Alfred Charles Kinsey

“ In each area we shall find a population obviously related to every other, but each will constitute a population whose limits of variation are different from those of any other. Sometimes these limits overlap, sometimes they are wholly within, sometimes they are wholly without the limits for each other species. Sometimes the populations are wholly segregated by mountain crests and divides, sometimes the populations hybridize and intergrade over broad zones of transition; but always each population is distinct in a great area which is the heart of the range of each species. ”

“ In a single period, in a limited area, there must have existed a population from which all of the present-day species, with their varying grades of relationships, have developed. This history of the expansion of a single genetic stock into 93 distinct populations, by processes of mutation, isolation, and on occasion subsequent recombination into hybrid populations, is the story we have been unfolding in this study, and which we are now ready to fit into the geologic time and the geographic areas in which speciation probably proceeded in the genus. ”

“ But if such a population, of hybrid origin, should in some way become isolated, then it might in the course of time become a fairly uniform population. Relieved from the continual introduction of genes from the parental stocks, the hybrids might finally achieve a thoro exchange of genes thruout the whole of the population. Then a sample taken from any part of the range would vary within the same wide but uniform limits typical of every other sample of the population. It would then satisfy our concept of a species, for it would have a common heredity. ”

“ It is this problem, the attainment of homogeneity out of a hybrid population, that has become the immigration problem of the American people in the last half-century. Whether homogeneity is a biologic virtue or not, the statesmen have shown themselves good taxonomists in their insistence that we cannot become a true species until barriers are erected to protect us from continued contributions of parental stock. Whether in peoples or insects, the melting pot cannot blend diverse materials that pour in too rapidly. ”

“ To a limited extent the form of the gall does depend upon the plant tissue involved, for the possible transformations, as we have already pointed out (Kinsey 1923:21) , are more restricted in certain tissues; but beyond that the form of the gall is dependent upon the species of the insect rather than upon the species of the plant. There must be nearly as many different kinds of gall-producing enzymes as there are species of gall wasps. When a single species of gall maker attacks more than one species of oak, the form of the gall is essentially the same on all of the hosts. ”

“ To morphology, physiology, and psychology we make certain assignments not only because we wish to deal with particular aspects of the organic organization, but because these sciences are adapted for dealing with ordinarily few species which may be taken to stand as types of whole orders and classes or phyla of plants or animals. For this reason these sciences contribute data on such problems as the relationships of the larger groups, their appearance in the geologic record, and their value as evidence of the processes of evolution itself. ”

“ The definition of species on the basis of their fertility or infertility does not delimit phylogenetic units, for while it is true that the individuals within a species must be mostly fertile inter se if they are to maintain any sort of hereditary relationship, the failure of distinct species to interbreed may be due to geographic or seasonal occurrence or to other factors not directly concerned with reproductive physiology. But if species are defined as populations with common heredity, we obtain a concept which seems genetically sound and which, we shall try to show, is a reality in nature. ”

“ Too many systematists attain their objectives when each species is "represented" by a half-dozen specimens pinned in their cabinets. These are the systematists responsible for the definition of systematic entomology as the science of transferring pins from one box to another. If taxonomists have too often made species-descriptions and catalogs and nomenclatorial inanities the end of their efforts, it is no proof that the science cannot rise above its technic and concern itself with biologic problems. As my good friend has remarked, our difference is not with taxonomy but with taxonomists. ”

“ It also appears possible that other structural peculiarities regularly associated with wing reduction may result from the same mutations of one or two genes in groups of linked genes responsible for wing characters. A single gene mutation in a single generation of insects might then give rise to a very distinct cynipid. Such radically new species are usually placed in distinct genera, and this probably explains why systematists have so often failed to believe that mutation accounts for the origin of species in nature. When the mutations are slight, they pass as products of Darwinian variation. ”

“ We may repeat that we know no single character, morphologic, physiologic, or biologic, by which a Cynips may invariably be recognized. A hairy thorax, complete parapsidal grooves, undivided foveal groove, hypopygial spine which is broadened nearer the tip; a monothalamous, fundamentally spherical, separable leaf gall, occurring on a white oak; and the maturing of the adult early in the fall with emergence delayed until the winter—this is a combination of characters that will distinguish most of the agamic forms. ”

“ Here is evidence that long-winged and short-winged species may be nearer than closely related species, for they may be alternate generations of one species.
In several of the cases cited above, we were delayed in our recognition of relationships by the peculiar hypopygial spines which, we have already mentioned, are found nowhere but among short-winged gall wasps. In connection with a generic re-arrangement which we are undertaking for the whole family Cynipidae, we have found that the hypopygial spine is one of the most constant of generic characters among the long-winged insects. ”

“ It is to an increased knowledge of the physicochemical nature of protoplasm and of the gene, and to such experimental work as that of Muller and others on mutations affected by the introduction of measurable amounts of energy, that we must look for the explanation of the first step in the process of evolution. But granting that mutations do on occasion occur, we may present a body of new data to show that these laboratory mutants are precisely the materials which have differentiated many of the species of our genus Cynips. ”

“ Concerning European Cynips Kieffer (1901:632) devoutly remarked of the insect which had delayed its emergence: “Ce qu'il attend, c'est l'époque que la Nature lui a assignée.”
Whether the emergence date is determined by the response of the insect to environmental factors should be determinable by modifications of those factors. This experiment we have conducted on an extended scale, incidental to the breeding of Cynips material. We have brought 60 of the species of this genus from every type of remote locality to breed out-of-doors under the peculiar conditions of southern Indiana winters. ”

“ THE ISOLATION OF SPECIES
It now remains to show how such mutant races as we have noted in the preceding sections of this study may be transformed into such large and relatively uniform populations as satisfy our concepts of species.
A mutant individual is still far from constituting a species. Its survival depends in the first place upon the condition that the new, mutant characters shall not interfere with the health of the organism. ”

“ It is thick woodland and we find only stray galls now and again. They are smooth and naked specimens, for aught we can tell like the smooth galls of erinacei. A mile down the road we find an open meadow where two isolated trees offer promise of richer collections. The farm boy helps, and we collect more smooth galls while we wonder about the varied mixture which spreads so many miles back of us. It is drizzling now, and sheets of fine snow come whirling off the mountain, but we espy a tree in the next open, and in the gathering dusk find—many naked but only two spiny galls for our collections! ”

“ In handling even such large numbers of individuals of a limited group of species, one becomes convinced that accurate information on the variability or constancy of species over wide areas, the extent of host and geographic isolation between related species, the correlation of biologic and structural facts, and the attainment of sound conclusions as to the affinities of species within any group and consequent interpretations of species and biologic phenomena cannot emanate from anything short of the most extensive data that modern facilities can provide. ”

“ Some will consider that individuals are so variable and interbreeding Mendelian races so abundant in nature that taxonomic classifications can be nothing but contrivances without biologic significance. And yet, when the Colorado of the West first cut into the Colorado Plateau the specific stocks of Cynips were in existence, and thruout the years that the Canyon has been cutting, even down onto the present, these complexes which we call species have maintained their identity. ”

“ In Acraspis all five layers are developed among the species centering about Cynips mellea, but in the other specific stocks in Acraspis the protective and parenchyma zones seem absent and the collenchyma and epidermal layers are unusually well developed.
The gall-producing stimulus, whatever its origin, is evidently selective in its effects upon particular plant tissues; and, since the gall characters are usually of subgeneric significance, it is apparent that these peculiarities of the gall-producing stimuli are of as ancient standing as any of the morphologic structures of the insects. ”

“ Of all the areas occupied by Cynipidae in the United States, this Northeastern area, the Eastern mountain country, and areas immediately adjacent to these are the only ones which had a Pleistocene history that would have provided the opportunity for the multiplication of hybrid individuals and which would have offered a subsequent isolation sufficient for the origin of new species. The apparent restriction of the hybrid Cynips to those areas seems confirmation of our explanation. ”

“ A more detailed genetic interpretation of our material must for the most part be postponed for a later paper; but we may point out that the graded series of individuals, obtained when short-winged species hybridize with long-winged stocks as with Cynips bifurca and several species in other genera on which we shall publish later, indicate that wing characters in these insects may be dependent on multiple factors or perhaps on more than one group of such factors. ”

“ Every one of the insects has been examined under the higher powers of a binocular microscope. Thousands of the specimens have been repeatedly re-examined in direct comparison with every specimen whose affinities might in any way throw light on the interpretation of the characters under observation. Exactly 16,899 of the insects and nearly all of the 54,000 galls of the genus are in our own collections where they have been available for all the comparisons and endless re-comparisons that have been necessary during the four years of intensive study given to this group of species. ”

“ Many outside, environmental factors also affect the developing organism, but the final form of the plant or animal is inherited in the sense that the inherited genes exert the primary influence on that form. It is in precisely the same sense that the physiologic or psychologic characters of species may be said to be inherited. There seems no sound basis for the oft-made suggestion that physiology is a function of structure—or structure of physiology. ”

“ Geoffroy, a contemporary of Linnaeus, made a better distinction (1762) between gall makers and parasites, altho calling the parasites Cynips and the gall makers Diplolepis. During the next century several attempts were made to fix the type of Cynips, but the only designation acceptable under the present International Rules was made by Westwood, in 1840, who named folii, probably the best known of all European gall wasps, as the type of the genus. Detailed discussion of this designation is given in the introduction to the European subgenus in this study. ”