Evolutionary Biology Center


Evolutionary Biology Center

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Valcarcel V.,Autonomous University of Madrid | Fiz-Palacios O.,Evolutionary Biology Center | Wen J.,Smithsonian Institution
Molecular Phylogenetics and Evolution | Year: 2014

The Asian Palmate group is one of the four major clades of the family Araliaceae that is formed by 18 genera, including ivies (Hedera L.). The Mediterranean diversity centre and temperate affinity of ivies contrast with the inferred Asian centre of diversity of the primarily tropical and subtropical Asian Palmate group. We herein investigated the sister-group relationships of Hedera to reconstruct the evolutionary context for its origin and early diversification. Seven nuclear and plastid DNA regions were analyzed in 61 Araliaceae samples including all the 18 Asian Palmate genera. Maximum Parsimony, Maximum Likelihood and Bayesian Inference were run together with a battery of topology testing analyses constraining the expected Hedera's sister-group relationships. Additionally, Bayesian polytomy resolvability and divergence time analyses were also conducted. Genome incongruence and hard nuclear and plastid basal polytomies are detected for the Asian Palmate group where the lineage of Hedera is placed. Topology testing analyses do not allow rejecting any of the tentative sisters of Hedera. An early radiation with inter-lineage hybridization and genome doubling is suggested for the Asian Palmate group where all the seven temperate genera, including Hedera, seem to have played an important role. The radiation took placed during the Upper Cretaceous in Asia under a general cooling and the eastern Asian mountain uplift that produced new temperate environments and promoted lineage connections. This allows us to hypothesize that the origin of the Hedera lineage may fit in a temperate niche conservatism scenario where the combination of the radiation with lineage admixtures prevents us from discovering its sister-group. © 2013 Elsevier Inc.

Fiz-Palacios O.,Evolutionary Biology Center | Valcarcel V.,Autonomous University of Madrid
Perspectives in Plant Ecology, Evolution and Systematics | Year: 2013

Paleobotanical and molecular studies link diversification of plants in the Mediterranean Basin with the onset of the Mediterranean climate. Screening diversification before this period is needed in order to analyze whether the observed increase in diversification is a legitimate footprint denoting radiation or instead the biological signal of a previous mass extinction or rate stasis period. A shared post-Messinian temporal gap of cladogenesis has been previously observed in two Mediterranean sister genera. Based on this evidence we explored recently published molecular studies to recover lineages with similar diversification profiles exhibiting a cladogenesis gap. Using this criterion, we conducted a meta-analysis of 36 Mediterranean plant lineages with a post-Messinian temporal gap of cladogenesis, including a new molecular dating of Genista (Fabaceae). Whereas 39% of these lineages have not diversified since the Miocene, another 39% began to rediversify during the onset of the Mediterranean climate and the remaining 22% began diversifying again afterwards during the Quaternary. The pattern of Mediterranean diversification recovery after a temporal gap of cladogenesis was also obtained with phylogenetic tree simulations under birth and death processes when forcing one or two temporal shifts in diversification rates. The relative importance of the Mediterranean onset as a driving force promoting speciation or triggering extinction remains as an open question, since neither the mass extinction nor the rate stasis evolutionary scenarios can be rule out. The independent analysis of individual clades within phylogenies is also essential to detect clade-dependent patterns hidden by phylogeny-level ones. We disclose the importance of analyzing diversification patterns of Mediterranean lineages since the Miocene to understand the recent history of the Mediterranean biota. © 2013 Perspectives in Plant Ecology, Evolution and Systematics.

Kohler S.J.,Swedish University of Agricultural Sciences | Kothawala D.,Evolutionary Biology Center | Futter M.N.,Swedish University of Agricultural Sciences | Liungman O.,Sydney Water | Tranvik L.,Evolutionary Biology Center
PLoS ONE | Year: 2013

Increased color in surface waters, or browning, can alter lake ecological function, lake thermal stratification and pose difficulties for drinking water treatment. Mechanisms suggested to cause browning include increased dissolved organic carbon (DOC) and iron concentrations, as well as a shift to more colored DOC. While browning of surface waters is widespread and well documented, little is known about why some lakes resist it. Here, we present a comprehensive study of Mälaren, the third largest lake in Sweden. In Mälaren, the vast majority of water and DOC enters a western lake basin, and after approximately 2.8 years, drains from an eastern basin. Despite 40 years of increased terrestrial inputs of colored substances to western lake basins, the eastern basin has resisted browning over this time period. Here we find the half-life of iron was far shorter (0.6 years) than colored organic matter (A420; 1.7 years) and DOC as a whole (6.1 years). We found changes in filtered iron concentrations relate strongly to the observed loss of color in the western basins. In addition, we observed a substantial shift from colored DOC of terrestrial origin, to less colored autochthonous sources, with a substantial decrease in aromaticity (-17%) across the lake. We suggest that rapid losses of iron and colored DOC caused the limited browning observed in eastern lake basins. Across a wider dataset of 69 Swedish lakes, we observed greatest browning in acidic lakes with shorter retention times (< 1.5 years). These findings suggest that water residence time, along with iron, pH and colored DOC may be of central importance when modeling and projecting changes in brownification on broader spatial scales. © 2013 Köhler et al.

Friberg M.,University of Stockholm | Friberg M.,Evolutionary Biology Center | Leimar O.,University of Stockholm | Wiklund C.,University of Stockholm
Journal of Evolutionary Biology | Year: 2013

Species interacting in varied ecological conditions often evolve in different directions in different local populations. The butterflies of the cryptic Leptidea complex are sympatrically distributed in different combinations across their Eurasian range. Interestingly, the same species is a habitat generalist in some regions and a habitat specialist in others, where a sibling species has the habitat generalist role. Previous studies suggest that this geographically variable niche divergence is generated by local processes in different contact zones. By varying the absolute and relative densities of Leptidea sinapis and Leptidea juvernica in large outdoor cages, we show that female mating success is unaffected by conspecific density, but strongly negatively affected by the density of the other species. Whereas 80% of the females mated when a conspecific couple was alone in a cage, less than 10% mated when the single couple shared the cage with five pairs of the other species. The heterospecific courtships can thus affect the population fitness, and for the species in the local minority, the suitability of a habitat is likely to depend on the presence or absence of the locally interacting species. If the local relative abundance of the different species depends on the colonization order, priority effects might determine the ecological roles of interacting species in this system. © 2013 The Authors. © 2013 European Society For Evolutionary Biology.

Fiz-Palacios O.,Evolutionary Biology Center
PloS one | Year: 2013

Evolution of lineage diversification through time is an active area of research where much progress has been made in the last decade. Contrary to the situation in animals and plants little is known about how diversification rates have evolved in most major groups of protist. This is mainly due to uncertainty about phylogenetic relationships, scarcity of the protist fossil record and the unknown diversity within these lineages. We have analyzed the evolutionary history of the supergroup Amoebozoa over the last 1000 million years using molecular dating and species number estimates. After an origin in the marine environment we have dated the colonization of terrestrial habitats by three distinct lineages of Amoebozoa: Dictyostelia, Myxogastria and Arcellinida. The common ancestor of the two sister taxa, Dictyostelia and Myxogastria, appears to have existed before the colonization of land by plants. In contrast Arcellinida seems to have diversify in synchrony with land plant radiation, and more specifically with that of mosses. Detection of acceleration of diversification rates in Myxogastria and Arcellinida points to a co-evolution within the terrestrial habitats, where land plants and the amoebozoans may have interacted during the evolution of these new ecosystems.

Bernander R.,Evolutionary Biology Center | Ettema T.J.G.,Evolutionary Biology Center
Current Opinion in Microbiology | Year: 2010

A dedicated cell division machinery is needed for efficient proliferation of an organism. The eukaryotic actin-myosin based mechanism and the bacterial FtsZ-dependent machinery have both been characterized in detail, and a third division mechanism, the Cdv system, was recently discovered in archaea from the Crenarchaeota phylum. Despite these findings, division mechanisms remain to be identified in, for example, organisms belonging to the bacterial PVC superphylum, bacteria with extremely reduced genomes, wall-less archaea and bacteria, and in archaea that carry out the division process without cell constriction. Cytokinesis mechanisms in these clades and individual taxa are likely to include adaptation of host functions to division of bacterial symbionts, transfer of bacterial division genes into the host genome, vesicle formation without a dedicated constriction machinery, cross-wall formation without invagination, as well as entirely novel division mechanisms. © 2010 Elsevier Ltd.

Morrison D.A.,Evolutionary Biology Center
Evolutionary Biology | Year: 2016

Pedigrees illustrate the genealogical relationships among individuals, and phylogenies do the same for groups of organisms (such as species, genera, etc.). Here, I provide a brief survey of current concepts and methods for calculating and displaying genealogical relationships. These relationships have long been recognized to be reticulating, rather than strictly divergent, and so both pedigrees and phylogenies are correctly treated as networks rather than trees. However, currently most pedigrees are instead presented as “family trees”, and most phylogenies are presented as phylogenetic trees. Nevertheless, the historical development of concepts shows that networks pre-dated trees in most fields of biology, including the study of pedigrees, biology theory, and biology practice, as well as in historical linguistics in the social sciences. Trees were actually introduced in order to provide a simpler conceptual model for historical relationships, since trees are a specific type of simple network. Computationally, trees and networks are a part of graph theory, consisting of nodes connected by edges. In this mathematical context they differ solely in the absence or presence of reticulation nodes, respectively. There are two types of graphs that can be called phylogenetic networks: (1) rooted evolutionary networks, and (2) unrooted affinity networks. There are quite a few computational methods for unrooted networks, which have two main roles in phylogenetics: (a) they act as a generic form of multivariate data display; and (b) they are used specifically to represent haplotype networks. Evolutionary networks are more difficult to infer and analyse, as there is no mathematical algorithm for reconstructing unique historical events. There is thus currently no coherent analytical framework for computing such networks. © 2016 Springer Science+Business Media New York

Griffin R.M.,Evolutionary Biology Center | Dean R.,Evolutionary Biology Center | Grace J.L.,Evolutionary Biology Center | Ryden P.,Umeå University | Friberg U.,Evolutionary Biology Center
Molecular Biology and Evolution | Year: 2013

Males and females share most of their genomes, and differences between the sexes can therefore not evolve through sequence divergence in protein coding genes. Sexual dimorphism is instead restricted to occur through sex-specific expression and splicing of gene products. Evolution of sexual dimorphism through these mechanisms should, however, also be constrained when the sexes share the genetic architecture for regulation of gene expression. Despite these obstacles, sexual dimorphism is prevalent in the animal kingdom and commonly evolves rapidly. Here, we ask whether the genetic architecture of gene expression is plastic and easily molded by sex-specific selection, or if sexual dimorphism evolves rapidly despite pervasive genetic constraint. To address this question, we explore the relationship between the intersexual genetic correlation for gene expression (rMF), which captures how independently genes are regulated in the sexes, and the evolution of sex-biased gene expression. Using transcriptome data from Drosophila melanogaster, we find that most genes have a high rMF and that genes currently exposed to sexually antagonistic selection have a higher average rMF than other genes. We further show that genes with a high rMF have less pronounced sex-biased gene expression than genes with a low rMF within D. melanogaster and that the strength of the rMF in D. melanogaster predicts the degree to which the sex bias of a gene's expression has changed between D. melanogaster and six other species in the Drosophila genus. In sum, our results show that a shared genome constrains both short-and long-term evolution of sexual dimorphism. © 2013 The Author.

Stone R.D.,University of KwaZulu - Natal | Andreasen K.,Evolutionary Biology Center
Taxon | Year: 2010

Warneckea consists of shrubs and small trees endemic to tropical forests in Africa, Madagascar, and Mauritius. Phylogenetic analyses of sequence data from the transcribed spacers of nuclear ribosomal DNA (ETS, ITS) indicate that W. sect. Carnosa Jacq.-Fél. (1 sp., East Africa and Madagascar) is a divergent element that is best treated at subgeneric level. The analyses recovered three major lineages in W. subg. Warneckea, together forming a basal trichotomy. The three lineages represent W. sect. Strychnoidea (western and central Africa), sect. Warneckea (East Africa, Madagascar, Mauritius), and a third group with three West African species (W. fascicularis, W. guineensis, W. mangrovensis) comprising the newly proposed W. sect. Guineensea.

Ellegren H.,Evolutionary Biology Center
Trends in Ecology and Evolution | Year: 2010

Evolution at the molecular level is manifested in a variety of types of change in DNA sequences, including changes in the structure and organisation of chromosomes. However, in birds chromosomal evolution occurs at an unusually slow rate and recent whole-genome comparisons have shown that many chromosomes have remained more or less intact during avian evolution. Here I discuss progress in the development of genetic maps of natural bird populations, which has revealed that the evolutionary stasis of chromosomes often extends to conservation of gene order. The evolutionary stability of bird chromosomes, which might relate to a low frequency of transposable elements, will facilitate the transfer of genomic information from model to non-model organisms and might have a connection to the rarity of postzygotic incompatibilities observed in birds. © 2010.

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