Spatial Variability of Small-leaved Linden (Tilia cordata Mill.) Leaf Blade

Abstract

The features of asymmetry and shape of small-leaved linden leaf blades (Tilia cordata Mill.) on the Kola Peninsula (Murmansk region, Kirovsk) and in the middle part of Russia (Moscow region, Orekhovo-Zuevo) were studied. The size of leaf blades in the northern population (Murmansk oblast) was significantly smaller (p <0.0001). Five linear traits had non-directional fluctuating asymmetry (FA). The method of geometric morphometrics showed a higher variability of leaf shape in the northern population compared to the southern one. Leaves differed in shape upon re-collection, and the leaf × side factor interaction showed the presence of FA in both populations (Goodall’s F criterion in the northern population was 31.7; in the southern – 92.3; p <0.0001). A high value of directional asymmetry was noted in the population on the Kola Peninsula (p <0.0001). The asymmetry of the shape did not depend on size of the leaf blades. According to linear features, plastic variability, especially in the northern population, strongly correlated with fluctuation variability (r = 0.81-0.82; p <0.05). The obtained data allows us to conclude that method of geometric morphometrics was more complex in determining the stability of development. FA was higher in the southern population, while directional asymmetry with a weak expropriation of FA was higher in the northern population. High latitude did not affect the decrease in developmental stability in terms of FA, but led to a decrease in the area of leaf blades with directional asymmetry.

Three methods testing the asymmetry of the leaf blades of the small-leaved lime

“…With a high latitudinal zonality gradient, the leaf blades differ both in size and in the dispersion of the values of the traits of the leaf blade, for example, the lengths of the veins, the distances between them. In previous works, the factors of altitudinal zonality, the nature of pollutants, the intensity of sources of technogenic pollution, and the climatic features of the collection site were considered [1][2][3]. From the obtained results, it follows that the adaptation of introduced species, such as small-leaved linden, proceeds from year to year with a high degree of morphological variability.…”

“…Previous work has shown that the population variability of the FA index was higher in the northern latitudes (Kola Peninsula) compared to central Russia. A higher fluctuating asymmetry was indicated by the method of geometric morphometry, based on a set of landmarks along the contour of the leaf blade [3]. The method of geometric morphometrics operates with high degrees of freedom, often (but not always) shows a directional asymmetry (DA) as a dominant deviation to the side, right or left.…”