Nové poznatky o biologii pcháče žlutoostenného (Cirsium brachycephalum)
| Title in English | New data on biology of yellow-spine thistle (Cirsium brachycephalum) |
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| Year of publication | 2012 |
| Type | Conference abstract |
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| Description | Cirsium brachycephalum is the Pannonian endemic. It is a subhalophilic, monocarpic, and less competitive species, which is threatened by extinction (in the CR critically endangered species C1). Its populations contain two sexes: females and hermaphrodites (= gynodioecy). In the years 2010-12, we analyzed the sex ratio in 23 populations in Moravia, Slovak Republic, Hungary and Austria. Population size (number of plants) and their density; vegetation composition, salinity were also recorded in the populations; and subsequently also the number, weight and germination of achenes in both sexes. We found that, compared with the other gynodioecious thistles in Central Europe, Cirsium brachycephalum has the highest proportion of females in the population (33-97%). The median proportion of females in populations fluctuated annually between 61-63%. The proportion of females in the population did not change significantly between the seasons, although each of them represents a completely different set of individuals (monocarpy). The proportion of females in the populations correlated positively with the degree of salinity. Females had more and heavier achenes than hermaphrodites. Female fertility was negatively correlated with the share of females in the population = female fertility is limited by the availability of pollen (from hermaphrodites). Compared to other thistles, Cirsium brachycephalum is very interesting by its "risky" life strategy, which combines almost incompatible: monokarpy and gynodioecy with the high proportion of females and hermaphrodites low fertility. Populations of this species growing in more salinic habitats have a higher proportion of female plants, which supports the "Sex-differential plasticity" hypothesis. |
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