Taxonomy and Biogeography of the Galapagos Branchiopod Fauna (Anostraca, Notostraca, Spinicaudata)

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Abstract
In spite of the isolated nature of the Galapagos Islands and the scarcity of inland waters, three of the main branchiopod taxa are represented on the archipelago by Dendrocephalus sarmentosus Pereira and Belk (Anostraca), Triops longicaudatus LeConte (Notostraca), and Eulimnadia cylindrova Belk sensu lato (Spinicaudata). These species have been collected from different botanical regions within the Galapagos. The present study documents their systematics and morphology using both light microscopy and scanning electron microscopy (SEM). The current systematics of the "conchostracan" genus Eulimnadia still present problems that hamper reliable identifications. The use of egg morphology, recently suggested to be a key taxonomic criterion within the genus, is here criticized, on the basis of material identified as E. cylindrova from several North American populations. Triops longicaudatus is known from North and South America, while Dendrocephalus sarmentosus is endemic to the Galapagos. Eulimnadia cylindrova is described from the United States and Mexico. Bird migration, transport by winds, or anthropgenic action are potential agents for the dispersal of cysts from mainland-source populations and are possible explanations for the affinities with mainland species and populations. In populations of E. cylindrova sensu lato and T. longicaudatus, no males have been observed. Unisexual modes of reproduction are considered to favor colonization, since only a single egg may suffice to establish a new population.