Tubenose Goby Phylogeography
Cryptic taxa present a unique difficulty in the description of biological diversity, which DNA sequencing approaches often readily resolve. The tubenose goby Proterorhinus – along with additional members of the Ponto-Caspian neogobiin gobies and other fauna (e.g., dreissenid mussels) – has recently expanded its range in Eurasia, as well as established non-native populations in the North American Laurentian Great Lakes via ballast water transport. Here we analyze mitochondrial (cytochrome b [cyt b] and cytochrome c oxidase subunit 1 [COI]) and nuclear (recombination activating gene 1 [RAG1]) DNA sequences and morphological characters from exotic Great Lakes as well as introduced and native Eurasian population sites of Proterorhinus marmoratus (Pallas) sensu lato in the first comprehensive examination of its characters across its range.
Marked genetic divergence and morphological differentiation in body shape indicate species-level separation between freshwater and marine/brackish lineages, dating to approximately 3.82-4.30 million years of separation between the two lineages. In addition, freshwater lineages within the Black and Caspian Sea basins show significant genetic and morphological differentiation, corresponding to an estimated 0.92-1.03 million years separation between freshwater lineages in these two basins. There are thus at least three separate species currently contained within Proterorhinus marmoratus: a marine species in the Black Sea proper, a freshwater species found in rivers within the Black Sea basin (which was introduced into the North American Great Lakes), and a second freshwater species inhabiting the Caspian Sea/Volga River basin.
Proteorhinus marmoratus was originally described by Pallas (1814) from marine specimens from Sevastopol, on the Crimean Peninsula, and this name would remain with the marine tubenose goby identified in this study. The freshwater tubenose goby in the Black Sea basin was originally described as P. semilunaris (Heckel, 1840), prior to its synonymy with P. marmoratus, and we propose the resurrection of that name and provide a redescription of the species. The Caspian basin taxon may correspond with P. semipellucidus (Kessler, 1857), a putative freshwater species in the Caspian basin that was originally described from a single specimen. A fourth putative species was also identified from a single specimen from the Kumo-Manych Depression (a geologic depression separating the Russian Plain from the Caucasus Mountains); however, further sampling and analysis is necessary to clarify its specific status.
Figure 1. Collection locations of Proterorhinus in native and invasive Eurasian locations. Shaded area indicates current range of Proterorhinus (adapted from Miller, 2003).
Figure 2. Maximum likelihood phylogenetic tree of Proterorhinus and other outgroups based on combined sequence data from two mitochondrial (cytochrome b; cytochrome c oxidase I) and one nuclear (recombination activating gene I) genes. Numbers above branch include maximum parsimony bootstrap values (1000 pseudoreplications; plain text) and decay indices (bold text); numbers below branches include maximum likelihood bootstrap values (1000 pseudoreplication; italic text) and Bayesian posterior probabilities (plain text)
Figure 3. Plots of the a) second vs. first; and b) fifth vs. second principal components (PC) from a principal components analysis of 123 tubenose gobies. ● = Proterorhinus marmoratus; ○ = P. semilunaris; □ = P. sp. cf semipellucidus. 95% confidence intervals (dashed, solid, and dotted lines, respectively) and centroids (+) are drawn for each species. A multivariate analysis of variance (MANOVA) using both body size and shape information (PC I-V), as well as body shape (PC II-V) alone detected highly significant differences between the two taxa (PC I-V, Wilks’ λ = 0.41, F10, 232 = 12.88, P << 0.001; PC II-V, Wilks’ λ = 0.54, F8, 234 = 14.74, P << 0.001).
Neilson, M.E. and C.A. Stepien. 2009a. Evolution and phylogeography of the tubenose goby genus Proterorhinus (Gobiidae: Teleostei): Evidence for new cryptic species. Biological Journal of the Linnean Society 96: 664-684.