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Background Multidirectional interactions in social (or communication) networks can have a profound effect on mate choice behavior. For example, Poecilia mexicana males show weaker expression of mating preferences when being observed by an audience male. It was suggested that this behavior is an adaptation to reduce sperm competition risk, which arises because commonly preferred female phenotypes will receive attention also by surrounding males, and/or because the audience male can copy the focal male's mate choice. Do P. mexicana males indeed respond to perceived sperm competition risk? We gave males a choice between two females and repeated the tests under one of the following conditions: (1) during the 2nd part of the tests an empty transparent cylinder was presented (control); (2) an audience male inside the cylinder observed the focal male throughout the 2nd part, or (3) the audience male was presented only before the tests, but could not eavesdrop during the actual choice tests (non-specific sperm competition risk treatments); (4) the focal male could see a rival male sexually interacting with the previously preferred, or (5) with the non-preferred female before the 2nd part of the tests (specific sperm competition risk treatments). Results When comparing the strength of individual male preferences between the 1st and 2nd part of the tests (before and after presentation of an audience), male preferences declined slightly also during the control treatment (1). However, the decrease in strength of male preferences was more than two-fold stronger in audience treatment (2), i.e., with non-specific sperm competition risk including the possibility for visual eavesdropping by the audience male. No audience effect was found in treatments (3) and (5), but a weak effect was also seen when the focal male had seen the previously preferred female sexually interact with a rival male (treatment 4; specific sperm competition risk). Conclusions When comparing the two 'non-specific sperm competition risk' treatments (2 and 3), a very strong effect was found only when the audience male could actually observe the focal male during mate choice in treatment (2). This suggests that focal males indeed attempt to conceal their mating preferences in the visual presence of other males so as to avoid mate choice copying. When there is no potential for eavesdropping [treatment (3)], non-specific specific sperm competition risk seems to play a minor or no role. Congruent with studies on other poeciliid species, our results also show that P. mexicana males respond to perceived specific sperm competition risk, and tend to share their mating effort more equally among females when the resource value of their previously preferred mate decreases (after mating with a rival male). However, this effect is comparatively weak.
Responding to inadequate awareness of the outstanding importance of biodiversity, the BioFrankfurt network was founded in 2004 in the State of Hesse, Germany. It is presented here as a case study and may serve as a model for other parts of the world, such as the Middle East. In 2007, only about 26% of the German population were familiar with the term “Biodiversity”, and most of them only had a vague idea about its meaning. The BioFrankfurt network of institutions addressed this problem, raising public awareness and supporting research, education and conservation. A regional biodiversity education program has been developed and delivered to more than 500 schools. Since 2007, an innovative public relations campaign combines raising awareness on regional biodiversity issues with activities to improve the public image of the Frankfurt area. Because of its geographical focus, the network’s activities gained the attention of local and regional politicians and other decision makers, culminating in the joint establishment of a new Biodiversity and Climate Research Centre by BioFrankfurt member institutions. The success of current activities attracts interesting partners, resulting in challenging cooperation initiatives. The authors are convinced that the network’s concepts and activities have a great potential to profoundly enhance the notion and acceptance of biodiversity issues elsewhere. Keywords: BioFrankfurt, biodiversity network, education, public awareness, scientifi c communication
Despite prevailing arid conditions, the diversity of terrestrial and freshwater biota in the Middle East is amazingly high and marine biodiversity is among the highest on Earth. Th roughout the Region, threats to the environment are moderate to severe. Despite the outstanding economic and ecological importance of biological diversity, the capacity in biodiversity-related research and academic education is inadequate. The "Middle Eastern Biodiversity Network" (MEBN), founded in 2006 by six universities and research institutes in Iran, Jordan, Germany, Lebanon and Yemen was designed to fi ll this gap. An integrated approach is taken to upgrade biodiversity research and education in order to improve regional ecosystem conservation and management capacities. A wide range of activities are carried out in the framework of the Network, including capacity building in biological collection management and professional natural history curatorship, developing university curricula in biodiversity, conducting scientifi c research, organising workshops and conferences on Middle Eastern biodiversity, and translating the results of biodiversity research into conservation and sustainable development. Keywords: Middle Eastern biodiversity, nature museums, biodiversity research, biodiversity education, biodiversity conservation, biodiversity networks
Background: The cosmopolitan moon jelly Aurelia is characterized by high degrees of morphological and ecological plasticity, and subsequently by an unclear taxonomic status. The latter has been revised repeatedly over the last century, dividing the genus Aurelia in as many as 12 or as little as two species. We used molecular data and phenotypic traits to unravel speciation processes and phylogeographic patterns in Aurelia.
Results: Mitochondrial and nuclear DNA data (16S and ITS-1/5.8S rDNA) from 66 world-wide sampled specimens reveal star-like tree topologies, unambiguously differentiating 7 (mtDNA) and 8 (ncDNA) genetic entities with sequence divergences ranging from 7.8 to 14% (mtDNA) and 5 to 32% (ncDNA), respectively. Phylogenetic patterns strongly suggest historic speciation events and the reconstruction of at least 7 different species within Aurelia. Both genetic divergences and life history traits showed associations to environmental factors, suggesting ecological differentiation forced by divergent selection. Hybridization and introgression between Aurelia lineages likely occurred due to secondary contacts, which, however, did not disrupt the unambiguousness of genetic separation.
Conclusions: Our findings recommend Aurelia as a model system for using the combined power of organismic, ecological, and molecular data to unravel speciation processes in cosmopolitan marine organisms.
© 2002 Schroth et al; licensee BioMed Central Ltd. Verbatim copying and redistribution of this article are permitted in any medium for any non-commercial purpose, provided this notice is preserved along with the article's original URL: http://www.biomedcentral.com/1471-2148/2/1
Background: The faunal and floral relationship of northward-drifting India with its neighboring continents is of general biogeographic interest as an important driver of regional biodiversity. However, direct biogeographic connectivity of India and Southeast Asia during the Cenozoic remains largely unexplored. We investigate timing, direction and mechanisms of faunal exchange between India and Southeast Asia, based on a molecular phylogeny, molecular clock-derived time estimates and biogeographic reconstructions of the Asian freshwater crab family Gecarcinucidae. Results: Although the Gecarcinucidae are not an element of an ancient Gondwana fauna, their subfamily Gecarcinucinae, and probably also the Liotelphusinae, evolved on the Indian Subcontinent and subsequently dispersed to Southeast Asia. Estimated by a model testing approach, this dispersal event took place during the Middle Eocene, and thus before the final collision of India and the Tibet-part of Eurasia. Conclusions: We postulate that the India and Southeast Asia were close enough for exchange of freshwater organisms during the Middle Eocene, before the final Indian--Eurasian collision. Our data support geological models that assume the Indian plate having tracked along Southeast Asia during its move northwards.
Large-scale genetic census of an elusive carnivore, the European wildcat (Felis s. silvestris)
(2016)
The European wildcat, Felis silvestris silvestris, serves as a prominent target species for the reconnection of central European forest habitats. Monitoring of this species, however, appears difficult due to its elusive behaviour and the ease of confusion with domestic cats. Recently, evidence for multiple wildcat occurrences outside its known distribution has accumulated in several areas across Central Europe, questioning the validity of available distribution data for this species. Our aim was to assess the fine-scale distribution and genetic status of the wildcat in its central European distribution range. We compiled and analysed genetic samples from roadkills and hundreds of recent hair-trapping surveys and applied phylogenetic and genetic clustering methods to discriminate wild and domestic cats and identify population subdivision. 2220 individuals were confirmed as either wildcat (n = 1792) or domestic cat (n = 342), and the remaining 86 (3.9 %) were identified as hybrids between the two. Remarkably, genetic distinction of domestic cats, wildcats and their hybrids was only possible when taking into account the presence of two highly distinct genetic lineages of wildcats, with a suture zone in central Germany. 44 % of the individual wildcats where sampled outside the previously published distribution. Our analyses confirm a relatively continuous spatial presence of wildcats across large parts of the study area in contrast to previous analyses indicating a highly fragmented distribution. Our results suggest that wildcat conservation and management should take advantage of the higher than previously assumed dispersal potential of wildcats, which may use wildlife corridors very efficiently.
Male reproductive biology can by characterized through competition over mates as well as mate choice. Multiple mating and male mate choice copying, especially in internally fertilizing species, set the stage for increased sperm competition, i.e., sperm of two or more males can compete for fertilization of the female’s ova. In the internally fertilizing fish Poecilia mexicana, males respond to the presence of rivals with reduced expression of mating preferences (audience effect), thereby lowering the risk of by-standing rivals copying their mate choice. Also, males interact initially more with a non-preferred female when observed by a rival, which has been interpreted in previous studies as a strategy to mislead rivals, again reducing sperm competition risk (SCR). Nevertheless, species might differ consistently in their expression of aggressive and reproductive behaviors, possibly due to varying levels of SCR. In the current study, we present a unique data set comprising ten poeciliid species (in two cases including multiple populations) and ask whether species can be characterized through consistent differences in the expression of aggression, sexual activity and changes in mate choice under increased SCR. We found consistent species-specific differences in aggressive behavior, sexual activity as well as in the level of misleading behavior, while decreased preference expression under increased SCR was a general feature of all but one species examined. Furthermore, mean sexual activity correlated positively with the occurrence of potentially misleading behavior. An alternative explanation for audience effects would be that males attempt to avoid aggressive encounters, which would predict stronger audience effects in more aggressive species. We demonstrate a positive correlation between mean aggressiveness and sexual activity (suggesting a hormonal link as a mechanistic explanation), but did not detect a correlation between aggressiveness and audience effects. Suites of correlated behavioral tendencies are termed behavioral syndromes, and our present study provides correlational evidence for the evolutionary significance of SCR in shaping a behavioral syndrome at the species level across poeciliid taxa.
Mate choice in many species is sensitive to social cues from neighboring individuals; for example, animals can copy mate choice decisions. If males copy other males’ choices, sperm of two or more males can compete for fertilization of the female’s ova. In the internally fertilizing fish Poecilia mexicana, males respond to the presence of rivals with reduced expression of mating preferences (audience effect), thereby lowering the risk of by-standing rivals copying their mate choice. Also, males interact initially more with a non-preferred female when observed by a rival, which has been interpreted in previous studies as a strategy to mislead rivals, again reducing sperm competition risk (SCR). Using a comparative approach, we tested the hypothesis that SCR is indeed a driving force explaining the occurrence of audience-induced changes in poeciliid male mate choice behavior. If this were true, then males of species with higher overall sexual activity — and, thus, higher potential for multiple mating — should show stronger audience effects. We investigated ten poeciliid species (in two cases including multiple populations) and found support for our hypothesis as mean sexual activity correlated positively with the occurrence of potentially deceptive behavior. An alternative explanation for audience effects would be that males attempt to avoid aggressive encounters, which would predict stronger audience effects in more aggressive species, and so we also characterized the examined species for aggressiveness using staged contests of size-matched males. We demonstrate a positive correlation between mean aggressiveness and sexual activity (suggesting a hormonal link as a mechanistic explanation), but we detected no correlation between aggressiveness and audience effects. Suites of correlated behavioral tendencies are termed behavioral syndromes, and our present study provides correlational evidence for the evolutionary significance of SCR in shaping a behavioral syndrome at the species level across poeciliid taxa.
Male reproductive biology can by characterized through competition over mates as well as mate choice. Multiple mating and male mate choice copying, especially in internally fertilizing species, set the stage for increased sperm competition, i.e., sperm of two or more males can compete for fertilization of the female’s ova. In the internally fertilizing fish Poecilia mexicana, males respond to the presence of rivals with reduced expression of mating preferences (audience effect), thereby lowering the risk of by-standing rivals copying their mate choice. Also, males interact initially more with a non-preferred female when observed by a rival, which has been interpreted in previous studies as a strategy to mislead rivals, again reducing sperm competition risk (SCR). Nevertheless, species might differ consistently in their expression of aggressive and reproductive behaviors, possibly due to varying levels of SCR. In the current study, we present a unique data set comprising ten poeciliid species (in two cases including multiple populations) and ask whether species can be characterized through consistent differences in the expression of aggression, sexual activity and changes in mate choice under increased SCR. We found consistent species-specific differences in aggressive behavior, sexual activity as well as in the level of misleading behavior, while decreased preference expression under increased SCR was a general feature of all but one species examined. Furthermore, mean sexual activity correlated positively with the occurrence of potentially misleading behavior. An alternative explanation for audience effects would be that males attempt to avoid aggressive encounters, which would predict stronger audience effects in more aggressive species. We demonstrate a positive correlation between mean aggressiveness and sexual activity (suggesting a hormonal link as a mechanistic explanation), but did not detect a correlation between aggressiveness and audience effects. Suites of correlated behavioral tendencies are termed behavioral syndromes, and our present study provides correlational evidence for the evolutionary significance of SCR in shaping a behavioral syndrome at the species level across poeciliid taxa
During field work along a transect in the Cordillera Central of western Panama between 2008 and 2010, we detected several populations of amphibian species which are considered as “Endangered” or “Critically Endangered” by the IUCN. Some of these species had suffered from serious population declines, probably due to chytridiomycosis, but all are generally threatened by habitat loss. We detected 53% of the Endangered and 56% of the Critically Endangered amphibian species that have previously been reported from within the investigated area. We report on findings of species that have not been found in Panama for many years, and provide locality data of newly discovered populations. There is a need to create a new protected area in the Cerro Colorado area of the Serranía de Tabasará, where we found 15% of the Endangered and Critically Endangered amphibian species known to Panama.
Introduction : extent, processes and evolutionary impact of interspecific hybridization in animals
(2008)
Since the time of Charles Darwin, studies of interspecific hybridization have been a major focus for evolutionary biologists. Although this phenomenon has often been viewed as problematic in the fields of ecology, taxonomy and systematics, it has become a primary source of data for studies on speciation and adaptation. Effects from genetic/evolutionary processes, such as recombination and natural selection, usually develop over extended periods of time; however, they are accelerated in cases of hybridization. Interspecific hybrids exhibit novel genomes that are exposed to natural selection, thus providing a key to unravel the ultimate causes of adaptation and speciation. Here we provide firstly a historic perspective of hybridization research, secondly a novel attempt to assess the extent of hybridization among animals and thirdly an overview of the reviews and case studies presented in this theme issue.
Resting egg banks of microcrustaceans have been used to reconstruct the evolutionary and ecological history of species. However, recent studies provided evidence for a discrepancy between dormant propagules in the sediment and the planktonic population. This pattern raises two questions: First, what is the value of data on resting egg banks for population dynamics over time and second, which component of the reproductive cycle causes the observed inconsistency? In our study we focussed on the second question by comparing the taxon composition of a resting egg bank with the reproductive success of ex-ephippial hatchlings. Species and interspecific hybrid identification of dormant and hatched stages was achieved through the application of restriction fragment length polymorphism analysis of an internal transcribed spacer region. We found no significant deviation between the proportion of hatched Daphnia galeata, D. galeata x hyalina and D. hyalina individuals and the observed taxon composition of the resting egg bank. However, species and hybrids differed in their mode and relative success of reproduction. We conclude that the components of reproductive success in Daphnia contribute differentially to the fitness of species and interspecific hybrids. The discrepancy between resting egg banks and "active" planktonic populations results not from differential hatching of species but from the reproductive success of ex-ephippial females and the timing and frequency of sexual reproduction of the different taxa.
Background: One aspect of premating isolation between diverging, locally-adapted population pairs is female mate choice for resident over alien male phenotypes. Mating preferences often show considerable individual variation, and whether or not certain individuals are more likely to contribute to population interbreeding remains to be studied. In the Poecilia mexicana-species complex different ecotypes have adapted to hydrogen sulfide (H2S)-toxic springs, and females from adjacent non-sulfidic habitats prefer resident over sulfide-adapted males. We asked if consistent individual differences in behavioral tendencies (animal personality) predict the strength and direction of the mate choice component of premating isolation in this system.
Results: We characterized focal females for their personality and found behavioral measures of ‘novel object exploration’, ‘boldness’ and ‘activity in an unknown area’ to be highly repeatable. Furthermore, the interaction term between our measures of exploration and boldness affected focal females’ strength of preference (SOP) for the resident male phenotype in dichotomous association preference tests. High exploration tendencies were coupled with stronger SOPs for resident over alien mating partners in bold, but not shy, females. Shy and/or little explorative females had an increased likelihood of preferring the non-resident phenotype and thus, are more likely to contribute to rare population hybridization. When we offered large vs. small conspecific stimulus males instead, less explorative females showed stronger preferences for large male body size. However, this effect disappeared when the size difference between the stimulus males was small.
Conclusions: Our results suggest that personality affects female mate choice in a very nuanced fashion. Hence, population differences in the distribution of personality types could be facilitating or impeding reproductive isolation between diverging populations depending on the study system and the male trait(s) upon which females base their mating decisions, respectively.
From sea to land and beyond : new insights into the evolution of euthyneuran Gastropoda (Mollusca)
(2008)
Background The Euthyneura are considered to be the most successful and diverse group of Gastropoda. Phylogenetically, they are riven with controversy. Previous morphology-based phylogenetic studies have been greatly hampered by rampant parallelism in morphological characters or by incomplete taxon sampling. Based on sequences of nuclear 18S rRNA and 28S rRNA as well as mitochondrial 16S rRNA and COI DNA from 56 taxa, we reconstructed the phylogeny of Euthyneura utilising Maximum Likelihood and Bayesian inference methods. The evolution of colonization of freshwater and terrestrial habitats by pulmonate Euthyneura, considered crucial in the evolution of this group of Gastropoda, is reconstructed with Bayesian approaches. Results We found several well supported clades within Euthyneura, however, we could not confirm the traditional classification, since Pulmonata are paraphyletic and Opistobranchia are either polyphyletic or paraphyletic with several clades clearly distinguishable. Sacoglossa appear separately from the rest of the Opisthobranchia as sister taxon to basal Pulmonata. Within Pulmonata, Basommatophora are paraphyletic and Hygrophila and Eupulmonata form monophyletic clades. Pyramidelloidea are placed within Euthyneura rendering the Euthyneura paraphyletic. Conclusion Based on the current phylogeny, it can be proposed for the first time that invasion of freshwater by Pulmonata is a unique evolutionary event and has taken place directly from the marine environment via an aquatic pathway. The origin of colonisation of terrestrial habitats is seeded in marginal zones and has probably occurred via estuaries or semi-terrestrial habitats such as mangroves.
Ohne das Eingreifen des Menschen wäre Mitteleuropa fast ein reines Waldgebiet. Noch heute beheimaten die Wälder eine große Vielfalt an Pflanzen und Tieren, die für diese Region spezifisch sind. Regionale Besonderheiten gehen aber verloren, je mehr Menschen in die Ökosysteme eingreifen: So unterscheiden sich die Pflanzenarten auf der North Charles Street in Baltimore nur wenig von denjenigen der Mainzer Landstraße in Frankfurt. Gleichzeitig verdrängen zugewanderte und eingeschleppte Arten heimische Tiere und Pflanzen. Allerdings gibt es auch im Frankfurter Stadtgebiet echte Horte der Biodiversität.
Background Reliable taxonomic identification at the species level is the basis for many biological disciplines. In order to distinguish species, it is necessary that taxonomic characters allow for the separation of individuals into recognisable, homogeneous groups that differ from other such groups in a consistent way. We compared here the suitability and efficacy of traditionally used shell morphology and DNA-based methods to distinguish among species of the freshwater snail genus Radix (Basommatophora, Pulmonata). Results Morphometric analysis showed that shell shape was unsuitable to define homogeneous, recognisable entities, because the variation was continuous. On the other hand, the Molecularly defined Operational Taxonomic Units (MOTU), inferred from mitochondrial COI sequence variation, proved to be congruent with biological species, inferred from geographic distribution patterns, congruence with nuclear markers and crossing experiments. Moreover, it could be shown that the phenotypically plastic shell variation is mostly determined by the environmental conditions experienced. Conclusion Contrary to DNA-taxonomy, shell morphology was not suitable for delimiting and recognising species in Radix. As the situation encountered here seems to be widespread in invertebrates, we propose DNA-taxonomy as a reliable, comparable, and objective means for species identification in biological research.
Population structure was estimated in a continuous population of a small land snail (Trochoidea geyeri). Mark-recapture experiments and randomly amplified polymorphic DNA analyses indicate that the population structure can be described by the isolation by distance model of Wright (1946). Estimates of density and dispersal suggest a neighbourhood size of 70-208 individuals on an area of 13-21 m². A principal component analysis of the randomly amplified polymorphic DNA data reveals clinal variation of genetic composition across the population, as predicted by the neighbourhood concept. An analysis of molecular variance indicates substantial genetic structuring. Comparisons of the genetic distances, expressed as euclidean distances among individuals, versus the geographic distance between sampling sites yield a highly significant positive correlation (Mantel test: r = 0.567, p<0.0001). The revealed pattern of populational subdivision on a microgeographic scale seems to be one of the principal processes generating and maintaining genetic diversity within populations of small land gastropods.
In dem Entwurf einer European Strategy on Invasive Alien Species T-PVS (2002) 8 werden verstärkte Forschungsaktivitäten der Mitgliedstaaten angeregt, die nicht nur auf den biologischen Bereich oder Bekämpfung invasiver Arten beschränkt bleiben, sondern auch die Bewertung der Auswirkungen auf Gesundheitswesen und Volkswirtschaft untersuchen sollen. Derartige Studien wurden bisher nur für die Vereinigten Staaten von Amerika oder mit eher regionalen Charakter durchgeführt. Aus diesem Grunde wurden 20 Tiere und Pflanzen aus verschiedenen Problemgebieten (Gesundheitsgefährdende Arten, Schäden in Forst-, Land-, und Fischereiwirtschaft, im kommunalen Bereich, an aquatischen und terrestrischen Verkehrswegen sowie Kosten von Arten, die einheimische Spezies gefährden oder in der Empfehlung 77 der Berner Konvention aufgeführt sind) ausgewählt und beispielhaft für das Gebiet Deutschlands bearbeitet. Die entstehenden Kosten wurden in drei Kategorien aufgeschlüsselt: a) direkte ökonomische Schäden, beispielsweise durch Vorratsschädlinge, b) ökologische Schäden, verursacht durch Pflege und Schutz gefährdeter heimischer Arten, Biozönosen oder Ökosysteme und c) Kosten für Maßnahmen zur Bekämpfung invasiver Arten. Es zeigte sich, dass auf Grund der Datenlage sowie der unterschiedlichen Biologie und Ökologie der invasiven Arten jeweils individuelle Ansätze notwendig waren. Die hier ermittelten Kosten unterscheiden sich stark von Art zu Art. Nicht alle untersuchten Arten verursachen ökonomische Schäden. Eine differenzierte Betrachtung von Neobiota ist nach dem Prinzip der Einzelfallbewertung erforderlich. Die Monetisierung von ökologischen Schäden gelang hierbei nur in wenigen Fällen. Weitergehende, mehrjährige Studien sollten willingness to pay-Analysen einbeziehen, um offen gebliebene Fragen zu beantworten.
The European Strategy on Invasive Alien Species T-PWS(2002) 8 mandates intensified research by member nations on invasive species. This research will not be restricted solely to the biology and remediation of invasive species, but will also evaluate their adverse health effects and economic impact. Previous studies of these issues have only been carried out in the Unites States of America, or in a limited, regional manner. Consequently, 20 plant and animal species from various problem areas (species which pose a threat to public health; losses to agriculture, fisheries, and forestry; damage to public roads and waterways; costs associated with the protection of native species threatened by non-native species as mandated by Recommendation 77 of the Bern Convention were assessed in Germany nation-wide. The accruing costs were sorted into 3 categories: a) direct economic losses, such as those caused by destructive pest species; b) ecological costs, in the form of extra care and protection of native taxa, biotopes, or ecosystems threatened by invasive species; c) costs of measures to combat invasive species. Because of the nature of available data, as well as the different biology and ecology of the invasive species, each had to be treated individually, and the associated costs vary greatly from species to species. Moreover, not all of the species investigated cause economic losses. Accordingly, a nuanced approach to alien species is essential. Cost assessment of losses deriving from ecological damage was only possible in a few cases. Ongoing, multi-year studies incorporating cost/benefit analysis will be necessary to resolve remaining issues.
Bipolar disorder (BD) is a genetically complex mental illness characterized by severe oscillations of mood and behavior. Genome-wide association studies (GWAS) have identified several risk loci that together account for a small portion of the heritability. To identify additional risk loci, we performed a two-stage meta-analysis of >9 million genetic variants in 9,784 bipolar disorder patients and 30,471 controls, the largest GWAS of BD to date. In this study, to increase power we used ~2,000 lithium-treated cases with a long-term diagnosis of BD from the Consortium on Lithium Genetics, excess controls, and analytic methods optimized for markers on the Xchromosome. In addition to four known loci, results revealed genome-wide significant associations at two novel loci: an intergenic region on 9p21.3 (rs12553324, p = 5.87×10-9; odds ratio = 1.12) and markers within ERBB2 (rs2517959, p = 4.53×10-9; odds ratio = 1.13). No significant X-chromosome associations were detected and X-linked markers explained very little BD heritability. The results add to a growing list of common autosomal variants involved in BD and illustrate the power of comparing well-characterized cases to an excess of controls in GWAS.