PHYLOGENY OF THE WORLD SPECIES OF MUSTHA AMYOT AND SERVILLE (HEMIPTERA: PENTATOMIDAE: PENTATOMINAE: HALYINI) BASED ON MORPHOLOGICAL CHARACTERS.
A phylogenetic analysis of all 10 species of the Palaearctic genus Mustha Amyot and Serville is presented here, together with a key. Thirty morphological characters were analyzed using parsimony, including characters of the internal and external male and female genitalia. Using the genus Orthoschizops as an outgroup, only a single most-parsimonious shortest tree resulted. Two species (izmirensis and serratta) were plesiomorphic in the tree. Although only with weak bootstrap support, three distinct clades were evident. A relatively plesiomorphic clade consisted of baranovi, longispinis, gigantea and vicina; the second contained two species, incana and morgani; and the third clade also contained two species, spinosula and spinosus.
Key words: Phylogeny Mustha, Halyini, PentatomidaeINTRODUCTION
Mustha Amyot and Serville (1843) is one of the richest Palaearctic genera of the tribe Halyini, with ten species described: baranovi Kiritshenko 1952, M. gigantea Horvath 1906, M. incana StAl 1876, , M. izmirensis Memon and Ahmad 2009, , M. longispinis Reuter 1890, , M. morgani Horvath 1906, , M. serrata Fabricius 1974, , M. spinosula Lefebvre 1837, , M. spinosus Ahmad and Kamaluddin 1984 and, M. vicina Hoberlandt 1995. The genus is widely distributed throughout the world, in Pakistan, Afghanistan, India, Tajikistan, Iran, Egypt, Syria, Israel, Jordan, Turkey, Eastern Europe and South Africa. Of the ten species, six had been described by 1952: the three most recently described species are: spinosus (Abasi and Ahmad 1971) from Pakistan, vicina Hoberlandt 1995 from Iran and izmirensis Memon and Ahmad 2009 from Turkey. M. spinosus was initially misidentified and placed in the genus Orthoschizops Spinola (1850) by Abbasi and Ahmad (1971), based only on a female specimen. Ahmad and Kamaluddin (1984) transferred O. spinosus to the genus Mustha without mentioning that it was the first record from Pakistan of either genus. Hoberlandt (1995) synonymized spinosus with gigantea Horvath, but here we have maintained its independent status, following Ahmad and Kamaluddin (1984): they described this species on the basis of both male and female specimens, including describing and illustrating the male genitalia. M. gigantea is based only on female specimens. Many Mustha species resemble one another in external characters, and we do not consider this an adequate basis for synonymy without information on the genitalia. Abbasi and Ahmad (1971) did describe the external genital plate of the female, but this is almost identical in all Mustha species. Rider (2006) followed Hoberlandt (1995) by including only eight species in his catalogue, excluding spinosus.Despite having such a wide distribution, most species of Mustha vary little in external characters (e.g. colouration, shape and length of antennal segments, length and width of head and pronotum), even though many species have been described only on the basis of external character, particularly by older authors (Lefebvre1837, Fabricius 1874, StAl 1876, Reuter 1890, Horvath1906, Kiritshenko 1952). Some contemporary workers did some work on the internal and external male genitalia in establishing their new species, but while revising the genus they ignored female external and internal genitalia: for example, Hoberlandt (1995) and Ahmad and Kamaluddin (1984), who gave descriptions of the male genitalia of spinosula and spinosus, but mentioned female specimens including the holotype and paratype in the material they examined. Memon and Ahmad (2008) were the first authors to describe and illustrate the internal female genitalia.While revising the Halyini, Hoberlandt (1995) recorded six Mustha species (serrata, gigantea, baranoui, spinosula, morgani and incana) but described only his new species Mustha vicina from Faras (S. Iran) and redescribed M. longispinis along with a detailed synonymy. In the description he described the male genitalia, but nothing about those of the female. He keyed out seven species of Mustha, and suggested the synonymy of M. spinosus with gigantea. In drawings he showed only the outer margins of the head, pronotum and abdomen of three species (vicinia, serrata and longispinis), while providing illustrations of the male pygophore and paramere only of his new species vicina. This was the first detailed work on the genus Mustha.In the Halyini, Mustha is known for a set of unique characters, i.e. the presence of very distinct spines on the lateral margins of the entire body (head, pronotum, abdomen), and also on the posterior margin of the eighth paratergite of the female genitalia. Species of Phricodus and Orthoschizops also have dentition on the head and pronotum, but none has spines on the connexiva and the eighth paratergite, although Phricodus species have a single small spine in the middle of the eighth paratergite.Taxonomic and systematic work on the genus by various workers in the last one hundred years has included and/or transferred many species, but these studies were mostly regional or country-based. Phylogenetic work is lacking. Furthermore, no-one has described the internal female genitalia except Memon andAhmad (2008) in their new species M. izmirensis. Theyonly described and illustrated the spermathecal bulb, while not describing the external terminalia because these were damaged in the paratype. Although Memon and Ahmad (2008) did estimate the phylogeny of nine species and gave a key to these nine species, the phylogeny was not numerically based, and they ignored M. spinosus in the key even though it was described from Pakistan.The goal of the present study is to estimate the phylogenetic relationship of all ten known species of the genus Mustha using adult morphological characters, including the male and female genitalia. Characters were extracted from the literature and by observation of material, including the holotype and paratype of the species.
MATERIALS AND METHODS
All known species of the genus Mustha were included: baranovi Kiritshenko 1952, gigantea Horvath1906, incana StAl 1876, izmirensis Memon and Ahmad2009, longispinis Reuter 1890, morgani Horvath 1906, serrata Fabricius 1974, spinosula Lefebvre 1837 and vicina Hoberlandt 1995. We examined the phylogenetic relationships among these species using adult morphological characters, including male and female genitalia. The characters were extracted from the literature and by observation of material, including the holotype and paratype of all taxa. Literature data were essential in some cases: for example, baranovi, longispinis and morgani were described by old authors and then catalogued or keyed by current authors (e.g. Hoberlandt 1995, Rider 2006). We used both presence/absence coding and true multistate characters, the latter because of the structural diversity in some external morphological characters and particularly in male genitalia (usual in most halyine species). In total 30 characters were used (Table 1). As far as is known, most are constant among individuals within species. In the data matrix (Table 1), baranovi, longispinis, serrata and morgani have missing data for twelve male and female genital characters, gigantea for seven male genital and spinosus for three female genital characters.The genus Orthoschizops was chosen as the outgroup: this genus has dentition on the anterior margin of the head, distinct dentition on the entire lateral margin of the pronotum (although few in comparison to Mustha), the humeral angles are broad and spinose (usually with two spines) and to some extent there is also a resemblance in the male pygophore. Mustha is closer to Orthoschizops than Phricodus in having five-segmented antennae, the 1st antennal segment is distinctly shorter than the head apex, the second is a little shorter or longer than the third, the labium reaches or exceeds the level of the hind coxae, and the female spermathecal bulb is with processes. In an analysis of many of the genera of Halyini (Memon et al., 2011), Orthoschizops was placed very close to Mustha.The shortest tree was found with Paup version4.0 (Swofford, 2003) under the parsimony criterion, using heuristic search with the default settings; all character states were treated as unordered. There was only one single most-parsimonious tree; we used the bootstrap command on this tree to assess confidence in each branch.
Cladogram: The single most parsimonious tree resulting from the data is shown in Fig 1. The only branch with appreciable bootstrap support is that leading to node 2 (see Fig 1), perhaps because only 12 characters were parsimony informative. The character-state changes of this tree are listed in Table 2.With Orthoschizops as an outgroup, izmirensis is placed closest to it, and is clearly very different from the other species; serrata is also placed in a fairly isolated position. Other recognizable groups of species are the gigantea group (baranovi, gigantea, vicina and longispinis), the incana group (incana + morgani) and the spinosula group (spinosula + spinosus).
Characters: In total 30 characters were defined and scored (Table 1); 18 were parsimony-uninformative but are included because they are mostly male and female genital characters important as diagnostic characters for the species. Character state 0 in all cases is the state scored for Orthoschizops.1. Head and pronotum colour: (0) ochraceous, punctures reddish brown in the form of light and dark stripes, clypeus pale; (1) unicoloured black/blackish-brown, punctures black, thick, with a small ochraceous fascia on posterior margin; (2) brown, with dark-brown punctures.The colour of the head is almost the same in all Mustha species (1) except gigantea which is a bit different in this trait (2).2 Colour of hemelytra: (0) ochraceous, with reddish- brown punctures; (1) black or dark-brown, with very few indistinct ochraceous spots; (2) reddish-brownwith many scattered ochraceous spots; (3) yellow;(4) yellowish-brown with light-brown punctures; (5) light-brown with orange-ish apical margin; (6) corium reddish-brown with whitish hair.In Mustha species, the hemelytra is the only body part which has variation in the colour pattern: the group of four genera, baranovi, izmirensis, vicina and serrata have state (1); spinosula and spinosus with state (2); longispinis (3); gigantea (4); incana (5); morgani (6)3 Colour of scutellum: (0) yellowish ochraceous, punctures reddish, light and dark stripes, apical lobe lighter, with a few scattered spots; (1) black or dark- brown, apical margin ochraceous; (2) light-brown with dark-brown punctures, with a very small central ochraceous fascia at the base.Like the head and pronotum, the colour of the scutellum is dark and looks the same in almost all species (1), but gigantea has a different pattern, light-brown with dark-brown punctures, and a very small central ochraceous fascia at the base (2)4 Colour of connexiva: (0) brownish; (1) dark-brown or black; (2) black with exterior margin along whole length yellow.The connexiva is unicoloured and looks the same in all Mustha species (1) apart from longispinis, the only species in which the connexiva has a yellow exterior margin (2)5 Shape of head. (Fig. 3): (0) three-quarters of head only very slightly narrowed, nearly parallel-sided; (1) parallel-sided on posterior part, anterior part gradually tapering upward; (2) gradually tapering upward along whole length; (3) sub-triangular, conspicuously narrowed along whole length; (4) head sharply narrowed towards apex, triangular in shape.The shape of the head is almost rectangular in vicina and serrata (0) but in serrata the apex is sub-acute rather than broad as in vicina (see Fig. 3); most Mustha species are either state 1 or 2, with Orthoschizops having state 1 ; gigantea and longispinis (3); incana (4).6 Ratio of head length and width: (0) slightly longer than broad; (1) distinctly longer than broad.In almost all species of Mustha, the length of the head is slightly longer than wide (0) except gigantea, which has head distinctly longer than wide (1), sharing this trait with the outgroup Orthoschizopsand many other halyine genera (1).7 Shape of lateral margins of head: (Fig. 3) (0) straight; (1) moderately round; (2) laterally slightly elevated.Most of the species have state (0); in group of three species, baranovi, gigantea, and longispinis, it is modified (1); and in vicina this state is more modified (2).8 Shape of dentition on lateral margin of head: (Fig. 3) (0) distinct/ indistinct small dentine may or may not present only on anterior part of head; (1) large, triangular, distinct dentine present only on anterior part; (2) small dentine on entire margin; (3) entirely armed, usually with long or short spines.This trait is diagnostic and constant in all Musthaspecies, but with variation in number and shape: it distinguishes Mustha from almost all other halyine genera and species. Among Mustha species, vicina is the only one with few denticles only on the anterior part (1); in serrata it is little more modified (2); but all remaining species have very well developed large and/or small spines on the entire lateral margin (3).9 Number of teeth on lateral margins of head: (Fig. 3) (0) 3-4 distinct or indistinct teeth on anterior part of head; (1) long distinct denticles on anterior part; (2) entirely finely irregularly dentate; (3) entirely armed with 7-8 distinct upwardly directed spines; (4) entirely armed with 10 or more distinct upwardly directed spines.The presence of denticles on the lateral margin of the head is a constant for all species, but their number is variable: vicina has only a few (1); in serrata they are small, but on the entire lateral margins (2); of the remaining eight species, baranovi, longspinis, spinosula, izmirensis and spinosus have seven to eight denticles (3); but gigantea, longispinis and morgani have greater numbers with more than ten spines (4).10 Width between paraclypeal lobes: (fig. 3): (0) apical part widely separated from each other; (1) entirely enclosing clypeus.This character divides Mustha species in two groups, spinosula and izmirensis with state (0); all remaining species with state (1).11 Ratio of length and width of pronotum: (0) twice as broad as long; (1) transverse, not more than 2.3 times as broad as long; (2) very broad, always more than 2.9 times as broad as long. The pronotum length-width ratio is almost constant in all species (1) except longispinis (2).12 Shape of lateral margins of pronotum: (Fig. 4 A-E) (0) entirely armed, but with few long and some small denticles; (1) usually armed with moderate-to-long spines.The presence of spines on the lateral margin of the pronotum is constant and a distinguishing character of the genus Mustha, separating it from other genera of Halyini (1). Two other genera, the outgroup Orthoschizops and Phricodus, share this trait with Mustha, but in comparison to Orthoschizops, all Mustha species have very modified spines on the lateral margins.13 Shape and number of teeth of lateral margins of pronotum: (Fig.4 A-E) (0) usually 4-6 long denticles irregularly arranged, with gaps, and a few small denticles in between; (1) with 10- 11 spines of medium size; (2) with 12 irregularly arranged spines; (3) with 13-14 irregularly arranged spines; (4) 15 long acute spines of almost equal size; (5) 15-16 broadly triangular spines of unequal size; (6) with 19 mostly long, acute spines; (7) 21-22 small and unequal spines.The shape and number of pronotal spines is variable among species: vicina (1); baranovi (2); gigantea (3); longispinis (4); a group of four species (morgani, spinosula, spinosus and serrata) with state 5; izimirensis (6); and incana with the largest number of spines of unequal size (7).14 Shape of humeral angles: (Fig.4 A-E) (0) ) less thick and smooth, entirely spinose (1) broad, thick, a little elevated, entirely spinose; (2) distinctly produced laterally, more or less elevated upward, usually with two dentine, apical margin straight or concave.This trait is constant in most species (0); but there is a group of three species (gigantea, vicina and spinosus) with state (1).15 Shape of lateral margins of corium: (Fig. 4F-J) (0)sinuate; (1) with 3-6 short and long acute spinesThis state is constant in all species with little variation in shape and size (1).16 Shape of lateral margins of abdomen: (Fig. 4F-J) (0)sinuate; (1) armed with distinct dentine / spinesThe presence of spines on the lateral margin of the abdomen is constant in all species, and is the most diagnostic character of Mustha within the Halyini.17 Shape, size and number of spines on each connexivum: (Fig. 4F-J) (0) spines absent; (1) withbackwardly directed flat teeth, five on eachconnexivum; (2) with five comb-like thin spines of equal length; (3) usually five spines of medium size on each connexivum; (4) with 5-6 long spines on each connexivum; (5) ten short upwardly directed teeth on each connexivum.This state has modifications among the species of Mustha; serrata (1); vicina (2); half of the species of the genus (baranovi, morgani, spinosula, izmirensis and spinosus) with state (3); gigantea and longispinis (4); and incana, with a more modified trait with ten spines on each connexivum (5). 18 Length of body: (0) 13.5- 16.6; (1) 17.3-18.7 mm; (2) 19.23 - 19.9 mm; (3) 21 mm; (4) 22-25 mm; (5)28-35 mm.All Mustha species are larger in size than most halyine species, but variation occurs in the size among species: longispinis and vicina (1); incana and izmirensis (2); serrata (3); baranovi, morgani, spinosula and spinosus (4); gigantea is the largest of the species with a bodylength of 28-35 mm (5).19 Shape of dorso-posterior cavity of pygophore: (Fig.5A-C) (0) deep, rounded, with a broad, sclerotized, triblobate median projection; (1) shallow, without a median projection; (2) deep, with a small conical median projection; (3) relatively small but broad, distinctly depressed in the middle, the median projection with a sub-acute apex; (4) broad, long, distinctly bilobed median projection with lobes rounded at the apical margin; (5) broad, much longer and slightly depressed at apex.Among species where the male is known, izmirensis is the only species in which dorsoposterior cavity is without a median projection (0); the remaining species have a very well-developed median projection, vicina (2); spinosus (3); spinosula (4); incana (5).20 Shape of ventro-posterior cavity of pygophore: (Fig.5A-C) (0) relatively shallow median excavation, with small rounded triangular projections on the sides; (1) usually distinctly V-shaped with smooth lateral margin, without a median excavation; (2) shallow, with distinct and narrow U-shaped median excavation, with triangular lobes on sides ofexcavation; (3) shallow cavity with broad, roundedmedian excavation and triangular lobes on sides, lateral margin sinuate; (4) shallow cavity with deep V-shaped median excavation.This trait has some variation among species: spinosula (1); izmirensis (2); spinosus (3); incana (4).21 Shape of lateral lobes of pygophore: (Fig. 5A-C) (0) a little produced, apex rounded; (1) slightly broad, not produced, apical margin straight; (2) slightly produced, apical margin rounded; (3) narrow, produced upward with apex rounded and slightly notiched in the middle; (4) produced like a separate lobe with distinct demarcation, tip concave with acute lateral apices.Out of five species, baranovi, gigantea, longispinis, morgani and serrata have missing data in the literature while gigantea is a species based on only on females. Among remaining species this trait has a little modification, incana (1); vicina (2); spinosula and spinosus (3); but it is very distinct in izmirensis in which lateral lobes produced with distinct demarcation, apex concave with acute lateral apices. (4).22 Shape of paramere: (Fig. 5D-H) (0) L-shaped, without inner process; (1) F-Shaped, with a well- developed inner process, with long golden hairs on the upper margin.Izmirensis shares this trait with the outgroup Orthoschizops (0); all other species have a very well- developed inner process of stem (1).23 Shape of paramere stem: (Fig. 5D-H) (0) long and broad, sometimes with a small triangular inner spine; (1) short, narrow, with very indistinct inner spine; (2) short, relatively broader, outer margin rounded, inner process present at base, long, finger-like, basal part semi-sclerotized, apical part sclerotized and conical; (3) long, broad, somewhat rectangular, outer margin straight, inner process broad, apical margin, tapering downward, semi-sclerotized; (4) long, thin, with outer margin roundish, inner process sharply triangular, occurring at the middle of the stem; (5) long, outer margin straight, inner process large, thumb-like, apex subacute.Like other halyine species, this character plays a vital role in identifying Mustha species; in all Mustha species the stem has a very well-developed inner process with long golden brown hairs on upper side, except izmirensis, which has a thin small stem with an indistinct spine (1); incana (2); spinosus (3); vicina (4); spinosula (5).24 Shape of paramere blade: (Fig. 5D-H): (0) elongated, apex little produced, ridge area very distinct, upper margin slightly rounded, lower tapering downwards; (1) blade as narrow as stem, apex slightly produced like small spine; (2) somewhat rectangular, upper margin and outer margin straight, apex broad with apical margin a little notched (3) narrow, curved and sharply tapering towards apex, a little rounded projection on the upper margin, resembling a bird's head; (4) narrow, elongated, ridge area distinct, apex broad with apical margin straight, tapering downwards; (5) short, somewhat square, upper margin roundish, apical margin concave.The shape of the paramere blade is important in diagnosing individual halyine species and genera; this trait is very modified and variable in all Mustha species; izmirensis (1); incana (2); spinosula has unique blade, like a bird's beak (3); spinosus (4); and vicina with state (5).25 Shape of vesica: (0) straight, tube-like or slightly zigzag; (1) distinctly curved.This character is invariable and constant in all Musthaspecies (1).26 Shape of posterior margin of first gonocoxae: (0)rounded; (1) distinctly lobed at inner angle; (2) oval.Spinosula and spinosus share this trait with the outgroup Orthoschizops (0); gigantea and spinosus (1); incana and vicina (2). 27 Shape of posterior margin of second gonocoxae; (0) almost straight (1) slightly concave; (2) distinctly rounded.The posterior margin of the second gonocoxae has very little modification among the species: spinosula and spinosus (1); gigantea and incana (2)28 Posterior margin of female eighth paratergite; (0) smooth; (1) entire posterior margin armed with four spines; (2) entire posterior margin armed with sixspines.The presence of spines on the posterior margin of the eighth paratergite is a constant and unique character among all species of Mustha - usually there are eight spines (1); gigantea and spinosus have twelve spines (2).29 Length of ninth paratergite: (0) equal to eighth; (1) distinctly shorter than eighth, almost equal to proctiger.Like most halyine species, all Mustha species have state(1).30 Shape of spermathecal bulb processes: (Fig. 6A-E) (0) two finger-like processes; (1) three finger-like processes of unequal size; (2) three processes, two finger-like and one thick, forked at apex; (3) three processes, one long, reaching to half the length of first flange, bent at apex, second shorter, and third very short, highly sclerotized; (4) three processes, one very long, reaching to three-quarters of first flange and bent at apex, 2nd shorter, finger-like, 3rd very short.Like other halyine species, the spermathecal bulb processes is a variable trait in different species: incana (0); izmirensis (2); vicina (3); gigantea (4)
Key to the species of the genus Mustha Amyot andServille1. Head nearly parallel-sided, almost rectangular,apex broad anterior part of lateral margins of head with 4-6 irregular-shaped but distinct dentine; lateral margins of pronotum with eleven unequal long acute spines; margins of connexivum with comb-like thin spines of equal length; dorsoposterior cavity of male pygophore with small conical median projection, ventroposterior cavity shallow with broad roundish median excavation and triangular lobes on sides; spermathecal bulb with three processes, one short, highly sclerotized, a second a little longer, semi-sclerotized and a little bent at apex, and the third thick, very long, reaching middle of first flange M. vicina Hoberlandt Head distinctly narrow at anterior part, tapering upward along whole length, more or less triangular with sides slightly rounded or sharply triangular, entire lateral margins of head armed with very distinct dentine, lateral margin of pronotum with more spines; male pygophore not as above, spermathecal bulb with two or three processes with little variation in shape and size22. Paraclypeal lobes apically wider apart, leaving clypeus free3 Paraclypeal lobes entirely enclosing clypeus43. Pronotum with sixteen regularly arranged spines; corium with sparse very small dentine; dorsoposterior cavity of male pygophore with broad bilobed median projection, ventroposterior cavity distinctly v-shaped, lateral lobes of pygophore produced with apex a little depressed, paramere stem broad,elongated with well-developed inner process, bladerelatively thin bend, anterior part acutely tapered with small round projection on upper margin, spermethecal bulb with three finger-like processes M. spinosula (Lefebvre) Pronotum with nineteen long spines, some of them relatively short; corium with six short denticles of unequal size; dorsoposterior margin of pygophore without median projection, ventroposterior margin with U-shaped median excavation and triangular lobes on sides, lateral lobes prominent with distinct demarcation, apical margin depressed with acute apices, parameral stem very thin, without an inner process, blade as thin as stem, with apex a little produced like a thin spine; spermathecal bulb with three processes, two thin and finger-like, one thick, forked at apex izmirensis Memon and Ahmad. 4. Head sub triangular, lateral margins moderately round, with seven to eight spines.5- Head distinctly triangular, lateral margin almost straight with ten or more spines.85. Pronotum trapezoid, 2.9 times as broad as long, lateral margins, straight, flattened and distinctly raisedwith fifteen long, acute, upwardly projecting spines ofunequal length; costal margin of hemelytra yellow, callus with three short stout yellowish teeth, connexiva black, with exterior margin along whole length yellow, moderately raised, armed with 5-6 teeth on each connexivum M. longispinis Reuter- Pronotum transverse, no more than 2.3 times as broad as long; costal margin of hemelytra and connexiva entirely black or dark brown; teeth on connexiva not as above. 66. Head margins moderately round along the whole length; pronotum 2.3 times as broad as long; hemelytraand connexivum, unicoloured, entirely black or dark brown without any yellow spots, 7- Lateral margins of head almost straight with seven upwardly directed spines, hemelytra reddish-brown with some scattered yellow patches; pronotum twice asbroad as long, with twelve spines; dorsoposterior cavityof male pygophore with broad, medially depressed projection, ventroposterior cavity medially notched and with sinuate margins, lateral lobes broad with apical margin a little depressed in middle, paramere stem short relatively narrow with very prominent conical-shapedinner process, blade thin long with apex acute.M. spinosus Abbasi and Ahmad7. Lateral margins of head irregularly dentate with small teeth along whole length; lateral margins of pronotum regularly arranged with 19 flat teeth; each connexivum with five backwardly directed flat teeth M. serrata (Fabricius)- Lateral margins of head with eight distinct spines along whole length; lateral margins of pronotum with 12 irregularly arranged spines; each connexivum with five irregularly arranged spines M. baranovi Kiritshenko8. Lateral margins of head straight, spines stout, present along whole length; lateral margins of pronotum straight with 15-16 medially long acute spines; corium reddish-brown with short dense depressed whitish hair, M. morgani Horvath- Lateral margins of head a little rounded; lateral margins of pronotum not as above, corium not reddish- brown and without short dense whitish hair 99. Head relatively broad at apical part, lateral margins with 11 spines, labium extends to the metacoxae; lateral margins of pronotum slightly elevated with 18-21 short upwardly directed spines of medium size; labium just extending in between meso thorax, each connexivum with nine short broad dentine, spermathecal bulb with two finger-like processes, one short and one relatively longer, M. incana Stal- Head sharply triangular, lateral margins with ten spines; labium extending to third abdominal sternum, lateral margins of pronotum with 13 acute spines of unequal size; each connexivum with five long acute spines; spermathecal bulb with three processes, one reaching to 3/4 of first flange, bent at apex, second short and curved, third very short, finger-like and highly sclerotized M. gigantea Horvath.
Table 1 Character table for characters scored on taxa, and reconstructed on the cladogram of Figure
The morphological characters and analysis of this study indicates that all species have characters which distinguish the genus from almost all other genera of Halyini: for example, the paraclypei are distinctly longer than clypeus; the presence of spines on the entire lateral margin of the head, pronotum and abdomen (the number and shape of spines is variable among species); the humeral angles entirely spinose; and the entire posterior margin of the eighth paratergite with distinct acute spines. Although Mustha shares the head and pronotum traits (although in slightly different form) with two other halyine genera Orthoschizops and Phricodus, neither has spines on the abdomen: Phricodus has just a single small tooth in the middle of the posterior margin of the eighth paratergite, while Orthoschizops has no teeth or spines.In our analysis, several nodes of the single final tree of Fig. 1 are supported by multiple apomorphies. The separation of the outgroup Orthoschizops from all species of Mustha is supported by almost all character-state changes of the characters scored (Table 2).Our tree indicates that the two most plesiomorphic species are izmirensis and serrata. M. izmirensis has many unique characters, particularly in the male genitalia. It is the only species of Mustha which has the dorso-posterior cavity without a median lobe (present in all other species, with variable shape and size); its ventro-posterior cavity has a distinct U-shaped excavation (character 20); it has a unique shape of the lateral lobes (21); it is the only species with a very narrow parameral stem and without an inner process (23); it has a distinctive shape of the parameral blade (24), and also the spermathecal bulb processes - like all other species it has three, but unlike them one is thick and forked at the apex.M. serrata also has some strong apomorphies: the shape of the head is nearly parallel-sided (5) (rather like Orthoschizops, which also has parallel sides but onlyin the posterior three-quarters of the head); the anterior part is distinctly tapered upwards; the shape and number of denticles on the lateral margin of the head (8, 9); and the shape, size and number of spines on each connexivum (17).Although not supported by many characters (as evidenced by the bootstrap results), there are some species-groups indicated by the tree. One clade is the gigantea group, which includes baranovi, gigantea, vicina and longispinis, defined by the synapomorphies of the shape of the lateral margins of head (7), and the shape and number of teeth on the lateral margins of the pronotum (13). There may be synapomorphies in genital characters too, but baranovi and longispinis lack any genitalic data, while gigantea lacks data for male genitalic characters: vicina is the only species of the clade with complete data. Although monophyly of vicina + gigantea is supported by the shape of the humeral angles (14), vicina is the only species of Mustha which has dentine only on the anterior part of the lateral margin of the head, a trait it shares with the outgroup Orthoschizops (but it has more distinct and modified denticles in comparison to Orthoschizops, which has only a few very small denticles).The monophyly of incana + morgani is supported by three syapomorphies: the colour of the hemelytra (2), the number of teeth on the lateral margin of the head (9), and the shape of the dorso-posterior cavity of the pygophore (19).The monophyly of spinosula + spinosus is supported by four characters: the colour of the hemelytra (2), the shape of the dorso-posterior cavity of the pygophore (19), the shape of the lateral lobes of the pygophore (21), and the shape of the parameral stem (23). In the whole tree this is the only clade where all species have more or less complete data. Like most halyine species, however, their parameral blades are very different from each other (24), and they also have many unique characters. The most important of these is the gap between the projected part of the paraclypeal lobes in spinosula, which it shares with izmirensis (in all other species the lobes entirely enclose the clypeus) and also the outgroup Orthoschizops
Acknowledgments: We thank the British Museum of Natural History, London and Natural History Museum Karachi, Pakistan, and Imtiaz Ahmad for providing material.
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|Date:||Apr 30, 2014|
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