Frequency-dependent pollinator discrimination acts against female plants in the gynodioecious Geranium maculatum
Gynodioecy, the co-occurrence of female and hermaphroditic individuals, is thought to be an intermediate step between hermaphroditism and separate sexes, a major transition in flowering plants. This paper suggests that suggest that pollinator discrimination negatively affects females’ relative fitness when they are rare. Thus the initial spread of females in a population, the first step in the evolution of gynodioecy, may be made more difficult due to pollinator discrimination.
Factors affecting stress tolerance in recalcitrant embryonic axes from seeds of four Quercus (Fagaceae) species native to the USA or China
Oaks (Quercus species) are often considered ‘foundation’ components of temperate and/or subtropical forest ecosystems. However, the populations of some species are declining and there is considerable urgency to develop ex situ conservation strategies. In this study, the storage physiology of seeds within Quercus was explored in order to determine factors that affect survival during cryopreservation and to provide a quantitative assessment of seed recalcitrance to support future studies of this complex trait.
Multiple origins of circumboreal taxa in Pyrola (Ericaceae), a group with a Tertiary relict distribution
Two major categories of Northern Hemisphere intercontinental disjunctions are Tertiary relict disjunctions and circumboreal distributions. Tertiary relict disjunctions tend to be older and involve groups from warm temperate to sub-tropical regions, reflecting the warm climates of the Tertiary epoch. Conversely, circumboreal distributions typically involve cold temperate to Arctic-Alpine species, and tend to be younger, reflecting the recent development of these biomes due to global cooling over the past 5 million years. This paper reconstructs the biogeographic history of Pyrola based on a clear phylogenetic analysis and to explore how the genus attained its circumboreal distribution.