Complex Patterns of Diversification in the Gray Zone of Speciation: Model-Based Approaches Applied to Patagonian Liolaemid Lizards (Squamata: Liolaemus kingii clade)

In this study we detangled the evolutionary history of the Patagonian lizard clade Liolaemus kingii, coupling dense geographic sampling and novel computational analytical approaches. We analyzed nuclear and mitochondrial data (restriction site-associated DNA sequencing and cytochrome b) to hypothesize and evaluate species limits, phylogenetic relationships, and demographic histories. We complemented these analyses with posterior predictive simulations to assess the fit of the genomic data to the multispecies coalescent model. We also employed a novel approach to time-calibrate a phylogenetic network. Our results show several instances of mito-nuclear discordance and consistent support for a reticulated history, supporting the view that the complex evolutionary history of the kingii clade is characterized by extensive gene flow and rapid diversification events. We discuss our findings in the contexts of the "gray zone" of speciation, phylogeographic patterns in the Patagonian region, and taxonomic outcomes. [Model adequacy; multispecies coalescent; multispecies network coalescent; phylogenomics; species delimitation.].

Revealing the coexistence of differentiation and communication in an endemic hare, Lepus yarkandensis (Mammalia, Leporidae) using specific-length amplified fragment sequencing

BACKGROUND

The Yarkand hare (Lepus yarkandensis Günther, 1875) is endemic to oasis and desert areas around the Tarim Basin in the Xinjiang Uyghur Autonomous Region of northwest China; however, genome-wide information for this species remains limited. Moreover, the genetic variation, genetic structure, and phylogenetic relationships of Yarkand hare from the plateau mountain regions have not been reported. Thus, we used specific-length amplified fragment sequencing (SLAF-seq) technology to evaluate the genetic diversity of 76 Yarkand hares from seven geographic populations in the northern and southwestern parts of the Tarim Basin to investigate single-nucleotide polymorphism (SNP) marker-based population differentiation and evolutionary processes. Selective sweep analysis was conducted to identify genetic differences between populations.

RESULTS

Using SLAF-seq, a total of 1,835,504 SNPs were initially obtained, of which 308,942 high-confidence SNPs were selected for further analysis. Yarkand hares exhibited a relatively high degree of genetic diversity at the SNP level. Based on pairwise FST estimates, the north and southwest groups showed a moderate level of genetic differentiation. Phylogenetic tree and population structure analyses demonstrated evident systematic phylogeographical structure patterns consistent with the geographical distribution of the hares. Hierarchical analysis of molecular variation further indicated that genetic variation was mainly observed within populations. Low to moderate genetic differentiation also occurred among populations despite a common genomic background, likely due to geographical barriers, genetic drift, and differential selection pressure of distinct environments. Nevertheless, the observed lineage-mixing pattern, as indicated by the evolutionary tree, principal component analysis, population structure, and TreeMix analyses, suggests a certain degree of gene flow between the north and southwest groups. This may be related to the migration of hares to high-altitude water sources southwest of the basin during glacial climatic oscillations, as well as river re-diffusion and oasis restoration in the basin following the glacial period. We also identified candidate genes, and their associated gene ontology terms and pathways, related to the adaptation of Yarkand hares to different environmental habitats.

CONCLUSIONS

The identified genome-wide SNPs, genetic diversity, and population structure of Yarkand hares expand our understanding of the genetic background of this endemic species and provide valuable insights into its environmental adaptation, allowing for further exploration of the underlying mechanisms.

Differentiation in the eastern Asian Periphyllus koelreuteriae (Hemiptera: Aphididae) species complex driven by climate and host plant

Divergent adaptation to different ecological conditions is regarded as important for speciation. For phytophagous insects, there is limited empirical evidence on species differentiation driven by climate and host plant. The recent application of molecular data and integrative taxonomic practice may improve our understanding of population divergence and speciation. Periphyllus koelreuteriae aphids feed exclusively on Koelreuteria (Sapindaceae) in temperate and subtropical regions of eastern Asia, and show morphological and phenological variations in different regions. In this study, phylogenetic and haplotype network analyses based on four genes revealed that P. koelreuteriae populations comprised three distinct genetic clades corresponding to climate and host plants, with the populations from subtropical highland regions and on Koelreuteria bipinnata host plants representing the most basal clade. These genetic lineages also showed distinct characteristics in terms of morphology and life cycle. The results indicate that P. koelreuteriae is a species complex with previously unrevealed lineages, whose differentiation may have been driven by climatic difference and host plant.