While recent studies on Spanish have shown that some causal connectives specialize in expressing certain types of causal relations, others have revealed that causal relations may be signaled by a variety of linguistic devices. Given that we were interested not only in specificity and variety, but also in the functionality of causal connective expressions, our objective in the present study was threefold. First, to identify the variety of connective expressions (connectives and cue phrases) used to signal causal relations in Spanish. Second, to determine whether a relationship of specificity exists between connective expressions and particular types of causal relations. Third, to describe the functionality of those connective expressions. We analyzed a corpus of 2,514 causal coherence relations previously annotated and identified in a corpus of academic texts. 41 different linguistic devices used to signal causal relations were identified. These devices were grouped into two main functional classes: connectives and cue phrases. Regarding the functionality of the signals, we found that 8 of the most frequent connective expressions were used to signal different relations. As for specificity, in terms of syntactic categories, it was observed that various conjunctions and conjunctive adverbs specialize in signaling specific relations.