| Rhombomys opimus and Meriones meridianus are common species in the region of middle Asian deserts. Their habitats overlap in many places. Wherever Rhombomys opimus inhabits, Meriones meridianus is concomitant. They have become a guild in the desert rodent community after long-term natural selection and genetic evolution. This papers studied the difference of two rodent's niche from their food, reproduction, active period.etc in different seasons in order to find out the reason why they have coexisted steadily for a long time in Jinghe Ganjia Lake(national conservation )From April in 2002 to October in 2003, we conducted 9 times wildness investigation in the way of plots-area with traps, traps was distributed according to 5X20, which last 72 hours and was checked every morning and dusk. The bait we used is carrot and fried bread. Clap is middle broad clap. We counted the numbers of capture two kinds of rodents, measuring with common biology methods, dissecting and recording number of embryos and womb spots, keeping the bone of head.. We measured the two species' spatial internal distribution pattern with David ,Moor and Lloyd ways ,calculating their time and space niche broad index and niche overlap index, observing two rodents' active period in different seasons. We also studied the habits by micro-tissue analysis, the conclusions are as follows: 1. Rhombomys opimus and Meriones meridianus have the cluster distribution in different seasons, but the cluster density in spring and autumn is stronger than in summer. The two rodents have the positive relation which means M.m live in the place where O.p live. Their habitats overlap.2. Rhombomys opimus and Meriones meridianus have relative broaden spatial niche which are fluctuate in different seasons. Spatial niche broaden index (Bi )in spring and autumn are higher than in summer, respectively. O.m has higer Bi than M,m in autumn but lower in other seasons. The Bi in the whole year of M,m is higher than O.m's. So M.m is the dominant species in the area where we studied.3. Rhombomys opimus and Meriones meridianus have two different active period in spring and autumn: the follower choices daytime to act but the later choices the nighttime to act. In autumn, both of them choice daytime to act and their active time overlaps.4.Both of rodents have two breeding peak in spring and autumn respectively, and spring's breeding peck is higher than in autumn. R o advanced by 15 or 20 days in proliferation in spring compared with M. M. but in autumn ,it reversed.5. Rhombomys opimus is a kind of onefold folivore. It likes eating plant's stems and leaves which contain lots of water while Meriones meridianus is a kind of omnivore, Besides those foods that O.p eat, it eats also eats plenty of seeds, insects etc.We conformed that R.o and M.m coexisted in the same habitation of the middle latitude of deserts for a long time, based on food, activity , growth and proliferation...
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