Host identity and phylogeny shape the foliar endophytic fungal assemblages of Ficus

Abstract

Foliar endophytic fungi (FEF) are diverse and ubiquitously associated with photosynthetic land plants. However, processes shaping FEF assemblages remain poorly understood. Previous studies have indicated that host identity and host habitat are contributing factors, but these factors are often difficult to disentangle. In this study, we studied FEF assemblages from plants grown in a botanical garden, enabling us to minimize the variation in abiotic environmental conditions and fungal dispersal capacity. FEF assemblages from 46 Ficus species were sequenced using next-generation methods, and the results indicated that closely related host species had clearly differentiated FEF assemblages. Furthermore, host phylogenetic proximity was significantly correlated with the similarity of their FEF assemblages. In the canonical correspondence analysis, eleven leaf traits explained 32.9% of the total variation in FEF assemblages, whereas six traits (specific leaf area, leaf N content, leaf pH, toughness, latex alkaloid content, and latex volume per leaf area) were significant in the first two dimensions of ordination space. In the multiple regression on distance matrix analysis, 21.0% of the total variance in FEF assemblage was explained by both host phylogeny and leaf traits while phylogeny alone explained 7.9% of the variance. Thus, our findings suggest that both evolutionary and ecological processes are involved in shaping FEF assemblages.

Keywords: Ficus; foliar endophytic fungi; leaf functional traits; phylogenetic signal.

Figure 1

Two‐dimensional DCA ordination showing the influence of host species on the structure of FEF assemblages in phylogenetically closely related species (a: subsection Conosycea; b: subsection Urostigma; c: F. auriculata species complex). Abbreviations are the first four letters of specific epithets of host species (Table S1). Ellipses indicate the location and dispersion in ordination space for each host species represented by more than three individuals (confidence level = 0.90). Points represent host individuals

Figure 2

Results of hierarchical clustering showed that most or all individuals of a given species frequently share similar FEF assemblages. Species represented by one individual are shown in gray, species with two individuals are shown in black, and species represented by more than two individuals are each given unique colors. Six subgenera are marked by segments of different colors on the rim of the circle. The numbers after the abbreviations denote the different individuals for a given species

Figure 3

Positive correlation between phylogenetic distance and dissimilarity between the FEF assemblages of 46 Ficus species in common‐garden conditions (Confidence level = 0.95)

Figure 4

Two‐dimensional CCA ordination, showing that leaf traits contribute to explaining the dissimilarity among FEF assemblages of the 23 Ficus species represented by three individuals (a: ordination space of CCA 1 and CCA2; b: CCA 1 and CCA3, leaf carbon content contributed more to CCA3 than to other axes). Variables with significant effects (p < .05 by “envfit” function in vegan) are colored red. Each species are given unique colors; points refer to each of the 69 individuals. Latexvolumesp refers to latex volume per leaf area