Reproductive ecology of the dioecious endemic Erodium sibthorpianum subsp. sibthorpianum in Türkiye

Abstract Erodium sibthorpianum subsp. sibthorpianum (Geraniaceae) is an endemic taxon restricted to western Türkiye. Understanding its reproductive traits and the factors governing reproductive success is essential for elucidating its reproductive ecology. The pollen–ovule ratio was calculated as 3043, which falls within the expected range for dioecious species. Pollination is mediated by a diverse assemblage of insects, predominantly Diptera with licking–sucking mouthparts. Pollen viability and stigma receptivity were highly synchronized during anthesis, both peaking on the day of flower opening and declining gradually thereafter. Seed viability averaged 91%. Seeds collected in the same year exhibited high germination success (75–90%) at 10–20 °C, whereas seeds stored for approximately four years showed markedly reduced germination (10–36%) across the same temperature range. The capacity for seed formation per plant used as an indicator of population-level reproductive success was 33.3% in 2019 and 15.1% in 2022. Overall, the findings highlight several key reproductive characteristics of the subspecies and suggest that pollination may be a significant factor influencing reproductive success. Environmental conditions at the microhabitat level or annual climate variability may also have affected the decline. However, additional evidence is needed to clarify the nature and strength of this relationship.