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Morales et al. test predictions of adaptive radiation theory and phenotypic convergence in Myotis bats using genomic target capture and a morphological dataset that represents 80% of the species described for this genus. The authors demonstrate that ecomorphological convergence has occurred multiple times throughout the history of Myotis, despite finding no diversification rate shifts associated with...
Sex is determined by chromosomes in mammals but it can be influenced by the environment in many worms, crustaceans, and vertebrates. Despite this, there is little understanding of the relationship between ecology and the evolution of sexual systems. The nematode Auanema freiburgensis has a unique sex determination system in which individuals carrying one X chromosome develop into males while XX individuals...
Outcrossing is maintained in many hermaphroditic species despite theoretical work suggesting that alleles increasing selfing should invade outcrossing populations. Brown and Kelly (2019) identify reasons why this may not have occurred in an outcrossing population of monkeyflower, namely that inbreeding depression causes strong reductions in fitness, resulting in selection for the maintenance of outcrossing...
Understanding how selective forces influence patterns of symmetry remains an active area of research in evolutionary biology. One hypothesis, which has received relatively little attention, suggests that the functional importance of morphological characters may influence patterns of symmetry. Specifically, it posits that for structures that display bilateral symmetry, those with greater functional...
In systems with early stage sex‐chromosome evolution, climate gradients can largely explain changes in the sex‐determining systems (i.e., genetic or environmental factors). However, in the common frog Rana temporaria, Phillips et al. found that phylogeography, rather than elevation (used as a proxy for climate), was associated with homomorphic sex‐chromosome differentiation levels.
Male hummingbirds have repeatedly evolved sexually dimorphic tails that they use as ornaments during courtship. We examine how male ornament evolution is reflected in female morphology. Lande's two‐step model of the evolution of dimorphism predicts that γ (the genetic correlation between the sexes) causes trait elaboration to first evolve quickly in both sexes, then dimorphism evolves more slowly...
Most of the theory for the evolution of caste specialization in social insects assumes that increased efficiency in worker labor leads to specialization and increased worker efficiency gives colonies with behavioral specialists an advantage. However, there are an increasing number of studies that show that the task specialists within social insect colonies do not have the highest efficiency. Indeed,...
Most flowering plants are hermaphroditic and experience strong pressures to evolve self‐pollination (automatic selection and reproductive assurance). Inbreeding depression (ID) can oppose selection for selfing, but it remains unclear if ID is typically strong enough to maintain outcrossing. To measure the full cost of sustained inbreeding on fitness, and its genomic basis, we planted highly homozygous,...
Sex chromosomes in vertebrates range from highly heteromorphic (as in most birds and mammals) to strictly homomorphic (as in many fishes, amphibians, and nonavian reptiles). Reasons for these contrasted evolutionary trajectories remain unclear, but species such as common frogs with polymorphism in the extent of sex chromosome differentiation may potentially deliver important clues. By investigating...
What evolutionary processes shaped the genomic landscape of differentiation in Selasphorus hummingbirds? Battey shows that the islands of differentiation on the Z chromosome are most likely the outcome of linked selection. Furthermore, these islands might contain barrier loci that contribute to reproductive isolation between these hybridizing hummingbirds.
How do obligate parasites cope with hosts that lack genetic elements required for parasite replication? Gupta et. al. (2020) illustrate an experimental evolution system where lambda bacteriophages circumvent a defective gene network in their E. coli host (which initially made it impossible for them to replicate) through both intracellular cooperation and evolutionary changes in phage life‐history...
To better predict how populations and communities respond to climatic temperature variation, it is necessary to understand how the shape of the response of fitness‐related rates to temperature evolves (the thermal performance curve). Currently, there is disagreement about the extent to which the evolution of thermal performance curves is constrained. One school of thought has argued for the prevalence...
Levels of genetic differentiation vary widely along the genomes of recently diverged species. What processes cause this variation? Here, I analyze geographic population structure and genome‐wide patterns of variation in the Rufous, Allen's, and Calliope Hummingbirds (Selasphorus rufus/Selasphorus sasin/Selasphorus calliope) and assess evidence that linked selection on the Z chromosome drives patterns...
An important driver of evolution in viruses is natural selection to optimize the use of their hosts’ genetic network. To learn how viruses respond to this pressure, we disrupted the genetic network of Escherichia coli to inhibit replication of its virus, bacteriophage lambda, and then observed how λ evolved to compensate. We deleted E. coli's dnaJ gene, which lambda uses to initiate DNA replication...
Sexual selection theory provides a framework for investigating the evolution of traits involved in attracting and competing for mates. Given the sexual function of such traits, studies generally focus on individual interactions (i.e., displays and contests) in explaining trait origin and persistence. We show that ecological factors can strongly influence the adaptive value of these traits, and changes...
Primate limb morphology is often described as either generalized, that is, suited to a range of locomotor and positional behaviors, or specialized for unique locomotor behaviors such as brachiation or bipedalism. The evolution of highly specialized limb morphology may result in loss of evolvability, that is, in a decreased capacity of the locomotor skeleton to evolve in response to selection towards...
Comparative phylogeographic studies often support shared divergence times for co‐distributed species with similar life histories and habitat specializations. During the late Holocene, West Africa experienced aridification and the turnover of rain forest habitats into savannas. These fragmented rain forests harbor impressive numbers of endemic and threatened species. In this setting, populations of...
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