Variranje odnosa polova, polnog dimorfizma i komponenti adaptivne vrednosti u populacijama Mercurialis perennis L. (Euphoriaceae) duž gradijenta nadmorske visine
Variation in sex ratio, sexual dimorphism, and fitness components in populations of Mercurialis perennis L. (Euphorbiaceae) along the altitudinal gradient
AuthorsJovanović, Vladimir M.
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The plant species of genus Mercurialis are very attractive object for various ecological, genetical and evolutionary researches. Dog’s mercury, Mercurialis perennis L., is a perennial anemophilous and dioecious herb, which usually grows in old and undisturbed forests. The analyses of populations of dog’s mercury from various altitudes gave us opportunity to investigate the effect of great environmental variation on morphological traits, reproductive allocation in different sexes, as well as on sex ratios in populations. This research included populations from 14 localities in Serbia sampled in 2006–2009. Statistically significant bias in sex ratio was found in 69.5% of population samples. Number of samples with biased sex ratio varied among years, and the majority of samples were male-biased. The male-biased populations of dog’s mercury were found elsewhere, and this pattern of bias is regarded to as the common one in dioecious perennials. Sexual dimorphism index for greater part of analysed traits had small to moderate values, while reproductive traits (number of flowers, mass of inflorescences) were markedly and consistently dimorphic. The range and direction of dimorphism differed in these reproductive traits. Males produced more flowers, and this information indicates pronounced intrasexual selection in males for greater pollen production. On the other hand, mass of female inflorescences was manifold bigger than mass of male inflorescences, and female reproductive allocation was bigger in a similar manner. In females, we also found pattern of decrease in reproductive allocation with the increase of altitude. The analyses of sexual dimorphism in plant size showed that males were the higher sex in majority of population samples. This is in agreement with pollen-dispersal hypothesis. The statistical regression models of spatial and temporal variation of sex ratio and reproductive allocation were created by generalized least squares method. Among these models, the best-fitting ones were selected by contemporary statistical inference. The proportion of male plants in population decreased with increasing altitude in the whole sample, as well as in the samples from different years. The bias direction therefore changed from male-biased in the lowland populations to female-biased in the higher altitudes. The environmental stress is more pronounced in the higher altitudes, and according to sex allocation theory this would lead to male-bias in the population. The female-biased sex ratio in populations of M. perennis in higher altitudes could be the adaptive response. Statistical models showed the significance of altitude and vegetation season in two ways: through affecting the mean of male plant proportion, as well as through affecting the variance of this proportion. The factors that showed significance in statistical models of reproductive allocation indicate the existence of difference in selective pressures on sexes. Only female plants were sensitive to sex ratio, with reducing reproductive allocation when there is smaller proportion of males in the population. Cytogenetic polymorphism is very expressed in M. perennis – more then 40 cytotypes were described so far, ranging from 42 to 112 chromosomes. In analysed populations from Serbia, the great cytogenetic variability was also found. There were 23 out of 47 cytotypes described in Europe and almost whole range of reported chromosome numbers. Populations from higher altitudes exert higher ploidy levels. Phylogenetic and historical biogeographic analysis indicated divergence time of genus Mercurialis from the rest of the subfamily Acalyphoideae to approximately 65-66 Mya, centre of the genus origin was defined in Indomalaya and plesiomorphism of dioecious sex system was confirmed.
Keywords:Mercurialis perennis, sex ratio, sexual dimorphism, reproductive allocation, evolutionary ecology, cytogeography; Mercurialis perennis; Sex ratio; Sexual dimorphism; Reproductive allocation; Evolutionary ecology; Cytogeography
- Evolucija u heterogenim sredinama (RS-143040) (-)
Belgrade: University of Belgrade, Faculty of Biology (2012): 1-144[ Google Scholar ]
APA:Jovanović, V. (2012). Variranje odnosa polova, polnog dimorfizma i komponenti adaptivne vrednosti u populacijama Mercurialis perennis L. (Euphoriaceae) duž gradijenta nadmorske visine. University of Belgrade, Faculty of Biology. p. 144.
Vancouver:Jovanović V. Variranje odnosa polova, polnog dimorfizma i komponenti adaptivne vrednosti u populacijama Mercurialis perennis L. (Euphoriaceae) duž gradijenta nadmorske visine [dissertation]. Belgarde: University of Belgrade, Faculty of Biology; 2012. 144 p.
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