| 1. |
- Ericson, Per G P, 1956-, et al.
(författare)
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Dating the diversification of the major lineages of Passeriformes (Aves)
- 2014
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Ingår i: BMC Evolutionary Biology. - : Springer Science and Business Media LLC. - 1471-2148. ; 14:8, s. 1-15
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Tidskriftsartikel (refereegranskat)abstract
- Background: The avian Order Passeriformes is an enormously species-rich group, which comprises almost 60% ofall living bird species. This diverse order is believed to have originated before the break-up of Gondwana in the lateCretaceous. However, previous molecular dating studies have relied heavily on the geological split between NewZealand and Antarctica, assumed to have occurred 85–82 Mya, for calibrating the molecular clock and might thusbe circular in their argument.Results: This study provides a time-scale for the evolution of the major clades of passerines using seven nuclearmarkers, five taxonomically well-determined passerine fossils, and an updated interpretation of the New Zealandsplit from Antarctica 85–52 Mya in a Bayesian relaxed-clock approach. We also assess how different interpretationsof the New Zealand–Antarctica vicariance event influence our age estimates. Our results suggest that thediversification of Passeriformes began in the late Cretaceous or early Cenozoic. Removing the root calibration forthe New Zealand–Antarctica vicariance event (85–52 Mya) dramatically increases the 95% credibility intervals andleads to unrealistically old age estimates. We assess the individual characteristics of the seven nuclear genesanalyzed in our study. Our analyses provide estimates of divergence times for the major groups of passerines,which can be used as secondary calibration points in future molecular studies.Conclusions: Our analysis takes recent paleontological and geological findings into account and provides the bestestimate of the passerine evolutionary time-scale currently available. This time-scale provides a temporalframework for further biogeographical, ecological, and co-evolutionary studies of the largest bird radiation, andadds to the growing support for a Cretaceous origin of Passeriformes.
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| 2. |
- Malmström, Helena, et al.
(författare)
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High frequency of lactose intolerance in a prehistoric hunter-gatherer population in northern Europe
- 2010
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Ingår i: BMC Evolutionary Biology. - : Springer Science and Business Media LLC. - 1471-2148. ; 10, s. 89-
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Tidskriftsartikel (refereegranskat)abstract
- Background: Genes and culture are believed to interact, but it has been difficult to find direct evidence for the process. One candidate example that has been put forward is lactase persistence in adulthood, i.e. the ability to continue digesting the milk sugar lactose after childhood, facilitating the consumption of raw milk. This genetic trait is believed to have evolved within a short time period and to be related with the emergence of sedentary agriculture. Results: Here we investigate the frequency of an allele (-13910*T) associated with lactase persistence in a Neolithic Scandinavian population. From the 14 individuals originally examined, 10 yielded reliable results. We find that the T allele frequency was very low (5%) in this Middle Neolithic hunter-gatherer population, and that the frequency is dramatically different from the extant Swedish population (74%). Conclusions: We conclude that this difference in frequency could not have arisen by genetic drift and is either due to selection or, more likely, replacement of hunter-gatherer populations by sedentary agriculturalists.
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| 3. |
- Bilde, Trine, et al.
(författare)
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Sex differences in the genetic architecture of lifespan in a seed beetle : extreme inbreeding extends male lifespan
- 2009
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Ingår i: BMC Evolutionary Biology. - : Springer Science and Business Media LLC. - 1471-2148. ; 9, s. 33-
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Tidskriftsartikel (refereegranskat)abstract
- Background: Sex differences in lifespan are ubiquitous throughout the animal kingdom but the causes underlying this phenomenon remain poorly understood. Several explanations based on asymmetrical inheritance patterns (sex chromosomes or mitochondrial DNA) have been proposed, but these ideas have rarely been tested experimentally. Alternatively, sexual dimorphism in lifespan could result from sex-specific selection, caused by fundamental differences in how males and females optimize their fitness by allocating resources into current and future reproduction. Results: Here we used sex-specific responses to inbreeding to study the genetic architecture of lifespan and mortality rates in Callosobruchus maculatus, a seed beetle that shows sexual dimorphism in lifespan. Two independent assays revealed opposing sex-specific responses to inbreeding. The combined data set showed that inbred males live longer than outbred males, while females show the opposite pattern. Both sexes suffered reduced fitness measured as lifetime reproductive success as a result of inbreeding. Conclusion: No model based on asymmetrical inheritance can explain increased male lifespan in response to inbreeding. Our results are however compatible with models based on sex-specific selection on reproductive strategies. We therefore suggest that sex-specific differences in lifespan in this species primarily result from sexually divergent selection.
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| 4. |
- Bilde, T., et al.
(författare)
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The genetic architecture of fitness in a seed beetle : assessing the potential for indirect genetic benefits of female choice
- 2008
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Ingår i: BMC Evolutionary Biology. - : Springer Science and Business Media LLC. - 1471-2148. ; 8, s. 295-
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Tidskriftsartikel (refereegranskat)abstract
- Background: Quantifying the amount of standing genetic variation in fitness represents an empirical challenge. Unfortunately, the shortage of detailed studies of the genetic architecture of fitness has hampered progress in several domains of evolutionary biology. One such area is the study of sexual selection. In particular, the evolution of adaptive female choice by indirect genetic benefits relies on the presence of genetic variation for fitness. Female choice by genetic benefits fall broadly into good genes (additive) models and compatibility (non-additive) models where the strength of selection is dictated by the genetic architecture of fitness. To characterize the genetic architecture of fitness, we employed a quantitative genetic design (the diallel cross) in a population of the seed beetle Callosobruchus maculatus, which is known to exhibit post-copulatory female choice. From reciprocal crosses of inbred lines, we assayed egg production, egg-to-adult survival, and lifetime offspring production of the outbred F1 daughters (F1 productivity). Results: We used the bio model to estimate six components of genetic and environmental variance in fitness. We found sizeable additive and non-additive genetic variance in F-1 productivity, but lower genetic variance in egg-to-adult survival, which was strongly influenced by maternal and paternal effects. Conclusion: Our results show that, in order to gain a relevant understanding of the genetic architecture of fitness, measures of offspring fitness should be inclusive and should include quantifications of offspring reproductive success. We note that our estimate of additive genetic variance in F-1 productivity (CVA = 14%) is sufficient to generate indirect selection on female choice. However, our results also show that the major determinant of offspring fitness is the genetic interaction between parental genomes, as indicated by large amounts of non-additive genetic variance (dominance and/or epistasis) for F-1 productivity. We discuss the processes that may maintain additive and non-additive genetic variance for fitness and how these relate to indirect selection for female choice.
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| 5. |
- Malmström, Helena, et al.
(författare)
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Barking up the wrong tree : Modern northern European dogs fail to explain their origin
- 2008
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Ingår i: BMC Evolutionary Biology. - : Springer Science and Business Media LLC. - 1471-2148. ; 8
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Tidskriftsartikel (refereegranskat)abstract
- Background: Geographic distribution of the genetic diversity in domestic animals, particularly mitochondrial DNA, has often been used to infer centers of domestication. The underlying presumption is that phylogeographic patterns among domesticates were established during, or shortly after the domestication. Human activities are assumed not to have altered the haplogroup frequencies to any great extent. We studied this hypothesis by analyzing 24 mtDNA sequences in ancient Scandinavian dogs. Breeds originating in northern Europe are characterized by having a high frequency of mtDNA sequences belonging to a haplogroup rare in other populations (HgD). This has been suggested to indicate a possible origin of the haplogroup (perhaps even a separate domestication) in central or northern Europe. Results: The sequences observed in the ancient samples do not include the haplogroup indicative for northern European breeds (HgD). Instead, several of them correspond to haplogroups that are uncommon in the region today and that are supposed to have Asian origin. Conclusion: We find no evidence for local domestication. We conclude that interpretation of the processes responsible for current domestic haplogroup frequencies should be carried out with caution if based only on contemporary data. They do not only tell their own story, but also that of humans.
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