Linköping University | Department of Physics, Chemistry and Biology Type of thesis, 60 hp | Educational Program: Applied Ethology and Animal Biology Spring term 2016 | LITH-IFM-A-EX— 16/3228--SE
Habitat Preferences of the
Woodland Brown (Lopinga-
achine) in South-East Sweden
Author: Zahra Moradinour
Examinator: Tom Lindström Tutor: Karl-Olof Bergman
Avdelning, institution Division, Department
Department of Physics, Chemistry and Biology Linköping University
URL för elektronisk version
ISBN
ISRN: LITH-IFM-A-EX--16/3228--SE
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Serietitel och serienummer ISSN
Title of series, numbering ______________________________
Språk Language Svenska/Swedish Engelska/English ________________ Rapporttyp Report category Licentiatavhandling Examensarbete C-uppsats D-uppsats Övrig rapport _____________ Titel Title
Habitat Preferences of the Woodland Brown (Lopinga achine) in South-East Sweden Författare Author Zahra Moradinour Nyckelord Keyword
L. achine, butterfly, woodland, habitat factors, movement behavoiour
Sammanfattning
Abstract
As a result of changes in grass sward composition and vegetation structure, as well as overgrowth of trees and bushes in open areas, many woodland butterfly species have declined across Europe.
Lopinga achine is a flagship species of woodlands and it has gone extinct from several habitats in
Europe. The aim of this study was to determine the effect of habitat factors on the occurrence of L.
achine and investigate if alteration in such habitat factors effect on their movement pattern. The
experiments were conducted in the south east of Sweden. The occurrence of the butterflies and sampling habitat factors were recorded in transect method in 11 sites in the province of
Östergötland. Furthermore, movement pattern and flight speed of 28 individuals were tested in two sites with different habitat structures. Habitat variables including host plant (Carex montana) abundance, grass sward height, tree canopy cover and also fern abundance had a significant effect on the occurrence of the species. In addition, open area with short grass height and less canopy cover affected the movement pattern and speed of L. achine and individuals flew more straight and faster in open areas. In conclusion, results shown that habitat factors are important for the
occurrence of L. achine and population viability. In addition, alteration in habitat structure such as short grass sward height and lack of bush and canopy trees effect on butterflies’ movement
behaviour, which may lead to population decline or extinction of the species from local habitats. Datum
Date 2016-06-16
Content
1 Abstract ... 1
2 Introduction ... 1
3 Material & methods ... 3
3.1 Study species ... 3 3.2 Study area ... 3 3.3 Field method... 4 3.3.1 Species monitoring ... 4 3.3.2 Movement behaviour ... 6 3.4 Data analysis ... 7 4 Results ... 7
4.1 Effect of habitat structure on occurrence of L. achine ... 7
4.2 Effect of habitat structures on movement behaviour ... 10
4.2.1 Flight pattern ... 10
4.2.2 Flight speed ... 11
4.2.3 Flight trajectories to different habitat structures ... 11
5 Discussion ... 12
5.1 Habitat preferences for L. achine ... 13
5.2 Movement behaviour ... 15
5.3 Conclusions and implication of conservation ... 16
6 Acknowledgement ... 17
1 1 Abstract
As a result of changes in grass sward composition and vegetation
structure, as well as overgrowth of trees and bushes in open areas, many woodland butterfly species have declined across Europe. Lopinga achine is a flagship species of woodlands and it has gone extinct from several habitats in Europe. The aim of this study was to determine the effect of habitat factors on the occurrence of L. achine and investigate if alteration in such habitat factors effect on their movement pattern. The experiments were conducted in the south east of Sweden. The occurrence of the
butterflies and sampling habitat factors were recorded in transect method in 11 sites in the province of Östergötland. Furthermore, movement pattern and flight speed of 28 individuals were tested in two sites with different habitat structure. Habitat variables including host plant (Carex
montana) abundance, grass sward height, tree canopy cover and also fern
abundance had a significant effect on the occurrence of the species. In addition, open area with short grass height and less canopy cover affected the movement pattern and speed of L. achine and individuals flew more straight and faster in open areas. In conclusion, results shown that habitat factors are important for the occurrence of L. achine and population viability. In addition, alteration in habitat structure such as short grass sward height and lack of bush and canopy trees effect on butterflies’ movement behaviour, which may lead to population decline or extinction of the species from local habitats.
2 Introduction
As a result of changes in forestry practice and grazing pressure, woodlands have been notably altered during the past 150 years (Vera 2000; Streitberger et al. 2012). These major alterations resulted in destruction and fragmentation of suitable habitats for many butterfly species (Bergman & Landin 2001). Due to the reduction of habitat suitability, such as changes in grass sward composition and vegetation structure, as well as overgrowth of trees and bushes in open areas, populations of many woodland butterflies have declined across Europe (Van Swaay et al. 2006; European Red list of Butterfly 2010;
Kodandaramaiah et al. 2012).
The Woodland Brown (Lopinga achine, Scopoli; Nymphalidae) is a representative of these butterflies and is a flagship species for woodlands (Streitberger et al. 2012). It is known as a Palearctic butterfly, with a wide distribution from Japan and Korea over North and Central Asia to southern Fennoscandia, Central Europe and the northern part of Spain (Tolman and Lewington 1997; Tuzov 2000; Kodandaramaiah et al.
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2012).Despite the broad distribution of L. achine, the species is very localised and distributed in its range with long distances between
populations, and it has disappeared from many parts of these areas (Heath 1981; Van Helsdingen et al. 1996; Bergman 1999; van Swaay & Warren 1999; Kudrna 2002; Kodandaramaiah et al. 2012). During the last
decades, more than 30% population decline, has been reported for this species in Europe. As a consequence, L. achine is classified as
Vulnerable in the IUCN redlist 2015, and placed as Near Threatened in the Swedish Red Data Book 2015 (Bergman 2001; ArtDatabanken 2015). In Sweden, the population is distributed in two regions: the province of Östergötland in the southeast and the island of Gotland in the Baltic (Henriksen & Kreutzer 1982; Bergman 1999). The species is sensitive to the successional stage of the habitat and has specific habitat requirements, particularly during oviposition and the larval stage. Therefore, the species prefers narrow zones under tree canopy and bushes, especially along the edges of glades with the presence of the host plant (Carex montana) (Bergman 2001). During the 1960s and 1970s, five populations of the species disappeared in the province of Östergötland, which was attributed to the reduction of glades, grazing pressure and overgrowing (Bergman 2001; Kodandaramaiah et al. 2012).
In addition to the importance of studying habitat structures for L. achine, increasing the knowledge about the behavioural movement patterns in response to changes in its environment is necessary, considering the lack of these data. This necessity is due to the strong effect of habitat structure on butterflies’ movement(Rouquette & Thompson 2007), while
movement is vital for finding a mate, food foraging and egg laying (Leimar et al. 2003)
The aim of this study is to determine the influence of different habitat characteristics (host plant, grass sward height, tree canopy and bushes and fern abundance) on the occurrence of L. achine in its habitats and to study the behavioural movement pattern in order to find if movement pattern changes with alteration in these habitat characteristics in different environments.
3 3 Material & methods
Two experiments were conducted in order to determine the influence of different habitat characteristics on the occurrence of L. achine and its movement pattern in response to change in habitat factors.
In the first study, the occurrence of the butterflies and measurement of habitat factors in each butterflies’ spot were recorded in 11 sites in south east of Sweden. Furthermore, control measurements of the habitat factors were performed in selected points for the whole area of each sites in order to have a general view of the habitat structures.
Secondly, movement pattern was tested in two sites with different
structures, a deciduous forest that mostly was covered by tall grass sward height and close canopy cover, and an open oak area with short grass sward height and open canopy cover. Flight pattern and flight speed were recorded for each released individuals respectively.
3.1 Study species
Lopinga achine flies in one generation in Jun-July and hibernation occurs
in the larval stage. The main host plant for the species in the studied area in Östergötland is the sedge Carex montana L (Bergman & Landin 2001). According to inventories up to 2015, L. achine lives in 82 populations in an area of 25*60 km2 in Östergötland and most of the populations have connections to each other. Populations are mostly small, and only two of them contain more than 500 adults (Bergman 2015).
3.2 Study area
The study area is located about 30 km south of Linköping in the province of Östergötland, in the south east of Sweden (58–20′ N, 15–45′ E)
(Bergman & Landin 2002). The type of habitat in this area is partly open oak woodland (Quercus robur L.) (Fagaceae) with scattered hazel bushes (Corylus avellana L.) (Corylaceae), which is primarily surrounded by open fields or spruce plantations (Bergman 1996, 2001). Due to the succession in this type of habitat, it will be closed if it left unmanaged after 50 years (Bergman & Landin 2001).
The distribution of suitable habitats for L. achine was mapped by the Östergötland county administrative board. Out of the 271 sites mapped, 11 were chosen for this study, based on different habitat characteristics (host plant, vegetation height and canopy cover) for field work (Fig. 1).
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The sites were mostly covered by deciduous forests surrounded by spruce plantations and also semi-natural grasslands.
Figure 1. The study sites in the province of Östergötland, southern Sweden (study sites are shown in red colour). © "Lantmäteriet [License No.
I2014/00578]"
3.3 Field method
3.3.1 Species monitoring
The observations of adult butterflies started on July 2, 2015. Observations were conducted between 09:00 and 17:00 (Swedish summer time,
GMT+2), suggested by Wikström et al. (2009), since the butterfly activity may be reduced before and after these time periods due to unfavorable temperatures and light conditions (Rawlins 1980; Shreeve 1984; Meyer & Sisk 2001). The weather criteria for sampling were around 25-30°C
(required to increase the body temperature for flight), wind less than 6 Beaufort while the weather was sunny (using for thermoregulation) (Wikström et al. 2009).
Sampling was performed through transect walks along fixed routes within
20 m distance from each other. The transect walk was conducted in a steady pace, and habitat variables (Table 1) were sampled in circular plots (10m Ø) in the locations where the butterflies were found.
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observer from the central point of the plot. The coordinates of each individual were taken by GPS Garmin 60CSx.
Table 1. Habitat variables and measurement methods
Variables Definition
Amount of host plant (dm²)
Amount of host plant (Carex montana) in a circular plot (10m Ø). It was measured by a transparent sheet divided into square decimetre.
Amount of leaves less than 3m (%)
The area covered by hazel or other types of bushes less than 3 m in the plot
Amount of fern (dm²) The area covered by fern in the plot Amount of bare ground
(dm²)
The area of the plot which was not covered by plants or rocks
Amount of rock (dm²) Grass sward height (cm)
The area covered by rock in the plot
Estimate of the height of vegetation in the plot. It was measured by a sward stick divided into 100 cm with a low weight drop-disk standing on top of the grass
Soil moisture Types of soil based on humidity: dry-mesic, moist and mix (i.e. when the plot covered by two types of soil moisture: moist and dry-mesic). Soil moisture was estimated by the vegetation composition in the plot
Canopy openness (0-1) The area of the plot which was not covered by canopy trees. It was measured by taking a hemispherical photo in the central point of the plot upward through the tree canopy from an east-west trajectory. The photos were taken by camera (Nikon D300) with fisheye lens (Sigma fisheye 8mm, 3.5, equisolid)
*All photos from canopy openness were adjusted by the Image J program and analysed in CIMES-FISHEYE software. The pictures were classified to 0-1(i.e. 0= indication of closed canopy, 1= indication of openness)
After the flight’s period finished, measurement of habitat variables used as controls for the whole area of each sites. All habitat variables were sampled with the same methods as in Table 1. Based on the area of the sites, control points were surveyed at two different densities(30 m distance between each plot in large sites > 4 ha, and 20 m distance in small sites < 4 ha).
6 3.3.2 Movement behaviour
Movement behaviour was examined in order to survey how butterflies respond to change in habitat structures (i.e. grass sward height and canopy closure). The effect of these parameters on the flight pattern and flight speed of L. achine was tested.
Individuals were captured with a butterfly net in the site where the
population of L. achine had the highest density. The site was a deciduous woodland with tall grass sward height and mostly closed canopy cover. Captured butterflies were kept in plastic jars, which contained C.
montana and were moisturized with a wet wipe to provide a suitable
condition for the butterflies. The jars were retained in a cool box and translocated to the release site (Merckx & Van Dyck 2007). The first release site was an open semi-natural grassland with oak and hazel used for grazing with a close proximity (260 m) to the capture site. The second release site was the one where butterflies were captured.
The experiment was conducted in mid-July when the temperature was approximately 21°C and the weather was sunny. In order to prevent the effects of wind (i.e. speed and direction) on butterflies’ movement, individuals were released when the wind level was < BF1 (1-5km/h) (Merckx & Van Dyck 2007).
Before release, every individual was transferred to a transparent box and kept there about 2 min to acclimatize to the environment. After two minutes, the lid was opened with a 10 m string to prevent intervention with the butterfly’s behaviour (Merckx & Van Dyck 2007). The
behaviour was recorded immediately after the butterflies left the box and were tracked by two observers, one using a stopwatch to record the time and another placing flags at each turn of flight direction at the same time (Merckx & Van Dyck 2007). Each butterfly was tested only one time and the recording process was stopped either after five minutes or when the butterfly disappeared from our sight (e.g. when it flew to the top of the trees or disappeared among bushes). The distance and the direction
between each of the flags were measured by a meter tape, and the amount of environmental parameters was sampled according to the table 1.
7 3.4 Data analysis
To analyse the effect of habitat factors on the occurrence of L. achine, a generalized linear model was performed using binominal distribution in IBM SPSS Statistics 23. Habitat factors were used as explanatory
variables and soil moisture as a categorical factor.
For the second part of the study, two different factors (flight pattern and flight speed) were evaluated to examine the influence of habitat structure on butterflies’ movement patterns. In order to calculate the flight speed, time and distance at each stop point were measured for every individual. Thereafter, the general linear mixed model was performed to identify the effect of canopy openness and grass sward height on flight speed. In this case, speed was considered a dependent variable, whereas sex, canopy openness and grass sward height were fixed effects. Furthermore, individual identity was set as random effect in the model.
To analyse how habitat structure affect flight pattern behaviour, a multinomial regression model was used. Movement behaviour was classified into three categories: straight flight (when an individual flew straight without any turns), sitting (mainly resting and/or basking) and flight with several curves (when butterflies made several turns during the flight) (Merckx & Van Dyck 2007). In this model, flight with several curves was used as the reference category. Grass sward height and
canopy openness were explanatory variables, while flight pattern was an independent factor.
Furthermore, in order to find out which direction and types of habitat structure butterflies flew more in release sites, a one sample Chi-Square Test was run. Different directions were classified as 1= North, 2= East, 3= South and 4= West and types of habitat structure was determined in each direction.
4 Results
4.1 Effect of habitat structure on occurrence of L. achine
Habitat factors were recorded for a total of 187 butterfly occurrences and 470 selected control points from 11 sites in Östergötland. The amount of host plant and grass sward height had largest effect among environmental variables on the occurrence of L. achine (Table 2, Fig. 2).
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Table 2. Effect of different habitat variables on the occurrence of L. achine, using a generalized linear model.
Parameter Estimate Std. Error
Wald
Chi-Square P
(Intercept) -1.342 0.4762 7.944 0.005 Soil Moisture, dry
mesic 0.215 0.3235 0.440 0.507
Soil Moisture, mix -0.157 0.4021 0.153 0.696 Amount of hostplant
(dm²) 0.001 0.0003 23.203 0.000
Canopy-openness -1.822 0.7881 5.346 0.021 Amount of leaves<3 -0.003 0.0039 0.731 0.393 Amount of fern (dm²) 0.001 0.0003 11.901 0.001 Amount of rock (dm²) 5.871E-5 0.0001 0.256 0.613 Bare-ground (dm²) 3.706E-5 4.7814E-5 0.601 0.438 Mean grass sward
height 0.041 0.0116 12.532 0.000
*The effect of moist soil was under the intercept
Furthermore, the occurrence of the butterflies increased with increasing grass sward height and amount of fern (Table 2, Fig. 2). In contrast, occurrence of the butterflies increased with decreasing canopy openness (Table 2). The highest proportion (28%) of the occurrence in study sites was recorded in the areas with 0.15-0.2 openness which indicates that L.
achine showed a tendency to use areas with more canopy closure rather
than in open areas. But the occurrence also declined in dense areas between 0 to 0.1 openness classes (Fig. 3). No effect were found for soil moisture, amount of leaves less than 3m, rock and bare ground (Table 2).
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Figure 2. Mean grass sward height, amount of host plant and amount of fern for sampling points with presence and absence of L. achine
Figure 3. The proportion of observed Lopinga achine individuals (light grey bars) in different canopy cover classes in comparison to canopy cover in selected control points (dark grey bars).Openness classes goes from 0= totally closed canopy to 1= totally open canopy
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4.2 Effect of habitat structures on movement behaviour
In this experiment 28 individuals, 11 males and 17 females, were caught from the site with the highest density of L. achine. The effect of canopy cover and grass sward height on the butterflies’ movement pattern and flight speed were tested.
4.2.1 Flight pattern
The flight pattern was classified into three categories i.e. straight flight, several curves and sitting, and several curves was considered as the reference category in the model (Table 3). There was a negative
significant effect (B= -0.157, P= 0.011) of grass sward height on flight pattern, showing that butterflies were more likely to fly straight than fly with several curves in short grass sward height (Table 3, Fig. 4). The effect of canopy openness on straight flight was significantly positive (B= 7.140, P= 0.002), showing that the probability of flying straight increased with decreasing canopy cover (Table 3, Fig. 4).
With regard to sitting behaviour, butterflies were more likely to perch in areas with tall grass sward height (Fig. 4), though the effect was not significant (P= 0.086) (Table 3). With increasing canopy openness butterflies had a higher tendency to perch rather than flying with several curves (Fig. 4), but the effect was not significant (Table 3).
Table 3. Effect of canopy cover and grass sward height on flight pattern. The reference category is: fly with several curves
Flight pattern Parameter Estimate Std. Error
Wald Chi-Square P Straight Intercept -1.109 0.708 2.452 0.117 Grass sward height (cm) -0.157 0.061 6.536 0.011 Canopy-openness 7.140 2.323 9.444 0.002 Sitting Intercept -2.018 0.724 7.780 0.005 Grass sward height 0.084 0.049 2.943 0.086 Canopy-openness 1.759 2.948 0.356 0.551
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Figure 4. Mean height of grass cover and canopy openness level for three categories of flight pattern
4.2.2 Flight speed
Flight speed increased significantly (B= 2.060, P= 0.005) with increasing canopy openness (Table 4). The effect of grass sward height on flight speed was significantly negative (B= -0.040, P= 0.019), showing that butterflies tended to fly faster in areas with short grass sward height. No significant difference was found between males and females.
Table 4. Effect of canopy cover and grass sward height on flight speed.
Parameter Estimate Std. Error P
(Intercept) 0.515894 0.287479 1.000 Sex, female 0.191888 0.229167 0.419 Canopy-openness 2.060901 0.710732 0.005 Grass sward
height(cm) -0.040785 0.016542 0.019 *The effect of male was under intercept
4.2.3 Flight trajectories to different habitat structures
Butterfly’s trajectories from the release point to areas with different grass sward height and canopy closure were studied. The choice of flight
directions was significantly different from random flight directions (P= 0.000). In the open release site out of 23 butterflies, 15 individuals flew in the area that was covered by oak trees and hazel bushes with the mean grass sward height 6 cm (Table 5, Fig. 5). The lowest flight trajectory (1individual) was recorded for the open area which covered with scattered hazel bushes (Table 5, Fig. 5)
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Table 5. Butterflies trajectories to different habitat structures. Observed N= number of observed butterflies in each directions. Expected N= number of expected butterflies’ trajectory
Direction Observed N Expected N Residual
North 5 5.8 -0.8 East 15 5.8 9.3 South 2 5.8 -3.8 West 1 5.8 -4.8 Total 23
Figure 5. Flight trajectories of L. achine individuals in the area with short grass sward height and open canopy cover. North: combination of oak trees and hazel bushes, mean grass sward height: 10-cm. East: combination of oak trees and hazel bushes, mean grass sward height: 6-cm. South: open area with short hazel bushes, mean grass sward height: 9-cm. West: Combination of tall and short hazel bushes, mean grass sward height: 9-cm
5 Discussion
In this study, the effect of habitat structures on the occurrence of L.
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the significant effect of habitat parameters, i.e. host plant, grass sward height, tree and bush canopy cover and fern abundance on the occurrence of L. achine in 11 sites in Östergötland. The results from the second experiment showed the significant effect of change in vegetation height and canopy cover on their movement behaviour i.e. flight speed and flight pattern.
5.1 Habitat preferences for L. achine
The results from analyzing the importance of different habitat variables on the occurrence of L. achine revealed a considerable effect of host plant and other variables, i.e. grass sward height, canopy openness and
abundance of fern.
In this study, the presence of the host plant (C. montana), was strongly correlated with the occurrence of L. achine and a higher occurrence was recorded in the areas with a higher amount of the host plant (Fig. 2, Table 2). This result is in agreement with Bergman (2000), which showed that 83-85% of the L. achine larvae used C. montana in the field, and there was a lower rate of larval mortality on C. montana compared to other plant species. The importance of a higher amount of host plant has also been shown by Devries (1987) and Beccaloni (1997), emphasizing that butterflies’ distributions are likely dependent on a high density and abundance of host plants (Saikia et al. 2009). In addition, high cover of host plant for egg-dropping butterflies like L. achine has been found crucial for oviposition, larval feeding and minimizing time-consuming searching behaviour (Wiklund, 1984; Streitberger et al. 2012).
However, Lindman et al. (2013) and Bergman (1999), suggest that other habitat factors may also important beside host plant abundance, such as bush and tree canopy cover and grass sward height.
This is confirmed in this study where grass sward height also had a significant effect on the butterflies’ occurrence (Table 2) and the
occurrence of L. achine increased with increasing vegetation height (Fig. 2). The necessity of grass sward height for L. achine and other species of butterflies has been revealed in different studies. For example, a study on the decline of the Woodland Brown in central Europe showed that the abundance of L. achine had a positive correlation with vegetation height (Streitberger et al. 2012). This is probably due to L. achine eggs’
sensitivity to desiccation, which has been tested by Bergman (1999) and Wiklund (1985), under laboratory conditions. They found that the egg mortality of L. achine increased considerably when the relative humidity
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was less than 80%. In other words, longer swards provide a cooler and more humid microclimate near the soil surface, which is crucial for the embryonic development of L. achine eggs (Stoutjesdijk & Barkman 1992; Streitberger et al. 2012). Furthermore, taller vegetation may decrease the effect of wind power and provide a shelter for butterflies. The study on the silver-studded blue butterfly in the UK (Plebejus argus) found that butterflies were considerably more abundant in taller
vegetation. Tall vegetation acts as a shelter with providing a good condition for mating and egg laying and also decreasing predation risk (Mendel and Parson 1987; Shreeve 1992; Porter 1992; Dover et al. 1997; Dennis 2004). Other than L. achine, the species richness and abundance of other species of butterflies (e.g. Rhopalocera), bumble bees,
grasshoppers and wasps increased with increasing vegetation height (Öckinger et al. 2006; Öckinger & Smith 2007).
Canopy openness had a negative significant effect on the occurrence of butterflies. However, the occurrence of butterflies peaked in areas with 15- 20% openness (Fig. 3), while it decreased in open areas (where the sky is completely visible) and also closed areas (where no sun exposure can penetrate from foliage cover). Lopinga achine avoidance of open areas with less canopy cover may be due to the fact that open areas with a high level of sun exposure decrease humidity and gives a dry
microclimate which threatens the survival of L. achine eggs. A field study showed 48% egg mortality due to desiccation in sun-exposed areas
(Bergman, 1999). On the other hand, warm microclimate and high
amount of sunlight has been shown to be important for egg development in many butterflies. For example, Montane Butterfly (Euphydryas
giilettii) eggs had a significantly faster developmental rate in the areas
with less leaves cover (Williams 1981) and warmer condition. Similarly, cankerworm (Alsophila pornetaria) eggs were hatched faster in southern directions with higher amount of sun exposure compared to those eggs that were laid in north trajectories with less amount of sunlight
(Schneider 1978; Mitter et al. 1979; Williams 1981). Overall, different butterflies’ taxa require various levels of canopy cover. For instance, a study of nymphalid butterflies in India showed that the endemic or habitat specialists mostly preferred low or moderate sunlight compared to
generalist butterflies (Saikia et al. 2009).
Results showed a positive effect of fern abundance on the occurrence of
L. achine (Table 2), and the frequency of butterflies increased with
increasing amount of fern (Fig. 2). According to the field experiment we found a high amount of host plant abundance in the shade of ferns,
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indicating that they may provide a suitable condition for growing the host plant. In addition, L. achine may use the areas and hostplant under the shades of fern for dropping eggs. In general, the community of fern and shrubs can provide a shelter for butterflies in adverse weather conditions, which allows butterflies to stay longer in the area for different activities, such as food foraging, mating and oviposition (Dover 1997; Merckx and van Dyck 2002; Skorka et al. 2007).
5.2 Movement behaviour
The study of animal movement patterns is crucial because it increases the knowledge about different behaviours, such as foraging behaviour, space usage in home ranges (Siniff & Jessen 1969; Swihart et al. 1988; Loehle 1990; Crist et al. 1992) and community interactions (Murdie & Assell 1973; Banks et al.1987; Kareiva & Odell 1987; Crist et al. 1992). Animals move in response to changes in vegetation structure and plant composition for food foraging and thermoregulation in different habitats (Crist et al. 1992). Alteration in habitat may change dispersal and
mobility patterns of species, depending on the rate of degradation in a habitat (Thomas 2000; Merckx et al. 2003; Van Dyck & Matthysen 1999).
In this study the effect of the habitat structure on the L. achine movement pattern was evaluated. According to the result, both speed and movement pattern changed in L. achine in areas with short grass sward height and less canopy closure. This result is in consistent with the other results in current study showing that L. achine had a lower occurrence in areas with short grass sward height and less canopy cover. It means that L. achine has a lower tendency to fly in an unsuitable habitat compared to a suitable habitat. Such homing behaviour has also been shown for other species like Meadow Brown (Maniola jurtina) and gatekeeper (Pyronia tithonus) when they preferentially chose to return to their familiar patch instead of returning to unfamiliar one (Conradt, 2000). Likewise, M. jurtina is known to move from habitats that have recently been grazed or cut, which is also confirmed by a study of Lebeau et al. (2015), since this species disappeared from habitat that was mown.
Butterflies may show different behaviour and flight morphologies in different habitats (e.g. dense forests versus more open areas) (Hill et al. 2001). This notion is supported by the current study, since a significant effect of different habitat structures was found on the flight pattern of L.
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to in their preferred habitat. In addition, flight speed was faster when L.
achine individuals flew over open habitat. Several studies on different
species of butterflies show similar results. For instance, studies on M.
jurtina detected a more direct and linear pattern with faster flights when
they flew across an unsuitable habitat which differed from their routine explorative movement (i.e. slower with more tortuosity) in a suitable habitat (Conradt et al. 2000; Van Dyck and Baguette 2005; Conradt & Ropper 2006; Cormont et al. 2011). Lebeau et al. (2015), found that M.
jurtina had shorter and faster flight bouts after the meadows had been
mowed. Furthermore, studies on fruit-feeding Nymphalid butterflies in rainforest gaps in Malaysia suggest that differences in vegetation structure may affect flight patterns so that butterflies show a more manoeuvrable pattern in dense vegetation and faster flight in more open areas (Hill et al. 2001)
These behavioral changes in butterflies may be taken to indicate that butterflies increase their flight speed in order to decrease the risk of predation, especially in open areas. Monarch butterflies in open areas showed more sensitivity to birds’ predation than those in closed forests (Alonso-Mejia et al. 1998). But Heidinger et al. (2009), suggest that butterflies in an unknown environment may show atypical behaviour and faster movement. This behaviour is probably due to orientation problems, which may lead to an increase in predation risk (Metzgar 1967; Ambrose 1972; Jacquot & Solomon 1997; Yoder et al. 2004).
Direct flight with faster movement in new areas might also be the result of butterflies’ attempt to reach a suitable habitat from an unsuitable patch. One study on 23 butterfly species in South Africa revealed that butterflies flew faster and farther in disturbed grassland, probably due to their
seeking for a more preferred habitat (Pryke & Samways 2001).
5.3 Conclusions and implication of conservation
Lopinga achine is a woodland butterfly species, and can be considered a
good indicator of habitat change and degradation. In this study, the effect of changes in habitat structure on L. achine occurrence and its movement has been shown. Butterflies had a more occurrence in the presence of host plant, and their abundance increased with a higher amount of host plant. This leads to the conclusion that the host plant is important for
occurrence of L. achine, particularly as the higher amount of host plant might be crucial for egg laying. Taller vegetation was also positively
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significant but the suitable height should be considered in conservation programs in order to prevent the negative effect of highly dense
vegetation which could affect host plant presence and microclimate
condition. On the other hand, short or heavily grazed vegetation may lead to the migration of butterflies from these habitats, and habitat
management should be focused on high grazing pressure and/or mowing in L. achine sites. Canopy openness was also an important factor for the occurrence of butterflies, and both open and closed canopy resulted in less occurrence of L. achine. Since tree and bush canopy influence the amount of sun exposure to the forest area, it is crucial to control the
amount and density of this factor to prevent desiccation or closed canopy.
L. achine also changed behavioral movement pattern and flew faster in an
open area with short grass height and less canopy trees. Since movement is vital for butterflies’ activities, major change in habitat can be
threatened the survival of L. achine. To prevent the negative effect of open area on L. achine activities, grazing the sites can be deferred after flight period and heavily grazed areas should be maintained ungrazed for a period of time to reach to the suitable level for L. achine. Also, too much clearing should be avoided to preserve suitable amount of canopy cover in these areas. However, more studies are needed in order to provide suitable information about the effect of habitat structure on the movement behaviour for L. achine and other species of butterflies. Also, in order to provide safer results and evaluate the effect of sex ratio, a larger sample size than that of this study is required.
In conclusion, the results in this study show that habitat factors have a crucial role in occurrence and population viability of L. achine. The
species is sensitive to changes in habitat structure and reduction of habitat suitability especially during oviposition and larval stage and that may lead to population declines or extinction of the species from local habitats.
6 Acknowledgement
I would like to specially thank my supervisor Karl-Olof Bergman that supported me in the field work and the whole parts of the project. Also thanks to Lars Westerberg and Per Milberg for support in statistical analysis and helpful suggestions as well as Zeinab Moradinour and Davoud Saffar for support in programming and Ali Moradinour for graphical design. I should also thanks to Tom Lindström and Elin Käck for their helpful suggestions to improve my report and Länsstyrelsen
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Östergötland for giving the maps of the study sites. At the end I give my best regards and appreciations to Swedish institute for supporting me to study in Master’s program in Sweden and my family and friends.
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