How many letters does the top answer for “arising or occurring within a species; involving the members of one species” have?

The most common answer is intraspecies (12 letters).

Crossword clue: arising or occurring within a species; involving the members of one species

2 answers found in Letterora's clue database (Wikidata facts, Open Trivia DB, WordNet and Webster definitions — all licensed sources).

intraspecies 12 letters wn-def

arising or occurring within a species; involving the members of one species

intraspecific 13 letters wn-def

arising or occurring within a species; involving the members of one species