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The ecological profit in phenology and pollination of alien species Spartina alterniflora (Loisel) introduced to coastal wetlands in northern China

Shi F., Yuan Z., He K., Li J., Guo S.

Polish Journal of Ecology

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2009

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Vol. 57, nr 2

283-289

EN

For the plant species, effective phenology and pollination syndromes can increase viable seeds which enhance the species to colonize new areas. So the species with a suit of advantageous characteristics inherent in its reproductive ecology is critical to its dispersion. Spartina alterniflora - a perennial grass native to coastal marshes of America was introduced to China in 1979 and now it is distributed in the Tianjin coastal wetlands of northern China. Flowering phenology was examined and indicated that in northern localities, flowering initiated in mid-August and senescence occurred by the end of October. The pollen-ovule ratio was 9875 ([plus or minus]2150). Abundant pollen grains compensated for a lack of pollen viability. Pollen viability was 10% approximately when pollen released 4 hours, but stigma receptivity was above 10% when stigmas exserted 7 hours. Stigmas maintained viability longer than the period of pollen release, ensuring successful pollination. Scanning electron microscopy was used to observe stigma surface characters and pollen viability. Further investigation proved stigma adaptations to increase pollen capture and exterior pollen tube growth following pollination was beneficial to fertilization. The results suggested that flowering phenology and pollination traits are vital to pollination and production of viable seed, enabling the species to spread rapidly and succeed in new habitats of northern China.

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Effects of sexual reproduction on growth and vegetative propagation in Arum maculatum L. (Araceae) : in situ removal experiments

Bilgin A., Kilinc M., Kutbay H., Yalcin E., Huseyinova R.

Polish Journal of Ecology

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2009

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Vol. 57, nr 2

261-268

EN

We investigated the effects of sexual reproduction on vegetative propagation and relative somatic cost in Arum maculatum L. (Araceae). Two groups were selected as control and experimental. The spadices of individuals in experimental group were removed to test the relationship between sexual reproduction and vegetative propagation. Statistically significant differences were found between initial and final tuber weight in individuals with sexual organs removed. No significant differences were found between initial and final tuber weight in naturally reproducing (sexual organs not removed) individuals. However, the statistically significant differences were found between control and experimental group with respect to above-ground biomass but not in terms of below-ground biomass. The differences between two groups in terms of above-ground and below-ground nitrogen concentrations were also significant. Relative somatic cost of sexual reproduction (RSC) was observed in above-ground parts, but not in below-ground parts in terms of biomass and in both above- and below-ground parts in terms of nitrogen concentration.

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Parthenogenesis and gamogenesis in seasonal succession of chydorids (Crustacea, Chydoridae) in three low-productive lakes as observed with activity traps

Nevalainen L.

Polish Journal of Ecology

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2008

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Vol. 56, nr 1

85-97

EN

The aim of the present study was to determine the variance in abundance of parthenogenetic (asexual) and gamogenetic (sexual) individuals among chydorids (Crustacea, Anomopoda, Chydoridae). The chydorids were monitored quantitatively with stationary activity traps in three lakes in southern Finland at 2-week intervals during the open-water season (early May-late October) in 2006. The lakes chosen for the study were low-productive forest lakes; Lake Kalatoin was dystrophic fish-free lake and lakes Tuhkuri and Iso Lehmalampi were oligotrophic. The abundance of trapped individuals varied widely among the lakes and during the sampling period presumably due to site-specific environmental conditions (available microhabitats, food, shelter). The abundance was highest in the dystrophic Lake Kalatoin (max. 43 x 10[^3] m[^2] trapday[^-1] in June) and clearly lower in the two oligotrophic lakes (max. 8.5 x 10[^3] m[^-2] trapday[^-1] in Lake Tuhkuri in mid-July and max. 2.2 x 10[^3] m[^-2] trapday[^1] in Lake Iso Lehmalampi in mid-October). The chydorids exhibited unique sexual reproduction patterns among sampling sites and populations as the abundance of trapped gamogenetic individuals differed, suggesting habitat- and population-specific patterns in gamogenesis. In lakes Kalatoin and Iso Lehmalampi gamogenetic individuals were caught in the traps during the autumn with maxima of 2.2 and 1.6 x 10[^3] m[^-2] trapday[^-1], respectively, but in Lake Tuhkuri no gamogenetic individuals were encountered during the autumn. Although Alonella nana (Baird) was most abundantly trapped species in all the lakes, its gamogenetic individuals were trapped numerously only in Lake Kalatoin (max. ca. 1.5 x l0[^3] m[^-2] trapday[^-1]). The results suggest that gamogenesis in chydorids is a more complex phenomenon than previously believed.