| Midday gerbils(Meriones meridianus Pallas,1773) belong to the Rodentia, Cricetidae, Meriones. They are common in sandy areas in Mongolia, Kazakstan, Iran and Afghanistan, and can be found to the west as far as the Caspian Sea coast. In China midday gerbils are mainly distributed in midwest of Inner Mongolia, north of Shanxi and Shanxi, Ningxia, Gansu, Qinghai and Xinjiang province. They can be found from150meters below the sea level to3200meters above sea level. As a highly adaptable species, more than10subspecies so far are recorded. According to the literatures, there are7subspecies in China. They are (1) M. m. psammophilus Miline-Edwards,1871;(2) M. m. buechneri Thomas,1909;(3) M. m. muleiensis Wang,1981;(4) M. m. penicilliger Heptner,1933;(5) M. m.jei Wang,1964;(6) M. m. cryptorhinus Blanford,1875;(7) M. m. lepturus Buchner,1889, respectively.In order to find out the rule of geographic variation on morphological characters of midday gerbils in China,339adult individuals of M. meridianus were measured, which were trapped by the rattrap at25sites from July of2008to October of2010in Inner Mongolia, Ningxia, Gansu, Qinghai and Xinjiang province, northwest of China. Partial correlation analysis and multiple linear regression analysis were used to analyze the variation between midday gerbil’s body mass (BM), body length (BL), tail length (TL), ear length (EL), hind foot length (HFL), relative tail length (RTL), relative ear length (REL), relative hind foot length (RHFL)8body mass and measurements, greatest length of skull (GLS), mastoid breadth (MB), greatest length of the nasals (GLN), relative mastoid breadth (RMB), relative greatest length of the nasals (RGLN), skull size (SS), size of auditory bulla (SAB), relative size of auditory bulla (RSAB)8skull measurements and heart dry mass (HE), lung dry mass (LU), liver dry mass (LI), kidneys dry mass (KI), spleen dry mass (SP), relative heart dry mass (RHE), relative lung dry mass (RLU), relative liver dry mass (RLI), relative kidneys dry mass (RKI), relative spleen dry mass (RSP)10organ masses with latitude and altitude2geographical factors, and annual mean temperature (TEM), frost-free period (FFP), relative humidity (HUM), precipitation (PRC), annual sunshine hours (SUN), annual average wind speed (WIN)6climatic factors. This study got the following conclusion:Partial correlation analysis were used to analyze the relationship between midday gerbil’s8body mass and measurements,8skull measurements and10organ masses with2geographical factors. The results showed that:(1) For the midday gerbil’s8body mass and measurements, ear length, tail length, hind foot length, relative ear length and relative tail length were significantly negatively correlated with latitude, body mass, body length and hind foot length were significantly positively correlated with altitude, tail length, relative ear length and relative tail length were significantly negatively correlated with altitude;(2) For the midday gerbil’s8skull measurements, relative mastoid breadth was significantly positively correlated with latitude, greatest length of the nasals, relative greatest length of the nasals, size of auditory bulla and relative size of auditory bulla were significantly negatively correlated with latitude, greatest length of skull, greatest length of the nasals, relative mastoid breadth, relative greatest length of the nasals, skull size, size of auditory bulla and relative size of auditory bulla were significantly positively correlated with altitude;(3) For the midday gerbil’s10organ masses, spleen dry mass, relative liver dry mass, and relative spleen dry mass were significantly positively correlated with latitude, lung dry mass and relative lung dry mass were significantly negatively correlated with latitude; heart dry mass, lung dry mass, liver dry mass, kidneys dry mass, spleen dry mass (male) and relative liver dry mass were significantly positively correlated with altitude.Multiple linear regression analysis were used to analyze the relationship between midday gerbil’s8body mass and measurements,8skull measurements and10organ masses with6climatic factors. The results showed that:(1) For the midday gerbil’s8body mass and measurements, the change of body mass, body length and relative hind foot length were mainly caused by the change of frost-free period, the change of ear length and relative ear length were mainly caused by the change of annual sunshine hours, the change of tail length and relative tail length were mainly caused by the change of annual average wind speed, the change of hind foot length was mainly caused by the change of relative humidity;(2) For the midday gerbil’s8skull measurements, the change of greatest length of skull, greatest length of the nasals, relative mastoid breadth, relative greatest length of the nasals, size of auditory bulla and relative size of auditory bulla were mainly caused by the change of frost-free period, the change of mastoid breadth was mainly caused by the change of precipitation; the change of skull size was mainly caused by the change of relative humidity;(3) For the midday gerbil’s10organ masses, the change of heart dry mass (female), spleen dry mass (male) and relative heart dry mass (female) were mainly caused by the change of annual mean temperature, the change of heart dry mass (male), lung dry mass, liver dry mass, kidneys dry mass and relative lung dry mass were mainly caused by the change of frost-free period, the change of relative heart dry mass (male) was mainly caused by the change of precipitation, the change of relative kidneys dry mass was mainly caused by the change of annual sunshine hours, the change of relative spleen dry mass (female) was mainly caused by the change of relative humidity.In this study, hierarchical cluster analysis were used to cluster31variable mean measurements of midday gerbil from the25sites, including8body mass and measurements and23skull measurements, and great gerbil (Rhombomys opimus) as outer cluster. At the same time, some literatures of molecular biology of midday gerbils were reviewed, and we discussed taxonomy of7subspecies in China.We banded together the Phylogenetic tree analyses (NJ method and MP method) composed of mitochondrial cytochrome-6gene. The results demonstrated that:(1) M. m. cryptorhinus and M. m. lepturus are all belong to M. m. psammophilus. Diagnosis: they are bigger, with the body weight averaging60g, and the length of head and body about120mm. Tail is slightly shorter than the head and body length, averaging90%of the latter. Upper surface with hairs is thus of a dark brown hue, almost not showing gray in colour. Tail is thickly and fluffy, and the tail tuft black or light. Distribution: midwest of Inner Mongolia, north of Shanxi and Shaanxi, Ningxia, Gansu, Qinghai, east and south of Xinjiang;(2) M. m. muleiensis and M. m. jei are all belong to M. m. penicilliger. Diagnosis:smaller, with the body weight averaging45g, and the length of head and body about110mm. Tail is almost as same long as the head and body length, averaging100%of the latter. Upper surface with hairs being thus of a grayish-buff hue, almost show dark gray in colour. Tail thinly and closely, the tail tuft is black or dark. Distribution:Tianshan Mounts areas of Xinjiang, including Turpan Basin, Gurbantonggut Desert, Usu Desert and Yili River Valley;(3) As there were not enough specimens to carry on hierarchical cluster analysis, we were not sure of the subspecies classification of M. m. buechneri, but the evidence of molecular biology supported this conclusion. |
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