Dissertation research |
Collaborative research |
Brief Introduction |
Figure 1a) Species belonging to Melampsora are the most thoroughly researched leaf pathogens in the Populus system. Melampsora sp. is a biotrophic fungi, meaning that it requires living tissue in order to reproduce. The orange pustules and orange-yellow rust are aeciospores that will disperse in the wind to infect additional hosts.
|
Figure 1b) Of note in this region are high numbers of lipid transfer genes, genes responsible for early responses to dehydration stress, and malonyl-CoA decarboxylase genes. These genes may be of particular benefit to tree tolerance and survival after successful infection by the rust pathogen. (Click for interactive figure).
|
Figure 2a) Mordwilkoja vagabunda(the poplar vagabond aphid) is a specialist insect that typically feeds on aspen and cottonwood trees. A stem mother will land on a host and feed on developing buds initiating the abnormal growth pictured here on the tip of the branch. She will then give birth through parthenogenesis (reproduction without mating) inside of the gall and her offspring will feed internally.
|
Figure 2b) Candidate genes in the region that are of note in this relationship include recent tandem duplications of Cytochrome P450 and R-genes as well as genes conferring lipoxygenase and oxidoreductase activity. These genes are important in both production of secondary metabolite plant defenses as well as recognition of insect attack which stimulates chemical defense responses. (Click for interactive figure).
|
Figure 3a) Phyllocolpa sp. are commonly referred to as leaf-folding sawflies. Female sawflies emerge in early spring and upon choosing a host they will lay an egg and sting the edge of the leaf creating swelling that creates a characteristic leaf fold over the egg.
|
Figure 3b) Candidate genes in this tree genome interval that may be important in this relationship included an enrichment of sucrose transporter genes. This may be particularly important in manipulation of host plant tissues to the nutritive benefit of larval sawflies. (Click for interactive figure).
|
Figure 4a) Pictured here is a newly hatched leaf-folding sawfly larvae feeding internally on tissue. After larvae leave the folds it creates habitat for a variety of other arthropods including caterpillar, aphids, spiders, and leaf hoppers.
|
Figure 4b) A second genetic interval that was significantly associated with the leaf-folding sawfly was found on chromosome 13. Potential candidate genes of note included a recent tandem duplication of exons encoding o-methyltransferase activity which are involved in secondary metabolite production. (Click for interactive figure).
|
Figure 5a) The Septoria musiva pathogen is a necrotrophic fungi that causes cankers which girdle and eventually kill Populus trees. S. musiva is currently one of the largest potential threats to the survival of P. trichocarpa (whose natural range is on the West coast), but the pathogens range is currently restricted to the East coast.
|
Figure 5b) Of note in this genetic region is a recent tandem duplication of a G-type lectin receptor-like protein kinase that was expanded in P. deltoides. This protein could play a similar role to a receptor-like kinase from the same family that was associated with susceptibility to S. musiva in previous P. trichocarpa research. (Click for interactive figure).
|
Figure 1) We surveyed arthropod communities in three common garden sites of P. trichocarpa in California and Oregon. Each point on this NMDS plot is a single surveyed tree and the closer two points are the more similar they were in their arthropod community composition. Color groupings indicate tree surveyed in specified garden site.
|
Figure 1) Non-metric multidimensional plot of 2017-2019 insect floral community with groupings indicated by color for sex of tree. Font size is scaled to represent three-dimensional projection.
|
Figure 2) Average activity of most common floral visitors and calculated community metrics from 2019 S. nigra surveys. Letters to the left of boxes indicate significantly different means as determined by a Tukey’s HSD (p-value < 0.05).
|