Life History, Life Table, Habitat, and Conservation of Byasa Impediens (Lepidoptera: Papilionidae)
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ACTA ECOLOGICA SINICA Volume 26, Issue 10, October 2006 Online English edition of the Chinese language journal Cite this article as: Acta Ecologica Sinica, 2006, 26(10), 3184−3197. RESEARCH PAPER Life history, life table, habitat, and conservation of Byasa impediens (Lepidoptera: Papilionidae) 1,2,3 1, 2 4 Li Xiushan , Zhang Yalin *, Luo Youqing , SETTELE Josef 1 Key Laboratory of Plant Protection Resources and Pest Management of the Ministry of Education of China, Entomological Museum of Northwest Sci-Tech University of Agriculture and Forestry, Yangling 712100, China 2 Key Laboratory of Forest Silviculture and Conservation of the Ministry of Education, College of Resources and Environment of Beijing Forestry University, Beijing 100083, China 3 Station of Forest Pests and Diseases Control and Quarantine of Gansu Province, Lanzhou, 730050, China 4 Helmholtz Centre for Environmental Research - UFZ, Department of Community Ecology, Theodor-Lieser-Str. 4, 06120 Halle, Germany Abstract: This article investigates the biology of Byasa impediens, presenting its life-table data and analyzing its habitat require- ments and the key factors threatening the survival of this species. This study also aims to detect specific protection methods to guarantee the long-term survival of Byasa impediens in Baishuijiang Reserve. Byasa impediens is bivoltine in Baishuijiang Reserve. The pupae overwinter on shrubs or on branches of trees. The eclosion of the first generation starts in mid-April. The adults of the first generation emerge in large numbers in mid-late May, and the second generation emerges from late June to mid-July. The two generations overlap. The adult males emerge 7–10 days earlier than the adult females. Their flight behavior is determined by factors such as perching along small rivers and gullies, and visiting flowers. The males are strong fliers. On the contrary, the flying ability of the females is weak; therefore, they just visit flowers, mate, and lay eggs near the natal area. The ratio of female to male is 1:4.1. The maximum lifespan of the males is 26 days, with an average of 6.9 days, whereas the maximum lifespan of the females is 21 days, with an average of 7.6 days. The pregnant eggs per female are 31.5 on average. The incubation period of the first generation is 12–14 days, whereas that of the second generation is 7–9 days. The larvae feed mainly on Aristolochia heterophylla. The larval period of the first generation lasts for 30 days with five instars and that of the second generation lasts for 30–40 days with five or six instars. The pupal period of the first generation begins in early June and lasts for 20–26 days whereas for the second generation, it begins between late July and late September. The adults prefer the following nectar plants: Albizzia julibrissin, Bauhinia glauca, Clerodendrum bungei, and Sambucus chinensis. The plant Aristolochia heterophylla is distributed at an altitude of 900–1680 m, and the most suitable range is 1200–1500 m. The host plants grow mainly along the paths and along the borders of forests where the canopy is rather open and shrubby undergrowth is found. The plant can hardly be found when the canopy density of the forest is greater than 80%. The elevation range most suitable for the larvae is 1200–1500 m. The ideal habitat of host plants also seems to be the ideal habitat of Byasa impediens. The key factors that adversely affect the population of Byasa impediens are loss and deterioration of habitats. The loss and deterioration of the habitats result in a decrease in the numbers of host plants and a more restricted distribution of the potential habitats. The habitat is easily influenced by anthropogenic activities, such as herding, cultivating, and using pesticides, which in turn influences the growth of the host plant Aristolochia heterophylla and the larvae of butterflies. Abnormal climatic conditions and natural enemies are the key factors affecting population density. The hot and dry weather in summer and the heavy rain in autumn considerably reduce the survival rate of eggs and larvae. The ichneumon parasitoids reduce the survival rate of the over-wintering pupae. The primary natural enemies of the larvae include spiders, earwigs, wasps, bugs, and ichneumon parasitoids. Other natural enemies of pupae and adults are birds. The most important conservation measures are preservation and reconstruction of the natural habitat, which includes rebuilding forests, enhancing management, enforcing existing laws, and developing eco-tourism. Creating a core-patch near all patches at a central area is also an important measure for conservation. In the most ideal habitat, appropriate shrub cutting can increase the growth of host plants, thereby promoting expansion of the Byasa impediens population. Key Words: Byasa impediens; biology; life table; population threats; suitable habitats; conservation measures Received date: 2005-08-07; Accepted date: 2006-08-12 *Corresponding author. E-mail: [email protected] Copyright © 2006, Ecological Society of China. Published by Elsevier BV. All rights reserved. LI Xiushan et al. / Acta Ecologica Sinica, 2006, 26(10): 3184–3197 Butterflies are regarded as good indicators of environmental species and thus not listed in the national list of protected ani- changes because of their sensitivity in detecting even slight mals, it is a good indicator of the quality of forest margins and changes in the environment. Therefore, butterfly conservation clearings because of the existence of the larvae of Byasa and monitoring are receiving increasing attention from impediens. Its habitats are easily disturbed by anthropogenic conservationists. By means of long-term monitoring of the activities, which may lead to severe decline in its local popula- dynamics on particular sites, the relations between the changes tion size. Thus it is a very suitable species for research on in butterfly diversity and species inventory in certain landscapes conservation biology. and the environmental changes and variation can be studied. There have been very few Chinese and international research They can be used to evaluate the habitat quality and to de- reports on the genus Byasa related to morphology, biology, velop concepts for environmental protection and ecosystem chemistry pheromen, and manual breeding[12], which show restoration. Because of their short life cycle, narrow distribu- that its biological characteristics are very different in different tion, large population fluctuations combined with their rela- places. The number of generation of the species increases tively easy availability for research, they have become one of toward the south. However, there have been no reports on its the primary groups for research in conservation biology. Many life in natural habitats, life tables and conservation up to now. theories in conservation biology, especially the theory of To protect Byasa impediens and other closely related species, metapopulation biology, emerged from research on butterfly[1]. the biology of Byasa impediens was thoroughly studied in At present, researches on butterfly ecology and conservation Baishuijian Natural Reserve, Gansu, China, from 2001 to have increased exponentially on a global scale[1]. These re- 2003. The life tables in natural sites and the environmental searches focus on population structure[2], population dynamics, requirements for survival have been investigated, and the most habitat requirements, extinction risk[3], population viability important factors that threatened survival are analyzed. Ade- analysis [4], genetic variation of rare species, influence of cli- quate conservation measures are recommended,and the main matic variation on butterfly populations, conservation meas- results are dealt with in the subsequent sections. ures, and so on. The research methods include capture- recap- ture[2], transect investigation, spatial grids, various models and 1 Materials and methods remote-sensing data, GIS (Geographical Information System) 1. 1 Materials and so on[5]. Study species Study on life tables is one of the most important means to Byasa impediens (Rothschild): eggs, larvae, pupae, and adults. study the population dynamics of rare butterflies. It helps to Host plants: Aristolochia heterophylla Hemsl. assess mortality rates at various stages in the life cycle. How- A. debilis S. ever, several years of observation is needed for obtaining use- A. mandshuriensi Kom. ful results through this assessment. At the same time, the life Equipments: camera with a macrolens (1:1, 1:2, 1:4) and a tables are necessary to identify the key factors that influence large zoom lens, GPS (global position system), vernier caliper, the population size[6]. Habitat quality is a main factor that insect breeding net, insect breeding box, sweep net with long influences the probability of butterfly extinction. It comprises handle (3m), red marker pen, dry and wet thermo-meters, the following factors: habitat diversity and richness, host and absorbent cotton, specimen box, insect needle, label, etc. nectar plants, and degree of habitat isolation and patch area[7]. 1. 2 Research area In China, research on butterfly conservation is just at the The research was carried out at the southeastern edge of commencement stage. This research particularly emphasizes Gansu Baishuijian Natural Reserve, at the Bifeng creek, with a on species inventories (catalogues), analysis of species south-to-north extension and a total area of about 30 km2. The composition[8], observation of biology[9], and assessment of altitude of the valley ranges from 600 m to 1800 m. The creek anthropogenic influences on butterfly communities[10]. Further is about 8 km deep, and its mouth lies in Bikou town at an alti- research is quite necessary in this direction. tude of 600 m. The entire valley is composed of one main Byasa impediens (Rothschild) belongs to family Papilioni- creek and ten branches. All branches are separated from each dae and genus Byasa Because of the presence of numerous red other by ridges. The altitudes of the two side highest mountains spots on the abdomen and the underside of wings, it looks delineating the valley are between 1600 m and 1800 m.