Mechanismy reprodukční izolace mezi dvěma hybridizujícími druhy pěvců, slavíkem obecným a slavíkem tmavým

v - ABSTRACT (in Czech) - Stěžejním krokem při vzniku nových druhů je evoluce reprodukčně izolačních mechanismů oddělujících genofondy nově vznikajících druhů. O molekulární, fyziologické a genetické podstatě reprodukční izolace víme i přes rostoucí počet studií stále málo. Na příkladu dvou přirozeně hybridizujících druhů pěvců, slavíka obecného (Luscinia megarhynchos) a slavíka tmavého (L. luscinia), jsme zkoumali různé mechanismy reprodukční izolace se zaměřením na postkopulační prezygotické a postzygotické izolační mechanismy. Tyto dva druhy slavíků se oddělily před ~1,8 miliony lety a v současnosti se kříží v sekundární kontaktní zóně probíhající napříč střední a východní Evropou. V rámci této dizertační práce jsme analyzovali genetické složení sekundární kontaktní zóny a ukázali, že v hybridní zóně jsou dominantní rodičovské formy, zatímco F1 hybridů (3,4 %) a časných zpětných kříženců (3,1 %) se zde vyskytuje málo a F2 hybridi úplně chybí. To naznačuje silnou, ale neúplnou reprodukční izolaci. F1 hybridní jedinci byli čtyřikrát častější z jednoho směru křížení než z druhého, což indikuje asymetrickou hybridizaci. Dále jsme ukázali velké mezidruhové rozdíly v morfologii spermií. Spermie slavíka obecného měly delší a širší střední část a bičík, zatímco spermie slavíka tmavého měly větší akrozom. Tyto...iv - ABSTRACT (in English) - A key step in the origin of new species is the evolution of the reproductive isolation mechanisms separating the gene pools of newly emerging species. Despite a growing number of studies, we still know very little about the molecular, physiological and genetic mechanisms underlying reproductive isolation. Hybrid zones represent useful examples of ongoing species differentiation and can provide information about the nature of reproductive isolation separating the species and mechanisms facilitating or limiting the hybridization. Using two naturally hybridizing passerine species, the common nightingale (Luscinia megarhynchos) and the thrush nightingale (L. luscinia), we evaluated several mechanisms of reproductive isolation at the chromosomal, phenotypic, and genetic levels, with a focus on postmating prezygotic (PMPZ) and postzygotic isolation mechanisms. These nightingale species diverged ~1.8 Mya and currently hybridize in a secondary contact zone running across Central and Eastern Europe. First, we analysed the genetic composition of the secondary contact zone, demonstrating that parental forms are predominant in the hybrid zone, with few F1 hybrids (3.4%), early backcross hybrids (3.1%) and the absence of F2 hybrids. This suggests strong but incomplete reproductive isolation....Katedra zoologieDepartment of ZoologyPřírodovědecká fakultaFaculty of Scienc

Multiple glacial refugia and contemporary dispersal shape the genetic structure of an endemic amphibian from the Pyrenees

Historical factors (colonization scenarios, demographic oscillations) and contemporary processes (population connectivity, current population size) largely contribute to shaping species’ present-day genetic diversity and structure. In this study, we use a combination of mitochondrial and nuclear DNA markers to understand the role of Quaternary climatic oscillations and present-day gene flow dynamics in determining the genetic diversity and structure of the newt Calotriton asper (Al. Dugès, 1852), endemic to the Pyrenees. Mitochondrial DNA did not show a clear phylogeographic pattern and presented low levels of variation. In contrast, microsatellites revealed five major genetic lineages with admixture patterns at their boundaries. Approximate Bayesian computation analyses and linear models indicated that the five lineages likely underwent separate evolutionary histories and can be tracked back to distinct glacial refugia. Lineage differentiation started around the Last Glacial Maximum at three focal areas (western, central and eastern Pyrenees) and extended through the end of the Last Glacial Period in the central Pyrenees, where it led to the formation of two more lineages. Our data revealed no evidence of recent dispersal between lineages, whereas borders likely represent zones of secondary contact following expansion from multiple refugia. Finally, we did not find genetic evidence of sex-biased dispersal. This work highlights the importance of integrating past evolutionary processes and present-day gene flow and dispersal dynamics, together with multilocus approaches, to gain insights into what shaped the current genetic attributes of amphibians living in montane habitats.info:eu-repo/semantics/publishedVersio

Mechanisms of reproductive isolation between two hybridizing passerine species, the common nightingale and the thrush nightingale

iv - ABSTRACT (in English) - A key step in the origin of new species is the evolution of the reproductive isolation mechanisms separating the gene pools of newly emerging species. Despite a growing number of studies, we still know very little about the molecular, physiological and genetic mechanisms underlying reproductive isolation. Hybrid zones represent useful examples of ongoing species differentiation and can provide information about the nature of reproductive isolation separating the species and mechanisms facilitating or limiting the hybridization. Using two naturally hybridizing passerine species, the common nightingale (Luscinia megarhynchos) and the thrush nightingale (L. luscinia), we evaluated several mechanisms of reproductive isolation at the chromosomal, phenotypic, and genetic levels, with a focus on postmating prezygotic (PMPZ) and postzygotic isolation mechanisms. These nightingale species diverged ~1.8 Mya and currently hybridize in a secondary contact zone running across Central and Eastern Europe. First, we analysed the genetic composition of the secondary contact zone, demonstrating that parental forms are predominant in the hybrid zone, with few F1 hybrids (3.4%), early backcross hybrids (3.1%) and the absence of F2 hybrids. This suggests strong but incomplete reproductive isolation...

Rapid gene content turnover on the germline-restricted chromosome in songbirds

Abstract The germline-restricted chromosome (GRC) of songbirds represents a taxonomically widespread example of programmed DNA elimination. Despite its apparent indispensability, we still know very little about the GRC’s genetic composition, function, and evolutionary significance. Here we assemble the GRC in two closely related species, the common and thrush nightingale. In total we identify 192 genes across the two GRCs, with many of them present in multiple copies. Interestingly, the GRC appears to be under little selective pressure, with the genetic content differing dramatically between the two species and many GRC genes appearing to be pseudogenized fragments. Only one gene, cpeb1, has a complete coding region in all examined individuals of the two species and shows no copy number variation. The acquisition of this gene by the GRC corresponds with the earliest estimates of the GRC origin, making it a good candidate for the functional indispensability of the GRC in songbirds

Micro Germline-Restricted Chromosome in Blue Tits : Evidence for Meiotic Functions

The germline-restricted chromosome (GRC) is likely present in all songbird species but differs widely in size and gene content. This extra chromosome has been described as either a microchromosome with only limited basic gene content or a macrochromosome with enriched gene functions related to female gonad and embryo development. Here, we assembled, annotated, and characterized the first micro-GRC in the blue tit (Cyanistes caeruleus) using high-fidelity long-read sequencing data. Although some genes on the blue tit GRC show signals of pseudogenization, others potentially have important functions, either currently or in the past. We highlight the GRC gene paralog BMP15, which is among the highest expressed GRC genes both in blue tits and in zebra finches (Taeniopygia guttata) and is known to play a role in oocyte and follicular maturation in other vertebrates. The GRC genes of the blue tit are further enriched for functions related to the synaptonemal complex. We found a similar functional enrichment when analyzing published data on GRC genes from two nightingale species (Luscinia spp.). We hypothesize that these genes play a role in maintaining standard maternal inheritance or in recombining maternal and paternal GRCs during potential episodes of biparental inheritance

High temperatures limit developmental resilience to high-elevation hypoxia in the snake Natrix maura (Squamata: Colubridae)

International audienceClimate change is generating range shifts in many organisms, notably along the altitudinal gradient. However, moving up in altitude exposes organisms to lower oxygen availability, which may negatively affect development and fitness, especially at high temperatures. To test this possibility in a potentially upward-colonizing species, we artificially incubated developing embryos of the viperine snake Natrix maura Linnaeus 1758, using a split-clutch design, in conditions of extreme high elevation or low elevation at two ecologically-relevant incubation temperatures (24 and 32 °C). Embryos at low and extreme high elevations incubated at cool temperatures did not differ in development time, hatchling phenotype or locomotor performance. However, at the warmer incubation temperature and at extreme high elevation, hatching success was reduced. Further, embryonic heart rates were lower, incubation duration longer and juveniles born smaller. Nonetheless, snakes in this treatment were faster swimmers than siblings in other treatment groups, suggesting a developmental trade-off between size and performance. Constraints on development may be offset by the maintenance of important performance metrics, thus suggesting that early life-history stages will not prevent the successful colonization of high-elevation habitat even under the dual limitations of reduced oxygen and increased temperature

Presence of the Fungus B. dendrobatidis, but not B. salamandrivorans, in Wild Pyrenean Brook Newts (Calotriton asper) in Spain and France

International audienceIn the last 20 years, the emergence of chytridiomycosis due to the chytrid fungi Batrachochytrium dendrobatidis (Bd), and the more recently described Batrachochytrium salamandrivorans (Bsal), has caused severe amphibian population regressions across the planet (Bosch et al. 2001; Spitzen-van der Sluijs et al. 2016; Scheele et al. 2019). This has generated an increase in scientific interest to decipher the complex interaction between the environment, the fungus and amphibian hosts, and increased surveillance efforts in many localities (Canessa et al. 2020). Batrachochytrium spp. affect the vital function of the amphibian skin, leading to lethargy or skin discoloration, hyperkeratosis, erosions (even ulcerations in Bsal) of the epidermis, and eventually death (Berger et al. 1998; Weldon et al. 2004; Stuart et al. 2004; Wake and Vredenburg 2010; Martel et al. 2013). Bd is currently found on all continents where amphibians are present (Skerratt et al. 2007), affecting more than 700 species within the three orders of amphibians and has been considered a major threat to amphibian biodiversity worldwide (Crawford et al. 2010; Fisher et al. 2012; Olson et al. 2013; Olson and Ronnenberg 2014)

Presence of the Fungus B. dendrobatidis, but not B. salamandrivorans, in Wild Pyrenean Brook Newts (Calotriton asper) in Spain and France

International audienceIn the last 20 years, the emergence of chytridiomycosis due to the chytrid fungi Batrachochytrium dendrobatidis (Bd), and the more recently described Batrachochytrium salamandrivorans (Bsal), has caused severe amphibian population regressions across the planet (Bosch et al. 2001; Spitzen-van der Sluijs et al. 2016; Scheele et al. 2019). This has generated an increase in scientific interest to decipher the complex interaction between the environment, the fungus and amphibian hosts, and increased surveillance efforts in many localities (Canessa et al. 2020). Batrachochytrium spp. affect the vital function of the amphibian skin, leading to lethargy or skin discoloration, hyperkeratosis, erosions (even ulcerations in Bsal) of the epidermis, and eventually death (Berger et al. 1998; Weldon et al. 2004; Stuart et al. 2004; Wake and Vredenburg 2010; Martel et al. 2013). Bd is currently found on all continents where amphibians are present (Skerratt et al. 2007), affecting more than 700 species within the three orders of amphibians and has been considered a major threat to amphibian biodiversity worldwide (Crawford et al. 2010; Fisher et al. 2012; Olson et al. 2013; Olson and Ronnenberg 2014)

Presence of the Fungus Batrachochytrium dendrobatidis, but not Batrachochytrium salamandrivorans, in Wild Pyrenean Brook Newts (Calotriton asper) in Spain and France

Este artículo contiene 6 páginas, 12 tabla, 2 figuras.This work was supported by the French Laboratory of Excellence project TULIP (ANR-10-LABX-41; ANR-11-IDEX-0002-02) by the INTERREG POCTEFA ECTOPYR (no. EFA031/15) and by the LIFE+ LIMNOPIRINEUS (LIFE13 NAT/ ES1210) projects.Peer reviewe