Gromphas dichroa Blanchard, 1846

Cupello, Mario & Vaz-de-Mello, Fernando Z., 2015, A new species and the phylogeny of the South American genus Gromphas Brullé, 1837 (Coleoptera: Scarabaeidae: Scarabaeinae: Phanaeini), Journal of Natural History 50, pp. 943-969 : 954-955

Gromphas dichroa Blanchard, 1846

( Figures 5 , 6 )

Comments

Although only nine specimens of G. dichroa were examined in Cupello and Vaz-de-Mello (2013), we recognized a wide colour variation in this species. Now, having examined the MACN collection, we found other seven specimens collected between 1926 and 1927 in Santo Tomé, Corrientes, Argentina, a locality already recorded for this species. This series is very interesting because it shows for just one locality much of the colour variation described by us earlier, including specimens that are entirely green, with green pronotum and dark blue elytra, and with pronotum metallic green on sides and along posterior margin and greenish-red in centre and dark blue elytra. This finding supports our hypothesis that colour varies individually within at least some populations, and it is not necessarily a matter of geographic variation nor evidence for recognizing more than one taxa. Yet, as pointed out by one of the anonymous reviewers of this work, ‘ the fact that the colour is subject to wide variation in one of the studied populations does not implicate that this variation necessarily occurs in the other populations of this species. There is the probability that some populations bear just a single or two colours ’. We agree that this is a possible scenario and so more collecting is needed for a fuller understanding of colour variation in G. dichroa .

The female from the Hermann Burmeister collection has one of its tarsi complete (i.e. it is not broken as in all the other females examined) and it is identical to the tarsus of G. inermis : the apical protarsomere is short and lacks an apical spiniform prolongation.

Additional material examined

ARGENTINA: CORRIENTES: Santo Tomé, September 1926, without collector – 1 male ( MACN); Santo Tomé , February 1927, without collector – 2 males and 2 females ( MACN); Santo Tomé, October 1928, without collector – 1 male ( MACN) . URUGUAY: December 1894, without collector – 1 female ( MACN – Hermann Burmeister coll.) . SALTO (?): without date, Hermano Mario col . – 1 male ( MLPA) . MONTEVIDEO: without date, J . Tremoleras col . – 1 male ( MLPA) .

Figures

Figure 5. Updated distribution of the six species of Gromphas.

Figure 6. Phylogeny of Gromphas. Above: Cladogram showing the phylogenetic relationship of the species of Gromphas and the evolution of their characters. Black circles indicate uncontroverted synapormorphies; white circles with black margin, controverted synapomorphies; red circles, ambiguous uncontroverted synapomorphies; and white circles with red margin, ambiguous controverted synapomorphies. Below: Support values given for each clade are decay index (above branch) and bootstrap (below branch).