Tagged: dioecy






Many coloured bands

Patterns of sex expression, health and mortality in a sex-changing tree

The ability of individuals to change sex during their lifetime is known as environmental sex determination (ESD). This ability represents a unique life history trait, allowing plants to allocate resources differentially to male and female functions across lifetimes, potentially maximizing fitness in response to changing environmental or internal cues. Blake-Mahmud and Struwe investigated Acer pensylvanicum, a species with an unconfirmed sex determination system, to see what patterns in sex expression existed across multiple years, if there were sex-based differences in growth and mortality, and whether this species conformed to theoretical predictions that females are larger and in better condition. In...

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Diagram of the breeding system

Breeding system evolution in Ficus and Moraceae

Diverse breeding systems have evolved in angiosperms from the bisexual flowers of their last common ancestor. However, breeding system evolution remains poorly understood in many plant families, including the Moraceae (figs and mulberries). In this paper, Zhang et al. address these questions using a state-of-the-art new dated phylogeny for Moraceae and, for the first time, model-based methods for ancestral state reconstruction. They find very strong support for ancestral dioecy in Moraceae, and show that monoecy was probably an intermediate step towards gynodioecy in Ficus. These results have significant implications for understanding the evolutionary origin of figs as well as breeding...

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Images of the typical (male) plant phenotype at each of the four growth stages studied.

Sexual dimorphism and rapid turnover in gene expression in pre-reproductive seedlings of a dioecious herb

Sexual dimorphism in morphology, physiology or life history traits is common in dioecious plants at reproductive maturity, but it is typically inconspicuous or absent in juveniles. Although plants of different sexes probably begin to diverge in gene expression both before their reproduction commences and before dimorphism becomes readily apparent, it seems transcriptome-wide differential gene expression has yet to be demonstrated for any angiosperm species. Cossard, Toups and Pannell document differences in gene expression in both above- and below-ground tissues of early pre-reproductive individuals of the wind-pollinated dioecious annual herb, Mercurialis annua, which otherwise shows clear sexual dimorphism only at the...

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Shrubs

Positive and negative interactions on a dioecious grass species performance

Dioecious plants are of particular concern in view of global environmental changes because reproductive females are more sensitive to abiotic stresses, thus compromising population viability. Positive interactions with other plants may counteract the direct effects of any abiotic environmental stress, allowing them to thrive and maintain a viable population in suboptimal habitats, although this process has not been tested for dioecious species. Furthermore, almost no data are available on the outcome of such species interactions and their link with local spatial patterns and sex ratios. Graff et al. find that facilitation, mediated by shrub canopies, help females of the native...

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Yew

Limited seed and pollen gene dispersal in Taxus baccata

Dispersal is crucial due to its direct impact on dynamics of a species’ distribution as well as having a role in shaping adaptive potential through gene flow. In plants forming scarce and small populations, knowledge about the dispersal process is required to assess the potential for colonizing new habitats and connectivity of present and future populations. Using molecular data and the modelling approach, Chybicki and Oleksa estimate dispersal potential in Taxus baccata (Taxaceae), a dioecious tree with a highly fragmented distribution. They find that yew seeds travel shorter distances than pollen, facilitating a rapid development of a kinship structure within...

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Sex-specific functional traits in cycads

The Mesozoic is often referred to as the “age of cycads”. During this period, dinosaurs roamed vast cycad forests, yet modern cycads are a vestige of their Mesozoic glory. Extant species represent the oldest lineage of dioecious seed-bearing plants. This curious phylogenic position is matched by their unusual ecology: most species are extremely rare while others form dense colonies that may play important roles in forest function. In spite of this and quite remarkably, cycads are the most poorly studied lineage of seed plants and almost nothing is known of their ecophysiology. A study published in AoB PLANTS by Krieg...

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Amborella trichopoda

Genetic sex determination and sexual instability in Amborella trichopoda

Amborella trichopoda, the sister species of all other extant angiosperms, is typically dioecious, producing male and female flowers on separate individuals. Anger et al. map sex phenotypes onto a phylogeny of basally diverging angiosperms using maximum parsimony. Sex-ratios and phenotypes were studied in parallel over two consecutive flowering seasons for an ex situ population of A. trichopoda. The sex-ratio of an in situ population was also assessed. The results show that the primary male-female ratio in A. trichopoda is 1:1, suggesting a genetic mechanism of sex determination, however, male-biased sex ratios were evident in natural populations. Rare sex-change events were...

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High male fertility in males of a subdioecious shrub

Female reproductive success in females versus hermaphrodites has been well documented. However, documenting a potential advantage in fertility of male versus hermaphrodite individuals in subdioecious species is also essential for understanding the evolutionary pathway from hermaphroditism toward dioecy via gynodioecy. In a recent study published by Wang et al. in AoB PLANTS, siring success in terms of fruit set, fruit mass, number of seeds, and mean seed mass was compared by hand-pollinated crosses in the subdioecious shrub Eurya japonica. Male individuals exhibited an advantage in male fertility in terms of both quantity and quality compared with hermaphrodites in hand-pollinated crosses...

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