Jakobs

My research interests primarily focus on the ecology of invasive species. To improve
our understanding of plant invasion patterns, an ecosystem with strong environmental
gradients may provide exceptional study sites. The Hawaiian Islands represent one of
the few areas in the world where climatic gradients can be followed over an altitudinal
range of more than 3000m, reaching from tropical into the alpine zone. While climatic
characteristics change significantly with altitude, soil conditions remain quite similar
over the entire range.

The aim of my current project is to investigate the abundance and performance of
introduced European weeds. A broad taxonomical and morphological variation may
allow system-specific generalizations and preliminary studies have revealed the
suitability of the study system. The main questions are: (1) Does the distribution of
European weeds coincide with their distribution in the native range and does plant
fitness vary across different environmental conditions? (2) What is the role of
plasticity and genetic variation/adaptation in contributing to an invader’s success? (3)
Do the plants differ genetically from the native provenances? And if so – which
mechanisms underlie these evolutionary changes? (4) How do species change over time
after their introduction?

A combination of field data and common garden experiments is a promising approach
to answer these questions. Since most species have first been introduced to lowland
areas, we expect that ecotypes only occurring in higher altitudes are most likely the
result of post-invasion changes. To support this hypothesis of evolutionary changes
towards the boundaries of the species’ range, we are planning genetic analysis with
microsatellites. Equivalent data have already been obtained along a similar altitudinal
range in the Swiss Valais.

· Jakobs, G., E. Weber & P.J. Edwards (submitted) Invasiveness may evolve
in the introduced range – an example of Solidago gigantea Ait.

· Guesewell, S., Jakobs, G. & E. Weber (2006) Native and introduced
populations of Solidago gigantea differ in shoot production but not in leaf
traits or litter decomposition. Functional Ecology 20 (4), 575-584.

· Jakobs, G. & E. Weber (2005) Biological flora of Central Europe: Solidago
gigantea Ait. Flora 200: 109- 118

· Jakobs, G., E. Weber & P.J. Edwards (2004) Introduced populations of the
invasive Solidago gigantea (Asteraceae) are larger and grow denser than
conspecifics in the native range. Diversity and Distributions, 10:10-19.

· Jakobs, G., E. Weber & P.J. Edwards (2004) Are introduced populations of
Solidago gigantea Ait more competitive than native ones? – A field survey.
Neobiota 3: 16- 19

· Jakobs, G. (2004) Evolution of increased competitive abilities in the
invasive perennial Solidago gigantea. PhD- Thesis, Geobotanical Institute,
ETH Zurich.

· Jakobs, G., E. Weber & P.J. Edwards (2001) Life-history and genetic
variation of native and introduced populations of Solidago gigantea. Bulletin
of the Geobotanical Institute ETH Zurich 67: 73- 78.