Altitudinal variation of the sex ratio and segregation by gender in the dioecious plant Mercurialis perennis L. (Euphorbiaceae) in Serbia

Abstract

The sex ratio is one of the most intriguing problems for evolutionary biologists. Spatio-temporal variation of male frequency in sexually dimorphic plant species, spatial segregation, and differential investment of the two sex functions have attracted much research interest. In this study, we examined altitudinal variation of the sex ratio and segregation by gender in Mercurialis perennis (dog?s mercury), a dioecious anemophilous species with wide distribution. The eight studied populations from Serbia represented an altitudinal range of 196 to 1480 m. Sex ratio was significantly biased in seven of the eight populations, with males outnumbering females 3.91:1 in the lowest-altitude population. Our results support the notion of spatial segregation of sexes along on altitudinal gradient: the frequency of males decreased with altitude, from 79.6% to 41.0%. The sex ratio was not significantly correlated with population density. We also examined intersexual differences of plant height in two populations from the extremes of the studied altitudinal range. Males were the larger sex in both populations, though the difference was not significant in the high-altitude population. .Jedan od najzanimljivijih problema za evolucione biologe predstavlja odnos polova. Prostorno-vremensko variranje ucestalosti muskih jedinki kod seksualno dimorfnih vrsta biljaka, prostorna segregacija i razlicito ucesce muskog i zenskog pola predmet su intenzivnih istrazivanja. U ovom radu istrazivali smo visinsko variranje odnosa polova, kao i prostornu segregaciju polova kod vrste Mercurialis perennis L., dvodome anemofilne vrste sirokog areala. Ispitali smo osam populacija u opsegu nadmorskih visina izmedju 196 m i 1480 m. Odnos polova je znacajno odstupao od 1:1 u sedam od osam populacija, sa odnosom 3,91:1 u korist muskih jedinki u populaciji na najnizoj nadmorskoj visini. Rezultati podrzavaju prethodna zapazanja o prostornoj segregaciji polova duz visinskog gradijenta: ucestalost muskih jedinki se smanjivala sa porastom nadmorske visine - od 79,6% do 41,0%. Odnos polova nije bio znacajno korelisan sa gustinom populacije. Istrazili smo i razlike u visini muskih i zenskih biljaka u populacijama sa najmanje i najvece nadmorske visine. U obe populacije muske biljke su bile vise, mada razlika nije bila statisticki znacajna u visokoplaninskoj populaciji. .