SIZE-DEPENDENT REPRODUCTIVE OUTPUT AND LIFE-HISTORY STRATEGIES IN FOUR EPHEMERAL SPECIES OF TRIGONELIA
胡卢巴属4种短命植物个体大小依赖的繁殖输出与生活史对策

Phenological characteristics and patterns of biomass allocation were studied in four ephemeral species of Trigonella (T. cancellata, T. arcuata, T. monantha and T. orthoceras) from the Zhungaer desert. The results showed that germination strategies were diverse among species. Seed germination occurred in the spring, summer and autumn in all four species, but was most prevalent in the spring and autumn. The germination time of seeds was very closely related to environmental factors, such as temperature and precipitation. There were no obvious interspecific differences in germination time. Plant growth was quick and the life cycle short in all four species. The fruits maturate before the arrival of the arid summer season. All four species are monocarpic, and their life-history strategy can be described as that of escaping aridity. The reproductive yield of plants germinated in the spring and autumn was maximized by an instantaneous switch from vegetative growth to reproductive growth after a short period of vegetative growth. The four species allocate a high proportion of carbon to reproductive output and was 62.3%, 51.9%, 54.3% and 58.3% for the four species, and the absolute measures of reproductive output were size-dependent. The reproductive output increased with plant size, with the r-value 0.989, 0.935, 0.720 and 0.924 in all the four species (p<0.001). There were significant differences in the size (p<0.01) and the reproductive output (p<0.05, p<0.01) among plants that germinated in different seasons. The plants that germinated in the spring were smaller and their reproductive output lower than those hat germinated in the autumn, but the difference in the proportion of reproductive allocation was not significant (p>0.05). These results indicate that differences in reproductive output can be explained by size differences in plants from different germination times. Finally, we discussed the life-history strategies of the four ephemeral species and analyzed their differences based on individual size, survival ability and reproductive output of plants germinated during different season, and their adaptation strategies to the arid environment of the Zhungaer desert.