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?
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
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
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)