Niche shift in invasive species: is it a case of “home away from home” or finding a “new home”?

In recent years, there has been a rather acrimonious debate on matters concerning the biology of invasive species, some as fundamental as the definition and what constitutes an invasive species. However, an abiding commonality of all invasive species is the fact that they have all moved away from their native ranges to newer and often non-native ranges. In plants, Lantana camara has shifted from its native South American range distribution to most other parts of the world. In animals, the African giant snail has dispersed from Africa to most parts of Asia. What do such niche shifts signify about the nature and quality of the habitats to which the invasive species have moved? In this paper, using the classical niche paradigm, we analyse if niche shifts of thirty-three of the world’s top invasive species constitute just moving from one habitat to another similar habitat somewhere on the earth (home away from home) or that they have moved to totally new habitats (different from their native home). Surprisingly, our results show that for 90% of the world’s top invasive species, movements have been largely restricted to homes away from home, rather than into alien homes. This clearly indicates the potential inertia that species might face in moving out of their fundamental niche. We discuss these results in the context of the overall debate on invasion biology and how niche conservatism may have played a role in dampening the rates of invasion.

     

Fusarium proliferatum, an endophytic fungus from Dysoxylum binectariferum Hook.f, produces rohitukine, a chromane alkaloid possessing anti-cancer activity

Rohitukine is a chromane alkaloid possessing anti-inflammatory, anti-cancer and immuno-modulatory properties. The compound was first reported from Amoora rohituka (Meliaceae) and later from Dysoxylum binectariferum (Meliaceae) and Schumanniophyton problematicum (Rubiaceae). Flavopiridol, a semi-synthetic derivative of rohitukine is a potent CDK inhibitor and is currently in Phase III clinical trials. In this study, the isolation of an endophytic fungus, Fusarium proliferatum (MTCC 9690) from the inner bark tissue of Dysoxylum binectariferum Hook.f (Meliaceae) is reported. The endophytic fungus produces rohitukine when cultured in shake flasks containing potato dextrose broth. The yield of rohitukine was 186 μg/100 g dry mycelial weight, substantially lower than that produced by the host tissue. The compound from the fungus was authenticated by comparing the LC–HRMS and LC–HRMS/MS spectra with those of the reference standard and that produced by the host plant. Methanolic extract of the fungus was cytotoxic against HCT-116 and MCF-7 human cancer cell lines (IC₅₀ = 10 μg/ml for both cancer cell lines).     

Fine- and local- scale genetic structure of <Emphasis Type="Italic">Dysoxylum malabaricum,</Emphasis> a late-successional canopy tree species in disturbed forest patches in the Western Ghats,India

Dysoxylum malabaricum (white cedar) is an economically important tree species, endemic to the Western Ghats, India, which is the world’s most densely populated biodiversity hotspot. In this study, we used variation at ten nuclear simple sequence repeat loci to investigate genetic diversity and fine scale spatial genetic structure (FSGS) in seedlings and adults of D. malabaricum from four forest patches in the northern part of the Western Ghats. When genetic variation was compared between seedlings and adults across locations, significant differences were detected in allelic richness, observed heterozygosity, fixation index (F _IS), and relatedness (P < 0.05). Reduced genetic diversity and increased relatedness at the seedling stage might be due to fragmentation and disturbance. There was no FSGS at the adult stage and FSGS was limited to shorter distance classes at the seedling stage. However, there was clear spatial genetic structure at the landscape level (<50 km), regardless of age class, due to limited gene flow between forest patches. A comparison of the distributions of size classes in the four locations with published data from a more southern area, showed that large trees (diameter at breast height, DBH, >130 cm) are present in the southern sacred forests but not in the northern forest reserves. This pattern is likely due to stronger harvesting pressure in the north compared to the south, because in the north there are no cultural taboos regulating the extraction of natural resources. The implications for forest conservation in this biodiversity hotspot are discussed.     

Genetic structure and diversity of Coscinium fenestratum: a critically endangered liana of Western Ghats,India

Coscinium fenestratum is a critically endangered medicinal plant, well-known for its bioactive isoquinoline alkaloid berberine. The species has been over harvested from its natural habitats to meet the huge requirement of raw drug market and industrial consumption. This has lead to a rapid decline in the population size and has also led to local population extinction at few locations in the Western Ghats, India. In this study, inter-simple sequence repeat markers were used to investigate the genetic variation and population structure of seven extant populations of C. fenestratum from the central Western Ghats, India. Eight primer combination produced a total of 57 unambiguous bands, of which (47.1 %) were polymorphic. The species exhibited a moderate to low level of intra population genetic diversity (H _s = 0.347 ± 0.008; H _t = 0.378 ± 0.006 (POPGENE) and H _s = 0.262 ± 0.0028; H _t = 0.204 ± 0.020 (HICKORY)). The populations were low to moderately differentiated from one another (G _ST = 0.221) and geographical distance was not significantly correlated with genetic distance, suggesting that these long-lived, geographically distant remnant populations were once connected through gene flow. There was a significant amount of genetic variation among populations (19.85 %). The Bayesian software STRUCTURE and HICKORY were used to further reveal the genetic structure of C. fenestratum. The results revealed weak population structure (K = 2) with one single widespread gene pool, and indicated that gene flow and inbreeding are likely to be the major driving force in shaping current population genetic structure of C. fenestratum. Thus, an understanding of the genetic diversity and population structure of C. fenestratum can provide insight into the conservation and management of this species.     

Genetic Structure,Diversity and Long Term Viability of a Medicinal Plant,Nothapodytes nimmoniana Graham. (Icacinaceae), in Protected and Non-Protected Areas in the Western Ghats Biodiversity Hotspot

Background and Question

The harvesting of medicinal plants from wild sources is escalating in many parts of the world, compromising the long-term survival of natural populations of medicinally important plants and sustainability of sources of raw material to meet pharmaceutical industry needs. Although protected areas are considered to play a central role in conservation of plant genetic resources, the effectiveness of protected areas for maintaining medicinal plant populations subject to intense harvesting pressure remain largely unknown. We conducted genetic and demographic studies of Nothapodytes nimmoniana Graham, one of the extensively harvested medicinal plant species in the Western Ghats biodiversity hotspot, India to assess the effectiveness of protected areas in long-term maintenance of economically important plant species.

Methodology/Principal Findings

The analysis of adults and seedlings of N. nimmoniana in four protected and four non-protected areas using 7 nuclear microsatellite loci revealed that populations that are distributed within protected areas are subject to lower levels of harvesting and maintain higher genetic diversity (H_e = 0.816, H_o = 0.607, A = 18.857) than populations in adjoining non-protected areas (H_e = 0.781, H_o = 0.511, A = 15.571). Furthermore, seedlings in protected areas had significantly higher observed heterozygosity (H_o = 0.630) and private alleles as compared to seedlings in adjoining non-protected areas (H_o = 0.426). Most populations revealed signatures of recent genetic bottleneck. The prediction of long-term maintenance of genetic diversity using BOTTLESIM indicated that current population sizes of the species are not sufficient to maintain 90% of present genetic diversity for next 100 years.

Conclusions/Significance

Overall, these results highlight the need for establishing more protected areas encompassing a large number of adult plants in the Western Ghats to conserve genetic diversity of economically and medicinally important plant species.     

Do Ecological Niche Model Predictions Reflect the Adaptive Landscape of Species?: A Test Using Myristica malabarica Lam., an Endemic Tree in the Western Ghats,India

Ecological niche models (ENM) have become a popular tool to define and predict the “ecological niche” of a species. An implicit assumption of the ENMs is that the predicted ecological niche of a species actually reflects the adaptive landscape of the species. Thus in sites predicted to be highly suitable, species would have maximum fitness compared to in sites predicted to be poorly suitable. As yet there are very few attempts to address this assumption. Here we evaluate this assumption. We used Bioclim (DIVA GIS version 7.3) and Maxent (version 3.3.2) to predict the habitat suitability of Myristica malabarica Lam., an economically important tree occurring in the Western Ghats, India. We located populations of the trees naturally occurring in different habitat suitability regimes (from highly suitable to poorly suitable) and evaluated them for their regeneration ability and genetic diversity. We also evaluated them for two plant functional traits, fluctuating asymmetry – an index of genetic homeostasis, and specific leaf weight – an index of primary productivity, often assumed to be good surrogates of fitness. We show a significant positive correlation between the predicted habitat quality and plant functional traits, regeneration index and genetic diversity of populations. Populations at sites predicted to be highly suitable had a higher regeneration and gene diversity compared to populations in sites predicted to be poor or unsuitable. Further, individuals in the highly suitable sites exhibited significantly less fluctuating asymmetry and significantly higher specific leaf weight compared to individuals in the poorly suitable habitats. These results for the first time provide an explicit test of the ENM with respect to the plant functional traits, regeneration ability and genetic diversity of populations along a habitat suitability gradient. We discuss the implication of these resultsfor designing viable species conservation and restoration programs.     

Section: bioprocessing and biological engineering gene fragment polymerization for increased yield of recombinant HIV fusion inhibitor enfuvirtide

Fuzeon (Enfuvirtide, T20) is the first fusion inhibitor approved by the FDA of the USA for the treatment of HIV/AIDS in combination with other anti-retroviral drugs. Enfuvirtide is a synthetic peptide that blocks the entry of HIV into healthy host CD₄ cells, which requires very high (90 mg twice daily) therapeutic doses. To increase the yield of Enfuvirtide, a gene polymerization strategy was introduced and recombinant T20 (rT20) was expressed in Escherichia coli as a five copy repeat polypeptide with a histidine-tag. The five copy rT20 was purified by Ni-affinity chromatography and cleaved to single rT20 units by cyanogen bromide. Finally, single rT20 units were purified by reversed phase chromatography giving a yield (400 mg/l) with a purity >95 %, which exhibited specific biological activity similar to Fuzeon.     

Development of polymorphic microsatellite loci in Nothapodytes nimmoniana, a medicinally important tree from the Western Ghats, India

Nothapodytes nimmoniana is a medicinally important tree species that occur in the Western Ghats, a megadiversity hotspot in southern India. Inner stem bark of the tree contains an important anti-cancer alkaloid, camptothecin for which the natural population of the tree is heavily harvested. In this paper, we report the isolation and characterization of eight polymorphic microsatellite loci using enrichment hybridization protocol. Analysis of 36 individuals representing two populations revealed three to 12 alleles per locus. Observed heterozygosity ranged from 0.21 to 0.94 for the two populations. None of the loci tested showed linkage disequilibrium. These markers are invaluable for evaluating the genetic structure and assessing the genetic impacts of harvesting of N. nimmoniana in the Western Ghats to formulate strategies for conservation of the species.     

Macrocyclic diterpenes from Euphorbia nivulia

The latex of Euphorbia nivulia afforded two ingol diterpenes 3,12-diacetyl-8-benzoylingol (4) and 3,12-diacetyl-7-benzoyl-8-nicotinylingol (5) along with three known ingol diterpenes 1, 2,and 3, and two known triterpenes cycloart-25-en-3beta-ol and cyclonivulinol. Their structures have been assigned on the basis of their structural data as well as their acetylated products. The diterpenes 1-5 were tested for the LPS induced PGE(2) inhibition activity.     

A new triterpenoid from the fern Adiantum lunulatum and evaluation of antibacterial activity

A new triterpenoid, 22,29xi-epoxy-30-norhopane-13beta-ol (1) was isolated together with six known compounds viz., fern-9(11)-en-6alpha-ol. fern-9(11)-ene, fern-9(11)-en-25-oic acid, fern-9(11)-en-28-ol, filicenol-B, adiantone and oxidation product of fern-9(11)-en-6alpha-ol obtained as 6-oxofern-9(11)-ene from the whole plant of Adiantum lunulatum, and their structures were elucidated by means of spectroscopic analysis and antibacterial evaluation of these compounds were conducted.