Cyto-nuclear discordance in the phylogeny of Ficus section Galoglychia and host shifts in plant-pollinator associations

Abstract

Background: Hybridization events are relatively common in vascular plants. However, the frequency of these events is unevenly distributed across the plant phylogeny. Plant families in which individual species are pollinated by specific pollinator species are predicted to be less prone to hybridization than other families. However, exceptions may occur within these families, when pollinators shift host-plant species. Indeed, host shifts are expected to increase the rate of hybridization events. Pollinators of Ficus section Galoglychia are suspected to have changed host repeatedly, based on several cases of incongruence between plant phylogeny and taxonomy, and insect phylogeny and taxonomy. We tracked cyto-nuclear discordance across section Galoglychia as evidence for hybridization. To achieve a proper global view, we first clarified the monophyly of section Galoglychia as it had been questioned by recent phylogenetic studies. Moreover, we investigated if fig size could be a factor facilitating host shifts.

Codivergence and multiple host species use by fig wasp populations of the Ficus pollination mutualism

“…Previous work [8,13] has shown evidence of both lineage duplication and host switching while more recent studies have debated the role extinction and duplication play in explaining phylogenetic incongruence [30,38]. The results presented in this study do not refute any of these arguments, especially as extinction scenarios are difficult to substantiate.…”

“…However, the phylogenetic discordance reported here might also be a function of the dissimilar taxonomic scales used to test associations between wasps and hosts. For instance, breakdown in phylogenetic concordance patterns has been argued to be partly the result of genetic introgression and hybridization across different fig species [8,38,40]. The Ficus phylogeny (Additional file 2) considered only species and not intraspecific variation.…”

The Complete Chloroplast Genome of Banana (Musa acuminata, Zingiberales): Insight into Plastid Monocotyledon Evolution

“…Similar incongruence between analyses of single-copy nuclear genes and the chloroplast genes has been observed in the phylogenetic placement of the Malpighiales within the Rosids [39]. These incongruences may be caused by incomplete lineage sorting [40], long-branch attraction phenomenon [41], [42] or chloroplast introgressions between Musaceae and Poales ancestors (see [43] for example). Additional taxa sampling and coalescence-based analyses will be required to resolve this conflict.…”

Pollinator sharing and gene flow among closely related sympatric dioecious fig taxa

“…Figs and their pollinating fig wasps perhaps represent an extreme case of an obligate pollination system in plant -insect coevolution [26]. However, the species-specific pollination relationship has been repeatedly challenged [17,19,29,32]. Here, we (a) Inter-taxa pollinator sharing of figs…”