Reproductive phenology of Ditassa burchellii (Apocynaceae, Asclepiadoideae), a herbaceous vine, in a semi-deciduous forest from Brazil

Abstract We analyzed the reproductive phenology of Ditassa burchellii and the influence of abiotic factors on the species phenophases. The study was conducted on individuals of a natural population from a semi-deciduous forest (Viçosa municipality, Minas Gerais state, southeastern Brazil). We quantified the activity and intensity indices of the following phenophases: flower bud, flower, immature fruit, and dehiscent fruit. To test for seasonality of phenophases, we analyzed each of them using Rayleigh test. We evaluated whether there was any association between abiotic variables (mean temperature, rainfall, and day length) and phenophases, in the month of occurrence and in the three months prior to the occurrence of each phenophase. The analyzed phenophases occurred mainly at the end of the rainy season and during the dry season, with overlapping periods, but with sequential peaks. The periods of occurrence of reproductive phenophases were similar to the ones in other climbing species and were mainly related to the dispersal mode. All phenophases were seasonal and were associated with at least one abiotic variable, either in the month of their occurrence or in the previous months.

摘要 本研究针对布氏迪塔沙藤（Ditassa burchellii）的生殖物候特征，以及非生物因子对其物候期的影响展开分析。研究以巴西东南部米纳斯吉拉斯州维索萨市半落叶林内的自然种群个体为研究材料，量化了现蕾期、开花期、幼果期及裂果期4个物候期的活动度与强度指数。为检验各物候期的季节性特征，本研究采用瑞利检验（Rayleigh test）分别对各物候期进行统计分析。我们进一步评估了非生物变量（平均气温、降雨量、日照时长）分别在物候期发生当月及发生前3个月时，与各物候期的关联情况。结果表明，所分析的生殖物候期主要集中于雨季末期与旱季时段，各物候期存在发生重叠但峰值依次出现。该物种的生殖物候发生时段与其他藤本植物相近，且主要与其传播方式相关。所有物候期均表现出季节性特征，且至少与一项非生物变量存在关联，无论该关联是在物候期发生当月还是前序月份。