Landcare Research - Manaaki Whenua

Landcare-Research -Manaaki Whenua

FNZ 15 - Ambositrinae (Insecta: Hymenoptera: Diapriidae) - Phylogeny

Naumann, ID 1988. Ambositrinae (Insecta: Hymenoptera: Diapriidae). Fauna of New Zealand 15, 168 pages.
( ISSN 0111-5383 (print), ; no. 15. ISBN 0-477-02535-8 (print), ). Published 30 Dec 1988


Most of the characters listed in Table 1 and used to construct the phylogeny (Text-fig. 1) are discussed in Naumann (1982). In general the polarity of each character has been determined by comparison with genera of the subfamily Belytinae, which appears to include the most primitive Diapriidae. Many of the plesiomorphies (those for characters 1, 3 - 5, 7, 8, 10 - 15, 18 - 21, 23 - 25, 30, and 32) are plesiomorphies for the Hymenoptera as a whole. Only the modifications of T2, the parafrontal carina, the pronotal scrobe, and the cercus require further explanation.

Modifications of T2. Fig. 26 - 29 show the plesiomorphic arrangement of the anterior metasomal tergites in the Hymenoptera. Either the tergites do not overlap, or the posterior margin of each tergite slightly overlaps the anterior margin of the following one. This is the situation in primitive Diapriidae, and is seen widely in Belytinae (Fig. 30, 31). In all Diapriidae T2 is relatively large. The posterior margin of Tl (pmt) is clearly visible in dorsal view across its entire width. (In Diapriidae Tl is fused to S1, and together they form the petiole.) The joint between Tl and T2 allows considerable mobility, which is important for manoeuvres associated with oviposition and copulation. However, it is a point of weakness which may be susceptible to damage by dirt particles or predators. Therefore, within the Ambositrinae there is a trend towards the at least partial protection of this joint. Lateral extensions of T2 (al, Fig. 30) combine with similar outgrowths of S2 to protect the joint in all Ambositrinae.

In Diphoropria Kieffer and Archaeopria n.gen. carinae (ct) arise from each anterolateral corner of T2 and provide additional dorsolateral protection to the joint (Fig. 32, 33). The posterior margin of Tl is still broadly visible in dorsal view, and the anterior margin of T2 appears to be emarginate, with the emargination flanked by carinae.

In Pantolytomyia Dodd a flange (ft) arises from each anterolateral comer of T2 to partially cover the Tl - T2 joint from above (Fig. 34, 36). Consequently, only a small portion of the posterior margin of Tl is visible in dorsal view and T2 has acquired a secondary, incised, anterior margin (am, Fig. 34, 36).

The most complete type of protection of the Tl - T2 joint has been achieved independently within the Dissoxylabis Kieffer group of genera and in the Betyla group. The flange arising from T2 forms a complete cover over the joint, and T2 has acquired a secondary, 'entire' anterior margin (am, Fig. 35, 36). The posterior margin of Tl is not visible in dorsal view, unless the gaster is very strongly jack-knifed on the petiole.

Ambositra protects the T1 - T2 joint in an entirely different way. T1 and T2 are more or less as in Diphoropria except that the lateral outgrowths of T2 are very large. The T1 - T2 joint is almost completely overgrown and protected by dense, stiffly coiffured pubescence.

The blunt, pubescent anteromedian process of T2 of Māoripria n.gen. appears to be a novel development in this genus, although it is lost in one apterous species. Possibly the low, bare longitudinal ridges seen in a similar position in some Diphoropria and Scianomas Naumann are homologous structures.

Parafrontal carina. This minute carina extends from the posterior wall of each antennal socket to the frons and encloses the postantennal excavation (Fig. M63, M64). It is known only in Māoripria, although processes from either the antennal socket or the frons or from both are present in many other genera.

Pronotal scrobe. A transverse groove is present on the pronotum in some Belytinae. This seems to be the forerunner of the discrete pit here termed the pronotal scrobe (Fig. M139, M140). The pronotal scrobe is the synapomorphy of the Dissoxylabis group of genera.

A pronotal scrobe is also present in macropterous males of two species of Betyla, but it is absent from most macropterous males, all wing-reduced males, and all females of the genus (all female Betyla are apterous). Two explanations are possible:

  1. the pronotal scrobe has been acquired secondarily in Betyla, and Betyla is not closely related to the Dissoxylabis group (as depicted in Text-fig. 1);
  2. the pronotal scrobe has been lost secondarily from most Betyla, and thus Betyla is a member of the Dissoxylabis group.
The pronotal scrobe certainly has been lost in the flightless Australian genus Riaworra Naumann, so it is not unreasonable to imagine the loss of the pronotal scrobe in wing-reduced Betyla, where the mesosoma is otherwise considerably modified. However, it is less easy to accept the loss of the pronotal scrobe from macropterous Betyla.

Cercus. An articulated cercus occurs in most primitive Hymenoptera, and presumably is part of the diapriid ground-plan. Within the Ambositrinae the articulated cercus may be digitiform (i.e., length exceeds basal diameter) or lobiform (i.e., length and basal diameter similar). In Archaeopria and Pantolytomyia the cercus of the female (and sometimes also that of the male) is reduced to a convex plate bearing sensory setae. Such reduction has taken place independently within the Belytinae and the Diapriinae.

Sister-group relationships. Text-fig. 1 summarises the fairly clear-cut autapomorphies of the various ambositrine genera and proposes a tentative phylogeny for the subfamily. A resolution of the Dissoxylabis group has been proposed by Naumann (1982).

Many of the proposed sister-group relationships are very weakly established. Several are defined by single apomorphies, e.g., Ambositra + Diphoropria, Perissodryas + ... + Betyla, Gwaihiria + ... + Betyla, and Parabetyla + Zealaptera + Betyla; and two branches - Ambositra + ... + Betyla and Māoripria + ... + Betyla - lack synapomorphies entirely. Only the primary dichotomy separating Archaeopria and Pantolytomyia from the other genera is beyond suspicion. Further consideration of the phylogeny of the subfamily and of a tribal classification should be deferred until the poorly known Neotropical genera have been assessed.

The cladogram allows numerous convergences. The pre-episternal furrow has opened up in Pantolytomyia + Archaeopria and in Perissodryas Naumann. The inner wall of the antennal socket is dorsally produced in Pantolytomyia (although sometimes weakly so), Archaeopria, Māoripria, apterous Perrissodryas, Allobetyla Naumann, and Lathropria Oglobin. The produced socket is often correlated with terricolous habits and wing reduction. Wing reduction and the associated modifications of the head and mesosoma have occurred at least nine times. Of eighteen ambositrine genera, only six do not include at least some wing-reduced forms. The distribution of modified flagellar segments remains a confused matter, and I have omitted the character from the phylogenetic analysis. However, it does seem likely that a carina has appeared on F3 independently within Diphoropria, Māoripria, Perissodryas, and Gwaihiria Naumann. S3 is anteriorly swollen to accommodate an enlarged ovipositor in females of Māoripria, some Betyla, Perissodryas, AIIobetyla, Scianomas, and some Dissoxylabis.

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