Research Interests
During my post-doc, I have been pursuing the following lines of research:
- phylogeny
of Cyprinidae and Blenniidae
- morphological
evolution and morphological integration in Cyprinidae and Bleniidae
- phylogeography
of North Atlantic and Mediterranean species
- phylogeny of Narcissus
For more details on my post-doc work, see my website at ISPA.
During my PhD, I pursued a few lines of research:
- Selection
for resistance to Pieris rapae
- Selection
for resistance to Alternaria brassicicola
-
Selection for anthocyanin expression
- Pupal color
polymorphism in P. rapae
- Leaf
shape evolution
- Evolution
of insect feeding preferences
My main research interest is community genetics, i.e. the genetics of biotic interactions and their ecological and evolutionary consequences, in particular that of interactions between plants and their insect and microbial enemies. Are geographical ranges of plants influenced by their enemies, and vice-versa? How important is the role of plant enemies in determining plant community composition? Is the evolution of plant traits such as flower morphology, phenology, or chemistry effected by selection pressures exerted by plant enemies?
The
objective of my PhD thesis project is to study patterns in resistance to different
plant enemies, using Rapid-cyling
Brassica rapa (Brassicaceae) as a model system. Plants face
a diversity of natural enemies, including vertebrate and invertebrate herbivores,
and bacterial, viral, and fungal pathogens. These can exert selection
pressure on plant traits. It is yet unclear, however, whether plants adapt in
a pair-wise fashion to specific enemies, or if selection pressures exerted by
different enemies are interdependent such that plants respond nonspecifically.
Interdependency of selection pressures may arise due to genetic correlations
in plant resistance to different enemies. The short generation time and high
fecundity of rapid-cycling Brassica make it ideal for studies of experimental
evolution that address this issue. I have been attempting to artificially selecting
populations of B. rapa for resistance against larvae of Pieris rapae
(a Pierid specialized on Brassicaceae) and of Trichoplusia ni (a generalist
noctuid). For more detailed information please see my PhD
thesis.
I have also made available the rearing procedures I used for P.
rapae and T. ni.
Selection for resistance to Pieris rapae
Populations of Rapid-Cycling Brassica rapa were
selected in two directions, for resistance and susceptibility to first instar
larvae of Pieris rapae. Larvae were placed onto 12-day old plants and
left to feed for 72 h. Damage was scored using a grid-square (4mm2
units). After three generations of selection, treatments differ regarding damage
inflicted by larvae. This was particularly satisfying as I had previously conducted
artificial selection, for 7 generations, using 3rd instar larvae, but to no
effect. I am in the process of evaluating whether populations differ the their
resistance to other enemies.
Selection for resistance to Alternaria
brassicicola
Populations of Rapid-Cycling Brassica rapa were
selected for resistance to disease caused by the cabbage leaf-spot, Alternaria
brassicicola. Plants are misted with a spore solution and scored for
disease manifestation. After six generations of selection, treatments differ
regarding disease expression. I am in the process of evaluating whether
populations differ the their resistance to other enemies.
Selection for anthocyanin expression
Anthocyanins are plant pigments that have been implied
in resistance to UV radiation and in plant-animal and plant fungal interactions,
both mutualistic (in attracting pollinators and seed dispersers) and antagonistic
(provinding resistance to fungi and insect herbivores). I have generated
populations of Rapid-Cycling Brassica rapa that exhibit high and
low antocyanin expression. Levels of expression can be assayed easily by
visual inspection as early as the 3-day stage. Plants were scored on a
categorical scale from Intense Green (=1) to Dark Purple (=9). After three
generations of selection, treatments differed significantly in the color
expression and in their resistance to first instar larvae of Pieris
rapae, namely plants with higher antocyanin expression were more fed
upon (i.e., less resistant). I am presently assaying these populations
with regard to resistance to other enemies, as well as thinking of ways
to investigate the mechanisms of resistance (Are anthocyanins attactive?
Does the allocation to antocyanins imply lower investment in deterent compounds?)
Pupal Color polymorphism in Pieris rapae
While rearing Pieris I begun to notice variation
in the pupal color that could not be attributable to environmental
effects, as single cups with homogeneous artifical diet contained pupae
of different colors. I scored pupal color using a categorical scale, ranging
from Intense Green (=1) to Dark Brown (=9) and founded two new populations
with pupae belonging to only either color extreme. Several more rounds
of artificial selection reveled a strong response indicating an important
genetic component to color polymorphism. I am presentely repeating the
selection process with replication within treatments, and plan to investigate
potential correlated traits (adult wing pigmentation, dissecation resistance)
and well as changes in plastic response to environmental factors that alsoplay
a rolein determining pupal color (e.g. inicident wavelength)