Abstract
Trichomycterus areolatus Valenciennes, 1846 is a small endemic catfish inhabiting the Andean river basins of Chile. In this study, the morphological variability of three T. areolatus populations, collected in two river basins from southern Chile, was assessed with multivariate analyses, including principal component analysis (PCA) and discriminant function analysis (DFA). It is hypothesized that populations must segregate morphologically from each other based on the river basin that they were sampled from, since each basin presents relatively particular hydrological characteristics. Significant morphological differences among the three populations were found with PCA (ANOSIM test, r = 0.552, p < 0.0001) and DFA (Wilks’s λ = 0.036, p < 0.01). PCA accounted for a total variation of 56.16% by the first two principal components. The first Principal Component (PC1) and PC2 explained 34.72 and 21.44% of the total variation, respectively. The scatter-plot of the first two discriminant functions (DF1 on DF2) also validated the existence of three different populations. In group classification using DFA, 93.3% of the specimens were correctly-classified into their original populations. Of the total of 22 transformed truss measurements, 17 exhibited highly significant (p < 0.01) differences among populations. The data support the existence of T. areolatus morphological variation across different rivers in southern Chile, likely reflecting the geographic isolation underlying population structure of the species.
Highlights
Almost all species display morphological variation within and among populations in response to environmental and genetic factors, or as a consequence of behavioral and physiological differences (West–Eberhard 1989, Schwander and Leimar 2011)
Nineteen of 22 truss measurement were found to be significantly different among populations (Table 1), including 17 (1–2, 1–3, 1–4, 2–4, 3–4, 3–6, 4–6, 5–6, 5–7, 6–7, 6–8, 7–9, 7–10, 8–9, 8–10, 9–10, 9–11 ) with highly significant (p < 0.01) values that were further tested in multivariate analysis using discriminant function analysis (DFA)
The segregation among populations was confirmed by principal component analysis (PCA) and DFA scatter-plot based on scores for each sample that showed non, or slight, overlapping clusters of points for each population
Summary
Almost all species display morphological variation within and among populations in response to environmental and genetic factors, or as a consequence of behavioral and physiological differences (West–Eberhard 1989, Schwander and Leimar 2011). Water velocity could have a significant effect on different attributes of body shape, such as, head depth and length, caudal peduncle depth, caudal fin depth and length, and body depth, among others (Imre et al 2002, Keeley et al 2006, Grünbaum et al 2007, Istead et al 2015). These findings indicate that fishes are largely amenable to environmentally-induced morphological variations
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