Background Samar Island Natural Park (SINP), the largest terrestrial protected area in the Philippines, encompasses the nations's most extensive karst landscape and largest remaining intact old-growth forests. While it is widely recognised for its exceptional biodiversity, comprehensive information for SINP, especially for plants, remains elusive. As a result, major taxonomic and distributional gaps persist. Nevertheless, with its immense biological value and urgent conservation needs, SINP has been nominated as a UNESCO World Heritage Site. To bolster this nomination, field surveys combined with secondary data were performed to generate a checklist of vascular flora of SINP. New information A total of 874 morphospecies representing 124 families and 444 genera were documented in SINP. The flora is predominantly native and exhibits high endemism, including 339 Philippine endemics and 37 species restricted to Samar Island, alongside 82 newly-recorded species for the island. The taxonomic composition, dominated by Rubiaceae, Orchidaceae and other species-rich families, reflects both regional floristic patterns and SINP's biogeographical positioning within the Sunda-Sahul Convergence Zone. Moreover, a notable portion of its flora is threatened under the IUCN and DENR-DAO listings, with the majority classified as Not Evaluated. Collectively, these findings demonstrate that SINP functions as a critical refuge for some of the Philippines' most unique and vulnerable plant lineages.

Makaleyi görüntüle

The diamondback moth (DBM), Plutella xylostella (Lepidoptera: Plutellidae) is a very destructive crucifer-specialized pest that has resulted in significant crop losses worldwide. DBM is well attracted to glucosinolates (which act as fingerprints and essential for herbivores in host plant recognition) containing crucifers such as wintercress, Barbarea vulgaris (Brassicaceae) despite poor larval survival on it due to high-to-low concentration of saponins and generally to other plants in the genus Barbarea . B. vulgaris build up resistance against DBM and other herbivorous insects using glucosinulates which are used in plant defense. Aside glucosinolates, Barbarea genus also contains triterpenoid saponins, which are toxic to insects and act as feeding deterrents for plant specialist herbivores (such as DBM). Previous studies have found interesting relationship between the host plant and secondary metabolite contents, which indicate that attraction or resistance to specialist herbivore DBM, is due to higher concentrations of glucosinolates and saponins in younger leaves in contrast to the older leaves of Barbarea genus. As a response to this phenomenon, herbivores as DBM has developed a strategy of defense against these plant biochemicals. Because there is a lack of full knowledge in understanding bioactive molecules (such as saponins) role in plant defense against plant herbivores. Thus, in this review, we discuss the role of secondary plant metabolites in plant defense mechanisms against the specialist herbivores. In the future, trials by plant breeders could aim at transferring these bioactive molecules against herbivore to cash crops.

Makaleyi görüntüle

Using an appropriately designed and replicated study of a latitudinal influence on rates of evolution, we test the prediction by K. Rohde [(1992) Oikos 65, 514-527] that the tempo of molecular evolution in the tropics is greater than at higher latitudes. Consistent with this prediction we found tropical plant species had more than twice the rate of molecular evolution as closely related temperate congeners. Rohde's climate-speciation hypothesis constitutes one explanation for the cause of that relationship. This hypothesis suggests that mutagenesis occurs more frequently as productivity and metabolic rates increase toward the equator. More rapid mutagenesis was then proposed as the mechanism that increases evolutionary tempo and rates of speciation. A second possible explanation is that faster rates of molecular evolution result from higher tropical speciation rates [e.g., Bromham, L. & Cardillo, M. (2003) J. Evol. Biol. 16, 200-207]. However, we found the relationship continued to hold for genera with the same number of, or more, species in temperate latitudes. This finding suggests that greater rates of speciation in the tropics do not cause higher rates of molecular evolution. A third explanation is that more rapid genetic drift might have occurred in smaller tropical species populations [Stevens, G. C. (1989) Am. Nat. 133, 240-256]. However, we targeted common species to limit the influence of genetic drift, and many of the tropical species we used, despite occurring in abundant populations, had much higher rates of molecular evolution. Nonetheless, this issue is not completely resolved by that precaution and requires further examination.

Makaleyi görüntüle

The haemolytic activity of saponins has been a known phenomenon for many years. In this work, structure-activity relationships were established from various triterpene saponins distinguishing hemolytic activity between mono- and bidesmosidic saponins. Saponins structure in Sapindaceae serve as a chimiotaxonomic criteria for dividing the species into two sub-families. In order to verify this criteria, five species were studied: Smelophyllum capense and Dimocarpus fumatus from the sub-family Sapindoideae, Filicium decipiens, Hippobromus pauciflorus, and Harpullia cupanioides from the sub-family Dodonaeoideae. Structure of eleven new saponins were elucidated from four species by the study of homo- and heteronuclear advanced NMR experiments and MS. Other metabolites were also isolated from Dimocarpus fumatus, including isoprenypchromenes and three new glycosides of long chain fatty alcohols.

Makaleyi görüntüle

Five new saponins have been isolated from the stem bark of Harpullia cupanioides and identified as 3-O-beta-D-glucopyranosyl(1-->2)[alpha-L-rhamnopyranosyl(1-->3)] beta-D-glucuronopyranosyl 22-O-angeloyl-A1-barrigenol, 3-O-beta-D-glucopyranosyl(1-->2)[alpha-L-rhamnopyranosyl(1-->3)] beta-D-glucuronopyranosyl 28-O-angeloyl-A1-barrigenol, 3-O-beta-D-galactopyranosyl(1-->2)[alpha-L-rhamnopyranosyl(1-->3)] beta-D-glucuronopyranosyl 28-O-angeloyl-A1-barrigenol. 3-O-beta-D-galactopyranosyl(1-->2)[alpha-L-rhamnopyranosyl(1-->3)] beta-D-glucuronopyranosyl 16-O-beta, beta-dimethylacryloyl-camelliagenin A and 3-O-beta-D-glucopyranosyl(1-->2)[alpha-L-rhamnopyranosyl(1-->3)] beta-D-glucuronopyranosyl 28-O-angeloyl-camelliagenin A. The structures were elucidated by analysis of 2D-NMR spectra and mass spectra.

Makaleyi görüntüle