A Study of Interspecific Hybrids in Papilio(Fifteenth Anniversary (1960) Commemorative Publication)

Abstract

Fundamental differences which separate species have been studied in interspecific hybrids of Japanese and North American Papilio at Rocky Mountain Biological Laboratory, U. S. A. in 1957 and at Nanzan University, Japan from 1958 to clarify a process of differenciation of species. Namely affinity of species has been surveyed through egg fertility, percentage of larval formation within egg shell, hatchability etc. of interspecific hybridizations and fertility of interspecific hybrids. Genetics of visible characters which separate species has also been studied. An outline of the obtained results is presented here as a preliminary report. All matings were performed by handpairing and eggs were obtained under fluorescent light. Cages of about 30 cm. cube were used for the rearings of larvae. Egg fertility, hatchability etc. of palyxenrs × "brucei", hippocrates × "brucei" and polyxenes x hippocrates are as high as intraspecific mating, From a pair of polyxenes female × "brucei" male, 78 males and 1 gynandromorph were obtained. From two pairs of the reciprocal crosses, 10 males and 20 females were obtained. Male pupae of them, which pupated in summer, emerged next spring after overwintering, but females of the same brood emerged during the same summer. These differences may due to an abnormal inheritance of voltine differences between "brucei" and polyxenes. These F1 hybrids resembled polyxenes and were fertile. From three pairs of hippocrates× "brucei", 3 females and 2 males were obtained. The appearances were intermediate of the parents. From a pair of hippocrates × polyxenes, 6 males, 3 females, and 1 gynandromorph were obtained. The adults resembled polyxenes. In xuthus × hippocrates, polyxenes, and "brucei", most of the eggs were fertilized and about half of the eggs were hatched. The adults obtained were all males and small. The number of adults obtained were respectively 29 (intermediate) from 11 pairs, 10 (resemble polyxenes) from 3 pairs, and 5 (intermediate) from 1 pair. Umbelliferae and Rutaceae were used as their larval food. In xuthus × protenor, helenus, macilentus, and memnon, eggs were obtained from more than several pairs in each kind. Egg fertility and hatchability etc. were very low in general. The larvae reached the end of the 3rd instar in the best case (xuthus × macilentus). In xuthus × bianor and maackii, egg fertility and hatchability etc, were very low and the larvae died respectively in the 1st and 2nd instar. Egg fertility of a pair of glaucus × xuthus were very high, but only one larva hatched and it reached pupal stage and died. In protenor × helenus (5 pairs), polytes × protenor (1 pair), and polytes × helenus (1 pair), most of the eggs were fertilized and more than half of the eggs were hatched. The number of adults obtained were respectively 15 (intermediate), 4 (intermediate), and 18 (resemble polytes) and all were males. From memnon × helenus, macilentus x memnon, and macilentus × protenor, 2 pupae, one pupa, and one 5th instar larva were obtained respectively. From a pair of bianor × maackii, two males were obtained and they were intermediate of the parental species. Two fertile eggs were obtained from bianor × troilus, but they did not hatch. Crossing of bianor × helenus seems entirely infertile. P. xuthus may not be a typical member of the P. machaon group, but it is also not close to "P. protenor" group. Affinity within the "P. protenor" group is not so high as affinity within the typical P. machaon group. HALDANE'S rule is applied for interspecific hybrids between P. xuthus and the P. machaon group and between P. helenus and P. protenor or P. polytes. Egg fertility and hatchability etc. are highly variable in each crossing of a same kind. Therefore, many crossing must be performed to obtain a general egg fertility and hatchability etc. in one kind of

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