Ecotypic divergences of the alpine herb Potentilla matsumurae adapted to fellfield-snowbed habitats across a series of mountain sky islands

Environmental gradients shape genetic variation in the desert moss, Syntrichia caninervis Mitt. (Pottiaceae)

The moss Syntrichia caninervis Mitt. is distributed throughout drylands globally, and often anchors ecologically significant communities known as biological soil crusts (biocrusts). The species occupies a variety of dryland habitats with varying levels of drought and temperature stress, suggesting the potential for ecological specialization within S. caninervis. Here, we sampled S. caninervis from sites along two elevation gradients and used restriction site associated DNA sequencing to compare the relative impacts of environmental factors and geospatial distances on genetic differentiation in S. caninervis populations. While we found no evidence of isolation by distance in our data, one environmental variable, mean annual precipitation (MAP), was found to be a positive predictor of FST. An ecological association analysis identified 32 SNP alleles that covary significantly with MAP, 15 of which fall within the exonic regions of genes with annotations suggesting diverse roles in response to dehydration stress. Understanding the degree to which genetic variation in S. caninervis is associated with environmental factors is key to predicting its potential for persistence in the face of global climate change, which is predicted to be especially detrimental to desert organisms already living at their physiological limits.

The diversity of iron acquisition strategies of calcifuge plant species from dry acidic grasslands

Although the calcifuge plant species existing in dry acidic grasslands are believed to be prone to iron (Fe)-dependent limitations, little is known about their susceptibility and reaction to pH-dependent Fe starvation. Therefore, the present study examines the effects of contrasting soils (acidic Podzol vs alkaline Rendzina) and Fe supplementation (Fe-HBED) on alkaline substratum (5 and 25 μmol Fe-HBED kg^-1 soil). Five calcifuge dicotyledonous plant species (Alyssum montanum L., Antennaria dioica (L.) Gaertn., Hypochaeris radicata L., Jasione montana L. and Potentilla arenaria Borkh.) were tested in a pot experiment under field conditions. Chlorosis, chlorophyll content, growth and chlorophyll a fluorescence were measured. The elemental composition (contents of Ca, Mg, Fe, Mn, Zn and Cu) of the roots and shoots were analyzed, as well as their specialized metabolites. Two studied species (A. dioica d and J. montana) were susceptible to pH-dependent chlorosis, and this deficiency was successfully diminished by the application of Fe-HBED. Almost all the studied species (except A. montanum) preferred the acidic soil. Fe-HBED treatments were not sufficient for supporting the growth of H. radicata and J. montana in alkaline soil to the same degree as in acidic soil, which suggests additional non-Fe-dependent limitations. Both Fe starvation and Fe over-supplementation caused species-specific changes in chlorophyll a fluorescence. The disturbed Fe acquisition in the alkaline soil was not the sole source of the observed limitations, as the chlorosis-susceptible species demonstrated a complex interaction between Fe, Mn and Zn. The species resistant to lime chlorosis contained greater amounts of specialized metabolites than the susceptible plants. Our findings do not support hypothesis that all calcifuges are susceptible to Fe-dependent chlorosis: calcifuge plant species from dry acidic grasslands appear to have diverse Fe requirements and acquisition strategies.

Intraspecific independent evolution of floral spur length in response to local flower visitor size in Japanese Aquilegia in different mountain regions

Geographic differences in floral traits may reflect geographic differences in effective pollinator assemblages. Independent local adaptation to pollinator assemblages in multiple regions would be expected to cause parallel floral trait evolution, although sufficient evidence for this is still lacking. Knowing the intraspecific evolutionary history of floral traits will reveal events that occur in the early stages of trait diversification. In this study, we investigated the relationship between flower spur length and pollinator size in 16 populations of Aquilegia buergeriana var. buergeriana distributed in four mountain regions in the Japanese Alps. We also examined the genetic relationship between yellow- and red-flowered individuals, to see if color differences caused genetic differentiation by pollinator isolation. Genetic relationships among 16 populations were analyzed based on genome-wide single-nucleotide polymorphisms. Even among populations within the same mountain region, pollinator size varied widely, and the average spur length of A. buergeriana var. buergeriana in each population was strongly related to the average visitor size of that population. Genetic relatedness between populations was not related to the similarity of spur length between populations; rather, it was related to the geographic proximity of populations in each mountain region. Our results indicate that spur length in each population evolved independently of the population genetic structure but in parallel in response to local flower visitor size in different mountain regions. Further, yellow- and red-flowered individuals of A. buergeriana var. buergeriana were not genetically differentiated. Unlike other Aquilegia species in Europe and America visited by hummingbirds and hawkmoths, the Japanese Aquilegia species is consistently visited by bumblebees. As a result, genetic isolation by flower color may not have occurred.

Intense browsing by sika deer (Cervus nippon) drives the genetic differentiation of hairy nettle (Urtica thunbergiana) populations

Many studies have inferred the way in which natural selection, genetic drift and gene flow shape the population genetic structures, but very few have quantified the population differentiation under spatially and temporally varying levels of selection pressure, population fluctuation and gene flow. In Nara Park (6.6 km²), central Japan, where several hundred sika deer (Cervus nippon) have been protected for more than 1,200 years, heavily- or moderately-haired nettle (Urtica thunbergiana) populations have evolved probably in response to intense deer browsing. Here, we analysed the genetic structure of two Nara Park populations and five surrounding populations using amplified fragment length polymorphism markers. A total of 546 marker loci were genotyped from 210 individuals. A Bayesian method estimated 5.5% of these loci to be outliers, which are putatively under natural selection. Neighbour-joining, principal coordinates and Bayesian clustering analyses using all-loci, non-outlier loci and outlier loci datasets showed that the Nara Park populations formed a cluster distinct from the surroundings. These results indicate the genome-wide differentiation of the Nara Park populations from the surroundings. Moreover, these imply the following: (1) gene flow is limited between these populations and thus genetic drift is a major factor causing the differentiation; and (2) natural selection imposed by intense deer browsing has contributed to some extent to the differentiation. In conclusion, sika deer seems to have counteracted genetic drift to drive the genetic differentiation of hairy nettles in Nara Park. This study suggests that a single herbivore species could lead to genetic differentiation among plant populations.

Intraspecific convergence of floral size correlates with pollinator size on different mountains: a case study of a bumblebee-pollinated Lamium (Lamiaceae) flowers in Japan

Background

Geographic differences in floral size sometimes reflect geographic differences in pollinator size. However, we know little about whether this floral size specialization to the regional pollinator size occurred independently at many places or occurred once and then spread across the distribution range of the plant species.

Results

We investigated the relationship between the local floral size of flowers and local pollinator size in 12 populations of Lamium album var. barbatum on two different mountains in the Japan Alps. Then, using 10 microsatellite markers, we analyzed genetic differentiation among the 12 populations. The results showed that local floral size was correlated with the average size of relevant morphological traits of the local pollinators: floral size was greater in populations visited frequently by the largest flower visitors, Bombus consobrinus queens, than it was in other populations. We also found that the degree of genetic similarity between populations more closely reflected interpopulation geographic proximity than interpopulation similarity in floral size.

Conclusions

Although genetic similarity of populations was highly associated with geographic proximity, floral size varied independently of geographic proximity and was associated with local pollinator size. These results suggest that in L. album var. barbatum, large floral size evolved independently in populations on different mountains as a convergent adaptation to locally abundant large bumblebee species.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12862-021-01796-8.