Pollinating fig waSPS: genetic consequences of island recolonization

Abstract

The levels of genetic diversity and gene flow may influence the long‐term persistence of populations. Using microsatellite markers, we investigated genetic diversity and genetic differentiation in island (Krakatau archipelago, Indonesia) and mainland (Java and Sumatra, Indonesia) populations of Liporrhopalum tentacularis and Ceratosolen bisulcatus, the fig wasp pollinators of two dioecious Ficus (fig tree) species. Genetic diversity in Krakatau archipelago populations was similar to that found on the mainland. Population differentiation between mainland coastal sites and the Krakatau islands was weak in both wasp species, indicating that the intervening 40 km across open sea may not be a barrier for wasp gene flow (dispersal) and colonization of the islands. Surprisingly, mainland populations of the fig waSPS may be more genetically isolated than the islands, as gene flow between populations on the Javan mainland differed between the two wasp species. Contrasting growth forms and relative ‘immunity’ to the effects of deforestation in their host fig trees may account for these differences.

Wind-borne insects mediate directional pollen transfer between desert fig trees 160 kilometers apart

“…crops (33, 34). Pollen dispersal ranges of 1 to 2 km have been inferred for the dioecious F. pumila in China (35), but genetic studies of two pollinators of dioecious fig trees from Indonesia nonetheless found low levels of population subdivision between mainland and island populations over 40 km apart (15), suggesting that the nature of the breeding system is a weak predictor of gene-flow distances in fig trees. How does C. arabicus manage to pollinate F. sycomorus trees over 100 km apart? The slow flight speed of fig wasps (36) precludes active, directed flight in the time available during a 48-h adult lifespan.…”

“…Pollen dispersal distances for some species have been found to range from hundreds of meters (5)(6)(7)(8)(9)(10)(11) to kilometers (12,13). Long-distance pollen flow between fig trees (Ficus spp., Moraceae) is particularly well documented (14,15). Each of the 800 or so species of fig tree is pollinated exclusively by one or a few host-specific fig wasps (Agaonidae) (16) .…”

“…Fig wasps are small, delicate, weakflying, and short-lived insects (17) that use the wind to carry them between fig trees in open woodland (18) or in rainforests, where many species are transported by the fast-flowing air found above the general canopy (19,20). Fig trees and their wasps are also effective colonizers of islands, and low levels of genetic differentiation at microsatellite loci between mainland and island populations suggest gene flow can occur over distances of tens of kilometers (15,21). Nason et al (14) were the first to use molecular approaches to detect long-distance dispersal of fig wasps.…”

Movements of genes between populations: are pollinators more effective at transferring their own or plant genetic markers?

“…Each fig species is exclusively pollinated by one or a small number of species of host-plant-specific fig wasps (Agaonidae) that enter the trees' globular inflorescences (figs) in order to lay their eggs [23]. Pollinating fig wasps are short-lived, weak-flying insects, but paternity analyses and population structuring of their host populations suggest that whereas some species disperse locally [24], others disperse across much longer distances [8,13,25], initially using fast-flowing air to transport them passively in whichever direction it is moving [26,27].…”

Evolutionary Ecology of Figs and Their Associates: Recent Progress and Outstanding Puzzles

“…Different host species appear to produce different blends that the associated wasps recognize. Genetic work has shown that the pollen-bearing wasps routinely disperse many kilometers, with the result that the areas covered by effective breeding populations of figs are often on the order of a hundred or more square kilometers, an order of magnitude larger than that documented for any other plant species (Nason et al 1998; also see Compton 1990see Compton , 1993Harrison & Rasplus 2006;Ware & Compton 1992;Zavodna et al 2005). Interestingly, high ratios of anthers to female flowers and produce much more pollen per syconium than do actively pollinated figs, and their mature anthers tend to dehisce naturally, facilitating the passive collection of pollen by their pollinators (pollen adheres to various parts of the body surface) (Jousselin et al 2003a.…”