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Abstract

Contents

Introduction

The study and analysis of species variety is a necessary stage in the implementation of biomonitoring of possible environmental changes. The Muridae rodent suborder includes more than a quarter of all mammal species. This group includes rats, mice, voles, lemmings, hamsters, gerbils and jerboas. They are spread all over the world, except Antarctica, and are found in almost all the terrestrial habitats. The Murine rodents are the most extensive family of modern rodents and mammals in general. It comprises about 120 genera and about 400-500 species. Muridae are part of a unique gene pool of the earth's surface, they play an important role in food chains and largely determine the formation and development of natural ecosystems. They are regarded as a valuable biological model, are of practical interest because of the epidemiological and forestry value. All studies in the field of human toxicology, evaluation of various risks and drug development are based on processing experimental data obtained mostly in the experiments on mice and rats. However, proliferation of small rodents in the wild has not been fully investigated; their community structure is not clearly understood .

1. Subject Topicality

The topicality of the research of Muridae diversity consists in the necessity of investigating rodents’ habitats, their ecological and morphological characteristics and patterns of species distribution according to different parameters. The priority is to study the structural characteristics of communities under specific environmental conditions with regard to their species composition, size, longevity and other parameters. These data are of practical value since changes in the community structure often serve as indicators of natural disturbances.

On the basis of the collected data the data banks are formed. After the accumulation of the sufficient data volume they are used for mining information. The data frequently obtained from various sources are often stored disembodiedly and fragmentally, thus the researcher has actually no systematic and comprehensive information about the object of his interest. Therefore, structured databases (hereafter, DB) are created on the basis of available data and store information in accordance with some ordering and sorting. The data are stored in the database, as a rule, in the third normal form: data consistency and absence of their redundancy. This allows us to draw certain conclusions and build systems of data evaluation, which is an important and urgent task.

2. Aim and Tasks of the Research

The aim of this study is to establish patterns of Muridae species distribution based on the digital cartographic information processing of their distribution areas using GIS technology and the use of Internet-oriented software, as well as the use of the long-term records of species biodiversity in the world.

The main tasks of the research:

  1. Data collection and processing, analysis of existing researches, methods and algorithms.
  2. Design of a database for storage and presentation of digital, graphic and textual data for further research.
  3. Development of GIS models of Muridae species distribution areas.
  4. Establishment of existing relations and patterns of Muridae distribution on the globe.

3. Overview of Existing Databases

At present, a large number of databases in the field of planet’s biodiversity have been created by researchers from different countries [2-6]. However, it should be noted that the available information is often fragmentary and not structured; it includes a variety of indicators, according to which data for some species of the same family and/or any kind either do not exist or only the indicative range of values is known. In addition, the information available in handbooks or displayed on the sites is characterized by various and inconvenient manner of presentation, for example, in the form of photographs, drawings and/or maps with marked corresponding parameters, zones and /or characteristics, either as numeric values or their ranges, but such information is not given for all species. Sometimes this information is represented by separate numbers from the text file, references to other sources and multilingual databases. The species name (family, kind) is commonly presented in the database in Russian, English and Latin. Latin names, common to all countries and languages, are unique for each Muridae species and are necessary for their identification. Russian names of species occur only as translation. In terms of the above said, it is obvious that integration of this information in one database is of actual importance nowadays.

In accordance with the above mentioned, collection and systematization of the existing information and creation of a general database is planned, which allows to apply data mining techniques for establishing biodiversity patterns.

4. Overview of Research and Development

On the basis of existing databases a single database comprising many indicators and graphic images has been built. Alongside this, the given database includes attributive (numerical) data that characterize the average life expectancy, number of litters, the interval between broods, weight, size of individuals, the duration of pregnancy, lactation, intensity of metabolism, etc. for each of the 300 species of the mouse subfamily. The total number of numerical values entered in the database is more than seven thousands. It should be stressed that in the course of the study there have been difficulties, especially with the insufficient knowledge of certain Muridae species and, accordingly, insufficient data on such indicators as number of individuals in the group, life expectancy in the wild, postnatal growth, etc.

Since the distribution areas of most Muridae and a single database map with marked species habitats are absent in the digital form in the existing databases [7], in the course of spatial data collection, the search of cartographic information with images of natural habitats of the investigated species has been carried out via the most popular search engines Google and Yandex. The obtained raster images have been presented as continents or their separate sections with the highlighted distribution areas of this or that species. Collected cartographic information has been digitized and entered in the database as a numeric area value for every distribution area of all the Muridae species in particular and the distribution area of each of species in general. The database also contains a vector map of the world with a variety of layers and marked distribution areas of all the mammalian species under investigation.

The database also includes photos showing the appearance of each analyzed species and raster images of their distribution areas which are stored as *.png. files with a high image compression and minimal quality loss. Depending on the resolution of the bitmap the following quality categories of image representation have been singled out for convenience: of small (257x311 - 469x587 pixels), medium (472x727 - 1060x1083) and large (2000x2090 pixels) resolutions.

To implement the tasks of the research the following methods have been used: mapping, statistical, analytical methods, as well as methods of processing and storage of digital data. The statistical method is used to determine the mode, median, minimum, maximum and average life expectancy, postnatal growth rate, weight, size of the individual, etc., as well as to determine the distribution of various parameters and to establish relationships between them. The analytical method has been applied to carry out a thorough data analysis of Muridae to study and identify all the existing interconnections completely. Mapping that is considered to be reliable and effective has been used as the main investigation method. By means of this technique, consistent digitizing and processing of raster images have been carried out, namely, identification of areas boundaries and areas of the corresponding polygons.

Currently, there are a number of techniques which enable the "removal" of digital information from graphic objects that also comprise methods of obtaining numerical values using graphical editors and methods of analysis and presentation of quantitative data based on the use of special software for digitizing graphics.

MapInfo system which combines advantages of information processing that the databases have (including the query language SQL) and visualization of maps, lists and graphs has been used for statistical and graphical information processing in creating the database. This enabled to design the database Muridae and to fill it with textual, graphical and numerical data with the possibility of determining the parameters of graphical objects (setting boundaries and defining the area of habitat).

The chosen method of processing graphic data is a consecutive process of raster images digitizing and their processing: identification of areas boundaries and areas of polygons. Maps (Figure 1) with marked polygons (the distribution areas of a certain mammal species) that visually stand out against the map have been used as raster images. Further on, these image data have been bound to the vector map of the world [8], after this the raster image has been digitized (vector). On the vector map of the world points have been chosen. Their latitude and longitude present the ultimate points on the raster map, thereby binding ultimate points on the map to the coordinates on the vector map. For this purpose four extra points have been added as the images are usually presented in the form of geometric shapes such as a square, a rectangle.

Figure 1 - Example of a bitmap image

Figure 2 - Editing window checkpoint

Further on, the boundaries of a distribution area of a mammal have been identified, which enables to determine the area inhabited by this or that species in square kilometers (Figure 3).

Figure 3 - The result of tracing the image

By analogy, the processing of about 300 maps that characterize Muridae distribution on the globe has been completed. This work serves as a basis for the creation of Muridae database in the MapInfo environment, which allows not only to store but to fill the database with digital, textual and graphical data.

The database filling has been performed in the following sequence. First, digitized images of species distribution area have been chosen as a polygon, that have been later supported by the attributive information (Figure 4) introduced manually. When choosing a point at the intersection of Muridae distribution areas, living at a certain latitude and longitude, a list of areas of their distribution areas has been displayed (Figure 5).

Figure 4 - Linking digital and textual information

Figure 5 - Several species of Muridae living in the selected area

The resulting vector image located in the newly created database represents one of the layers of the project images. In addition, the user can choose layers which he would like to display or not to display on the screen at his own discretion. When selecting the layers for display it is necessary to choose a tool to manage layers on the action panel and point to the layer you want to display.

Conclusion

Thus, at the first stage of the research GIS models of Muridae distribution have been developed and a database of cartographic and attributive information has been created. The analysis of Muridae distribution enables to organize information about the peculiarities of the species biodiversity using GIS models. It is planned that further studies will be devoted to finding out the patterns of Muridae distribution depending on climate conditions. This is possible by combining the created database for Muridae distribution with the database of the World Climate Center [9-11], which stores the archives of climate data re-analysis. The data archive of the World Climate Centre allows us to construct time-averaged fields of climate indicators for the entire planet. Such averaging can be carried out for 15 years on the latitude-longitude grid of the globe with a cell in a 1x1 degree. The archive contains over 80 climatic parameters, such as temperature, relative humidity, wind speed and direction, light, precipitation, altitude, etc. The amount of the archive data equals several terabytes.

Having analyzed the processed data, we can conclude that at present more than 400 areas of 300 species of the mouse family can be identified on the Earth’s surface. The attributive information from 80 averaged climatic indicators can be correspondingly arranged as a result of a GIS model of Muridae distribution area. The use of the regression analysis enables us to identify the most significant climatic parameters that affect the habitats of the species. In addition, the attributive information quantitatively characterizing each species can be retrieved from the database. That is, the union of the created database and the World Climate Centre database of averaged indicators will make it possible to approach the development of models of species distribution in the world. It is assumed that further investigations will be conducted in this direction.

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