Biology subjects

Morales-Garcia, J.

Publications and source records attributed to Morales-Garcia, J..

3 recordsLinked to original sources

bioRxiv2025

Demographic history inferred from an inversion-rich spruce bark beetle genome

The demographic history of species inferred from whole-genome data provides quantitative insights into key biological parameters such as population size changes and divergence times. Reliable estimates often require data that have not been affected by selection. Extensive research, however, indicates that many species harbour multiple polymorphic chromosomal inversions, which often evolve under different selective pressures. Consequently, inversions can influence genome-wide patterns of variation and subsequent evolutionary inferences. In this study, we used genome-wide data from over 300 spruce bark beetle (Ips typographus) individuals from 23 populations across Europe to reconstruct their demographic history and to investigate the impact of a complex polymorphic inversion landscape (covering approximately 28% of the beetle genome) on demographic inference. We used two complementary methods, Pairwise Sequential Markovian Coalescent (PSMC) and Site Frequency Spectrum (SFS)-based modelling, and revealed a Late Pleistocene divergence ([~]79 kya) between populations from the southern and northern parts of the species European range, and a long-term effective population size of [~]250,000. The southern group underwent significant population expansion after this divergence event, whereas the northern group expanded during the Holocene ([~]7 kya). Recent population size estimates suggest that the southern group is twice as large as the northern group. Neglecting the presence of chromosomal inversions did not significantly affect the model selection procedure and resulted in relatively small biases in the estimated demographic parameters. This study provides information on the historical population dynamics of the spruce bark beetle and improves our understanding of the influence of a complex genomic architecture on the inference of evolutionary history.

evolutionary biology↗

bioRxiv2025

Selection inference in a complex genomic landscape: the role of inversions in the spruce bark beetle

Understanding the genetic basis of adaptation is a key objective in evolutionary biology. Although advances in genomic selection scans have greatly improved our ability to detect signatures of adaptation, distinguishing true signals from false positives remains challenging. This task is particularly difficult in regions of reduced recombination, such as polymorphic inversions. In this study, we examine the genome-wide landscape of selection in the European spruce bark beetle (Ips typographus), Europes most destructive forest pest, which has one of the most complex inversion-associated recombination landscapes known. Using simulation-based analyses and whole-genome resequencing data from 312 individuals across 23 populations, we applied two complementary selection scan methods (nSL and {Lambda}) to assess how inversions influence the detection of adaptive signals. Simulations revealed that the two selection scan methods differ in their susceptibility to false-positive signals within inversions and that partitioning data by inversion genotype (i.e., homozygote classes) can substantially reduce these errors. Consistent with the results of our simulations, our empirical data showed that inversions are highly enriched for selection signals when all inversion genotypes are analyzed but are depleted when only homozygotes are considered. This demonstrates that focusing on homozygote genotypes allows for a more precise identification of putative selection targets and haplotype-specific signals, as it overcomes the confounding effects of suppressed recombination in heterokaryotypic individuals. In contrast, the detection of selection in collinear regions was largely unaffected by the presence of inversions. Our findings highlight that inversions may play an important role in shaping adaptation, underscoring the need to account for species-specific genomic architecture when interpreting signals from selection scans. Author summaryDetecting the genetic basis of adaptation is one of the main goals in evolutionary biology. However, it is often difficult to tell whether selection signals identified by genome scans truly reflect natural selection signatures or are simply artefacts of genome structure. In this study, we examined how polymorphic inversions affect the detection of selection in the European spruce bark beetle, one of Europes most destructive forest pests. First, we assessed two selection scan methods using simulation approach. Second, we tested the influence of polymorphic inversion on the selection inference using genome-wide data from 23 beetle populations. We showed that inversions can create false signals of selection when all individuals are analyzed together but by separating individuals according to their inversion genotypes, we were able to distinguish potential adaptive regions from false positives. Our results demonstrate that accounting for genomic architecture is crucial for identifying selection signatures and provide practical guidelines for studying species with inversion-rich genomes.

evolutionary biology↗

bioRxiv2023

Complex genomic landscape of inversion polymorphism in Europe's most destructive forest pest

In many species, polymorphic inversions underlie complex phenotypic polymorphisms and facilitate local adaptation in the face of gene flow. Multiple polymorphic inversions can co-occur in a genome, but the prevalence, evolutionary significance, and limits to complexity of genomic inversion landscapes remain poorly understood. Here, we examine genome-wide variation in one of Europes most destructive forest pests, the spruce bark beetle Ips typographus, scan for polymorphic inversions, and test whether inversions are involved in key adaptations in this species. We analyzed 240 individuals from 18 populations across the species European range and, using a whole-genome resequencing approach, identified 27 polymorphic inversions covering approximately 28% of the genome. The inversions vary in size and in levels of intra-inversion recombination, are highly polymorphic across the species range, and often overlap, forming a complex genomic architecture. We test several mechanisms, including directional selection, overdominance and associative overdominance that can contribute to the maintenance of inversion polymorphisms in the genome. We show that the heterogeneous inversion landscape is likely maintained by the combined action of several evolutionary forces and that inversions are enriched in odorant receptor genes encoding key elements of recognition pathways for host plants, mates, and symbiotic fungi. Our results indicate that the genome of this major forest pest of growing social, political, and economic importance harbors one of the most complex inversion landscapes described to date posing a question about limits of genomic architecture complexity.

evolutionary biology↗