Phytogeography of Najas gracillima (Hydrocharitaceae) in North America and its cryptic introduction to California

GC-MS Analysis, Neuropharmacological, and Antidiarrheal Activities of the Acetone Extract of Najas gracillima Seaweed: In Vivo and In Silico Study

Najas gracillima, a marine seaweed found in North America and Asia, was investigated for its neuropharmacological and antidiarrheal properties. Acetone extracts of N. gracillima (ANG) were analyzed using both in vivo and in silico methods. Gas chromatography-mass spectrometry (GC-MS) analysis was conducted to identify bioactive compounds present in the extract. In vivo assessments, including the elevated plus maze, light-dark box, and hole board tests, showed that ANG at doses of 200 and 400 mg/kg exhibited significant (p < 0.001) anxiolytic effects. Both doses also demonstrated antidepressant effects in the forced swimming and tail suspension tests by significantly (p < 0.001) reducing immobility time, with the 200 mg/kg dose showing more pronounced effects. Sedative activity was confirmed through open field and hole cross tests, where both doses exhibited significant (p < 0.001) sedative effects. ANG also demonstrated significant antidiarrheal effects at 400 mg/kg in castor oil-induced diarrhea (p < 0.05) and gastrointestinal motility tests (p < 0.01). Molecular docking simulations revealed that compounds from ANG had strong binding affinities to critical drug targets involved in anxiety, depression, sleep disorders, and diarrhea. These findings suggest that N. gracillima holds potential for therapeutic use in treating neuropharmacological disorders and diarrhea, warranting further investigation.

The phylogeographic structure of Hydrilla verticillata (Hydrocharitaceae) in China and its implications for the biogeographic history of this worldwide-distributed submerged macrophyte

BACKGROUND

Aquatic vascular plants are a distinctive group, differing from terrestrial plants in their growth forms and habitats. Among the various aquatic plant life forms, the evolutionary processes of freshwater submerged species are most likely distinct due to their exclusive occurrence in the discrete and patchy aquatic habitats. Using the chloroplast trnL-F region sequence data, we investigated the phylogeographic structure of a submerged macrophyte, Hydrilla verticillata, the single species in the genus Hydrilla, throughout China, in addition to combined sample data from other countries to reveal the colonisation and diversification processes of this species throughout the world.

RESULTS

We sequenced 681 individuals from 123 sampling locations throughout China and identified a significant phylogeographic structure (NST > GST, p < 0.01), in which four distinct lineages occurred in different areas. A high level of genetic differentiation among populations (global FST = 0.820) was detected. The divergence of Hydrilla was estimated to have occurred in the late Miocene, and the diversification of various clades was dated to the Pleistocene epoch. Biogeographic analyses suggested an East Asian origin of Hydrilla and its subsequent dispersal throughout the world.

CONCLUSIONS

The presence of all four clades in China indicates that China is most likely the centre of Hydrilla genetic diversity. The worldwide distribution of Hydrilla is due to recent vicariance and dispersal events that occurred in different clades during the Pleistocene. Our findings also provide useful information for the management of invasive Hydrilla in North America.

Through thick and thin: cryptic sympatric speciation in the submersed genus Najas (Hydrocharitaceae)

Cryptic sympatric species arise when reproductive isolation is established in sympatry, leading to genetically divergent lineages that are highly similar morphologically or virtually indistinguishable. Although cryptic sympatric species have been reported in various animals, fungi, and protists, there are few compelling examples for plants. This investigation presents a case for cryptic sympatric speciation in Najas flexilis, a widespread aquatic plant, which extends throughout northern North America and Eurasia. The taxon is noted for its variable seed morphology, which earlier research associated with cytotypes; i.e., diploids were characterized by thicker seeds and tetraploids by thinner seeds. However, cytotypes are not patterned geographically with diploid and tetraploid plants often found in close proximity within the same lake. Using digital image and DNA sequence analyses, we found that diploids and tetraploids are well-isolated and remain genetically distinct throughout their sympatric range, where sterile hybrids occur frequently. Incorporation of sequence data from the single-copy nuclear phytoene desaturase locus revealed further that the tetraploids are allopolyploid derivatives of N. flexilis and N. guadalupensis, the latter a closely related species with an overlapping distribution. We conclude that the taxon widely known as N. flexilis actually comprises two cryptic, sibling species, which diverged in sympatry by interspecific hybridization and subsequent chromosomal isolation. By comparing seed morphology of type specimens, we associated the names N. flexilis and N. canadensis to the diploids and tetraploids respectively. Additionally, the narrowly restricted taxon known formerly as N. muenscheri is shown via morphological and genetic evidence to be synonymous with N. canadensis.