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----------. 1972d. Interaction of Philiathria dido (Heliconiinae) and Victorina
steneles (Nymphalinae) at Stachytarpheta flowers: evidence against mimetic association. Act. Biol. Venez. 8 (in press).
----------. 1972e. Strategies of reproduction in some tropical butterflies. Oikos 23
(in press).
PIERIS NAPI L. (PIERIDAE) AND THE SUPERSPECIES CONCEPT
S. R. Bowden
53 Crouch Hall Lane, Redbourn, Herts., England
This is a subject to be treated at greater length on some future occasion: the present note is intended to draw attention to unresolved taxonomic questions, which particularly affect the North American populations.
When the European collector enquires, "Is bryoniae Ochsenheimer a separate species?" he may mean either of two different things. He may be asking whether ssp. bryoniae is reproductively separate from the other Pieris napi L. flying in the same country, or he may want to know whether bryoniae + flavescens Wagner + neobryoniae Sheljuzhko and perhaps adalwinda Fruhstorfer + hulda Edwards +......are reproductively isolated, severally, from napi + britannica Verity + meridionalis Heyne + oleracea Harris + venosa Scudder + . . . . The answers are likely to be different, and only that to the simpler question can be unequivocal.
Dobzhansky (1970), quoting Mayr and also Amadon, defines a super-species as a monophyletic group of closely related and largely or entirely
allopatric species, or as a group of.....essentially allopatric taxa that
were once races of a single species but which have now achieved specific status. The components of the superspecies are semispecies or allospecies; gene-exchange is still possible among semispecies but not as freely as among conspecific populations. Thus the Holarctic Pieris napi-bryoniae complex is a perfect example of a superspecies.
The definition involves "species," which can itself be defined in many different ways. For butterflies, a formally new, though quite theoretical, criterion of species status has been given (Bowden, 1972):
Where the taxa have come into contact, if sympatry is leading to increased genetic and sexual barriers between them, the populations are to be taken as already belonging to distinct species; if not, not.
This fixes speciation at a rather earlier stage than the "full speciation" of many systematists, and transfers a number of supposed semispecies to the
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species category. But of course it still gives no assistance with populations which have remained apart geographically, except in so far as captive pairings provide evidence of the probable results of cross-breeding in the wild.
The usual tests decide readily enough that Pieris virginiensis Edwards is specifically separated from P. napi oleracea, and experiments (Bowden, 1966, 1972) leave no doubt that it is also distinct from P. n. napi.
We can be nearly as certain that, in Switzerland, wild bryoniae is re-productively almost completely isolated from napi, though fertile hybrids are easily obtained in captivity. Experimentally, fertile oleracea X bryoniae Fi pairings are obtained as easily as napi X bryoniae, but thereafter fertility crashes (Bowden, 1972). On the other hand oleracea X napi can be carried to the direct F3 at least. These results permit the conclusion that P. n. napi and P. n. oleracea are still conspecific, and will interbreed if the Atlantic Ocean is abolished next year. But it is not necessary to wait so long to conclude that reproductive barriers would in fact go up rapidly—oleracea and European napi are very different insects.
The writer has appreciable breeding experience of only three Nearctic subspecies of napi, including virginiensis, the third being marginalis Scudder. None of these can be raised on Alliaria, a plant which the European subspecies eat readily (Bowden, 1971a, 1971c). The larvae all differ from European napi and bryoniae, most conspicuously by the absence of bright yellow rings round the spiracles. The pupae vary in shape: P. n. marginalis is fairly close to P. n. napi, but virginiensis is radically different; P. n. oleracea is intermediate, but tending towards virginiensis (Bowden, unpublished). Pupae of the various European napi and bryoniae subspecies are, on the other hand, practically indistinguishable from one another. The relative length of the antennae also can be used to differentiate subspecies (Bowden, 1971b). The antennae of P. n. oleracea are conspicuously shorter than those of four European taxa measured, between which no statistically significant difference is found. P. virginiensis is perhaps slightly closer to the European proportion, but the difference from oleracea was not significant as measured. P. n. venosa shows a "European" antenna/wing ratio, as does P. n. hulda. P. n. marginalis (Oregon) is intermediate between oleracea and European, and differs significantly from both.
It is clear that phenotypic differences at three stages combine to separate oleracea from napi, even if one disregards the genetically determined melanic patterns above and below the wings. The name Pieris
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oleracea could almost certainly be used in that form without error. But the status of other taxa is not so readily determinable.
Lorkovic (1970) describes a confusing case in south-eastern Europe. In parts of Jugoslavia resides a population balcana Lork, which is phenotypically like P. napi meridionalis with some characters of ssp. pseudorapae Verity, but which karyologically resembles bryoniae and also pairs much more willingly with bryoniae than with P. n. napi. In the northern Caucasus is another population, balcarica Wojtusiak & Niesiolowski, which karyotypically rather approaches balcana but shows no reproductive isolation from P. n. napi; morphologically it resembles P. n. pseudorapae (Lebanon). Now there is as yet no sufficient evidence on which to determine whether Lebanon pseudorapae is specifically or only subspecifically distinct from P. napi napi, and its karyotype is unknown; hence one cannot decide whether ssp. balcarica is a subspecies of napi s.s. or of pseudorapae.
Where the limits of true species should fall among the groups of subspecies will become better known as the relations between subspecies are explored in search of the evolutionary paths. But at present only scraps of the necessary knowledge are available, and we deceive ourselves if we pretend to have more.
One concludes that for most of the taxa which have ever been included in Pieris napi we should continue to use a binomial or a trinomial nomenclature, Genus species subspecies, but that when there is still insufficient evidence to decide to what species a particular subspecies belongs, we should instead use the superspecies name in parentheses: Genus (super-species) subspecies.
If the subspecies in question constitutes what Kiriakoff (1948) and Lorkovic (1953) call a semispecies, this style is identical with theirs. Its adoption should imply that a semispecies (while it is considered such) cannot be allowed to have its own subspecies, even under the inappropriate guise of "forms/' Indeed, while we are unable to allot a given semispecies to a species, we are unlikely to be able to allot further subspecies to that semispecies with any degree of certainty.
If, however, the subspecies is not considered to be a semispecies, but is merely a taxon of still uncertain affinities, the same style may be used. The resulting slight ambiguity is justified by the rather temporary taxo-nomic status of the semispecies: in either case the aim must be final reversion to the conventional trinomial.
Nevertheless, in the Pieris napi group we find a continuous range of differentiation, from local populations through subspecies to species, which nomenclature cannot fully reflect. The adoption of an arbitrary
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criterion for specific status will not change this. Names are labels, and the amount of biological information that they can be expected to hold is limited.
Literature Cited
Bowden, S. R. 1966. Polymorphism in Pieris: "subtalba" in P. virginiemis.
Entomologist 99: 174-182. ----------. 1971a. American white butterflies and English food-plants. J. Lepid. Soc.
25: 6-12. ----------. 1971b. Metrical discrimination of variable butterflies: antenna-length in
Pieridae. Entomologist 104: 236-239. ----------. 1971c. "Pieris napf in America: reconnaissance. Proc. Brit. Entomol.
Nat. Hist. Soc. 4: 71-77.
1972. "Pieris napi" in America: genetic imbalance in hybrids. Proc.
Brit. Entomol. Nat. Hist. Soc. 4: 103-117. Dobzhansky, T. 1970. Genetics of the Evolutionary Process. Columbia Univ.
Press, New York. 505 p. Kiriakoff, S. G. 1948. On the so-called "lower" taxonomic categories. Lepid.
News 2: 3-4. Lorkovic, Z. 1953. Semispecies a necessary new taxonomic category. Biol. Glasnik
7: 236-237. ----------. 1970. Karyologischer Beitrag zur Frage der Fortpflanzungsverhaltnisse
siideuropaischer Taxone von Pieris napi. Biol. Glasnik 21 ("1968"): 95-136.
NOTES ON URODUS PARVULA (HENRY EDWARDS) (YPONOMEUTIDAE)
S. W. Frost
Frost Entomological Museum, The Pennsylvania State University, Department of Entomology, University Park, Penn. 16802
Urodus parvula (Henry Edwards) is a common species in Florida and has been recorded from many localities from Miami north to Jacksonville. R. B. Dominick states that the species is also common from March to November at McClellanville, South Carolina. A single specimen in the Cornell University collection from Okefinokee Swamp, Georgia, is apparently the only record from that state. This species may occur along the Gulf coast towards Texas and northward along the Atlantic coast. Forbes (1923) stated, "The northern record (District of Columbia) is based on a single specimen which may have been a stray."
Edwards (1881) referred this species to the genus Penthetria, Dyar (1898) placed it in Trichostibas, and Forbes (1923) assigned it to Urodus. Although only one species of Urodus is known from North America, this