Characteristics of the butterflies on various forms of land uses

The purpose of the research was to identify the species and quantitative contents of butterflies in a field-and-forest landscape. It was investigated whether the form land use affects the biodiversity and dominance structure of butterflies. The scope of work covered the selected fragment of the area subjected to various human economic performance.

The research was conducted in the ‘Krzywda’ field-and-forest Site occupying 172 ha (Fig. 1). The area consists of the land leaving in fallow, pastures, forests, meadows including about 68 ha of swamps supplied by three watercourses. An approximately 75 years’ old pine forest stand insulated by open areas is located on a hill in the central part of the area site. On the southern and northern side, the research facility is surrounded by a 40 years’ old pine stand growing in former agricultural soils. It borders on a 95 years’ old pine stand with an addition of oaks, birches and beeches on the west. The entire area is subjected to an experiment involving the artificial inhibition of succession processes by the cutting off and removing of the plant biomass. Additionally, the lay land was divided into the lay land mown with biomass not collected, lay land mown with biomass collected, unmown lay land with the tree and shrub undergrowth cutting out regularly. The main purpose of the facility is to monitor changes occurring in the fauna and flora as a result of the processes stimulated by human economic activities.

Figure 1

Research areas in the form of line transects representing various landform uses were established in the research facility. –

Transect A2–F2 – 25 years’ old fallow mown with biomass not collected (Fig. 2)

The length of a transect depended on the size of the form of land use and amounted to 500–600 m. The species content of vascular plants was determined in each of the transects. All specimens encountered in each research area from May to September 2017 were caught. They were caught with the use of an entomological net and their species were identified.

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Field observations have been conducted taking place from May to September in 2017. Five transects (600 m long) were selected in the Krzywda area site (Fig. 1). The form of use of the basic criterion for transect localization was the form of land use:

Results were summed up and presented in the table taking into account the species observed in each transect and the collected number of specimens (Tab. 1).

The domination structure of the communities of day moths was also determined. The division of the domination distribution into 6 classes was adopted in the classification: eurecedents (I, eR), recedents (II, R), subrecedents (III, sR), subdominants (IV, sD), dominants (V, D) i eudominants (VI, eD) (Plewka 2007). The classification involves the comparison of the numerousness of a species with the numerousness of the most numerous species. The division will help to come to conclusions regarding the domination structure. In this case, the dominant is the prevailing species, while the recedent is the receding species.

The domination structure was calculated according to the following formula: a=n6{\bf{a}} = \root {\bf{6}} \of {\textbf {\emph{n}}} where: a

– the boundary value for the lowest class obtained by getting the sixth rot of the number equal to the population size of the most numerous species. Boundaries of individual classes are determined by the values of consecutive powers of the ‘a’ number,

This action rule made it possible to evaluate the role of individual species in the community and the requirements of individual species concerning the form of land use. Final results were presented in the form of tables.

Throughout the entire research period, 32 species of butterfly were observed; they represented all the 5 families (Tab. 1). They equal about 20% of all species belonging to this group of animals that occur in Poland (Buszko, Masłowski, 1993). 606 specimens were caught. The Nymphalidae family turned out to be the most numerous one with 17 of the recorded species belonging to it. Another large family was the Pieridae with 6 species belonging to it. High variability of the spatial arrangement of individual species and their numbers was observed. Most species were found in the A2–G2 transect consisting of the 25 years’ old fallow land mown once a year with biomass not collected (27 species). The greatest number of specimens was also found in the same transect (217). The area established in the fallow-forest ecotone (L1–L6) also turned out to contain a great number of specimens where 207 of them were collected; however, they belong to a smaller number of species, that is, 22 species were found. The least number of species, that is, 13 of them were observed in the A3–F3 transect established in the mown fallow with biomass removed and the B5–G5 transect established in the unmown fallow. The least number of specimens was collected in the second of the transects mentioned above where only 28 specimens were observed. Lycena viregaureae turned out to be the most numerous species with 148 specimens recorded throughout the entire research period. Other numerous species were: Lycaena tityrus and Coenonympha pamphilus with respective 90 and 71 specimens caught. Such diversity of species of this group of insects can be attributed to the characteristics of land cover and the availability of different host plants for butterflies. Researchers have shown that host plant species affect the occurrence of butterflies (Tiple et al., 2007; Sagwe et al., 2015). Habitat heterogeneity also plays an important role in the biodiversity of insect species including butterflies (Ngongolo, Mtoko, 2013; Fitzherbert et al., 2006). It should be noted, however, that some of these habitats may support a large number of species and their diversity, while others may have a negative impact. This can be attributed to the high anthropogenic activity in these areas, which worsens the quality of the environment. Studies by many researchers show that through anthropogenic disturbances, they have shown a clear decline in the number of species and their quantitative distribution (Akite, 2008). The diversity and abundance of butterflies has decreased with intensive land use (Sagwe et al., 2015).

The domination of individual species of butterfly communities was determined. Table 2 presents the calculated domination position of individual butterfly species.

Lycaena virgaurea and Coenonympha pamphilus turned out to be eudominants in the mown fallow with biomass not collected (A2–F2). Dominants consisted of two species: Maniola jurtina and Lycaena tityrus. The group of subdominants consisted of 4 species: Pieris rapae, Polyommatus icarus, Aphantopus hyperanthus and Thymelicus lineola. The remaining 19 species can be classified as recedents of the receding species. The large number of eurecedents (13 species) most probably results from the presence of microhabitats (Plewka 2007). In principle, the least differentiation of the species domination was observed in the case of Lycaena virgaureae. The species occurred quite numerously in all transects; however, a tendency towards the preference of mown fallows with biomass not removed, unmown fallows with undergrowth pulled out and areas in the vicinity of the forest can be observed. One can observe a certain susceptibility of this species to stressful environmental conditions involving the mowing and disposal of biomass. Even though the species is ubiquitous and mobile, it preferred dry areas in the vicinity of forests, unmown fallows or mown fallows with biomass not removed. It was less numerous in transects with the more intense economic use and transects located in the vicinity of water reservoirs. Lycaena tityrus turned out to be the eudominant in the transect established on an unmown fallow with biomass collected (A3–F3); it also occurs less numerously in the areas close to forests (L1–L6) and waters (W1–W6), while it was classified as a receding species in an area that is used more intensely. Other species also classified as dominating were: Coeneonypha pamphilus as a dominant and Lycaena virgaurea as a subdominant. The remaining 10 species were classified as receding species. The unmown fallow (A5–G5) had two eudominants: Lycaena virgaureae and Vanessa atalantha. Inachis io was classified as a subdominant. Other species comprise a group of recedents (4 species) and group of eurecedents (6 species). Tymelicus lineola is eudominant in a habitat close to water (W1–W6) and subdominant in a mown fallow with biomass not collected (A2–F2), while it has not been recorded at all in the fallow with biomass removed (A3–F3). L. virgaureae turned out to be eudominant in the L1–L6 transect established in the fallow-forest ecotone, while 2 species were dominant: L. tityrus and C. pamphilus.

The correct structure of an ecosystem is characterized by a small number of numerous species and a large number of species that are less numerous (Trojan, 1998). This regularity can be observed in the case of the domination of individual species in the Krzywda area (Table 3). Most species with the class average amounting to 7.4 were found in the class of eurecedents, while the least number of species was found in the classes of eudominants and subdominants, where the average number of species amounted to 1.6 only. This phenomenon probably results from well-preserved functions of the ecosystem and resources necessary to species occurring there. In addition, large differences in the quantitative distribution of species in the different transects may indicate that the microhabitat conditions preferred by the different species are not the same (Sagwe, 2015). This is shown by some species of I. lathonia, which was caught only in the forest transect (L1–L6), or by the large number of L. virgaureae, where the difference between transects in the number of specimens caught between W1–W6 and L1–L6 was 73 specimens. The different dominance of individual species in the studied area may also result from the fact that some species have specialised in a specific group of plants (Franze’n et al., 2006). The occurrence of butterflies is obviously due to the characteristics of individual populations. Closed populations are comprised of settled butterflies and the imagines occur in very large numbers in a small area. The majority of such populations create metapopulations or local populations inhabiting isolated parts of the habitat between which they migrate. Open populations consist of more mobile species with the characteristic lack of barriers for the flow of genes. Such butterflies can move among various habitats. In turn, migrating species are the most mobile ones; they can travel even at the distance of a few hundred kilometres (Krzywicki, 1982; Sielezniew, Dziekańska 2010). We usually encounter metapopulations in the Krzywda area. Butterflies demonstrate preferences for specific habitats to a greater or lesser degree. A habitat of a butterfly has to satisfy its needs in each development phase. A host plant for both the caterpillars and for the imagines has to occur in such a habitat, there has to be space for the penetration and an appropriate microhabitat for the development of larvae (Buszko, Masłowski, 1993; Bellmann, 1999; Tolman, 2007; Sielezniew, Dziekańska, 2010, Mielczarek, 2016). Different types of disturbances, the removal of host plants has consequences for the butterfly population (Tiple et al., 2007). Butterflies are sensitive to anthropogenic changes (Murphy et al., 1990; Spitzer et al., 1997; Dale, Beyler, 2001). The destruction by human activities of naturally growing plants and habitats necessary for the development of all stages of butterfly development has a huge impact on the species impoverishment of this group of insects (Tiple et al., 2007). Varied landscape development will make it possible to guarantee areas that will satisfy the needs of larvae development, shelter and the maintenance of the habitat mosaic and surroundings of butterfly habitats in a good condition (Kędziora et al., 2010; Kalarus, 2016; Chrzanowski, 2017). Another danger consists of the plant encroachment on open areas as a result of the natural succession due to the cessation of extensive land management (Skórka et al., 2007; Conception, 2008) and of the intense management of largescale agricultural production that negatively impacts living organisms due to the unification of the agricultural landscape (Renetzeder et al., 2010). This is why mowing is so important to maintain the species diversity in open areas and also to inhibit succession processes to prevent the invasion of foreign plant species (Cremene, 2005; Johst et al., 2006, Skórka et al., 2007). There is no doubt that economic activities carried out in individual transects influenced the species content and the share of individual plant species that also provide feed for butterflies. Butterfly species occurring in the Krzywda Site are mostly eurotypical species. Their biotope mostly consists of open areas, especially meadows and fallows. They are encountered on dry turf, meadows, roadsides and grounds next to railway tracks. They can also occur in ruderal areas and in gardens, shrubby formations in the vicinity of forests or mid-forest meadows. Preferences of individual species were observed not only for a specific type of habitats but also for specific form of land uses. Varied prevalence of individual species was observed in each of the areas. The study showed that despite the relatively broad spectrum of habitats preferred by butterflies and their high mobility, the number of species as well as their quantitative occurrence were different depending on the form of land use.