Biotopic variability of Polyphemus pediculus (Cladocera, Onychopoda) in a local population of Lake Michigan, USA
published: May 1, 2016
ArtNo. ESP141018801004, Price: 29.00 €
A study of 48 quantitative features was conducted on 401 specimens of Polyphemus pediculus (Linnaeus, 1761) of different age and sex, present in one and the same local population in Lake Michigan (USA) at the depths of 1.2 to 23.5 meters. Experimental data were treated statistically, employing variation and multivariant analysis methods. Differences in quantitative features and the accuracy of these differences were assessed by the ratio of sizes, variation coefficients, their limit and difference values, mean level of variability, Student's test, and statistic differences in distribution of morphometric data by principal components. All types of individual and ecological variability are unstable, proceed simultaneously and continuously, but with different intensity at different population depth horizons. Biotopic variability governs the range width and the mean level of age-specific and sex-related variability. Its magnitude, age-specific and sex-related differences diminish together with the increase of crustacean habitation depth. Mature individuals are the most variable. Variability of parthenogenetic females (Cv% = 21.9–9.4) is higher than that of heterosexual individuals, especially of males (Cv% = 8.2–7.8). Vertical primary intergradation is clearly expressed in the population. The spatial structure of the population is characterized by complexity. Three morphoforms, having statistically significant differences, are present in the population. Each of the morphoforms consists of a series of discrete micropopulations, which are located at different depths, and differ with the certainty of 95%. Morphometric differences between micropopulations get stronger together with the increase of the distance between them. Micropopulations of the shallow-water and deep-water morphoforms are discrete, do not contact, and differ reliably in all studied features. Individuals of the intermediate morphoform are spread over the entire local population. Their micropopulations differ insignificantly between each other and from the shallow-water micropopulation, but they differ reliably from deep-water morphoform in all features. The studied population is polymorphic. Within the population, there occurs a development of significant morphometric differences, adaptation of individuals to various environmental conditions, and the formation of reliably different, non-contacting micropopulations.
polyphemus pediculus • certainty of differences • difference of variation coefficients • depth of habitation • sex-related • quantitative features • age-specific • biotopic variability • mean level of variability