Ecophysiology, growth timing and reproductive effort of three sexual foms of Corema album (Empetraceae)

Abstract

Corema album is a dioecious shrub endemic of the Iberian Peninsula, growing in sandy coastal areas from the North of Galicia to Gibraltar in the South. Hermaphrodite individuals have been found in the southern populations of El Asperillo (Spain) and Vila Real de Santo Antonio (Portugal). In this paper, the role of hermaphroditic individuals in the driest populations of its biogeographical area is discussed and the tradeoff between reproduction and vegetative growth in the three sexual forms is presented. Asperillo site where hermaphrodite individuals were more abundant was selected for this current study. The proportion of hermaphrodite individuals was 1-4%, and male/female sex ratio ranged from 0.9 to 1.1. Hermaphrodite plants had a low number of hermaphrodite inflorescences, in relation to the number of staminate inflorescences. Their ripe fruits were smaller than those of female plants. The reproductive effort was three times higher in female than in male or hermaphrodite plants. The observed interannual oscillation in vegetative elongation was not related to annual rainfall. However, differences existed in growth timing among the three sexual forms, related to the timing of peak investment in reproduction. These results suggest the existence of trade-offs between investment in reproduction and vegetative growth. There were significant differences in leaf water potential among the three sexual forms early in summer, with males showing the less negative and hermaphrodite the most negative potential values. The demand of water for fruit production may explain these differences.

Natural regeneration and gender-specific spatial pattern of Taxus baccata in an old-growth population in Foresta Umbra (Italy)

“…Males prevail under stressful circumstances in many species, even if the opposite may sometimes be observed (Freeman et al 1981;Arista et al 1997;Obeso 2002;Nuñez et al 2008). It is generally accepted that reproductive effort is higher for female than male individuals Denno 1990a, 1990b;Cipollini and Stiles 1991;Massei et al 2006;Montesinos et al 2006;Zunzunegui et al 2006), because the higher energetic costs for females result in lower yearly increments of height and stem diameter, and consequently, higher mortality under stress conditions (Sawyer and Anderson 1998;Espirito-Santo et al 2003;Massei et al 2006). Such a pattern has been found to be more frequent than the reverse in dioecious plant species, resulting in male-biased sex ratios (Faliński 1998;Bañuelos and Obeso 2004;de Jong and van der Meijden 2004).…”

Effects of pretreatments on Corema album (L.) D. Don (subsp. album) seeds' germination

“…However, 1-4% of male plants from the southwest present some hermaphrodite inflorescences [24,30]. The growing period takes place from February to July, reaching its maximum between April and June, while flowering occurs from February to April, with fruits ripening from June to September [1,25,26].…”

Do secondary sexual dimorphism and female intolerance to drought influence the sex ratio and extinction risk of Taxus baccata?

“…It is generally accepted that reproductive effort is higher for female than male individuals (Krischik and Denno 1990;Cipollini and Stiles 1991;Cipollini and Whigham 1994;Massei et al 2006;Zunzunegui et al 2006;Montesinos et al 2006). Of 41 dioecious species reviewed by Leigh et al (2006), female reproductive effort exceeded that of males in 39 cases.…”