Additional meanings of 也 I am reading this example:

听众至少也有五千人。
The audience was not less than five thousand.

Dictionary gives only "also, too" meanings for 也 and it doesn't seem to fit in this example. So what is the role of this word here?
It is used to emphasize the verb 有.

We can omit 也 and show the same meaning.
听众至少(也)有五千人。

也 [副] 3
表示强调。如：“一点也不”、“再也不敢”、“连爸妈也乐得开怀大笑。” 

也 yě 〈副〉(5)
 表示强调 [even]。如: 也须 (也应当; 也应该); 连老人也干活