Galapagos is often called the Last Paradise, but in fact it is a
suffering paradise, with hundreds or thousands of introduced species
sometimes replacing the native fauna and flora. Efforts to safe species
and ecosystems compete with economic interests, and for many taxa our
knowledge about native and introduced species continues to be
rudimentary. Pholcidae spiders are known for their high number of
synanthropic species that have followed humans around the world, but
only a single species had previously been recorded from Galapagos. Our
aim was to document introduced pholcid species and to estimate their
potential impact on the native pholcid species.
At least three introduced species were found to be abundant on the two visited islands (Santa Cruz, Isabela): Modisimus culicinus, Smeringopus pallidus, and Physocyclus globosus. On Santa Cruz, we found strong evidence that the African S. pallidus is replacing or has replaced the native cave-dwelling Aymaria jarmila. On the same island, Modisimus culicinus seems to compete with the native Galapa bella, but in this case the impact seems still restricted to the area around the largest town, Puerto Ayora.
Only two species of Metagonia had previously been known from Galapagos: M. bellavista (upper left) and M. reederi (upper right). Since both are blind troglobites, they had been thought to be relicts, i.e. with no epigean relatives on Galapagos. We were surprised to find epigean representatives of Metagonia fairly abundant in several places, with different new species on Santa Cruz (lower left) and Isabela (lower right).
In two caves on Santa Cruz we found the so far smallest known pholcid spider, a new species of Metagonia. Its body length is 0.75 mm, it is entirely blind and pale whitish except for the sclerotized male pedipalps.
I The endemic genus Galapa is apparently restricted to arid habitats like the one shown here near Garrapatero beach on Santa Cruz. This tiny spider occupies the same microhabitat as the introduced Modisimus culicinus, and it remains to be seen if the latter will eventually occupy the entire island and replace Galapa, as it already does around Puerto Ayora.
I thank Andrea Acurio and Marta Romoleroux (Charles Darwin Research Station) for their help with preparations, permits, and logistics.