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1 December 2000 Discrimination of Larval Morone Geometric Shape Differences with Landmark-Based Morphometrics
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We investigated the use of geometric morphological shape differences to differentiate laboratory-reared larval (4–22 days posthatch, < 10 mm SL) Morone chrysops, Morone saxatilis, and Morone chrysops ♀ × M. saxatilis ♂ hybrids. We also examined impacts of allometry on descriptions of individual shape. For validation of a shape-based taxonomic discrimination model, we used cellulose acetate electrophoresis to establish a “known species” test group of field-collected larvae based on banding patterns for the enzyme system esterase. Geometric shape was described with Cartesian coordinates of 16 anatomical landmarks located along the midsaggital outline of laboratory-reared (n = 373) and field-collected (n = 29) larvae. Coordinate data were reoriented and rescaled to uniform centroid size and analyzed as landmark displacements from a reference form. Discriminant function analysis resulted in 100% separation of M. chrysops and M. saxatilis larvae based on geometric shape. Discrimination success dropped to 87% when more variable data from hybrids were included in the discriminant function. Seventy percent and 87%, respectively, of field collected larvae (n = 29) and a randomly selected laboratory subgroup (n = 40) were correctly classified to taxon. Results suggest that taxonomic separation of early-stage larvae based on shape data is not affected by allometry but is sensitive to larval nutritional condition and handling. Landmark-based morphometrics may provide an improved, simple method of discrimination among species in sympatric populations of closely related larval fishes.

The American Society of Ichthyologists and Herpetologists
Richard S. Fulford and D. Allen Rutherford "Discrimination of Larval Morone Geometric Shape Differences with Landmark-Based Morphometrics," Copeia 2000(4), 965-972, (1 December 2000).[0965:DOLMGS]2.0.CO;2
Accepted: 9 May 2000; Published: 1 December 2000

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