• Animal Systematics, Evolution and Diversity
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• 제28권4호
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• pp.279-290
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• 2012

Plecoglossus altivelis (ayu) is an amphidromous fish widely distributed in Northeastern Asia from the East China Sea to the northern Japanese coastal waters, encompassing the Korean Peninsula within its range. The shore lines of northeastern region in Asia have severely fluctuated following glaciations in the Quaternary. In the present study, we investigate the population genetic structure and historical demographic change of P. altivelis at a population level in East Asia. Analysis of molecular variance (AMOVA) based on 244 mitochondrial control region DNA sequences clearly showed that as the sampling scope extended to a larger geographic area, genetic differentiation began to become significant, particularly among Northeastern populations. A series of hierarchical AMOVA could detect the genetic relationship of three closely located islands between Korea and Japan that might have been tightly connected by the regional Tsushima current. Neutrality and mismatch distribution analyses revealed a strong signature of a recent population expansion of P. altivelis in East Asia, estimated at 126 to 391 thousand years ago during the late Pleistocene. Therefore it suggests that the present population of P. altivelis traces back to its approximate demographic change long before the last glacial maximum. This contrasts our a priori expectation that the most recent glacial event might have the most crucial effect on the present day demography of marine organisms through bottleneck and subsequent increase of effective population size in this region.

• 농촌지도와개발
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• 제12권1호
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• pp.17-28
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• 2005

This study investigated structural changes of the Korea's agriculture and proposed the new direction of rural and agricultural policy in Korea after economic opening. The major results may be summarized as follows: Firstly, the study identified structural changes of the country's peasantry under the economic opening system. Korean agriculture has been deteriorated in population structure, arable land size, and income composition. Secondly, according to above analysis on these changes it suggested that the traditional rural communities were exposed to collapse and this unwanted disaster could result in serious adversities to the national economy. Thirdly, this study proposed preservation policies for small scale farming households and also administrative preparations of multi-dimensional approaches leading to successful rural and agricultural planning.

• The Journal of Asian Finance, Economics and Business
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• 제9권3호
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• pp.135-147
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• 2022

This study was conducted to determine whether there is a significant relationship between board structure and board committee qualities and corporate cash holdings in Pakistan. For this objective, 168 listed enterprises on the PSX for the period 2016 to 2020 were chosen as a sample from a population of 436 non-financial firms. Multiple regression analysis was used in the study to discover a relationship between board structure and board committee features and cash holdings. The study's findings revealed that board size, executive directors, and board independence have no significant impact on the firm's cash holding because they play no important part in the firm's cash holding. Auditors, audit committee size, audit committee meetings, and the compensation committee, on the other hand, have no major impact on the firm's cash holdings because they are not relevant indicators to compare with cash holdings. While board meeting frequency and leadership structure both have a negative influence on cash holding, board meeting frequency increases firm costs, whereas leadership structure causes agency problems. Results were supported by the pecking order theory, cash flow theory, and agency theory.

• The Korean Journal of Ecology
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• 제18권4호
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• pp.503-512
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• 1995

The present paper describes partial results of the study on the activities of microbes in the soil of Quercus mongolica forest from July, 1994 to April, 1995. To determine the relationship between structure and function of soil microbial ecosystem, the author investigated the seasonal change of physical environmental factors, microbial population and soil enzyme activities. The changes of pH was not significant and the temperature of surface soil was 2℃ higher than lower soil through out the year. Moisture contents (％) of soil samples ranged from 7.64％ to 42.11％. However, soils of site 3 at Mt. Komdan in which vegetation is successional have higher moisture content than the others. The bacterial population increased in summer, but continuously decreased in autumn and winter, and then reincreased again in spring. Bacterial population of surface soil was higher than those of 30 cm depth all the year round. Dehydrogenase activity (DHA) was about two-fold higher throughout in surface soil compared to those of lower soil. And the correlation coefficient between DHA and bacterial population size was 0,713, It was suggested that DHA could be used as a primary index of soil microbial population and activity in soil ecosystem.

• Proceedings of the National Institute of Ecology of the Republic of Korea
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• 제3권4호
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• pp.191-198
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• 2022

Natural habitats of the Korean long-tailed goral (Naemorhedus caudatus) have been fragmented by anthropogenic activities in South Korea in the last decades. Here, the individual identity, genetic variation, and population differentiation of the endangered species were examined via the multiple-tube approach using a non-invasive genotyping method. The average number of alleles was 3.16 alleles/locus for the total population. The Yanggu population (1.66) showed relatively lower average number of alleles than the Inje population (3.67). Of the total 19 alleles, only seven (36.8%) alleles were shared by the two populations. Using five polymorphic out of six loci, four and six different goral individuals from the captive Yanggu (n=24) and the wild Inje (n=28) population were identified, respectively. The allele distribution was not identical between the two populations (Fisher's exact test: P<0.01). A considerably low migration rate was detected between the two populations (no. of migrants after correction for size=0.294). Additionally, the F statistics results indicated significant population differentiation between them, however, quite low (F_ST=0.327, P<0.01). The posterior probabilities indicated that the two populations originated from a single panmictic population (P=0.959) and the assignment test results designated all individuals to both populations with nearly equal likelihood. These could be resulted from moderate population differentiation between the populations. No significant evidence supported recent population bottleneck in the total Korean goral population. This study could provide us with useful population genetic information for conservation and management of the endangered species.

• 한국산림과학회지
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• 제105권3호
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• pp.309-314
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• 2016

변화하는 자연환경에서 식물이 생존하기 위해서는 적절한 유전다양성을 유지할 뿐 아니라 지역적응성을 갖추어야 세대를 성공적으로 이어나갈 수 있다. 만약 유전다양성이 급격히 감소하게 된다면 집단이 쇠퇴하고 소멸 위험성이 커지게 된다. 본 연구는 주변 집단으로 부터 화분이나 종자의 유입이 어려운 소규모 사시나무 집단의 유전구조를 구명하였다. 월악산 미륵리의 사시나무림은 전체 분포면적 $14,000m^2$에 성목은 350개체로 추정되며, 임분내에 설정한 $70m{\times}70m$ 조사구에 출현하는 123개체 중 61개체를 대상으로 AFLP 마커를 이용하여 유전변이를 분석하였다. 조사구내 사시나무의 수령은 평균 16년 최고 32년생이었으며, 개체의 공간적 분포는 약한 밀집 형태를 이루고 있었다. AFLP primer 6조합에서 196개 증폭산물을 확인하였으며, 이 중 151개는 다형성을 보였다. primer 조합당 평균 유전자좌수는 32.7(표준편차=7.2), 이형접합도 기대치($H_e$)는 0.154, Shannon의 다양성 지수(S.I.)는 0.254로 나타나서, 월악산 사시나무는 우리나라 사시나무 집단 평균에 비하여 매우 낮은 유전다양성을 갖고 있는 것으로 나타났다. 공간적 유전구조는 24 m 이내에서 분포하는 개체들 간에 유전적 유사성이 나타났으며, 소규모 면적과 고립된 분포지 특성으로 인하여 비교적 작은 유전군락이 형성된 것으로 생각된다.

• Journal of Ecology and Environment
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• 제31권1호
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• pp.9-15
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• 2008

Growth and reproduction of Palaemon serrifer were described and analyzed in a population inhabiting tide pools in warm temperate waters in Korea. The water temperature varied greatly in the tide pools, ranging from 8$^{\circ}C$ to 27.8$^{\circ}C$ Population structure and growth were investigated using size frequency distribution data collected from January to December 2003. Sex ratios fluctuated, but were almost equal during the breeding period. Growth was continuous and size increased gradually throughout the year. Adult females were larger and grew faster than males. von Bertalanffy growth parameters for a one-year sample of females and males were estimated as $L_{i\ddot{A}}$ = 11.32, K = 0.311, $t_0$ = -0.4115 and $L_{i\ddot{A}}$ = 8.36, K = 0.228, $t_0$ = -0.9693 respectively. Breeding was seasonal, starting in May, peaking in August, and finishing by the end of August. The species showed continuous production of successive broods. Laboratory observation showed that females with embryos near hatching had ovaries filled with vitellogenic oocytes ready for spawning. The reproductive output (effort) of each female (mean number of eggs: $552{\sim}1355$) was not high. The mean embryo volume, $0.078mm^3$, is relatively small, indicative of low energy allocation to each embryo. Recruitment of juveniles was closely linked to the breeding period, beginning in September.

• The Korean Journal of Ecology
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• 제20권6호
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• pp.423-438
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• 1997

The structure and variation of the mating call in Rana nigromaculata was studied in a population at Da-rak, Chong-won, Chung-buk (36$\circ$ 37' latitude, 127$\circ$ 21' longitude) in Korea. The mating call consists of 3 to 8 pulse groups divided by clear silent intervals. Each pulse group is also composed of fine pulses. Temperature and body size affect the temporal and spectral characteristics of the mating call. Pulse, pulse group repetition rate and dominant frequency rise with increasing temperature, whereas pulse grouprepetition rate and dominant frequency decrease with increasing body size. A playback experiment was designed to establish the effect of a potential intruder on male calling. During the stimulus periods, resident males markedly decreased the pulse repetition rate, and icreased the rate of pulse groups, dominant frequency, and the number of call groups. This results indicate that this species responds in a graded fashion when interacting with other individuals.

• Fisheries and Aquatic Sciences
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• 제12권2호
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• pp.138-151
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• 2009

We quantitatively investigated compositions of fish and invertebrate bycatch in Korean shrimp fisheries. We sampled shrimp trawl bycatch from 48 commercial trawls over 1 year. These samples contained 108 taxa from 50 families, with 60 fish taxa contributing 51.2% of the total biomass and 48 invertebrate taxa 48.8%. However, 86.32% of the total individual organism density comprised invertebrates, while individual fishes made up the remainder. Within the bycatch, two fish species varied in population size structure by season, suggesting recruitment is seasonal in these taxa. Overall general catch characteristics (total bycatch biomass and organism density) varied significantly by season and tide, and a significant interaction effect was observed (season$\times$tide) on total density, but not on total biomass. The data collected will be used in designing a program of long-term bycatch monitoring.

• 한국시스템다이내믹스연구
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• 제12권2호
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• pp.95-126
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• 2011

This paper aims at developing a System Dynamics model with an augmented predator-prey interaction structure to deal with the population management of roe deer in Jeju, Korea. Although people still regard the creature as one of the important tourist attractions, there has been much debate on the issues of the appropriateness of the population size of roe deers because they have been stigmatized as crop damagers, and roadkill/poaching victims due to their natural habit to move around from the top mountain to the lowland of the island. The model is therefore to incorporate these migrating and grazing behaviors into an augmented Lotka-Volterra model coupling roe deer population in both parts of the island to that of predators and preys of the species. The authors also provide a comprehensive set of dynamic hypotheses and relevant CLD/SFD to understand the population dynamics of roe deer and co-evolving species and perform the steady-state analysis of the proposed equation system to verify the model behavior of the numerical example lastly presented in this paper.