Genome-wide sequence data show no evidence of admixture and introgression among pollinator wasps associated with a community of Panamanian strangler figs

Abstract

Interactions between plants and their animal pollinators can shape processes of divergence and gene flow within associated lineages. For example, in the obligate mutualism between figs (Ficus) and fig pollinator wasps (family Agaonidae), each wasp species typically pollinates a single fig species, potentially reinforcing reproductive isolation among different wasp species. Multiple pollinator species, however, can sometimes reproduce in the same host fig species, potentially enabling hybridization and introgression between wasp species. In a community of Panamanian strangler figs (section Americana), we use genome-wide ultraconserved element (UCE) loci to estimate phylogenetic relationships and test for hybridization and gene flow among 19 pollinator species associated with 16 host fig species. Previous studies showing ongoing pollinator sharing and a history of pollinator host switching are consistent with documented genetic admixture in their host figs. Here we investigate if host sharing and a dynamic evolutionary history including host switching has also resulted in hybridization and gene flow between pollinator species. Phylogenetic analyses recover strong support for well-delimited wasp species coupled with high interspecific divergence. There is no evidence for ongoing hybridization or introgression, even among pairs of pollinator species currently reproducing within the same host. In contrast to work suggesting admixture among Panamanian host figs, we conclude hybridization and interspecific gene flow have not been important processes shaping the evolutionary history of their pollinating wasps.

Rising temperatures threaten pollinators of fig trees—Keystone resources of tropical forests

“…Specifically, we studied Pegoscapus tonduzi ( Ficus citrifolia ), P. hoffmeyeri A and B ( F. obtusifolia ), P. gemellus A and B ( F. popenoei ), Tetrapus costaricanus ( F. insipida ), and T. americanus ( F. maxima ) (Molbo et al, 2004 ; Wiebes, 1995 ). F. obtusifolia and F. popenoei are each pollinated by two cryptic fig wasp species that cannot be distinguished morphologically (Molbo et al, 2004 ; Satler et al, 2020 ). For each fig species, one of the cryptic pollinator species is much more common than the other, and the wasps are sister species ( P. hoffmeyeri A and B) or closely related ( P. gemellus A and B) (Molbo et al, 2004 ; Satler et al, 2020 ) so in this study, we did not try to separate them.…”

“…F. obtusifolia and F. popenoei are each pollinated by two cryptic fig wasp species that cannot be distinguished morphologically (Molbo et al, 2004 ; Satler et al, 2020 ). For each fig species, one of the cryptic pollinator species is much more common than the other, and the wasps are sister species ( P. hoffmeyeri A and B) or closely related ( P. gemellus A and B) (Molbo et al, 2004 ; Satler et al, 2020 ) so in this study, we did not try to separate them. Non‐pollinating parasitic wasps were found on all fig species but only in two fig species were there a sufficient number of parasitic wasps in our samples to include them in the statistical analyses; F. popenoei : Heterandrium spp.…”

“…Ficus obtusifolia (Molbo et al, 2004;Satler et al, 2020;Wiebes, 1995) Pegoscapus hoffmeyeri A Pegoscapus hoffmeyeri B Idarnes Ficus popenoei (Molbo et al, 2004;Satler et al, 2020;Wiebes, 1995) Pegoscapus gemellus A Pegoscapus gemellus B…”

“…Using climate chambers, we performed survival experiments on wasp species from both existing Neotropical fig pollinator genera, Pegoscapus and Tetrapus . Our tested wasp species are species‐specific pollinators of five common Panamanian Ficus species (but see Machado et al, 2005 ; Satler et al, 2020 , regarding rare host sharing). We tested temperatures that ranged from the local current mean daytime temperatures to the local predicted daytime temperatures by the end of the 21st century (1–4°C higher depending on the different climate scenarios; IPCC, 2021 ) and beyond.…”