Reproductive allocation patterns in different density populations of spring wheat.
The effects of increased intraspecific competition on size hierarchies (size inequality) and reproductive allocation were investigated in populations of the annual plant, spring wheat (Triticum aestivum). A series of densities (100, 300, 1000, 3000 and 10,000 plants/m(2)) along a gradient of competition intensity were designed in this experiment. The results showed that average shoot biomass decreased with increased density. Reproductive allocation was negatively correlated to Gini coefficient (R(2) = 0.927), which suggested that reproductive allocation is inclined to decrease as size inequality increases. These results suggest that both vegetative and reproductive structures were significantly affected by intensive competition. However, results also indicated that there were different relationships between plant size and reproductive allocation pattern in different densities. In the lowest density population, lacking competition (100 plants/m(2)), individual reproductive allocation was size independent but, in high density populations (300, 1000, 3000 and 10,000 plants/m(2)), where competition occurred, individual reproductive allocation was size dependent: the small proportion of larger individuals were winners in competition and got higher reproductive allocation (lower marginal reproductive allocation; MRA), and the larger proportion of smaller individuals were suppressed and got lower reproductive allocation (higher MRA). In conclusion, our results support the prediction that elevated intraspecific competition would result in higher levels of size inequality and decreased reproductive allocation (with a negative relationship between them). However, deeper analysis indicated that these frequency- and size-dependent reproductive strategies were not evolutionarily stable strategies.
Liu
Jing
J
Key Laboratory of Arid and Grassland Agroecology at Lanzhou University, Ministry of Education, Lanzhou 730000, China.
Wang
Gen-Xuan
GX
Wei
Liang
L
Wang
Chun-Ming
CM
D018533:Biomass; D002681:China; D002980:Climate; D011157:Population Dynamics; D012044:Regression Analysis; D012098:Reproduction; D014908:Triticum / Q000033:anatomy & histology / Q000502:physiology*