Quantifying the Danger for Parnassius Nomion on Beijing Dongling Mountain
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DISCRETE AND CONTINUOUS Website: http://aimSciences.org DYNAMICAL SYSTEMS{SERIES B Volume 4, Number 3, August 2004 pp. 679{686 QUANTIFYING THE DANGER FOR PARNASSIUS NOMION ON BEIJING DONGLING MOUNTAIN Ma Zufei, Li Dianmo, Baoyu Xie The National Laboratory of Integrated Management of Insect and Rodent Pests in Agriculture Institute of Zoology, Chinese Academy of Sciences Beijing 100080, P.R.China Abstract. It is the major task of the researches of conservation biology to explore species existing necessary conditions and endanger mechanism [1]. Presently, population viability analysis models mainly focus on a single species and few of them take into account the influence of inter-species e®ect to aimed species [2][3]. It is more di±cult to apply traditional population viability analysis to insects, as compared to birds or mammals. First, insects have complex life histories, small body and various species. For animals that have body length between 10m and 1cm, the number of the species increases by 100 times with the body length shorten by 1/10 [4]. Biologists' knowledge is far from completely understanding insect species, or even the number of insect, because it is very di±cult to obtain the life parameters of wild insect populations. Second, biologists are accustomed to study the key species of the community, which are often the topmost taxa in biology chain or the dominant species in communities. These insect species are rare to be found playing a key role independently in ecosystem maintenance or community succession. Last, many insect species have become extinct before people know them well. The e±cient and comprehensive approach is required to detect why the population of some insect specify is descending and what kind of protective strategies should be applied. In this paper, we have proposed the competition index of Parmassius Nomion species by combining the aimed species population dynamics with the diversity index. The results have shown that the alteration of competition index is able to detect the danger of shrinking population. 1. Introduction Studies on dangerous species' biology and population ecology are very important subject in biodiversity and conservation research. However, there are few studies on relation between the protected species and the components of community, especially the synchronization of dangerous species population dy- namics with fluctuation of concomitant species diversity. Caughley presented the common distinguish methods and procedures to protect descending population [3]. He reported that the study of a descending population should base on long time observation and thorough knowledge of the species. However, Caughley's method is di±cult to apply when the descending population is small since the population descends quickly and may become extinct before people notice their existence, and also it is di±cult to estimate individual number and obtain the information about their mortality by random disturbance for small population. We have studies a lo- cal population of Parnassius Nomion and the other butterflies on the spot. Loss of habitat and increase of natural enemy are the two factors contributing to decreased population of Parnassius Nomion on Dongling Mountain peak from the year of 1998 through 2001. But these two factors play di®erent roles at di®erent times. In this paper we propose the competition index of the Parnassius Nomion population. The change of competition index can be used to determine major e®ect that causes the fluctuations of Parnassius Nomion population. From 1998 through 2000, competi- tion index of Parnassius Nomion population had a small change with descending AMS 2000 Subject Classi¯cation: 92D40. Key words and phrases: competition index, population dynamics, endanger mechanism, insect species, Parnassius nomion. 679 680 ZUFEI MA, DIANMO LI AND BAOYU XIE population density, therefore, the loss of habitat was the main factor. In the year of 2001, competition index decreased rapidly together with the population density, therefore, natural enemy is the main factor. The results of this paper show that competition index is a useful tool to reveal the major e®ect that causes small and descending population to be endangered. 2. Competition Index Biodiversity is the sum of all biotic variation from the level of genes to ecosystems. It has a multitude of facets and di®erent facets of biodiversity can each be quanti¯ed [5]. Any attempt to measure biodiversity quickly runs into the problem that it is a fundamentally multidimensional concept: it cannot be reduced sensibly to a single numbers [6]. To evaluate the competition index of the endangered species, we not only calculate each species' number of individual in all units, but also evaluate the reflecting a±liation of aimed species dynamics and biodiversity changed by competition index fluctuation. The value of competition index could be used to determine whether the population size of aimed species synchronizes with other species. If there are s species in the community, and the jth is the aimed species. The competition index of the jth species is 2 Dj = Pj =¸ Pj = Nj=N X ¸ = (Ni(Ni ¡ 1)=N(N ¡ 1)) Pj is the proportion of number of individual of the aimed species (Nj) in the total individual number (N) in the community. ¸ is Simpson index and is the mea- surement of the concentration (inverse to diversity) [7]. Some of the most popular diversity measures have been formulated as decreasing functions of the concentra- tion index ¸ [8]. For example, ecologists uses 1¡¸ as one of the most frequently used diversity measures [6][9][10]. Besides possessing a number of interesting mathemat- ical properties, this diversity index also has an intuitively appealing interpretation: it is the probability that two individuals selected at random (with replacement) from the sample will belong to di®erent species.However, the diversity index is not describing the competition ability of the aim species in community. This ability is decided by the proportions of individuals belong to the aim species and the other species.If the proportion of individuals belong to the aimed species is higher, than the competition ability of the species is higher too. On the other hand, when the proportion of individuals belong to the aimed species is ¯xed, with the proportions of individuals belong to the other species in the community are lower, what means a lower concentration of species in community, the competition ability of the aimed species is higher. Then this ability should be formulated not only as decreasing 2 function of the concentration index, but also as increasing function of Pj , where Pj is the proportion of individuals belong to the jth species. The competition index of jth species is Dj = Pj=¸. Competition index (Dj) has characters described as follows:1)0 · Dj · 1. When the jth species is extinct, Dj = 0. When only the jth species exists, Dj = 1. 2) Changes of Dj's value is also decided by the syn- chronous of aimed species and the surrounding species. The more synchronization, the smaller the changes of D value will be. 3) When the proportion of the aimed species individuals in the total individuals is constant, Dj value will be larger with a higher diversity of community. 3.Material and Method Parnassius Nomion is on the list of endangered animals in China. Until present this butterfly was found in Korea, Japan, Russia and China. QUANTIFYING THE DANGER FOR PARNASSIUS NOMION 681 There are records of catch in Beijing, Heilongjiang, Jilin, Xinjiang and Qinhai in China [11]-[14]. Dongling Mountain lies in southwest of Beijing, north latitude 40 degree 1 cent and east longitude 115 degree 27 cent, where the annual average tem- perature is 2-8 and annual average precipitation is more than 700mm. Vegetation of Dongling Mountain is distinctly delaminating with the change of altitudes, and but- terfly diversity is high. Since the last two decades of 20 century, Dongling Mountain has been a natural conservative region in Beijing . This Mountain includes three hills. The ¯rst hill is about above sea level 1700-1950 meters, the second is about 1900-2150 meters and the third is about 2100-2300 meters. The plant community in the third hill has clearly divided into three typical vegetation types such as defoliate- broadleaf forest (Betula dahurica forest), defoliate-broadleaf shrubland (Caragana jubata shrubland) and subalpine meadow (Saussurea iodostegia and Carex capil- laris meadow). In the meadow region, we have found four butterfly species such as Melanargia montana, Brenthis ino, Gen sp. and Parnassius Nomion. Through the observation from the year of 1998 to 2001, a population of Parnassius Nomion habitating were found on the south sloping ¯eld of the highest peak, whichis about 2200-2300 meters above sea level. Its area is about 5,000 square meters. The vege- tation type is meadow community with dominance species as Saussurea iodostegia, Carex capillaris, Scabiosa tschiliensis, Carum carui and Potentilla freyniana. The habitat is encircled with shrublands and forests. The Parnassius Nomion popula- tion is isolated because the species live only above altitude of 1,800 meters. The nearest attainable ¯tting habitat is more than 5,000 meters away, and is separated by forests and shrublands. We have observed and noted butterflies population size in the habitat from the year of 1998 to 2001. It was separated to two periods. The ¯rst was from May 25 through September 22 in 1998, each two observations had a ten days interval, and began at 10:00 and ended at 17:00 for each day. The butterfly populations were estimated and recorded in every hour to grapple the imagoes annual activity rule and day activity rhythm. The second is from July 14 to August 3 in 1999 year to 2001 year, the observation began at 12:00 and ended at 13:00 for each day.