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Phylogeny of the Anastrepha serpentina species group

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Relationships among the species groups of Anastrepha were discussed by Norrbom et al. (1999) and McPheron et al. (1999)  (see Phylogeny of Anastrepha and Toxotrypana).  The relationships among the species of the serpentina group were analyzed by Norrbom (2002).  The following text is taken from these three references.  

The serpentina group comprises 11 species, including two of the most significant pests within the genus Anastrepha and several others of lesser agricultural importance. Anastrepha serpentina (Wiedemann) is an especially important pest of sapotaceous fruits, such as star apple, sapotes, and nispero, and A. striata Schiner is among the worst pests of Myrtaceae, especially guavas, although both species also sometimes attack mango, mombins, citrus, and various other fruits (see Norrbom, in press). As delimited by Norrbom (2002), the serpentina group comprises four previously included species, three species formerly recognized as the striata group (see Norrbom et al. 1999b), and four newly described species. 

The serpentina group is most diverse in southern Central America and northern South America, although the two widespread species A. serpentina and A. striata extend north to northern Mexico or southern Texas and A. serpentina extends south to Argentina. The other species are known from smaller ranges. Anastrepha ocresia (Walker) is endemic to the Greater Antilles and southern Florida. The ranges of A. anomala Stone (Panama; Brazil?), A. anomoiae Norrbom (Panama and Colombia), A. normalis Norrbom (Panama and Venezuela), A. pseudanomala Norrbom (Costa Rica and Panama), A. pulchella Norrbom (Panama), and A. pulchra Stone (Panama, Venezuela, Brazil (Amazonas)) extend into Mesoamerica (and there may be another species in southern Mexico and Guatemala), whereas A. ornata Aldrich (Colombia, Ecuador, Peru) and A. bistrigata Bezzi (southern Brazil) are restricted to South America.

Host plants are known for eight of the 11 species of the serpentina group. Although the host range for the species group is very diverse, the native hosts are mainly in three families. Two species (A. anomala and A. normalis) have only species of Apocynaceae as known hosts, whereas A. pulchra is known only from Sapotaceae, which also includes the main hosts of the generalist species A. serpentina. The only native host known for A. ocresia belongs to the Myrtaceae, but it has been reared from an exotic species of Sapotaceae. The only known native host plant of A. ornata, and most of those of A. striata and A. bistrigata, belong to the family Myrtaceae.

Steyskal (1977) originally included A. serpentina, pulchra, anomala, ocresia, ornata, fenestrata (Lutz & Lima) and phaeoptera (Lima) in the serpentina group. The latter two species are now placed in the robusta species group (Norrbom et al. 1999b). Norrbom & Kim (1988) and Norrbom et al. (1999b) instead included A. ornata along with A. striata and bistrigata in the striata species group based on similar scutal microtrichial patterns and aculeus tip shape, although they suggested that the serpentina and striata groups might be closely related. As noted by Stone (1942), A. ornata resembles some species of the serpentina group (sensu stricto) in wing pattern and body color, but its terminalia are similar to A. striata and bistrigata. Norrbom et al. (1999b) considered the serpentina group (sensu stricto) to be defined by several apomorphic character states. The most important was the bicolored, partially dark brown abdomen, although they noted that abdominal markings also occur in A. ornata and in a few species of the cryptostrepha, schausi, punctata, grandis and daciformis groups. Two other character states considered as possible synapomorphies were aculeus tip shape (long, moderately broad, evenly tapered, and partially finely serrate; this occurs in the previously included species except A. pulchra) and wing pattern relatively dark brown. Considering the additional variation discovered in aculeus tip shape in the new species described by Norrbom (2002), and the paler color of the wing pattern in A. normalis, the latter two characters do not appear to be synapomorphies that define a restricted serpentina group.

Norrbom (2002) reanalyzed the 11 species here included in the group based on the characters and character states indicated in Tables 1 and 2. Only the 12 characters indicated by an asterisk in Table 1 were used in the analysis; the others are either intraspecifically variable or are autapomorphies of individual species. The species known only from a male from Mexico also was excluded from the analysis. The sister taxon of the serpentina group is uncertain. Norrbom et al. (1999b) proposed that the serpentina and striata groups belong to a large clade also including the pseudoparallela, spatulata, ramosa, grandis, doryphoros, and fraterculus groups. Anastrepha dissimilis Stone, which belongs to the pseudoparallela group, was chosen as the outgroup taxon as a typical representative of all of the possible sister taxa. Almost all of the species of the other groups also would be coded 0 for the characters used in the analysis, except for aculeus tip shape, which is highly variable. The matrix was analyzed using Hennig86 option ie*. Ninety-five trees of 27 steps length resulted (ci = 0.74, ri = 0.76), four of which are shown in Figs. 12 and 13, which were produced using WinClada. The serpentina group, as defined here, is supported as a monophyletic group mainly by the presence of brown markings on the mesonotum and subscutellum and mediotergite (character 2), the only synapomorphy present on all 95 trees. Except in A. ocresia, where the brown markings are restricted to the area bordering the scuto-scutellar suture, the brown area is extensive and either somewhat U-shaped or covering most or all of the darker areas of the mesonotum. Similar extensive brown areas occur in some species of the daciformis group, but other characters indicate that this is due to homoplasy (Norrbom et al. 1999b). Brown mesonotal markings also occur in a few other Anastrepha species (e.g., A. grandis, some species of the cryptostrepha and robusta groups), but the different shapes of the markings and other characters also suggest that this is the result of homoplasy. The subscutellum and mediotergite are usually mostly brown in species of the serpentina group, although in some specimens of some species it is brown only laterally, resembling the condition in most species of the fraterculus species group. Because the mostly to entirely brown condition is more common in these intraspecifically variable species, I regard this as a different character state than that in the fraterculus group, that further supports the monophyly of the serpentina group. Outside of this group, it is uncommon in Anastrepha, occuring in some species of the grandis, daciformis, cryptostrepha and robusta groups. Only the former species group appears to be relatively closely related to the serpentina group (Norrbom et al. 1999b, McPheron et al. 1999). McPheron et al. (1999) included four species of the serpentina group in their phylogenetic analysis of Anastrepha based on mitochondrial DNA sequences. They found strong support for the monophyly of A. serpentina + normalis (as "n. sp. nr. anomala") and also for A. striata + bistrigata. Both pairs of species were included in a large clade with species of the fraterculus, spatulata, pseudoparallela, and grandis species groups, but the relationships among these groups were poorly resolved. Studies of isozymes (Morgante et al. 1980, Matioli et al. 1992) have also shown strong similarity between A. striata and bistrigata, although A. serpentina was more similar to other species.

Relationships among the species within the serpentina group were not well resolved by the morphological cladistic analysis of Norrbom (2002, see Figs. 12-13), although two clades were consistent in all 95 trees: A. striata + bistrigata; and A. serpentina + (pulchella + (pulchra + anomoiae)). The close relationship of A. striata + bistrigata is strongly supported by the shape of the posterior margin of the epandrium and the ridge on the lateral surstylus (character states 17.1 and 18.1, respectively), which are unique to these two species. The clade of A. pulchella + (pulchra + anomoiae) is also strongly supported, by the very broad connection of the C-band and S-band (character state 6.2), and the reduced or absent yellow area of the C-band posterior to the pterostigma (character state 7.1). The relationship of A. serpentina to the latter clade is supported by one or more of the following character states: distal section of S-band slender (9.1); hyaline marginal spot in cell r1 elongated distally along costa (11.1; this can also be interpreted as arising independently in A. serpentina and in A. pulchra + anomoiae), and the lateral surstylus with a small basolateral lobe (19.1). None of these states is consistently hypothesized as a synapomorphy for these four species on every tree, however; character state 9.1 is usually a synapomorphy, but on some trees it may be interpreted as a synapomorphy for these species plus A. ocresia or ornata, with subsequent change to state 2 in the latter species. The positions of the other species in the cladograms are highly variable. Anastrepha normalis is always relatively basal in the most parsimonious trees, arising as the sister group to a clade including all other species of the serpentina group (Fig. 12B; supported only if relatively darker wing pattern color (character state 5.1) is interpreted as a synapomorphy for the other species, with reversal in A. striata + bistrigata), as the sister group of a clade containing all of the other species except A. striata and bistrigata (Fig. 13A-B), as the sister group of a clade with all species except A. ornata + (striata + bistrigata) (Fig. 12A), or as the sister group of the clade A. ornata + (striata + bistrigata) (supported only if character 21.1 is interpreted as a synapomorphy, with subsequent change to state 21.2 in the other three species). Anastrepha ocresia and anomala are usually somehow included in a clade also including the serpentina clade, A. pseudanomala, and/or A. ornata, and they are not closely grouped with A. striata + bistrigata on any of the trees. Anastrepha pseudanomala is highly variable in position, in part because characters 17-20 are unknown for it. It is usually within a clade including A. ocresia, anomala, the serpentina clade, and sometimes A. ornata. On some trees it is hypothesized as the sister group of A. ornata + (striata + bistrigata), but this is supported only if A. pseudanomala is assumed to have a subapical lateral lobe on the lateral surstylus (character state 20.1). The relationship of A. ornata among the other species of the serpentina group is also unresolved by the present analysis. It is highly variable in position on the 95 cladograms. In some trees it is the sister group of A. striata + bistrigata (Fig. 12), a hypothesis supported by scutal microtrichial pattern (character state 3.1), lateral surstylus shape (20.1) and aculeus tip shape (21.2). In other trees (e.g., Fig. 13) it is placed variably within clades including A. ocresia, anomala, pseudanomala, or the serpentina clade. The hypothesis that A. ornata is more closely related to the species exclusive of A. striata and bistrigata is supported by the more extensively brown bodies of these species (character state 2.2), their broad C-band, which extends into the distal half of cell br (6.1), and the relatively dark wing pattern of all of the latter species except A. normalis (character state 5.1).

Table 1. Useful taxonomic characters in the serpentina group. Only those preceeded by asterisk were used in the cladistic analysis.

1. Orbital plate and bordering areas - 0) without brown markings; 1) orbital plate with triangular brown mark; 2) areas bordering orbital plate brown, or those areas and orbital plate brown.

*2. Color of darker areas of thorax and abdomen (areas exclusive of yellow vittae, bands and other markings) - 0) yellow brown to orange; 1) mesonotum with brown markings and subscutellum and mediotergite mostly brown; 2) abdomen, mesonotum, subscutellum, mediotergite and thoracic pleuron with dark brown areas. State 0 occurs rarely in A. ocresia, but it was coded state 2, the usual state, in the analysis. [additive]

*3. Scutal microtrichia pattern - 0) entirely microtrichose or with only medial presutural bare area; 1) with dorsocentral bare stripes; 2) bare except extreme lateral margin. [nonadditive]

4. Crossvein DM-Cu orientation - 0) with anterior end distinctly more distal than posterior end; 1) with anterior end only slightly more distal or more basal than posterior end.

*5. Wing pattern color - 0) bands largely orange brown with narrow brown margins; 1) bands mostly dark brown, S-band dark brown, including areas distal to and anterior to R-M.

*6. C-band and S-band basally - 0) separated by hyaline area in cells bm, dm, and br, extending full width of latter in part posterior to pterostigma; 1) separated by hyaline area in cells bm, dm, and no more than posterior 2/3 of part of br posterior to pterostigma; 2) separated basally at most by hyaline area in cells bm and dm. [additive]

*7. C-band yellowish area in cells r1 and r2+3 posterior to pterostigma - 0) large, extending distally into cells r1 and r2+3 at least to level of midlength of pterostigma; 1) small, not extending beyond cell r1 nor distally beyond level of basal third of pterostigma.

8. Hyaline spot in cell r1 between S-band and vein R2+3 - 0) absent; 1) present.

*9. S-band, width of distal section at apex of vein R2+3/ width of cell r2+3 - 0) 0.45-0.70; 1) less than 0.45; 2) greater than 0.70. The ratio varies from 0.53-1.00 in A. ornata, and is less than 0.45 in the Brazilian female of A. anomala, but the former was coded state 2 and the latter state 1 in the cladistic analysis because the S-band is broader more distally in the specimens with the lower ratios. [nonadditive]

10. S-band - 0) not extended to apex of vein M; 1) extended to apex of vein M.

*11. Hyaline marginal spot in cell r1 shape - 0) nearly triangular; 1) distal side larger or elongated along costa; 2) connected to hyaline area in cell br. [nonadditive]

12. Hyaline marginal spot in cell r1 alignment - 0) apex aligned basal to R-M; 1) apex aligned with R-M; 2) apex aligned distal to R-M.

13. V-band distal arm - 0) complete; 1) partially absent, present at least from vein M to margin; 2) absent, or rarely with small faint spot in cell m.

14. V-band proximal arm - 0) extended along posterior wing margin but not connected to extension from base of S-band along vein A1+Cu2; 1) extended along posterior wing margin and connected to extension from base of S-band along vein A1+Cu2; 2) not extended along posterior wing margin.

15. V-band proximal arm - 0) connected to S-band along vein R4+5; 1) separated from S-band anteriorly; 2) connected to S-band near middle of crossvein R-M.

16. Abdominal tergite color - 0) orange with posterior margins yellow; 1) at least syntergite 1+2 and tergite 3 with dark brown bands; 2) mostly brown with somewhat T-shaped yellow area.

*17. Dorsal, posterior margin of epandrium - 0) evenly convex; 1) with narrow, V-shaped, medial indentation.

*18. Lateral surstylus mesal margin bordering medial surstylus - 0) not projecting; 1) projecting posteriorly as narrow ridge.

*19. Lateral surstylus basolateral lobe - 0) absent; 1) small to moderate; 2) strong. [nonadditive]

*20. Lateral surstylus in posterior view - 0) triangular or tapering, without subapical, lateral lobe; 1) with rounded or truncate subapical lateral lobe.

*21. Aculeus tip shape - 0) at least half serrate, gradually tapered or basal nonserrate part parallel-sided; 1) nonserrate, gradually tapered; 2) nonserrate or serrate only subapically, very broad and bluntly triangular; 3) nonserrate or serrate only subapically, rapidly tapered basally, then parallel sided until near apex. [nonadditive]

Table 2. Character state matrix for the species of the serpentina group. See Table 1 for explanation of character numbers. For intraspecifically variable characters, the predominant state is listed first. Parentheses indicate states that are rare.
Character number  1 2 3 4 5678 9 10 11 12 13 14 15 16 17 18 19 20 21
dissimilis 0 0 0000 0 0 00000
striata 0 1 1 0 0000 0 0 0 0 0-2 0 1 0 11012
bistrigata 0 1 1 0 0000 1 0 0 0 0,1 0 1 0 11012
ornata 0,2 2 1 0 1100 0,2 1,0 2 ? 2 1 1 1 00012
normalis 0 2 0 0 0100 0 0,1 0 0 2 0 1,0 1 00001
ocresia 0 2(0) 2 0 1100 2 1,0 0 0 1 0 1,0 1 00200
anomala 0 2 0 0 1100 0,1 0 0 0,1 2 0 1 1 00200
pseudanomala 0,1 2 0 0 1100 0 0 0 0 2 0 1 1 ????0
sp. (Mexico) 0 2 0 0 1100 0 1 0 0 0 0 0 1 0000?
serpentina 0,1 2 0 0 1100 1 0(1) 1 0,1 2 0 1 2 00100
pulchella 0 2 0 0,1 1211 1 0 0 0 2 0,1 1(0) 1 00100
pulchra 1 2 0 0,1 1210 1 0 1 1,2 2 0 1 1,2 00003
anomoiae 0 2 0 1 1210 1 0 1 1 2 2 2 1 00103

References
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McPheron, B. A., H.-Y. Han, J. G. Silva & A. L. Norrbom. 1999. Phylogeny of the genera Anastrepha and Toxotrypana (Trypetinae: Toxotrypanini) based upon 16S rRNA mitochondrial DNA sequences, p. 343-361. In M. Aluja & A. L. Norrbom, eds., Fruit flies (Tephritidae): Phylogeny and evolution of behavior. CRC Press, Boca Raton. [16] + 944 p. [phylogeny]
Norrbom, A. L. 2002. A revision of the Anastrepha serpentina species group (Diptera: Tephritidae). Proceedings of the Entomological Society of Washington 104: 390-436.
Norrbom, A.L., R.A. Zucchi & V. Hernández-Ortiz. 1999. Phylogeny of the genera Anastrepha and Toxtrypana (Trypetinae: Toxotrypanini) based on morphology, p. 299-342. In M. Aluja & A. L. Norrbom, eds., Fruit flies (Tephritidae): Phylogeny and evolution of behavior. CRC Press, Boca Raton. [16] + 944 p.