Biology subjects

Rönkä, K.

Publications and source records attributed to Rönkä, K..

3 recordsLinked to original sources

bioRxiv2024

Can social interactions rescue "lost" behavioural defences in an allopatric cuckoo host?

Behavioral defenses are a key adaptation across animals, but confirming decay under relaxed selection is challenging. If expression involves decision-making, then defenses may only be expressed when the right environmental cues are available (i.e. cryptic plasticity). Even if defenses wane, they could be quickly restored once selection resumes as animals can learn by observing others (i.e. social memory). Here we tested cryptic plasticity and social memory under relaxed selection in a cuckoo host, the Common Reed Warbler, by manipulating perceived parasitism risk with social information in geographically-distinct areas differing in allopatry (100 to 1000 years). Despite predicting social information of a cuckoo vs. a control would elicit otherwise cryptic behavioral defenses, only birds that mobbed model cuckoos prior to manipulation upregulated this defense, and only in the recently allopatric population. Social information also had no effect on low-to-absent rates of foreign egg rejection, a second line of defense common to cuckoo host species. These results contrast with parasitized locations where similar methods provoke mobbing and increase egg rejection ten-fold. Our study therefore suggests that, even when manipulating information to account for reaction norms, behavioral defenses may degrade rapidly under relaxed selection, demonstrating a process facilitating a geographic mosaic of coevolution.

animal behavior and cognition↗

bioRxiv2022

Genomic consequences of range expansion and colonisation in the reed warbler (Acrocephalus scirpaceus)

Range expansion is a common natural phenomenon, which may be intensified by human-induced drivers such as climate change and alterations of habitat. The genetic consequences of range expansion are potentially major, and it is important to study known cases of range expansion to understand how human activities affect contemporary evolution, and to learn more about the genetic adaptive potential of species. The reed warbler (Acrocephalus scirpaceus) is a long-distance migratory bird breeding in Eurasia and wintering south of Sahara. It is currently expanding its range northwards, likely as a consequence of climate change. Interestingly, however, reed warblers have also recently colonised new territory southwards, following habitat restoration at the southern range margin. In this study, we investigate the genetic consequences of these two-directional range expansions with RAD-seq, looking at 10 populations from north to south in Europe. We investigate population structure and genome diversity, and assess the role of selection in divergence between populations across the species range. We do not find evidence of strong genetic structure in the reed warbler populations, and the youngest edge populations do not exhibit any substantial loss in genetic diversity, suggesting ongoing gene flow. On a smaller scale, the edge populations are the most genetically distinct, and we identify environmental disparity, especially in precipitation variability, as the main barrier of gene flow, to a greater extent than geographic distance. We find no evidence that the loci involved in population divergence and adaptation in the core populations are the same that are involved in adaptation at the range edges. Using three genome scan methods to identify selection, we found 49 SNPs putatively under selection, of which 33 were located in introns of 28 unique genes. Most of these are correlated with differences in climatic variables of temperature and precipitation. Some genome scan outliers show signs of being part of nascent selective sweeps, especially one which is distinct for the northern range edge. Our results suggest that in the reed warbler, contemporary range expansion has had little effect on molecular diversity and has been rapidly followed by local adaptation to climatic conditions, which could further corroborate the rapid pace at which colonisation of novel environments has occurred both northwards and southwards.

evolutionary biology↗

bioRxiv2021

A Chromosome-level Genome Assembly of the Reed Warbler (Acrocephalus scirpaceus)

The reed warbler (Acrocephalus scirpaceus) is a long-distance migrant passerine with a wide distribution across Eurasia. This species has fascinated researchers for decades, especially its role as host of a brood parasite, and its capacity for rapid phenotypic change in the face of climate change. Currently, it is expanding its range northwards in Europe, and is altering its migratory behaviour in certain areas. Thus, there is great potential to discover signs of recent evolution and its impact on the genomic composition of the reed warbler. Here we present a high-quality reference genome for the reed warbler, based on PacBio, 10X and Hi-C sequencing. The genome has an assembly size of 1,075,083,815 bp with a scaffold N50 of 74,438,198 bp and a contig N50 of 12,742,779 bp. BUSCO analysis using aves_odb10 as a model showed that 95.7% of genes in the assembly were complete. We found unequivocal evidence of two separate macrochromosomal fusions in the reed warbler genome, in addition to the previously identified fusion between chromosome Z and a part of chromosome 4A in the Sylvioidea superfamily. We annotated 14,645 protein-coding genes, of which 97.5% were complete BUSCO orthologs. This reference genome will serve as an important resource, and will provide new insights into the genomic effects of evolutionary drivers such as coevolution, range expansion, and adaptations to climate change, as well as chromosomal rearrangements in birds. Significance statementThe reed warbler (Acrocephalus scirpaceus) has been lacking a genomic resource, despite having been broadly researched in studies of coevolution, ecology and adaptations to climate change. Here, we generated a chromosome-length genome assembly of the reed warbler, and found evidence of macrochromosomal fusions in its genome, which are likely of recent origin. This genome will provide the opportunity for a deeper understanding of the evolution of genomes in birds, as well as the evolutionary path and possible future of the reed warbler.

genomics↗