Neighbor-joining tree of lineages in the Daphnia pulex species complex. Representative sequences of the mitochondrial ND5 gene were taken from Colbourne et al. . The relationship of the SAPC-C lineage, first identified by Mergeay et al. , to the rest of the complex is based on the mitochondrial 12S rRNA gene. Attempts to amplify the ND5 fragment from members of this lineage have been unsuccessful. Taxa are indicated as follows: ARE = D. arenata, EPC = European D. pulicaria, EPX = European D. pulex, MEL = D. melanica, MID = D. middendorffiana, NAPC = North American D. pulicaria (e = eastern, w = western, p = polar), NAPX = North American D. pulex, SAPC = South America D. pulicaria, TEN = D. tenebrosa.