Monomorphic ants undergo within-colony morphological changes along the metal-pollution gradient

• Published in: Environmental science and pollution research international 2015-04, Vol.22 (8), p.6126-6134
• Main Authors: Grześ, Irena M, Okrutniak, Mateusz, Woch, Marcin W
• Format: Article
• Language: English
• Subjects: Animal behavior; Animals; Ants; Ants - anatomy & histology; Ants - drug effects; Aquatic Pollution; Atmospheric Protection/Air Quality Control/Air Pollution; Body size; Body Size - drug effects; Cadmium; Catalysis; Coefficient of variation; Colonies; Digital; Earth and Environmental Science; Ecotoxicology; energy; Energy limitation; Environment; Environmental Chemistry; Environmental Health; Environmental Pollution - adverse effects; Flowers & plants; Formicidae; Geographical distribution; head; Head - anatomy & histology; Invertebrates; Kurtosis; Lasius niger; Metals; Metals, Heavy - toxicity; Mining; Morphology; Poland; Pollution; Pollution abatement; Pollution levels; Polymorphism; Regression Analysis; Research Article; Size distribution; Skewness; Toxicity; Waste Water Technology; Water Management; Water Pollution Control; Workers (insect caste); Zinc; Zinc - analysis
• ISSN: 0944-1344; 1614-7499
• DOI: 10.1007/s11356-014-3808-5

In ants, intra and inter-colony variation in body size can be considerable, even in monomorphic species. It has been previously shown that size-related parameters can be environmentally sensitive. The shape of the body size distribution curve is, however, rarely investigated. In this study, we measured head widthes of the black garden ant Lasius niger workers using digital methods. The ants were sampled from 51 colonies originating from 19 sites located along a metal pollution gradient, established in a former mining area in Poland. Total zinc concentrations in random samples of small invertebrates were used as a measure of site pollution levels. We found that the skewness of head size distribution grows significantly in line with the pollution level of the site, ranging from values slightly below zero (about −0.5) in the least polluted site up to a positive value (about 1.5) in the most polluted site. This result indicates that the frequency of small ants grows as pollution levels increase. The coefficient of variation, as well as the measures of central tendency, was not related to the pollution level. Four hypotheses explaining the obtained results are proposed. The bias towards the higher frequency of small workers may result from energy limitation and/or metal toxicity, but may also have an adaptive function.