John A. Moore

The Frogs of Eastern New South Wales

The frogs of eastern New South Wales , The frogs of eastern New South Wales , مرکز فناوری اطلاعات و اطلاع رسانی کشاورزی

COMPETITION BETWEEN DROSOPHILA MELANOGASTER AND DROSOPHILA SIMULANS. I. POPULATION CAGE EXPERIMENTS

Drosophila melanoqaster and Drosophila simulans are sibling species that were not distinguished from each other until Sturtevant described the latter in 1919. Their remarkable morphological similarity is well known to Drosophila geneticists. As a measure of their near identity it might be mentioned that several investigators experimented with strains of both species simultaneously and were unaware that they were not dealing exclusively with melanogaster. According to Sturtevant (1920), it was C. B. Bridges who first noticed the peculiar male genitalia of simulans. This feature allows easy separation of the males of the two species but there is no reliable and rapid means of distinguishing females. The close similarity of melanogaster and simulans is not restricted to externals. There is a corresponding parallel in genetics (Sturtevant, 1920, 1921a, 1921b, 1929; and Sturtevant and Plunkett, 1926). Both species have four linkage groups and many of the mutations that have arisen in simulans are allelomorphs of those in melanogaster. Comparisons of the salivary gland chromosomes were made by Patau (1935), Kerkis (1936, 1937) and Horton (1939). A study of the hybrids showed a striking similarity of the salivary chromosome bands of. the two species. There is one large inversion in the third chromosome which previously had been detected genetically by Sturtevant. In addition there are 5 very short inversions, 4 instances where the bands differ at the free ends of the chromosomes, and 14 regions where the chromosomes do not synapse in spite of the fact that the chromosomes appear to be identical. Hybridization is difficult. Sturtevant (1929) reported that offspring are obtained in from 10 to 40 per cent of the melanogaster ~ X simulans ~ crosses and in not over 2 per cent of the simulans ~ X melanogaster ~ crosses. The first cross produces females and a few exceptional males. The second produces many males and a few females. All hybrids are sterile. So far as mating preference is concerned, Sturtevant found that males will court females of the opposite species but females prefer to mate with members of their own kind. When Sturtevant published his monograph on simulans in 1929, all geographical records known to him were from the western hemisphere. Subsequently, simulans has been recorded from Europe, Australia and Asia (Kikkawa and Peng, 1938) . It is probable that melanogaster and simulans are widely distributed in tropical and temperate zones throughout the world. In most regions they are commonly associated with human habitations and natural areas contiguous with human habitations. Some ecological differences between simulans and melanoqaster, which may be of importance in competition under natural conditions, have been noted by several authors. Patterson (1943) studied an area near Austin, Texas, where both species occur. Simulans is more abundant in the late autumn months. During the coldest period of the winter the population size of both species is greatly reduced. With the subsequent temperature increases the

Further Studies on Rana pipiens Racial Hybrids

The data presented in this paper are a continuation of a study of geographic variation of adaptations in Rana pipiens Schreber and of hybrids arising from interpopulation crosses. The eggs and jelly mass of Costa Rica pipiens are described. They are of the northern, cold-adapted type. Hybrids resulting from the cross Vermont [female] x Colorado [male] are normal. Hybrids resulting from the cross Vermont [female] x Costa Rica [male] have minor defects. This result is discussed in light of the previous cases of defective hybrids arising from crosses of northern and southern pipiens.

Geographic and Genetic Isolation in Australian Amphibia

The continent of Australia has a moist section along the east coast and another in the south-west corner. These two areas are separated by a broad arid zone that acts as an effective barrier for those species of amphibia that require a moist environment. Hyla aurea is found in both of the moist zones but is absent from the arid center. The two populations, which are now discontinuous, probably have not been connected in recent times. There has been almost no morphological differentiation during the period of isolation but genetic divergence has reached the point where the two populations are behaving as different species. Crosses of east Australia x south-west Australia individuals result in complete hybrid inviability. Similar experiments have been conducted with Crinia signifera, a species showing the same type of distribution, and the results are nearly the same. Crosses of east Australia x south-west Australia individuals result in considerable inviability of the progeny. On the island of Tasmania Crinia signifera and the very similar Crinia tasmaniensis occur. Crosses of east Australian signifera x Tasmania signifera gives normal progeny. Crosses of east Australia signifera x Tasmania tasmaniensis results in complete hybrid inviability. These data suggest a double invasion of Tasmania by signifera. The first group evolved into tasmaniensis but the second has not diverged from the mainland type. The south-west Australian analogue of the eastern Hyla aurea should be known as Hyla raniformis (Parker). No name is available for the southwest Australian species formerly included in Crinia signifera. A new name, Crinia insignifera, is proposed.

Adaptative Differences in the Egg Membranes of Frogs

THE influence of temperature in limiting geographical distribution is apparent in many animal groups. One species will be characteristic of a region where the temperature fluctuates around a certain mean, while yet another is found under warmer or colder conditions. To throw light on some aspects of this problem a study is being made of physiological differences among members of the Salientian genus Rana that inhabit northeastern North America. These frogs differ in the extent of their northern distribution and, in a given locality in the time at which they spawn. It has previously been shown (Moore, 1938) that marked differences exist in the embryonic temperature tolerance, northern frogs having lower minimal and maximal temperatures for normal development. Furthermore, northern species compensate for the retarding influence of the low temperature of their environment on development, by a rapid rate of growth (Table 1). The present study is concerned with modifications of the jelly envelopes which limit the developing embryos to particular temperature conclitionis.

An Analytical Study of the Geographic Distribution of Rana septentrionalis

Where moisture is a limiting factor, xerophytic plant communities possess fewer species than do the communities of mesophytic regions, but the number of communities per unit of area is likely to be larger than in regions of adequate moisture. This promotes geographic separation of species populations and races, and thus might be expected to speed up evolution. Evidence that certain mesophytic types are derived from xerophytic ancestors is presented for the genera Scorzonera and Tragopogon of the Compositae, tribe Cichorieae, and for certain genera of the subfamilies Mimosoideae and Caesalpinoideae of the family Leguminosae. The evidence in the latter family is derived chiefly from the development of both adult and seedling leaves.

STUDIES IN THE DEVELOPMENT OF FROG HYBRIDS. IV. COMPETENCE OF GASTRULA ECTODERM IN ANDROGENETIC HYBRIDS

1. In an effort to dissociate the factors responsible for the failure of development in Rana pipiens ♀ x Rana sylvatica ♂ hybrids, a study has been made of the development of haploid embryos composed of pipiens cytoplasm and sylvatica chromosomes. These androgenetic hybrids develop only to the late blastula stage.2. The competence of the presumptive ectoderm of these haploid hybrids was tested by transplantation to neurulae of Rana palustris. The results indicated a total lack of competence.3. Aside from the main problem with which the paper is concerned, it was found that the various classes of embryos used could be arranged in order of decreasing competence of the presumptive ectoderm. The sequence was as follows: diploid pipiens, haploid pipiens, pipiens ♀ x sylvatica ♂ diploid hybrids and (pipiens ♀) x sylvatica ♂ haploid hybrids.

Temporal stability of third-chromosome inversion frequencies in Drosophila persimilis and D. pseudoobscura

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THE DROSOPHILA OF SOUTHERN CALIFORNIA. I. COLONIZATION AFTER A FIRE

During August 27-31, 1974, approximately 70 square kilometers of chaparral and forest on the western side of the San Jacinto Range of southern California burned in the devastating Soboba fire. The affected area extended from the base of the mountain to the edge of the James San Jacinto Mountains Reserve-part of the University of Californias Natural Land and Water Reserve System. The fire was intense, killing all the conifers and those portions of other trees and plants above ground. The surface was left with a cover of fine ash that averaged about 10 centimeters in depth in the area we were to study. Seemingly all sedentary life above ground had been destroyed (Fig. 1). The San Jacinto Range is home to a rich and varied population of Drosophila. In fact, it is one of the classic sites where in the 1930s, 40s and 50s Th. Dobzhansky, Carl Epling, and their associates carried out many of their fundamental observations on the biology of natural populations of Drosophila pseudoobscura. Our studies were designed to answer two main questions: (1) what is the pattern of recolonization of a burned area by Drosophila and (2) what have been the changes in Drosophila populations, if any, since Dobzhansky studied them in the late 1930s and early 1940s?

Hybridization Experiments Involving Rana dunni, Rana megapoda, and Rana pipiens

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