The population genomic signature of environmental association and gene flow in an ecologically divergent tree speciesMetrosideros polymorpha(Myrtaceae)

Abstract

Genomewide markers enable us to study genetic differentiation within a species and the factors underlying it at a much higher resolution than before, which advances our understanding of adaptation in organisms. We investigated genomic divergence in Metrosideros polymorpha, a woody species that occupies a wide range of ecological habitats across the Hawaiian Islands and shows remarkable phenotypic variation. Using 1659 single nucleotide polymorphism (SNP) markers annotated with the genome assembly, we examined the population genetic structure and demographic history of nine populations across five elevations and two ages of substrates on Mauna Loa, the island of Hawaii. The nine populations were differentiated into two genetic clusters distributed on the lower and higher elevations and were largely admixed on the middle elevation. Demographic modelling revealed that the two genetic clusters have been maintained in the face of gene flow, and the effective population size of the high-altitude cluster was much smaller. A F -based outlier search among the 1659 SNPs revealed that 34 SNPs (2.05%) were likely to be under divergent selection and the allele frequencies of 21 of them were associated with environmental changes along elevations, such as temperature and precipitation. This study shows a genomic mosaic of M. polymorpha, in which contrasting divergence patterns were found. While most genomic polymorphisms were shared among populations, a small fraction of the genome was significantly differentiated between populations in diverse environments and could be responsible for the dramatic adaptation to a wide range of environments.

Genomic evidence for asymmetric introgression by sexual selection in the common wall lizard

“…The putative selection targets were extracted based on being in the top 5% of log‐odds ratios for both π and F ST (Chen et al., ) (Figure a). The genetic differentiation patterns were compared between candidate loci and non‐candidate (“neutral”) loci using pairwise F ST analysis for populations from different regions (Izuno et al., ). To further study the genetic differentiation of the candidate loci, we conducted the neighbour‐joining tree analysis for individuals from the Syndrome and Reference Groups.…”

RADseq resolves the phylogeny of Hawaiian Myrsine (Primulaceae) and provides evidence for hybridization

“…Welch et al (2016) sequenced whole plastomes of Hawaiian mints (Lamiaceae); Jennings et al (2016) used restriction site-associated DNA sequencing (RADseq) in a population-level study of two species of Hawaiian Lobeliads. Izuno et al (2016Izuno et al ( , 2017 and Choi et al (2020) used wholegenome sequencing to study population genomics of the most iconic Hawaiian tree species Metrosideros polymorpha Gaudich. (ʻŌhiʻa, Myrtaceae).…”

Genecology and ecophysiology of the maintenance of foliar phenotypic polymorphisms of Leptospermum recurvum (Myrtaceae) under oscillating atmospheric desiccation in the tropical‐subalpine zone of Mount Kinabalu, Borneo

“…In addition, although an allozyme analysis was conducted in their study, few polymorphic loci were detected, and the pattern of gene flow remained unveiled. Leaf trichome density is probably genetically based for this species, as seen in model plant Arabidopsis thaliana (L.) Heynh (Pattanaik, Patra, Singh, & Yuan, 2014) or in Hawaiian M. polymorpha (Izuno et al, 2017; Kitayama et al, 1997; Tsujii et al, 2015), but it is unknown to date.…”