Príncipe – Hotspot of Endemics in the Gulf of Guinea

1. Introduction: Príncipe – Hotspot of Endemics in the Gulf of Guinea

A. Geographical Location and Volcanic Origin

Príncipe Island, also known as Ilha do Príncipe, is a small volcanic island situated in the Gulf of Guinea in Central Africa. It is one of the two main islands constituting the Democratic Republic of São Tomé and Príncipe (STP). Geographically, Príncipe is located in the equatorial Atlantic and lies approximately 220 km west of the African mainland or about 240 km west of Equatorial Guinea and 255 km northwest of Gabon. The islands are part of the Cameroon Volcanic Line, a chain of volcanic structures. Crucially, Príncipe is an oceanic island that emerged from volcanic activity on the ocean floor and has never been connected to the African continent. The island system is separated from the mainland by deep-sea trenches or ocean depths exceeding 1,800 m or 2,000 m.

B. Geological Significance: The Island as the Oldest Part of the Chain, Formed approximately 31 Million Years Ago

Príncipe holds significant geological importance as it is definitively the geologically oldest of the oceanic islands in the Gulf of Guinea system. Its origin dates back to approximately 31 million years ago (Ma). This age is significantly older than its sister island, São Tomé (estimated at 15 Ma). The extended time (31 Ma) establishes Príncipe as a deep-time evolutionary archive. Príncipe is a heavily eroded volcano, and its geology is split between a relatively flat, low-lying basalt platform in the north and a more rugged, mountainous south dominated by peaks composed of phonolite. The highest point is Pico do Príncipe. Estimates suggest that the island's area in the mid-Oligocene (31 Ma) was about 4,200 km², roughly four times the current combined area of São Tomé and Príncipe.

C. The Consequence of Isolation: Extreme Rates of Endemism, Often Called the "Galápagos of Africa"

The combination of its deep geological age and extreme isolation has resulted in an exceptionally high degree of endemism across the island's biota. This endemic richness causes the archipelago to be frequently referred to as the "African Galápagos". In fact, São Tomé and Príncipe are home to more endemic species in an area eight times smaller than the famous Galápagos archipelago. Príncipe alone harbors over 40 unique animal species. This unique diversity is due to evolutionary specialization characteristic of island biogeography, where successfully colonizing species evolve without continuous continental pressure.

D. Total Island Area (approx. 136–142 km²) and Significance for Global Biodiversity

Príncipe is the smaller of the two main islands, covering an area of approximately 136 km² or 142 km². Despite this small size, it is globally recognized as a biodiversity hotspot. The forests of the STP archipelago are ranked as the second most important of 75 African forests for bird conservation. In recognition of its global importance, the entire island of Príncipe and its surrounding marine environment were designated a UNESCO Biosphere Reserve in 2012. The total area of the reserve is 71,592.5 hectares, and it includes important surrounding islets such as Bom Bom, Boné do Jóquei (Caroço), Mosteiros, Pedra da Galé, and the Tinhosas islands. The forests on Príncipe are also part of the Guinean Forests of West Africa Biodiversity Hotspot.