marked differences in the proportions of these groups. In general, males preyed more on beetles and grasshoppers, while females – more on ants. All main prey groups were recorded both in dry and in wet season in all five skink species. Food niche overlap was the highest between T. damarana and T. wahlbergii (0.84), and between T. binotata and T. punctulata (0.77). No overlap in food niche was recorded between T. capensis and T. punctulata, and low overlap (0.26) between T. capensis and T. binotata.

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Space Partitioning among Two Sympatric Species, Sand Cat (Felis margarita) and Rüppell's Fox (Vulpes rueppellii), in a Desert Landscape in Central Iran

Feizabadi H. A., Naderi M., Ashrafi S., Hemami M. R.

Polish Journal of Ecology

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2018

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Vol. 66, nr 2

194--204

EN

This study evaluates and compares habitat preferences and spatial niche breadth and overlap between two sympatrically occurring species, the sand cat (Felis margarita) and Rüppell's fox (Vulpes rueppellii), in a desert landscape of central Iran. A field survey from 2014 to 2016 was conducted to collect occurrence points for the two species as well as to identify their structural characteristics of used habitats in the occurrences points. Jacobs' index as a measure of habitat preference, Shannon and Levins' indices as measures of niche breadth, MacArthur, Levins and Pianka's indices as measures of niche overlap were calculated and interpreted. The results of this study showed that the sand cats are specifically restricted to sand dune and sabulous habitat type, whereas Rüppell's foxes have wider ecological amplitude. Sand cats only prefers sand dunes while Rüppell's foxes were found to prefer foothills, badlands, and sand dunes. Rüppell's foxes therefore had a wider niche breadth compared to the sand cats. The asymmetric MacArthur and Levins indices yielded a higher value of niche overlap for the sand cats compared to Rüppell's foxes, while the symmetric Pianka's measure of niche overlap was relatively high for both species. Such habitat preference and niche segregation between the two species may be a result of their feeding habits or the physical protective structure of their habitats attributes.

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The port service ecosystem research based on the Lotka-Volterra model

Li W., Liu W., Xu X., Gao Z.

Polish Maritime Research

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2017

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S 3

86--94

EN

Under the new normal of China’s economy, the competition among the port enterprises is not only the competition of the core competence of the port, the port industry chain or the port supply chain, but also the competition of the port service ecosystem. In this paper, the concept and characteristics of the port service ecosystem is discussed, a hierarchical model of the port service ecosystem is constructed. As an extended logistic model, Lotka-Volterra model is applied to study the competitive co-evolution and mutually beneficial co-evolution of enterprises in the port service ecosystem. This paper simulates the co-evolution of enterprises in the port service ecosystem by using MATLAB programming. The simulation results show that the breadth of the niche of the enterprises is changing with the change of the competition coefficient and the coefficient of mutual benefit in the port service ecosystem. Based on that, some proposals are put forward to ensure the healthy and orderly development of the port service ecosystem.