Interspecific displacement mechanisms by the invasive little fire ant Wasmannia auropunctata

Abstract Competition between invasive species and native ones in the new environment was found to be significant and to affect both animal and plant species. Invasive ants are notorious for displacing local ant species through competition. Competitive displacement of native species can occur through interference and or resource competition. However, for invasive ants, little is known about the relative importance of competitive displacement. We studied competitive interactions of the little fire ant, Wasmannia auropunctata, one of the most destructive invasive ant species, with two other ant species, Monomorium subopacum and Pheidole teneriffana. We compared the species' foraging behavior and studied their aggressive interactions around food baits for the short (2 h) and long (21 days) term in the laboratory. Surprisingly we found that in short term experiments W. auropunctata had the poorest foraging abilities of the three species studied: it took the workers the longest to locate the bait and retrieve it; in addition they retrieved the lowest amount of food. When both W. auropunctata and M. subopacum were foraging the same bait, in the short term competition experiment, W. auropunctata workers did not defend the bait, and ceased foraging when encountered with competition. The long-term experiments revealed that W. auropunctata had the advantage in aggressive interactions over time; they eliminated seven of nine M. subopacum's nests while consuming some of the workers and brood. According to our laboratory studies, W. auropunctata cannot be considered an extirpator species, unless it has a substantial numerical advantage, in contrast with previous assumptions. Otherwise it may behave as an insinuator species, i.e. the workers do not initiate aggression and by staying undetected they can continue foraging adjacent to dominant species

Corrigendum: Collective search by ants in microgravity

The problem of collective search is a tradeoff between searching thoroughly and covering as much area as possible. This tradeoff depends on the density of searchers. Solutions to the problem of collective search are currently of much interest in robotics and in the study of distributed algorithms, for example to design ways that without central control robots can use local information to perform search and rescue operations. Ant colonies operate without central control. Because they can perceive only local, mostly chemical and tactile cues, they must search collectively to find resources and to monitor the colony's environment. Examining how ants in diverse environments solve the problem of collective search can elucidate how evolution has led to diverse forms of collective behavior. An experiment on the International Space Station in January 2014 examined how ants (Tetramorium caespitum) perform collective search in microgravity. In the ISS experiment, the ants explored a small arena in which a barrier was lowered to increase the area and thus lower ant density. In microgravity, relative to ground controls, ants explored the area less thoroughly and took more convoluted paths. It appears that the difficulty of holding on to the surface interfered with the ants’ ability to search collectively. Ants frequently lost contact with the surface, but showed a remarkable ability to regain contact with the surface

Spirulina (Arthrospira) industry in Inner Mongolia of China: current status and prospects

This paper outlines an investigation on current situation of Spirulina (Arthrospira) industry in Inner Mongolia, an internal region of China with temperate continental climate. More than 20 Spirulina plants have been established in Inner Mongolia since 2001, most of which are located at Wulan Town in the Ordos Plateau. By the end of 2009, the total annual production of Spirulina in the Ordos Plateau surpassed 700 t (dw), which account for ca. 80% of the total productivity of Inner Mongolia, and ca. 20% of China. Besides abundant solar radiation and enough freshwater favorable for Spirulina production, the three technical strategies contribute to the prosperity and success of Spirulina industry in the region: (1) reducing the cost or investment by overall advantages of rich local natural resources with low cost for Spirulina production, such as alkaline lakes, coal, electricity, and sandy land; (2) controlling the culture temperature and to avoid contamination by building plastic greenhouses on raceway ponds, (3) reducing investment by simplifying the construction of the ponds and the greenhouses. As the result, the growth period of Spirulina has been prolonged from about 120 to about 165 days, the cost of Spirulina has decreased by 25–30%, and the quality of products has been enhanced substantially. Inner Mongolia is expected to become the largest base for Spirulina production not only in China, but also in the world in the near future

Worldwide invasion by the little fire ant: routes of introduction and eco-evolutionary pathways

Biological invasions are generally thought to occur after human aided migration to a new range. However, human activities prior to migration may also play a role. We studied here the evolutionary genetics of introduced populations of the invasive ant Wasmannia auropunctata at a worldwide scale. Using microsatellite markers, we reconstructed the main routes of introduction of the species. We found three main routes of introduction, each of them strongly associated to human history and trading routes. We also demonstrate the overwhelming occurrence of male and female clonality in introduced populations of W. auropunctata, and suggest that this particular reproduction system is under selection in human-modified habitats. Together with previous researches focused on native populations, our results suggest that invasive clonal populations may have evolved within human modified habitats in the native range, and spread further from there. The evolutionarily most parsimonious scenario for the emergence of invasive populations of the little fire ant might thus be a two-step process. The W. auropunctata case illustrates the central role of humans in biological change, not only due to changes in migration patterns, but also in selective pressures over species

Wastewater nutrient removal in a mixed microalgae bacteria culture: effect of light and temperature on the microalgae bacteria competition

[EN] The aim of this study was to evaluate the effect of light intensity and temperature on nutrient removal and biomass productivity in a microalgae¿bacteria culture and their effects on the microalgae¿bacteria competition. Three experiments were carried out at constant temperature and various light intensities: 40, 85 and 125¿µE¿m¿2¿s¿1. Other two experiments were carried out at variable temperatures: 23¿±¿2°C and 28¿±¿2°C at light intensity of 85 and 125¿µE¿m¿2¿s¿1, respectively. The photobioreactor was fed by the effluent from an anaerobic membrane bioreactor. High nitrogen and phosphorus removal efficiencies (about 99%) were achieved under the following operating conditions: 85¿125¿µE¿m¿2¿s¿1 and 22¿±¿1°C. In the microalgae¿bacteria culture studied, increasing light intensity favoured microalgae growth and limited the nitrification process. However, a non-graduated temperature increase (up to 32°C) under the light intensities studied caused the proliferation of nitrifying bacteria and the nitrite and nitrate accumulation. Hence, light intensity and temperature are key parameters in the control of the microalgae¿bacteria competition. Biomass productivity significantly increased with light intensity, reaching 50.5¿±¿9.6, 80.3¿±¿6.5 and 94.3¿±¿7.9¿mgVSS¿L¿1¿d¿1 for a light intensity of 40, 85 and 125¿µE¿m¿2¿s¿1, respectivelyThis research work was possible because of Projects CTM2011-28595-C02-01 and CTM2011-28595-C02-02 [funded by the Spanish Ministry of Economy and Competitiveness jointly with the European Regional Development Fund and the Generalitat Valenciana GVA-ACOMP2013/203]. This research was also supported by the Spanish Ministry of Education, Culture and Sport via a pre doctoral FPU fellowship to the first author [FPU14/05082].Gonzalez-Camejo, J.; Barat, R.; Pachés Giner, MAV.; Murgui Mezquita, M.; Seco Torrecillas, A.; Ferrer, J. (2018). Wastewater nutrient removal in a mixed microalgae bacteria culture: effect of light and temperature on the microalgae bacteria competition. Environmental Technology. 39(4):503-515. https://doi.org/10.1080/09593330.2017.1305001S503515394Giménez, J. B., Robles, A., Carretero, L., Durán, F., Ruano, M. V., Gatti, M. N., … Seco, A. (2011). Experimental study of the anaerobic urban wastewater treatment in a submerged hollow-fibre membrane bioreactor at pilot scale. Bioresource Technology, 102(19), 8799-8806. doi:10.1016/j.biortech.2011.07.014Huang, Z., Ong, S. L., & Ng, H. Y. (2011). 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Behavior of mixed Chlorophyceae cultures under prolonged dark exposure. Respiration rate modeling

[EN] The behavior of three different microalgal cultures, when exposed for a long period (>48 h) to dark conditions, was studied with a methodology based on respirometry. The cultures were transferred to darkness and the oxygen evolution in the reactors was monitored after successive air injections. Several sequential oxygen uptake rates were thus calculated and a respiration constant, assuming a first order decay of a fraction of the biomass, was obtained by calibration. Initial specific oxygen uptake rates were in the range of 0.9 5.1 mg O2 g TSS−1 h−1 and dark respiration constants in the range of 0.005 0.018 h−1.This research work has been supported by the Spanish Ministry of Economy and Competitiveness (MINECO, CTM2011-28595-C02- 01/02) jointly with the European Regional Development Fund (ERDF) which are gratefully acknowledged. This research was also supported by the Spanish Ministry of Science and Innovation via a pre doctoral FPU fellowship to the first author (AP2009-4903). The authors would also like to thank the water management entities of the Generalitat Valenciana (EPSAR).Ruiz Martínez, A.; Serralta Sevilla, J.; Seco Torrecillas, A.; Ferrer, J. (2016). Behavior of mixed Chlorophyceae cultures under prolonged dark exposure. Respiration rate modeling. Ecological Engineering. 91:265-269. https://doi.org/10.1016/j.ecoleng.2016.02.025S2652699

Explaining the causes of cell death in cyanobacteria: what role for asymmetric division?

Cyanobacteria contribute a significant fraction of global primary production and are therefore of great ecological significance. An individual cyanobacteria cell has four potential fates: to divide, perhaps after a dormant period, to be eaten, to undergo viral lysis, or to undergo cell death. In some studies, cyanobacteria cell death has been classified as programmed cell death, borrowing a concept more widely known in metazoan cells, and there are various biochemical parallels to support such a categorisation. However, at the same time there is a growing awareness of asymmetric division as a fundamental process in bacterial division which can result in non-equal daughter cells with differing fitness. Thanks to recent theoretical and experimental advances it is now possible to explore cyanobacteria cell death in the light of asymmetric division and to test hypotheses on the ultimate causes of cyanobacterial cell death. Assessing the degree of protein damage within individual cells during population growth is a sensible initial research target as is the application of techniques which allow the tracking of cell lineages. The existence of asymmetric division in cyanobacteria is likely given its suggested ubiquity across the bacterial domain of life. It will be technically difficult to test the interaction of asymmetric division with environmental variability, and how that leads to individual cell death via differing susceptibilities to environmental stress. However, testing such ideas could confirm asymmetric division as the ultimate cause of cell death in cyanobacteria and thereby allow a better understanding of the patterns of cell death in natural populations