Competitive interactions between herbivorous rotifers: importance of food concentration and initial population density

Hydrobiologia ◽  
1996 ◽  
Vol 331 (1-3) ◽  
pp. 1-7 ◽  
Author(s):  
S. S. S. Sarma ◽  
Nandini Iyer ◽  
H. J. Dumont
Keyword(s):  
Population Density ◽  
Food Concentration ◽  
Competitive Interactions ◽  
Initial Population ◽  
Initial Population Density

scholarly journals A theoretical framework for multi-species range expansion in spatially heterogeneous landscapes

2021 ◽  
Author(s):  
Lukas Eigentler ◽  
Nicola R Stanley-Wall ◽  
Fordyce A Davidson
Keyword(s):  
Population Density ◽  
Range Expansion ◽  
Theoretical Framework ◽  
Dominant Mode ◽  
Bacterial Biofilm ◽  
Time Interval ◽  
Initial Population ◽  
Initial Population Density ◽  
Competitive Outcome ◽  
The Impact

Range expansion is the spatial spread of a population into previously unoccupied regions. Understanding range expansion is important for the study and successful manipulation and management of ecosystems, with applications ranging from controlling bacterial biofilm formation in industrial and medical environments to large scale conservation programmes for species undergoing climate-change induced habitat disruption. During range expansion, species typically encounter competitors. Moreover, the environment into which expansion takes place is almost always heterogeneous when considered at the scale of the individual. Despite the ubiquitous nature of these features, the impact of competition and spatial landscape heterogeneities on range expansion remains understudied. In this paper we present a theoretical framework comprising two competing generic species undergoing range expansion and use it to investigate the impact of spatial landscape heterogeneities on range expansion with a particular focus on its effect on competition dynamics. We reveal that the area covered by range expansion during a fixed time interval is highly variable due to the fixed landscape heterogeneities. Moreover, we report significant variability in competitive outcome (relative abundance of a focal species) but determine that this is induced by low initial population densities, independent of landscape heterogeneities. We further show that both area covered by range expansion and competitive outcome can be accurately predicted by a Voronoi tessellation with respect to an appropriate metric, which only requires information on the spatial landscape and the response of each species to that landscape. Finally, we reveal that if species interact antagonistically during range expansion, the dominant mode of competition depends on the initial population density. Antagonistic actions determine competitive outcome if the initial population density is high, but competition for space is the dominant mode of competition if the initial population density is low.

scholarly journals A Population of Meloidogyne javanica in Spain Virulent to the Mi Resistance Gene in Tomato

Plant Disease ◽  
2001 ◽  
Vol 85 (3) ◽  
pp. 271-276 ◽  
Author(s):  
C. Ornat ◽  
S. Verdejo-Lucas ◽  
F. J. Sorribas
Keyword(s):  
Population Density ◽  
Negative Correlation ◽  
Meloidogyne Javanica ◽  
Initial Population ◽  
Initial Population Density ◽  
Tomato Yield ◽  
Final Population ◽  
Tomato Cultivars ◽  
Mi Gene ◽  
Susceptible Tomato

A population of Meloidogyne javanica virulent to Mi-gene in tomato was identified in Spain. It reproduced similarly on resistant and susceptible tomato cultivars in the greenhouse, microplots, and in the field. In monoxenic cultures, reproduction of the virulent M. javanica was higher than that of an avirulent population on resistant but not on susceptible tomatoes. The virulent population suppressed tomato yield of both resistant and susceptible tomatoes by 29% in microplots. Initial population density (Pi) was inversely correlated with Pf (final population density)/Pi on both resistant and susceptible tomatoes in the field. A negative correlation was found between Pi and tomato yield for the susceptible but not for the resistant cultivar.

Experiment on obtaining an algologically pure culture of Tetraselmis viridis in non-sterile conditions

2020 ◽  
pp. 94-100
Author(s):  
Svetlana Yu. Gorbunova ◽  
Rudolf P. Trenkenshu
Keyword(s):  
Population Density ◽  
Pure Culture ◽  
Sea Water ◽  
The Black Sea ◽  
Initial Population ◽  
Green Microalgae ◽  
Infected Culture ◽  
Initial Population Density ◽  
Mechanical Removal ◽  
Tetraselmis Viridis

The possibility of obtaining an algologically pure culture of Tetraselmis viridis, grown on the Black Sea water in non-sterile conditions, was shown experimentally. Our experiments showed that at low initial population density of the culture after 1–3 days, there was an infection of the culture with blue-green species of microalgae (Oscillatoria sp.). Thrice repeated mechanical removal of blue-green microalgae cells by filtering the infected culture allowed obtaining an algologically pure culture of T. viridis. Under similar conditions of T. viridis cultivation, but with the initial addition of NaCl (15 g/l) to the nutrient medium aimed at increasing salinity to the Mediterranean level, there was no contamination of the culture.

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