Population Size and Spatial Patterns of the Endangered Tree Gigasiphon macrosiphon in Tanzania

ABSTRACT Gigasiphon macrosiphon (Harms) Brenan is a rare and endangered tree endemic to the coastal forests of Kenya and Tanzania. Yet, its population status and spatial ecology remain poorly documented, particularly in Tanzania. We quantified population size, growth‐stage composition, and spatial patterns of G. macrosiphon in two forest reserves in southeastern Tanzania: Kwediboma Forest Reserve and Rondo Nature Forest Reserve. Individuals across all growth stages were systematically surveyed, with diameter measurements used to assess size‐class structure and regeneration status, and spatial mapping used to evaluate patterns of aggregation. Rondo supported a substantially larger and more demographically continuous population, with abundant early growth stages indicating ongoing recruitment. In contrast, Kwediboma was dominated by intermediate and mature individuals, with limited representation of germinants and seedlings, suggesting constrained or episodic regeneration. Spatial analyses revealed strong clustering consistent with localized recruitment near parent trees, with broader spatial distribution and more extensive recruitment at Rondo than at Kwediboma. Together, these patterns indicate that G. macrosiphon populations are shaped by site‐specific habitat conditions and regeneration processes, underscoring the need for targeted conservation strategies to maintain recruitment and long‐term population persistence.