A new species of Uroleucon (Hemiptera: Aphididae) on Madia (Asteraceae) in Chile

Uma nova espécie de Uroleucon (Hemiptera: Aphididae) em Madia (Asteraceae) no Chile

SYSTEMATICS, MORPHOLOGY AND PHYSIOLOGY

A new species of Uroleucon (Hemiptera: Aphididae) on Madia (Asteraceae) in Chile

Uma nova espécie de Uroleucon (Hemiptera: Aphididae) em Madia (Asteraceae) no Chile

Miguel A. Delfino^I; Wilfredo L. Gonzáles^II

^ICátedra de Entomología, Facultad de C.E.F. y N., Universidad Nacional de Córdoba Av. Vélez Sarsfield 299, 5000-Córdoba, Argentina

^IIDepto. Botánica, Universidad de Concepción, Casilla 160-C, Concepción, Chile [e-mail]

ABSTRACT

Uroleucon is one of very few aphid genera that have species indigenous to South America. A new species of aphid from Chile is described and illustrated, Uroleucon eumadiae sp. nov., living on the two South American species of the genus Madia (Asteraceae): M. sativa Mol. and M. chilensis (Nutt.) Reiche. Morphological characters are discussed and the characters by which this aphid species may be distinguished from related ones are given. The long, hairy last rostral segment of the new species suggests strongly a feeding adaptation, and parallels that of a North American Madia-feeding species in the same genus which is not, however, closely related.

Key words: South America, aphid, Uroleucon eumadiae, feeding adaptation

RESUMO

Uroleucon é um dos poucos gêneros de afídeos com espécies nativas da América do Sul. Neste trabalho, é descrita e ilustrada uma nova espécie do Chile, Uroleucon eumadiae sp. nov., coletada em duas espécies sul-americanas do gênero Madia (Asteraceae): M. sativa Mol. e M. chilensis (Nutt.) Reiche. São discutidos os caracteres morfológicos e aqueles utilizados para distinguir U. eumadiae de outras espécies relacionadas. O ultimo segmento rostral piloso desta espécie sugere uma adaptação alimentar, paralela a uma outra espécie que ocorre na América do Norte e que também se alimenta de plantas de do gênero Madia, mas que não é filogeneticamente próxima.

Palavras-chave: América do Sul, afídeo, Uroleucon eumadiae, adaptação de alimentação

Species of the aphid genus Uroleucon Mordvilko live on plants of the family Asteraceae, and are broadly distributed throughout the world (Blackman & Eastop 1984, Moran et al. 1999). The South American species are of special interest because they are one of the very few groups of the main aphid subfamily Aphidinae to have undergone recent speciation on native plants in southern temperate regions (Carvalho et al. 1998). Moran (1984) comments that biochemical, morphological, behavioral and life historical adaptations probably play a role in host specialization, but their relative importance is not clear. Interestingly, previous work has reported a positive correspondence between the length of the apical rostral segment and the hairiness of the host-plant (Moran 1984, 1986), suggesting a matching between aphid and host-plant traits. Such morphological specialization may occur secondarily with original benefits to specificity deriving from some other source (Moran 1984).

Uroleucon eumadiae sp. nov., was collected on Madia chilensis (Nutt.) Reiche and M. sativa Mol. (Asteraceae) in Chile. Both annual host plants show glandular trichomes on leaves and flower stems, and very sticky bracts of the involucre. Uroleucon eumadiae sp. nov., shows a long and hairy ultimate rostral segment. U. eumadiae is described and illustrated and the morphological traits by which this species may be distinguished from related ones are given.

Uroleucon eumadiae sp. nov.

Type material

Holotype. Alate viviparous female collected on Madia sativa Mol. at Farellones (Región Metropolitana, Santiago, Chile) 10-I-2001, W. L. Gonzáles leg., in The Natural History Museum (BMNH; London, United Kingdom).

Paratypes. Three apterous viviparous females collected on Madia chilensis (Nutt.) Reiche at Farellones (Región Metropolitana, Santiago, Chile) 21-XI-2000, W. L. Gonzáles leg.; 19 apterous viviparous females and one alate viviparous female collected on M. sativa at Farellones (Región Metropolitana, Santiago, Chile) 08-V-2000, W. L. Gonzáles leg.; 24 apterous viviparous females and 19 alate viviparous female collected on M. sativa at Farellones (Región Metropolitana, Santiago, Chile) 14-I-2001, W. L. Gonzáles leg.; 22 apterous viviparous females and 22 alate viviparous females collected on M. sativa Mol. at Farellones (Región Metropolitana, Santiago, Chile) 10-II-2001, W. L. Gonzáles leg.; collections of The Museo de Historia Natural (Santiago, Chile), Universidad Nacional de Córdoba (Córdoba, Argentina) and BMNH.

Description

Apterous Viviparous Female. Color in life is shining green. Cleared specimens with head pale, antennal segments I and II dusky; remainder of antenna except small basal part of segment III dark. Rostrum same color as antennal segments I and II, except apical rostral segment brown to almost black. Thorax pale. Legs with coxae and trochanters pale, femora with basal third to half pale, remainder dark brown; tibiae smoky, gradually becoming darker toward distal apex; tarsi similar in color to apical tibiae and antennal flagellum. Abdomen pale with peritrema brown; dorsum with distinct scleroites at the bases of the hairs, some of them pale dusky to transparent. Siphunculi mainly rather pale with dusky apices; some specimens with them lighter brown at base gradually changing to a dark brown toward apex, or they can be entirely dark brown. Cauda and anal plate pale dusky, and genital plate slightly paler.

Morphological Characters. Head smooth with antennal tubercles developed, divergent, about two-thirds as long as antennal segment I; and median frontal tubercle small (Fig. 1a, Table 1). Cephalic hairs have indistinct apices. Antennal segment I smooth, faint imbrication on II; III: without imbrications on zone around the secondary rhinaria; IV: faintly imbricated on base and more strongly so on segments V and VI. Proportions of segments III – VI = 100 (III): 65–87 (IV): 58–69 (V): 20–23 (base of VI) + 87–88 (proc. term.); processus terminalis 2.65–4.00 times as long as base of antennal segment VI. Secondary rhinaria 8–26, irregularly scattered on nearly the whole length of antennal segment III (Fig. 1b). Antennal hairs of segment III with indistinct apices. Longest hair 0.87 to 1.35 times as long as basal diameter of segment III (0.028 – 0.042 mm). Rostrum reaching to third coxae; ultimate rostral segment 1.56 – 1.81 times as long as segment II of hind tarsus, and bearing 18 - 24 accessory hairs. Prothorax with lateral tubercles, which have height 0.50 of length of adjacent hair. Hind femora and hind tibiae; 0.30 – 0.43 and 0.51 – 0.79 times as long as body length, respectively; ratio hind tibiae / femora 1.77 – 1.94. First tarsal segment with 5 hairs (Fig. 1h). Lateral abdominal tubercles present on abdominal segments II – IV, some of which are distinctly lobulate (Fig. 1f). Dorsal abdominal hairs with indistinct apices, and sometimes arising from small dark sclerites; usually four hairs (rarely five) dorsally on abdominal segment VIII: 0.050 – 0.070 mm. Siphunculi slightly enlarged at base, otherwise cylindrical; reticulated distally (0.17 – 0.26 of siphunculi length), and remainder imbricated to almost smooth on basal portion, about 0.20 – 0.29 of the body length, 0.77 – 1.07 times as long as antennal segment III, 1.28 – 1.56 times as long as cauda. Cauda, slender and acuminate, shows 10 – 26 hairs on apical two-thirds (Fig. 1g).

Alate Viviparous Female. Cleared specimens differ from apterae in having pale brown head and thorax. The abdomen is pale, except for light brown marginal sclerites.

Morphological Characters. Antennal segment III with basal diameter 0.028 – 0.036 mm, 0.88 – 1.15 times as long as the longest hair. Proportions of segments III VI = 100 (III): 70 – 85 (IV): 61 – 72 (V): 18 – 22 (base of VI) + 76 – 89 (proc. term.); processus terminalis 4.00 – 4.67 times as long as base of antennal segment VI. Antennal hairs with indistinct apices, on segment III about 0.028 – 0.040 mm long. Secondary rhinaria 29 – 50, irregularly distributed over nearly entire length of antennal segment III (Fig. 1c). Ultimate rostral segment 1.71 – 1.94 times as long as segment II of hind tarsus, and bearing 22 – 24 accessory hairs (Fig. 1d). Hind femora and hind tibiae 0.35 – 0.42 and 0.67 – 0.82 times as long as body length, respectively. Ratio hind tibiae / femora 1.92 – 2.03. Siphunculi reticulated distally (0.24 – 0.31 of the siphunculi length) (Fig. 1e), 0.21 – 0.28 of the body length, 0.81 – 0.90 times as long as antennal segment III, 1.54 1.70 times as long as cauda. Other characters like apterae specimen.

Host Plants and Life Cycle.U. eumadiae was collected on M. sativa and M. chilensis in the following locations: Farellones, El Cerro "El Roble", and the Parque Nacional Río Clarillo (Región Metropolitana, Santiago, Chile), during the spring and summer seasons (2000 and 2001) by W. L. Gonzáles. These annual host-plants have glandular trichomes on the leaves and flower stems. M. sativa shows an amphitropical distribution between South America (Chile and Argentina) and North America (Raven 1963; Zardini 1992); M. chilensis is a Chilean endemic (Hoffman et al. 1997). Other Madia species are in North America (Kyos et al. 1990).

U. eumadiae colonizes the inflorescences and stems of its host plants and after the flowers are in bloom it may also be found among the sticky bracts of the involucre. This species establishes dense colonies that often cover several stems. The sexual forms are not yet known.

Discussion

Both aptera and alate female of this new species can easily distinguished from all other South American Uroleucon by the long hairy ultimate rostral segment; 0.21-0.24 mm, bearing 18-24 accessory hairs, whereas no other species has simultaneously an ultimate rostral segment longer than 0.22 mm, with more than 10 accessory hairs. Only Uroleucon muermosum (Essig) has ultimate rostral segment 0.23-0.27 mm long but with 6-10 accesory hairs (Carvalho et al. 1998). The only other species of Uroleucon living on Madia is U. madia (Swain 1919), which belongs to the subgenus Lambersius. It was first described as a color variety of U. rudbeckiae (Fitch) in California (North America). According to Swain (1919), U. madia is dark-green, slightly pruinose in life; the alate viviparous female has the processus terminalis about six times as long as the base of VI; antennal segment III has 25 – 35 secondary sensoria; the rostrum reaches to the second coxae, the siphunculi are 0.91 mm long, slightly tapering, black except for the basal one-third which shows the same color as the abdomen, apical one-fifth reticulate; and the cauda is 0.45 mm long, about one-half as long as the siphunculi. U. eumadiae is shining green in life; the alate viviparous female has the processus terminalis 4.00–4.67 times as long as the base of VI; antennal segment III has 29 – 50 secondary sensoria; the rostrum reaches to the third coxae; the siphunculi are 0.49 – 0.65 mm long, apical one-quarter to one-third reticulate; and the cauda is 0.31 – 0.42 mm long. According to Robinson (1986) the ultimate rostral segment of U. madia bears 14 – 18 accessory hairs, whereas U. eumadiae has 18 – 24.

U. eumadiae should currently be placed in subgenus Uroleucon (Uroleucon), as defined by such characters, as the reduced dorsal sclerotization and absence of antesiphuncular sclerites, despite the distinctly pigmented siphunculi, cauda and green color in life, which are untypical of this subgenus. Holman (1975) stated that the presence or absence of pigment in the cauda should not be considered as an absolute criterion in the classification of some groups of aphids, even though they may be a valuable guide to separate groups of species or subgenera which are uniform in other morphological and ecological characters. U. madia belongs to subgenus Lambersius according to Robinson (1986) and Remaudiere & Remaudiere (1997); nevertheless Carvalho et al. (1998) comments that this subgenus is not clearly defined and it needs to be reassessed, and that the endemic South American species of Uroleucon may form a monophyletic group on their own. It is interesting that eumadiae and madiae are evidently not closely related but converge in characters of the rostrum that allow them to feed on Madia.

Acknowledgments

We thank R.L. Blackman and E. Fuentes-Contreras for their valuable comments on an early draft of this manuscript. WLG was supported by a postdoctoral grant of FONDECYT (3040036) during the writing process.

Literature Cited

Received 22/IX/04. Accepted 22/XII/04.

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Publication Dates

• Publication in this collection
  14 July 2005
• Date of issue
  Apr 2005

History

• Received
  22 Sept 2004
• Accepted
  22 Dec 2004