Speciation by hybridization in phasmids and other insects

Speciation by hybridization in insects has been recently recognized on the basis of isozyme and chromosome studies showing that several species, either diploid or polyploid, have genomes that combine the genes and chromosome sets of two (or more) bisexual species. Until this evidence became available, thelytokous invertebrates were all considered uniparental derivatives of bisexual species. In this paper, we review examples including the stick insects Bacillus whitei, B. atticus, B. lynceorum, Leptynia hispanica D, Clonopsis gallica, Carausius morosus; the grasshopper Warramaba virgo; some Otiorrhynchus weevils; the planthopper Muellerianella 2-fairmairei–brevipennis; and black flies of the genera Gymnopais and Prosimulium. For several species (e.g., Warramaba virgo and Bacillus whitei), both parental taxa have been recognized, and their hybrid origin has been genetically assessed. In others (e.g., B. atticus), only one of the bisexual parental species has been detected; but their hybrid origin is supported by strong evidence, at both the isozyme and chromosome levels. For other supposed hybrid species (e.g., Clonopsis gallica, Carausius morosus), no bisexual ancestors have been detected, possibly because competition with their hybrid derivatives has made them rare or extinct. Insect hybrid species may differ in their mode of reproduction (apomictic or automictic thelytokous parthenogenesis, gynogenesis), degree of ploidy, and genetic structure (level of heterozygosity, clonal variation). The parallels between insect and vertebrate hybrid species, in which this phenomenon has been recognized and widely studied in the past 50 years, are drawn. The main problems involved in the origin and evolution of hybrid species are discussed, with particular regard to (i) changes in the maturation divisions allowing the transmission of the hybrid genome to the next generation, and (ii) their successful adaptation. The "spontaneous" and "hybrid" theories for the origin of unisexual forms are compared, with regard to hybrid species. An origin of hybrid species from occasional parthenogenetic development of hybrid eggs produced in areas of extensive interspecific hybridization (e.g., disturbed habitats) is suggested. Hybridization would not itself cause changes in the maturation divisions (which are controlled by genes of tychoparthenogenetic eggs) but only favour their selection through heterosis. The role of the so-called "heterotic" advantage (resulting from high levels of heterozygosity) and "demographic" advantage (resulting from all-female reproduction) in the evolutionary success of hybrid species is discussed. It is concluded that habitat disturbance by man is favouring both the onset of hybrid species and their successful spread.

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Hybrid Origin and Genomic Mosaicism of Dubautia scabra (Hawaiian Silversword Alliance; Asteraceae, Madiinae)

Systematic Botany ◽

10.1600/036364408785679815 ◽

2008 ◽

Vol 33 (3) ◽

pp. 589-597 ◽

Cited By ~ 16

Author(s):

Elizabeth A. Friar ◽

Linda M. Prince ◽

Jennifer M. Cruse-Sanders ◽

Mitchell E. McGlaughlin ◽

Charles A. Butterworth ◽

...

Keyword(s):

Single Copy ◽

Nuclear Genes ◽

Hybrid Origin ◽

Internal Transcribed Spacer Region ◽

Hybrid Species ◽

Cytogenetic Data ◽

Molecular Phylogenetic ◽

Distinct Lineage ◽

Phylogenetic Hypotheses ◽

Genomic Regions

Incongruence among different estimates of species relationships in plants, from different molecules, cytogenetic data, biogeographic data, morphological/anatomical data or other sources, has been used frequently as an indication of introgression, hybrid species origin, or chloroplast (cp) capture. In plants, these incongruences are most often seen between data derived from the nuclear vs. the cp genomes and the nuclear markers used for comparison usually have been from the nuclear ribosomal (nr) internal transcribed spacer region (ITS). The amount of genomic material shared between introgressing species can be highly variable. In some of these cases, other nuclear genomic regions have moved between species without leaving a signature on the nrITS. An example of well-supported phylogenetic incongruence is the placement of Dubautia scabra (DC.) D. D. Keck in the Hawaiian silversword alliance (HSA); evolutionary hypotheses for D. scabra based on molecular as opposed to cytogenetic data are strongly discordant. In this paper, we test these two conflicting phylogenetic hypotheses regarding the evolutionary relationships of Dubautia scabra using evidence from six low-copy nuclear genes, as well as multiple chloroplast noncoding regions and nrITS. The nrITS region is also examined for the presence of multiple copy types. Incongruence between inferred relationships based on nuclear chromosomal arrangements and molecular phylogenetic data from chloroplast DNA and nrITS is resolved in favor of a hypothesis of ancient hybridization rather than cytogenetic homoplasy involving dysploidy. Most single-copy nuclear genes track histories of D. scabra compatible with cytogenetic data whereas chloroplast and nrITS data track a common, different history that appears to reflect hybridization with a chromosomally distinct lineage that also occurs on Maui Nui and Hawai'i (the Big Island).

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Evidence for continual hybridization rather than hybrid speciation betweenLigularia duciformisandL. paradoxa(Asteraceae)

PeerJ ◽

10.7717/peerj.3884 ◽

2017 ◽

Vol 5 ◽

pp. e3884 ◽

Cited By ~ 5

Author(s):

Rong Zhang ◽

Xun Gong ◽

Ryan Folk

Keyword(s):

Parental Species ◽

Reproductive Traits ◽

Issr Markers ◽

Natural Hybridization ◽

Hybrid Origin ◽

Phenotypic Traits ◽

Hybrid Species ◽

Network Analyses ◽

Hybrid Swarms ◽

Ssr Loci

BackgroundHybrids possess phenotypic traits that are often intermediate between their parental taxa, which commonly serves as evidence of hybridization in morphological analyses. Natural hybridization has been shown to occur frequently inLigularia(Asteraceae). In a previous study,Ligularia×maoniushanensiswas demonstrated as a natural hybrid species betweenL. duciformisandL.paradoxabased on morphological and reproductive traits.MethodsWe used three chloroplast (cpDNA) fragments (psbA-trnH,trnL-rpl32 andtrnQ-5′rps16), the nuclear ribosomal internal transcribed spacer (nrITS), and co-dominant SSR and dominant ISSR markers to study natural hybridization betweenL. duciformisandL. paradoxagrowing sympatrically in two locations. Parental taxa were inferred using network analyses of cpDNA and nrITS haplotypes. Admixture among individuals was examined using the Bayesian clustering programs STRUCTURE and NewHybrids based on the SSR and ISSR data; and potential introgression in the SSR loci was assessed using the INTROGRESS package.ResultsThe putative parental species were clearly distinguished from other sympatricLigulariaspecies by nrITS data, andL.×maoniushanensisindividuals were confirmed to be the hybrid offspring ofL.duciformisandL.paradoxa. Moreover, introgression was detected among several individuals morphologically identified asL.duciformisorL. paradoxa. Analyses of the cpDNA data revealed primarily unidirectional hybridization betweenL. duciformisandL. paradoxa, withL.paradoxaas the maternal parent in Mt. Maoniu, whereas bidirectional but asymmetrical hybridization was inferred to occur in Heihai Lake. The STRUCTURE analyses based on the SSR data detected two distinct clusters among the three taxa. The NewHybrids analyses showed that individuals circumscribed asL.×maoniushanensiswere dominated by early- and later-generation and backcrossing hybrids. The NewHybrids results based on the ISSR data were congruent with SSR results. In addition, introgression was detected in some SSR loci, and heterogeneity among loci was found in terms of detected patterns of introgression.ConclusionsOur data provide strong evidence for hybridization and introgression betweenL.duciformisandL.paradoxa.Ligularia×maoniushanensiswas demonstrated to be of hybrid origin. Since no evident reproductive isolation was found between the two parental species, detected hybrids appear to be part of hybrid swarms resulting from frequent and ongoing gene flow, which might impede the formation of a new hybrid species.

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Natural hybridization between two butterfly bushes in Tibet: dominance of F1 hybrids promotes strong reproductive isolation

10.21203/rs.3.rs-42245/v3 ◽

2021 ◽

Author(s):

Rongli Liao ◽

Weibang Sun ◽

Yongpeng Ma

Keyword(s):

Morphological Characters ◽

Natural Hybridization ◽

Hybrid Origin ◽

F1 Hybrids ◽

Sympatric Populations ◽

Intergenic Spacers ◽

Typical Distribution ◽

Hybridization Origin ◽

Butterfly Bush ◽

Disturbed Habitats

Abstract Background: It has been recognized that certain amount of habitat disturbance is a prerequisite for occurrence of natural hybridization, yet we are currently still not aware of any studies exploring hybridization and reproductive barriers to those plants preferably occupying disturbed habitats. Buddleja plants (also called butterfly bush) generally grow in disturbed habitat, and several species with hybrid origin only on basis of morphology evidence have been proposed. Results: In the present study, we test the natural hybridization origin hypothesis of B. × wardii in two sympatric populations of three taxa including B. × wardii and its parents (B. alternifolia and B. crispa) plus 4 referenced parental populations, using four nuclear genes and three chloroplast intergenic spacers, as well as with 10 morphological characters. Our results suggest that at both sites B. × wardii was likely to be hybrids between B. alternifolia and B. crispa, and moreover, most of the hybrids examined were confirmed to be F1s. This was further supported by morphology as no transgressive characters were detected. B. crispa was found to be the maternal parent in Bahe (BH) population from the cpDNA. While in the Taji (TJ) population was difficult to distinguish the hybridization direction due to the shared haplotypes of cpDNA between B. alternifolia and B. crispa, we still predicted the similar unidirectional hybridization pattern due to results from cross-specific pollination treatments which supported the “SI x SC rule”. Conclusions: Hybrids mainly consisting of F1s can successfully impede gene flow and thus maintain species boundaries of parental species in its typical distribution of Buddleja, i.e. disturbed habitats.

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Recent hybrid speciation at the origin of the narrow endemic Pulmonaria helvetica

Annals of Botany ◽

10.1093/aob/mcaa145 ◽

2020 ◽

Vol 127 (1) ◽

pp. 21-31 ◽

Cited By ~ 1

Author(s):

Sandra Grünig ◽

Markus Fischer ◽

Christian Parisod

Keyword(s):

Niche Differentiation ◽

Ecological Modelling ◽

Hybrid Origin ◽

Hybrid Speciation ◽

Niche Modelling ◽

Hybrid Species ◽

Intrinsic Factors ◽

Narrow Endemic ◽

Genetic Clusters ◽

Original Number

Abstract Background and Aims Hybridization is known to drive plant speciation through the establishment of homoploid or allopolyploid hybrid species. Here we investigate the origin of Pulmonaria helvetica, a narrow endemic species described across a restricted area of Switzerland that was entirely covered by ice during the last glacial maximum. This species presents an original number of chromosomes (2n = 24) and morphological traits suggestive of a hybrid origin. Methods We sequenced a plastid locus and 1077 double-digest restriction-site-associated DNA (ddRAD) loci in 67 individuals from across the distribution range of P. helvetica and candidate progenitor species growing in the same area. Assignment of genotypes to main genetic clusters within and among taxa using STRUCTURE tested whether P. helvetica represents a genetically differentiated lineage and addressed the hypothesis of its hybrid origin. Comparative ecological modelling further addressed possible niche differentiation among taxa. Key Results Pulmonaria helvetica was highlighted as a genetically homogeneous species distinct from co-occurring taxa. Consistent with a scenario of hybrid speciation, it presented clear evidence of balanced admixture between Pulmonaria officinalis (2n = 16) and Pulmonaria mollis s.l. (2n = 18, 22), which was also highlighted as a maternal progenitor based on plastid sequences. Limited genetic structure within the maternal progenitor is consistent with an origin of P. helvetica through either homoploid hybridization with considerable karyotype changes or via complex scenarios of allopolyploidy involving a dysploid taxon of P. mollis s.l. Comparative niche modelling indicated non-significant ecological differences between P. helvetica and its progenitors, supporting intrinsic factors resulting from hybridization as main drivers of speciation. Conclusions Hybridization appears as a major process having promoted the postglacial origin of the narrow endemic P. helvetica, suggesting hybrid speciation as an effective process that rapidly produces new species under climate changes.

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Genomic Screening Reveals That the Endangered Eucalyptus paludicola (Myrtaceae) Is a Hybrid

Diversity ◽

10.3390/d12120468 ◽

2020 ◽

Vol 12 (12) ◽

pp. 468

Author(s):

Kor-jent van Dijk ◽

Michelle Waycott ◽

Joe Quarmby ◽

Doug Bickerton ◽

Andrew H. Thornhill ◽

...

Keyword(s):

High Throughput Sequencing ◽

South Australia ◽

Hybrid Origin ◽

F1 Hybrids ◽

Management Options ◽

Hybrid Species ◽

Conservation Implications ◽

Hybrid Class ◽

Low Incidence ◽

Stable Hybrid

A hybrid origin for a conservation listed taxon will influence its status and management options. Here, we investigate the genetic origins of a nationally endangered listed taxon—Eucalyptus paludicola—a tree that is restricted to the Fleurieu Peninsula and Kangaroo Island of South Australia. Since its description in 1995, there have been suggestions that this taxon may potentially be a stable hybrid species. Using a high throughput sequencing approach, we developed a panel of polymorphic loci that were screened across E. paludicola and its putative parental species E. cosmophylla and E. ovata. Bayesian clustering of the genotype data identified separate groups comprising E. ovata and E. cosmophylla while E. paludicola individuals were admixed between these two, consistent with a hybrid origin. Hybrid class assignment tests indicate that the majority of E. paludicola individuals (~70%) are F1 hybrids with a low incidence of backcrossing. Most of the post-F1 hybrids were associated with revegetation sites suggesting they may be maladapted and rarely reach maturity under natural conditions. These data support the hypothesis that E. paludicola is a transient hybrid entity rather than a distinct hybrid species. We briefly discuss the conservation implications of our findings.

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Leaf anatomy is not correlated to CAM function in a C3+CAM hybrid species, Yucca gloriosa

Annals of Botany ◽

10.1093/aob/mcaa036 ◽

2020 ◽

Cited By ~ 3

Author(s):

Karolina Heyduk ◽

Jeremy N Ray ◽

Jim Leebens-Mack

Keyword(s):

Leaf Anatomy ◽

Time Course ◽

Intraspecific Variability ◽

Complex Trait ◽

Hybrid Origin ◽

Cam Plants ◽

Hybrid Species ◽

Anatomy And Physiology ◽

Cam Species ◽

Trait Correlations

Abstract Background and Aims Crassulacean acid metabolism (CAM) is often considered to be a complex trait, requiring orchestration of leaf anatomy and physiology for optimal performance. However, the observation of trait correlations is based largely on comparisons between C3 and strong CAM species, resulting in a lack of understanding as to how such traits evolve and the level of intraspecific variability for CAM and associated traits. Methods To understand intraspecific variation for traits underlying CAM and how these traits might assemble over evolutionary time, we conducted detailed time course physiological screens and measured aspects of leaf anatomy in 24 genotypes of a C3+CAM hybrid species, Yucca gloriosa (Asparagaceae). Comparisons were made to Y. gloriosa’s progenitor species, Y. filamentosa (C3) and Y. aloifolia (CAM). Key Results Based on gas exchange and measurement of leaf acids, Y. gloriosa appears to use both C3 and CAM, and varies across genotypes in the degree to which CAM can be upregulated under drought stress. While correlations between leaf anatomy and physiology exist when testing across all three Yucca species, such correlations break down at the species level in Y. gloriosa. Conclusions The variation in CAM upregulation in Y. gloriosa is a result of its relatively recent hybrid origin. The lack of trait correlations between anatomy and physiology within Y. gloriosa indicate that the evolution of CAM, at least initially, can proceed through a wide combination of anatomical traits, and more favourable combinations are eventually selected for in strong CAM plants.

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Clonal Structure of Some Weevil Species (Coleoptera, Curculionidae) From Central Ukraine

Vestnik Zoologii ◽

10.2478/vzoo-2018-0033 ◽

2018 ◽

Vol 52 (4) ◽

pp. 313-322

Author(s):

V. Yu. Nazarenko ◽

S. Yu. Morozov-Leonov

Keyword(s):

Clonal Diversity ◽

Hybrid Origin ◽

Clonal Variation ◽

Clonal Structure ◽

Weevil Species ◽

Electrophoretic Spectra

Abstract The clonal structure of the populations of nine weevil species (family Curculionidae) from central Ukraine was analyzed. Clonal diversity varied extensively among studied species. Th e level of clonal variation of some species (Otiorhynchus ligustici, O. raucus, Liophloeus tessulatus) is high, within some other species (O. tristis, Tropiphorus micans) it is low. Th e constant heterozygosity of lot of genes has been demonstrated that it may be a proof of the hybrid origin of the studied weevil populations. Th e asymmetry of some obtained electrophoretic spectra was observed. Th is can be a consequence of their polyploid nature. Th e signifi cant interpopulation diff erentiation of most of the species studied was demonstrated.

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Origin, elevation, and evolutionary success of hybrids and polyploids in British Columbia, Canada

Botany ◽

10.1139/cjb-2012-0177 ◽

2013 ◽

Vol 91 (3) ◽

pp. 182-188 ◽

Cited By ~ 9

Author(s):

Jana C. Vamosi ◽

Jamie R. McEwen

Keyword(s):

British Columbia ◽

Evolutionary History ◽

Elevation Gradient ◽

Hybrid Origin ◽

Diploid Hybrid ◽

Hybrid Species ◽

Ecological Patterns ◽

Evolutionary Success ◽

Richness Patterns ◽

High Elevations

Although it is well established that many clades have polyploidization in their evolutionary history, the question of whether polyploidization is actually adaptive is far from resolved. It has been hypothesized that the evolutionary advantages of polyploidy are context-dependent, although we have yet to clearly identify the geographical or ecological contexts in which polyploids are more common. One reason why polyploidy may be displaying idiosyncratic ecological patterns is that previous comparative studies have often not separated polyploids into allopolyploids and autopolyploids, and we posit that there may be important differences in the origin and evolutionary success between the two types. Here, we examine the distribution of allopolyploid, autopolyploid, and diploid hybrid species along an elevation gradient from sea level to ∼4500 m within British Columbia, Canada, and find that polyploids (especially those of hybrid origin) are disproportionately present at high elevations. These processes of hybridization and polyploidization may contribute to species richness patterns observed in British Columbia. We discuss whether the associations are more likely to be the result of differential ecological tolerance or differential origination rates of allopolyploids at higher elevations. These findings highlight the importance of studying both hybridization and polyploidy when considering the diversification process in plants.

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Natural hybridization between two butterfly bushes in Tibet: dominance of F1 hybrids promotes strong reproductive isolation

BMC Plant Biology ◽

10.1186/s12870-021-02909-7 ◽

2021 ◽

Vol 21 (1) ◽

Author(s):

Rongli Liao ◽

Weibang Sun ◽

Yongpeng Ma

Keyword(s):

Morphological Characters ◽

Natural Hybridization ◽

Hybrid Origin ◽

F1 Hybrids ◽

Morphological Evidence ◽

Sympatric Populations ◽

Intergenic Spacers ◽

Hybridization Origin ◽

Butterfly Bush ◽

Disturbed Habitats

AbstractBackgroundIt has been recognized that a certain amount of habitat disturbance is a facilitating factor for the occurrence of natural hybridization, yet to date we are unaware of any studies exploring hybridization and reproductive barriers in those plants preferentially occupying disturbed habitats.Buddlejaplants (also called butterfly bush) generally do grow in disturbed habitats, and several species with hybrid origin have been proposed, based solely on morphological evidence.ResultsIn the present study, we test the hypothesis thatB. × wardiiis of natural hybridization origin in two sympatric populations of three taxa includingB. × wardiiand its parents (B. alternifoliaandB. crispa) plus 4 referenced parental populations, using four nuclear genes and three chloroplast intergenic spacers, as well as with 10 morphological characters. Our results suggest that at both sitesB. × wardiiis likely to be a hybrid betweenB. alternifoliaandB. crispa, and moreover, we confirm that most of the hybrids examined are F1s. That these plants are F1s is further supported by morphology, as no transgressive characters were detected.B. crispawas found to be the maternal parent in the Bahe (BH) population, from cpDNA evidence. However, in the Taji (TJ) population, the direction of hybridization was difficult to establish due to the shared cpDNA haplotypes betweenB. alternifoliaandB. crispa, however we still predicted a similar unidirectional hybridization pattern due to results from cross-specific pollination treatments which supported the “SI × SC rule”.ConclusionsThe presence of mainly F1hybrids can successfully impede gene flow and thus maintain species boundaries in parental species in a typical distribution ofBuddleja, i.e. in disturbed habitats.

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Origin and evolution of Parthenogenetic reproduction in the grasshopper Maraba virgo (Eumastacidae: Morabinae)

Australian Journal of Zoology ◽

10.1071/zo9680647 ◽

1968 ◽

Vol 16 (4) ◽

pp. 647 ◽

Cited By ~ 21

Author(s):

MJD White ◽

GC Webb

Keyword(s):

New South ◽

Tritiated Thymidine ◽

Chromosomal Rearrangements ◽

Bisexual Species ◽

Origin And Evolution ◽

South Wales ◽

Parthenogenetic Reproduction ◽

Western Victoria ◽

Thymidine Autoradiography ◽

North Western

The virgo group of morabine grasshoppers includes the parthenogenetic, all. female species virgo from western New South Wales and north-western Victoria, together with four bisexual species from arid regions of Western Australia. The karyotypes of three of these bisexual species are compared with that of virgo and the origin of the various kinds of genetic heterozygosity found in the latter is discussed. It has been shown by tritiated thymidine autoradiography that virgo, in addition to being heterozygous for various structural rearrangements, is a permanent heterozygote for certain late-replicating DNA segments in the AB and CD chromosomes. The total amount of DNA per diploid nucleus is slightly lower in virgo than in its bisexual relatives. It is probable that the evolution of the virgo karyotype under conditions of parthenogenetic reproduction has involved inactivation of some segments (as suggested by late-labelling) and actual deletion of others. There have been two different X-autosome fusions in the phylogeny of the virgo group (one in the ancestry of virgo itself), two fusions between autosomes, and a translocation (or dissociation plus fusion). A numerical system to designate these and other chromosomal rearrangements in the morabine grasshoppers is put forward.

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