Morphological and Genome-Wide Evidence of Homoploid Hybridisation in Urospermum (Asteraceae).
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ABSTRACT:
SUBMITTER: Pellicer J
PROVIDER: S-EPMC8779322 | biostudies-literature |
REPOSITORIES: biostudies-literature
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Project description:Hybridisation in the wild between closely related species is a common mechanism of speciation in the plant kingdom and, in particular, in the grass family. Here we explore the potential for natural hybridisation in Stipa (one of the largest genera in Poaceae) between genetically distant species at their distribution edges in Mountains of Central Asia using integrative taxonomy. Our research highlights the applicability of classical morphological and genome reduction approaches in studies on wild plant species. The obtained results revealed a new nothospecies, Stipa × lazkovii, which exhibits intermediate characters to S. krylovii and S. bungeana. A high-density DArTseq assay disclosed that S. × lazkovii is an F1 hybrid, and established that the plastid and mitochondrial DNA was inherited from S. bungeana. In addition, molecular markers detected a hybridisation event between morphologically and genetically distant species S. bungeana and probably S. glareosa. Moreover, our findings demonstrated an uncertainty on the taxonomic status of S. bungeana that currently belongs to the section Leiostipa, but it is genetically closer to S. breviflora from the section Barbatae. Finally, we noticed a discrepancy between the current molecular data with the previous findings on S. capillata and S. sareptana.
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Project description:BackgroundThe proper identification of feather grasses in nature is often limited due to phenotypic variability and high morphological similarity between many species. Among plausible factors influencing this issue are hybridisation and introgression recently detected in the genus. Nonetheless, to date, only a bounded set of taxa have been investigated using integrative taxonomy combining morphological and molecular data. Here, we report the first large-scale study on five feather grass species across several hybrid zones in Russia and Central Asia. In total, 302 specimens were sampled in the field and classified based on the current descriptions of these taxa. They were then genotyped with high density genome-wide markers and measured based on a set of morphological characters to delimitate species and assess levels of hybridisation and introgression. Moreover, we tested species for past introgression and estimated divergence times between them.ResultsOur findings demonstrated that 250 specimens represent five distinct species: S. baicalensis, S. capillata, S. glareosa, S. grandis and S. krylovii. The remaining 52 individuals provided evidence for extensive hybridisation between S. capillata and S. baicalensis, S. capillata and S. krylovii, S. baicalensis and S. krylovii, as well as to a lesser extent between S. grandis and S. krylovii, S. grandis and S. baicalensis. We detected past reticulation events between S. baicalensis, S. krylovii, S. grandis and inferred that diversification within species S. capillata, S. baicalensis, S. krylovii and S. grandis started ca. 130-96 kya. In addition, the assessment of genetic population structure revealed signs of contemporary gene flow between populations across species from the section Leiostipa, despite significant geographical distances between some of them. Lastly, we concluded that only 5 out of 52 hybrid taxa were properly identified solely based on morphology.ConclusionsOur results support the hypothesis that hybridisation is an important mechanism driving evolution in Stipa. As an outcome, this phenomenon complicates identification of hybrid taxa in the field using morphological characters alone. Thus, integrative taxonomy seems to be the only reliable way to properly resolve the phylogenetic issue of Stipa. Moreover, we believe that feather grasses may be a suitable genus to study hybridisation and introgression events in nature.
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Project description:Hybridization is increasingly seen as a trigger for rapid evolution and speciation. To quantify and qualify divergence associated with recent homoploid hybrid speciation, we compared quantitative trait (QT) and molecular genetic variation between the homoploid hybrid species Senecio squalidus and its parental species, S. aethnensis and S. chrysanthemifolius, and also their naturally occurring Sicilian hybrids. S. squalidus originated and became invasive in the United Kingdom following the introduction of hybrid plants from Mount Etna, Sicily, about 300 years ago. We recorded considerable molecular genetic differentiation between S. squalidus and its parents and their Sicilian hybrids in terms of both reduced genetic diversity and altered allele frequencies, potentially due to the genetic bottleneck associated with introduction to the United Kingdom. S. squalidus is also distinct from its parents and Sicilian hybrids for QTs, but less so than for molecular genetic markers. We suggest that this is due to resilience of polygenic QTs to changes in allele frequency or lack of selection for hybrid niche divergence in geographic isolation. While S. squalidus is intermediate or parental-like for most QTs, some trangressively distinct traits were observed, which might indicate emerging local adaptation in its invasive range. This study emphasizes the important contribution of founder events and geographic isolation to successful homoploid hybrid speciation.
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Project description:Petaurus breviceps and Petaurus norfolcensis have produced hybrids in captivity, however there are no reported cases of Petaurus hybridisation in the wild. This study uses morphological data, mitochondrial DNA, and nuclear genome-wide SNP markers to confirm P. breviceps breviceps × P. norfolcensis hybridisation within their natural range on the central coast of New South Wales, Australia. Morphological data identified a potential hybrid that was confirmed with next-generation sequencing technology and 10,111 genome-wide SNPs. Both STRUCTURE and NewHybrid analyses identified the hybrid as a P. norfolcensis backcross, which suggests an initial F1 hybrid was fertile. The mitochondrial DNA matched that of a P. b. breviceps, indicating that a P. b. breviceps female initially mated with a P. norfolcensis male to produce a fertile female offspring. Our study is an important example of how genome-wide SNPs can be used to identify hybrids where the distribution of congeners overlaps. Hybridisation between congeners is likely to become more frequent as climate changes and habitats fragment, resulting in increased interactions and competition for resources and mates.
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Project description:Schistosomiasis remains a public health concern across sub-Saharan Africa; current control programmes rely on accurate mapping and high mass drug administration (MDA) coverage to attempt disease elimination. Inter-species hybridisation can occur between certain species, changing epidemiological dynamics within endemic regions, which has the potential to confound control interventions. The impact of hybridisation on disease dynamics is well illustrated in areas of Cameroon where urogenital schistosomiasis, primarily due to Schistosoma haematobium and hybrid infections, now predominate over intestinal schistosomiasis caused by Schistosoma guineensis. Genetic markers have shown the ability to identify hybrids, however the underlying genomic architecture of divergence and introgression between these species has yet to be established. In this study, restriction site associated DNA sequencing (RADseq) was used on archived adult worms initially identified as; Schistosoma bovis (n = 4), S. haematobium (n = 9), S. guineensis (n = 3) and S. guineensis x S. haematobium hybrids (n = 4) from Mali, Senegal, Niger, São Tomé and Cameroon. Genome-wide evidence supports the existence of S. guineensis and S. haematobium hybrid populations across Cameroon. The hybridisation of S. guineensis x S. haematobium has not been demonstrated on the island of São Tomé, where all samples showed no introgression with S. haematobium. Additionally, all S. haematobium isolates from Nigeria, Mali and Cameroon indicated signatures of genomic introgression from S. bovis. Adaptive loci across the S. haematobium group showed that voltage-gated calcium ion channels (Cav) could play a key role in the ability to increase the survivability of species, particularly in host systems. Where admixture has occurred between S. guineensis and S. haematobium, the excess introgressive influx of tegumental (outer helminth body) and antigenic genes from S. haematobium has increased the adaptive response in hybrids, leading to increased hybrid population fitness and viability.
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Project description:Genomes of numerous diploid plant and animal species possess traces of interspecific crosses, and many researches consider them as support for homoploid hybrid speciation (HHS), a process by which a new reproductively isolated species arises through hybridization and combination of parts of the parental genomes, but without an increase in ploidy. However, convincing evidence for a creative role of hybridization in the origin of reproductive isolation between hybrid and parental forms is extremely limited. Here, through studying Agrodiaetus butterflies, we provide proof of a previously unknown mode of HHS based on the formation of post-zygotic reproductive isolation via hybridization of chromosomally divergent parental species and subsequent fixation of a novel combination of chromosome fusions/fissions in hybrid descendants. We show that meiotic segregation, operating in the hybrid lineage, resulted in the formation of a new diploid genome, drastically rearranged in terms of chromosome number. We also demonstrate that during the heterozygous stage of the hybrid species formation, recombination was limited between rearranged chromosomes of different parental origin, representing evidence that the reproductive isolation was a direct consequence of hybridization.
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