Flora Diversity and Conservation Status Along an Altitudinal Gradient in the District of Sumbilca, Huaral, Peru

The tropical Andes are a global biodiversity hotspot, yet extensive areas of the Peruvian western slope, such as the district of Sumbilca (Huaral province, Lima), remain floristically understudied despite mounting pressure from agricultural expansion, overgrazing, and seasonal burning. This study aimed to determine floristic diversity and assess the conservation status of vascular plants along a 2400–4000 m altitudinal gradient in Sumbilca. Between July 2024 and June 2025, qualitative walking surveys were conducted across four altitudinal zones (Z1–Z4), and species richness, family composition, floristic similarity (Jaccard dissimilarity, hierarchical clustering), and conservation status (IUCN Red List and Peruvian Supreme Decree N.° 043-2006-AG) were analyzed. A total of 202 species, 140 genera, and 62 families were recorded, dominated by Asteraceae, Poaceae, Solanaceae, and Fabaceae, with herbs as the predominant growth habit (66.3%). Species richness peaked in Z2–Z3 (85 and 84 species) and declined sharply in Z4 (38 species), which was also the most floristically distinct zone. Twenty-one endemic species and 42 species with recognized conservation status were documented, including five nationally threatened taxa, along with several new records for Huaral province. These findings indicate that Sumbilca harbors considerable, previously undocumented floristic and conservation value, and provide an essential baseline for future ecological monitoring and management along the western Andean slope.