Revision des Xiphophorus montezumae/cortezi - Komplexes und Neubeschreibung einer Subspezies

Streszczenie:

" P. Lechner and A. C. Radda revise the Xiphophorus montezumae/cortezi complex of eastern Mexico and describe a distinctive new form from the Río Tempoal drainage of the Río Pánuco system. Their study combines field collections, aquarium observations, morphology, gonopodial structure, coloration, and geographic distribution to distinguish several closely related populations occurring in separate headwater systems

The newly described Xiphophorus montezumae birchmanni is particularly remarkable because adult males possess only a minute rudiment of the sword normally associated with members of the complex. It also differs in its short head, large sail-like dorsal fin, body proportions, coloration, and gonopodium details. The species inhabits shallow, fast-flowing streams with gravel or rocky substrates, sometimes at very high water temperatures. Its name honors Heinz Birchmann, who participated in its discovery and first brought living specimens to Europe

The authors recognize four geographically separated forms within the complex: X. montezumae montezumae from the Río Verde system, X. montezumae cortezi from the Río Moctezuma-Axtla region, the unnamed “Hamburg 1964” form from the Río Salto and Río Sabinas systems, and X. montezumae birchmanni from the Río Tempoal drainage

The paper highlights the remarkable geographic differentiation of swordtails within the upper Río Pánuco basin and illustrates how isolated river systems can promote morphological and reproductive divergence among closely related populations. "