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1. The influence of oviposition status on measures of transmission potential in malaria-infected mosquitoes depends on sugar availability

   https://doi.org/10.1186/s13071-024-06317-2  

   Shiau, Justine C; Garcia-Diaz, Nathan; Kyle, Dennis E; Pathak, Ashutosh K (December 2024, Parasites & Vectors)

   Abstract BackgroundLike other oviparous organisms, the gonotrophic cycle of mosquitoes is not complete until they have selected a suitable habitat to oviposit. In addition to the evolutionary constraints associated with selective oviposition behavior, the physiological demands relative to an organism’s oviposition status also influence their nutrient requirement from the environment. Yet, studies that measure transmission potential (vectorial capacity or competence) of mosquito-borne parasites rarely consider whether the rates of parasite replication and development could be influenced by these constraints resulting from whether mosquitoes have completed their gonotrophic cycle. MethodsAnopheles stephensimosquitoes were infected withPlasmodium berghei, the rodent analog of human malaria, and maintained on 1% or 10% dextrose and either provided oviposition sites (‘oviposited’ herein) to complete their gonotrophic cycle or forced to retain eggs (‘non-oviposited’). Transmission potential in the four groups was measured up to 27 days post-infection as the rates of (i) sporozoite appearance in the salivary glands (‘extrinsic incubation period' or EIP), (ii) vector survival and (iii) sporozoite densities. ResultsIn the two groups of oviposited mosquitoes, rates of sporozoite appearance and densities in the salivary glands were clearly dependent on sugar availability, with shorter EIP and higher sporozoite densities in mosquitoes fed 10% dextrose. In contrast, rates of appearance and densities in the salivary glands were independent of sugar concentrations in non-oviposited mosquitoes, although both measures were slightly lower than in oviposited mosquitoes fed 10% dextrose. Vector survival was higher in non-oviposited mosquitoes. ConclusionsCosts to parasite fitness and vector survival were buffered against changes in nutritional availability from the environment in non-oviposited but not oviposited mosquitoes. Taken together, these results suggest vectorial capacity for malaria parasites may be dependent on nutrient availability and oviposition/gonotrophic status and, as such, argue for more careful consideration of this interaction when estimating transmission potential. More broadly, the complex patterns resulting from physiological (nutrition) and evolutionary (egg-retention) trade-offs described here, combined with the ubiquity of selective oviposition behavior, implies the fitness of vector-borne pathogens could be shaped by selection for these traits, with implications for disease transmission and management. For instance, while reducing availability of oviposition sites and environmental sources of nutrition are key components of integrated vector management strategies, their abundance and distribution are under strong selection pressure from the patterns associated with climate change. Graphical Abstract 

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2. The landscape of natural selection during early population establishment in an invasive lizard

   https://doi.org/10.1093/evolut/qpaf184  

   Gilbert, Anthony L; Fargevieille, Amélie; Delaney, David M; Durso, Andrew M; Hall, Joshua M; Kahrl, Ariel F; Mitchell, Timothy S; Pearson, Phillip R; Reedy, Aaron M; Cox, Robert M; et al (September 2025, Evolution)

   Henshaw, Jonathan; Wolf, Jason (Ed.)

   Abstract Populations during early stages of establishment are sensitive to forms of demographic regulation coinciding with rapid growth, which may also coincide with specific patterns of natural selection due to demographic variation. Understanding how selection varies during the establishment of new populations, however, is complicated by the constraint of knowing the precise age of a population as it grows over time. To address this, we established six brown anole (Anolis sagrei) populations on spoil islands in Florida and manipulated initial sex ratios to understand how natural selection is influenced by the demographic composition of founding populations. We found that initial sex ratios of founding populations led to age-specific patterns of natural selection. Juveniles experienced stronger selection in populations that began with a female-biased sex ratio, and the strength of natural selection on juvenile size strengthened with increasing population density. We also found substantial variation in selection, suggesting that the relationship between phenotypes and fitness across early generations of a population is not consistent over time. As a result, variation in natural selection driven by demographic aspects within populations may provide opportunities for rapid population growth and novel evolutionary trajectories during the earliest stages of establishment. 

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3. Repeated signatures of balancing selection in small and large populations of guppies (Poecilia reticulata)

   Paris, Josephine R; Whiting, James R; Ferrer_Obiol, Joan; Hughes, Kimberly A; Fraser, Bonnie A (March 2026, Philosophical transactions of the Royal Society of London B)

   Balancing selection is a powerful evolutionary force that maintains adaptive genetic and phenotypic diversity. Although methods to detect the footprints of balancing selection in genomic data have advanced, we still lack a clear understanding of how repeatable these signatures appear in wild populations, and how this repeatability is shaped by demographic history and existing genetic variation. The Trinidadian guppy (Poecilia reticulata) provides an ideal model to test the repeatability of balancing selection in the wild as there is strong evidence that negative frequency-dependent selection (NFDS) maintains colour polymorphism. We define repeatability as the same genomic window showing evidence of balancing selection across populations, regardless of origin (i.e., independence vs. ancestral maintenance). Analysing whole-genome sequencing data from 11 guppy populations (n = 195) with contrasting demographic contexts, we apply scans of balancing selection to explore which genomic regions show evidence of repeatability. We find that populations with small Ne show less genetic repeatability but still exhibit population-specific regions of elevated diversity, implicating independent balancing selection or other evolutionary mechanisms. We identify 23 regions with repeated signatures of balancing selection, including a region on LG22 containing genes involved in colour, vision, mate choice, and social behaviour. Investigating the repeatability of balancing selection in small and large populations improves our knowledge of how demographic factors interact with selective processes to shape natural variation. 

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4. Genome Report: Genomic novelty within a ‘great speciator’ revealed by a high-quality reference genome of the collared kingfisher ( Todiramphus chloris collaris )

   https://doi.org/10.1093/g3journal/jkac260  

   Eliason, Chad M; Hains, Taylor; McCullough, Jenna; Andersen, Michael J; Hackett, Shannon J (September 2022, G3 Genes|Genomes|Genetics)

   Abstract Islands are natural laboratories for studying patterns and processes of evolution. Research on island endemic birds has revealed elevated speciation rates and rapid phenotypic evolution in several groups (e.g., white-eyes, Darwin's finches). However, understanding the evolutionary processes behind these patterns requires an understanding of how genotypes map to novel phenotypes. To date, there are few high-quality reference genomes for species found on islands. Here, we sequence the genome of one of Ernst Mayr's ‘great speciators’, the collared kingfisher (Todiramphus chloris collaris). Utilizing high molecular weight DNA and linked-read sequencing technology, we assembled a draft high-quality genome with highly contiguous scaffolds (scaffold N50 = 19 Mb). Based on universal single-copy orthologues (BUSCO), we estimated a gene space completeness of 96.6% for the draft genome assembly. Population demographic history analyses reveal a distinct pattern of contraction and expansion in population size throughout the Pleistocene. Comparative genomic analysis of gene family evolution revealed that species-specific and rapidly expanding gene families in the collared kingfisher (relative to other Coraciiformes) are mainly involved in the ErbB signaling pathway and focal adhesion. Todiramphus kingfishers are a species-rich group that has become a focus of speciation research. This draft genome will be a platform for future taxonomic, phylogeographic, and speciation research in the group. For example, target genes will enable testing of changes in sensory structures associated with changes in vision and taste genes across kingfishers. 

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5. Estimating bonobo ( Pan paniscus ) and chimpanzee ( Pan troglodytes ) evolutionary history from nucleotide site patterns

   https://doi.org/10.1073/pnas.2200858119  

   Brand, Colin M.; White, Frances J.; Rogers, Alan R.; Webster, Timothy H. (April 2022, Proceedings of the National Academy of Sciences)

   Admixture appears increasingly ubiquitous in the evolutionary history of various taxa, including humans. Such gene flow likely also occurred among our closest living relatives: bonobos ( Pan paniscus ) and chimpanzees ( Pan troglodytes ). However, our understanding of their evolutionary history has been limited by studies that do not consider all Pan lineages or do not analyze all lineages simultaneously, resulting in conflicting demographic models. Here, we investigate this gap in knowledge using nucleotide site patterns calculated from whole-genome sequences from the autosomes of 71 bonobos and chimpanzees, representing all five extant Pan lineages. We estimated demographic parameters and compared all previously proposed demographic models for this clade. We further considered sex bias in Pan evolutionary history by analyzing the site patterns from the X chromosome. We show that 1) 21% of autosomal DNA in eastern chimpanzees derives from western chimpanzee introgression and that 2) all four chimpanzee lineages share a common ancestor about 987,000 y ago, much earlier than previous estimates. In addition, we suggest that 3) there was male reproductive skew throughout Pan evolutionary history and find evidence of 4) male-biased dispersal from western to eastern chimpanzees. Collectively, these results offer insight into bonobo and chimpanzee evolutionary history and suggest considerable differences between current and historic chimpanzee biogeography. 

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