关键词: 花高度, 距长度, 花大小, 选择压力, 变种, 回归分析

Abstract:

Studies on the intraspecific variations of flower traits among different populations, which might result from the selective pressures of different pollinator faunas, could enhance our understanding on the evolution of flower diversity. The first study process is to detect how flower traits of a plant species change in its whole distribution area, which could be observed and measured from herbarium’s specimens. By means of observing and measuring most specimens from several herbaria (PE, KUN, QTPMB, WUK) in China, we presented the patterns of geographical variations in floral traits of Halenia elliptica, which has been identified as two varieties (H.elliptica var. elliptica and H.elliptica var. grandiflora) in light of the differences of flower diameter. We used data of the flower height and spur length to analyze the relationship between flower size and altitude, latitude and longitude using stepwise linear regression. We found that the spur length of H.elliptica var. grandiflora was in the range of H.elliptica var. elliptica, and there was no obvious gap to support the previous taxonomic treatment splitting into two varieties. There was a significant positive relationship between flower height and spur length, and 99% of our data were fallen into the 99% individual prediction interval, suggesting that both flower height and spur length might have experienced the same selective pressure. However, 1% of our data were not fallen into the prediction interval, and this might indicate that the flower height and spur length might have been driven by different selective pressures in comparison with most of the population of H.elliptica. After stepwise linear regression analysis, we found the geometric flower size of this species was negatively correlated with latitude and altitude, but positively correlated with longitude. Furthermore, according to the regression coefficients of each factors, the flower size was affected more by latitude (-2.735) than by altitude (-0.516) and longitude (0.669), which indicates that the geographical variations of flower traits of H.elliptica might change along a latitudinal gradient. Our results suggested that the flower traits of H.elliptica might have been driven by different selective pressures, but the direct evidence from field observations and experiments are absolutely necessary. Furthermore, this study provides a case study to better use herbarium specimens as prerequisites for field researches of floral diversity.

Key words: Flower height, Spur length, Flower size, Selective pressure, Variety, Regression analysis