Two New Aberrant Forms of Tiger Swallowtail Butterfly From the Great Lakes Hybrid/Transition Zone (Lepidoptera: Papilionidae)

Content Provider	Semantic Scholar
Author	Scriber, J. Mark
Copyright Year	1990
Abstract	Two aberrant forms of the tiger swallowtail butterfly. Papi io glaucus, are described. Both of these aberration types (one in a male, the other in females) are believed to be previously unreported and both are from the Great Lakes hybrid zone and plant transition zone (41 ° _44°N latitude). It is, therefore, possible that genetic introgression from the northern tiger swallowtail P. glaucus canadensis may have been involved in some way with these abnormalities. While the specific causes of aberrant forms of tiger swallowtail butterflies remain basically unknown, it has been noted that the frequency of unusual forms may be greater within, or near, the plant and insect transition zone (Curtis 1957, Remington 1968) that occurs throughout the Great Lakes region (Scriber et al. 1987). For example the distinctive Papilio glaucus "fletcheri" variety (Fletcher 1889), as far as reported thus far, occurs only in males and typically north of, or very close to the transition/hybrid zone of the P. g. glaucus L. and P. g. canadensis R. & J. subspecies (Scriber and Lintereur 1983; and T.]. Allen, D. Mutusik, H. Romack and ] .D. Zelias, pers. comm.). A different "dark cell" aberration has a genetic basis and was reported only from females which also originated within the subspecies transi­ tion zone i Schuykill County, Pennsylvania (Scriber and Evans 1988a). A large series of 42 sexual mosaics and bilateral gynandromorphs of Papilio glaucus (most of which are from the hybrid zone) is illustrated and described by Scriber and Evans (1988b), and it is concluded that intersubspecific pairings may be conducive to the infrequent occurrence of bilateral gynandromorphs. Another low frequency phenomenon that may occasionally be related to hybrid interactions between subspecies of Papilio glaucus is the occurrence of "melanic intermediates" in which the dark morphotype female has incomplete expression (see figures and descriptions in Clark 1932, Clark and Clark 1951, Scriber et al. 1987). In these "intermediate" females the underlying black tiger striping pattern may be clearly visible with mostly yellow background, appearing lightly "dusted," or they may be essentially non-distinguishable due to a much heavier suffusion of dark scales, resulting in an "intermediate" color series or continuum. While partial dark suppression from P. g. canadensis genes may be involved (Scriber et al. 1987, Scriber et al. in prep.), these "dark intermediates" are known from nearly every state east of the Mississippi River, and it has been shown that the phenomenon can be environIDepartment of Entomology, Michigan State University, East Lansing, MI 48824 1 Scriber: Two New Aberrant Forms of Tiger Swallowtail Butterfly From the Gr Published by ValpoScholar, 1990 122 THE GREAT LAKES ENTOMOLOGIST Vol. 23, No.3 mentally induced in P. g. glaucus by high temperatures (Ritland 1986, R.C. Lederhouse and J.M. Scriber unpublished). A slightly aberrant "sooty" region basally in both the dorsal and ventral sides of the forewings and hindwings was noted in female P. g. glaucus by Clark (1932) and Clark and Clark (1951). A similar darkened inner wing pattern was subsequently noted in a male P. g. glaucus and certain of his unique offspring (possibly involving a chromosome abnormality) that included dark segregating females where they were not expected to be possible, including offspring of a P. g. can densis female (Scriber and Evans 1986). Here, two new and different types of aberrations are described, which have not been previously reported as far as is known. One of these aberrations was found in a male from the potential hybrid zone f P. g. glaucus and P. g. canadensis, and the other aberrant form is represented by two females of two different family lines from the same hybrid zone population in Green Lake County, Wisconsin. RESULTS In the last 8 years our lab has reared more than 40,000 tiger swallowtail butter­ fly larvae. We have reared approximately 20,000 to the adult stage. In addition, we have collected from widespread geographic areas across the eastern half of the country. Two types of aberrations are described below that we have not seen in any of the other individuals we have reared or collected in the field. The Ilfst aberration, which is described in this paper, appeared in a male. In males, the blue scales in the submarginal area are usually reduced on the hindwings; however, this blue extends across most of the hindwings of females and often into the forewing. This aberrant male was reared from stock sent by William Houtz (Schuykill County, PA) and has the blue scaling essentially as in normal females (Fig. 1). The second aberration occurred in two females reared from the same popula­ tion in Green Lake County, Wisconsin. These females have an atypical melanism and atypical wing pattern (Figs. 2 and 3) compared to normal P. g. glaucus or P. g. canadensis (Fig. 2). The black band on the hind wing virtually fills the entire anal cell, and there is essentially no blue scaling on the dorsal or ventral wing surfaces as in most P. g. glaucus and P. g. canadensis females. These two females were reared from separate mothers, however, each originated from normal appearing yellow morph field-captured mothers from Green Lake County (see Table 1). DISCUSSION The control of blue scaling of the hind wings of Papilio glaucus subspecies has not been genetically determined yet (see West and Clarke 1988). There is also consid­ erable variation in the blue scaling patterns observed among our voucher collection females (e.g. with blue scaling suffused across the entire dorsal surface of the hindwings) and males (with no blue scales). However, these two female individuals from Green Lake County Wisconsin represent an extreme case of reduced blue hindwing scaling and extra melanism. The aberrant male with unusually excessive blue scaling also represents an extreme case. It otherwise has basically similar pat­ terns to other normal P. g. glaucus males. We know of no other previous record or existing specimens of these types. We are unable to determine if introgression from hybrid interaction of P. g. glaucus and P. g. canadensis was involved in either of these aberrants (Figs. 2 and 3); however, both are from the near vicinity of the known subspecies hybrid zone across the Great Lakes region southward into the Appalachians (Luebke et al. 1988, Scriber and Hainze 1987). Other individuals caught in the exact location as the two females from Green Lake Co., Wisconsin do produce mixed color broods of daugh­ 2 The Great Lakes Entomologist, Vol. 23, No. 3 [1990], Art. 1 https://scholar.valpo.edu/tgle/vol23/iss3/1 1 1990 THE GREAT LAKES ENTOMOLOGIST 123 Figure 1. Dorsal view of an aberrant male P. gi(luCUS reared from a mother (# 16) collected by W. Houtz from Schuykill County, Pennsylvania. ters (both dark mimetic and yellow) and are often computer-scored as hybrids using multivariate discriminant analyses of male wing characteristics (Luebke et at. 1988), suggesting that subspecies introgression does occur in this area (Scriber 1990, and Scriber et at. 1990).
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Language	English
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