Hawaiian Picture-winged Drosophila Research Articles

Hawaiian picture-winged Drosophila exhibit adaptive population divergence along a narrow climatic gradient on Hawaii Island.

Anthropogenic influences on global processes and climatic conditions are increasingly affecting ecosystems throughout the world.Hawaii Island’s native ecosystems are well studied and local long‐term climatic trends well documented, making these ecosystems ideal for evaluating how native taxa may respond to a warming environment.This study documents adaptive divergence of populations of a Hawaiian picture‐winged Drosophila, D. sproati, that are separated by only 7 km and 365 m in elevation.Representative laboratory populations show divergent behavioral and physiological responses to an experimental low‐intensity increase in ambient temperature during maturation. The significant interaction of source population by temperature treatment for behavioral and physiological measurements indicates differential adaptation to temperature for the two populations.Significant differences in gene expression among males were mostly explained by the source population, with eleven genes in males also showing a significant interaction of source population by temperature treatment.The combined behavior, physiology, and gene expression differences between populations illustrate the potential for local adaptation to occur over a fine spatial scale and exemplify nuanced response to climate change.

Mapping Genomic Scaffolds to ChromosomesUsing Laser Capture Microdissection inApplication to Hawaiian Picture-WingedDrosophila

Next-generation sequencing technologies have led to a decreased cost and an increased throughput in genome sequencing. Yet, many genome assemblies based on short sequencing reads have been assembled only to the scaffold level due to the lack of sufficient chromosome mapping information. Traditional ways of mapping scaffolds to chromosomes require a large amount of laboratory work and time to generate genetic and/or physical maps. To address this problem, we conducted a rapid technique which uses laser capture microdissection and enables mapping scaffolds of de novo genome assemblies directly to chromosomes in Hawaiian picture-winged Drosophila. We isolated and sequenced intact chromosome arms from larvae of D. differens. By mapping the reads of each chromosome to the recently assembled scaffolds from 3 Hawaiian picture-winged Drosophila species, at least 67% of the scaffolds were successfully assigned to chromosome arms. Even though the scaffolds are not ordered within a chromosome, the fast-generated chromosome information allows for chromosome-related analyses after genome assembling. We utilize this new information to test the faster-X evolution effect for the first time in these Hawaiian picture-winged Drosophila species.

Quantifying the effects of an invasive thief ant on the reproductive success of rare Hawaiian picture-winged flies

Threats to endangered insect species that act independently of those associated with habitat loss are often suspected, but are rarely confirmed or quantified. This may hinder the development of the most effective recovery strategies, which are increasingly needed for listed insects. Since 2006, 14 species of flies within the large, showy Hawaiian picture-winged Drosophila group have been added to the US threatened and endangered species list. Many of these species are thought to be limited by host plant rarity, but also by predation on immature stages by invasive ants. We tested the latter hypothesis with a field experiment involving Drosophila crucigera, a more common surrogate for sympatric endangered species, and the invasive ant Solenopsis papuana, on the island of Oʻahu. We established ant suppression and control plots across three forest sites. Within each plot we placed a host plant branch piece, into which lab-reared flies had oviposited, and subsequently tracked weekly emergence of adults. Numbers of flies that emerged were 2.4 times higher in ant-suppressed plots than in control plots; this 58% reduction in survival from egg to adult in the presence of ants was similar across all three sites. Among plots, numbers of emerged flies exhibited a pattern suggesting that the detrimental effect of ants is density dependent. These results confirm that S. papuana, and possibly other invasive ant species, can strongly impact the reproductive success of Hawaiian picture-winged Drosophila. They also point to several management actions, beyond habitat restoration, that may improve the recovery of these imperiled flies.

A Test for Gene Flow among Sympatric and Allopatric Hawaiian Picture-Winged Drosophila

The Hawaiian Drosophila are one of the most species-rich endemic groups in Hawaii and a spectacular example of adaptive radiation. Drosophila silvestris and D. heteroneura are two closely related picture-winged Drosophila species that occur sympatrically on Hawaii Island and are known to hybridize in nature, yet exhibit highly divergent behavioral and morphological traits driven largely through sexual selection. Their closest-related allopatric species, D. planitibia from Maui, exhibits hybrid male sterility and reduced behavioral reproductive isolation when crossed experimentally with D. silvestris or D. heteroneura. A modified four-taxon test for gene flow was applied to recently obtained genomes of the three Hawaiian Drosophila species. The analysis indicates recent gene flow in sympatry, but also, although less extensive, between allopatric species. This study underscores the prevalence of gene flow, even in taxonomic groups considered classic examples of allopatric speciation on islands. The potential confounding effects of gene flow in phylogenetic and population genetics inference are discussed, as well as the implications for conservation.

Hybrid sterility and evolution in Hawaiian Drosophila: differential gene and allele-specific expression analysis of backcross males.

The Hawaiian Drosophila are an iconic example of sequential colonization, adaptive radiation and speciation on islands. Genetic and phenotypic analysis of closely related species pairs that exhibit incomplete reproductive isolation can provide insights into the mechanisms of speciation. Drosophila silvestris from Hawai'i Island and Drosophila planitibia from Maui are two closely related allopatric Hawaiian picture-winged Drosophila that produce sterile F1 males but fertile F1 females, a pattern consistent with Haldane's rule. Backcrossing F1 hybrid females between these two species to parental species gives rise to recombinant males with three distinct sperm phenotypes despite a similar genomic background: motile sperm, no sperm (sterile), and immotile sperm. We found that these three reproductive morphologies of backcross hybrid males produce divergent gene expression profiles in testes, as measured with RNA sequencing. There were a total of 71 genes significantly differentially expressed between backcross males with no sperm compared with those backcross males with motile sperm and immotile sperm, but no significant differential gene expression between backcross males with motile sperm and backcross males with immotile sperm. All of these genes were underexpressed in males with no sperm, including a number of genes with previously known activities in adult testis. An allele-specific expression analysis showed overwhelmingly more cis-divergent than trans-divergent genes, with no significant difference in the ratio of cis- and trans-divergent genes among the sperm phenotypes. Overall, the results indicate that the regulation of gene expression involved in sperm production likely diverged relatively rapidly between these two closely related species.

Genomic Signatures of Speciation in Sympatric and Allopatric Hawaiian Picture-WingedDrosophila

The Hawaiian archipelago provides a natural arena for understanding adaptive radiation and speciation. The Hawaiian Drosophila are one of the most diverse endemic groups in Hawaiì with up to 1,000 species. We sequenced and analyzed entire genomes of recently diverged species of Hawaiian picture-winged Drosophila, Drosophila silvestris and Drosophila heteroneura from Hawaiì Island, in comparison with Drosophila planitibia, their sister species from Maui, a neighboring island where a common ancestor of all three had likely occurred. Genome-wide single nucleotide polymorphism patterns suggest the more recent origin of D. silvestris and D. heteroneura, as well as a pervasive influence of positive selection on divergence of the three species, with the signatures of positive selection more prominent in sympatry than allopatry. Positively selected genes were significantly enriched for functional terms related to sensory detection and mating, suggesting that sexual selection played an important role in speciation of these species. In particular, sequence variation in Olfactory receptor and Gustatory receptor genes seems to play a major role in adaptive radiation in Hawaiian pictured-winged Drosophila.

Sexual Selection, Epistasis and Species Boundaries in Sympatric Hawaiian Picture-winged Drosophila

The Hawaiian picture-winged flies in the genus Drosophila are a spectacular example of rapid evolutionary diversification in which sexual selection is considered an important mechanism for reproductive isolation and speciation. We investigated the behavioral reproductive isolation of two closely related and sympatric Hawaiian picture-winged Drosophila species, D. silvestris and D. heteroneura, which are known to hybridize in nature and produce viable and fertile hybrids. We compared the mating success of parental, F1 and backcross males in pairings with D. heteroneura females. The F1 males were produced by mating D. heteroneura males with D. silvestris females, and the backcross males were produced by mating F1 females with D. heteroneura males. The mating success of backcross males paired with D. heteroneura females were significantly reduced relative to that of parental and F1 males. This reduced mating success occurred primarily at a late stage of courtship where female choice of mate may be important. Two- and three-gene models demonstrate that epistasis involving a few genes could account for the observed variation in male mating success. These results are consistent with negative epistasis in the backcross generation and support the importance of sexual selection and negative epistasis in the evolution and maintenance of these species.

Population structure and genetic diversity in two species of Hawaiian picture-winged Drosophila

Over the last several decades many picture-winged Drosophila have become less common in both geographical distribution and local population size (pers. obs., Foote pers. comm., Montgomerey pers. comm.). Here we report on a study of two Hawaiian Drosophila species, D. engyochracea, and D. hawaiiensis, to determine the impact that changes in population sizes over the past thirty years have had on the genetic diversity of these species. D. engyochracea is known from only two locations on the Island of Hawai‘i (Kipuka Ki and Kipuka Pua‘ulu), while D. hawaiiensis is currently more wide spread across Hawai‘i Island. We collected 65 D. hawaiiensis and 66 D. engyochracea from two forest patches (kipuka) isolated by a 400 year old volcanic ash deposit. DNA sequence data for 515 bases of the mitochondrial gene COII was analyzed for both species to estimate relative total genetic diversity as well as inter-kipuka gene flow. The more wide spread species, D. hawaiiensis, has more genetic diversity (23 vs. 11 unique haplotypes) than the rarer species, D. engyochracea. The distribution of haplotypes in the kipuka is consistent with more gene flow in D. engyochracea than in D. hawaiiensis. Phylogenetic analysis indicates a small number of individuals morphologically identified as one species but have DNA sequence diagnostic for the other species. These results are consistent with these individuals being descendant from hybrids between species.

Variation in male wing song characters inDrosophila plantibia (Hawaiian picture-wingedDrosophila group)

The males of most species of the HawaiianDrosophila planitibia group produce songs when vibrating their wings during courtship. In four of the most recently evolved species,D. differens, D. planitibia, D. heteroneura, andD. silvestris, these songs are simple in structure and possess a higher and more variable carrier frequency than the songs of the more ancestral species of the group. In the present paper, we studied the variation in wing song production and song characters in aD. planitibia population. Some males vibrated their wings at a very low amplitude or slow speed, producing no detectable sound. Other males produced sound bursts varying in carrier frequency and burst length. The carrier frequency of the song depended mainly on the wing posture of the male during wing vibrations and was consistent for individual males. Variation between males of different isofemale progenies was not significant in any measured song trait. Songs of the males recorded in the present study differed, however, from songs of the males of a laboratory strain recorded earlier.

Courtship songs of the picture-winged Drosophila planitibia subgroup species

Abstract. The Drosophila planitibia subgroup belongs to the endemic Hawaiian picture-winged Drosophila species group. The males of this subgroup may produce sounds by fanning or vibrating their wings or by bobbing the abdomen. These wing songs fall into three categories: pulse song, phrase song and sound bursts. Among the most primitive species only D. obscuripes males produce sounds: a low-frequency phrase song. In one intermediate species D. neoperkinsi, the males produce all three songs, while in the other species the males use different combinations of the songs: only the phrase song, the pulse song plus the phrase song or the pulse song plus the sound burst. The males of the advanced species produce only sound bursts. The fact that the males of different lineages use similar kinds of songs in their courtship suggests that all three songs have evolved before the evolution of the intermediate and advanced species. During the speciation processes some of the wing songs have been omitted from the courtship rituals of the evolving species, while the remaining songs have become less variable and more species-specific.

Evolution of regulatory genes and patterns: relationships to evolutionary rates and to metabolic functions.

In an effort to understand the forces shaping evolution of regulatory genes and patterns, we have compared data on interspecific differences in enzyme expression patterns among the rapidly evolving Hawaiian picture-winged Drosophila to similar data on the more conservative virilis species group. Divergence of regulatory patterns is significantly more common in the former group, but cause and effect are difficult to discern. Random fixation of regulatory variants in small populations and/or during speciation may be somewhat more likely than divergence driven by selection. Within the picture-winged group, we also have compared enzymes that fulfill different metabolic roles. There are highly significant differences between individual enzymes, but no obvious correlations to functional categories.

Rates of DNA change and phylogeny from the DNA sequences of the alcohol dehydrogenase gene for five closely related species of Hawaiian Drosophila.

The sequence of 1.6 kb of DNA surrounding the alcohol dehydrogenase (Adh) gene from five species of the Planitibia subgroup of the Hawaiian picture-winged Drosophila, with estimated divergence times of 0.4-5.1 Myr, has been determined. The gene trees which were found by using the sequence divergence from different regions of the sequences are generally in accord with the phylogeny proposed for these species when chromosomal inversions and island of origin are used. One of the species (D. picticornis) appears to be more distant from the other species in this group than they are from a member of the Grimshawi group (D. affinidisjuncta) which is chromosomally more distant. Two of the species (D. differens and D. plantibia) show heterogeneity in the nucleotide changes in the Adh coding region, heterogeneity which is interpreted to be due to a gene conversion or recombination after hybridization between the two species. The minimal rate of nucleotide substitution of synonymous nucleotides and of nontranscribed nucleotides downstream from the coding region is estimated as 1.5 x 10(-8) and 1.1 x 10(-8) substitutions/nucleotide/year, respectively. This rate is two to three times the maximal rate estimated for mammalian synonymous substitutions.

Tissue-specific expression phenotypes of Hawaiian Drosophila Adh genes in Drosophila melanogaster transformants.

Interspecific differences in the tissue-specific patterns of expression displayed by the alcohol dehydrogenase (Adh) genes within the Hawaiian picture-winged Drosophila represent a rich source of evolutionary variation in gene regulation. Study of the cis-acting elements responsible for regulatory differences between Adh genes from various species is greatly facilitated by analyzing the behavior of the different Adh genes in a homogeneous background. Accordingly, the Adh gene from Drosophila grimshawi was introduced into the germ line of Drosophila melanogaster by means of P element-mediated transformation, and transformants carrying this gene were compared to transformants carrying the Adh genes from Drosophila affinidisjuncta and Drosophila hawaiiensis. The results indicate that the D. affinidisjuncta and D. grimshawi genes have relatively higher levels of expression and broader tissue distribution of expression than the D. hawaiiensis gene in larvae. All three genes are expressed at similar overall levels in adults, with differences in tissue distribution of enzyme activity corresponding to the pattern in the donor species. However, certain systematic differences between Adh gene expression in transformants and in the Hawaiian Drosophila are noted along with tissue-specific position effects in some cases. The implications of these findings for the understanding of evolved regulatory variation are discussed.

High-frequency clicks of Hawaiian picture-winged Drosophila species

In this study, it is shown that the males of several picture-winged Drosophila subgroup species produced high-frequency clicking sounds when courting females. At the beginning of the courtship, the males may semaphore or vibrate their wings with a large amplitude, producing no audible sounds. After these ‘preliminary’ wing vibrations the males set their wings backwards in a normal resting position and vibrate them with a small amplitude, producing loud clicking sounds (up to 15000 cps), which differ from all Drosophila sounds described so far in both their spectral and their temporal structure. When producing these sounds the males always touch the abdomen of the female with their front legs, which might help the females receive the sounds as vibrational signals.

Tissue-specific regulatory differences for the alcohol dehydrogenase genes of Hawaiian Drosophila are conserved in Drosophila melanogaster transformants.

Naturally occurring regulatory variation is a source of genetic variability that is well documented but poorly understood. Two members of the Hawaiian picture-winged Drosophila, D. affinidisjuncta and D. hawaiiensis, display markedly different levels of alcohol dehydrogenase (alcohol: NAD+ oxidoreductase, EC 1.1.1.1) in the larval midgut and Malpighian tubules. To analyze the regulation of the alcohol dehydrogenase genes from these two species, their homologous alcohol dehydrogenase genes were cloned and introduced, via P element-mediated transformation, into the germ line of Drosophila melanogaster. Histochemical and electrophoretic analyses of larval transformants demonstrate that major differences in the tissue-specific levels of alcohol dehydrogenase production are characteristic of the alcohol dehydrogenase genes themselves. While these results do not directly address possible species-specific differences in the tissue distribution of trans-acting regulatory components, they indicate that demonstrable differences in cis-dominant regulatory information are sufficient to account for the observed regulatory variation.

The Use of Regulatory Patterns in Constructing Phylogenies

The Hawaiian picture-winged Drosophila are a well characterized group among which there are marked differences in the pattern of expression of several developmentally regulated enzymes. We have assessed the phylogenetic information content of these pattern differences by using them in the PAUP computer program (Swofford, 1984). The resulting phylogenies were examined for internal consistency and compared to phylogenies based on other character sets. The results suggest that these patterns have changed so extensively that relationships between distantly related species have been obscured. However, the amount of homoplasy within groups of closely related species is sufficiently small that regulatory patterns may be useful for inferring relationships at this level, especially between chromosomally homo- sequential species. (Phylogeny; relationships; Drosophila; PAUP program.)

GENETICS, SPECIATION AND THE FOUNDER PRINCIPLE.

W. Anderson, K. Kaneshiro & L. V. Giddings: H. L. Carson: Interviews toward an intellectual history W. B. Provine: Founder effects and genetic revolutions in microevolution and speciation: an historical perspective G. D. Carr, R. H. Robichaux, M. S. Witter & D. W. Kyhos: Adaptive radiation of the Hawaiian silversword alliance: a comparison with Hawaiian picture-winged Drosophila F. R. Ganders: Adaptive radiation in Hawaiian bidens G. L. Stebbins: Plant speciation and the founder principle J. S. Yoon: Chromosomal evolution and speciation in Hawaiian Drosophila T. W. Lyttle: Is there a role for meiotic drive in karyotype evolution? J. A. Hunt, K. A. Houtchens, L. M. Brezinsky, F. Shadravan & J. G. Bishop: Genomic DNA variation within and between closely related species of Hawaiian Drosophila W. J. Dickinson: Gene regulation and evolution E. Nevo: The nature and role of peripheral isolates in the origin of species J. R. Powell: The effects of founder-flush cycles on ethological isolation in laboratory populations of rosophila W. B. Heed: Origin of Drosophila of the Sonoran Desert: in search for a founder event K. Y. Kaneshiro: The dynamics of sexual selection and founder effects in species formation J. V. Neel: Human evolution and the "founder-flush" principle A. T. Ohta: The genetic basis of adaptive evolution in the Grimshawi species complex of Hawaiian Drosophila A. R. Templeton: Founder effects and the evolution of reproductive isolation H. L. Carson: Genetic imbalance, realigned selection and the origin of species.

GENETICS, SPECIATION AND THE FOUNDER PRINCIPLE.

W. Anderson, K. Kaneshiro & L. V. Giddings: H. L. Carson: Interviews toward an intellectual history W. B. Provine: Founder effects and genetic revolutions in microevolution and speciation: an historical perspective G. D. Carr, R. H. Robichaux, M. S. Witter & D. W. Kyhos: Adaptive radiation of the Hawaiian silversword alliance: a comparison with Hawaiian picture-winged Drosophila F. R. Ganders: Adaptive radiation in Hawaiian bidens G. L. Stebbins: Plant speciation and the founder principle J. S. Yoon: Chromosomal evolution and speciation in Hawaiian Drosophila T. W. Lyttle: Is there a role for meiotic drive in karyotype evolution? J. A. Hunt, K. A. Houtchens, L. M. Brezinsky, F. Shadravan & J. G. Bishop: Genomic DNA variation within and between closely related species of Hawaiian Drosophila W. J. Dickinson: Gene regulation and evolution E. Nevo: The nature and role of peripheral isolates in the origin of species J. R. Powell: The effects of cycles on ethological isolation in laboratory populations of rosophila W. B. Heed: Origin of Drosophila of the Sonoran Desert: in search for a founder event K. Y. Kaneshiro: The dynamics of sexual selection and founder effects in species formation J. V. Neel: Human evolution and the founder-flush principle A. T. Ohta: The genetic basis of adaptive evolution in the Grimshawi species complex of Hawaiian Drosophila A. R. Templeton: Founder effects and the evolution of reproductive isolation H. L. Carson: Genetic imbalance, realigned selection and the origin of species.

Evolution of patterns of gene expression in Hawaiian picture-wingedDrosophila

The tissue and stage specificity of expression of five enzymes was examined by electrophoretic analysis of relative enzyme levels in extracts of 13 larval and adult tissues in 27 species of Hawaiian picture-winged Drosophila. The developmentally regulated patterns of enzyme expression thus characterized were compared to a modal standard phenotype. About 30% of the pattern features analyzed differed significantly from the standard in one or more species. Many of these regulatory differences are essentially qualitative, with tissue specific differences in enzyme activity in excess of 100 fold for some species pairs. The adaptive significance of these pattern differences in unknown, but the results provide strong direct evidence for rapid evolution of new patterns of gene regulation in this group of organisms.

Tissue specificity of enzyme expression regulated by diffusible factors: evidence in Drosophila hybrids.

Pairs of hybridizable species of Hawaiian picture-winged Drosophila differ qualitatively in the distributions of specific enzymes in their tissues. An examination of the patterns of enzyme expression in the hybrids showed that, in three instances, absence of an enzyme from a specific tissue was dominant to presence. Since other developmental features indicated that both parental genomes were functioning, these results suggest that, in these cases, the pattern differences in the parental species were due to diffusible factors that affected expression of the relevant structural genes rather than to differences in the genes themselves or in cis-acting regulatory sites.