CONICET | Buscador de Institutos y Recursos Humanos

The single-stiped morphology and simple thecal form make the genus Azygograptus easily recognizable, but the identification at species level results complicated by subtle differences, the scarcity of detailed descriptions, intraspecific variations and deformation. Here, an elliptical Furrier analysis is carried out in the proximal end of individuals to test the systematic classification at species level. The resulting coordinates were subjected to an exploration using principal components and cluster analysis to examine groupings. We include 27 individuals from two species characterized by the absence of adpressed growth of theca1 along the sicula: Azygograptus lapworthi Nicholson and A. eivinonicus Elles. Most of the material comes from the Central Andean Basin (northwestern Argentina and southern Bolivia), but specimens from South China, Scandinavia and Great Britain are also included for comparison. The contour analysis showed that the first three components explain 79.21% of the total variation in the shape of the specimens. PC1 represented the stipe width at theca1 and the differences in the sicular morphology: narrow stipes at the theca1 and large-elongated siculas (negative) vs. wide stipes at theca1 and short-stouter siculas (positive). Meanwhile, PC2 explained the variation in the stipe divergence angle: close to 90 (negative) vs. greater than 90 (positive). Moreover, dendrograms illustrated that individuals from different species are related and grouped together. Thus, the resulting morphospaces and clusterings allow inferring that the specimens previously assigned as two different species are geomorphometrically indistinguishable. Therefore, we can conclude that all the material could correspond to a unique species (A. lapworthi) with intraspecific variations.

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