High endemism of mosquitoes on São Tomé and Príncipe Islands: evaluating the general dynamic model in a worldwide island comparison

Abstract

The archipelago of São Tomé and Príncipe is a major centre of endemism for vertebrates but, to date, arthropods remain poorly studied, with the exception of mosquitoes due to their medical and economic relevance. Previous studies, over 20 years old, recorded 26 species of mosquitoes for São Tomé and 14 for Príncipe, of which six and two were endemic to each island respectively. We collected mosquito larvae and adults on both islands and found three species as a first record, putting the number of mosquito species collected at least once on São Tomé at 29 and 15 for Príncipe. We compared the mosquito richness on São Tomé and Príncipe islands to 71 other oceanic islands represented within 20 archipelagoes worldwide. We used the general dynamic model of oceanic island biogeography and the associated ATT2 (for Area+Time+Time2) model to explain two different metrics: (i) the richness of the single‐island endemics and (ii) the richness of archipelago endemics. We also included other island characteristics in our model, such as isolation and latitude. Our data compilation and comparative analyses revealed an overall low richness of endemic mosquitoes on islands, with the highest number of single‐island endemics found on São Tomé Island. As predicted, we found a positive relationship between our two richness metrics and the general dynamic model ATT2, although the model with the area (A) alone also explained endemic richness. Isolation was also predictor of mosquito diversification.

The origin of island populations of the African malaria mosquito, Anopheles coluzzii

“…São Tomé and Príncipe islands present an inverted pattern i.e. high endemism, that includes the mosquito fauna 49 , 52 , and low species richness. In STP only two species of anopheline mosquitoes have been reported, A. coluzzii and A. coustani 19 , 53 , whilst on Bioko there are at least five: A. gambiae , A. coluzzii , A. melas , A. funestus , and A. smithii 54 , 55 .…”

Biogeography and Evolution in the Oceanic Islands of the Gulf of Guinea

“…(1) high levels of endemism; (2) wide representation across the tree of life; (3) in situ radiations are rare and result in few species; and (4) the biological communities of each island are largely unique, with few endemics shared between them. With the exception of the Odonata (dragonflies and damselflies), which have relatively low species diversity in the Gulf of Guinea and just one endemic species (Dijkstra and Tate 2022), the three islands have some of the highest concentrations of endemic species in the world for several groups, including mosquitoes (Loiseau et al 2019), amphibians (Bell et al 2022), terrestrial reptiles (Ceríaco et al 2022b), and birds (Melo et al 2022). These patterns are particularly remarkable in relation to the small size of these islands (just over 1000 km 2 combined) and are likely a consequence of their favorable geographic setting.…”

Transcontinental dispersal of Anopheles gambiae occurred from West African origin via serial founder events

“…A number of individual studies of island populations of A. gambiae have been undertaken, most recently analysis of several small islands in Lake Victoria, eastern Africa, indicating genetic isolation of these island populations 34 . However, these islands are located <50 km from the mainland and there is a known negative correlation between species diversity and distance to mainland 35 including a study specifically on mosquitoes 36 , underlining the importance of remoteness for isolation.…”