Monkey Goby Phylogeography
The monkey goby Neogobius fluviatilis (Teleostei: Gobiidae) is one of a suite of Ponto-Caspian species to expand and become established outside of its native range during the past 50 years via canals and shipping (Fig. 1). Neogobius fluviatilis is euryhaline and broadly distributed throughout the Ponto-Caspian region, inhabiting both inland freshwater habitats and saline waters. It is a moderately large goby (to 195 mm total length) living in shallow, sandy-bottom habitats (Pinchuk et al., 2003). Like other members of the Ponto-Caspian gobiid species flock (Gobiidae: Benthophilinae; Neilson & Stepien, 2009b), it lacks a swim bladder, males show territorial nesting behaviour, and it undergoes direct development to hatch as juveniles (Pinchuk et al., 2003). Neogobius fluviatilis is presently divided into two subspecies: N. f. fluviatilis (Pallas, 1814) in the Black and Azov Seas and associated drainages and N. f. pallasi (Berg, 1916) in the Caspian Sea basin. The two subspecies are distinguished by the presence of a darker lower band on the first dorsal fin, reduced average numbers of lateral scales and longitudinal scale rows and a shorter snout in N. f. pallasi (Berg, 1949), as well as some reported variations in osteology (Pinchuk et al., 2003).
Figure 1. Current native (stippled) and invasive distribution (shaded) of monkey gobies (adapted from Pinchuk et al., 2003) in the Ponto-Caspian region and central/northern Europe, respectively, showing sampling sites (circles = Neogobius fluviatilis; squares = Neogobius pallasi).
Figure 2. Maximum likelihood phylogenetic analyses of monkey goby for (a) mtDNA cytochrome b gene; (b) nuclear RAG1 gene. Numbers above nodes indicate bootstrap support (% of 2000 pseudoreplications). Trees are rooted using two congeneric species (round goby Neogobius melanostomus and Caspian goby N. caspius). Branch tip labels indicate haplotype number within a clade (cyt b; 2A) or the individual (GLGL tissue extraction code) used for the analysis (RAG1; 2B).
Figure 3. Statistical parsimony networks of monkey goby cytochrome b haplotypes from the A) Black Sea basin = Neogobius fluviatilis and B) the Caspian Sea basin = Neogobius pallasi. Circles are sized according to total observed frequency of that haplotype. Lines indicate a single mutational step between the haplotypes. Small, unlabelled circles represent hypothesized unsampled haplotypes. Haplotypes are coloured as in Fig. 4.
Figure 4. Bayesian structure version 2.2.3 (Pritchard et al., 2000) analyses of monkey goby populations using 10 microsatellite loci. K = 4 population groups was identified as the optimal value of K using the ΔK method of Evanno et al. (2005). The analysis at K = 2 is included to show the primary separation among the two monkey goby taxa (Black Sea basin assignments are coloured dark orange, those to the Caspian Sea basin are dark purple). Each fish is represented as a vertical line partitioned into K coloured segments, reflecting that individual’s estimated group membership fractions. Black lines separate sampling sites, which are labelled above the figure (*introduced locations). Brackets above the population sites indicate major watersheds. Distribution of cytochrome b haplotypes from the maximum likelihood tree (Fig. 2) among populations is shown below figure (solid line = Black Sea clade haplotypes; dashed line = Caspian Sea clade haplotypes).
Figure 5. Plot of the second and third principal components (PC) from a principal components analysis of morphometric data from 141 monkey gobies. Circles = Neogobius fluviatilis; squares = Neogobius pallasi. A multivariate analysis of variance using both body size and shape information (PC 1–5) as well as body shape alone (PC 2–5), exhibited highly significant differences among basins (PC 1–5, Wilks’ λ = 0.703, F5,135 = 11.407, P << 0.001; PC 2–5, Wilks’ λ = 0.704, F4,136 = 14.303, P << 0.001). Centroids (black circle and square) and 95% confidence ellipses for the Black (solid line) and Caspian (dashed) Sea basin individuals are given.
Neilson, M.E.* and C. A. Stepien. 2011. Historic speciation and recent colonization of Eurasian monkey gobies (Neogobius fluviatilis and N. pallasi) revealed by DNA sequences, microsatellites, and morphology. Diversity and Distributions, DOI: 10.1111/j.1472-4642.2011.00762.x.