Spatial Scales of Genetic Structure in Free-Standing and Strangler Figs (Ficus, Moraceae) Inhabiting Neotropical Forests

Abstract

Wind-borne pollinating wasps (Agaonidae) can transport fig (Ficus sp., Moraceae) pollen over enormous distances (> 100 km). Because of their extensive breeding areas, Neotropical figs are expected to exhibit weak patterns of genetic structure at local and regional scales. We evaluated genetic structure at the regional to continental scale (Panama, Costa Rica, and Peru) for the free-standing fig species Ficus insipida. Genetic differentiation was detected only at distances > 300 km (Jost´s Dest = 0.68 ± 0.07 & FST = 0.30 ± 0.03 between Mesoamerican and Amazonian sites) and evidence for phylogeographic structure (R ST>>permuted R ST) was only significant in comparisons between Central and South America. Further, we assessed local scale spatial genetic structure (SGS, d ≤ 8 km) in Panama and developed an agent-based model parameterized with data from F. insipida to estimate minimum pollination distances, which determine the contribution of pollen dispersal on SGS. The local scale data for F. insipida was compared to SGS data collected for an additional free-standing fig, F. yoponensis (subgenus Pharmacosycea), and two species of strangler figs, F. citrifolia and F. obtusifolia (subgenus Urostigma) sampled in Panama. All four species displayed significant SGS (mean Sp = 0.014 ± 0.012). Model simulations indicated that most pollination events likely occur at distances > > 1 km, largely ruling out spatially limited pollen dispersal as the determinant of SGS in F. insipida and, by extension, the other fig species. Our results are consistent with the view that Ficus develops fine-scale SGS primarily as a result of localized seed dispersal and/or clumped seedling establishment despite extensive long-distance pollen dispersal. We discuss several ecological and life history factors that could have species- or subgenus-specific impacts on the genetic structure of Neotropical figs.

Lack of genetic isolation by distance, similar genetic structuring but different demographic histories in a fig‐pollinating wasp mutualism

“…Indeed, Hainan belongs to the 'marginal tropical zone', a climatic zone of very limited spread in continental China (Dai et al 2015). In high dispersal species like Ficus, geographic barriers may be of major importance in allowing some, limited, genetic differentiation among populations as suggested for F. insipida between Costa Rica, Panama and Peru (Heer et al 2015). Such differentiation, if supplemented by some isolation by adaptation, could facilitate diversification.…”

Effects of zoochory on the spatial genetic structure of plant populations

“…The list of additional factors that might potentially influence SGS in the surveyed studies, but were present in too few studies to include in the analysis, included fruit availability and plant distribution (Bizoux et al., ; Trapnell et al., ), management situation of plant populations (Lind‐Riehl & Gailing, ), habitat fragmentation (Vieira, Fajardo, de Souza, Reis, & de Carvalho, ; Wang, Compton, & Chen, ), urbanization level of study site (Wang et al., ), specific microhabitat requirements limiting germination success (Chung et al., ; Heer et al., ) and plant life history, such as masting events or high fruiting yields (Lind‐Riehl & Gailing, ; Vieira et al., ), clonality (Dodd, Mayer, Nettel, & Afzal‐Rafii, ) or plant life form (Heer et al., ). Many of these factors influence directly or indirectly foraging behaviour of the seed dispersal vectors.…”

Genetic structure of the Canarian palm tree (Phoenix canariensis) at the island scale: does the ‘island within islands’ concept apply to species with high colonisation ability?

“…; Heer et al . ). Considering the wide ecological range of P. canariensis , the effect of historical disturbance on SGS patterns will depend on the extent of the perturbation and the particular resilience of each population, i.e .…”