Aphis (Aphis) pulverea Nieto Nafría, Moreno-González & Ortego, 2022

Nieto Nafría, Juan M., Ortego, Jaime, Moreno-González, Víctor & Durante, M. Pilar Mier, 2022, The genus Aphis (Hemiptera, Aphididae) living on Asteraceae species in southern South America: Argentina and Chile, with five new species, Zootaxa 5183 (1), pp. 439-463 : 455-459

Aphis (Aphis) pulverea Nieto Nafría, Moreno-González & Ortego sp. n.

Types. Holotype: apterous viviparous female CHI-522- 7 (mounted with two paratypes): CHILE: AYSéN DEL GENERAL CARLOS IBáñEZ DEL CAMPO, Capitán Prat, Baker and Neff rivers junction (47º 07' S, 72º 46' W, 230 m), on Senecio patagonicum , 16-January-2019, collection of the Universidad de León. Paratypes: 190 apterous viviparous and 4 alate viviparous females, collection of the Universidad de León; of them: (1) same data as the holotype, 66 apterae and 4 alatae; (2) ARGENTINA: RÍO NEGRO: Pilcaniyeu: Dina Huapi (41º 04' S, 71º 07' W, 900 m), on Senecio filaginoides , 19-January-2000, 52 apterae; (3) ARGENTINA: CHUBUT: Futaleufú: Trevelin (43º 07' S, 71º 26' W, 390 m), on Senecio filaginoides , 20-January-2000, 40 apterae; and (4) CHILE: MAGALLANES Y ANTáRTICA CHILENA: Última Esperanza: Paine falls (50º 56' S, 72º 47' W, 120 m) on Senecio sp. , 6-January-2016, 32 apterae.

Etymology. The Latin epithet “pulvereus, -a, -um” means dusty or pulverulent and allows to remember a very distinguishing character of the species.

Descriptions. Apterous viviparous females ( Fig. 7 ). From 191 specimens (164 measured). When alive dull black under a very remarkable layer of white wax powder, with conspicuous black cauda, and antennae and legs mostly brown dark to black. When mounted, most specimens are well pigmented because they are extensively sclerotized (see below). Head smooth for the most part, dark to very dark brown and often with a thin, irregular and pale epicranial line. Frons straight or nearly straight. ANT.I and ANT.II with some irregular streaks. ANT.III with 4–10(14) ST. URS with concave edges on its proximal third. TH.1–2 with sclerotized and striate bands not as dark as the head and ABD sclerites, usually almost complete, fragmented in less pigmented specimens. TH.3 to ABD.6 with a spino-pleural band of diverse development, sometimes cut in the middle and sometimes in contact with the immediate ones and with the MG patches; these last are usually as dark as spiracular sclerites and paler than intersegmental sclerites, they are absent in ABD.1 as also in other segments in less pigmented specimens. ABD.7–8 with transverse bands, usually wide and extensive to the sides. COM MG TUB absent. ST on ANT, TH, ABD and legs are thin, pointed and very pale. Coxae and trochanters light brown, like most part of femora. Tarsal formula, 3.3.2(3). SIPH very dark brown or black (always darker than the head), truncated-conical with a relatively wide base or sub-cylindrical and not so wide at the base. ABD.8 with ((1))2((4)) ST. Genital plate with 2–12 discal and 8–15 posterior ST. Cauda as dark as SIPH, elongated finger-shaped with quite pointed apex, carrying 7–17 ST, which are especially long and extremely thin. Other qualitative features in “Common features of the new species”. Quantitative features in Table 4 .

......Continued on the next page

Alate viviparous females ( Fig. 8 ). From 4 specimens. ABD sclerotization diverse, from spinal and pleural sclerites on ABD.1, spinopleural bands and broad MG sclerites on ABD.2–6, and transverse bands on ABD.7–8 (in biggest specimen), to only MG sclerites on ABD.2–5, MG plus minimal spinal sclerite on ABD.6, and small and scattered sclerites on ABD.7–8 (in smallest specimen). ANT.III with 7–10 SEC SEN. Other qualitative features in “Common features of the new species”. Quantitative features in Table 4 .

Bionomics and distribution. The four collections of this species were made on plants of the Senecio genus, very abundant in Argentine and Chilean Patagonia. In all cases, only parthenogenetic females were obtained, it cannot be guaranteed that the species is holocyclic, but this is expected due to the latitude and the harsh winters.

Aphis pulverea sp. n. it has always been collected within the territory belonging to the Patagonia biogeographic formation, and south of parallel 40. Between the southernmost locality (Cascadas del Paine, Chile) and the northernmost (Dina Huapi, Argentina), there is an approximate distance of 2,500 km in a straight line, which suggests that the new species may be found throughout this area; furthermore, it may host on some of the numerous Senecio species present to the north of this area.

Taxonomic discussion, diagnosis. Specimens of A.pulverea sp. n. show great variation in various measurements, in the SIPH shape ( Fig. 7 A–D ) and in the density of wax cover, when alive, which is greater in the specimens from the Baker and Neff rivers junction ( Chile) than in other specimens. This variation could be a manifestation of a marked intraspecific variability or an indication of the existence of two or more taxonomic entities.

To solve the doubt, a Principal Component Analysis (PCA) followed by a Hierarchical Cluster of Principal Components (HCPC) was carried out under R v. 3.6.3 (R Core Team, 2020) with packages FactoMineR v. 1.42 ( Lê et al. 2008) and factoextra v. 1.0.5 ( Kassambara & Mundt, 2017). Measurements of 164 apterous viviparae that are sufficiently complete and well arranged on slides were used, of them: 43 from Dina Huapi ( Argentina), 33 from Trevelin ( Argentina), 58 from Baker and Neff rivers junction ( Chile) and 30 from Paine falls ( Chile). Only quantitative absolute features were used to avoid overfitting, although body and antenna lengths were removed to reduce size-effect.

HCPC suggests that apterous viviparae of A. pulverea sp. n. belong to two morphological groups as determined automatically by the higher relative loss of inertia ( Lê et al. 2008). All the specimens collected in Dina Huapi, almost all those collected in Trevelin (32 of 33) and in Paine falls (24 of 30), plus a few (4 of 54) collected in Baker and Neff rivers junction are part of a first group, while the majority of those from Baker & Neff rivers junction (54 of 58) and a few specimens from Trevelin and Paine falls (1 and 6 respectively) are part of a second group.

The limits of the ranges of dispersion of most absolute and relative metric features of body parts and setae are distinctively different for both groups. Both the lower and upper limits in the first group well lower than the equivalent limits in the second group, and the respective ranges overlap for the most part. Specimens with truncatedconical SIPH are majority in the first group, although there are specimens with cylindrical and sub-cylindrical SIPH; the opposite occurs in the second group. Therefore, it seems sensible to conclude that both morphological groups belong to the same taxonomic entity.

From the host plants, the collection places latitudes, and the collection dates, it is unlikely that the variations are related to the hosts or to the season or to a geographic cline. Therefore, the more logical conclusion, is that the species has great internal variability.

A. pulverea sp. n. shares characters with the species that form part of groups 7 and 9 of the key to apterous viviparous females of Aphidina species known in South America by Nieto Nafría et al. (2019a), however, it presents a very different ratio “SIPH / cauda”, which in the new species is no greater than 0.8 times.

Figures

FIGURE 7. Aphis pulverea Nieto Nafría, Moreno-González & Ortego. sp. n., apterous viviparous female. A, complete view, with details: ABD.1–2 MG, ABD.3 MG, ABD.4 spino-pleural band; B–D, complete view; E, ANT.III and ANT.VI; F, cauda. The scales vary according to specimens or parts photographed; see measurements in Table 1. Body length of specimens A, D (Baker and Neff rivers junction), B (Dina Huapi) and C (Paine falls): 2.175, 2.250, 1.900 and 1.905 mm respectively.

FIGURE 8. Aphis pulverea Nieto Nafría, Moreno-González & Ortego sp. n., alate viviparous female. A, complete view; B, abdomen (note the diverse sclerotization). C, ANT.III and ANT.VI; D, SIPH. The scales vary according to specimens or parts photographed; see measurements in Table 1.