How to merge shapes to one object

Petra,

An afterthought; if you merely wish to avoid its filling the expanded Layer, you can just click the down arrow to collapse the GREEN LEAVES Group.

Petra,

Always keep the original artwork and work on a copy when you make irreversible changes, such as rasterizing, which will limit the artwork to a specific number of pixels, each pixel haing one colour.

I would encourage anyone who wants to 'merge' their artwork into one object to ask themselves why they think they need to first.

in this condition it's impossible. You can either have the united shape with the same color/gradient or have many different pieces with different colors.

If you want to have fewer amount of objects and keep the texture, I could suggest this way:

1. export the current artwork as a raster image with the needed resolution;

2. unite all the shapes as Ton recommended (use Pathfinder > Unite);

3. import the image and create a clipping mask: put the united shape above the image, select both and click Ctrl(Cmd)+7.

Another way is to create a Gradient Mesh for the united shape, but it's a very long and complicated work.

If you want a single color, choose Unite in the Pathfinder panel.