Case Study Panesthiinae

Those members of the Panesthiinae for which we have ecological information are known to burrow in soil (Geoscapheini) or rotted wood (the remainder). They therefore illustrate the range of wing variation possible within an ecologically similar, closely related taxon (Table 2.4). Many species in the subfamily have fully developed tegmina and wings, and are heavy bodied but able flyers (Fig. 2.12A). Male Panesthia australis, for example, have been collected at lights in Australia (Roth, 1977; CAN, pers. obs.). Some genera include sexually dimorphic species, with winged males and wingless females (Mio-panesthia), and a number of species in the genus Panes-

Table 2.3. Tryonicinae (Blattidae) illustrate the complete range of wing development,from fully developed wings to completely apterous, with intermediate stages (LMR, pers. obs.).

Genus

Wing characters

(no. species)

Country

Fully winged, but wings may not reach the end of the abdomen

Methana (10)

Australia

Tegmina reduced, elongated, lateral, completely separated from the mesonotum,

Tryonicus (3)

Australia

reaching a little beyond hind margin of second abdominal tergite, hindwings present,

(female apterous)

vestigial, lateral, completely covered by the tegmina

Tegmina small, lateral lobes completely separated from the mesonotum,

Punctulonicus (2)

New Caledonia

not reaching the first abdominal tergite, wings absent

Angustonicus (2) Rothisilpha (2)

Tegmina lateral, but not completely separated from the mesonotum, wings absent

Pellucidonicus (2) Pallidionicus (5) Angustonicus (1) Punctulonicus (1) Rothisilpha (1)

New Caledonia

Completely apterous

Lauraesilpha (4)

New Caledonia

Fig. 2.12 Wing condition in wood-feeding Panesthiinae. (A) Fully winged adult of Australian Panesthia australis; photo by C.A. Nalepa; (B) detail of adult Australian Panesthia cribrata showing ragged wing bases after dealation; photo courtesy of Douglas Rugg; (C) strikingly patterned winged female of Caeparia donskoffi from Vietnam, body length approximately 3.5 cm; photo by L.M. Roth.

Fig. 2.12 Wing condition in wood-feeding Panesthiinae. (A) Fully winged adult of Australian Panesthia australis; photo by C.A. Nalepa; (B) detail of adult Australian Panesthia cribrata showing ragged wing bases after dealation; photo courtesy of Douglas Rugg; (C) strikingly patterned winged female of Caeparia donskoffi from Vietnam, body length approximately 3.5 cm; photo by L.M. Roth.

Table 2.4. Extent of development of tegmina and wings in 10 genera of Panesthiinae;after Table 6 in Roth (1982b).The "reduced"wing category includes brachypterous morphs, micropterous morphs,and those with reduced tegmina and absent wings. One genus includes polymorphic species (Panesthia).Sexual dimorphism is found only in the genus Miopanesthia.

Table 2.4. Extent of development of tegmina and wings in 10 genera of Panesthiinae;after Table 6 in Roth (1982b).The "reduced"wing category includes brachypterous morphs, micropterous morphs,and those with reduced tegmina and absent wings. One genus includes polymorphic species (Panesthia).Sexual dimorphism is found only in the genus Miopanesthia.

Number of species + subspecies with tegmina and wings

Genus

Fully developed (macropterous)1

Fully developed + reduced-wing morphs

Reduced

Absent

Total

Panesthia2

23 + 1

5 + 1

15 +2

11 + 1

54 + 9

Miopanesthia2 Male

6

0

0

2

8

Female

13

0

0

7

8

Ancaudellia2

15+1

0

3 + 3

0

18 + 4

Salganea2

26 + 3

0

12 + 1

4

42 + 4

Caeparia2

4

0

0

0

4

Microdina

0

0

1

0

1

Parapanesthia4

0

0

0

1

1

Neogeoscapheus4

0

0

0

2

2

Geoscapheus4

0

0

0

2 + 2

2 + 2

Macropanesthia4

0

0

0

4

4

1A number of these eventually shed their wings.

2Wood-feeding cockroaches; information on the diet of Miopanesthia,Caeparia, and Ancaudellia from a pers.comm.from K.Maekawa to CAN.

3The original description of M.sinica Bey-Bienko did not indicate the wing condition of the female;the implication is that they have tegmina and wings

4Soil-burrowing cockroaches (Geoscapheini).

1A number of these eventually shed their wings.

2Wood-feeding cockroaches; information on the diet of Miopanesthia,Caeparia, and Ancaudellia from a pers.comm.from K.Maekawa to CAN.

3The original description of M.sinica Bey-Bienko did not indicate the wing condition of the female;the implication is that they have tegmina and wings

4Soil-burrowing cockroaches (Geoscapheini).

thia are intraspecifically variable. Of these, both males and females may have either well-developed or variably reduced wings. In some species (e.g., Pane. australis), the reduced-wing form is uncommon (Roth, 1977).

Uniquely among cockroaches, some macropterous members of this subfamily shed their wings. In some species of Panesthia, Salganea, and Ancaudellia only the basal region of the tegmina and wings remains intact. The wings are not cleanly snapped at a basal suture, as in termites, but have a raggedy, irregular border (Fig. 2.12B) (Roth, 1979c; Maekawa et al., 1999b). Some early observers thought that dealation resulted from the chewing action of conspecifics (Caudell, 1906), that they "solicit the assistance of their comrades to gnaw them off close to the base." Others, however, suggested that the wings were broken off against the sides of their wood galleries, because dealation occurs even in isolated individuals and because the proposed gnawing action was never observed (McKeown, 1945; Redheuil, 1973). The wings are most likely lost by a combination of both behaviors. In laboratory studies of Panesthia cribrata, Rugg (1987) saw adults moving rapidly backward, rubbing the wings against the sides of the cage, and also observed a male chewing the wing of a female, then dragging off a tattered portion and eating it. Rugg illustrates obviously chewed wings, with distinct semicircular portions removed. Individuals are unable to chew their own wings (D. Rugg, pers. comm. to

CAN). Like termites and some other insects, Panesthiinae with deciduous wings restrict flight activity to the pre-reproductive stage of their adult life. It would therefore be of interest to determine if flight muscle histolysis accompanies wing loss, and if so, how it relates to fecundity. In crickets, dealation induces histolysis of the wing muscles and a correlated rapid production of eggs (Tanaka, 1994).

A well-corroborated estimate of relationships among 20 species of Panesthiinae inferred from a combined analysis of 12S, COII, and 18S is illustrated in Fig. 2.13 (Maekawa et al., 2003). We mapped four wing-related character states onto the depicted tree: wing morphology (macropterous, reduced wings, or apterous), and in macropterous species, whether the wings are permanent or deciduous. The apterous condition appears to have evolved three times, in Miopanesthia deplanata, Panesthia heurni, and the Geoscapheini. Deciduous wings arose twice, in Salganea and in the lineage that includes Panesthia and Ancaudellia. Within Salganea, reduced wings seem to be derived from the macropterous, deciduous state. Maekawa et al.'s (2003) phylogeny is not fully resolved and shows the genus Panesthia as poly- or para-phyletic. It is nonetheless obvious that the morphological wing condition and the behaviors associated with removing deciduous wings are evolutionarily labile in these cockroaches. Wings are generally dull and uniformly colored in the Panesthiinae that eventually shed them. Un

Fig. 2.13 Phylogenetic distribution of wing condition in the Panesthiinae. The phylogenetic tree is inferred from a combined analysis of 12S, COII, and 18S, obtained using Bayesian inference of phylogeny with the GTR + I + G model of substitution. Posterior probabilities (PP), expressed as percentages, are shown above branches to indicate the level of support for each node. Branches with less than 50% PP were collapsed to form polytomies. Bootstrap values (expressed as percentages) from an MP analysis are shown below the nodes. The asterisk indicates a node that was not supported in more than 50% of bootstrap replicates; however, an analysis in which COII third codon transitions were downweighted by a factor of 4 resulted in 70% support. The scale bar indicates the number of inferred substitutions per site. From Fig. 3 (p. 1305) in Maekawa et al. (2003), courtesy of K. Maekawa and with permission of the Royal Society of London. Wing conditions based on Roth (1979b, 1979c) and the observations of K. Maekawa (pers. comm. to CAN).

Fig. 2.13 Phylogenetic distribution of wing condition in the Panesthiinae. The phylogenetic tree is inferred from a combined analysis of 12S, COII, and 18S, obtained using Bayesian inference of phylogeny with the GTR + I + G model of substitution. Posterior probabilities (PP), expressed as percentages, are shown above branches to indicate the level of support for each node. Branches with less than 50% PP were collapsed to form polytomies. Bootstrap values (expressed as percentages) from an MP analysis are shown below the nodes. The asterisk indicates a node that was not supported in more than 50% of bootstrap replicates; however, an analysis in which COII third codon transitions were downweighted by a factor of 4 resulted in 70% support. The scale bar indicates the number of inferred substitutions per site. From Fig. 3 (p. 1305) in Maekawa et al. (2003), courtesy of K. Maekawa and with permission of the Royal Society of London. Wing conditions based on Roth (1979b, 1979c) and the observations of K. Maekawa (pers. comm. to CAN).

like the other macropterous species, Panesthia transversa and Caeparia crenulata (as well as other species of Cae-paria) have strongly colored and patterned wings and retain them throughout their adult life (Fig. 2.12C). This reinforces the idea that cockroach wings have functional significance in contexts other than flight; in this case it is likely that retained wings have signal value to predators, conspecifics, or both. A comparison of the population genetics of apterous or brachypterous wood-feeding species to those that have remained flight capable might yield data relevant to dispersal distances.

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