I want to create an svg image of a map that has no stoke and the background is filled with a dotted pattern with transparent background, so the whole image is transparent apart from the dots that fill the map. When I save my file as svg the dots are not showing up. If I save it as png, it works just fine. I have no other layers or shapes in the file. Any idea why is this happening?
It sounds like you are using a pattern fill within Illustrator. Try expanding the fill before saving or exporting the item as SVG.
You might need to ungroup the resulting items as many dotted patterns are made up of the dots and the white or transparent negative space around them - if so, delete this white/transparent space as it can do odd things to the resulting SVG file.
If the pattern is bitmap rather than vector, then things become more complex. It's still possible, as SVG does support embedded bitmaps, but things are much easier to deal with if your pattern is a vector one.