Daniel Barranco Álvarez. University of Seville. Supervisors: Juan Arroyo, Rocío Santos Gally & Violeta Simón Porcar. Start in 2015.
Summary:
Style polymorphic Narcissus species often display spatial
variation among populations in morph-ratio and perianth traits.
Deterministic and stochastic processes may play a role in this
variation. For example, morph-ratio variation in Narcissus may result
from morph-specific differences in the rates of selfing, and assortative
and dissasortative cross-pollination in populations. All of these
crosses are possible because polymorphic species are characterized by
the absence of an intra-morph incompatibility system and some are also
self-compatible. Pollinator shifts have also been useful to understand
variation in morph ratio across populations. Furthermore, historical
stochastic factors (i.e. founder events, drift) can account for
population structure. Detailed understanding of the maintenance of
morphs requires thorough investigation across the species’ range, which
is rarely achieved in widespread species. Here we analysed the influence
of historical stochastic factors (phylogeography) and deterministic
factors (pollinators and incompatibility systems), on the morph-ratio
variation among populations of four Narcissus species (N. assoanus, N.
dubius, N. rupicola and N. cuatrecasasii). The historical factors have
been determined through Bayesian phylogeographic analyses. We used
plastid sequences from a total of 193 populations. Pollinator
environment was studied by means field observations. We determined
visitation rates of pollinators in two representative populations of
each species which have differences in the morph-ratio. Finally, the
incompatibility system was determined from published and experimental
data. This work will show the relative relevance of different factors
(i.e. historical, ecological and genetic) on the stylar-polymorphism
maintenance and morph-ratio variation across populations.