Biology Reference
In-Depth Information
linated herb Silene latifolia, by investigating floral signals (floral display and
fragrance) and conducting behavioral experiments with the pollinator-moth,
Hadena bicruris.
Results
As found in previous studies, male plants produced more but smaller flowers.
Male flowers, however, emitted significantly larger amounts of scent than fe-
male flowers, especially of the pollinator-attracting compounds. In behavioral
tests we showed that naïve pollinator-moths preferred male over female flow-
ers, but this preference was only significant for male moths.
Conclusion
Our data suggest the evolution of dimorphic floral signals is shaped by sexu-
al selection and pollinator preferences, causing sexual conflict in both plants
and pollinators.
Background
According to sexual selection theory, males compete with each other over access
to females since the reproductive success of a male is limited by the number of fe-
males he can fertilize, whereas female reproductive success is limited by resources
available for producing offspring [1,2]. In plants, access to pollinators should
therefore limit the reproductive success of males to a greater extent than it restricts
the reproductive success of females [3-5]. Consequently, different selection pres-
sures are expected to act on males and females, resulting in male-male competi-
tion over mates [1].
The majority of plants rely on pollinators for successful pollen transfer [6].
Prefertilization-competition among male gametophytes has been described
as pollen competition within the female organs [7], which can be influenced
through physiological interactions with the pistils [8]. However, pollinator at-
traction is the first step in the reproductive cycle of animal-pollinated plants
and in dioecious species, sexual reproduction is impossible without the trans-
fer of pollen from male to female flowers. In contrast to most other plants
that have hermaphroditic flowers, males and females can respond differently
to pollinator-mediated selection. In this situation, selection may hence favor
traits that improve pollination and fertilization success, which may lead to
sexual dimorphisms in pollinator attracting traits rendering male flowers more
attractive than females since access to mates is a function of access to pollina-
tors [4,9,10]. In addition, natural selection on females should reduce attrac-
tiveness, since besides pollinators, floral signals also attract granivores that can
