Macrosiphum tonantzin Peña-Martínez, Muñoz-Viveros, and Jensen, 2019

Jensen, Andrew S., Martinez, Rebeca Peña-, Viveros, Ana Lilia Muñoz- & Rorabaugh, Jesse, 2019, A New Species Of Macrosiphum Passerini (Hemiptera: Aphididae) From Mexico On The Introduced Plant Pittosporum Undulatum Ventenat (Pittosporaceae), Proceedings of the Entomological Society of Washington 121 (1), pp. 39-53 : 42-51

Macrosiphum tonantzin Peña-Martínez, Muñoz-Viveros, and Jensen , new species

urn:lsid:zoobank.org:act:BF707440-40AF-4995-A043-DBCF41DD7A0F

( Figs. 1–14 )

Apterae.— Color: When alive, pale to bright green, the abdomen often characterized by a transparent whitish round spot in the center ( Figs. 1, 2 ). When macerated, antennae with joints dusky to brown on segments III, IV, and V, with VIa dark around the primary sensoria and with a.s. VIb mostly dusky and darkest in middle. Head pale. Rostral segment III light brown to brown, u.r.s. dark brown. Femora pale, sometimes dusky dorso-apically. Tibiae light brown at apex. Tarsi brown. Siphunculi pale with extreme apex sometimes dusky. Other body parts pale.

Morphology: Measurements of body, appendages, setae, etc. see Table 1. Antennae with segment I with a cluster of spinules or bi- or tri-cuspid ridges ventrally, concentrated near base, but sometimes scattered throughout ( Fig. 4 ); a.s. II entirely smooth; a.s. III ( Fig. 5 ) with small dense imbrications basally, remainder more or less smooth except a narrow strip of spinules on lateral margin where secondary sensoria would set, occasionally with faint imbrications near apex; a.s. IV–VI uniformly covered with imbrications ( Fig. 5 ); antennal setae blunt to slightly capitate. Head with medium-sized antennal tubercles ( Fig. 3 ), in carefully mounted specimens a small median tubercle is also evident; spinal tubercles absent; dorsum of head more or less smooth; dorsal setae narrowly blunt, tips slightly less prominent than on antennae; ventral and dorsal setae more or less the same shape; antennal tubercle with a patch of spinules medially ( Fig. 4 ), adjacent to a.s. I, composed of about 10–20 large occasionally bicuspid spinules; spinules absent ventrally on each side of mouthparts. Rostrum reaching metacoxae; segment II with stylet groove spinulated, segments III and u.r.s. without ornamentation; setae on rostrum pointed; u.r.s. long, with 22–29 accessory setae ( Table 1, Fig. 14 ). Prothorax with small lateral tubercles, spinal tubercles absent. Thorax with dorsum slightly wrinkled, setae blunt; setae on coxae and trochanters more or less pointed; femora with setae blunt, no ventral ones dramatically longer than others, ornamentation of spinules and small imbrications over apical ~½ to 2/3 anteriorly and ventrally, with just a few small imbrications posteriorly. Tibiae with setae blunt, ventral and dorsal setae about the same shape, metatibia with dorsal setae mostly longer than corresponding setae on pro- and mesotibiae; tibiae without ornamentation. Tarsi with 4–6 setae on segment I, pro-, meso-, and metatarsi may have 4, 5, or 6 setae on tarsal I; protarsal II with 4 pairs of dorsal setae, imbrications usually smooth but sometimes a few faint spinules present ( Fig. 13 ). Abdomen with tergum membranous, smooth; dorsal setae blunt to slightly capitate, ventral setae pointed; segments III–VI usually with small lateral tubercles. Siphunculi ( Fig. 12 ) with about 2–4 rows of indistinct apical polygonal reticulation, these apical imbrications with minute spinules, small spinulate imbrications more basally, becoming more or less smooth on basal ~¼. Cauda ( Figs. 6, 7 ) with setae more or less paired; dorsal ornamentation of ribbed and spinulate imbrications about 8–10 across width at middle; ventral ornamentation of large spinules in groups of 1–2. Tergites VII and VIII often with 1–2 faint spinal tubercles. Subgenital plate with posterior-marginal setae and 1 pair of anterior setae, occasionally with 1 posterior-marginal seta displaced anteriorly. Middle pair gonapophyses fused so that it appears there are 3 gonapophyses.

Alatae.— Color: When alive, bright pale green, thoracic plates, legs, and antennae brown. When macerated, antennae entirely brown except extreme base of a.s. III pale. Head dusky to brown, darkest around the ocelli. Rostral segment II dusky or brown, segment III brown, u.r.s. dark brown. Thoracic plates all brown. Femora pale at base, becoming dusky, then brown apically, darkest dorsoapically. Tibiae more or less entirely brown, with pale area in the middle. Tarsi brown. Siphunculi mostly pale, but sometimes dusky. Abdomen with lateral sclerites on segments II–V dusky to brown. Subgenital plate light brown. Cauda sometimes dusky. Other body parts pale.

Morphology: Measurements of body, appendages, setae, etc. see Table 1. Antennae with segment I usually with a small cluster of spinules ventro-laterally; a.s. II with a few big ridges ventroapically; a.s. III ( Fig. 8 ) with small dense imbrications basally, secondary sensoria large, with largest ones often having uneven edges ( Fig. 8 ); a.s. IV–VI uniformly covered with imbrications, interrupted when sensoria are present ( Figs. 9, 10 ). Head with medium-sized antennal tubercles; antennal tubercle with a patch of spinules medially, adjacent to a.s. I, composed of about 10–20 small spinules. Thorax with thoracic plates normal, wings full-sized, wing venation normal with media twicebranched; femora with setae narrowly blunt. Abdomen with segments III–VI usually with small lateral tubercles on lateral sclerites; lateral sclerites on segments II–IV spinulate on ventral half. Siphunculus more or less as in apterae ( Fig. 11 ). Cauda more or less as in apterae but generally narrower. Tergites VII and VIII usually without spinal tubercles. Otherwise as in apterae.

Alate males.— Color: When alive, reddish brown. When macerated, antennae entirely brown except extreme base of a.s. III pale. Head dusky to brown, darkest around the ocelli. Rostral segment II dusky or brown, segment III brown, u.r.s. dark brown. Thoracic plates all brown. Femora pale at base, becoming dusky, then brown apically, darkest dorsoapically. Tibiae more or less entirely brown, with pale area in the middle. Tarsi brown. Siphunculi mostly pale, but sometimes dusky. Abdomen with lateral sclerites and intersegmental muscle attachment plates on segments II–V dusky to brown. Cauda dusky. Genitalia brown. Other body parts pale. Morphology: Measurements of body, appendages, setae, etc. see Table 2. Head with medium-sized antennal tubercles; antennal tubercle with a patch of spinules medially, adjacent to a.s. I, composed of about 5–10 small spinules. Cauda very short and triangular, as is common in male Macrosiphum . Otherwise as in alatae.

Type material.— Holotype aptera: AJ8638, Mexico, Distrito Federal, Mexico City, Xochimilco, La Noria , ex Pittosporum undulatum , 10 October 2015, R. Peña (1, MEX.APH.080.0499). Paratype apterae: AJ8626, Mexico, Distrito Federal, Mexico City, Xochimilco , La Noria ( Coord . 19.277832, - 99.142417), ex Pittosporum undulatum , 20 July 2015, R. Peña (3, MEX.APH. 080.0499); AJ8627, Mexico, Distrito Federal, Mexico City, Xochimilco , La Noria , ex Pittosporum undulatum , 20 July 2015, R. Peña (3, ASJ); Peña7933, Mexico, Distrito Federal, Mexico City, Xochimilco , La Noria , ex Pittosporum undulatum , 20 July 2015, R. Peña (3 slides, 4 apterae, 1 to BMNH, 2 to MEX. APH.080.0499); AJ8639, Mexico, Distrito Federal, Mexico City, Xochimilco , La Noria , ex Pittosporum undulatum , 10 October 2015, R. Peña (1, ASJ); AJ8657, Mexico, Distrito Federal, Mexico City, Xochimilco , La Noria , ex Pittosporum undulatum , 28 January 2016, R. Peña (1, USNM); AJ8662, Mexico, Distrito Federal, Mexico City, Xochimilco , La Noria , ex Pittosporum undulatum , 28 January 2016, R. Peña (1, ASJ); AJ8674, Mexico, Distrito Federal, Mexico City, Xochimilco , La Noria , ex Pittosporum undulatum , 6 March 2016, R. Peña (1, MNHN). Paratype alatae: AJ8638, Mexico, Distrito Federal, Mexico City, Xochimilco , La Noria , ex Pittosporum undulatum , 10 October 2015, R. Peña (1, MEX.APH.080.0499); AJ8639, Mexico, Distrito Federal, Mexico City, Xochimilco , La Noria , ex Pittosporum undulatum , 10 October 2015, R. Peña (1, ASJ); AJ8657, Mexico, Distrito Federal, Mexico City, Xochimilco , La Noria , ex Pittosporum undulatum , 28 January 2016, R. Peña (1, USNM); AJ8675, Mexico, Distrito Federal, Mexico City, Xochimilco , La Noria , ex Pittosporum undulatum , 6 March 2016, R. Peña (1, ASJ); Peña7863, Mexico, Distrito Federal, Mexico City, Xochimilco , La Noria , ex Pittosporum undulatum , 14 February 2016, R. Peña (1 slide, 1 alata, MEX. APH.080.0499); Peña7933, Mexico, Distrito Federal, Mexico City, Xochimilco , La Noria , ex Pittosporum undulatum , 20 July 2015, R. Peña (1 slide, 1 alata, BMNH); Paratype males: AJ8662, Mexico, Distrito Federal, Mexico City, Xochimilco , La Noria , ex Pittosporum undulatum , 28 January 2016, R. Peña (1, ASJ); AJ8674, Mexico, Distrito Federal, Mexico City, Xochimilco , La Noria , ex Pittosporum undulatum , 6 March 2016, R. Peña (1, MNHN); Peña7863, Mexico, Distrito Federal, Mexico City, Xochimilco , La Noria , ex Pittosporum undulatum , 14 February 2016, R. Peña (1 slide, 1 male, MEX.APH.080.0499); Peña7864, Mexico, Distrito Federal, Mexico City, Xochimilco , La Noria , ex Pittosporum undulatum , 17 December 2015, R. Peña (1 slide, 1 male, MEX. APH.080.0499); Peña7869, Mexico, Distrito Federal, Mexico City, Xochimilco , La Noria , ex Pittosporum undulatum , 14 February 2016, R. Peña (1 slide, 1 male, MEX.APH.080.0499);

Slides containing all type specimens are clearly marked and highlighted with red ink.

Etymology.— The species is meant to honor the Nahuatl name for an Aztec mother goddess. For the purposes of zoological nomenclature, the name should be considered a random collection of letters without gender.

Biology and distribution.— So far this aphid is only known from a single site in Xochimilco area of southern Mexico City. Here, it lives throughout the year on the growing tips of ornamental trees of P. undulatum . The second and third authors have observed that P. undulatum is not a common plant in Mexico City, and the site where they find M. tonantzin is the only site they have seen this plant. Further, they note that Pittosporum tobira (Thunb.) W.T. Aiton is common in Mexico City but despite extensive searching they have not been able to find M. tonantzin feeding on it. The production of alate males starting in December, in the absence of oviparae, suggests that this aphid’s native biology may be heteroecious. The species is, however, so far not known from any native plants. For more discussion of host plant biology and relationships, see the Discussion below.

Remarks.—This aphid presented a conundrum as to its proper generic placement and its possible affinities to other known aphid species in North America and beyond. When M. tonantzin was first found, we and a few colleagues around the world corresponded about our thoughts on generic placement, the authors then studied all other genera of Macrosiphini listed in Blackman and Eastop (2018), and the consensus was that Macrosiphum was most appropriate. It is, however, not a typical Macrosiphum . The following features are unusual for Macrosiphum : siphunculi with few apical reticulations, these reticulations spinulate; tarsal segments I with 4–6 setae; fully membranous abdominal tergum in apterae (many North American species of Macrosiphum possess pale and sclerotized abdominal terga, many others do not); presence of a discrete patch of large spinules ventrally on each antennal tubercle; presence of a slight median frontal tubercle in apterae; presence of secondary rhinaria on antennal segment IV and sometimes V in alate viviparae. Most of these features can be found in species currently placed in Macrosiphum , but no other species possesses all of them. For example, several of the species of fern-feeding Macrosiphum have few to no apical reticulations on the siphunculi, including M. cyatheae (Holman) and M. clydesmithi Robinson. Spinulate reticulations on the siphunculi can be found in M. niwanistum (Hottes) . More than three setae can be found on tarsal segments I in M. tuberculaceps (Essig) , and the first author knows of an undescribed species of otherwise very typical Macrosiphum in western U.S.A. that normally has 5 setae on tarsal segments I. Admittedly, we are not aware of any other Macrosiphum species that has 6 setae on tarsal segment I. Two species of fern-feeding Macrosiphum sometimes have secondary sensoria on a.s. IV of alate viviparae: M. walkeri Robinson and M. dryopteridis (Holman) . We know of no other Macrosiphum in which alate viviparae have secondary sensoria on a.s. V. Some of the fern-feeding Macrosiphum possess a slight medial frontal tubercle.

Other possible generic placements we considered included Acyrthosiphon Mordvilko and Illinoia Wilson. The distinction between Macrosiphum and Acyrthosiphon is limited to the presence or absence of subapical reticulation on the siphunculi, a rule that has been disregarded in a few cases in which the evolutionary affinities clearly tied a species to Macrosiphum despite lack of reticulation. A key example of this is M. cyatheae (Holman) , which was originally described in Acyrthosiphon , but examination of it in the context of other North American fern-feeding Macrosiphum showed that the latter genus was the better choice (Jensen and Holman 2000). Interestingly, Acyrthosiphon cyparissiae (Koch) shares the unusual feature with M. tonantzin of having more than 5 setae on the first tarsal segments (5–7 setae, according to Hille Ris Lambers 1947), but differs in important ways that do not support placement of the two species in the same genus (e.g. a short u.r.s. and lack of any siphuncular reticulation in A. cyparissiae ). Illinoia is another genus that, taken as a whole, is separated from Macrosiphum by only one character: the subapical swelling of the siphunculi. There are, however, exceptions in both genera, i.e. species placed in Macrosiphum that have swollen siphunculi (e.g. M. parvifolii Richards , M. wilsoni Jensen , M. stanleyi (Wilson)) , and species placed in Illinoia that lack such swelling (e.g., Illinoia (Masonaphis) rhododendri (Wilson) , Illinoia (Masonaphis) menziesiae Robinson ). These genus placements were chosen due to apparent affinities of these species to more typical members of their genera. While M. tonantzin shares with many Illinoia the presence of more than 3 setae on tarsal segments I, it differs from Illinoia in important ways, such as its completely membranous abdominal tergum in apterae; Illinoia species have a sclerotized abdominal tergum in apterae, with the exception of the subgenus Oestlundia Hille Ris Lambers , species of which differ from M. tonantzin in several ways such as having very long and obviously swollen siphunculi. Ultimately, the lack of swelling of the siphunculi and the membranous tergum in M. tonantzin argue for its placement in Macrosiphum . We feel it is useful to draw attention to the ways in which M. tonantzin is similar to, and differs from, some of the species with which it shares unusual features. Such comparisons are meant to point out possible affinities that we know about, which might be helpful to future workers in this general group of Macrosiphini . Macrosiphum longirostratum Jensen and Holman shares with M. tonantzin an unusually long and setose u.r.s. and reduced reticulation on the siphunculi. These species differ in many ways, including the sclerotized tergum and more numerous secondary sensoria of the aptera in M. longirostratum , plus the presence of 4–6 setae on the first tarsal segments of M. tonantzin . Among the fern feeding Macrosiphum , M. miho Jensen and Holman is an example of reduced dorsal abdominal sclerotization, looking very similar to M. tonantzin in this regard and in the type of siphuncular reticulation. These species differ in numerous ways, including the much longer u.r.s. in M. tonantzin , and the shorter triangular cauda in M. miho . A species with siphunculi and head shape very similar to M. tonantzin is the fern-feeder M. adianti (Oestlund) , which differs from M. tonantzin in many ways including its very short u.r.s. and cauda. The species of fern feeders that tend to have secondary sensoria on the a.s. IV of alatae are M. walkeri Robinson and M. dryopteridis (Holman) . Like most other fern-feeders, these species differ from M. tonantzin by possessing sclerotized terga in apterae and short triangular caudas.

Moving away from fern-feeders, one finds in M. niwanistum (Hottes) a similar siphunculus in terms of overall shape and the tendency to have finely spinulate imbrications and reticulations apically. The two species also can have similar head shape in terms of a small median tubercle. There are numerous differences between these two species, including the much longer and setose u.r.s. and the more setose tarsal segments I in M. tonantzin . Among Macrosiphum of North America, only one is known to typically have 4 setae on tarsal segments I: M. tuberculaceps (Essig) . This might be interesting because the 4 setae are two lateral ones, plus two shorter peg-like setae between; most specimens of M. tonantzin also have two of these smaller peg-like setae. These two species differ in many ways, including abdominal sclerotization, siphuncular shape, shape of the u.r.s., etc.

Figures

Figs. 1, 2. Macrosiphum tonantzin. 1, Aphids crowded onto a young leaf of Pittosporum undulatum in early December, 2015; the reddish nymphs are males, while the green and pale green nymphs will be apterous and alate viviparae; photo credit: Pena-Martinez. 2, Close-up of a typical apterous vivipara and a few nymphs; photo credit: O. E. Hernández-Torres.

Figs. 3, 4. Macrosiphum tonantzin. 3, Head capsule and antennal segments I of aptera, dorsum. 4, Head capsule and antennal segments I of aptera, ventral surface.

Figs. 5–7. Macrosiphum tonantzin. 5, Antenna and foreleg of aptera. 6, Cauda of aptera, dorsum. 7, Cauda of aptera, ventral surface.

Figs. 8–14. Macrosiphum tonantzin. 8, Alata a.s. III. 9, Alata a.s. IV. 10, Alata a.s. V. 11, Alata siphunculus. 12, Aptera siphunculus. 13, Aptera metatarsus. 14, Aptera u.r.s.