Species Of Hawaiian Drosophila Research Articles

Cytogenetic study of three closely related species of Hawaiian Drosophila.

Cytogenetic study of three closely related species of Hawaiian Drosophila.

Qualitative and quantitative studies of pteridine eye pigments in Drosophila. Seven species of Hawaiian Drosophila and D. melanogaster

The procedure of two dimensional thin-layer chromatography followed by fluorometric quantification of pigments provides a reliable protocol for analyzing different pteridine eye pigments in species of Drosophila. Using this procedure, a new pigment [S] was discovered in five of the seven species of Hawaiian Drosophila examined. This pigment, which occurs in varying amounts, has colour and R f values very similar to the pteridines, biopterin and 2-amino-4-hydroxypterin. The ability to quantitate these pigments provides a reproducible way to uniquely characterize these files based on a biochemical profile. Most pigments appear to be correlated with light intensity, in that, as light intensity increases, the pigment amount decreases. It is hoped that this procedure can provide a new way to look at the evolutionary relationships between these species and also furnish new data about the ecological genetics of the Hawaiian Drosophila.

Qualitative and quantitative studies of pteridine eye pigments in Drosophila. A statistical analysis of fluorometric data on seven Hawaiian species

Two dimensional thin layer chromatography followed by fluorometric quantification of pteridine eye pigments promises to be a very useful methodology for biochemical taxonomy to identify the relationships among species of Hawaiian Drosophila. This protocol and the statistical interpretation of the data provide a new way to look at relationships among various species of the Genus Drosophila. They imply new relationships among groups of Drosophila species hot easily detected by other procedures, and also confirms some of the taxonomic relationships between species while at the same time providing a new window to clarify and expand other relationships. With improvements in the methodology, additional species to work with, and more precise environmental data, this tool can greatly expand our understanding of the evolutionary pathways and ecological genetics of the Hawaiian Drosophila.

Metaphase karyotype identity in four homosequential Drosophila species from Hawaii

Four recently evolved species of Hawaiian Drosophila (silvestris, heteroneura, dijferens, and planitibia) have previously been shown to be homosequential in all five polytene chromosome arms. This suggests that the changes involved in speciation are at the genic level and hence are not evident in the polytene banding sequences. Because this does not rule out the occurrence of heterochromatic differences between these homosequential species, the present study was carried out to examine this possibility. These species are now shown to have identical heterochromatin distributions in mitotic metaphase chromosomes. This proves that neither gross chromosomal rearrangements nor novel heterochromatic blocks have been involved in the divergence of these four species. A fifth, and evolutionarily more distant, species (hemipeza) belonging to the same subgroup has a significantly different heterochromatin distribution from the other four species.Key words: heterochromatin, metaphase karyotypes, Hawaiian Drosophila.

DNA/DNA Hybridization studies among six endemic Hawaiian Drosophila species

The nucleotide-sequence homology and divergence of six endemic Hawaiian Drosophila species have been studied by means of DNA/DNA hybridization experiments, using the fractionated unique and moderately repetitive sequences. The data indicate that the extent of homology between the nonrepetitive DNA sequences of D. crucigera, D. pilimana, D. engyochracea, D. silvarentis and D. picticornis confirms the taxonomic relationship established through cytological evidence. The average rate of divergence of nonrepetitive DNA sequences among Hawaiian Drosophila species is approximately 2.75 to 3.75% per million years. This value is much higher than that found among other species when divergence time is estimated on an absolute time base.

ALDEHYDE OXIDASE DISTRIBUTION IN PICTURE-WINGED HAWAIIAN DROSOPHILA: EVOLUTIONARY TRENDS.

Dipteran imaginal discs, especially those of Drosophila, are a unique system for the study of genetic control in determination and differentiation (Gehring, 1978). Although differentiation of adult structure is limited to metamorphosis, experiments utilizing clonal analysis have shown that groups of cells within imaginal discs become more and more restricted in their determination through the larval period. Morphologically, cells of the discs appear to be similar but Crick and Lawrence (1975) have hypothesized that they may differ from one another by enzyme profile which could be visualized histochemically. Major steps toward this visualization have been taken for the enzyme aldehyde oxidase (AO). A great deal is known of the biochemistry and genetic control of this enzyme in Drosophila. Much of this work is reviewed by Dickinson and Sullivan (1975). Dickinson (1971) was the first to histochemically localize AO in Drosophila melanogaster larvae and adults and find tissue-specific patterns of expression. Patterns of AO acitivity in Drosophila imaginal discs were first observed by Janning (1972, 1973) who also showed, using cell markers in gynandromorphs, that aldehyde oxidase is cell autonomous. Distribution of aldehyde oxidase in larval tissues and imaginal discs was surveyed by Kuhn and Cunningham (1978). These investigators were also able to show that in homoeotic mutants disc specific staining patterns are altered reflecting the change in determination (Kuhn and Cunningham, 1977a, 1977b). It is quite clear from these and other studies that tissue specificity of enzyme activity is a result of genetic regulation. The importance of considering regulatory as well as structural gene changes in evolution was emphasized by King and Wilson (1975). Sprey (1977) surveyed aldehyde oxidase distribution in imaginal discs of several dipterans including D. melanogaster, its sibling, D. simulans, and D. hydei. There is probably no better group of Drosophila in which to examine evolutionary trends in developmental regulation than the Hawaiian species. Precise relationships for 101 species of the picturewinged group have been determined based on banding sequences in the salivary gland polytene chromosomes (Carson et al., 1970; Carson and Kaneshiro, 1976). For these species a great deal is also known about their ecology, behavior, morphology and genetic variability. Dickinson (1979, 1980) has begun to examine these species for tissue-specific gene expression and has demonstrated cis-acting regulatory elements controlling expression of ADH and AO. We have chosen to survey ten species of picture-winged Hawaiian Drosophila, representing several branches of the phylogeny, examining them for larval tissuespecific expression of aldehyde oxidase and patterns of expression within the imaginal discs. This paper describes the AO activity patterns observed in relation to the questions: are patterns of expression species specific and do closely related species manifest similar distribution patterns?

Location of the 18/28S ribosomal RNA genes in two Hawaiian Drosophila species by monoclonal immunological identification of RNA.DNA hybrids in situ.

Using both heterologous rabbit antisera and mouse monoclonal antibody to RNA.DNA hybrids, we have mapped the in situ hybridization locus of the 18/28S ribosomal RNA fraction to a single large band on polytene autosome 3 in Drosophila heteroneura and Drosophila silvestris. This portion of the chromosome is not physically connected with the nucleolus at the end of larval salivary gland development. In mature larvae, little or no hybridization with the material in the nucleolus can be detected. In younger larvae, hybridization of the ribosomal RNA probe to the nucleolus itself can be observed. The chromosome 3 locus is the only band in the polytene genome that shows variation in size and intensity of staining between populations and species. The interband chromosome regions that are immediately distal or proximal to the 18/28S rRNA locus have been involved in a disproportionately large number of natural inversion breaks observed in the euchromatic portion of the polytene chromosome. In 104 species of Hawaiian Drosophila in which chromosome 3 polytene sequences have been determined, 15 breaks occur in these two regions. On a random basis, only one such break is expected. We propose that this locus may be flanked by substantial heterochromatic blocks which are not represented in the salivary gland chromosome.

DOES ASYMMETRICAL MATING PREFERENCE SHOW THE DIRECTION OF EVOLUTION?

The analysis of present behavior patterns is often a useful tool in our attempts to decipher the past. Studies of reproductive behavior have proven particularly fruitful in this regard, for the extent and type(s) of ethological barriers between two or more species can sometimes offer clues concerning key events in their evolutionary history. The usual approach is to obtain data on the relative willingness of individuals to mate, indicated by some type of isolation index. This index may actually be a function of both sex drive and discrimination. The strength of the isolation present-as measured by the isolation index-together with other relevant information, is then used to determine evolutionary patterns. Such investigations have shown that certain species pairs exhibit asymmetrical isolation. Asymmetrical isolation is said to exist when sexual isolation between the females of one population (population A) and the males of another population (population B) is greater than that found in the reciprocal crosses (females of population B with males of population A). One might expect that the rate of the development of sexual isolation between two populations would, by chance, occasionally be asymmetrical. Indeed, where isolation is not complete, equality of isolation between populations may be the exception rather than the rule. On the other hand, since the development of reproductive isolation is crucial to the speciation process, the presence of asymmetrical mating preferences may actually reflect the mechanism by which speciation has occurred. Toward this end, Kaneshiro (1976) and Watanabe and Kawanishi (1979) proposed models whereby they suggested that the direction of evolution can be determined by the examination of patterns of asymmetrical isolation. Kaneshiro (1976) and later Ohta (1978) uncovered asymmetry in mating preferences among several Hawaiian Drosophila species. Kaneshiro's model, upon which Ohta elaborated, suggested that the females of the putative ancestral species are more isolated from males of the putative derived species than are the derived females from the ancestral males. In 1979 Watanabe and Kawanishi offered a contrasting model based on their experimental work with the Drosophila melanogaster species group (Watanabe and Kawanishi, 1979). Here they had found an asymmetrical mating preference whereby the females of the putative derived species were more isolated from the males of the putative ancestral species than were the ancestral females from the derived males. This seemed also to be true of the published work on the virilis group. Thus, for any given set of asymmetrical isolation indices, the direction of evolution proposed by Watanabe and Kawanishi is exactly opposite to that suggested by Kaneshiro. If either of these two models is generally correct, a very powerful tool is available to researchers. Both are adequate to explain the data for which they were designed. A good test of these models would be to apply them to new data. For this purpose we will use the results of a study made on the Drosophila arizonensis-Drosophila majavensis species pair in which we investigated the reproductive relationships between various allopatric and sympatric populations of the two species (Wasserman and Koepfer, 1977). We found a much higher level of sexual isolation between sympatric populations

SEXUAL ISOLATION, SPECIATION AND THE DIRECTION OF EVOLUTION.

Kaneshiro (1976), in his study of behavioral isolation among four species of Hawaiian Drosophila, made the observation that isolation was asymmetrical between allopatric species. That is, between any allopatric pair of species, sexual isolation was strong in one direction but showed weak or no isolation in the other reciprocal. Based on the assumption that elements of behavior are lost during founder events due to severe drift conditions and the genetic revolution which accompanies such events, Kaneshiro proposed a hypothesis to infer the direction of evolution for the four species studied. Ohta (1978) analyzed sexual isolation among six populations of two other Hawaiian Drosophila species and observed striking asymmetry in pair-wise combinations of four of the six. By using Kaneshiro's (1976) hypothesis, Ohta was able to propose a uni-directional phylogeny for the six populations of the grimshawi complex of species. A preliminary search of the literature on ethological isolation between populations of Drosophila indicates that one-sided mating preference or asymmetrical isolation is not an uncommon phenomenon. Re-evaluation of these data in terms of the hypothesis proposed by Kaneshiro (1976) complements phylogenetic interpretations inferred from various other techniques. This paper elaborates the hypothesis proposed by Kaneshiro (1976). Additional evidence which appear to support his ideas will be presented. A discussion of the origin of premating isolation mechanisms is presented first to emphasize the role of sexual isolation in the speciation process.

Coadaptive Gene Complexes in Incipient Species of Hawaiian Drosophila

The degree of postmating isolation existing among allopatric populations belonging to two species of endemic Hawaiian Drosophila was investigated. Drosophila grimshawi is unusual among picture-winged Hawaiian Drosophila in that it is widely distributed in the archipelago with populations on the islands of Kauai, Oahu, Lanai, Molokai, and Maui. The second species, D. pullipes, is very closely related and is confined to the island of Hawaii. Kauai and Oahu D. grimshawi and D. pullipes are known to be ovipositional specialists, utilizing only one genus of plant. Populations of D. grimshawi from Lanai, Molokai, and Maui are generalists and oviposit on several plants of a number of different families. Hybridizations among stocks representing four of the six allopatric populations (i.e., Oahu, Maui, and Molokai D. grimshawi and D. pullipes) were completed in all reciprocal combinations; and, in addition, Kauai D. grimshawi was crossed to Oahu D. grimshawi. The F1 hybrid progeny were used to produce an F2 and backcrosses to parental males and females. Although crosses between ecologically different D. grimshawi stocks resulted in full F1 male fertility, breakdown was observed in the F2 and backcross males. This was not observed in crosses between ecologically similar populations. Fertility breakdown in these intraspecific crosses was consistently greatest in the F2's, followed by the backcross to the parental males, and least in the backcross to the parental females. This progressive breakdown, based on the assumption of no crossover recombination in Hawaiian Drosophila males, was attributed to the breakup of two differing sets of coadaptive gene complexes. It is further suggested that the coadaptive gene complexes of populations with the same adaptive peaks are identical or at least similar enough so as not to have yet evolved reproductive isolation. The D. pullipes stock was found to produce completely sterile F1 males when hybridized with all stocks except Molokai, in which approximately 70% of the F1 males were fertile. Added to the hybrid sterility, crosses involving D. pullipes females showed a reduction in hybrid viability.

Regulation of the tissue specificity of an enzyme by a cis-acting genetic element: evidence from interspecific Drosophila hybrids.

Homologous genes for alcohol dehydrogenase (alcohol:NAD+ oxidoreductase, EC 1.1.1.1) are expressed in qualitatively different patterns during the development of two closely related species of Hawaiian Drosophila. In interspecific hybrids, each parental structural allele is expressed according to the developmental program characteristic of the species from which it is derived. This provides strong evidence for a cis acting control element.

On Premating Isolation Between Two Closely Related Species of Hawaiian Drosophila

On Premating Isolation Between Two Closely Related Species of Hawaiian Drosophila

GENETIC VARIATION IN HAWAIIAN DROSOPHILA VI. SEASONALLY-DEPENDENT GENE CHANGES IN DROSOPHILA MIMICA.

Relatively few studies have been done on the behavior of gene-allozyme (electromorph) systems over time in natural populations of Drosophila. Instead, most studies have concentrated on looking at geographical differences between populations of Drosophila in attempts to demonstrate the selective advantage of allozyme variation. In such studies, however, migration and its accompanying gene flow may confound the selective picture. The study of seasonally-dependent genic changes within a population can offer an advantage where migration effects can be minimized and where specific environmental and ecological parameters that have the potential to drive gene changes in a seasonal cyclical manner lend themselves to observation. These types of studies may provide evidence as to the nature of microevolution within populations. Species which lend themselves to the study of seasonally-dependent gene changes must satisfy the above criteria. Two sympatrically occurring, endemic Hawaiian Drosophila species, D. mimica and D. engyochracea, are ideal in this regard. The two species are found in Volcano National Park on the island of Hawaii (Fig. 1). There are only two confirmed populations, both of finite size, both comparatively young in an evolutionary sense, and both separated from each other by a volcanic event some 2,100 years ago (Mueller-Dombois and Lamoureaux, 1967). I have studied both species over approximately two years. For economical reasons, I will concentrate on the data for D. mimica in this report and ask the following questions: (1) How extensive is the allozyme variability within the two populations? (2) Do patterns of genetic change in one population reflect genetic events in the second? (3) Do these changes correlate to specific weather variables obtained concurrently with the genetic data? and (4) Do single locus genetic changes affect population heterozygosity as estimated from electromorph frequencies? The answers to these questions not only are of broad theoretical interest but may throw some light on microevolutionary processes in finite populations such as often characterize the Hawaiian Drosophilidae.

CYTOGENETICS AND EVOLUTION OFSIMULIUM ORNATIPESSKUSE (DIPTERA: SIMULIIDAE). II. TEMPORAL VARIATION IN CHROMOSOMAL POLYMORPHISMS AND HOMOSEQUENTIAL SIBLING SPECIES

The discovery of homosequential species of Hawaiian Drosophila which share identical polytene chromosomes and metaphase karyotypes (Carson et al., 1967), established that overt chromosomal change need not accompany speciation. These homosequential species are morphologically distinct and are, therefore, not sibling species. The genetic divergence that has obviously occurred must therefore have involved only gene mutations. Within the genus Drosophila not all homosequential species, as defined by polytene chromosome banding patterns, share identity of metaphase karyotypes. Thus in the D. pachea group homosequential species show striking heterochromatin differences in their metaphase karyotypes (Ward and Heed, 1970). Since heterochromatic sequences are generally underreplicated relative to euchromatin in polytene chromosomes of Drosophila (Cordeiro et al., 1975; Gall et al., 1974; Rudkin, 1972), no differences in polytene chromosome structure are evident despite the considerable divergence revealed by mitotic karyotypes. Thus where possible, analysis of both diploid and polytene chromosomes should be carried out. In the Simuliidae mitotic karyotypes are remarkably conservative being identical in species of several different genera (Rothfels, 1956). On the other hand, the analysis of polytene chromosomes has shown the existence of sibling species

ETHOLOGICAL ISOLATION AND PHYLOGENY IN THE GRIMSHAWI SPECIES COMPLEX OF HAWAIIAN DROSOPHILA.

The ethological isolation among six allopatric populations, comprised of two closely related species of Hawaiian Drosophila, was measured and used to analyze the phylogenetic relationships among these populations. The two species used in this study are included in the picture-winged species group (Carson and Stalker, 1968). In its present taxonomic status, Drosophila grimshawi Oldenberg is the only species of this group that inhabits all the accessible major islands (i.e. Kauai, Oahu, Maui, Lanai, and Molokai) except Hawaii. On the island of Hawaii a very closely related species, D. pullipes Hardy and Kaneshiro, is found. The only distinguishing morphological character between grimshawi and pullipes is reported to be the coloration of the legs and pleurae (Hardy and Kaneshiro, 1972). A cytological comparison of the six populations showed a strong similarity between them. Carson and Stalker (1968) and Carson and Sato (1969) found grimshawi from the islands of Lanai, Maui, and Molokai (these islands known collectively as the complex of islands) to possess the standard polytene chromosomal sequence as well as one polymorphic inversion on the fourth chromosome (4A). Later studies (Carson et al., 1970) of grimshawi populations from Oahu and Kauai and of pullipes populations showed that they are fixed for the standard chromosomal sequence. That is, they differ from the Maui complex populations only in lacking the polymorphic 4A inversion sequence. For the grimshawi populations the comparison of metaphase karyotypes showed the five rods and one dot haploid chromosomal complement characteristic of most of the picture-winged species (Clayton, 1971). Therefore, contrary to the findings of Craddock (1974), no consistent morphological or cytological differences were detected among the insular populations of grimshawi. Montgomery (1975) reared the adults of both species from field collected substrates and discovered an interesting ecological differentiation. The adults of the Maui complex grimshawi were obtained from the substrates representing 12 different plant families. However, grimshawi from Oahu and Kauai and pullipes from the island of Hawaii were reared exclusively from the rotting bark of trees of the genus Wikstroemia (family Thymeleaceae). On the basis of these studies grimshawi from the Maui complex have been termed ovipositional generalists whereas pullipes from Hawaii and grimshawi from Oahu and Kauai are ovipositional specialists. In addition to this ecological differentiation, Ringo (1974; 1976) observed jousting behavior differences among the males of some of these populations. Using stocks of Maui, Molokai, and Oahu grimshawi and pullipies, Ringo observed a greater difference in jousting displays between generalist and specialist males than between species. That is, although Maui and Molokai grimshawi had similar jousting displays as did Oahu grimshawi and pul1 Published with the approval of the Director of the Hawaii Agricultural Experiment Station as Journal Series Number 2132. 2 Present address: Department of Primary Industries, Entomology Branch, Meiers Road, Indooroopilly, Brisbane, Queensland, Australia 4068.

A Multivariate Analysis of Behavioral Divergence Among Closely Related Species of Endemic Hawaiian Drosophila

A Multivariate Analysis of Behavioral Divergence Among Closely Related Species of Endemic Hawaiian Drosophila

A MECHANISM OF CHROMOSOMAL REARRANGEMENTS: THE ROLE OF HETEROCHROMATIN AND ECTOPIC JOINING

Clusters of breaks at certain intercalary heterochromatin sites producing chromosomal rearrangements are reported in four endemic species (24 strains) of Hawaiian Drosophila. In laboratory strains of these species we observed some types of changes in chromosome structure that were predicted in our earlier studies (Yoon and Richardson 1976a).-We outline the pseudochromocenter model for the production of chromosomal rearrangements. First, nonhomologous sites that are heterochromatic and contain similar base sequences of highly repetitious DNA join in a chromocenter-like configuration. Second, chromatid exchanges by breakage and reunion occur at the ectopically joined sites. Based on this model, one expects many new chromosomal rerrangements, some of which have been observed and used to differentiate species.-Inversions with identical breakpoints may occur with much greater frequency than previously assumed. Chromosome phylogenies, based on the assumption that inversions are unique events, still would be accurate if the incorporation of an inversion into the karyotype was rare. This would be the case if a rare combination of genes was necessarily contained in the inversion before it was likely to be incorporated into the gamete pool and thereby become a characteristic feature of the species.

Niche Width and Genetic Variation in Hawaiian Drosophila

With the use of regression techniques, associations are found between genetic variability and the number of oviposition sites utilized by two exotic and 16 endemic species of Hawaiian Drosophila. An additional association is found for altitudinal location of populations of D. setosimentum and genetic variability. These findings are interpreted as providing support for the niche width-genetic variability hypothesis. Additional studies to confirm these findings and establish their genetic basis are suggested.

GENETIC ANALYSIS OF THE MORPHOLOGICAL DIFFERENCES BETWEEN TWO INTERFERTILE SPECIES OF HAWAIIAN DROSOPHILA.

Most biological species are reproductively isolated from their closest relatives both in nature and in the laboratory. Thus direct analysis of the genetic differences between them is not possible by Mendelian methods. Inferences as to the extent of genetic differences between species can be based on comparative biochemical studies (e.g. Ayala, 1974) or on polytene chromosome sequencing (Clayton et al., 1972). In key instances of certain very close species, however, both these techniques fail to be useful. Morphologically and behaviorally distinct species are known which cannot be distinguished either by allozymes or chromosomes (Carson et al., 1975). Indeed, the biochemical similarity between such obviously distant species as man and chimpanzee have led to the postulating of regulatory rather than structural genes as the basis of the important biological differences between species (King and Wilson, 1975). I report here the results of hybridization experiments between two morphologically and behaviorally distinct species of Hawaiian Drosophila. By using methods to overcome ethological isolation, it is possible to obtain reciprocal hybrids which are fertile in both sexes (Ahearn and Val, 1975). F2's and backcrosses reveal considerable segregating polygenic differences in morphology. These species show close cytological and electrophoretic similarity. Accordingly, I believe that the character segregations observed represent polygenes regulating morphology rather than differences in chromosome sequences or in structural proteins. The species considered in the present work are Drosophila heteroneura (Perkins, 1910) and Drosophila silvestris (Perkins, 1910). They are endemic to the Island of Hawaii where they are sympatric in many localities. They belong to a cluster of homosequential species of Hawaiian picture-winged Drosophila in the planitibia subgroup. Different aspects of this cluster have been the subject of several recent studies. The species constitute one of the end branches in Carson's chromosome phylogeny (Clayton et al., 1972). At the present time, four species are considered to belong to it: differens Hardy and Kaneshiro (1975), from Molokai; planitibia Hardy (1966), from Maui; heteroneura and silvestris from the Island of Hawaii. D. differens, just recently described as a new species, was referred to as planitibialike from Molokai by Ahearn et al. (1974), Craddock (1974a,b) and Johnson et al. (1975). Speciation in this cluster of species has been discussed in Carson (1970), Carson et al. (1970), Carson (1974), Craddock (1974a,b) and is the subject of an extensive work by Kaneshiro (in preparation). D. heteroneura and D. silvestris constitute a case of sympatric species from which fertile hybrids in both reciprocal directions can be obtained in the laboratory with relative facility. Premating barriers are responsible for reproductive isolation between them, as has been shown in a study of their ethological isolation by Ahearn et al. (1974), and discussed by Craddock (1974a,b). The full fertility of male and female laboratory hybrids makes these species suitable for studying the inheritance of species differences.

Natural Hybridization between a Sympatric Pair of Hawaiian Drosophila

Natural interspecific hybrids between two closely related species of Hawaiian Drosophila, heteroneura and silvestris, have been collected from the Kahuku Ranch area on the Island of Hawaii. Despite full fertility of both sexes of these hybrid specimens, hybridization is apparently not extensive. Investigations of the degree of introgression between these two species and of environmental factors which might contribute to the breakdown of isolating mechanisms are continuing.