Extensive hybridization between two Andean warbler species with shallow divergence in mtDNA

Abstract Studying processes acting on differentiated populations upon secondary contact, such as hybridization, is important to comprehensively understand how species are formed and maintained over time. However, avian speciation studies in the tropical Andes have largely focused on the role of topographic and ecological barriers promoting divergence in allopatry, seldom examining hybridization and introgression. We describe a hybrid zone involving 2 closely related Andean warblers (Parulidae), the Golden-fronted Redstart (Myioborus ornatus), and the Spectacled Redstart (Myioborus melanocephalus). Geographic ranges of these species abut near the Colombia-Ecuador border and many specimens from the region exhibit intermediate phenotypes, but a formal description of phenotypic variation in the contact zone was heretofore lacking. We collected specimens across a transect encompassing the area where ranges abut and areas where only “pure” parental phenotypes of M. ornatus chrysops and M. melanocephalus ruficoronatus occur. We described variation in plumage traits including patterns of head and ventral coloration and tail markings based on 321 specimens. To describe genetic variation in the contact zone and over a broader phylogeographic context, we used sequences of the mitochondrial ND2 gene for 219 individuals across the transect and the entire range of both species, including all subspecies, from Venezuela to Bolivia. We documented a hybrid zone ~200 km wide based on head coloration, where intermediate plumage phenotypes are most common and “pure” forms do not overlap geographically, consistent with extensive hybridization. Across the range of the M. ornatus–M. melanocephalus complex, mitochondrial genetic structure was shallow, with genetic breaks only coinciding clearly with one topographic feature. Such a low genetic structure is striking given the high diversity in plumage phenotypes and the current taxonomy of the group. Our phenotypic data suggest that barriers to hybridization are not strong, and allow us to postulate hypotheses to be tested using forthcoming genomic data.

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How often do they do it? An in-depth analysis of the hybrid zone of two grass snake species (Natrix astreptophora and Natrix helvetica)

Biological Journal of the Linnean Society ◽

10.1093/biolinnean/blaa152 ◽

2020 ◽

Vol 131 (4) ◽

pp. 756-773

Author(s):

Marika Asztalos ◽

Nadine Schultze ◽

Flora Ihlow ◽

Philippe Geniez ◽

Matthieu Berroneau ◽

...

Keyword(s):

Contact Zone ◽

Hybrid Zone ◽

Climatic Conditions ◽

Secondary Contact ◽

Distribution Models ◽

Long Distance ◽

Depth Analysis ◽

Grass Snake ◽

Genetic Signatures ◽

Cline Width

Abstract We examined the contact zone of two parapatric species of grass snake (Natrix astreptophora and Natrix helvetica) in southern France. To this end, we used comprehensive sampling, analysed mtDNA sequences and microsatellite loci, and built Species Distribution Models for current and past climatic conditions. The contact zone had established by the mid-Holocene during range expansions from glacial refuges in the Iberian Peninsula (N. astreptophora) and southern or western France (N. helvetica). The contact zone represents a narrow bimodal hybrid zone, with steep genetic transition from one taxon to the other and rare hybridization, supporting species status for N. astreptophora and N. helvetica. Our results suggest that the steepness of the clines is a more robust tool for species delimitation than cline width. In addition, we discovered in western France, beyond the hybrid zone, a remote population of N. helvetica with genetic signatures of hybridization with N. astreptophora, most likely the result of human-mediated long-distance dispersal. For N. helvetica, we identified a southern and a northern population cluster, connected by broad-scale gene flow in a unimodal hybrid zone running across France. This pattern either reflects genetic divergence caused by allopatry in two microrefuges and subsequent secondary contact or introgression of foreign alleles into the southern cluster.

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Microbiota, Immune System and Autism Spectrum Disorders: An Integrative Model towards Novel Treatment Options

Current Medicinal Chemistry ◽

10.2174/0929867326666190328151539 ◽

2020 ◽

Vol 27 (31) ◽

pp. 5119-5136 ◽

Cited By ~ 5

Author(s):

Barbara Carpita ◽

Donatella Marazziti ◽

Lionella Palego ◽

Gino Giannaccini ◽

Laura Betti ◽

...

Keyword(s):

Immune System ◽

Familial Aggregation ◽

Treatment Options ◽

Autism Spectrum ◽

Integrative Model ◽

Neural Basis ◽

Integrative Framework ◽

Intermediate Phenotypes ◽

Close Relatives

Background: Autism Spectrum Disorder (ASD) is a condition strongly associated with genetic predisposition and familial aggregation. Among ASD patients, different levels of symptoms severity are detectable, while the presence of intermediate autism phenotypes in close relatives of ASD probands is also known in literature. Recently, increasing attention has been paid to environmental factors that might play a role in modulating the relationship between genomic risk and development and severity of ASD. Within this framework, an increasing body of evidence has stressed a possible role of both gut microbiota and inflammation in the pathophysiology of neurodevelopment. The aim of this paper is to review findings about the link between microbiota dysbiosis, inflammation and ASD. Methods: Articles ranging from 1990 to 2018 were identified on PUBMED and Google Scholar databases, with keyword combinations as: microbiota, immune system, inflammation, ASD, autism, broad autism phenotype, adult. Results: Recent evidence suggests that microbiota alterations, immune system and neurodevelopment may be deeply intertwined, shaping each other during early life. However, results from both animal models and human samples are still heterogeneous, while few studies focused on adult patients and ASD intermediate phenotypes. Conclusion: A better understanding of these pathways, within an integrative framework between central and peripheral systems, might not only shed more light on neural basis of ASD symptoms, clarifying brain pathophysiology, but it may also allow to develop new therapeutic strategies for these disorders, still poorly responsive to available treatments.

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A Developmental Perspective on the Genetic Basis of Alcohol Use Disorder

10.1093/oso/9780190676001.003.0004 ◽

2018 ◽

Author(s):

Elisa M. Trucco ◽

Gabriel L. Schlomer ◽

Brian M. Hicks

Keyword(s):

Alcohol Use ◽

Alcohol Use Disorder ◽

Developmental Perspective ◽

Relative Contribution ◽

Intermediate Phenotypes ◽

Problematic Alcohol ◽

Age Related ◽

Genetic And Environmental Factors ◽

Problematic Alcohol Use

Approximately 48–66% of the variation in alcohol use disorders is heritable. This chapter provides an overview of the genetic influences that contribute to alcohol use disorder within a developmental perspective. Namely, risk for problematic alcohol use is framed as a function of age-related changes in the relative contribution of genetic and environmental factors and an end state of developmental processes. This chapter discusses the role of development in the association between genes and the environment on risk for alcohol use disorder. Designs used to identify genetic factors relevant to problematic alcohol use are discussed. Studies examining developmental pathways to alcohol use disorder with a focus on endophenotypes and intermediate phenotypes are reviewed. Finally, areas for further investigation are offered.

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Four Mutant Alleles Elucidate the Role of the G2 Protein in the Development of C4 and C3 Photosynthesizing Maize Tissues

Genetics ◽

10.1093/genetics/159.2.787 ◽

2001 ◽

Vol 159 (2) ◽

pp. 787-797

Author(s):

Lizzie Cribb ◽

Lisa N Hall ◽

Jane A Langdale

Keyword(s):

Cell Types ◽

Bundle Sheath ◽

Primary Role ◽

Ribulose Bisphosphate Carboxylase ◽

Sheath Cell ◽

Mesophyll Cells ◽

Phenotypic Data ◽

Bisphosphate Carboxylase ◽

Bundle Sheath Cell

Abstract Maize leaf blades differentiate dimorphic photosynthetic cell types, the bundle sheath and mesophyll, between which the reactions of C4 photosynthesis are partitioned. Leaf-like organs of maize such as husk leaves, however, develop a C3 pattern of differentiation whereby ribulose bisphosphate carboxylase (RuBPCase) accumulates in all photosynthetic cell types. The Golden2 (G2) gene has previously been shown to play a role in bundle sheath cell differentiation in C4 leaf blades and to play a less well-defined role in C3 maize tissues. To further analyze G2 gene function in maize, four g2 mutations have been characterized. Three of these mutations were induced by the transposable element Spm. In g2-bsd1-m1 and g2-bsd1-s1, the element is inserted in the second intron and in g2-pg14 the element is inserted in the promoter. In the fourth case, g2-R, four amino acid changes and premature polyadenylation of the G2 transcript are observed. The phenotypes conditioned by these four mutations demonstrate that the primary role of G2 in C4 leaf blades is to promote bundle sheath cell chloroplast development. C4 photosynthetic enzymes can accumulate in both bundle sheath and mesophyll cells in the absence of G2. In C3 tissue, however, G2 influences both chloroplast differentiation and photosynthetic enzyme accumulation patterns. On the basis of the phenotypic data obtained, a model that postulates how G2 acts to facilitate C4 and C3 patterns of tissue development is proposed.

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Landscape resistance constrains hybridization across contact zones in a reproductively and morphologically polymorphic salamander

Scientific Reports ◽

10.1038/s41598-021-88349-7 ◽

2021 ◽

Vol 11 (1) ◽

Author(s):

Guillermo Velo-Antón ◽

André Lourenço ◽

Pedro Galán ◽

Alfredo Nicieza ◽

Pedro Tarroso

Keyword(s):

Contact Zone ◽

Environmental Heterogeneity ◽

Evolutionary Dynamics ◽

Morphological Differentiation ◽

Phenotypic Traits ◽

Hybrid Zones ◽

Landscape Resistance ◽

Phenotypic Differentiation ◽

Contact Zones

AbstractExplicitly accounting for phenotypic differentiation together with environmental heterogeneity is crucial to understand the evolutionary dynamics in hybrid zones. Species showing intra-specific variation in phenotypic traits that meet across environmentally heterogeneous regions constitute excellent natural settings to study the role of phenotypic differentiation and environmental factors in shaping the spatial extent and patterns of admixture in hybrid zones. We studied three environmentally distinct contact zones where morphologically and reproductively divergent subspecies of Salamandra salamandra co-occur: the pueriparous S. s. bernardezi that is mostly parapatric to its three larviparous subspecies neighbours. We used a landscape genetics framework to: (i) characterise the spatial location and extent of each contact zone; (ii) assess patterns of introgression and hybridization between subspecies pairs; and (iii) examine the role of environmental heterogeneity in the evolutionary dynamics of hybrid zones. We found high levels of introgression between parity modes, and between distinct phenotypes, thus demonstrating the evolution to pueriparity alone or morphological differentiation do not lead to reproductive isolation between these highly divergent S. salamandra morphotypes. However, we detected substantial variation in patterns of hybridization across contact zones, being lower in the contact zone located on a topographically complex area. We highlight the importance of accounting for spatial environmental heterogeneity when studying evolutionary dynamics of hybrid zones.

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Deep genetic structure at a small spatial scale in the endangered land snail Xerocrassa montserratensis

Scientific Reports ◽

10.1038/s41598-021-87741-7 ◽

2021 ◽

Vol 11 (1) ◽

Author(s):

Cristina Català ◽

Vicenç Bros ◽

Xavier Castelltort ◽

Xavier Santos ◽

Marta Pascual

Keyword(s):

Genetic Structure ◽

Land Snail ◽

Snail Species ◽

Small Spatial Scale ◽

Geographic Ranges ◽

Genetic Groups ◽

Species Of Conservation Concern ◽

Conservation Actions ◽

Conservation Concern ◽

Single Locality

AbstractSpecies with small geographic ranges do not tend to have a high genetic structure, but some land snail species seem to be an exception. Xerocrassa montserratensis, an endangered land snail endemic to Catalonia (northeastern Iberian Peninsula), is an excellent model to study the processes affecting the phylogeography of specialized species of conservation concern. This species is restricted to xerophilous stony slopes and occurs within a small and fragmented area of ca. 500 km2. We sequenced the COI barcode region of 152 individuals from eight sites covering the entire range of the species. We found four genetic groups mostly coincident with their geographic distribution: a central ancestral group containing shared haplotypes among five localities and three groups restricted to a single locality each. Two of these derived groups were geographically and genetically isolated, while the third and most differentiated group was not geographically isolated. Geomorphologic and paleoclimatic processes during the Pleistocene can explain the divergence found between populations of this low dispersal species with historical fragmentation and secondary contacts. Nonetheless, recent passive large dispersal through streams was also detected in the central group. Overall, our study uncovered four evolutionary units, partially matching morphologically described subspecies, which should be considered in future conservation actions.

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