Conservation biology of the last Italian population of Cistus laurifolius (Cistaceae): demographic structure, reproductive success and population genetics

Ionomic analysis, polyphenols characterization, analgesic, antiinflammatory and antioxidant capacities of Cistus laurifolius leaves: in vitro, in vivo, and in silico investigations

This study aims to investigate the chemical and mineral composition, antioxidant, analgesic, and anti-inflammatory effects of the aqueous extract of Cistus laurifolius var. atlanticus Pit. (Cistaceae). Additionally, molecular docking interactions of various ligands with antioxidant protein target urate oxidase (1R4U) and anti-inflammatory protein target cyclooxygenase-2 (3LN1), revealing potential dual activities and highlighting specific residue interactions. The chemical characterization focused at first glance on the mineral composition which showed that C. laurifolius extract is a mineral-rich source of potassium (K), magnesium (Mg), manganese (Mn), sodium (Na), phosphorus (P), and zinc (Zn). We next performed, ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) analysis, the latter showed various polyphenols in C. laurifolius extract including Gallic acid as the predominant polyphenol. Isoquercetin, Taxifolin and Astragalin were also among the major flavonoids detected. The antioxidant capacity of C. laurifolius leaves was tested using 2,2'-azino-bis (3-ethylbenzothiazoline-6-sulfonic acid) (ABTS), 2,2-diphenyl-1- picrylhydrazyl (DPPH) and reducing power (RP) assays. In vitro analysis of the anti-inflammatory property of C. laurifolius leaves was conducted by the albumin denaturation test and the in vivo was assessed in the sequel by carrageenan-induced paw edema test. The analgesic activity was evaluated in vivo using tail flick, acetic acid-induced contortion, and plantar tests. The findings showed that the leave extract had a powerful antioxidant activity with an IC50 values of 2.92 ± 0.03 µg/mL (DPPH) and 2.59 ± 0.09 µg/mL (in RP test). The studied extract strongly abolished the induced inflammation (82%). Albumin denaturation test recorded an IC50 value of 210 µg/mL. Importantly, the oral administration of C. laurifolius extract considerably reduced the nociceptive effect of acetic acid in rats, showing a significant analgesic effect in a dose-related manner. Altogether, our results showed that C. laurifolius can be a promising source of phytochemicals for drug development potential.

Strong conservatism of floral morphology during the rapid diversification of the genus Helianthemum

PREMISE

Divergence of floral morphology and breeding systems are often expected to be linked to angiosperm diversification and environmental niche divergence. However, available evidence for such relationships is not generalizable due to different taxonomic, geographical and time scales. The Palearctic genus Helianthemum shows the highest diversity of the family Cistaceae in terms of breeding systems, floral traits, and environmental conditions as a result of three recent evolutionary radiations since the Late Miocene. Here, we investigated the tempo and mode of evolution of floral morphology in the genus and its link with species diversification and environmental niche divergence.

METHODS

We quantified 18 floral traits from 83 taxa and applied phylogenetic comparative methods using a robust phylogenetic framework based on genotyping-by-sequencing data.

RESULTS

We found three different floral morphologies, putatively related to three different breeding systems: type I, characterized by small flowers without herkogamy and low pollen to ovule ratio; type II, represented by large flowers with approach herkogamy and intermediate pollen to ovule ratio; and type III, featured by small flowers with reverse herkogamy and the highest pollen to ovule ratio. Each morphology has been highly conserved across each radiation and has evolved independently of species diversification and ecological niche divergence.

CONCLUSIONS

The combined results of trait, niche, and species diversification ultimately recovered a pattern of potentially non-adaptive radiations in Helianthemum and highlight the idea that evolutionary radiations can be decoupled from floral morphology evolution even in lineages that diversified in heterogeneous environments as the Mediterranean Basin.

Dynamics of secondary pollen presentation in Campanula medium (Campanulaceae)

After several decades of research, dynamics and patterns of mating system in floral evolution remain incompletely understood, especially with regards to strategies that combine both outcrossing and selfing, as frequently recorded in the genus Campanula. Data about temporal and spatial dynamics of secondary pollen presentation are still scarce in literature: we investigated them using Campanula medium (Campanulaceae) as case study. Experimental pollinations were conducted under natural conditions, to characterise the breeding system of this species. Effects on stigma opening and stigma receptivity of stylar pollen presence were investigated in manipulated flowers. The temporal dynamics and fitness of male and female functional phases were estimated. Flower visitors and their interactions with sexual parts of the flower were also annotated. C. medium is xenogamous and self-incompatible, with a clear temporal separation between sexual functional phases. Floral lifespan is shortened by experimental outcrossing. Removal of pollen from the style shortened the time span of male function. Pollen viability was highest at the beginning of the anthesis, decreasing during the flowering period, whereas stigmatic receptivity shows an opposite trend. We found a severe pollen limitation in the studied population. Bees were the most frequent floral visitors. In some of these insects we observed stereotyped interactions with the reproductive structures of the flower, in particular with the pollen, exposed along the upper and median portion of the style. Sexual phases in C. medium are inversely correlated and finely spatially and temporally coordinated, since stigma maturation is scalar along its length and depends on pollen presence on the style. Overall, our findings push forward the knowledge on reproductive strategies in Campanula.

Is population genetic structure of vascular plants shaped more by ecological or geographic factors? A study case on the Mediterranean endemic Centaurea filiformis (Asteraceae)

All known populations of the Sardinian endemic Centaurea filiformis Viv. (Asteraceae) were studied in order to understand the impact of both geographic and ecological factors on the genetic structuring of this species. Fourteen populations and 234 individuals were sampled. The demographic structure of the populations and the reproductive ecology were estimated in 28 plots. Population genetic analyses were based on SSR markers. Genetic structure was investigated by spatial Bayesian methods. Average densities of 0.51 individuals m^-2 were detected, with a prevalence of adults. Ten species of pollinators were identified; C. filiformis ability to self-pollinate and myrmecochory were demonstrated experimentally. The populations displayed an average heterozygosity value of H_e  = 0.576 and high genetic differentiation (overall F_ST  = 0.218). Bayesian analysis suggests that five is the most probable number of gene pools of origin. A strong correlation between geographic distances and genetic distances among populations was highlighted. The demographic population structure of C. filiformis is dominated by adults, suggesting that it is a stable-regressive or senile species, investing more in local persistence than colonisation ability. Despite the scattered distribution, the populations studied do not present evidence of genetic erosion. The analysis of genetic differentiation reveals very high differentiation levels among populations, thus indicating that effective barriers exist against gene flow. A general conclusion is that population distribution results in a clear genetic structure for the populations studied, and that geography and not ecology is shaping the present distribution of this species.