The Galápagos Islands: biogeographic patterns and geology

Abstract

In the traditional biogeographic model, the Galápagos Islands appeared a few million years ago in a sea where no other islands existed and were colonized from areas outside the region. However, recent work has shown that the Galápagos hotspot is 139 million years old (Early Cretaceous), and so groups are likely to have survived at the hotspot by dispersal of populations onto new islands from older ones. This process of metapopulation dynamics means that species can persist indefinitely in an oceanic region, as long as new islands are being produced. Metapopulations can also undergo vicariance into two metapopulations, for example at active island arcs that are rifted by transform faults. We reviewed the geographic relationships of Galápagos groups and found 10 biogeographic patterns that are shared by at least two groups. Each of the patterns coincides spatially with a major tectonic structure; these structures include: the East Pacific Rise; west Pacific and American subduction zones; large igneous plateaus in the Pacific; Alisitos terrane (Baja California), Guerrero terrane (western Mexico); rifting of North and South America; formation of the Caribbean Plateau by the Galápagos hotspot, and its eastward movement; accretion of Galápagos hotspot tracks; Andean uplift; and displacement on the Romeral fault system. All these geological features were active in the Cretaceous, suggesting that geological change at that time caused vicariance in widespread ancestors. The present distributions are explicable if ancestors survived as metapopulations occupying both the Galápagos hotspot and other regions before differentiating, more or less in situ.

Incorporating Topological and Age Uncertainty into Event-Based Biogeography of Sand Spiders Supports Paleo-Islands in Galapagos and Ancient Connections among Neotropical Dry Forests

“…Thus, the paleo-islands were closer to the continent, which could help explaining how a group with poor dispersal capabilities reached a volcanic archipelago. This scenario is similar to the metapopulation vicariance model that has been proposed to explain the presence of ancient, poorly dispersing groups in recent volcanic archipelagos, particularly in the Galapagos [57,58]. It could also explain other instances of clades whose estimated ages are older than the islands they occupy, such as sheet-web weavers in the Juan Fernández Islands [59].…”

“…The Galapagos Islands are volcanic in origin, and while the oldest emerged island is 3-4 million years old [34], there is evidence of submerged paleo-islands to the east [35] and north [36] of the current archipelago. The particular biota of the islands has affinities with those of South America, the Greater Antilles and other Pacific islands [56,57]. It is clear that the only sand spider of the islands, S. utriformis, is of South American origins, as its closest relative lives on the coast of Peru (Figure 2).…”

“…Christie et al [35] suggested that it is very possible that the history of the archipelago could be as old as that of the volcanic hotspot, spanning 80-90 million years, and thus other uncharted paleo-islands might exist. Further evidence for this hypothesis has been recently reviewed by Heads & Grehan [57]. To account for this possibility, we compared a model where dispersal to the Galapagos was only possible in last 15 Myr to an unconstrained model where dispersal could happen at any moment-thus, considering the possibility of even older paleo-islands.…”

Methods in molecular biogeography: The case of New Caledonia

“…The direction that biogeographical research takes in the future will be determined by the methods used. Rejection of the standard ancestral area algorithms in favour of the approach used here has led to new ideas on biogeography in other areas (such as the Galapagos Islands; Heads & Grehan, 2021) and in other groups (such as the pantropical plant family Meliaceae; Heads, 2019b).…”

Biogeographic–tectonic calibration of 14 nodes in a butterfly timetree

“…These eventually collided and fused with north‐western South America or were subducted beneath it (Fig. 18; Heads and Grehan, 2021). For example, Ontong Java Nui formed in the central Pacific near other plateaus that are now accreted to western Colombia and western Ecuador (Chicangana, 2005; Kerr and Tarney, 2005).…”