Manzoor A. Shah

Arbuscular Mycorrhizas: Drivers or Passengers of Alien Plant Invasion

Observational and manipulative studies have revealed that alien plant invasions are an outcome of interplay between a myriad of biotic and abiotic factors operating at various spatio-temporal stages and scales. Despite the salient role of ubiquitous arbuscular mycorrhizal (AM) fungi in plant interactions, studies exploring the role of such symbionts in invasiveness of alien species and invasibility of communities are limited, in part because of difficult-culturablilty of AM fungi on artificial media and apparent complexities in manipulations of AM-plant interactions in field and laboratory experiments. Moreover, analysis of the AM-plant invasion studies conducted so far have yielded contradictory results with some indicating facilitation of invasion by AM fungi and others its inhibition. Other studies have indicated that arbuscular mycorrhizal symbiosis has no effect on invasiveness of alien plants. While arbuscular mycorrhizas may facilitate invasiveness of some alien plants, such plants may also potentially impact mycorrhizal community structure and functions in the invaded habitats in different ways. The present review addresses these paradoxically conflicting observations in the context of mutualism-commensalism-parasitism gradient that characterizes the relationship between AM fungi and their alien vs. native hosts and also discusses the influence of alien invasive plants on mycorrhizal community structure of invaded ecosystems. Through critical analysis of costs and benefits for invasive plants that associate with AM fungi in their introduced range, invasion-induced shifts in AM mutualism are evaluated in the context of their impact on native biodiversity. Underlining limitations of methodologies and experimental designs usually employed to understand AM-mediated plant invasiveness, we proposes herein some alternative frameworks and experimental approaches to overcome these limitations.

Conyza canadensis suppresses plant diversity in its nonnative ranges but not at home: a transcontinental comparison.

The impact of invasive species across their native and nonnative ranges is poorly quantified and this impedes a complete understanding of biological invasions. We compared the impact of the native North American plant, Conyza canadensis, which is invasive to Eurasia, on species richness at home and in a number of introduced regions through well replicated transcontinental field studies, glasshouse experiments and individual-based models. Our results demonstrated mostly negative relationships between C. canadensis abundance and native species richness in nonnative ranges, but either positive or no relationships in its native North American range. In glasshouse experiments, the total biomass of Conyza was suppressed more by species from its native range than by species from regions where it is nonnative, but the effects of Conyza on other species did not show a consistent biogeographical pattern. Finally, individual-based models led to the exclusion of Conyza from North American scenarios but to high abundances in scenarios with species from the nonnative ranges of Conyza. We illustrate biogeographical differences in the impact of an invader across regional scales and suggest that inherent differences in one specific aspect of competitive ability, tolerance to the effects of other species, may play some role in these differences.

Mycorrhizosphere mediated Mayweed Chamomile invasion in the Kashmir Himalaya, India

Recent studies have established the controlling influence of rhizospheric biota, especially arbuscular mycorrhizal fungi (AMF), on colonization and spread of some alien plants in their introduced range. But how AMF from different geographical sources influence traits that contribute to invasiveness, particularly in presence of neighbouring plants of other species, has been rarely investigated. Thus, we compared the influence of some local (Kashmir Himalayan isolates) and non-local (isolates from Rajasthan, India) AMF isolates of Glomus moseae, G. fasciculatum and Gigaspora margarita on vegetative and reproductive attributes of Mayweed Chamomile (Anthemis cotula L.), a highly invasive species in the Kashmir Himalaya, India. We also examined whether or not the neighbouring plant species, namely Daucus carota L. (Apiaceae) alters the mutualistic interaction between the AMF and A. cotula. Pot experiments revealed greater positive impact of the local than the non-local AMF on vegetative as well as reproductive attributes of A. cotula. Experimental field studies showed that the incidence of highly prevalent Arum-type mycorrhizal colonization in natural populations of A. cotula was reduced in presence of D. carota. Besides, the local AMF significantly promoted growth of A. cotula more than D. carota under mixed-culture conditions. These results suggest that the facilitation of some alien plant invasions by AMF needs to be considered together with plant–plant interactions and invasion-induced changes in the soil microbial community.

Aquatic bacterial diversity: Magnitude, dynamics, and controlling factors

The primary aspiration in the microbial observatory is to advance the understanding of freshwater bacterioplankton, whose diversity and population dynamics are currently the least understood off all freshwater planktonic organisms. Through identification and characterization of bacterial populations in a suite of fresh water bodies, we are able to gain significant new insight into the ecological niches of bacteria in diverse freshwater ecosystems. Given the facts that lakes and other inland freshwaters play a more critical role in the global carbon budget and that lakes have been described as early indicators of both regional and global environmental change, the role of microbes in these processes is of renewed interest. In this review, general overview will be given highlighting the characteristic features of bacterial species thriving in different water bodies. In the following sections, different cultural approaches vis a vis the controlling factors of bacterial diversity have been elaborated. In the concluding sections, the prospects of aquatic microbial diversity are well mentioned.

Functional Promiscuity of Two Divergent Paralogs of Type III Plant Polyketide Synthases

Evolutionary and functional divergence of gene paralogs expressing polyketide synthases from Rheum emodi play into secondary metabolism and substrate selectivities. Plants effectively defend themselves against biotic and abiotic stresses by synthesizing diverse secondary metabolites, including health-protective flavonoids. These display incredible chemical diversity and ubiquitous occurrence and confer impeccable biological and agricultural applications. Chalcone synthase (CHS), a type III plant polyketide synthase, is critical for flavonoid biosynthesis. It catalyzes acyl-coenzyme A thioesters to synthesize naringenin chalcone through a polyketidic intermediate. The functional divergence among the evolutionarily generated members of a gene family is pivotal in driving the chemical diversity. Against this backdrop, this study was aimed to functionally characterize members of the CHS gene family from Rheum emodi, an endangered and endemic high-altitude medicinal herb of northwestern Himalayas. Two full-length cDNAs (1,179 bp each), ReCHS1 and ReCHS2, encoding unique paralogs were isolated and characterized. Heterologous expression and purification in Escherichia coli, bottom-up proteomic characterization, high-performance liquid chromatography-electrospray ionization-tandem mass spectrometry analysis, and enzyme kinetic studies using five different substrates confirmed their catalytic potential. Phylogenetic analysis revealed the existence of higher synonymous mutations in the intronless divergents of ReCHS. ReCHS2 displayed significant enzymatic efficiency (Vmax/Km) with different substrates. There were significant spatial and altitudinal variations in messenger RNA transcript levels of ReCHSs correlating positively with metabolite accumulation. Furthermore, the elicitations in the form of methyl jasmonate, salicylic acid, ultraviolet B light, and wounding, chosen on the basis of identified cis-regulatory promoter elements, presented considerable differences in the transcript profiles of ReCHSs. Taken together, our results demonstrate differential propensities of CHS paralogs in terms of the accumulation of flavonoids and their relative substrate selectivities.

Isolation, Identification and Distribution of Culturable Bacteria in Manasbal Lake, Kashmir Himalaya

Bacteria comprise an important part of the aquatic microbial flora and perform myriad of ecological roles in aquatic ecosystems. Yet the bacteriological studies on aquatic ecosystems are scarce, especially in the Himalayan context. The main objective of present study was to assess the bacteriological composition of Manasbal lake, the deepest freshwater lake of Kashmir Himalayas, in relation to anthropogenic pressures. The authors measured abundance of the culturable bacteria in lake waters from March to December 2011 using culture based approaches. A total of 1391 different colonies of the identified bacterial strains were obtained from the lake waters with significant site specific variability. The data indicated that the colony number was highest for site II (surrounded by residential hamlets) followed by site I (an irrigational stream) and III (Central site) and lowest for site IV (Outlet). The strains were identified using the gram’s staining, motility test and biochemical tests. Data revealed a highest percentage occurrence of 14.67 % for Proteus II and lowest of 0.21 % for Shigella I. This study indicated the need for development of a feasible system with regular assessment of microbial population for ascertaining the proper microbial load in order to effectively combat the multiple dangers of anthropogenic pollution of the lake.

A cross-city molecular biogeographic investigation of arbuscular mycorrhizas in Conyza canadensis rhizosphere across native and non-native regions

IntroductionThe ecological processes underlying the suppressive impacts of invasive species on native species diversity, both above- and below-ground, in non-native regions are not well understood. We therefore aimed to investigate the cross-city biogeographic patterns of arbuscular mycorrhizal (AM) diversity in Conyza canadensis rhizosphere in native (North American) and non-native (Kashmir Himalayan) regions.MethodsWe recovered AMF spores from rhizospheric soils of Conyza in native and non-native ranges, besides doing so from the uninvaded sites in the introduced region. DNA extracted from AMF spores was processed for cloning and PCR-RFLP of SSU rRNA gene to yield the restriction groups (RGs) followed by their sequence analysis to determine the sequence groups (SGs).ResultsThe results indicated greater diversity of RGs and SGs in Conyza rhizosphere in native than in non-native sites. In the introduced region, however, the AMF diversity was more in uninvaded than in invaded sites. The species composition of AMF varied significantly between native and non-native regions and so also between invaded and uninvaded habitats.ConclusionsThough difference in AMF diversity between Conyza invaded and uninvaded sites may be attributed to invasion, the role of other evolutionary factors seems likely for differences between the native and non-native regions. We suggest that the ecological processes underlying these evolutionary differences in two biogeographic regions, besides the intensity of urbanization, might play some role in these differences.

Invasive species: reality or myth?

In view of the recent debate on the future of invasion biology, we argue that species could be regarded as invasive only when after adaptation in non-native habitats they reach yet another fitness maximum. We suggest that invasion biologists need to unambiguously clarify what constitutes being “invasive” to refute those who call for an end to invasion biology.

Studying the patterns of alien and native floras of some habitats in Srinagar city, Kashmir, India

IntroductionUrban flora is an important component of human-dominated ecosystems that links urban dwellers with nature. This study aims at compiling and analysing the alien and native vascular plant species of some selected habitats in the Srinagar city, Kashmir, India.MethodsBi-seasonal sampling was employed and each habitat type (viz., graveyards, grasslands, orchards and wastelands) was sampled at seven different sites.ResultsThe number of species recorded from graveyards was 96; from grasslands 112; 141 from orchards and 110 from wastelands. The level of invasion among habitats varied from 67.27% to 68.75%, with a mean value of 67.86%; out of clubbed species list, 64.84% were alien. Asteraceae, Poaceae, Brassicaceae and Fabaceae were the biggest families in all four habitat types.ConclusionsOur research shows that across habitats, alien plant species are the predominant part of their floras.

Mycorrhizas in Aquatic Plants

In contrast to widespread occurrence of arbuscular mycorrhizas (AM) in terrestrial plants, aquatic plants are considered to be relatively less mycorrhizal. It is mainly because the benefits of mycorrhizal association to plants under aquatic conditions are expected to be relatively lesser. It is, however, hard to accept these generalised perceptions, partly because only a few studies have been hitherto carried out on mycorrhizal symbioses of aquatic plants, thereby leaving huge information gaps and paucity of quantitative data in this area of research. The cost–benefit analysis of mycorrhizal associations with aquatic plants has been relatively much less explored mainly because of more challenging methodological issues. The present chapter begins with a brief outline of aquatic habitats, followed by an overview of the studies conducted so far on mycorrhizal association of aquatic plant species with the main objective to identify key knowledge gaps in this area of research. Finally, the important questions that merit attention by future researchers to get better insights into mycorrhizal symbioses in aquatic habitats are highlighted, and a conceptual framework to address these questions is also provided (Fig. 8.1).