Altitudinal distribution of moths ( Lepidoptera ) in Mt . Jirisan National Park , South Korea

The relationship between species richness of plants and animals and altitude can be either hump-shaped, a monotonic decrease or increase. In this study the altitudinal distribution of moths on one of the highest mountains in South Korea was investigated. Moths were captured using a UV-light trap from May to October in 2007 and 2008. This revealed that the relationship between the total numbers of moth species and individuals and altitude is hump-shaped. A significant relationship was also recorded between the size of the area at each altitude and moth abundance and richness. However, the evenness index yielded a consistent decrease with increase in altitude because of the dominance of few species at high altitudes. Non-metric multidimensional scaling identified two major axes for the moth assemblage on Mount Jirisan. The correlations between the axes and variables demonstrated that the first axis was strongly correlated with altitude and aspect and the second axis with forest and site location.


INTRODUCTION
Mountains are found on all continents.High altitude ecosystems on mountains differ from all other ecosystems as the environment at high altitudes is uniquely harsh (Mani, 1990).Mountain habitats are spatially and structurally complex when trees or larger shrubs form part of the landscape, producing a mosaic of different habitat types with their own particular vegetation and/or microclimate (Haslett, 1997;Hodkinson, 2005).Utilization of these mosaic patches by different plants and animals may reflect more their specific life history strategies and ability to exploit a particular type of habitat than the total taxonomic diversity present at a particular altitude (Haslett, 1997;Hodkinson, 2005).
Patterns in the altitudinal distribution of species richness have frequently been cited as compelling evidence for hypotheses that propose associations with productivity and ambient energy, as well as past and current climates, since these factors vary with altitude (Rahbek, 2005).Two patterns in the altitudinal distribution of species richness are frequently observed (Rahbek, 2005).The first is a monotonic decrease with altitude.This is expected if resource limitation and thermal constraints govern species diversity (Fiedler & Beck, 2008).The second is that the pattern of species richness is hump-shaped, the middomain effect (Colwell & Lees, 2000).This pattern is expected if the geometric constraints on habitat areas change with altitude.Lomolino (2001) indicates that peaks in diversity at intermediate levels along an incline correspond to points where the combined effects of many environmental factors and associated processes promote the co-occurrence of many species.Additionally, several insect groups demonstrate no clear altitudinal trends.For example, grasshoppers on a Mediterranean mountain (Claridge & Singrao, 1978) and hemipteran insects in Indonesian tropical rainforests (Casson & Hodkinson, 1991) exhibit no clear altitudinal trends (Hodkinson, 2005).Therefore, it appears that the changes in species richness with altitude may be determined by more complicated mechanisms than previously believed.
Mount Jirisan National Park (highest peak: 1915 m, area: 440.517 km 2 ) includes the highest mountain on the mainland of South Korea.The annual average temperature is 12-13°C and annual precipitation is 1,200 mm, mostly falling in summer.The vegetation is divided into three main zones: subalpine (> 1,400 m), cool temperate (400-1,400 m) and warm temperate (200-300 m on southern aspects) (Yim, 1977).The subalpine zone is characterized by coniferous (Abies koreana Wilson, Abies nephrolepisv Maximowicz, Picea jezoensis (Sieb.& Zucc.)Carriere, Pinus koraiensis Sieb.& Zucc., Taxas cuspidate Sieb.& Zucc.) and deciduous (Betula ermani Chamisso, B. costata Trautvetter, Quercus mongolica Fischer, Rhododendron schlippenbachii Maxim.var.schlippenbachii) trees.Below the subalpine zone, the forest consists mainly of deciduous trees, such as Quercus mongolica, Quercus serrata Thunberg, Carpinus laxiflora (Sieb.& Zucc.)Blume, C. tschonoskii Maxim., Quercus aliena Blume and Quercus variabilis Blume.Trees such as Pinus densiflora Sieb.& Zucc., Cornus controversa Hemsley, Zelkova serrata (Thunberg) Makino and Fraxinux mandshurica Ruprecht commonly occur on ridges and in valleys at low altitudes.The mountain range runs 34 km east to west and 26 km north to south in the southwestern part of Korea and is a barrier to dispersal for many species.Its geographic location and difference in altitude from the majority of the mainland have facilitated many studies on the altitudinal distribution of species richness.
Studies on the patterns in the altitudinal distribution in species richness in Mount Jirisan National Park have revealed it mostly either decreases monotonically or is hump-shaped.Namkung et al. (1972) record a monotonic decrease in spider species richness with increasing altitude over the range of 600 to 1750 m. Lee et al. (2008) compared communities of breeding birds and found that bird species richness and density were higher at low than at high altitudes.However, the species richness of millipedes is highest at middle altitudes (700 m) (Lim et al., 1992) as is that of soil microarthropods and pseudoscorpions, which peak at 700 and 900 m, respectively (Hong et al., 1996(Hong et al., , 1997)).Similarly, the distribution with altitude of stone fly species richness (Plecoptera) is also humpshaped with a peak at 750 m (Ra et al., 1991).
This study sought to determine the altitudinal distribution of moths in Mount Jirisan National Park and the influence of altitude on moth species richness and abundance.

Study sites
Seven sites in the Mount Jirisan National Park in South Korea were sampled in this study (Fig. 1, Table 1).These sites were selected based on accessibility from the lowest CEH (295 m) to the highest altitude QMH (1372 m).Of the seven sites, three (CEH, AKH, QMH) were Korea Long-Term Ecological Research sites.Altitudinal area (ha) data for Mount Jirisan National Park was obtained from the Korea Forest Research Institute (Seoul, Korea).
Vegetation at the sites was categorized as either coniferdominant or deciduous-dominant.The vegetation at CEH consisted mainly of pine trees and at AKH mainly of Abies koreana.SSA, BS, HY, SW and QMH were covered with diver-sity of hardwood deciduous trees with little understory vegetation beneath a closed canopy.These seven sites were also designated as either riparian or upland, depending on their proximity to streams.BS, SSA, SW and AKH were designated riparian sites and CEH, HY and QMH upland sites.Two sites (CEH, SSA) were located on southern aspects and the remaining sites on northern aspects.
A light trap consisting of a 22-watt ultraviolet light powered by a 12 V battery (BioQuip Co., USA) was used to collect insects at each site.Moths were sampled once a month from May to October in 2007 and 2008.To avoid the effect of weather or moonlight on moth catches by each trap, the moths were sampled simultaneously at all seven sites.Moth sampling continued for six hours after dusk.Moths were identified to species and are preserved in a collection at Mokpo National University, South Korea.

Data analysis
The catches of moths for the two years were pooled.Species richness (total number of species), abundance (total number of individuals), Simpson's diversity index (D) and the Shannon evenness index (E) were calculated for each site (altitude).Simpson's diversity index calculates the probability of any two individuals drawn at random from an infinitely large community belonging to the same species (Magurran, 2003).The Shannon evenness index is H'/(ln S) where H' is the Shannon diversity index and (ln S) is the log-transformed species richness.Altitude, altitudinal area, species richness, and abundance were logtransformed prior to analysis.
Relationships among altitude, altitudinal area, species richness, abundance, diversity and moth evenness were investigated.First, correlation analyses between altitude, altitudinal area and four dependent variables (species richness, abundance, Simpson's D and the Shannon evenness index) were carried out to determine any significant relationships among the variables.Second, a piecewise regression was carried out with a breakpoint at 760 m (UCLA).The two models were combined into a single model by creating four new variables.The other two new variables, int1 and int2, represent the intercepts below and above 760 m, respectively.int1 = 1, if (altitude 760) int1 = 0 int2 = 1, if (altitude < 760) int2 = 0 All correlations and piecewise regression analyses were carried out using SPSS (SPSS Inc., 2006).
The relationship between moth assemblage and site location (distance from site to site) was examined using the Mantel test.The Mantel test was undertaken with an initial matrix of seven sites and 402 species (after deleting species unique to particular sites), and using a second matrix of distances (in km) between sites.Distance measures for the first and second matrices were Sørensen (Bray-Curtis) and Euclidean distances, respectively.A Monte Carlo randomization test with 999 runs was applied using PC-ORD (ver.5.17; McCune & Mefford, 2006).
Non-metric multidimensional scaling (NMDS), an ordination method, was used to compare differences in composition and abundance among samples (McCune & Grace, 2002).The NMDS procedure was initiated following data transformation, which included the deletion of singletons (species occurring only at one altitude) and log-transformations after adding one to the number caught of each species.A data matrix with seven sampling units and 402 species was produced.The second matrix was created based on four characters, altitude, forest type (conifer vs. mixed deciduous forest), site location (riparian vs. upland), and aspect (northern vs. southern).The significances of the clusters in the NMDS space were calculated using the multiresponse permutation procedure (MRPP), which tests the hypothesis of no difference between two a priori defined groups of entities, in PC-ORD (version 5.17; McCune & Mefford, 2006).

RESULTS
The species richness, abundance, diversity and evenness results are detailed in Table 2.The distribution of these variables relative to altitude has a hump-shaped pattern, with the exception of the evenness index (Figs 3-6).There were no significant correlations between species richness, abundance or diversity and altitude.However, the inverse correlation between altitude and evenness is significant (Pearson's r = -0.766,P = 0.045).
The piecewise regression between log-transformed species and individuals in the catches below and above 760 m (breakpoint) revealed that species richness is strongly affected by the variables studied above (alt2 t = -0.34,p < 0.05), while species abundance was strongly affected by the variables studied both below (alt1 t = 5.04, p < 0.05) and above the breakpoint (alt2 t = -7.53,p < 0.05) (Table 4).The relationship between the diversity index and the variables studied is not significant.Moth assemblages did not vary according to the distances between sites.The Mantel test revealed that the null hypothesis (no relationship between the site-to-site distance and moth assemblages) was not rejected (r = 0.16, P = 0.25).Non-metric multidimensional scaling identified two major axes for moth assemblage on Mount Jirisan (final stress = 0.006, Fig. 7).The correlations between the two axes and the four variables from the second matrix demonstrated that the first axis is strongly correlated with altitude (r = 0.95) and aspect (r = 0.71).The second axis, on the other hand, is negatively correlated with forest (r = -0.51)and site location (r = -0.47).The MRPP test did not reject the hypothesis of no relationship between groups for the variables forest (A = -0.01,P = 0.53), site location (A = -0.03,P = 0.89) and aspect (A = 0.01, P = 0.34).

DISCUSSION
Moth assemblages in Mount Jirisan National Park are primarily affected by altitude and altitudinal area.Moth assemblages at different altitudes are not strongly affected by the distance between sites (Mantel test r = 0.16, P = 0.25).In addition, NMS ordination revealed that the first axis is strongly correlated with altitude (r = 0.95) and aspect (r = 0.71).This suggests that factors related to altitude and aspect affect the species richness and abundances of moths in Mount Jirisan National Park.As altitude increases, many conditions such as temperature, precipitation, relative humidity, solar radiation, wind and soil conditions change (Körner, 2007;Fiedler & Beck, 2008).For example, temperature is altitude-specific and decreases by an average of 0.65°C for every 100 m of altitude.Other climatic factors (e.g., precipitation, humidity, wind speed, solar radiation) and geophysical characteristics are also collectively altered by altitude and aspect.Organisms respond to these integrative indicators of environmental change that depend on a multitude of physical and chemical factors along altitudinal gradients (Fiedler & Beck, 2008;Chen et al., 2009).
The distribution of species richness and abundance of moths relative to altitude in Mount Jirisan National Park is hump-shaped with the peak at 760 m (Figs 3-4).Species richness strongly decreased above 760 m and species 232    abundance increased up to 760 m and decreased above it.The pattern in the distribution of altitudinal area relative to altitude for Mount Jirisan is also hump-shaped.Regression analyses revealed that altitudinal area is closely related to abundance and species richness, suggesting a close species-area relationship (MacArthur & Wilson, 1967).
The hump-shaped pattern in the altitudinal distribution of moths is similar to that recorded for other taxa on Mount Jirisan, including millipedes (Lim et al., 1992), microarthropods (Hong et al., 1996), soil pseudoscorpions (Hong et al., 1997) and stoneflies (Ra et al., 1991), although their peaks vary from 700 to 900 m.Fiedler & Beck (2008) record peaks of from 1000 to 2000 m for many groups and commented on the range in the values.The difference in the peak values for Korean and other mountains is likely to be a result of differences in the heights of the mountains and their latitudinal position (e.g.tropic, temperate, arctic).Compared to several high mountains in tropical areas, which far exceed 2000 m a.s.l.(e.g., Papua New Guinea, Hebert, 1980; Andean mountains, Brehm & Fiedler, 2003;Mt. Kilimanjaro, Axmacher et al., 2004), Mount Jirisan National Park is relatively low, with a height of less than 2000 m and is located in a temperate zone (latitude 35°N).
Unlike the hump-shaped patterns for the relationships between species richness and abundance relative to altitude recorded in Mount Jirisan National Park, the relationship for evenness consistently decreased with altitude (Fig. 6).Shannon evenness is a measure of heterogeneity that considers the degree of evenness in species abundances in terms of the ratio of observed diversity to maximum diversity (Magurran, 2003).The consistent decrease in evenness recorded in the present study suggests that the observed diversity decreased relative to the maximum diversity.Insect communities at high altitudes are characterized by few species and a greater abundance of individuals (Mani, 1968;Hebert, 1980;Brehm & Fiedler, 2003).Due to the generally extreme conditions at high altitudes, a high degree of inter-specific integration with concomitant community independence and isolation is one of the peculiar characteristics of high altitude insect communities (Mani, 1968).For example, Brehm & Fiedler (2003) suggest that the relatively high diversity of larentiine moths (Geometridae) in the Andean mountains may result from low predation pressure at high altitudes.Six species of which more than 170 individuals were caught (about 20% of total catch of 8,706 individuals) included 970 Hydriollodes morosa (Butler, 1879) (Noctuidae), 589 Lemyra boghaika Tsistjakov & Kishida, 1994 (Arctiidae), 336 Odontopera arida (Butler, 1878), 320 Alcis angulifera (Butler, 1878), 190 Idaea biselata (Hufnagel, 1767) (Geometridae) and 173 Drymonia dodonides (Staudinger, 1887) (Notodontidae).Among these species, the three most abundant were found primarily at high altitudes (SW, AKH, QMH).
Comparative studies of altitudinal gradients are needed to identify the consistent patterns in scale effects, which can then be used to study the effects of contemporary climate, history and stochastic factors (Rahbek, 2005).Although the pattern in the altitudinal distribution of moths on Mount Jirisan is hump-shaped those for other taxa (e.g.spiders, breeding birds) present on the same mountain are not.While the underlying mechanisms determining the different altitudinal patterns were not examined in the present study; that there are different taxa dependent altitudinal patterns (monotonic decrease vs. hump-shaped) in species richness at the same locality, Mount Jirisan National Park, is intriguing.

Fig. 1 .
Fig. 1.Location of Mt.Jirisan National Park in South Korea and of the seven sites sampled in the National Park.

Fig. 3 .
Fig. 3. Hump-shaped relationship between species richness (total number of moth species collected in 2007 and 2008) and altitude in Mt.Jirisan National Park, South Korea.

Fig. 5 .
Fig. 5. Relationship between species diversity index of the moths collected in 2007 and 2008 and altitude in Mt.Jirisan National Park, South Korea.

Fig. 7 .
Fig. 7. Non-metric multidimensional scaling graph of 7 sites and 402 moth assemblages in Mount Jirisan National Park (final stress = 0.006, 348 degree rotated).Dark triangles indicate sites and if bearing designations for two or more sites overlapping between sites.Each site is identified in Fig 1. Lines indicate the degree of correlation between moth assemblages and variables.Abbreviations and explanation: site (site location, riparian vs. upland), alt (altitude), forest (forest type, conifer vs. deciduous) and aspect (north vs. south).

Fig. 4 .
Fig. 4. Hump-shaped relationship between abundance (total number of moths collected in 2007 and 2008) and altitude in Mt.Jirisan National Park, South Korea.

Fig. 6 .
Fig. 6.Monotonic decrease in the relationship between the evenness index of the moths collected in 2007 and 2008 and altitude in Mt.Jirisan National Park, South Korea.

TABLE 1 .
Description of the sites sampled in Mount Jirisan National Park, South Korea.Location of the sites within the park is indicated in Fig.1.

TABLE 2 .
Summary of the species richness (total number of species), abundance (total number of individuals), Simpson's diversity (D) and Shannon's evenness (E) indices recorded at each of the sites.

TABLE 4 .
The results of a piecewise regression analysis of species richness and abundance relative to altitude.Variables, alt1 and alt2, represent the effect of altitude on species richness above and below 760 m and int1 and int2 the intercepts below and above 760 m. * P < 0.5, ** P < 0.05.List of the moth species sampled at Mount Jirisan National Park from 2007 to 2008.See Fig.1.for the location and abbreviations of the sites.