ggplot expression not rendering correctly

Question

As seen in the image below, some characters in the axes labels are not rendered correctly. Spaces show up as boxes. This image was exported as a png. Seems to work fine when exporting to a pdf.

Running in a conda env. Perhaps something graphic related is missing?

library(ggplot2)

g <- ggplot(iris,aes(Sepal.Width,Petal.Width))+
  geom_point()+
  labs(x=expression(Mean~Log[2]~Fold~change),y=expression(-Log[10]~Adj~P~value))

ggsave("test.png",g)
#> Saving 7 x 5 in image

^{Created on 2021-08-30 by the reprex package (v2.0.1)}

Session info

sessioninfo::session_info()
#> ─ Session info ───────────────────────────────────────────────────────────────
#>  setting  value                       
#>  version  R version 4.1.0 (2021-05-18)
#>  os       Ubuntu 20.04.3 LTS          
#>  system   x86_64, linux-gnu           
#>  ui       X11                         
#>  language en_GB:en                    
#>  collate  en_GB.UTF-8                 
#>  ctype    en_GB.UTF-8                 
#>  tz       Europe/Stockholm            
#>  date     2021-08-30                  
#> 
#> ─ Packages ───────────────────────────────────────────────────────────────────
#>  package     * version date       lib source        
#>  ggplot2     * 3.3.5   2021-06-25 [1] CRAN (R 4.1.0)
#> 
#> [1] /home/user/miniconda3/envs/r-4.1/lib/R/library

Answer 1

I add the same issue than you on Mac OS and managed to solve it with 2 modifications : replace ~ by %~% and add device = png in the ggsave function

g <- ggplot(iris,aes(Sepal.Width,Petal.Width))+
  geom_point()+
  labs(x=expression(Mean%~%Log[2]%~%Fold%~%change),y=expression(-Log[10]%~%Adj%~%P%~%value))

ggsave("test.png",g,device=png)

I hope this would work for you