Table 1.
The original and published otolith material used in this study.
Status: presence status in the Ponto-Caspian basin, i.e., CE, Caspian Sea endemic; PCN, Ponto-Caspian native; AZE, Azov Sea endemic; BAN, Black Sea/Azov Sea native; BE, Black Sea endemic; EX, exotic. Quant.: taxonomic level of quantitative analysis, i.e., L, lineage; T, tribe; G, genus; S, species. N, number of specimens; SL, standard length in mm. Institutional abbreviations: CMNFI, Canadian Museum of Nature in Ottawa; NMNH NASU, Zoological Museum of Ukraine in Kiev; RBINS, Royal Belgian Institute of Natural Sciences; SMF, Senckenberg Museum, Frankfurt/Main; ZM-CBSU, Zoological Museum of Shiraz University, Collection of Biology Department, Shiraz, Iran; ZMMU/ZMMSU, Zoological Mueum, Moscow University in Moscow; ZMUC, Zoological Museum, University of Copenhagen; ZSM, SNSB-Bavarian State Collection of Zoology, Munich.
Fig 1.
Schematic illustration of the left sagittal otolith medial face of Ponticola gorlap, showing the terminology for characters and morphometric measurements.
OL, maximal otolith length; OL2, minimal otolith length; OH, maximal otolith height; OA, otolith area; OP, otolith perimeter; CL, colliculum length; SuL, sulcus length; SuH, sulcus height; SuP, sulcus perimeter; SuA, sulcus area; SuTipV, distance from sulcus tip to the ventral margin; SuEndV, distance from sulcus end to the ventral margin; α, inclination angle of ostium; β, inclination angle of anterior rim; γ, inclination angle of posterior rim; δ, angle of preventral projection to posterodorsal projection traverse.
Fig 2.
Otolith morphology of Benthophilini.
Benthophilus leobergius: A, ZM-CBSU 50; B, ZM-CBSU 51; C, ZM-CBSU 53; D, ZM-CBSU 54; E, ZMMU P.22625. Benthophilus pinchuki: F, ZM-CBSU 119; G, ZMMU P.16127. Benthophilus macrocephalus: H, ZMMU P.15889. Benthophilus durrelli: I, ZMMU P.21611. Benthophilus baeri: J, ZMMU P.16141. Benthophilus abdurahmanovi: K, ZMMU P.15890. Benthophilus stellatus: L, ZMMU P.11023. Anatirostrum profundorum: M, CMNFI 1999–0023.1. Benthophiloides brauneri: N, NMNH NASU 5136. Caspiosoma caspium: O, ZMMU P.13965. Scale bars = 0.5 mm.
Fig 3.
Otolith morphology of Neogobiini.
Neogobius pallasi: A, ZM-CBSU 20; B, ZM-CBSU 22; C, ZM-CBSU 23; D, ZM-CBSU 27. Neogobius fluviatilis: E, ZMMU, P.22433. Neogobius caspius: F, ZM-CBSU 2; G, ZM-CBSU 6; H, ZM-CBSU 12; I, ZM-CBSU 13; J, ZM-CBSU 14. Neogobius melanostomus: K, ZM-CBSU 15; L, ZM-CBSU 16; M, ZM-CBSU 18; N, ZM-CBSU 19; O, unnumbered RBINS specimen [43]. Neogobius bathybius: P, ZM-CBSU 101; Q, ZM-CBSU 106; R, ZM-CBSU 108; S, ZM-CBSU 111; T, ZM-CBSU 110. Scale bars = 0.5 mm.
Fig 4.
Otolith morphology of Mesogobius.
Mesogobius batrachocephalus: A–B, ZMUC P2395071-72; C, drawing from Nolf [49]. Mesogobius nonultimus: D, ZM-CBSU S036-1. Scale bars = 1 mm.
Fig 5.
Otolith morphology of Ponticola.
Ponticola iranicus: A, ZM-CBSU 37; B, ZM-CBSU 38; C, ZM-CBSU 39; D, ZM-CBSU 40; E, ZM-CBSU 141; F, ZM-CBSU 144. Ponticola patimari: G, ZM-CBSU P1; H, ZM-CBSU P2; I, ZM-CBSU P3; J, ZM-CBSU P4; K, ZM-CBSU P6. Ponticola syrman: L, ZM-CBSU 142; M, ZM-CBSU 139. Ponticola gorlap: N, ZM-CBSU 41; O, ZM-CBSU 44; P, ZM-CBSU 45; Q, ZM-CBSU 46; R, ZM-CBSU 48. Ponticola iljini: S–T, ZMMSU P-23516; U–V, Ponticola kessleri: non-catalogued specimens from the RBINS collection, Danube, near Vienna in Austria [43]. Ponticola hircaniaensis: W, ZM-CBSU K18; X, ZM-CBSU K28 [5]. Scale bars = 0.5 mm.
Fig 6.
Otolith morphology of Proterorhinus.
Proterorhinus nasalis: A, ZM-CBSU 56; B, ZM-CBSU 57; C, ZM-CBSU 59; D, ZM-CBSU 60; E, ZM-CBSU 61; F, ZM-CBSU 62. Proterorhinus semilunaris: G, ZM-CBSU 122; H, ZM-CBSU 126; I, ZM-CBSU 125. Scale bar = 0.2 mm.
Fig 7.
Otolith morphology of the studied species from the Pomatoschistus and Acanthogobius lineages.
Knipowitschia caucasica: A, ZM-CBSU 63; B, ZM-CBSU 64; C, ZM-CBSU 80; D, ZM-CBSU 82; E, ZM-CBSU 128; F, ZM-CBSU 129. Knipowitschia longecaudata: G, ZM-CBSU 65; H, ZM-CBSU 66; I, ZM-CBSU 67; J, ZM-CBSU 68; K, ZM-CBSU 69; L, ZM-CBSU 92; M, ZM-CBSU 93; N, ZM-CBSU 94; O, ZM-CBSU 95; P, ZM-CBSU 96; Q, ZM-CBSU 97. Hyrcanogobius bergi: R, ZM-CBSU 84; S, ZM-CBSU 85; T, ZM-CBSU 86; U, ZM-CBSU 87; V, ZM-CBSU 90; W, ZM-CBSU 91. Rhinogobius sp.: X, ZM-CBSU 70; Y, ZM-CBSU 71; Z, ZM-CBSU 72; A’, ZM-CBSU 73; B’, ZM-CBSU 74; C’, ZM-CBSU 76. Scale bars = 0.2 mm.
Table 2.
Otolith variables that differed significantly among the studied lineages [upper right matrix: Mann-Whitney test, p < 0.05; lower left matrix: ANOVA, p < 0.05, with Tukey HSD (indicated with superscript T) and Dunnett T3 (superscript D) post-hoc tests, depending on homogeneity of variances (Levene’s test, p > 0.05].
Fig 8.
Discriminant function plots based on the otolith variables at taxonomic levels.
(a) Lineage, (b) tribe, (c) genus, and (d–f) species in different genera.
Table 3.
Classification matrix of the canonical discriminant analysis based on otolith variables for the three lineages.
Correctly classified samples are shown in bold.
Table 4.
Otolith variables that differed significantly among the three benthophiline tribes [upper right matrix: Mann-Whitney test, p < 0.05; lower left matrix: ANOVA, p < 0.05, with Tukey HSD (indicated with superscript TU) and Dunnett T3 (superscript D3) post-hoc tests, depending on homogeneity of variances (Levene’s test, p > 0.05].
Table 5.
Classification matrix of the canonical discriminant analysis based on otolith variables for the three benthophiline tribes.
Correctly classified samples are shown in bold.
Table 6.
Otolith variables that differed significantly between the studied genera [upper right matrix: Mann-Whitney test, p < 0.05; lower left matrix: ANOVA, p < 0.05, with Tukey HSD (indicated with superscript T) and Dunnett T3 (superscript D) post-hoc tests, depending on homogeneity of variances (Levene’s test, p > 0.05].
Table 7.
Classification matrix of the canonical discriminant analysis based on otolith variables for the seven genera.
Correctly assigned samples are shown in bold.
Table 8.
Otolith variables that differed significantly between the Caspian Neogobius species [upper right matrix: Mann-Whitney test, p < 0.05; lower left matrix: ANOVA, p < 0.05, with Tukey HSD (indicated with superscript T) and Dunnett T3 (superscript D) post-hoc tests, using homogeneity of variances (Levene’s test, p > 0.05].
Table 9.
Classification matrix of the canonical discriminant analysis based on otolith variables for the species of Neogobius and Ponticola.
Correctly classified samples are shown in bold.
Table 10.
Otolith variables that differed significantly between the Caspian species of Ponticola and Neogobius bathybius [upper right matrix: Mann-Whitney test, p < 0.05; lower left matrix: ANOVA, p < 0.05, with Tukey HSD (indicated with superscript T) and Dunnett T3 (superscript D) post-hoc tests, depending on homogeneity of variances (Levene’s test, p > 0.05].
Table 11.
Otolith variables that differed significantly between the studied species in the Pomatoschistus and Acanthogobius lineages [upper right matrix: Mann-Whitney test, p < 0.05; lower left matrix: ANOVA, p < 0.05, with Tukey HSD (indicated with superscript T) and Dunnett T3 (superscript D) post-hoc tests, depending on homogeneity of variances (Levene’s test, p > 0.05].
Table 12.
Classification matrix of the canonical discriminant analysis based on otolith variables for the species of the Pomatoschistus and Acanthogobius lineages.
Correctly classified samples are shown in bold.
Fig 9.
Average linkage dendrogram (using Euclidean distances) showing the phenotypic relationships between otoliths of the studied species, based on all 31 variables.
Yellow, Benthophilini; green, Neogobiini; pink, Ponticolini.
Fig 10.
Phylogenetic mapping of general otolith morphology for the studied benthophiline species (COI phylogeny modified from Zarei et al. [30]).
Each tribe is represented by a different color: yellow, Benthophilini; green, Neogobiini; pink, Ponticolini. BI posterior probability/ML bootstrap support values are indicated beside the nodes. Double bar at the root indicates that branch has been reduced in length and is not proportional to the scale. Alphabetical letters inside parentheses after the species names (A–Q: 17 species) refer to their otolith drawings on the right. Otolith drawings on the upper left corner belong to Ponticola iljini (R–S), Mesogobius nonultimus (T), Benthophilus pinchuki (U), B. macrocephalus (V), B. durrelli (W), B. baeri (X), Anatirostrum profundorum (Y), and Benthophiloides brauneri (Z), which have not been phylogenetically analysed.
Fig 11.
Head lateral line system (left side, suborbital rows) of Ponticola, Proterorhinus, Mesogobius, and Neogobius.
For comparison, the head lateral line system and otolith drawings of M. nonultimus, N. bathybius, and N. melanostomus are shown in the bottom row.
Table 13.
Some morphological and ecological characteristics of Neogobius melanostomus, N. bathybius, and Mesogobius nonultimus [70–7,2].