Grallipeza paraplacida, Marshall, S. A., 2013

Marshall, S. A., 2013, Grallipeza Rondani (Diptera: Micropezidae: Taeniapterinae) of the Caribbean and North America, Zootaxa 3682 (1), pp. 45-84 : 47-48

THE G. PLACIDA CLADE

The G. placida clade divides naturally into three groups, one made up of the closely related G. placida (Loew) , G. baracoa (Cresson) , G. n e b u l o s a (Loew), G. t u r b a n.sp. and G. paraplacida n.sp., one comprising G. p e re z i n.sp. and G. a b e j a n. sp., and the other made up of G. albiterga n.sp. and its relatives. Grallipeza placida , G. baracoa , G. nebulosa , G. turba and G. paraplacida share the following putative synapomorphies:

9) Distiphallus bulb with two sequential coils followed by a flat distal extension. 10) Abdominal pleuron almost entirely white.

11) Paired spermathecae large, recumbent and bell or pipe-shaped. 12) Wing with a distinct discal band that does not reach the wing margins.

Grallipeza placida and G. paraplacida share the following character:

13) Each arm of the genital fork with a prominent, subquadrate inner basal lobe terminating in a row of small teeth.

Grallipeza baracoa and G. nebulosa are extremely similar in characters other than the distiphallus apex, and have in the past been treated as synonyms. The most convincing synapomorphy linking these two species is:

14) Aristal hairs reduced, arista almost bare. The hairs are also somewhat reduced in G. t u r b a, so this character is treated as multistate (14.1, aristal hairs short; 14.2, aristal hairs greatly reduced).

Grallipeza perezi and G. abeja , both from the isolated Las Abejas intramontane area of the Dominican Republic, are loosely linked to the G. albiterga group by the following character:

15) Wing evenly infuscated in at least distal three quarters.

Grallipeza perezi is unknown from females and G. abeja is well characterized for both sexes but still difficult to place because it is so autapomorphic for almost all significant characters. The sympatric G. p e re z i and G. a b e j a appear to be sister species on the basis of the following external characters:

16) Dark legs with a distal yellow band (a reversal of the usual pattern).

17) First tarsomere and basal half of second tarsomere white. Fore tarsomere colour often varies widely between closely related taeniapterine species and it is therefore not a generally reliable indicator of relationship. No other Caribbean Grallipeza , however, has a sharply bicoloured second tarsomere.

The remaining clade, made up of G. albiterga and its relatives, includes several rarely collected species characterized as follows:

18) Anterior abdominal tergites pale or desclerotized, contrasting with posterior tergites. Within the group characterized by the unusually desclerotized anterior abdominal tergites a distinctive subgroup is characterized by:

19) All or part of the frontal vitta secondarily darkened. Most Grallipeza , including almost all species in South and Central America, have a partially black frontal vitta. Since the Caribbean species with this character are deep within the G. placida group, otherwise characterized by an orange vitta, the darkened frontal vitta is interpreted as independently derived in this group. Fig. 1A shows character 19 originating independently in G. p e re z i and the clade made up of G. nigrivitta and G. albiterga .

One significant character apparently incongruent with the above arrangement is the cervical sclerite. In the basal lineages ( spinuliger , placidoides , scurra , and footei ) it is unmodified and similar in both sexes, but in other species the female cervical sclerite is at minimum flatter and duller than that of the male. Males of several taeniapterine genera grasp the female's cervical sclerite with their fore tarsi during mating, so modifications in the female cervical sclerite are probably driven by sexual selection. In most species of the G. placida clade the female cervical sclerite is as follows:

20) Female cervical sclerite with a large differentiated ventral area densely covered with conspicuous pits. This character is apparently reversed in G. abeja and possibly in the clade including G. nebulosa , baracoa and turba .

The above outline leaves G. flavicaudata and G. pleuritica unplaced because they were not available for dissection, and they cannot be placed on the basis of external characters. Grallipeza cliffi , known only from the holotype and one paratype from Jamaica, is also known from inadequate material (there is no dissection of a male and only a single poor dissection of a female G. cliffi available). Grallipeza flavicaudata , G. pleuritica and G. cliffi are not included on Fig. 1A.