Distribution of Crataegus (Rosaceae) in S-e Poland

POLISH JOURNAL OF ECOLOGY(Pol. J. Ecol.) 61 4 683–691 2013 Regular research paper Krzysztof OKLEJEWICZ 1, Eugeniusz CHWASTEK 2, Marian SZEWCZYK 3, Andrzej BOBIEC 4, Józef MITKA 5* Department of Botany, University of Rzeszów, Zelwerowicza 4, 35–601 Rzeszów, Poland Bielsko-Biała Academy of Józef Tyszkiewicz, Nadbrzeżna 12, 43–300 Bielsko–Biała, Poland e-mail: [email protected] 3 Institute of Agriculture, Jan Grodek State Higher Vocational Academy in Sanok, Mickiewicza 21 38–500 Sanok, Poland 4 Department of Agroecology, University of Rzeszów, Ćwiklińskiej 2A, 35–601 Rzeszów, Poland 5 Institute of Botany, Botanical Garden, Jagiellonian University, Kopernika 27, 31–501 Kraków, Poland *e-mail: [email protected] (corresponding author) 1 2 DISTRIBUTION OF CRATAEGUS (ROSACEAE) IN S-E POLAND ALONG A GRADIENT OF ANTHROPOGENIC INFLUENCE ABSTRACT: The impact of land use intensity on the taxonomic composition of hawthorns in four regions of south-eastern Poland was investigated. As a result of different human settlement histories, two of the regions are 54–64% forested nowadays, and the remaining two regions are 70–78% transformed into arable land. Numerical analysis and Monte Carlo permutation tests showed that the purely geographical component of the species distribution, linked with the land use intensity, was statistically significant (1.97%, P = 0.002), as well the pure site component (1.17%, P = 0.010). The human-induced opening of the landscape promotes Crataegus monogyna. Forests are occupied by C. laevigata, C. rhipidiphylla, C. rhipidophylla Gand. var. lindmanii and the hybrid C. × macrocarpa (C. rhipidophylla × C. laevigata); on forest edges the hybrid C. × media (C. monogyna × C. laevigata) tends to occur. Crataegus × subsphaericea (C. monogyna × C. rhipidophylla) is rare and tends to occur in thickets, and a triple hybrid C. monogyna × C. rhipidophylla × C. laevigata colonizes recently abandoned fields. Hybridization seems to be an efficient evolutionary strategy of hawthorns in the face of humaninduced transformations of the landscape. KEY WORDS: CORINE Land Cover, hawthorn, human impact, hybrids, landscape transformation, land use, species distribution journal 36.indb 683 1. INTRODUCTION Evolutionary processes in human-dominated landscapes are poorly understood, however, there is little doubt that human activities have altered them. They are best known from the population-genetic studies. For example, Pe rg ams and L a c y (2008), using museum and recently collected specimens, found rapid morphological and genetic (mtDNA) change in a population of white-footed mice in the Chicago region during the past 150 years. The other problem, to which little attention is paid, is the issue of the consequences of changing evolutionary trajectories of species that persist in human-altered environments (Sm it h and B e r nat he z 2008). Human impact is one of the most important factors changing the vegetation cover of the Earth, and results in synanthropization processes (Kor naś 1981, 1983). Some plants increase their ranges (hemerophiles), and at same time others decrease as an effect of human impact (hemerophobes). The most interesting group of taxa, is one in which the evolutionary response to human alterations is especially rapid. It forms a group of flowering plants with a flexible type of asexual reproduction, i.e. apomixis (C z api k 1996). To this group 2013-12-30 21:05:53 684 Krzysztof Oklejewicz et al. belong, among others, Taraxacum dandelions, Hieracium hawkweeds, Rubus brambles or blackberries, and Crataegus hawthorns. In hawthorns evolutionary change may be rapid and flexible due to pseudo-gamous gametophytic apomixis (Ta lent 2009). Also, rapid ploidy-level changes are possible if a meiotically reduced egg cell develops by parthogenesis, or if a meiotically unreduced egg cell is fertilized. These phenomena are almost always associated with hybridization (Ta le nt and Dick ins on 2005, L o et al. 2009). In Europe, hawthorns were taxonomically revised by C hr istens en (1992, 1997). In south-eastern Poland three basic taxa have been found: C. monogyna Jacq., C. rhipidophylla Gand. and C. laevigata (Poir.) DC., and three related nothospecies: C. × subsphaericea Gand. (= C. monogyna × C. rhipidophylla), C. × macrocarpa Hegetschw. (= C. rhipidophylla × C. laevigata) and C. × media Bechst. (= C. monogyna × C. laevigata). Additionally, we included an extreme morphological form of hawthorn represented by C. rhipidophylla Gand. var. lindmanii (Hrabětová) K. I. Chr., as well as forms described as a triple hybrid C. monogyna × C. rhipidophylla × C. laevigata (Holub 1992). Generally, information on the ecological preferences and amplitudes of the species and nothospecies of hawthorns is absent. The genus Crataegus is known for its polyploidy and gametophytic apomixis. Apomixis and reproductive barriers between cytotypes are factors that reduce the frequency of gene flow among populations, and may ultimately led to allopatric speciation (L o et al. 2009). In this way, agamic complexes form evolutionary potential to promote new genetic variability and ecological varieties. D i ck i ns on et al. (2008) pointed out that human disturbance of the landscape may have diversified originally diploid sexual lineages as a result of polyploidy and agamospermy, including reticulate evolution (L o et al. 2010). The aim of this paper is to reveal the general ecological profiles of the hawthorns in four regions of southern Poland, with different histories of human settlement. Our main hypothesis is that the taxonomic differentiation of hawthorns in the particular regions is associated with the different patterns of land use. The relatively undisturbed region of the Beskid Niski Mts with the youngest settlement history and large share of forest areas, Fig. 1. Localization of the four study regions in south-eastern Poland in the ATPOL grid. A map courtesy of A. Zając and M. Zając, Laboratory of Computer Chorology, Institute of Botany, Jagiellonian University. journal 36.indb 684 2013-12-30 21:05:54 Crataegus in man-made landscape 685 Fig. 2. The land use categories according to the CORINE Land Cover database in the regions under study. The figure does not consider wet areas and water bodies that form altogether 0.02% in the Beskid Niski and 1.5% in the Pogórze Przemyskie. should be dominated by a specific group of species. On the other hand, the region of the Przedgórze Rzeszowskie, which has been disturbed by human intervention, has to be supposedly characterized by the occurrence of the hybridogenous species of the genus. Specifically, we expect that each of the regions with a unique land use pattern has different share of hawthorn species. The main premise of the studies is that the origin and spread of hybridogenous species was facilitated by the opening of the landscape. 2. STUDY AREA AND METHODS The hawhtorns were collected in three physiographic units within the Polish Western Carpathians: the Beskid Niski Mts, Pogórze Przemyskie (Przemyskie Foothills), and Pogórze Strzyżowskie (Strzyżowskie Foothills). The specimens were dried, attached to paper sheets and labelled in a standard manner, and deposed in the herbarium of Institute of Botany, Jagiellonian University (KRA). The fourth physiographic unit, the Przedgórze Rzeszowskie (Rzeszowskie Foothills) are located the most northwards and belongs to the Kotlina Sandomierska (Fig. 1). Here, mainly podzolic soils occurs, in contrast to the brown soils in the Carpathian area. The Beskid Niski and Pogórze Przemyskie regions are characterized by large complexes of forests and relatively well preserved natu- journal 36.indb 685 ral plant communities. The Beskid Niski is the most diverse area in terms of topography and geology. It includes the highest altitudes, rich relief and many variants of flysch bedrock (B a l on et al. 1995). The Pogórze Strzyżowskie is characterized by deep and narrow folds formed by the soft geological substratum creating great site diversity. It is a rural area with extensive farming and scattered forests. The Przedgórze Rzeszowskie is the most distinct of the three areas and is characterized by small height differences, high human impact and almost total deforestation (Fig. 2). In the Pogórze Przemyskie (especially its northern part) and eastern part of the Przedgórze Rzeszowskie the linear pottery communities are dated back to the Neolithic times (C z ekaj - Z ast aw ny 2008). In historical times they were settled relatively early, in the 14th century. The second wave of settlement, dated to the 15th–17th centuries, is related to the colonization of the Beskid Niski (L a ch 1968, G órk a 1995). The area under study is differentiated according to the historical and present impact of man. The Beskid Niski belongs to one of the most forested regions in Central Europe. Forests cover 64.5% of its area (Fig. 2). In the 19th century overpopulation of the area of the Beskid Niski led to extensive deforestation. The process ceased after 1945, triggering successional changes leading to the recovery of forest communities on abandoned meadows 2013-12-30 21:05:54 686 Krzysztof Oklejewicz et al. and fields (L ach 1968, L ach and Z i ę t ar a 1989). Recently, they have been turned to fallows dominated by invasive plant species as Solidago canadensis and Heracleum sosnowskyi. According to the CORINE Land Cover database, we specified a percentage of the particular land use categories: Arable land, Forests, Wet areas, Water bodies, Meadows and Anthropogenic sites (Fig. 2). The occurrence of eight taxa of Crataegus was checked using a systematic-random sampling in all squares 2 × 2 km of an ATPOL system (Fig. 1). In total, 1429 records were entered. We recognized, at each sample site, the taxon of Crataegus, the type of plant community, exposure and altitude (m above sea level). In order to secure the methodological consistency all field data were collected by the same team and species determinations were done by one of us (KO). In the trial project a DCCA analysis was used for the calculation of the longest underlying gradient in the data set. The longest length of gradient was 2.662 SD. It was close to 3.0, a value which delimits the use of the linear or unimodal model of species response (L epš and Šmi l auer 1999). Thus, we used both models: a linear with Redundancy Analysis RDA and a unimodal ordination method, namely the Canonical Correspondence Analysis CCA (ter Braa k 1987). The explanatory data set includes both the geographical (regions of occurrence, the CORINE Land Use Categories) and site (type of plant community, exposure and altitude) variables (see Fig. 3). The nominal (qualitative) variables were coded as 0/1 dummy variables. In order to establish how much variance is explained by the site vs geographical variables, a variance partitioning procedure, as described by B orc ard et al. (1992), was carried out. By making two canonical ordinations, each of them constrained by one of the sets of explanatory variables: namely the site and geographical, one can obtain a measure of the total importance for the species data of (1) the effects of the site conditions and (2) the geographical structure. Additionally, some species and site variables may share a common spatial structuring that has been calculated by the subtraction of the partial effects of the site and geographical vari- journal 36.indb 686 Fig. 3. CCA (a) and RDA (b) of Crataegus in south-eastern Poland with environmental and geographical variables as explanatory factors of species distribution. laevig – C. laevigata, lin – C. monogyna var. lindmani, monog – C. monogyna, × macro – C. × macrophylla, × media – C. × media, × subs – C. × subsphaericea, triple – triple hybrid. BNiski – Beskid Niski, PPrzem – Pogórze Przemyskie, PRzesz – Przedgórze Rzeszowskie; AN– anthropogenic sites, including road and rail embankments, AR – agricultural areas, BO – boggy and wet sites, FO – forest sites, ME – meadows, WO – water bodies; Forest – forest sites, Edges – forest ecotones, Fallows – former agricultural land and balks, Anthrop – anthropogenic sites, including road and rail embankments, Thicket – isolated dense stands of tall shrubs; E – east, SW – southwest, N – north, NE – north-east, S – south, SE – south-east, W – west, NW – north-west, ExpNull – no exposure, alt – altitude (m above sea level). ables. The significance of the first canonical axis and all canonical axes were checked by a Monte Carlo permutation test – unconstrained permutations in a reduced model in 499 runs. The reduced model method better 2013-12-30 21:05:55 Crataegus in man-made landscape maintains the Type 1 error in small data sets. The frequency data of the CORINE Landuse Categories in particular regions were angular transformed according to the formula x’ = SQRT ARCSIN (x). The permutation tests of significance of all correspondence canonical analysis CCA axes calculated the Trace statistics, i.e. the sum of all canonical eigenvalues, in relation to the total inertia, i.e. the sum of all eigenvalues. In that way the significance of speciesenvironmental relations in the direct analysis was explained, in 499 random permutations. In order to evaluate the explanatory power of the particular quantitative and qualitative variables, the forward selection procedure was applied, using the partial Monte Carlo permutations in 499 runs. At the beginning of the procedure each explanatory variable was tested separately to estimate its independent, marginal effect. Then, the best explanatory variables were consecutively added to the model and each time the effect of the added variable was calculated, i.e. its conditional, partial effect was estimated. The calculations were carried out with the use of the CANOCO for Windows software, and the graphics with the use of the Canodraw for Windows (ter Bra a k and Šmi l auer 2002). 3. RESULTS The Monte Carlo test of significance of the first canonical axis of CCA (eigenvalue = 0.201) gave F-ratio 42.666 687 and P = 0.002, and significance of all canonical axes (Trace = 0.322) F-ratio = 3.613 and P = 0.002. Similarly, in RDA the significance of the first canonical axis (eigenvalue = 0.062) gave F-ratio = 95.238 and P = 0.002, and significance of all canonical axes (Trace = 0.073) gave F-ratio = 5.907 and P = 0.002. We checked the importance of the geographical, as well as the site factors affecting the distribution of Crataegus species in southeastern Poland. A variance partitioning shows that both groups of variables explain, statistically significantly, the species variability. The purely geographical component of the species distribution is negligibly more important (1.97%, P = 0.002) than the purely site component (1.17%, P = 0.010, Table 1). The results of CCA and RDA are given in Figs 3a and b. For CCA the total inertia equals 6.946 and the Trace 0.322 (Table 1). In both analyses Axis 1 describes a geographical gradient of species distribution among the Beskid Niski vs Pogórze Rzeszowskie and Pogórze Przemyskie. The Pogórze Strzyżowskie has a different position, located at Axis 2, and is characterized by a large share of fallows. According to the CCA analysis, here the triple hybrid found optimum conditions, RDA showed rather C. × subsphaericea. The forward selection of the explanatory data shows that the region of the Beskid Niski and occurrence of meadows (ME) contribute mostly to the species variability (Table 2). Similarly, SW exposition, Forests, ExpNull, Fallows and Edges can be considered as important variables. Crataegus monogyna seems to be asso- Table 1. Partitioning of variation of a species data explained by Environment and by Region. Environmental characteristics include the type of plant community, exposure and altitude. Trace – sum of all canonical eigenvalues; P – corresponding probability value obtained by the Monte Carlo permutation test, 499 random permutations. Component   a b c d e Source   Site+Region Site Region Covariation between b and c Unexplained 0.310 0.173 0.229 0.092 6.636 f g d+e+f+g Pure Site* Pure Region** Total 0.081 0.137 6.946 *Region set as covariable **Site set as covariable journal 36.indb 687 Trace F-ratio P % Variance Analyses without covariables 3.670 0.002 4.46 2.416 0.002 2.49 12.191 0.002 3.30 1.32 95.54 Analyses adjusted for covariables 7.290 0.010 1.17 9.713 0.002 1.97     100 2013-12-30 21:05:56 Krzysztof Oklejewicz et al. 688 Table 2. Ranking environmental variables in importance in the unimodal (CCA) and linear (RDA) models by their marginal (left) and conditional (right) effects of the ecological factors (see Fig. 3), as obtained by the forward selection (Lambda1 = fit = eigenvalue with a variable only); LambdaA = additional fit = change in eigenvalue); P = significance level of the effect, F–ratio = as obtained with a Monte Carlo permutations under the full model with 499 permutations. Only variables with P ≤ 0.05 are shown. For variables explanation see Fig. 3.   Variable CCA BNiski ME ExpNull alt SW Fallows Forests Marginal Effects Lambda1 Conditional Effects LambdaA   P   F-ratio 0.16 0.05 0.01 0.14 0.01 0.03 0.03 0.002 0.002 0.004 0.002 0.014 0.014 0.040 33.16 7.88 4.93 4.28 2.69 2.68 2.03 BNiski ME alt SW Forests Edges 0.05 0.01 0.05 0.00 0.01 0.00 0.16 0.03 0.02 0.02 0.01 0.02 0.01 RDA 0.05 0.00 0.01 0.00 0.01 0.00 0.002 0.002 0.002 0.006 0.010 0.018 68.95 13.83 8.26 4.48 3.42 2.78 Fig. 4. Distribution of Crataegus species and nothospecies in south-eastern Poland along a human-induced ecological gradient of influence based on numerical analysis of 1429 records on the ATPOL grid. laevig – C. laevigata, rhipid – C. rhipidophylla + var. lindmanii, monog – C. monogyna, × macro – C. × macrophylla, × media – C. × media, × subsph – C. × subsphaericea, ‘triple’ – triple hybrid. ciated with the Przedgórze Rzeszowskie having the longest history of settlement and the largest proportion of arable land. The Beskid Niski is largely forested; here three taxa, C. rhipidophylla, C. × macro and C. lindmanii found optimal circumstances. The most diversified region is the Beskid Niski, where forests, thickets and forest edges prevail. Within the region, C. rhipidiphylla and C. × macrocarpa found optimum occurrence. Crataegus monogyna is mainly confined to the Pogórze Przemyskie and Pogórze Rzeszowskie, in flat areas. Here anthropo- journal 36.indb 688 genic communities prevail. The Pogórze Strzyżowskie is characterized by the occurrence of recent fallows and the optimum of occurrence of the triple hybrid. Crataegus laevigata, C. × media and C. × subsphaericea occupy outlier positions, however at the opposite ends of the Axis 2 (Fig. 3). To sum up, the distribution of Crataegus in the Western Carpathians is statistically significantly shaped by the geographical component, connected with the various types of human impact. A clear gradient was found among two species: C. monogyna and C. lae- 2013-12-30 21:05:57 Crataegus in man-made landscape vigata agg. that tend to occupy opposite ends of the human impact gradient. The intermediate position is filled by the hybrid species (Fig. 4). 4. DISCUSSION All the hawthorn species in Poland are syntaxonomically classified as characteristic of the Rhamno-Prunetea class (Matus z k i ew icz 2006, Z aj ąc and Z aj ąc 2009). Floristic studies carried out in the second half of the 20th century in the Western Carpathians also point to their occurrence on forest edges and in thickets (Z emanek 1989, Z e manek and Winnick i 1999, Ok lej e w icz 1993), fallows (Jasie w icz 1965, B ar ab as z - Kras ny 2011), rail embankments and balks (Towp asz 1987). Similarly, intensive botanical studies in the Pogórze Przemyskie by Wolanin (unpublished) point to a wide spectrum of hawthorn occurrence in forests, on forest edges, in thickets, glades, on xerothermic grasslands overgrown by shrubs, in balks and fallows and on rail and road embankments. Crataegus rhipidophylla and C. monogyna have the widest ecological niche. They are distributed throughout the whole region under study, however our analyses point to their demarcation along the ecological gradient. While Crataegus rhipidophylla is strongly associated with forest communities and forest edges, C. monogyna is the most frequent in open anthropogenic sites. Recently, Crataegus spp. were studied in Flanders (Belgium) by D epy p e re et al. (2006). The authors found that, morphologically, C. monogyna and C. laevigata are easily recognized species, however their hybrid C. × media showed a remarkably large range and overlapped with both parental species for most of the studied traits. According to Belgian botanists (cited in D epy p e re et al. 2006) in Flanders, C. × media displays better adaptability to changing environments than C. laevigata. The latter species is rare in the area under study, but its hybrid is common and occupies an intermediate ecological niche between the parental species, on forest edges. The other result of the morphological investigations concerned C. × subsphaerica, a hybrid between C. monogyna and C. rhipidophylla. In Flanders, its morphology is hardly journal 36.indb 689 689 distinguishable from C. monogyna, which is a planted species, found in old hedges to delineate field boundaries and to provide a barrier to grazing livestock. On the other hand, C. laevigata is less common in Flanders and it is characteristic for old hedges and wood banks on richer soil types (D epy p e re et al. 2006). Our results show that C. × subsphaericea occurs, similarly to C. monogyna, in regions under strong anthropogenic impact, where it forms dense thickets. Similarly, another hybrid C. × macrocarpa (C. laevigata × C. rhipidophylla) is ecologically close to one of its parents, i.e. to C. rhipidophylla. In fact, the parental taxa and its hybrid tend to occur in forest plant communities. Hybridization in some plant genera is quite common. It enhances the degree of variability in fitness among different hybrid genotypes. In consequence, hybridization need not be an evolutionary dead end (R i es eb e rg and C ar ne y 1998). The significance of hybridization in the context of biodiversity maintenance was critically discussed by S e ehaus e n et al. (2008). They note that, on the one hand, hybridization may contribute to an increase in species numbers by enhancing evolutionary potential, but, on the other hand, it may effectively reversed speciation. In fact, our results show that C. laevigata is a rare species, and its hybrid C. × macrocarpa is much more frequent in the forested Beskid Niski. It seems that C. laevigata may collapse in a hybrid swarm here, as a result of reduced population density, a hypothesis that should be verified by systematic observational and experimental studies. Our results strongly support the view expressed by Kor naś (1981) that the breaking of the ecological barriers brought about by human intervention may lead to creation of new nothotaxa. The newly originated – as an effect of humaninduced open landscapes – biotypes (antrophyta anthropogena) are often expansive and could have given rise to, for example, many central European meadow species (L and olt 1970, S cholz 1975). Two hybrid nothospecies: C. × subsphaericea and the triple hybrid deserve more attention. They are relatively rare, especially the triple hybrids, and gravitate towards regions transformed by humans. The rarity of Crataegus × subsphaericea may be explained by the fact 2013-12-30 21:05:57 Krzysztof Oklejewicz et al. 690 that it is the hybrid between parents with different, non-overlapped ecological profiles. The question is whether its occurrence in patches of bushes in the open landscape is merely a random effect, or it is a divergent adaptation of the hybrid species. Similarly, the occurrence of the triple hybrid in relatively young fallows in the Pogórze Strzyżowskie also need further observations on the dynamics of the process. In conclusion, the prolonged, i.e. dating to Neolithic times, activity of man in southeastern Poland seems to be an important evolutionary factor shaping the taxonomical diversity of hawthorns. The opening of the landscape and the creation of novel habitats disrupted dispersal barriers and promoted gene flow between otherwise isolated genotypes and made the hybridization of hawthorns much easier. In effect, new genetic combinations arose that underwent natural selection. The process has been continuing and may have led to the generation of new hawthorn species, to fit the rapidly changing anthropogenic sites. ACKNOWLEDGMENTS: The study was financially supported by the Ministry of Science and Higher Education/National Science Centre of the Poland (N N305 221537). 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