Is intraspecific trait differentiation in Parthenium hysterophorus a consequence of hereditary factors and/or phenotypic plasticity?

Of the various strategies adopted by an invasive plant species for expanding its niche breadth,phenotypic differentiation(either due to plasticity and/or adaptive evolution) is proven to be the most successful.Lately,we studied the persistence of substantial morpho-functional variations within the individuals of alien invasive plant,Parthenium hysterophorus in Chandigarh,India,through field surveys.Based on observed differences,the individuals were categorized into two morphotypes,PAand PB.PAhad higher leaf area,leaf biomass,and chlorophyll content as compared with PB.However,PBhad a higher stem circumference,stem specific density,twig dry matter content,profuse branching,bigger canopy,and better reproductive output than PA.To substantiate the persistence of intraspecific variations in P. hysterophorus and to deduce the possible genesis of these variations,we propagated both the morphotypes under experimental conditions in winter and summer.Apart from the key morpho-functional differences observed during the field studies,protein and carbohydrate metabolism were studied in leaves and roots of the propagated plants.Differences in plant metabolism were observed only during the early growth period,whereas the morpho-functional traits varied in the mature flowering plants.The effect of growth season was highly significant on all the studied morpho-functional and biochemical parameters(p ≤0.05).Parent morphotypes(P) and interactions between morphotypes and seasons significantly affected several growth parameters(p ≤0.05).The analyses revealed that the contrasting growth conditions at the time of transplantation and early growth may regulate the phenotype of P. hysterophorus.The pattern of intraspecific variations observed during the study is justified to consider morphotype PAas winter biotype and morphotype PBas summer biotype of P. hysterophorus.The study points towards the role of plasticity or a combination of genetic and environmental(G×E) factors in producing the phenotypic variability observed in the population of P. hysterophorus.

Using a Macroalgal Functional Form Approach to Assess the Level of Disturbance of Seagrass Meadows in Bahía of Nuevitas,Cuba(2000-2002)

A study on the spatial and seasonal variations of the associate macroalgae and epiphytes of Thalassia testudinum was carried out in Bahía de Nuevitas. Sixty-two species were identified: 3 Cyanophyta, 25 Chlorophyta, 8 Phaeophyceae, 23 Rhodophyta and 3 Magnoliophyta, with two new records for Cuba and 43 for the area. The differences in the specific composition of the macroalgae communities are determined by a space component related to the type of affectation in each area. The morpho-functional groups of macroalgae in the station with more nutrient influence were mainly foliaceous and filamentous. In the stations far from the city, the predominant morpho-types were the leathery and articulate calcareous indicators of lower nitrification levels. The abundance and diversity of macroalgae in the site affected by fisheries were lower due to the damage by bottom trawls. Seasonal variations were found in the relative abundance of the species, not in the diversity, which makes evident seasonal changes in the structure of the seaweeds, where some species replace others in the community.