Studies from different parts of the world have generated pieces of evidence of climate change’s effects on plant phenology as indicators of global climate change. However, datasets or pieces of evidence are lacking for the majority of regions and species, including for the climate-sensitive Himalayan biodiversity hotspot. Realizing this gap in information, and the wide-ranging implications of such datasets, we integrated real-time field observations and long-term herbarium records to investigate the changes in the spring flowering phenology of Olea ferruginea Royle, commonly known as the Indian Olive, in response to the changing climate in the western Himalayas. We attempted to create phenological change model using the herbarium records and field observations after recording the current dates of flowering and overall temperature trends from the study area over the last four decades from the five regional meteorological observatories of the Jammu province managed by Indian Meteorological Department (IMD) in Jammu and Kashmir. When considering current flowering dates along with herbarium information (years 1878–2008) for O. ferruginea, our Generalized Additive Model (GAM) showed 15–21 days-early flowering over the last 100 years significantly (p < 0.01). Results of the Mann–Kendall test showed increasing trends of T_Min for all seasons significantly (p < 0.05) for Jammu province whereas T_Max was only for the spring season. The increasing T_Min of spring, summer, and autumn seasons also influenced the flowering phenology of O. ferruginea significantly (p < 0.01). By demonstrating the integrated use of methodological tools for finding long-term phenological changes in response to climate change, this work bridges knowledge gaps in phenological research from the developing world in general and the Himalayas in particular.

Context: Reproductive success in dioecious plant species may be limited by severe pollen limitation owing to their separate sexes and pollination barriers. Aims: Dodonaea viscosa subsp. angustifolia (Jacq.) (Sapindaceae) is a dioecious and wind-pollinated species that has a long flowering period. This study sought to determine the relationship between its reproductive behaviour and pollen availability during different flowering phases. Methods: Extra-stigmatic pollen germination and reproductive performance during different phases of flowering were investigated and correlated with pistil elongation under natural conditions. Results: The species offers whole stigmatic and stylar surfaces for pollen to land and germinate under natural conditions. During pollen-limiting conditions, the length of the pistil increases significantly to enhance pollen capture. Depending on where on the pistil pollen lands, the timing of pollen tube arrival at the ovary varies. Conclusions: Dodonaea viscosa subsp. angustifolia is the first reported wild species in the Sapindaceae where pistil elongation is regulated by pollination conditions and extra-stigmatic pollen germination ensures reproduction during phases of differing pollen availability. Our results indicated that the flexibility of female function and reproductive behaviour in Dodonaea viscosa subsp. angustifolia adds to the evolutionary possibilities to overcome pollination constraints. Implications: This unique strategy for increasing female fitness through pollen presentation in D. viscosa subsp. angustifolia could be explored in other subspecies of D. viscosa on the Australian subcontinent.