Browsing by Subject "speciation"

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  • Nováková, Eliška; Zablatzká, Lenka; Brus, Jan; Nesrstová, Viktorie; Hanáček, Pavel; Kalendar, Ruslan; Cvrčková, Fatima; Majeský, Ľuboš; Smýkal, Petr (2019)
    Reproductive isolation is an important component of species differentiation. The plastid accD gene coding for the acetyl-CoA carboxylase subunit and the nuclear bccp gene coding for the biotin carboxyl carrier protein were identified as candidate genes governing nuclear-cytoplasmic incompatibility in peas. We examined the allelic diversity in a set of 195 geographically diverse samples of both cultivated (Pisum sativum, P. abyssinicum) and wild (P. fulvum and P. elatius) peas. Based on deduced protein sequences, we identified 34 accD and 31 bccp alleles that are partially geographically and genetically structured. The accD is highly variable due to insertions of tandem repeats. P. fulvum and P. abyssinicum have unique alleles and combinations of both genes. On the other hand, partial overlap was observed between P. sativum and P. elatius. Mapping of protein sequence polymorphisms to 3D structures revealed that most of the repeat and indel polymorphisms map to sequence regions that could not be modeled, consistent with this part of the protein being less constrained by requirements for precise folding than the enzymatically active domains. The results of this study are important not only from an evolutionary point of view but are also relevant for pea breeding when using more distant wild relatives.
  • Hekkala, Toni (Helsingin yliopisto, 2019)
    Arsenic (As) is a metalloid naturally present in the environment. Arsenic species vary in toxicity. Metal mining has contributed to the anthropogenic input of arsenic to groundwaters and surface waters. In this study, water samples were collected from 20 sample points in three mining-impacted study areas in Finland: the former Ylöjärvi Cu–W–As and Haveri Au–Cu mines, and the active Pyhäsalmi Zn–Cu mine. Six groundwater well samples, eleven surface water samples and three tailings seepage collection ditch samples were analyzed for dissolved arsenic speciation by HPLC-ICP-MS and for geochemical composition by ICP-MS, titration, and ion chromatography. Dissolved arsenic concentrations ranged from 14.2 to 6649 µg L-1 in samples collected at the Ylöjärvi study area, from 0.5 to 6.2 µg L-1 in samples collected at the Haveri study area, and from 0.2 to 9.4 µg L-1 in samples collected at the Pyhäsalmi study area. In all study areas, measured dissolved arsenic concentrations showed a general decrease from the tailings to the surroundings. Speciation analysis showed that two of the samples collected at the Ylöjärvi study area had arsenite [As(III)] as the dominant form of dissolved inorganic arsenic (iAs), three had arsenate [As(V)] as the dominant form of dissolved iAs, and four had a mixture of both. In the water samples collected at the Haveri and Pyhäsalmi study areas, all concentrations of dissolved arsenic species were below method detection limits. Also, none of the 22 water samples analyzed for arsenic speciation had dissolved MMA or DMA concentrations above method detection limits. Identification of dissolved arsenic species in the sampled waters in Haveri and Pyhäsalmi, and of MMA and DMA in all sampled waters requires more detailed study. A significant 2-tailed Pearson correlation between dissolved arsenic and dissolved molybdenum (Mo) (r=0.80**, n=20), and dissolved arsenic and dissolved potassium (K) (0.68**, n=19) suggests that in these three study areas the distributions of dissolved arsenic and Mo, as well as dissolved arsenic and K may be controlled by the same environmental variables. Anomalously high maximum concentrations of dissolved Al, Ca, Co, Cu, Fe, Ni, and SO4 were measured in surface water samples collected at the Ylöjärvi and Haveri study areas, and in a seepage collection ditch sample collected at the Pyhäsalmi study area.
  • Sirkiä, Päivi M.; McFarlane, S. Eryn; Jones, William; Wheatcroft, David; Ålund, Murielle; Rybinski, Jakub; Qvarnstrom, Anna (2018)
    Divergence in the onset of reproduction can act as an important source of reproductive isolation (i.e., allochronic isolation) between co-occurring young species, but evidence for the evolutionary processes leading to such divergence is often indirect. While advancing spring seasons strongly affect the onset of reproduction in many taxa, it remains largely unexplored whether contemporary spring advancement directly affects allochronic isolation between young species. We examined how increasing spring temperatures affected onset of reproduction and thereby hybridization between pied and collared flycatchers (Ficedula spp.) across habitat types in a young secondary contact zone. We found that both species have advanced their timing of breeding in 14 years. However, selection on pied flycatchers to breed earlier was weaker, resulting in a slower response to advancing springs compared to collared flycatchers and thereby build-up of allochronic isolation between the species. We argue that a preadaptation to a broader niche use (diet) of pied flycatchers explains the slower response to raising spring temperature, but that reduced risk to hybridize may contribute to further divergence in the onset of breeding in the future. Our results show that minor differences in the response to environmental change of co-occurring closely related species can quickly cause allochronic isolation.
  • Byers, Kelsey J. R. P.; Darragh, Kathy; Fernanda Garza, Sylvia; Abondano Almeida, Diana; Warren, Ian A.; Rastas, Pasi M. A.; Merrill, Richard M.; Schulz, Stefan; McMillan, W. Owen; Jiggins, Chris D. (2021)
    The degree to which loci promoting reproductive isolation cluster in the genome-that is, the genetic architecture of reproductive isolation-can influence the tempo and mode of speciation. Tight linkage between these loci can facilitate speciation in the face of gene flow. Pheromones play a role in reproductive isolation in many Lepidoptera species, and the role of endogenously produced compounds as secondary metabolites decreases the likelihood of pleiotropy associated with many barrier loci. Heliconius butterflies use male sex pheromones to both court females (aphrodisiac wing pheromones) and ward off male courtship (male-transferred antiaphrodisiac genital pheromones), and it is likely that these compounds play a role in reproductive isolation between Heliconius species. Using a set of backcross hybrids between H. melpomene and H. cydno, we investigated the genetic architecture of putative male pheromone compound production. We found a set of 40 significant quantitative trait loci (QTL) representing 33 potential pheromone compounds. QTL clustered significantly on two chromosomes, chromosome 8 for genital compounds and chromosome 20 for wing compounds, and chromosome 20 was enriched for potential pheromone biosynthesis genes. There was minimal overlap between pheromone QTL and known QTL for mate choice and color pattern. Nonetheless, we did detect linkage between a QTL for wing androconial area and optix, a color pattern locus known to play a role in reproductive isolation in these species. This tight clustering of putative pheromone loci might contribute to coincident reproductive isolating barriers, facilitating speciation despite ongoing gene flow.
  • Zamora, Juan Carlos; Svensson, Mans; Kirschner, Roland; Olariaga, Ibai; Ryman, Svengunnar; Alberto Parra, Luis; Geml, Jozsef; Rosling, Anna; Adamcik, Slavomir; Ahti, Teuvo; Aime, M. Catherine; Ainsworth, A. Martyn; Albert, Laszlo; Alberto, Edgardo; Garcia, Alberto Altes; Ageev, Dmitry; Agerer, Reinhard; Aguirre-Hudson, Begona; Ammirati, Joe; Andersson, Harry; Angelini, Claudio; Antonin, Vladimir; Aoki, Takayuki; Aptroot, Andre; Argaud, Didier; Sosa, Blanca Imelda Arguello; Aronsen, Arne; Arup, Ulf; Asgari, Bita; Assyov, Boris; Atienza, Violeta; Bandini, Ditte; Baptista-Ferreira, Joao Luis; Baral, Hans-Otto; Baroni, Tim; Barreto, Robert Weingart; Baker, Henry; Bell, Ann; Bellanger, Jean-Michel; Bellu, Francesco; Bemmann, Martin; Bendiksby, Mika; Bendiksen, Egil; Bendiksen, Katriina; Benedek, Lajos; Beresova-Guttova, Anna; Berger, Franz; Berndt, Reinhard; Bernicchia, Annarosa; Biketova, Alona Yu; Bizio, Enrico; Bjork, Curtis; Boekhout, Teun; Boertmann, David; Bohning, Tanja; Boittin, Florent; Boluda, Carlos G.; Boomsluiter, Menno W.; Borovicka, Jan; Brandrud, Tor Erik; Braun, Uwe; Brodo, Irwin; Bulyonkova, Tatiana; Burdsall, Harold H.; Buyck, Bart; Burgaz, Ana Rosa; Calatayud, Vicent; Callac, Philippe; Campo, Emanuele; Candusso, Massimo; Capoen, Brigitte; Carbo, Joaquim; Carbone, Matteo; Castaneda-Ruiz, Rafael F.; Castellano, Michael A.; Chen, Jie; Clerc, Philippe; Consiglio, Giovanni; Corriol, Gilles; Courtecuisse, Regis; Crespo, Ana; Cripps, Cathy; Crous, Pedro W.; da Silva, Gladstone Alves; da Silva, Meiriele; Dam, Marjo; Dam, Nico; Dammrich, Frank; Das, Kanad; Davies, Linda; De Crop, Eske; De Kesel, Andre; De Lange, Ruben; Bonzi, Barbara De Madrignac; dela Cruz, Thomas Edison E.; Delgat, Lynn; Demoulin, Vincent; Desjardin, Dennis E.; Diederich, Paul; Dima, Balint; Dios, Maria Martha; Divakar, Pradeep Kumar; Douanla-Meli, Clovis; Douglas, Brian; Drechsler-Santos, Elisandro Ricardo; Dyer, Paul S.; Eberhardt, Ursula; Ertz, Damien; Esteve-Raventos, Fernando; Salazar, Javier Angel Etayo; Evenson, Vera; Eyssartier, Guillaume; Farkas, Edit; Favre, Alain; Fedosova, Anna G.; Filippa, Mario; Finy, Peter; Flakus, Adam; Fos, Simon; Fournier, Jacques; Fraiture, Andre; Franchi, Paolo; Molano, Ana Esperanza Franco; Friebes, Gernot; Frisch, Andreas; Fryday, Alan; Furci, Giuliana; Marquez, Ricardo Galan; Garbelotto, Matteo; Garcia-Martin, Joaquina Maria; Otalora, Monica A. Garcia; Sanchez, Dania Garcia; Gardiennet, Alain; Garnica, Sigisfredo; Benavent, Isaac Garrido; Gates, Genevieve; Gerlach, Alice da Cruz Lima; Ghobad-Nejhad, Masoomeh; Gibertoni, Tatiana B.; Grebenc, Tine; Greilhuber, Irmgard; Grishkan, Bella; Groenewald, Johannes Z.; Grube, Martin; Gruhn, Gerald; Gueidan, Cecile; Gulden, Gro; Gusmao, Luis F. P.; Hafellner, Josef; Hairaud, Michel; Halama, Marek; Hallenberg, Nils; Halling, Roy E.; Hansen, Karen; Harder, Christoffer Bugge; Heilmann-Clausen, Jacob; Helleman, Stip; Henriot, Alain; Hernandez-Restrepo, Margarita; Herve, Raphael; Hobart, Caroline; Hoffmeister, Mascha; Hoiland, Klaus; Holec, Jan; Holien, Hakon; Hughes, Karen; Hubka, Vit; Huhtinen, Seppo; Ivancevic, Boris; Jagers, Marian; Jaklitsch, Walter; Jansen, AnnaElise; Jayawardena, Ruvishika S.; Jeppesen, Thomas Stjernegaard; Jeppson, Mikael; Johnston, Peter; Jorgensen, Per Magnus; Karnefelt, Ingvar; Kalinina, Liudmila B.; Kantvilas, Gintaras; Karadelev, Mitko; Kasuya, Taiga; Kautmanova, Ivona; Kerrigan, Richard W.; Kirchmair, Martin; Kiyashko, Anna; Knapp, Daniel G.; Knudsen, Henning; Knudsen, Kerry; Knutsson, Tommy; Kolarik, Miroslav; Koljalg, Urmas; Kosuthova, Alica; Koszka, Attila; Kotiranta, Heikki; Kotkova, Vera; Koukol, Ondrej; Kout, Jiri; Kovacs, Gabor M.; Kriz, Martin; Kruys, Asa; Kudera, Viktor; Kudzma, Linas; Kuhar, Francisco; Kukwa, Martin; Kumar, T. K. Arun; Kunca, Vladimir; Kusan, Ivana; Kuyper, Thomas W.; Lado, Carlos; Laessoe, Thomas; Laine, Patrice; Langer, Ewald; Larsson, Ellen; Larsson, Karl-Henrik; Laursen, Gary; Lechat, Christian; Lee, Serena; Lendemer, James C.; Levin, Laura; Lindemann, Uwe; Lindstrom, Hakan; Liu, Xingzhong; Hernandez, Regulo Carlos Llarena; Llop, Esteve; Locsmandi, Csaba; Lodge, Deborah Jean; Loizides, Michael; Lokos, Laszlo; Luangsa-ard, Jennifer; Luderitz, Matthias; Lumbsch, Thorsten; Lutz, Matthias; Mahoney, Dan; Malysheva, Ekaterina; Malysheva, Vera; Manimohan, Patinjareveettil; Mann-Felix, Yasmina; Marques, Guilhermina; Martinez-Gil, Ruben; Marson, Guy; Mata, Gerardo; Matheny, P. Brandon; Mathiassen, Geir Harald; Matocec, Neven; Mayrhofer, Helmut; Mehrabi, Mehdi; Melo, Ireneia; Mesic, Armin; Methven, Andrew S.; Miettinen, Otto; Romero, Ana M. Millanes; Miller, Andrew N.; Mitchell, James K.; Moberg, Roland; Moreau, Pierre-Arthur; Moreno, Gabriel; Morozova, Olga; Morte, Asuncion; Muggia, Lucia; Gonzalez, Guillermo Munoz; Myllys, Leena; Nagy, Istvan; Nagy, Laszlo G.; Neves, Maria Alice; Niemela, Tuomo; Nimis, Pier Luigi; Niveiro, Nicolas; Noordeloos, Machiel E.; Nordin, Anders; Noumeur, Sara Raouia; Novozhilov, Yuri; Nuytinck, Jorinde; Ohenoja, Esteri; Fiuza, Patricia Oliveira; Orange, Alan; Ordynets, Alexander; Ortiz-Santana, Beatriz; Pacheco, Leticia; Pal-Fam, Ferenc; Palacio, Melissa; Palice, Zdenek; Papp, Viktor; Partel, Kadri; Pawlowska, Julia; Paz, Aurelia; Peintner, Ursula; Pennycook, Shaun; Pereira, Olinto Liparini; Daniels, Pablo Perez; Capella, Miguel A. Perez-De-Gregorio; del Amo, Carlos Manuel Perez; Gorjon, Sergio Perez; Perez-Ortega, Sergio; Perez-Vargas, Israel; Perry, Brian A.; Petersen, Jens H.; Petersen, Ronald H.; Pfister, Donald H.; Phukhamsakda, Chayanard; Piatek, Marcin; Piepenbring, Meike; Pino-Bodas, Raquel; Esquivel, Juan Pablo Pinzon; Pirot, Paul; Popov, Eugene S.; Popoff, Orlando; Alvaro, Maria Prieto; Printzen, Christian; Psurtseva, Nadezhda; Purahong, Witoon; Quijada, Luis; Rambold, Gerhard; Ramirez, Natalia A.; Raja, Huzefa; Raspe, Olivier; Raymundo, Tania; Reblova, Martina; Rebriev, Yury A.; Garcia, Juan de Dios Reyes; Ripoll, Miguel Angel Ribes; Richard, Franck; Richardson, Mike J.; Rico, Victor J.; Robledo, Gerardo Lucio; Barbosa, Flavia Rodrigues; Rodriguez-Caycedo, Cristina; Rodriguez-Flakus, Pamela; Ronikier, Anna; Casas, Luis Rubio; Rusevska, Katerina; Saar, Gunter; Saar, Irja; Salcedo, Isabel; Martinez, Sergio M. Salcedo; Montoya, Carlos A. Salvador; Sanchez-Ramirez, Santiago; Sandoval-Sierra, J. Vladimir; Santamaria, Sergi; Monteiro, Josiane Santana; Schroers, Hans Josef; Schulz, Barbara; Schmidt-Stohn, Geert; Schumacher, Trond; Senn-Irlet, Beatrice; Sevcikova, Hana; Shchepin, Oleg; Shirouzu, Takashi; Shiryaev, Anton; Siepe, Klaus; Sir, Esteban B.; Sohrabi, Mohammad; Soop, Karl; Spirin, Viacheslav; Spribille, Toby; Stadler, Marc; Stalpers, Joost; Stenroos, Soili; Suija, Ave; Sunhede, Stellan; Svantesson, Sten; Svensson, Sigvard; Svetasheva, Tatyana Yu; Swierkosz, Krzysztof; Tamm, Heidi; Taskin, Hatira; Taudiere, Adrien; Tedebrand, Jan-Olof; Lahoz, Raul Tena; Temina, Marina; Thell, Arne; Thines, Marco; Thor, Goren; Thus, Holger; Tibell, Leif; Tibell, Sanja; Timdal, Einar; Tkalcec, Zdenko; Tonsberg, Tor; Trichies, Gerard; Triebel, Dagmar; Tsurykau, Andrei; Tulloss, Rodham E.; Tuovinen, Veera; Sosa, Miguel Ulloa; Urcelay, Carlos; Valade, Francois; Garza, Ricardo Valenzuela; van den Boom, Pieter; Van Vooren, Nicolas; Vasco-Palacios, Aida M.; Vauras, Jukka; Santos, Juan Manuel Velasco; Vellinga, Else; Verbeken, Annemieke; Vetlesen, Per; Vizzini, Alfredo; Voglmayr, Hermann; Volobuev, Sergey; von Brackel, Wolfgang; Voronina, Elena; Walther, Grit; Watling, Roy; Weber, Evi; Wedin, Mats; Weholt, Oyvind; Westberg, Martin; Yurchenko, Eugene; Zehnalek, Petr; Zhang, Huang; Zhurbenko, Mikhail P.; Ekmani, Stefan (2018)
    Nomenclatural type definitions are one of the most important concepts in biological nomenclature. Being physical objects that can be re-studied by other researchers, types permanently link taxonomy (an artificial agreement to classify biological diversity) with nomenclature (an artificial agreement to name biological diversity). Two proposals to amend the International Code of Nomenclature for algae, fungi, and plants (ICN), allowing DNA sequences alone (of any region and extent) to serve as types of taxon names for voucherless fungi (mainly putative taxa from environmental DNA sequences), have been submitted to be voted on at the 11th International Mycological Congress (Puerto Rico, July 2018). We consider various genetic processes affecting the distribution of alleles among taxa and find that alleles may not consistently and uniquely represent the species within which they are contained. Should the proposals be accepted, the meaning of nomenclatural types would change in a fundamental way from physical objects as sources of data to the data themselves. Such changes are conducive to irreproducible science, the potential typification on artefactual data, and massive creation of names with low information content, ultimately causing nomenclatural instability and unnecessary work for future researchers that would stall future explorations of fungal diversity. We conclude that the acceptance of DNA sequences alone as types of names of taxa, under the terms used in the current proposals, is unnecessary and would not solve the problem of naming putative taxa known only from DNA sequences in a scientifically defensible way. As an alternative, we highlight the use of formulas for naming putative taxa (candidate taxa) that do not require any modification of the ICN.
  • Young, J. Peter W.; Moeskjaer, Sara; Afonin, Alexey; Rahi, Praveen; Maluk, Marta; James, Euan K.; Cavassim, Maria Izabel A.; Rashid, M. Harun-or; Aserse, Aregu Amsalu; Perry, Benjamin J.; Wang, En Tao; Velazquez, Encarna; Andronov, Evgeny E.; Tampakaki, Anastasia; Flores Felix, Jose David; Rivas Gonzalez, Raul; Youseif, Sameh H.; Lepetit, Marc; Boivin, Stephane; Jorrin, Beatriz; Kenicer, Gregory J.; Peix, Alvaro; Hynes, Michael F.; Ramirez-Bahena, Martha Helena; Gulati, Arvind; Tian, Chang-Fu (2021)
    Bacteria currently included in Rhizobium leguminosarum are too diverse to be considered a single species, so we can refer to this as a species complex (the Rlc). We have found 429 publicly available genome sequences that fall within the Rlc and these show that the Rlc is a distinct entity, well separated from other species in the genus. Its sister taxon is R. anhuiense. We constructed a phylogeny based on concatenated sequences of 120 universal (core) genes, and calculated pairwise average nucleotide identity (ANI) between all genomes. From these analyses, we concluded that the Rlc includes 18 distinct genospecies, plus 7 unique strains that are not placed in these genospecies. Each genospecies is separated by a distinct gap in ANI values, usually at approximately 96% ANI, implying that it is a 'natural' unit. Five of the genospecies include the type strains of named species: R. laguerreae, R. sophorae, R. ruizarguesonis, "R. indicum" and R. leguminosarum itself. The 16S ribosomal RNA sequence is remarkably diverse within the Rlc, but does not distinguish the genospecies. Partial sequences of housekeeping genes, which have frequently been used to characterize isolate collections, can mostly be assigned unambiguously to a genospecies, but alleles within a genospecies do not always form a clade, so single genes are not a reliable guide to the true phylogeny of the strains. We conclude that access to a large number of genome sequences is a powerful tool for characterizing the diversity of bacteria, and that taxonomic conclusions should be based on all available genome sequences, not just those of type strains.
  • Lanki, Maiju (Helsingfors universitet, 2013)
    Adaptive radiation is an important mechanism of evolution, which can lead to emergence of sympatric species or morphotypes. Among other biological interactions, parasitic pressure can have significant evolutionary implications for host populations by reducing the fitness of the host individuals. Parasite community structure of fishes is typically strongly dependent on both host ecology (e.g. habitat and feeding behaviour) and environmental factors (e.g. water quality and temperature). However, the relative importance of these factors for parasite-mediated speciation is not known. Also, host gender-specific differences in parasite communities can have an effect on the differentiation of host morphs. In this Master's thesis, I focused on differences in parasite communities of sympatric morphs of three-spine stickleback (Gasterosteus aculeatus) in two large Icelandic lakes, Thingvallavatn and Mývatn. In these lakes, the habitats of sympatric mud and lava morphs are the same (soft/hard bottom), but the habitat water temperatures are opposite between the lakes. In this unique system, it is thus possible to compare between the effects of host ecology and water temperature on parasite community structure and strength of parasite-mediated selection. Additionally, I studied the effect of host sex on the parasitic pressure. There is also a third stickleback morph, Nitella morph, inhabiting the cold limnetic habitats in Lake Thingvallavatn. I sampled the stickleback morphs from both lakes and identified their parasite species. I discovered a total of five parasite genera: trematodes Apatemon and Diplostomum, and cestodes Diphyllobothrium, Proteocephalus and Schistocephalus. Most of the observed parasites have negative effects on health and fitness of the host. I found more parasites in sticklebacks living in higher temperature in both lakes regardless of the morph. When comparing the cold water morphs in Thingvallavatn, parasite abundance was higher in the limnetic Nitella morph than in the shallow water lava morph. Fish gender had an effect on parasitism only in Thingvallavatn as males of both lava and Nitella morphs were more heavily infected with cestodes. Similarities in parasite communities with water temperature indicate that water temperature mainly determines parasite infections in this system instead of host ecology. As similar fish morphotypes exist in different lakes under opposite parasitic pressure, parasitism has unlikely initiated host differentiation, but differences in infection probably have emerged secondary to the ecological specialization of the morphs to different habitats. These results are among the first to tackle the key question in parasite-mediated divergent selection: at which point of the speciation process parasite communities become differentiated and thus can have an effect on speciation. However, the comparison between the cold water morphs (lava and Nitella) indicates that although water temperature seems to be the main factor controlling infections in this system, its effect may still be over ridden by host ecology. Sex-depended differences in parasitic pressure, on the other hand, are likely to reflect specific characteristics of each fish population and lake. These results suggest complex interactions between host ecology and abiotic environment, such as water temperature, in determining the parasite community structure. Hence both factors have to take into consideration when studying the role of parasites in speciation processes. In future, it is necessary to pinpoint the stage of the host speciation process when parasite infections become differentiated in replicated systems to gain comprehensive understanding of the role of parasites in adaptive radiations.
  • Boluda, C. G.; Rico, V. J.; Divakar, P. K.; Nadyeina, O.; Myllys, L.; McMullin, R. T.; Zamora, J. C.; Scheidegger, C.; Hawksworth, D. L. (2019)
    In many lichen-forming fungi, molecular phylogenetic analyses lead to the discovery of cryptic species within traditional morphospecies. However, in some cases, molecular sequence data also questions the separation of phenotypically characterised species. Here we apply an integrative taxonomy approach - including morphological, chemical, molecular, and distributional characters - to re-assess species boundaries in a traditionally speciose group of hair lichens, Bryoria sect. Implexae. We sampled multilocus sequence and microsatellite data from 142 specimens from a broad intercontinental distribution. Molecular data included DNA sequences of the standard fungal markers ITS, IGS, GAPDH, two newly tested loci (FRBi15 and FRBi16), and SSR frequencies from 18 microsatellite markers. Datasets were analysed with Bayesian and maximum likelihood phylogenetic reconstruction, phenogram reconstruction, STRUCTURE Bayesian clustering, principal coordinate analysis, haplotype network, and several different species delimitation analyses (ABGD, PTP, GMYC, and DISSECT). Additionally, past population demography and divergence times are estimated. The different approaches to species recognition do not support the monophyly of the 11 currently accepted morphospecies, and rather suggest the reduction of these to four phylogenetic species. Moreover, three of these are relatively recent in origin and cryptic, including phenotypically and chemically variable specimens. Issues regarding the integration of an evolutionary perspective into taxonomic conclusions in species complexes, which have undergone recent diversification, are discussed. The four accepted species, all epitypified by sequenced material, are Bryoria fuscescens, B. glabra, B. kockiana, and B. pseudofuscescens. Ten species rank names are reduced to synonymy. In the absence of molecular data, they can be recorded as the B. fuscescens complex. Intraspecific phenotype plasticity and factors affecting the speciation of different morphospecies in this group of Bryoria are outlined.
  • Pulido-Santacruz, Paola; Aleixo, Alexandre; Weir, Jason T. (2020)
    The incidence of introgression during the diversification process and the timespan following divergence when introgression is possible are poorly understood in the neotropics where high species richness could provide extensive opportunities for genetic exchange. We used thousands of genome-wide SNPs to infer phylogenetic relationships, calculate ages of splitting, and to estimate the timing of introgression in a widespread avian neotropical genus of woodcreepers. Five distinct introgression events were reconstructed involving taxa classified both as subspecies and species including lineages descending from the basal-most split, dated to 7.3 million years ago. Introgression occurred between just a few hundred thousand to about 2.5 million years following divergence, suggesting substantial portions of the genome are capable of introgressing across taxa boundaries during a protracted time window of a few million years following divergence. Despite this protracted time window, we found that the proportion of the genome introgressing (6-11%) declines with the time of introgression following divergence, suggesting that the genome becomes progressively more immune to introgression as reproductive isolation increases.
  • Miraldo, Andreia; Duplouy, Anne (2019)
    Determining the drivers of diversity is a major topic in biology. Due to its high level of micro-endemism in many taxa, Madagascar has been described as one of Earth's biodiversity hotspot. The exceptional Malagasy biodiversity has been shown to be the result of various eco-evolutionary mechanisms that have taken place on this large island since its isolation from other landmasses. Extensive phylogenetic analyses have, for example, revealed that most of the dung beetle radiation events have arisen due to allopatric speciation, and adaptation to altitudinal and/or longitudinal gradients. But other biotic factors, that have yet to be identified, might also be at play. Wolbachia is a maternally transmitted endosymbiotic bacterium widespread in insects. The bacterium is well-known for its ability to modify its host reproductive system in ways that may lead to either discordance patterns between the host mitochondrial and nuclear phylogenies, and in some cases to speciation. Here, we used theMultiLocus Sequence Typing system, to identify and characterize five Wolbachia strains infecting several species within the Nanos clypeatus dung beetle clade. We discuss the implications of these Wolbachia strains for the evolution and diversification of their dung beetle hosts in Madagascar.
  • Kulmuni, Jonna; Nouhaud, Pierre; Pluckrose, Lucy; Satokangas, Ina; Dhaygude, Kishor; Butlin, Roger K. (2020)
    Speciation underlies the generation of novel biodiversity. Yet, there is much to learn about how natural selection shapes genomes during speciation. Selection is assumed to act against gene flow at barrier loci, promoting reproductive isolation. However, evidence for gene flow and selection is often indirect and we know very little about the temporal stability of barrier loci. Here we utilize haplodiploidy to identify candidate male barrier loci in hybrids between two wood ant species. As ant males are haploid, they are expected to reveal recessive barrier loci, which can be masked in diploid females if heterozygous. We then test for barrier stability in a sample collected 10 years later and use survival analysis to provide a direct measure of natural selection acting on candidate male barrier loci. We find multiple candidate male barrier loci scattered throughout the genome. Surprisingly, a proportion of them are not stable after 10 years, natural selection apparently switching from acting against to favouring introgression in the later sample. Instability of the barrier effect and natural selection for introgressed alleles could be due to environment-dependent selection, emphasizing the need to consider temporal variation in the strength of natural selection and the stability of the barrier effect at putative barrier loci in future speciation work.
  • Kulmuni, J.; Westram, A. M. (2017)
    The possibility of intrinsic barriers to gene flow is often neglected in empirical research on local adaptation and speciation with gene flow, for example when interpreting patterns observed in genome scans. However, we draw attention to the fact that, even with gene flow, divergent ecological selection may generate intrinsic barriers involving both ecologically selected and other interacting loci. Mechanistically, the link between the two types of barriers may be generated by genes that have multiple functions (i.e., pleiotropy), and/or by gene interaction networks. Because most genes function in complex networks, and their evolution is not independent of other genes, changes evolving in response to ecological selection can generate intrinsic barriers as a by-product. A crucial question is to what extent such by-product barriers contribute to divergence and speciation-that is whether they stably reduce gene flow. We discuss under which conditions by-product barriers may increase isolation. However, we also highlight that, depending on the conditions (e.g., the amount of gene flow and the strength of selection acting on the intrinsic vs. the ecological barrier component), the intrinsic incompatibility may actually destabilize barriers to gene flow. In practice, intrinsic barriers generated as a by-product of divergent ecological selection may generate peaks in genome scans that cannot easily be interpreted. We argue that empirical studies on divergence with gene flow should consider the possibility of both ecological and intrinsic barriers. Future progress will likely come from work combining population genomic studies, experiments quantifying fitness and molecular studies on protein function and interactions.
  • Satokangas, Ina; Martin, S. H.; Helanterä, H.; Saramaki, J.; Kulmuni, J. (2020)
    All genes interact with other genes, and their additive effects and epistatic interactions affect an organism's phenotype and fitness. Recent theoretical and empirical work has advanced our understanding of the role of multi-locus interactions in speciation. However, relating different models to one another and to empirical observations is challenging. This review focuses on multi-locus interactions that lead to reproductive isolation (RI) through reduced hybrid fitness. We first review theoretical approaches and show how recent work incorporating a mechanistic understanding of multi-locus interactions recapitulates earlier models, but also makes novel predictions concerning the build-up of RI. These include high variance in the build-up rate of RI among taxa, the emergence of strong incompatibilities producing localized barriers to introgression, and an effect of population size on the build-up of RI. We then review recent experimental approaches to detect multi-locus interactions underlying RI using genomic data. We argue that future studies would benefit from overlapping methods like ancestry disequilibrium scans, genome scans of differentiation and analyses of hybrid gene expression. Finally, we highlight a need for further overlap between theoretical and empirical work, and approaches that predict what kind of patterns multi-locus interactions resulting in incompatibilities will leave in genome-wide polymorphism data. This article is part of the theme issue 'Towards the completion of speciation: the evolution of reproductive isolation beyond the first barriers'.
  • Law, Kathleen A.; Parry, Stephen A.; Bryan, Nicholas D.; Heath, Sarah L.; Heald, Steven; Knight, Darrell; O'Brien, Luke; Fuller, Adam J.; Bower, William R.; Law, Gareth T. W.; Livens, Francis R. (2019)
    One of the most challenging components of the UK nuclear legacy is Magnox sludge, arising from the corrosion of Mg alloy-clad irradiated metallic U fuel that has been stored in high pH ponds. The sludges mainly comprise Mg hydroxide and carbonate phases, contaminated with fission products and actinides, including Pu. Cementation and deep geological disposal is one option for the long-term management of this material, but there is a need to understand how Pu may be leached from the waste, if it is exposed to groundwater. Here, we show that cemented Mg(OH)2 powder prepared with Pu(IV)aq is altered on contact with water to produce a visibly altered ‘leached zone’, which penetrates several hundred microns into the sample. In turn, this zone shows slow leaching of Pu, with long-term leaching rates between 1.8–4.4 × 10−5% of total Pu per day. Synchrotron micro-focus X-ray fluorescence mapping identified decreased Pu concentration within the ‘leached zone’. A comparison of micro-focus X-ray absorption spectroscopy (μ-XAS) spectra collected across both leached and unleached samples showed little variation, and indicated that Pu was present in a similar oxidation state and coordination environment. Fitting of the XANES spectra between single oxidation state standards and EXAFS modeling showed that Pu was present as a mixture of Pu(IV) and Pu(V). The change in Pu oxidation from the stock solution suggests that partial Pu oxidation occurred during sample ageing. Similarity in the XAS spectra from all samples, with different local chemistries, indicated that the Pu oxidation state was not perturbed by macro-scale variations in cement chemistry, surface oxidation, sample aging, or the leaching treatment. These experiments have demonstrated the potential for leaching of Pu from cementitious waste forms, and its underlying significance requires further investigation.
  • Cronemberger, Aurea A.; Aleixo, Alexandre; Mikkelsen, Else K.; Weir, Jason T. (2020)
    How species evolve reproductive isolation in the species-rich Amazon basin is poorly understood in vertebrates. Here, we sequenced a reference genome and used a genome-wide sample of SNPs to analyze a hybrid zone between two highly cryptic species ofHypocnemiswarbling-antbirds-the Rondonia warbling-antbird (H. ochrogyna) and Spix's warbling-antbird (H. striata)-in a headwater region of southern Amazonia. We found that both species commonly hybridize, producing F(1)s and a variety of backcrosses with each species but we detected only one F-2-like hybrid. Patterns of heterozygosity, hybrid index, and interchromosomal linkage disequilibrium in hybrid populations closely match expectations under strong postzygotic isolation. Hybrid zone width (15.4 km) was much narrower than expected (211 km) indicating strong selection against hybrids. A remarkably high degree of concordance in cline centers and widths across loci, and a lack of reduced interspecificF(st)between populations close to versus far from the contact zone, suggest that genetic incompatibilities have rendered most of the genome immune to introgression. These results support intrinsic postzygotic isolation as a driver of speciation in a moderately young cryptic species pair from the Amazon and suggest that species richness of the Amazon may be grossly underestimated.