Work Package 3:
Coevolution, Invasion and Plant Conservation Biology
15 researchers
COORDINATORS Isabelle Olivieri (UMR 5554 CNRS Montpellier) and Bruce Anderson (Department of Botany and Zoology, University of Stellenbosch)
Project
1: Gene flow, life-histories and
sexual dimorphism in plants of a fynbos endemic plant genus, Leucadendron (Proteaceae).
Participants : Isabelle Olivieri, Agnès Mignot,
Ophélie Ronce, Sandrine Maurice, Emmanuel Douzery (UMR 5554 CNRS, Montpellier),
Tony Rebelo (Kirstenbosch Botanical
Garden, Rondebosh), Jeremy Midgley, Nicola Illing (University of Cape Town)
The genus Leucadendron is made of 96 taxa, half of which are
threatened (two already extinct). This genus is highly diversified from the
point of view of its ecology, mating sysem, dispersal structures, adaptation to
fire. For instance some species have diaspores dispersed by ants, others by
wind (wings or parachutes), others just roll on the soil thanks to hairs. Some
species are polymorphic for seed coat or flower colour, others possess
different types of dormancy (serotinous species which seed dispersal only
occurs after a fire, or soil seed bank with germination induced by fire).
Pollination is either insect or wind mediated. All species are dioecious, but
they present various degrees of sexual dimorphism.
We now have collected several individuals of most taxa, and are about to
sequence the whole transcriptome for three of them, plus two outgroup species.
This will allow us to design ca. 30 molecular primers specific to the genus and
related genera, that will be very useful to reconstruct the molecular phylogeny
of the genus (the one presently available is not robust at all, and botanists
strongly disagree with it), hence addressing questions about macroevolutionary
patterns of life-history evolution.
Thanks to the molecular markers that we have now developed (microsatellites)
we will address a number of questions relative to speciation process, and the
ecological and evolutionary significance of sexual dimorphism. We will for
instance determine both pollen and seed dispersal kernels in species differing
by their amount of sexual dimorphism.
Using common garden experiments, we will compare various quantitative
traits and molecular diversity of several populations of two species, closely
related on the available phylogeny, but very different for life-histories, and
for the amount of phenotypic diversity. This will allow us to address questions
about the first step of potential ecological speciation
Finally, modelling the evolution of resource allocation to growth,
survival and reproduction, we will ask about the role of the fire regime in
determining the optimal life-history, and about the ecological and evolutionary
consequences of changes in the fire regime.
Project
2 : Pollination-induced speciation in plants.
Participants : Isabelle Olivieri (UMR 5554 CNRS, Montpellier), Bruce
Anderson, Anton Pauw (University
of Stellenbosch).
One particularly attractive hypothesis to explain the extraordinary
speciation rates in the south-african fynbos, is that soil substrate or
climatic factors governs the distribution of pollinators, which then governs
the amount of gene flow among populations. In the genus Leucadendron and
Hemimeris, parapatric populations occur on different substrates. There
is some evidence that in Leucadendron salignum, different flower
colours, occuring mostly in parapatric situations, are associated to different
pollinators, both soil types and climatic adaptation seem to be involved.
Populations of Leudadendron platyspermum and of L. meridianum
also occur on parapatry on very different soil types, and are both insect
pollinated, but which pollinators occur is unknown. Could they help reinforce
the local adaptation pattern likely to occur on such different substrates? In Hemimeris racemosa, there is
also some evidence that populations are normally outcrossing, but that
populations occuring on sand have lost self-incompatibility dimorphism and
instead have evolved towards selfing. This could be due to a change in the type
of pollinators. If such soil substrate differences is indeed at the origin of
speciation mediated by pollinator types or availability, one expect such
evolution of reproductive isolation to often occur. Therefore, evolution
towards self-compatibility and selfing is expected to have evolved several
times. This should translate into parapatric populations on different soil
types to be more related than allopatric populations. In order to distinguish
between current gene flow and recent common origin, we will compare genetic differentiation
among populations of Hemimeris racemosa.
Project 3 : The Ficus-fig-wasp association: a model system to investigate
coevolutionary processes.
Participants : Finn Kjellberg, Martine Hossaert-McKey (CEFE UMR
5175, Montpellier), Jean-Yves Rasplus (CBGP UMR 1062, Montpellier), Simon
van Noort (IZIKO museum), Michael McLeish (University of Stellenbosch), Jaco
Greeff (University of Pretoria).
Ficus (Moraceae) produce closed,
urnshaped-inflorescences, called figs, the inside of which is lined by flowers.
They are exlusively pollinated by Agaonid wasps (hymenoptera, chalcidoidea)
that enter figs to oviposit. Each Ficus
species is pollinated by one or a few generally species specific Agaonid wasps.
Further a number of chalcid wasp species belonging to different families may
parasitize the fig-pollinating wasp association. Some gall female flowers, some
use galls initiated by other wasps, some are parasitoids and some may even
consume seeds. Most of these wasps oviposit from outside figs, but some may
enter the figs as pollinators. Most of these wasp species are assumed to
specialize on a single host. There are over 750 species of Ficus distributed worldwide constituting a fantastic model to
investigate the evolutionary history of 750 separate micro-hymenopteran
communities.
The participants are involved in a long term
joint research effort that will be facilitated by the GDRI. The study is aimed
at understanding how and why the Ficus-fig-wasp
system diversified. We are progressively revising the taxonomics of fig wasps
and Ficus on a worldwide basis. We
are also involved in a large joint long term phylogenetic project the aim of
which is to understand how the communities diversified. We are studying the
biology of the system in order to understand the ecological determinants of
community structure.
The participants are involved in a global
worldwide perspective but they also focus specifically on Africa. Indeed, in
Africa there seem to be an exceptional diversity of cases of one wasp visiting
several host Ficus and one Ficus being visited by several agaonid
wasps. To unravel this situation we are building on a phylogeographic approach
all over Africa and on more specific local studies on the biology of the
interactions, especially in South Africa.
The participants are progressively developing
the website, http://www.figweb.org/, which aims at providing worldwide information
for the identification of all Ficus
and fig wasp species. The aim is to show that it is feasible to provide
complete identification assistance, including morphological and molecular data
to identify all members of these communities, i.e. for about 10000 species.
Figweb is hosted at Iziko museums, Cape Town, with a mirror site at CBGP,
Montpellier.
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