25802
However , the four sampled species of Polymorphus were nested within several clades , indicating that these species do not share a common ancestor , requiring further taxonomic revision using phylogenetic systematics , and reexamination of morphological and ecological data .
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Please list all entity words in the text that fit the category.Output format is "type1: word1; type2: word2". 
Option: Chemical 
Text: {0} 
Answer:
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