Rhyncogonus and Laparocerus (Coleoptera, Curculionidae, Entiminae), a parallel case of success in island evolution. Report of a study trip to Moorea, Tahiti and Rurutu.
2007; Volume: 35; Issue: Vieraea 35 Linguagem: Inglês
10.31939/vieraea.2007.35.07
ISSN0210-945X
Autores Tópico(s)Plant and animal studies
ResumoThis is a report of a study trip to the islands of Moorea, Tahiti and Rurutu to compare the Polynesian weevil genus Rhyncogonus with the Macaronesian genus Laparocerus, in the Atlantic. Both genera have radiated in these archipelagos, and the species are flightless and mostly single-island endemics. The general geological and environmental conditions in both archipelagos are briefly discussed and snapshots of both groups of weevils are provided. Common features are highlighted (wingless, endemicity, etc.) as well as some differences observed (nocturnal versus diurnal activity, feeding amplitude, abundance, size, morphological diversity, etc.). Despite the richer ecological diversity of Macaronesia and the lack of competition in Polynesia, Rhyncogonus and Laparocerus can be considered as ecologically homologous. Both genera have succeeded in colonising their archipelagos, followed by intensive radiation. The concentration of endemics per island is higher in Polynesia congruent with its greater isolation. The highest species density in the Canaries is found in La Gomera, with 0.8 sp/km², while in Rurutu it is 0.12 sp/km². The record species density is achieved in Rhyncogonus on Rapa-Iti with 0.27 sp/km², this figure is further surpassed by the cryptorhynchine genus Miocalles with 1.67 sp/ km² on that same island. A high number of closely related but welldifferentiated species on a small isolated island could be explained as the product of repeated colonising events from a single source lineage (therefore, the monophyly), punctuated in time (punctuated allopatric speciation).
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