Complex sentence: The most recognizable subspecies is the red-eared slider ("T. s. elegans"), which is popular in the pet trade and has been introduced to other parts of the world by people releasing it to the wild.
Split into simpler sentences: The most recognizable subspecies is the red-eared slider ("T. s. elegans"), which is popular in the pet trade. This subspecies has been introduced to other parts of the world by people releasing it to the wild.