Master’s degree project in Plant Ecology and Systematics

The degree project may comprise 30-60 credits and can be carried out in a research group at the department of Biology, or at an external institution e.g. at another faculty or elsewhere.

Prerequisites for the Master’s degree project in Plant Ecology and Systematics

• 45 cr Advanced courses in Ecology including Plant Ecology (BIOR34) and Plant Evolution and Diversity (BIOR54). 
• A Bachelor’s degree including 90 cr in Cell Biology, Genetics, Microbiology, Ecology, Botany and Zoology and 7.5 cr in Statistics

Proposals for master degree projects in

Plant ecology and systematic

Dilemma of surplus flowers: lack or waste of resources?

Many plant species produce much more flowers than they produce fruits. This dilemma of surplus flowers has been explained, for instance, by 1) pollen limitation, 2) resource limitation, 3) pollinator attraction and 4) architectural factors. The aim of this project is to examine these alternative hypotheses for surplus flowers by conducting flower manipulations using an invasive, bumblebee-pollinated herb as a model species (field work will take place in June-July), and to compare the observed flower-fruit ratios to those reported for other species.

Please contact Satu Ramula if you are interested in this proposal.

Evolution and systematics of some forms in Rubus sect. Corylifolii (Rosaceae)

Rubus sect. Corylifolii is a large group of blackberries believed to have arisen by hybridisation between dewberry (R. caesius; “blåhallon”) and various species of true blackberries (R. sect. Rubus; “björnbär”). From the latter, they have inherited the capacity of forming fruits without fertilisation. Therefore, a large number of closely related forms have developed, especially in southern Scandinavia and central Europe. In Sweden, about 30 species are known, but several of them are controversial. This work is a part of a larger project to bring order into this section in Sweden. We will study three issues.

First, we will decide whether a form found locally on around Örö, south of Västervik in Småland, which has sometimes been called R. balticus, is the same species as R. lagerbergii (“filtbjörnbär”), from the west-coast of Sweden.

Second, we will test whether a newly described species, R. polybrachteatus (onsalabjörnbär) from ~15 localities on Onsala peninsula in northern Halland, is identical to several forms found in northwestern Skåne. One of the latter forms has previously been (invalidly) described as R. trivultus.

Finally, we will study what has traditionally been called Rubus pruinosus (“hallonbjörnbär”) in Sweden. This is normally considered as a widespread a species and it is even red-listed (VU). However, in our experience, it is a very heterogeneous species with a scattered distribution. Our hypothesis is that it is not a monotopic species, but instead a collection of primary hybrids between various Corylifolii and Rubus idaeus (raspberry; “hallon”).

In this project, we will test these hypotheses by screening material of the various taxa, as well as putative parents of R. pruinosus for nuclear microsatellites. Nuclear microsatellites are codominant nuclear markers, which means that markers from both parents are expressed in the hybrid offspring. They are also variable enough to test our hypothesis of independent and local origins.

The project is appropriate for a Masters thesis of 15 or 30 hp. The project will be performed at the Plant Systematics DNA lab in the Ecology Building, Dept. of Biology, LU. Plant material of various Rubus forms has already been collected during 2010 and 2011 by Ulf Ryde and coworkers. The practical part of the project will thus include DNA extraction and analysis of nuclear microsatellites, using available equipment at the DNA lab and under supervision of Mikael Hedrén. Data analysis and interpretation of results will be carried in collaboration with both supervisors.

We look for a student who is interested in plant evolution and systematics. You should be careful and confident in handling small amounts of material. It is a plus if you have already developed an interest in systematics or have experience from work in a DNA lab. The work should be performed during autumn 2011 or spring 2012.

Supervisors: Mikael Hedrén, Dept of Biology, LU and Ulf Ryde, Dept of Chemistry, LU.

Please contact Mikael Hedrén or Ulf Ryde if you are interested in this proposal.

Local adaptation in the partial inbreeder Collinsia heterophylla

Populations can become different for a number of reasons, either related to chance (genetic drift) or natural selection (e.g., local adaptation). In plants it is possible that local selection on the mating system (i.e. selfing rate) lead to divergence across populations. Some plants have a mixed mating system, where outcrossing and selfing occurs in the same individual. To date, it is not fully known how such a mating system can be evolutionary stable over time. One hypothesis is that availability and predictability of pollinators influence selection on the mating system. Investigating if plants are locally adapted in mating system is important for our general understanding of how mixed mating can persist and how selection on the mating system can influence divergence.

Within the genus of Collinsia (ca 20 species, native to California) species vary substantially in mating system from mainly selfing to more outcrossing. In the more outcrossing species, selfing is delayed until late in the floral lifetime. Delayed selfing allows for reproductive assurance if pollinators fail to visit. The more outcrossing species also possess delayed stigma receptivity. This is puzzling because it implies that the stigma becomes receptive at the time when selfing occurs, reducing the opportunity for outcrossing. We have shown that early-arriving outcross pollen can still father seeds by waiting on the unreceptive stigma until maturity in Collinsia heterophylla. However, it is still not clear why plants possess delayed stigma receptivity at all. We think that this trait may be useful for enhancing pollen competition, which increases the possibilities for sexual selection and sexual conflicts.

In order to investigate local adaptation in traits related to the mating system in C. heterophylla, plant material collected as seeds from about 20 wild populations can be grown in the greenhouse, i.e. in a common environment. Characteristics of the plants will be measured, including timing of selfing, timing of stigma receptivity, pollen competitive ability and flower size, shape and colour. Patterns of variation of plant traits will be compared across populations. Furthermore, trait variation will be compared with already recorded environmental factors of the wild populations in order to learn more about the underlying cause of the variation.

Please contact Åsa Lankinen or Stefan Andersson if you are interested in this proposal.

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