Spatiotemporally explicit incidence analysis of plant functional groups in metacommunities [Elektronische Ressource] / von Andrea Schleicher

Andrea Schleicher

Sujets

• Biologie

Informations

• Publié par: carl_von_ossietzky_universitat_oldenburg
• Publié le: 01 janvier 2010
• Nombre de lectures: 11
• Langue: English
• Poids de l'ouvrage: 3 Mo

Extrait

Spatiotemporally explicit
incidence analysis
of plant functional groups
in metacommunities
Von der Fakultät für Mathematik und Naturwissenschaften
der Carl von Ossietzky Universität Oldenburg
zur Erlangung des Grades und Titels eines
Doktors der Naturwissenschaften (Dr. rer. nat.)
angenommene Dissertation von
Andrea Schleicher
geboren am 07. Juni 1979 in Nürnberg

Oldenburg 2010

Gutachter Prof. Dr. Michael Kleyer
Zweitgutachter Prof. Dr. Martin Diekmann
Tag der Disputation 17.12.2010



Contents

Summary .................................................................................................................................... v
Zusammenfassung ......................ix
1 Preface 3
2 Metacommunity theory and the functional trait concept: Towards a more general
understanding of biodiversity .................................................................................................. 11
2.1 Metacommunity theory ........ 11
2.2 The functional trait concept .. 20
2.3 Box 1: Assembly Rules ........................................................................................................... 28
2.4 Reconciling metacommunity ecology and the functional trait concept ............................... 31
3 Study design ...................................................................................................................... 37
3.1 Study area .............................. 37
3.2 Sampling design: Bridging scales ........................... 40
3.3 Functional diversity ............................................................................................................... 43
4 Seed number and terminal velocity determine plant response to habitat connectivity in
an urban landscape .................................................................................. 51
4.1 Introduction ........................................................... 52
4.2 Methods ................................ 55
4.3 Results ................................................................................................... 60
4.4 Discussion .............................. 63
5 Effects of the resident community on colonizing plants: A functional approach ............ 75
5.1 Introduction ........................................................................................................................... 77
5.2 Methods ................................ 79
5.3 Results ................................................................................................... 87
5.4 Discussion .............................. 92
6 Functional patterns during succession: Is plant community assembly trait-driven? .... 101
6.1 Introduction ......................................................................................................................... 103
6.2 Methods .............................. 107
6.3 Results ................................................................................................................................. 114
6.4 Discussion ............................ 124
7 Synthesis ......................... 133
7.1 Relationships between functional traits and assembly filters ............................................ 134
i

7.2 Plant functional groups in the study area ........................................................................... 146
7.3 Relevance of metacommunity paradigms in the study area............... 148
7.4 Predicting the relevance of metacommunity paradigms in plant communities ................. 154
7.5 A glance at methods ............................................................................................................ 157
7.6 Future research needs ......... 161
7.7 Outlook ................................................................................................................................ 163
8 Appendix ......................... 167
9 References ...................................................... 183
Acknowledgements ................................................................................ 217
Curriculum Vitae ..................... 219
Erklärung ................................................................................................................................ 223

ii



Summary
Understanding the assembly of ecological communities is a core interest of ecology –
one which is, not yet, entirely within reach. One reason is that dispersal processes have
been neglected. Metacommunity theory has shown that the type of interaction between
the exchange of individuals among communities and local competition can have strong
implications for local and regional biodiversity. Depending on what mechanisms
enable the coexistence of competitors, four paradigms are distinguished. While the
species sorting and mass effects paradigms highlight the separation of species along
abiotic gradients, dispersal limitation is central in the patch dynamics and neutral
paradigms. The neutral paradigm is special in that it denies the relevance of ecological
differences among species, making community assembly strongly contingent on
stochastic factors.
To reveal the paradigm prevailing in a given metacommunity, knowledge is required
of the relative importance of dispersal processes, abiotic habitat differentiation and
ecologically meaningful differences among species. However, such knowledge is hard
to obtain for natural plant communities where high numbers of species interact. The
functional trait concept allows for reducing complexity by using relationships between
ftraits and species ecological properties to pool species with similar
capacities to disperse, to tolerate abiotic stress and to compete into functional groups.
This thesis integrated metacommunity theory and the functional trait concept to
understand community assembly in a dynamic urban landscape. Using a successional
gradient as a proxy for varying degrees of dispersal limitation and competition,
relationships between functional traits and three assembly filters were determined at
appropriate scales. The responsiveness of plants to the spatiotemporal configuration of
habitats (dispersal filter) was examined at the scale of the study area, response to
abiotic habitat unsuitability (stress filter) at the scale of local communities, and
response to interspecific competition (competition filter) at the scale of neighboring
individuals.
v

While the stress filter was not a significant driver of community composition, effects
of dispersal limitation and local competition were supported and related to functional
traits. Species distribution models showed that species exhibiting high seed terminal
velocity and low seed numbers were more likely to be affected by habitat
configuration than others. Seed bank analysis demonstrated that extended life span and
low specific leaf area (SLA) were favorable for establishment in extant communities,
whereas annuals with high SLA were most successful at high proportions of bare
ground. Yet, these functional relationships were not reflected in the functional
diversity of local communities. When observed functional diversities were compared
to random expectations generated by a null model largely neutral patterns were
supported. In no part of the considered successional gradient did dispersal limitation,
abiotic stress or competition constrain the spectrum of functional trait expressions to a
significant degree.
From a metacommunity perspective, these results are consistent with the neutral
paradigm. While irrelevance of stress filtering contradicted the species sorting and
mass effects paradigms, the patch dynamics paradigm was unsupported due to the
absence of a trade-off between colonization and competition ability: Coexistence of
competitively weak and strong species could not be explained by a dispersal advantage
of weak competitors, because weak competitors did not exhibit greater dispersal ability
than strong ones. The neutral paradigm, however, was supported because, although
dispersal and competition filtering affected species differently according to their
functional traits, their ability to predict local community composition was small.
Overall, this thesis showed that integration of metacommunity theory and the
functional trait concept may provide a comparatively simple approach to identifying
key processes of the assembly of species-rich plant communities. It further
demonstrated that, even if species differed in their ecological properties, from a
functional view, the first years of community assembly were largely neutral. It follows
that, next to species properties and local factors, stochastic forces need to be
considered to understand community assembly - and to predict possible implications
of environmental changes for biodiversity.
vi