The loss of dispersal on islands hypothesis revisited: Implementing phylogeography to investigate evolution of dispersal traits in Periploca (Apocynaceae)

Abstract

Aim: The loss of dispersal on islands hypothesis (LDIH) posits that wind-dispersed plants should exhibit reduced dispersal potential, particularly if island populations are old. In this study, we tested this hypothesis using a detailed phylogeographical framework across different geographical scales. Location: Mainland and island areas of the Atlantic and Mediterranean regions, including Macaronesia (Canary Islands and Cape Verde) and Mediterranean islands in the strait of Sicily. Methods: Forty-five populations of Periploca laevigata, a wind-dispersed shrub, were sampled. Plastid and nuclear microsatellite data were used to reconstruct spatiotemporal patterns of island colonization, and estimates of seed terminal velocity used as a surrogate for dispersal ability under both field and common garden conditions.Results: Our findings did not provide evidence of loss of dispersability in any island lineage. In all of the regions considered, dispersal ability was similar on island and mainland populations, or higher on islands. Contrary to LDIH expectations, lineages inferred as the oldest (western Canaries and Cape Verde) converged towards the most dispersive seed phenotype. This pattern was supported by data obtained under common garden conditions. Within the western Canarian lineage, successful dispersal was shown to be very rare among islands and extensive within islands, but dispersability did not vary significantly from older to more recent sublineages. Considering all the study islands, we found a strong, positive correlation between dispersal ability and estimates of within-island habitat availability. Main conclusions:This study suggests that dispersal ability can be favoured on islands, possibly because traits enhancing wind dispersal are positively selected when habitat availability is high. Our results challenge broad generalizations of the LDIH, but we discuss how overlooking species 0 phylogeographical history may give rise to misleading conclusions. K E Y W O R D S anemochory, dispersal ability, island colonization, Macaronesia, parallel evolution, seed dispersal

Disentangling the processes driving tree community assembly in a tropical biodiversity hotspot (New Caledonia)

“…A more recent study on animal species native to New Caledonia showed that there is a higher proportion of species with restricted ranges (≤5.2 km 2 ) in non‐endemic species (22%) than in endemic species (12%), suggesting that environmental dissimilarity may play an important role in their distribution (Caesar, Grandcolas, & Pellens, ). The role of environmental filtering in shaping island communities is gaining increasing support in the literature, while recent biogeographical and phylogenetical analyses in the Galápagos and Macaronesia have provided increasing evidence against the hypothesis of lesser dispersal ability in islands (Carvajal‐Endara, Hendry, Hendry, Emery, & Davies, ; García‐Verdugo, Mairal, Monroy, Sajeva, & Caujapé‐Castells, ).…”

rWind: download, edit and include wind data in ecological and evolutionary analysis

“…Specifically, we compare the genetic structure of northwestern African and Macaronesian populations of P. laevigata obtained by García-Verdugo et al (2017) with wind connectivity between those areas computed with rWind. 2A, B, C in García-Verdugo et al 2017). 2A, B, C in García-Verdugo et al 2017).…”

“…In their research, García-Verdugo et al detected a close genetic relation between northwestern African populations, eastern Canary Islands populations and Cape Verde populations ( Fig. In this example we compute wind connectivity from locations sampled on the African mainland by García-Verdugo et al (2017) with their sampled islands of Fuerteventura (eastern Canary Islands), Gran Canaria and Tenerife (central Canary Islands), La Palma (western Canary Islands), and Santo Antão and Fogo (Cape Verde). In this example we compute wind connectivity from locations sampled on the African mainland by García-Verdugo et al (2017) with their sampled islands of Fuerteventura (eastern Canary Islands), Gran Canaria and Tenerife (central Canary Islands), La Palma (western Canary Islands), and Santo Antão and Fogo (Cape Verde).…”

“…2A, B, C in García-Verdugo et al 2017). Figure 3 shows a wind-connectivity graph from the mainland Africa locations (AGA, TAN, WSAH_A, WSAH_B, see Appendix S1 in García-Verdugo et al (2017)) to all the island locations. A complete script with analyses and plots created for this example is included in the Supplementary material Appendix 1-3.…”

“…In this example we compute wind connectivity from locations sampled on the African mainland by García-Verdugo et al (2017) with their sampled islands of Fuerteventura (eastern Canary Islands), Gran Canaria and Tenerife (central Canary Islands), La Palma (western Canary Islands), and Santo Antão and Fogo (Cape Verde). 2A, B, C in García-Verdugo et al (2017), suggesting wind connection may play a role in genetic structuring. Figure 3 shows a wind-connectivity graph from the mainland Africa locations (AGA, TAN, WSAH_A, WSAH_B, see Appendix S1 in García-Verdugo et al (2017)) to all the island locations.…”