Fern Hybrids Research Articles

Genome-wide data reveal bi-direction and asymmetrical hybridization origin of a fern species Microlepia matthewii.

Natural hybridization is common and plays a crucial role in driving biodiversity in nature. Despite its significance, the understanding of hybridization in ferns remains inadequate. Therefore, it is imperative to study fern hybridization to gain a more comprehensive understanding of fern biodiversity. Our study delves into the role of hybridization in shaping fern species, employing Microlepia matthewii as a case study to investigate its origins of hybridization. We performed double digest Genotyping-by-sequencing (dd-GBS) on M. matthewii and its potential parent species, identifying nuclear and chloroplast SNPs. Initially, nuclear SNPs were employed to construct the three cluster analysis: phylogenetic tree, principal component analysis, and population structure analysis. Subsequently, to confirm whether the observed genetic mixture pattern resulted from hybridization, we utilized two methods: ABBA-BABA statistical values in the D-suite program and gene frequency covariance in the Treemix software to detect gene flow. Finally, we employed chloroplast SNPs to construct a phylogenetic tree, tracing the maternal origin. The analysis of the nuclear SNP cluster revealed that M. matthewii possesses a genetic composition that is a combination of M. hancei and M. calvescens. Furthermore, the analysis provided strong evidence of significant gene flow signatures from the parental species to the hybrid, as indicated by the two gene flow analyses. The samples of M. matthewii cluster separately with M. hancei or M. calvescens on the chloroplast systematic tree. However, the parentage ratio significantly differs from 1:1, suggesting that M. matthewii is a bidirectional and asymmetrical hybrid offspring of M. hancei and M. calvescens.

Niche and phenotypic differentiation in fern hybrid speciation, a case study of Pteris fauriei (Pteridaceae).

Niche differentiation is a critical issue in speciation. Although it has a well-known role in adaptive processes of hybrid angiosperms, it is less understood in hybrid ferns. Here we investigate whether an intermediate ecological niche of a fern hybrid is a novel adaptation that provides insights into fern hybrid speciation. Pteris fauriei (Pteridaceae) is a natural hybrid fern, occurring environments between its parent species. The maternal P. minor is found in sunny areas, but the habitat of the paternal P. latipinna is shady. We combined data from morphology, leaf anatomy, and photosynthetic traits to explore adaptation and differentiation, along with measuring the environmental features of their niches. We also performed experiments in a common garden to understand ecological plasticity. The hybrid P. fauriei is intermediate between the parent species in stomatal density, leaf anatomical features, and photosynthetic characteristics in both natural habitats and a common garden. Interestingly, the maternal P. minor showed significant environmental plasticity and was more similar to the hybrid P. fauriei in the common garden, suggesting that the maternal species experiences stress in its natural habitats but thrives in the environments similar to the hybrid's. Based on the similar niche preferences of the hybrid and parents, we propose hybrid superiority. Our results indicate that the hybrid P. fauriei exhibits greater fitness and can compete with and occupy the initial niches of the maternal P. minor. Consequently, we suggest that the maternal P. minor has experienced a niche shift, elucidating the pattern of niche differentiation in this hybrid group. These findings offer a potential explanation for the frequent occurrence of hybridization in ferns and provide novel insights into fern hybrid speciation, enhancing our understanding of fern diversity.

<p><strong>Fern nothogenera and <em>×Lepinema, </em>a new hybrid genus between <em>Ellipinema</em> and <em>Lepisorus </em>(Polypodiaceae)</strong></p>

The biological species concept is not exclusively applicable in many groups of organisms including ferns. Interspecific fern hybrids are not rare: there are 16 intergeneric hybrid genera in ferns confirmed with molecular data. Here we add one more hybrid genus in the tribe Lepisoreae of Polypodiaceae, ×Lepinema, formed via hybridization between parents in two genera: Ellipinema and Lepisorus.

Character expression, reproductive barriers, and origin of the rare fern hybrid Asplenium ×aran-tohanum (Aspleniaceae)

Hybridization is a ubiquitous force in plant evolution. In ferns, hybrids are often easily recognized by their intermediate morphology and abortive spores and thus provide a good model for studying reproductive isolating barriers between species. Asplenium ×aran-tohanum is a rare fern hybrid, despite wide coexistence of its parental species (A. billotii and A. trichomanes subsp. quadrivalens) in Western Europe. We made a complete characterization of its three known individuals, including macro- and micromorphology, sporogenesis, gametophyte reproduction, and chloroplast DNA inheritance and evolution. The hybrid expressed morphological characters that were mostly intermediate between those of the parents, but some characters were more similar to one parent or the other. Sizes of both guard cells and spores indicate that the hybrid is tetraploid, as are both parents, and one parent (A. billotii) consistently acted as the female. A very small fraction of spores (~ 7%) were viable and the resulting gametophytes could not form sporophytes, either sexually or apogamously, suggesting that effective postzygotic barriers exist between the parents. The lineages of these taxa diverged about 35 million years ago, which may explain the strong reproductive isolation and rarity of the hybrid. Asplenium ×aran-tohanum appears to be an evolutionary dead end, probably formed recurrently at the places where it grows, but incapable of completing its life cycle or producing viable offspring.

Genetic and morphological identification of a recurrent Dicksonia tree fern hybrid in New Zealand.

Hybridization is common in many ferns and has been a significant factor in fern evolution and speciation. However, hybrids are rare between the approximately 30 species of Dicksonia tree ferns world-wide, and none are well documented. In this study we examine the relationship of a newly-discovered Dicksonia tree fern from Whirinaki, New Zealand, which does not fit the current taxonomy of the three species currently recognized in New Zealand. Our microsatellite genotyping and ddRAD-seq data indicate these plants are F1 hybrids that have formed multiple times between D. fibrosa and D. lanata subsp. lanata. The Whirinaki plants have intermediate morphology between D. fibrosa and D. lanata subsp. lanata and their malformed spores are consistent with a hybrid origin. The Whirinaki plants–Dicksonia fibrosa × D. lanata subsp. lanata–are an example of hybridization between distantly related fern lineages, with the two parent species estimated to have diverged 55–25 mya. Our chloroplast sequencing indicates asymmetric chloroplast inheritance in the Whirinaki morphology with D. lanata subsp. lanata always contributing the chloroplast genome.

Diversidad de licopodios y helechos del bosque tropical subcaducifolio del estado de Hidalgo, México

Antecedentes y Objetivos: Los estudios florísticos enfocados en helechos y licopodios en los bosques tropicales de México son escasos. Los objetivos de la presente investigación fueron conocer la riqueza de ambos grupos en el bosque tropical subcaducifolio (BTS) del estado de Hidalgo y comparar su composición y riqueza a nivel de especie con la de otras regiones del país con el mismo tipo de vegetación.Métodos: La recolección de ejemplares se realizó en 26 localidades de seis municipios con BTS en la Huasteca Hidalguense. La determinación taxonómica fue hasta nivel de especie. La semejanza taxonómica entre municipios se estimó con análisis de agrupamiento (índice de Sørensen y UPGMA), y la riqueza de especies entre regiones con un índice de diversidad taxonómica.Resultados clave: En el BTS de Hidalgo se identificaron 12 familias, 32 géneros, 66 especies y un híbrido de helechos, así como una familia, un género y seis especies de licopodios. Las familias con mayor número de géneros fueron Pteridaceae (9) y Polypodiaceae (6). Los géneros con mayor riqueza de especies fueron Anemia y Selaginella, con seis especies cada uno. Las especies de amplia distribución fueron Adiantum tenerum y Tectaria heracleifolia (constancia de 85%). Se registraron seis especies por primera vez en la entidad. La semejanza florística entre municipios fue alta, excepto Huehuetla, situado en el extremo sur del área de estudio. El BTS de Hidalgo ocupa el tercer lugar en riqueza de especies por unidad de area (6.58/ha), dentro de los bosques tropicales del país.Conclusiones: La riqueza de especies del BTS de Hidalgo es alta con respecto a la de otras regiones con el mismo tipo de vegetación en México, relevante para implementar planes de manejo y conservación, considerando el elevado grado de deterioro de este ecosistema por las actividades humanas.

Target sequence capture of nuclear-encoded genes for phylogenetic analysis in ferns.

Premise of the StudyUntil recently, most phylogenetic studies of ferns were based on chloroplast genes. Evolutionary inferences based on these data can be incomplete because the characters are from a single linkage group and are uniparentally inherited. These limitations are particularly acute in studies of hybridization, which is prevalent in ferns; fern hybrids are common and ferns are able to hybridize across highly diverged lineages, up to 60 million years since divergence in one documented case. However, it not yet clear what effect such hybridization has on fern evolution, in part due to a paucity of available biparentally inherited (nuclear‐encoded) markers.MethodsWe designed oligonucleotide baits to capture 25 targeted, low‐copy nuclear markers from a sample of 24 species spanning extant fern diversity.ResultsMost loci were successfully sequenced from most accessions. Although the baits were designed from exon (transcript) data, we successfully captured intron sequences that should be useful for more focused phylogenetic studies. We present phylogenetic analyses of the new target sequence capture data and integrate these into a previous transcript‐based data set.DiscussionWe make our bait sequences available to the community as a resource for further studies of fern phylogeny.

Genetic and genomic aspects of hybridization in ferns

AbstractThe morphological and ecological intermediacy of hybrid taxa has long interested and challenged fern biologists, resulting in numerous systematic contributions focused on disentangling relationships within reticulate species complexes. From a genetic perspective, hybrid ferns are especially interesting because they represent the union of divergent parental genomes in unique evolutionary entities. This review summarizes advances in our knowledge of the genetic and genomic aspects of hybridization in ferns from the mid‐20th century to the present. The different organismal products of hybridization, evolutionary aspects of additive and non‐additive gene expression in allopolyploids, genetic and genomic mechanisms leading to gene silencing and loss, the roles of multiple origins and introgression for imparting genetic variation to hybrid fern taxa and their progenitors, and the utility of allopolyploid ferns to investigate mechanisms of genome evolution in the homosporous ferns are discussed. Comparisons are made to other plant lineages and important future research directions are highlighted, with the goal of stimulating additional research on hybrid ferns.

用核DNA和叶绿体DNA序列鉴别铁线蕨属<italic>Adiantum</italic> L. (凤尾蕨科)新的隐性杂交种

Natural hybridization has been commonly found in ferns and is generally believed to happen independently at different locations if the range of the parent species overlaps. In 2013, we collected seven species of Adiantum from Yuanjiang, Yunnan, China. The identity of one of these collections remained in doubt; the plant is very similar to A. meishanianum ( A. malesianum × A. philippense ), a natural hybrid from Taiwan, China. Morphological comparison showed that this unidentified collection was different from other related taxa. Sequencing of a single copy of an exon ( CRY2 exon 3) of the nuclear genome suggested this plant contained haplotype sequences of both A. sinicum and A. menglianense. Therefore, it should be treated as a new hybrid. Phylogenic analysis based on five chloroplast DNA sequences ( rbc L, atp B, atp A, trn L-F and rps 4- trn S) indicated that the plant was clustered in A. sinicum, which could be considered to be the female parent of the hybrid. This new hybrid is not only similar to A. meishanianum in morphology, but also its parental taxa are in sister groups in the phylogeny. Hence, the new hybrid was considered to be a cryptic hybrid species. Our methods could be extended to identify other potential natural fern hybrids in China. The habit of clonal propagation potentially occurs in nature, so this natural hybrid could easily survive in the field because clonal growth can offset the lack of fitness caused by sexual reproductive isolation, which may be an important reason why so many hybrid ferns exist in nature.

Fern hybrid does not mind the gap

Fern hybrid does not mind the gap

Hybridization involving independent gametophytes in the Vandenboschia radicans complex (Hymenophyllaceae): a new perspective on the distribution of fern hybrids

To test our hypothesis of hybrid formation involving the 'independent gametophyte' phenomenon in ferns, we identified the genomic formulae and ploidy level of gametophytes of the Vandenboschia radicans complex at the periphery of a sporophyte population. We identified haploid gametophytes of V. kalamocarpa (one of the two putative parents of V.xstenosiphon) in a hybrid sporophyte population in Japan that lacks fertile non-hybrid individuals. Furthermore, diploid sporophytes of the species were not found within a 50-km radius. This finding supports a hypothesis of hybridization involving the 'independent gametophyte' phenomenon and provides a new perspective on the geographical distribution of fern hybrids.

Deciphering the origins of apomictic polyploids in the Cheilanthes yavapensis complex (Pteridaceae)

Deciphering species relationships and hybrid origins in polyploid agamic species complexes is notoriously difficult. In this study of cheilanthoid ferns, we demonstrate increased resolving power for clarifying the origins of polyploid lineages by integrating evidence from a diverse selection of biosystematic methods. The prevalence of polyploidy, hybridization, and apomixis in ferns suggests that these processes play a significant role in their evolution and diversification. Using a combination of systematic approaches, we investigated the origins of apomictic polyploids belonging to the Cheilanthes yavapensis complex. Spore studies allowed us to assess ploidy levels; plastid and nuclear DNA sequencing revealed evolutionary relationships and confirmed the putative progenitors (both maternal and paternal) of taxa of hybrid origin; enzyme electrophoretic evidence provided information on genome dosage in allopolyploids. We find here that the widespread apomictic triploid, Cheilanthes lindheimeri, is an autopolyploid derived from a rare, previously undetected sexual diploid. The apomictic triploid Cheilanthes wootonii is shown to be an interspecific hybrid between C. fendleri and C. lindheimeri, whereas the apomictic tetraploid C. yavapensis is comprised of two cryptic and geographically distinct lineages. We show that earlier morphology-based hypotheses of species relationships, while not altogether incorrect, only partially explain the complicated evolutionary history of these ferns.

Blechnum ×rodriguezii Hyb. Nov., a Deer Fern Hybrid from Southern Chile

ABSTRACT A new deer fern hybrid, B. corralense × B. mochaenum subsp. mochaenum, is described on the basis of macro- and micromorphological characters. Previous reports of this hybrid combination are excluded. In addition, new data on the distribution of B. corralense are reported, including its presence in Argentina.

<em>Dryopteris goldiana</em> × <em>D. intermedia</em>, a Natural Fern Hybrid New to Canada

The rare fern hybrid Dryopteris goldiana × D. intermedia is reported for the first time from Canada on the basis of a collection from eastern Ontario. The plant occurred in rich deciduous woods in an extensive seepage area at the base of a slope. The immediate vicinity had an unusually high floristic diversity and 25 associated vascular plants are listed. Distinguishing characteristics of the hybrid are outlined.

A note on the Cuban tree fern hybridCyathea ×calolepis (Cyatheaceae)and on its parentage

Caluff, M. G.: A note on the Cuban tree fern hybrid Cyathea ×calolepis (Cyatheaceae) and on its parentage. — Willdenowia 32: 311–318. 2002. — ISSN 0511-9618.Cyathea ×calolepis was first collected by Wright in 1856 or 1857 and after 1859 was not found by any other collector until 1981 when it was rediscovered on the Gran Piedra range in the Sierra Maestra. It has since been collected in several places in the Santiago de Cuba province, twice in the Granma and once in the Guantánamo province, all in E Cuba. It has long been assumed to represent the hybrid between C. arborea and another, unknown tree fern species. This assumption is here corroborated, and it is demonstrated that the second parent is the E Cuban endemic C. strigillosa.

Evidence for natural selection in a fern hybrid zone

Morphological characters, chloroplast DNA, and allozymes were used to analyze the distribution of individuals within a hybrid population of the ferns Polystichum munitum and P. imbricans in northwestern California. Microsites within the population were characterized according to soil moisture and light levels reaching the plants. In sites with low soil moisture and high light levels, all of the ferns were genetically and morphologically like P. imbricans. In contrast, ferns with the genetic and morphological identity of P. munitum predominated in moist shady sites. Intermediate sites supported very few P.munitum, a wide variety of hybrid recombinants, and a majority of ferns with P. imbricans characteristics. The pattern of variation within the population is noteworthy because of the close proximity of the habitat extremes and the long-range dispersal of fern spores. We conclude that natural selection along environmental gradients must be a major factor in determining the ecological and genetic associations within the hybrid zone. The results of this study are evaluated in the context of the fern life cycle and compared to the assumptions of models explaining the establishment and maintenance of hybrid zones, which vary in the role attributed to environmentally mediated natural selection.

Phylogeny of Aspleniaceae Inferred from rbcL Nucleotide Sequences

Phylogeny of Aspleniaceae Inferred from rbcL Nucleotide Sequences

On Hybrid Formation in the Rock Fern Asplenium x alternifolium (Aspleniaceae, Pteridophyta)

Abstract:Length polymorphism in a non‐coding spacer (trnLUAA‐trnFGAA) in the chloroplast DNA was used in the investigation of the origin of the most common and conspicuous European fern hybrid, Asplenium x alternifolium (Aspleniaceae, Pteridophyta). The origins of A. x alternifolium, the hybrid between A. trichomanes s.l. and A. septentrionale s.l. was studied at three ploidy levels, diploid, triploid and tetraploid. The cpDNA technique allowed us to investigate the mode of hybrid formation between sexual species for the first time over a wide geographic range and with a large sample size. Morphological variation in this hybrid has previously been attributed to different reciprocal parental combinations, and to the influence of chloroplast genes on morphogenesis. Our results demonstrate that one parent, A. septentrionale s.l., acts predominantly as the female parent in these hybrids, with only one population of A. x alternifolium showing reciprocal hybridity. The discovery of predominantly unidirectional hybrid formation in this hybrid may be explained by the different breeding systems of the parental taxa. The role of gametophyte ecology is also assessed.

Colysis ×beddomei (Polypodiaceae, Pteridophyta): a new interspecific fern hybrid from India, Burma and China

SummaryManickam, V. S., Irudayaraj, V. & Rajkumar, S. D.: Colysis ×beddomei (Polypodiaceae, Pteridophyta): a new interspecific fern hybrid from India, Burma and China. – Taxon 46: 265‐268. 1997. – ISSN 0040‐0262.The new fern hybrid Colysis ×beddomei Manickam & Irudayaraj (Colysis decurrens × C. hemionitidea) is described and illustrated. It was first collected in south India by Beddome, before 1883, and was then assigned to Gymnopteris variabilis. The morphological variation of the hybrid is discussed on the basis of newly collected material from the same area and of herbarium specimens from Burma and China.

Abnormal spores and possible interspecific hybridization as a factor in the evolution of Early Devonian land plants

Abnormal meiosis occurred in some land plants around 410 million years ago as witnessed by Early Devonian fossil spores from England. The spores have identical sculpture but occur in tetrad, triad, dyad and monad configurations. In that the same spore configurations occur in Ceratopteris and other modern fern hybrids the presence of similar variation in fossils may indicate the presence of hybridization amongst some Early Devonian plants. If so reticulate evolution, interspecific hybridization followed by polyploidy, may have played a significant role in the evolution of terrestrial plants in the early critical phases of their development.