MORPHOLOGICAL VARIABILITY OF INVASIVE SPECIES …

Goran Anačkov, Slobodan Bojčić, Vladimir Ječmenica,... 27

International Symposium: Current Trends in Plant Protection UDK: 632.51:582.988.1(497.113) Proceedings

MORPHOLOGICAL VARIABILITY OF INVASIVE SPECIES

AMBROSIA ARTEMISIIFOLIA L. (ASTERALES, ASTERACEAE)

ON THE IMPORTANT TRANSIT AREAS

GORAN ANAČKOV, SLOBODAN BOJČIĆ, VLADIMIR JEČMENICA, MILICA RAT, RUŽICA IGIĆ, PAL BOŽA

University of Novi Sad, Faculty of Sciences, Department of biology and ecology

mail: [email protected] Investigations and distribution monitoring of invasive species in Vojvodina are mainly based on the degree of natural and agricultural ecosystems decreasing by invasive alien plants. The studies that are omitted are biology of alien species, their adaptive mechanisms and physiology in order to find answers related to their accomplishments on the new habitat. For those reasons, samples in this study were taken from different habitat types to get final data about mechanical treatment as a tool for eradication of Ambrosia artemisiifolia L., depending on different habitats type, and to provide data for developing of effective measurements. The results are analyzed by descriptive and multivariate statistics. Conducted investigations have shown that in some, especially the poorer soil types, species A. artemisiifolia shows extraordinary capabilities of adaptation in terms of survival and biomass production. Key words: invasive species, common ragweed, adaptation, phenotypic plasticity,

INTRODUCTION

As one of the most interesting evolutionary mechanisms, it is considered a form of adaptive differentiation and in accordance with that natural selection (Schulter, 2000). The fact is that selection pressure in the natural environment affects many levers of adaptive radiation and allows normal historical changes in the ecosystem units, occurrence of adaptation, specialization and phenotypic neo-speciation (Takhtajan, 1991). Invasive species have ability to accelerate certain processes, characterized by adaptive mechanism, and soon they become members of the phytocoenological structure in new habitats. At that moment they begin to modify it, causing destructive changes and finally its extinction (Myers and Bazely, 2003). Such changes are part of the essential biological transformations and they present the basis for the observation of genetic diversity, which explains their adaptive divergence. One of the mechanisms is multiple introductions of species in new habitats as well as mixing of primary and secondary introduced populations that enriches the genetic composition. In this way remarkable adaptability and evolutionary advantages that have invasive species is created. One of them is certainly Ambrosia artemisiifolia, which in its history shows all the elements of the genetic basis for the successful propagation range (Jin Chunet al., 2011).

28 Morpfological variability of invasive species ambrosia artemisiifolia L.,...

In Vojvodina, 147 invasive plant species have been identified (IASV, 2011). Invasive alien species (IAS) develop specific adaptation mechanisms to the ecological conditions in new conquered habitats. In this way, stable populations are established, and they are the centers of species spreading to the natural habitats and surrounding nonnative ecosystems (agro-ecosystems). The degradation of habitats enables invasive alien plants spreading and naturalizations, and in the same time they disturb the ecological balance of ecosystems. Invasive nature of these plants is result of their high adaptability, absence of natural enemies and easy adaptability to sudden changes in the general environmental conditions (Jaric, 2009). In the Serbia during last centuries three Ambrosia species were recorded: Ambrosia artemisiifolia L. 1753 (common ragweed), A. trifida L. 1753 (giant ragweed) and A. tenuifolia Spreng. 1826 (field ragweed). Common ragweed is only species which is naturalized in nature, and giant ragweed is in the adaptation phase. Field ragweed was recorded only once, in 1995th in the wider area of Novi Sad, near rail station (Boža, 2002). For this record herbarium sheets exists in Herbarium BUNS, but after this data, no more data were provided, so it can be concluded that it was just one accidentally introducing of the seeds. A. artemisiifolia L. is one of the most invasive alien plants distributed in Europe. Ragweed is introduced in a botanical garden as a cultivated species in the mid XVIII century. In the 1880 it was detected in natural habitats in two districts, and in 2004 in 63 districts in France (Dessaint et al., 2005). Today, regions with the most abundant populations of ragweed in Europe are Valley Roneu in France, northern Italy and the Pannonian plain (Juhász, 1998). In Vojvodina, ragweed inhabits mostly ruderal places. Common ragweed is introduced in the northern part of Serbia at the beginning of the twentieth century, although the first records dates from 1953 (Slavnić, 1953). Ten years earlier was noted for the first time in neighboring Croatia (Galzina et al., 2010). From entering in the Pannonian part of Serbia to the first data recording, common ragweed has succeeded in overcoming the initial adaptation and began spreading extensively. As a pioneer plant, common ragweed occurs along the roads, railroads, abandoned places, wastes, but also as a weed of small grains, row crops, orchards and vineyards (Boža, 2011). Recently, it is expanded into the closed phytocenoses and grasslands, especially in arid areas (Sărăteanu et al., 2010), such are majority in Vojvodina. In this way, ragweed has become almost obligatory member of vegetation in the natural habitats and present a threat to the habitats such are steppes on loess and sand and saline grasslands. In forest ecosystems is not present, except in the planted forests of alien species black locust and poplar forests, where it may survive and develop stabile populations (Boža et al. 2002). The problem of ragweed massive presence is also its influence on human health. Ragweed pollen is one of the most dangerous allergens in the air for the man, which can cause diseases such as asthma, rhinitis and conjunctivitis. Additionally, ragweed is contact allergenic plant, which causes local changes on the skin (Igić and Boža, 2012). Intensive agricultural production in the Pannonian basin is primarily consequence by quality of pedological substrate. However, the area is opened for the spreading of alien species. Given that the land is constantly treated and refined for the cultivation, this situation and organic component of the substrate correspond to the initial expansion of invasive weed species. For these reasons, the treated areas (agricultural sites) are one of the main centers for spreading of invasive species. Problems with invasive species and their control are not new. Investigations and distribution monitoring of invasive species in Vojvodina are mainly based on the degree of natural and agricultural ecosystems deficiency by invasive alien plants. Should not be


ignored the fact that new species in the newly conquered habitats have no natural enemies of an IAP. Most of these species belongs to the group of an allergen plants, and prevent actions for the timely removal of them for reducing higher concentrations of pollen in the air are founded every year. Biological and mechanical control methods are the primary models for struggle with invasive species in natural and urban ecosystems (Wittenberg and Cock, 2001). Significant resources are spent on their removal, however, insufficient for the study of their invasive nature. One reason for the unsuccessful struggle should be sought in uneven prevention methodologies in Europe, as well in the absence of any treatment in certain regions (Gerber et al., 2011). Combine methods of mechanical and chemical treatments do not show significant changes compared to the purely mechanical treatment. Successively mowing has the effect in natural habitats, but much higher in controlled conditions (Holst, 2009). The problem is the individual capacity of local populations and the size of the adaptive response to current environmental impacts. This is a consequence of the previously mentioned genetic basis of adaptive potential. The local ragweed populations have the ability to adapt quickly, even if a several ragweed species grow in the same area (Fernández-Lamazareset al., 2012). Additionally, it is necessary to conduct studies that are aimed to establish long-term strategy and efficient destruction mechanism of such species. In accordance with these objectives were set the goals for this work: to determine the pace of growth and production of invasive species A. artemisiifolia L. on different substrates correlated with the method of mechanical removal of plants.

MATERIALS AND METHODS

Plant material was collected at three localities in Vojvodina, in Novi Sad (Fig. 1, Table 1). Selection of sites was made on the basis of experience in dealing with the species habitats. For A. artemisiifolia, typical ruderal habitat types and locations were selected in urban settlements. A total of 90 plants samples were taken, with 30 samples from each site. Stable populations were chosen, with a significant number of individuals that are successfully developed at that locality. The second character for the site selection was pedological substrate and each population is characterized by pedological individuality (Table 1). All the measurements for analyzed characteristics were carried out at the stage of full flowering. Measurements were performed in the sites, after which the plants were cut at the height of 30 cm, and the measurements were repeated after 30 days. Leaf area is measured in the laboratory. Plants were labeled with standard signs of operational taxonomic units (OTU). Material was deposited in the taxonomic collection in the Herbarium BUNS at the Department of Biology and Ecology, Faculty of Sciences, University of Novi Sad. Leaves taken from plants are also marked with OTU compatible units. Table 1: Localities of sampled material

Locality Substrate characters GPS coordinates

Novi Sad sand 45o15'59.58"SGŠ 19o51'47.34"IGD

Novi Sad clay-sand 45o16'28.97"SGŠ 19o50'34.62"IGD

Novi Sad construction material 45o14'52.44"SGŠ 19o47'06.23"IGD


Figure 1: Localities of sampled material, cadastral map of Novi Sad city (Public Enterprise for City Construction and Development, modified)

Field measurements were performed by standard measuring instruments and floating-gauged measurement tool with the precision level 0.01. Leaf area was measured using LI-COR Bioscientific portable leaf area meter, model LI-3000. Analyzed characters were selected based on diagnosis taken from floras from species native range (Flora of North America, 2008) and species allochthonous range (Gajic, 1975; Vasic, 1986). Characters are grouped according to plant regions (Tables 2, 3: Fig. 2). After mechanical treatment, characters related to the pollen production were observed. All data from the field/laboratory protocols are synthesized into an electronic database created in MS software, Microsoft Excel 2007 for Windows. Data were analyzed by descriptive, parametric and multivariate analysis in software package Statistica for Windows ver. 10 (StatSoft, Inc., 2011).


Table 2: Morphological characters measured before mechanical treatment

Plant organe Characters

Stem

Height Noduse position

First internode length Middle internode length

Terminal internode length Node with first branch

Node with first fertile branch

Leaf Total number

Area

Inflorescence

Total number Terminal inflorescence length

Length of lateral inflorescences 1 Length of lateral inflorescences 2

Figure 2: Elements of morphometric analysis before mechanical treatment: 1. terminal inflorescence length; 2. lateral inflorescence length D1, 3. lateral inflorescence length L2; 4a. terminal internode

length; 4b. middle internode length; 4c. first internode length; 5. node with the first fertile branch; 6. central leaf; 7. node with the first branch; 8. height (modified from Flora of North America, 2008)

Table 3: Analyzed morphological characters after mechanical treatment

Plant organe Character

Stem Node with first branch

Node with first fertile branch


RESULTS

Results of descriptive statistical analysis for 13 quantitative characters of A.

artemisiifolia showed high variability for most of the characters. The characteristics of importance for the interpretation of biological production and biomass formation were stem height (SH) and middle leaf area (MLA) (Table 4). Stem height processed by descriptive statistics showed that data from population on clay-sand varies within the temperate zone with coefficient of 11.17%. Pronounced variability for same character inside temperate zone is obtained for the data from population on construction sites, with a coefficient of variation 18.48%. For the MLA variability is obtained inside temperate zone for populations on sand and clay-sand, while the population from construction sites is characterized by expressed variability of 39.69%, higher than the value of standard deviation and has a significantly higher mean value 22.18 cm2 (Fig. 3). Values obtained by descriptive statistics for all three populations, clearly indicate moderate variability of character stem height (16.43%), while expressed variability of MLA (39.71%) indicate the minimum and maximum values (Fig. 4). These characters are one of the main levers of species invasiveness poll and of particular importance is their inter-population stability.

Figure 3: Basic statistical parameters for the characters stem height and middle leaf area from different pedological substrates A: Population on sand; B: Population on construction sites;

C: Population on clay-sand.

Figure 4: Summary of descriptive statistics for characters stem height and middle leaf area


The character ‘total number of inflorescences before cutting’ (TNIBC) analyzed by descriptive statistics indicate pronounced variation for two populations, and the coefficient of variation (40.41%) is significantly high in the population sampled at construction sites (Fig. 5). The coefficient of variation for the character ‘total number of inflorescences after cutting' (TNIAC) in all three populations are more than 30%, although smaller variation of the analyzed character is noticed in populations from clay-sand (Fig. 6, Tab. 4).

Figure 5: Basic statistical parameters for the characters ‘total number of inflorescences’ before

and after cutting. A: Population on clay-sand; B: Population on construction site; C: Population on sand.

Figure 6: A summary of descriptive statistics for the character ‘total number of inflorescences’ before and after cutting.

Table 4: Coefficient of variation for selected morphological characters of A.artemisiifolia

Stem height Middle leaf

area Inflorescence no. before treatment

Inflorescence no. after treatment

Population on sand

11,82% 19,18% 33,06% 82,14%

Population on constructed site

18,48% 39,69% 40,41% 65,71%

Population on clay-sand

11,17% 18,04% 26,81% 87,56%

All populatins 16,42% 39,71% 34,32% 78,98%


Using multivariate statistical method of discriminant analysis, a priori defined populations of common ragweed are tested. Compared to the first discriminant axis (75% sample variability) populations on clay-sand and construction site were separated, but the population on the natural soil (sand) has considerably more uniform characteristics. According to characters that define the variability on the second axis, population on sand is partially separated (Fig. 7). Characters that contribute most to discrimination are SH and leaves number, which follows the previous character, as well as total number of inflorescences. In relation to these characteristics the first two populations are significantly different. Besides characters by which the separation is performed on first axis, to partial separation of individuals on the second axis contributes characters number of nodes and length of terminal and lateral inflorescences (Table 5).

Figure 7: Positions of analyzed individuals in the area of the first two discriminant axes, (blue:

sand; red: construction site; green: clay-sand) Table 5: Load levels for quantitative characters of analyzed A. artemisiifolia populations

character DA 1 DA 2

Stem height (cm) -1.03294 1.29487

The number of stem nodes 0.45887 -1.04201

First internode length (cm) -0.30352 0.21460 Middle internode length (cm) 0.31373 0.48901 Terminal internode length (cm) -0.07362 -0.03511 Node with first branch 0.15064 -0.13993 Node with first fertile branch 0.45483 -0.46194 The number of leaves -1.22594 -1.10257

Middle leaf area (cm2) -0.33375 0.05487 Total number of inflorescences 1.28461 0.11636 Terminal inflorescence length (cm) 0.29838 1.10207

Length of lateral inflorescences 1 (cm) 0.54342 -0.13671 Length of lateral inflorescences 2 (cm) -0.02151 -0.92707

characteristic value 3.35724 1.10494 cumulative effect 0.75238 1.00000


Figure 8: Correlation between characters ‘node with first fertile branches’ before (green) and

after (red) mechanical treatment Character ‘node with first fertile branch’ showed a significant depending on the substrate type. Plants from populations with arid ground (sand), fertile branches formed on the second or third nodes before mechanical treatment, while after the treatment node with first fertile branches is significantly higher. Population from clay-sand, which is characterized by increased level of humidity, fertile branches have appeared at an extremely high nodes, while after the mechanical treatment they were significantly lower (third node), or even in some cases on ground node (Fig. 8).

DISCUSSION

Conducted investigations have shown that at some, especially the poorer soil types, species A. artemisiifolia shows an extraordinary capability of adaptation in terms of survival and biomass production. The results indicate that stem height is a more or less stable character while leaf area has an intense variability (Table 4). Favoring the character leaf area is a way of adjusting to environmental conditions, with strategy of faster completion of the life cycle and propagulume production in conditions of temperate-continental climate with arid character, then a character that indicates the quality of the habitat. Substrate characteristics enabled the preference of the character leaf area and stability of character stem height, since compared to the poorer substrate characters are significantly different (Fig. 5, 6). These features have undergone changes comparing to provide data (Fig. 6, 10) in the indigenous floras (Flora of North America, 2008 el. Ver.) and floras for allochthonous region (Gajic, 1975; Vasic, 1986). Populations’ individuality are confirmed by data obtained by discriminant analysis for the combination of morphometric and meristic characters. These characteristics are variable because they are not polygenic determined and they are conditioned by various environmental factors. The common response of the population has been confirmed by a priori classification, which is reflected in discriminant analysis in the compactness of population scores for each population individually (Fig. 7, 13). Characters that significantly contribute to such populations’ distribution in both cases are almost the same. Stem height is responsible for the associativity of population scores, because it has a low intra-population and pronounced


inter-population variability. Character leaf area is associated with the nutrients amount and substrate moisture. The characteristics of inflorescence region were used for the interpretation of pollen and propagulumes production. Analyzed results have more expressed variability in comparison to characteristics of the vegetative organs (Table 5, 7). Their effect on the total variability and segregation of populations are significantly reduced due to increased inter-population variation (Table 4, 6). Regardless to the substrate nature, nutrient amount, locality, even the species, the character inflorescence number is highly variable (Table 4, 6) and have a significant loading degree in populations differentiation (Fig. 7). The high variability of the generative organs was obtained only for characters such as inflorescence number, inflorescence length, etc. Variability is not related to the generative region sensu

stricto (flower and fruit characters), but to inflorescence. The inflorescence organization contributes to the development of a large number of stamens and fruits. Model of mechanical treatments as a method for removing of potentially allergenic species is generally accepted, but the justification is often discussed (Host, 2009). The results of corresponding analysis prove justification of this method. Mechanical removal of ragweed - cutting at the correct height before initial development of generative buds significantly reduces the development of flowers and pollen (Boža et al., 2006). Values for characters inflorescence number, length and position obtained after mechanical treatment, are also different. The inflorescence variability was confirmed and after mechanical treatment. After removing of fertile branch retains the high variability of the inflorescence characters, which point to the conclusion that this is a characteristic of this plant group. Increased variability after treatment is the result of the plants individuality in order to solve the problem of propagulume production. The position of nodes, where the first fertile branch is developed after mechanical treatment is also characteristic that allows a high degree of individual plants variability. This feature is part of their strategy that allows creations of individuality with aim to overcome emerging environmental conditions in nature. Increased/decreased variability of certain characters analyzed in this paper provides a better understanding of the nature of common ragweed in the area of the Pannonian plain. Of particular interest is information related to the mechanical removal and achieved effects. The individuality which is shown in this study, in response to the soil content and especially at the post-mechanical development of fertile branches, indicates significant changes in strategy against this model of adaptation of invasive plant species, favoring methods that are characterized with more intensive and better-formed prior to the monitoring mechanical treatment.

REFERENCE

Boža, P. (2011): Taxon: Ambrosia artemisiifolia L. 1753. [20 July 2012]. In: Lista invazivnih vrsta na području AP Vojvodine = List of invasive species in AP Vojvodina [Internet]. Version 0.1beta. Anačkov G, Bjelić-Čabrilo O, Karaman I, Karaman M, Radenković S, Radulović S, Vukov D & Boža P, editors. Novi Sad (Serbia): Department of Biology and Ecology; 2011. [Available:

http://iasv.dbe.pmf.uns.ac.rs/index.php?strana=baza&idtakson=40&jezik=english]. Boža, P., Igić, R., Anačkov, G., Vukov, D., (2006): Complex Research of Invasive species

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York. Wittenberg, R., Cock, M.J.W. (2001): Invasive Alien Species: A tool of Best Prevention and

Menagement Practices. CABI publishing, Oxford.

MORPHOLOGICAL VARIABILITY OF INVASIVE SPECIES

AMBROSIA ARTEMISIIFOLIA L. (ASTERALES, ASTERACEAE) ON THE

IMPORTANT TRANSIT AREASGoran Anačkov, Slobodan Bojčić, Vladimir Ječmenica, Milica Rat, Ružica Igić, Pal Boža

University of Novi Sad, Faculty of Science, Department of Biology and Ecology, Trg D. Obradovica 2, Novi Sad, Serbia

Herbarium BUNS; Laboratory of invasive and alergenic plants;

Project 173030 Ministery of sciences and education of Republic of Serbia

Corresponding e-mail: [email protected]

Positions of analyzed individuals in the area of the

discriminant axes (blue: sand; red: construction

site; green: clay-sand)

clay-sandsand

const. side

Correlation between characters ‘node with first fertile branches

(FG)’ before (green) and after (red) mechanical treatment

Conducted investigations have shown that at some, especially the

poorer soil types, A. artemisiifolia shows an extraordinary capability

of adaptation in terms of survival and biomass production.

Characteristics of the soil notably influence the variability of leaf

area and much less on stem height.

Increased variability after treatment is the result of the plants

individuality in order to solve the problem of propagulume

production. The position of nodes, where the first fertile branch is

developed after mechanical treatment is also characteristic that

allows a high degree of individual plants variability.

MORPHOLOGICAL VARIABILITY OF INVASIVE SPECIES …

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