5 - Origins and evolution of Galapagos endemic vascular plants

Summary

Thirty years ago, Porter (1979) summarised what was then known of the origins and evolution of Galapagos endemic vascular plants. He concluded that 43% of indigenous taxa (231 out of 543 species, subspecies and varieties) were endemic, although this figure included six questionably endemic and 14 questionably distinct taxa plus 13 others known only from the type or not collected for at least 45 years. Removing those led to 186 endemics in a total vascular flora of 498 taxa (37% endemic). This percentage endemism is higher than some published estimates, partly because Porter (1976, 1979, 1983) excluded from the indigenous flora 47 species that he regarded as introduced by people, but which have been treated as native by others (e.g. Lawesson et al., 1987). Porter (1979) recognised 192 naturalised introduced taxa (including the 47 that were treated as native by Lawesson et al., 1987). Porter (1979) recognised seven endemic genera, and radiations that had produced at least three endemic taxa in ‘19’ genera (actually 21 according to his systematic list, including two about which some doubt was expressed), plus ‘10’ more genera (12 in his systematic list including two less certain ones) which had produced two endemics by radiation. He suggested that birds had played the most important role in dispersing plants to the islands.