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

How many species of Plagiothecium are there and how should they be delimited and identified?

In contemporary floras, the number of species of the moss genus Plagiothecium (Swedish: sidenmossor) recognized in Sweden varies between 7 and 10. Most of these species are common and widespread, but still there is no consensus on how many species to recognize and how they should be circumscribed and identified, and this has become an urgent issue for the ongoing inventory of the bryophyte flora of the province of Skåne. The idea of this project is to use herbarium specimens from Skåne (and possibly other areas), measure all morphological characters that may potentially differ between the species and analyse this data statistically with the aim of demonstrating how many (and which) species that are possible to recognize and what characters that can be used for identifying them.

Please contact Torbjörn Tyler if you are interested in this proposal.

Patterns of morphological variation, geographic distribution and taxonomy of a less well understood group of plants in the Scandinavian flora

In general, the species of vascular plants native to the Scandinavian flora are well known. However, there are still some species, in particular among the most common and widespread ones, that exhibit huge morphological variation the geographic distribution and taxonomy of which is not well described and understood and in most cases no unbiased analysis of the pattern of variation has been undertaken. The idea of this group of projects is to chose one of several such species (or groups of species), identify and measure variable morphological characters using herbarium specimens from throughout their distribution (at least in Scandinavia) and analyse the results by statistical techniques with the aim of getting to know which and how many subspecific taxa that may be recognized and mapping their distribution. Depending on the choice of study species, some work with the scientific nomenclature of the taxa may also be needed. A few suitable groups to study are shortly described below, but there are additional candidates.

• Leontodon/Scorzoneroides autumnalis (Swedish: höstfibbla). Four varieties of this species are currently recognized in Scandinavia, but many more varieties and subspecies have been described in the past and the morphological variation found in the area is apparently not well reflected in the current taxonomy.
• Erigeron acris (Swedish: gråbinka). Between four and six subspecies are currently recognized within this species in Scandinavia, but there are different opinions on how they should be identified and what geographic distribution they have. In addition, their relationship to some of the closely related species that are found in the alpine areas are not well understood.
• Pilosella suecica (Swedish: svenskfibbla). This widespread species is currently broadly circumscribed and no subspecific taxa are recognized, but there is considerable morphological variation within the species which may be geographically structured and possibly usful to recognize taxonomically.
• Hieracium atronitens agg. (Swedish: glansfibblor). A group of c. 20 apomictic species distributed in southern Sweden. Most of the species were originally described based on very limited material from restricted geographic regions, but as more collections have accumulated in the herbaria it has become evident that some of the species may indeed be identical while, on the other hand, there are probably some local species that has yet not been described and named.

Please contact Torbjörn Tyler if you are interested in this proposal.

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 Stefan Andersson if you are interested in this proposal.

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