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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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Interactions of con-generic Lecane species (Rotifera) within different macrophyte patches in a shallow lake

Kuczyńska-Kippen Natalia

Polish Journal of Ecology

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2007

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Vol. 55, nr 1

91-100

EN

The research on the distribution of species of the Lecane genus among different types of macrophytes (including rushes, nymphaeids and two zones of submerged macrophytes) in comparison with open water was carried out for three years in a shallow lake (Lake Budzyńskie, western Poland; an area - 17.4 ha, maximum depth - 2.7 m and a mean depth - 1.4 m) in order to determine the possibility of their competition and of co-existence. The distinct species of submerged macrophytes create separate vegetation beds and patches in the lake. The size of a particular macrophyte bed did not exceed the area of 5 m. Zooplankton samples were collected between 1997 and 1999 (from April to October, at about 2-week intervals) in the shallow part (approx. 1m deep) of a lake. Nymphaeids were only sampled during the 1998 and 1999. Samples were taken at each site using a plexiglass core sampler ([the empty set] 50-mm). Subsamples of a volume of about 1.5 l from the surface layer (0-1.5 m) were sampled from randomly chosen places within each macrophyte patch. Six Lecane species were analysed (Lecane bulla (Gosse), L. closterocerca (Schmarda), L. flexilis (Gosse), L. furcata (Murray), L. luna (Miiller) and L. lunaris (Ehrenberg)). L. bulla dominated at most of the examined stations each year. Detailed seasonal analysis of the abundance of particular species of the Lecane genus in most cases revealed the replacement character of their occurrence. The sudden increase in the numbers of one species caused a simultaneous decrease of another within the same macrophyte stand. A distinct replacement pattern was observed for L. bulla, which was replaced by L. closterocerca or L. luna and for another two pairs of species (L. closterocerca with L. furcata and L. flexilis with L. luna). At the same time, pairs of species such as L. closterocerca-L. lunaris (statistically positive correlation was found in the case of Chara bed - r[s] = 0.70; P = 0.007), L. flexilis-L furcata (within Typha - r[s]= 0.58; P = 0.048) and also L. luna-L. furcata (in the Myriophyllum bed - r[s]= 0.80; P = 0.001) exhibited a similar pattern of seasonal changes without, however, revealing the exchange occurrence between each other. The pattern of species replacement within a genus is an example of the competitive exclusion of closely related species. The nature of the seasonal distribution of species of the Lecane genus, replacing each other over a period of time, may be connected with the niche overlap of particular species, which results in time segregation. Exploitative competition cannot be excluded when describing such behaviour.