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Community Assembly and Spatial Ecology of Saproxylic Coleoptera
Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Animal Ecology.
2009 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Community assembly is the process deciding inclusion/exclusion of species in a developing community. Spatial ecology integrates spatial habitat factors with local biotic interactions within a given patch.

I used standardized tree bolts (0.35-1 m long) to sample saproxylic (wood living) beetles in natural and managed forest types.

Density-dependent effects were more intense in old-growth coniferous forest than in burnt forest. The final-state assemblages in these two forest types diverged regarding species composition but converged regarding community structure. The communities also followed forest-type specific assembly trajectories.

Order of arrival can influence the species assemblage, I found priority effects when comparing the reproductive success of two cerambycid species. A two-week head start had a positive effect on fitness in both species. Different fitness components were affected in the two species: offspring number in Acanthocinus aedilis and offspring quality in Rhagium inquisitor.

In birch-living Coleoptera a large part of variance in species composition could be explained by habitat variables (22.9 %), such as forest type, or spatial variables (15.8 %), such as distance apart. The assemblages in deciduous sites responded to distance apart and showed positive spatial autocorrelation up to a distance of 80 km. For assemblages in deciduous sites a metacommunity perspective is warranted – on a surprisingly large scale.

I compared two regions, one more fragmented and one less fragmented, (with 2.2 % more deciduous forest in the landscape). The effects of habitat fragmentation was primarily found in mature coniferous forest. Host-tree patches in this matrix forest were perceived as matrix by the Coleoptera in the more fragmented region but as habitat in the less fragmented region.

Some of my study sites consisted of protected old-growth forest. These were embedded in a landscape dominated by forestry. These protected areas were invaded by generalist species, thriving in managed forests.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis , 2009. , 36 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 604
National Category
Ecology
Research subject
Animal Ecology
Identifiers
URN: urn:nbn:se:uu:diva-88765ISBN: 978-91-554-7427-0 (print)OAI: oai:DiVA.org:uu-88765DiVA: diva2:159035
Public defence
2009-03-20, Zootissalen, EBC, Villavägen 18, Uppsala, 10:00 (English)
Opponent
Supervisors
Available from: 2009-02-27 Created: 2009-02-06 Last updated: 2009-03-31Bibliographically approved
List of papers
1. Tough neighbourhood ? Density-dependent effects more important in old-growth forest than in recently burnt forest for saproxylic Coleoptera
Open this publication in new window or tab >>Tough neighbourhood ? Density-dependent effects more important in old-growth forest than in recently burnt forest for saproxylic Coleoptera
(English)Manuscript (Other academic)
Abstract [en]

Resource competition is an important structuring mechanism in communities of insects living as larvae in ephemeral resource patches. Old-growth forest and recently burnt forest, two important boreal forest habitats, differ in several ways that could affect the intensity of resource competition in saproxylic (living in dead trees) Coleoptera. I studied the level of density-dependent effects in an experiment in two burnt-forest sites and two old-growth forest sites. A total of 140 bolts (0.5 m lengths of Norway spruce, Picea abies, bole) were exposed to colonization by saproxylic Coleoptera for increasingly longer times: 0.5, 1, 2, 4, and 8 weeks. Density (number of emerged Coleoptera per bolt) increased with increasing exposure time in a forest-type-specific manner. The increase showed concave-down linearity (the increase leveled off) in the old-growth sites, but a concave-up continuous increase in the burnt-forest sites. This showed that density-dependent effects, and possibly the intensity of resource competition, were more important for saproxylic Coleoptera in the old-growth-forest bolts than in the burnt-forest bolts.

National Category
Ecology
Research subject
Animal Ecology
Identifiers
urn:nbn:se:uu:diva-88759 (URN)
Available from: 2009-02-06 Created: 2009-02-06 Last updated: 2010-01-14
2. Priority effects and asymmetric competition in saproxylic cerambycids
Open this publication in new window or tab >>Priority effects and asymmetric competition in saproxylic cerambycids
(English)Manuscript (Other academic)
Abstract [en]

(1) Cerambycidae is one of the main saproxylic (dependent on dead wood) insect families. Two species, common in Sweden, Acanthocinus aedilis and Rhagium inquisitor, that colonize newly dead trees were studied in this experiment.

(2) In a two-way factorial experiment, pairs of beetles were released on caged bolts. Either two pairs of A. aedilis and two pairs of R. inquisitor, or four pairs of only one of the species were released on two occasions, with a 2-week delay between releases. The pairs released on the first occasion therefore had a 2-week priority over the pairs released on the second occasion.

(3) The hypothesis was that this 2-week priority would lead to a priority effect, manifested in offspring number and/or offspring quality.

(4) A priority effect was found in A. aedilis in offspring number and in R. inquisitor in offspring quality. Interspecific competition was asymmetrical with A. aedilis being the superior competitor. Exploitative resource competition rather than intra-guild predation was the most likely explanation.

National Category
Ecology
Research subject
Animal Ecology
Identifiers
urn:nbn:se:uu:diva-88760 (URN)
Available from: 2009-02-06 Created: 2009-02-06 Last updated: 2010-01-14
3. Community structure convergence despite different species composition: community assembly in saproxylic Coleoptera
Open this publication in new window or tab >>Community structure convergence despite different species composition: community assembly in saproxylic Coleoptera
(English)Manuscript (Other academic)
Abstract [en]

Community assembly can be viewed as the trajectory, regarding species composition and community structure, a community exhibits over time as new species fail or succeed in establishing. Community assembly in saproxylic (wood-living) Coleoptera was studied in two boreal coniferous forest types, recently burnt forest and old-growth forest, by exposing 88 Norway spruce, Picea abies, bolts (0.5 m long pieces of bole) to colonization for increasingly longer times (0.5, 1, 2, 4, and 8 weeks). The final 8-week communities diverged in species composition but converged regarding community structure measures, such as species richness. In both forest types cambivores dominated the final state. Assemblages became increasingly similar in species composition along the assembly trajectory in old-growth forest but not in burnt forest. Assemblages in the two forest types followed different trajectories regarding species composition. They also showed clear differences in evenness and species identity of the bolt-dominant species (species with the highest abundance in a particular bolt). Overall, burnt-forest bolts had a more open community with higher evenness and a more diverse selection of bolt-dominants, while old-growth bolts had a more closed community highly dominated by Dryocoetes autographus (Scolytinae), a species common also in managed forest. During assembly, burnt-forest bolts had a higher proportion fungivores than old-growth bolts. Proportion predators was higher during assembly than in the final state in both forest types. The last two results showed that guilds important during assembly were found in lower proportions in the final assemblages.

National Category
Ecology
Research subject
Animal Ecology
Identifiers
urn:nbn:se:uu:diva-88761 (URN)
Available from: 2009-02-06 Created: 2009-02-06 Last updated: 2010-01-14
4. What is the matrix ? A sea or a habitat for saproxylic Coleoptera in deciduous forest fragments in boreal forest
Open this publication in new window or tab >>What is the matrix ? A sea or a habitat for saproxylic Coleoptera in deciduous forest fragments in boreal forest
(English)Manuscript (Other academic)
Abstract [en]

We compared two regions that differed in the level of habitat fragmentation regarding deciduous trees. Brassberget, a less fragmented region, and Gåsberget, a more fragmented region that had a 2 % lower proportion of deciduous forest than Brassberget. We investigated the assemblage of saproxylic Coleoptera in birch in remnant patches of deciduous forest as well as in two matrix forest-types: mature coniferous forest and clear-cuts. We exposed 240 standardized birch bolts (tree bole, 1m in length) to natural colonization in a total of 30 forest sites and then collected Coleoptera emerging from those bolts. The saproxylic Coleoptera assemblages reflected the underlying regional difference in level of fragmentation. In the less fragmented region the Coleoptera assemblages in deciduous remnants and mature coniferous forest were largely similar in species composition, guild proportions, species richness, evenness, and dominance. The clear-cuts in this region differed from the other two forest types in all these community measures. In the more fragmented region there was a different pattern. In that region, the deciduous remnants were different from the matrix forest types, both mature coniferous sites and clear-cuts, in species composition, guild proportions, and evenness whereas the two matrix forest types had largely converged regarding all these community measures. Regional comparisons of forest types, showed that there was forest-type convergence in guild proportions in both deciduous remnants and in clear-cuts but regional divergence in mature coniferous sites. Thus, the effects of increasing habitat fragmentation was primarily found in mature coniferous forest. We conclude that in the less fragmented region, mature matrix forest retain habitat characteristics similar enough to natural deciduous forest to allow a saproxylic Coleoptera fauna similar to the one in deciduous forest-fire remnants to develop.

National Category
Ecology
Research subject
Animal Ecology
Identifiers
urn:nbn:se:uu:diva-88762 (URN)
Available from: 2009-02-06 Created: 2009-02-06 Last updated: 2010-01-14
5. Forest-type dependent response to spatial factors in birch-living saproxylic Coleoptera assemblages
Open this publication in new window or tab >>Forest-type dependent response to spatial factors in birch-living saproxylic Coleoptera assemblages
(English)Manuscript (Other academic)
Abstract [en]

We studied spatial factors affecting the species composition of birch-living saproxylic (breeding in dead trees) Coleoptera. We sampled 30 forest sites in two regions by rearing Coleoptera from eight standardized birch-bolts (tree bole, 1m in length) from each site. A large part of variance in species composition could be explained by habitat variables (22.9 %), such as forest type, or spatial variables (15.8 %), such as distance apart. We compared three forest types – birch-dominated deciduous forest, mature coniferous forest, and clear-cuts – and found forest-type differences in response to spatial variables. The assemblages in deciduous sites responded to distance apart and showed some positive spatial autocorrelation up to a distance of 80 km. Assemblages in coniferous sites were different in the two regions whereas assemblages in clear-cuts did not respond to any spatial variables. Thus, the variation in species composition explained by spatial factors could mainly be attributed to spatial effects in two of the forest types: deciduous forest and mature coniferous forest. A conclusion from these results is that a metacommunity approach could be useful for understanding the community dynamics in the deciduous sites. Species in clear-cuts could conform more to the concept of patchy populations since the assemblages in those sites showed no spatial structure over the maximum inter-site distance of 105 km in this study.

National Category
Ecology
Research subject
Animal Ecology
Identifiers
urn:nbn:se:uu:diva-88763 (URN)
Available from: 2009-02-06 Created: 2009-02-06 Last updated: 2010-01-14

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