Daphnia O. F. Müller, 1785

Elías-Gutiérrez, Manuel, Jerónimo, Fernando Martínez, Ivanova, Natalia V., Valdez-Moreno, Martha & Hebert, Paul D. N., 2008, DNA barcodes for Cladocera and Copepoda from Mexico and Guatemala, highlights and new discoveries, Zootaxa 1839 (1), pp. 1-42 : 9

Genus Daphnia O. F. Müller, 1785

This genus was represented in our collections by six species, all well discriminated by COI sequences. Three of the species belonged to the subgenus Daphnia ( D. parvula , D. cheraphila Hebert and Finston 1996 , Daphnia sp. ), and three to the subgenus Ctenodaphnia ( D. magna , D. exilis , D. lumholtzi ). Comparisons with sequence records in GenBank revealed that Daphnia exilis showed little divergence from its close relative D. spinulata (minimum 0.80, maximum 3.9%), from Argentina. Despite this fact, the D. exilis from Mexico was grouped in the same cluster, which was distinct from the cluster formed by D. spinulata . These two species do show allozyme ( Adamowicz et al. 2004) and morphological differences ( Benzie 2005).

Daphnia cheraphila was recently described by Hebert & Finston (1996) who included material from Mexico in their original description. Our material showed 1.94% COI divergence from sequences in GenBank for this species. Another Daphnia , a member of the pulex group, seems to represent a new species as its closest COI match (12.7%) was to Daphnia parvula from Río Coronda, Argentina.

We recorded the invasive species D. lumholtzi for the first time in Mexico in the northern state of Sonora. Given its broad distribution across the United States and its presence in southern Canada, its detection was not unexpected. The Mexican specimens showed barcode identity with populations from the other North American populations that have been sequenced (0.47% maximum) and high divergences (8.68% minimum) with Australian specimens ( Havel et al. 2000).