Reproductive and vegetative phenology of the micro endemic Stachytarpheta cassiae (Verbenaceae)

Abstract The flora of the Brazilian rupestrian grasslands represents a hotspot of species richness and endemisms. Stachytarpheta cassiae (Verbenaceae), is a micro endemic species, from which nothing is known. Here, we quantified the activity and intensity of vegetative and reproductive phenophases throughout 12 months and tested for their seasonality and their relationship with local climatic variables. Both vegetative and reproductive phenophases were continuous. No seasonality was observed in the vegetative phenophases and none of them was influenced by climatic variables. Only flower buds and mature fruits’ intensities showed seasonality in February (rainy season) and July (dry season), respectively. Accordingly, increased temperature and humidity combined explained increased production of flower buds whereas decreased rainfall explained increased mature fruits. Higher intensity in flower buds may respond to similar climatic conditions as other species in the community. However, S. cassiae is much different as it continues producing flowers continuously. Higher intensity of mature fruits in the dry season is expected as their seeds are abiotically dispersed. Due to constant flower and leaf production, S. cassia may be a key species for the conservation of many vertebrate and invertebrate species and for maintaining the biogeochemical functioning of the impoverished soils of the rupestrian grasslands.

摘要 巴西岩生草原（rupestrian grasslands）的植物区系是物种丰富度与特有性的热点区域。决明假马鞭（Stachytarpheta cassiae，马鞭草科Verbenaceae）是一种微特有物种，目前对其尚无相关研究。本研究对该物种为期12个月的营养与生殖物候期的活动强度与发生强度进行了量化，并检验了其季节性特征及其与当地气候变量的关联。结果显示，其营养与生殖物候期均呈连续发生状态。营养物候期未表现出季节性特征，且均不受气候变量的影响。仅花蕾与成熟果实的发生强度分别在雨季2月与旱季7月呈现季节性变化。进一步分析表明，温度与湿度的协同升高可促进花蕾的产生，而降雨量的减少则会提升成熟果实的产量。花蕾的高发生强度可能与群落中其他物种响应相似的气候条件有关，但决明假马鞭的独特之处在于其可持续不断地产生花朵。旱季成熟果实的高发生强度符合预期，因其种子依靠非生物方式传播。由于决明假马鞭可持续产生叶片与花朵，其可能作为关键物种，对岩生草原贫瘠土壤中的众多脊椎动物、无脊椎动物的保护以及维持当地生物地球化学功能具有重要意义。