Abstract
Introduced species may cause harm to native fish populations, which to design any conservative program to control the exotics an identification key is necessary. To find the morphological differences among the exotic Rhinogobius lindbergi and its sympatric congeners including the endemic Ponticla iranicus and the native Ponticla gorlap, a 15-landmark morphometric system was used to examine 90 specimens in Sefid River, in the Southern Caspian Sea basin. Univariate analysis of variance showed significant differences among the means of the three groups for 79 out of 105 standardized morphometric measurements. Principal component analysis (PCA) and canonical variates analysis (CVA) confirmed the statistically significant difference among these species. The CVA scatter plot showed that the 90 studied specimens grouped into three distinct areas with a degree of overlap between P. iranicus and P. gorlap. Clustering based on Euclidean distances among the groups of centroids using an UPGMA indicated segregation of the three species into two distinct clusters: P. iranicus and P. gorlap in one group and R. lindbergi in the other group. The exotic Rhinogobius can be distinguished from the sympatric gobies in Sefid River by short snout (vs. longer), deep body (vs. shallow), deeper head, stout body, and smaller ventral disc.
Highlights
Invasive species are alien organisms that have been introduced into an area outside of their natural range, establishing self-sustaining populations and spreading beyond their initial point of introduction, with deleterious impacts on the environment, economy and human health (Lymbery et al 2014)
It is well known that the female and male specimens of the gobies have some morphological differences (Mousavi-Sabet et al 2012; Vasil′eva et al 2015), but the interaction between morphometric measurements used in this study by truss network system and sexes uses ANOVA analysis was not significant (P > 0.05), demonstrating a negligible effect of sex on observed variations; the data for both sexes were pooled for all subsequent analyses
The results of the multivariate analysis demonstrated that the three examined species are correctly separated from each other, which the two Ponticola (P. iranicus and P. gorlap) are classified as one clade and the Rhinogobius in the other clade
Summary
Invasive species are alien (non-native) organisms that have been introduced into an area outside of their natural range, establishing self-sustaining populations and spreading beyond their initial point of introduction, with deleterious impacts on the environment, economy and human health (Lymbery et al 2014). Preparing any key to identify fish species needs powerful analytical manners which the traditional and modern morphological analyzing methods are normally used for fish populations/species. Morphological characters are most important in the identification and taxonomy of fishes, and the only known facts about many fishes. Understanding the function of a morphological structure is a stronghold for practical use in taxonomy and ecology too (Turan 2004; Yamamoto et al 2006; Pollar et al 2007). In addition to traditional method, in recent years, truss network system is increasingly used for morphometric measurements with the purpose of species and/or stock differentiation
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