Vim not recognizing markdown and tex files

Question

Here is a sample of my .vimrc, that doesn't do a thing (the autocmd does not work) when I open a .md or .tex file, but works fine for .py files:

augroup filetype_python
  autocmd FileType python nnoremap <buffer> <localleader>c I#<esc>
  autocmd FileType python set nu
  autocmd FileType python :iabbrev <buffer> iff if:<left>
  autocmd FileType python :iabbrev <buffer> forr for:<left>
  autocmd FileType python :iabbrev <buffer> while while:<left>
  autocmd BufWritePre,BufRead *.py :normal gg=G
augroup END

augroup filetype_tex
  autocmd FileType tex set nu
augroup END

augroup filetype_markdown
  autocmd FileType markdown onoremap i= :<c-u>execute "normal! ?^==\\+$\r:nohlsearch\rkvg_"<cr>
  autocmd FileType markdown onoremap i- :<c-u>execute "normal! ?^--\\+$\r:nohlsearch\rkvg_"<cr>
augroup END

As if Vim didn't know about markdown and tex (but it's supposed to, I checked the list of all known FileTypes and they were there)... Any ideas ?

Thanks in advance !