Biologische Hochschulschriften (Goethe-Universität)
Refine
Institute
- Biodiversität und Klima Forschungszentrum (BiK-F) (3)
(remove)
3 search hits
-
The impact of land-use intensification on pollination and seed-dispersal interactions in the wild cherry (Prunus avium L.)
(2012)
-
Nils Breitbach
- Menschliche Aktivitäten beeinflussen beinahe alle Bereiche des Lebens auf der Erde (MEA
2005a; UNEP 2007). Die Zerstörung und Veränderung natürlicher Lebensräume sind als
Hauptursache für den weltweiten Biodiversitätsverlust identifiziert (Harrison and Bruna 1999;
Dale et al. 2000; Foley et al. 2005; MEA 2005a). Zusammen mit dem Klimawandel wird die
Landnutzungsveränderung daher als einflussreichster Aspekt anthropogen verursachten
globalen Wandels betrachtet (MEA 2005a). Landnutzungsveränderung schließt sowohl die
Umwandlung natürlicher Habitate in Agrarland oder Siedlungen als auch die Landnutzungsintensivierung
in bereits kultivierten Landschaften mit ein. Diese Veränderungen haben weitreichende
Konsequenzen für die Artenvielfalt und resultieren häufig in dem Verlust von Arten
mit zunehmender Intensität der Landnutzung (Scholes and Biggs 2005).
Biodiversität und Ökosysteme stellen viele verschiedene Funktionen zur Verfügung, wie z. B.
die Sauerstoffproduktion, die Reinigung von Wasser und die Bestäubung von Nutzpflanzen.
Einige dieser Funktionen sind hilfreich, andere wichtig und wieder andere notwendig für das
menschliche Wohlergehen (MEA 2005b; UNEP 2007). Mittlerweile sind Ökosystemfunktionen
und die vielen Nutzen, die sie erbringen, zu einem zentralen Thema der interdisziplinären
Forschung von Sozialwissenschaften und Naturwissenschaften geworden (Barkmann et al.
2008 und darin enthaltene Referenzen). Dadurch bedingt ist es zu einiger Verwirrung bezüglich
der verwendeten Begriffe der "Ökosystemfunktion" (engl. "ecosystem function") und dem der
"Ökosystemdienstleistung" (engl. "ecosystem service") gekommen (deGroot et al. 2002). Da der
Fokus meiner Arbeit auf grundlegenden Funktionen von Ökosystemen liegt, verwende ich im
Folgenden den Begriff der Ökosystemfunktion.
Für viele Ökosystemfunktionen ist noch sehr unzureichend bekannt, wie diese von externen
Störungen beeinflusst werden (Kremen and Ostfeld 2005; Balvanera et al. 2006). Ökosystemfunktionen
werden selten von nur einer einzigen Art aufrechterhalten, sondern meist von einer
ganzen Reihe unterschiedlicher taxonomischer Gruppen – alle mit ihren ganz eigenen
Ansprüchen. Diese Arten, wie auch deren intra- und interspezifischen Interaktionen, können durchaus unterschiedlich auf die gleiche Störungsquelle oder Störungsintensität reagieren. Dies
kann Vorhersagen zum Verhalten von Ökosystemfunktionen extrem erschweren. ...
-
Spatial and temporal fluctuations in bird communities along a forest-farmland gradient in western Kenya
(2012)
-
Ronald K. Mulwa
- The impacts of human activities, notably the conversion of tropical forests into farmland
habitat, has profound impacts on biological diversity and ecosystem functions
(Millennium Ecosystem Assessment 2005). It is widely debated to what extent human modified
landscapes can maintain tropical biodiversity and their ecosystem
functionality (e.g. Waltert et al. 2004, Sekercioglu et al. 2007). In this thesis, I have used a huge and temporarily replicated dataset to assess the value of different habitat types differing in land-use intensities for bird communities in tropical East Africa. I investigated bird abundance and species richness along a forest-farmland habitat gradient and assessed spatial and temporal fluctuations of bird assemblages and their food resources.
I could show that forest and farmland habitats harbor distinct bird communities.
Moreover, the protection of natural forests merits the highest priority for conserving the high diversity of forest-dependent bird species. My study, however, also shows that farmland habitats in the proximity of natural forest can support a high bird diversity. High bird diversity in tropical farmlands depends on a high structural complexity, such
as in small-scale subsistence farmlands. From my findings, I conclude that the
conversion of forest to farmland leads to substantial losses in bird diversity, in
particular in specialized feeding guilds such as insectivores, while the conversion of structurally heterogeneous subsistence farmlands to sugarcane plantation causes erosion of bird diversity in agricultural ecosystems. Both findings are important for
conservation planning in times when tropical forests and agroecosystems are under constantly high pressure due to increasing human population numbers and global
demands for biofuel crops (Gibbs et al. 2008).
From an ecosystem function perspective, my study demonstrates the potential of
agroecosystems in supporting important ecosystem functions, such as seed dispersal by frugivorous birds and pest control by insectivorous birds. I could show that bird abundances in both frugivorous and insectivorous guilds were strongly predicted by
their respective food resources, implying that seasonal shifts in fruit and invertebrate abundance at Kakamega forest and surrounding farmlands affect community dynamics and appear to influence local movement patterns of birds. The most interesting finding of this study was that feeding guilds responded idiosyncratically to resource fluctuations. Frugivore richness fluctuated asynchronously in forest and farmland habitats, suggesting foraging movements and fruit tracking across habitat borders. In contrast, I found that insectivores fluctuated synchronously in the two habitat types, suggesting a lack of inter-habitat movements. I therefore predict that insectivorous bird communities in this forest-farmland landscape may be more susceptible to the
combined effects of land-use and climate change, due to their narrow habitat niche and
limited capacity to track their resources.
The fact that a number of bird species regularly moved across the landscape mosaic in my study system implies that birds are able to provide long-distance seed
dispersal across habitat borders. Thus, birds may enhance forest regeneration in
human-modified landscapes, such as those in most parts of tropical Africa, given that
forest remnants are protected within an agricultural habitat matrix. In order to
effectively conserve tropical biodiversity within forest-farmland mosaics, this study
advocates for conservation strategies that go beyond forest protection and explicitly integrate farmlands into forest management plans and policies. This should emphasize the retention of keystone habitat elements within tropical farmland landscapes, such as
indigenous trees, forest galleries and hedgerows, whose presence enhance species
diversity. Such grassroot-level approaches can be operationalized for instance through providing incentives to farmers to maintain their traditional subsistence land-use
practices and through community-based livelihood projects aiming at enhancing local habitat heterogeneity and inter-habitat connectivity.
-
Expansion of CORE-SINEs in the genome of the Tasmanian devil
(2012)
-
Maria A. Nilsson
Axel Janke
Elizabeth P. Murchison
Zemin Ning
Björn M. Hallström
- Background: The genome of the carnivorous marsupial, the Tasmanian devil (Sarcophilus harrisii, Order: Dasyuromorphia), was sequenced in the hopes of finding a cure for or gaining a better understanding of the contagious devil facial tumor disease that is threatening the species’ survival. To better understand the Tasmanian devil genome, we screened it for transposable elements and investigated the dynamics of short interspersed element (SINE) retroposons.
Results: The temporal history of Tasmanian devil SINEs, elucidated using a transposition in transposition analysis, indicates that WSINE1, a CORE-SINE present in around 200,000 copies, is the most recently active element. Moreover, we discovered a new subtype of WSINE1 (WSINE1b) that comprises at least 90% of all Tasmanian devil WSINE1s. The frequencies of WSINE1 subtypes differ in the genomes of two of the other Australian marsupial orders. A co-segregation analysis indicated that at least 66 subfamilies of WSINE1 evolved during the evolution of Dasyuromorphia. Using a substitution rate derived from WSINE1 insertions, the ages of the subfamilies were estimated and correlated with a newly established phylogeny of Dasyuromorphia. Phylogenetic analyses and divergence time estimates of mitochondrial genome data indicate a rapid radiation of the Tasmanian devil and the closest relative the quolls (Dasyurus) around 14 million years ago.
Conclusions: The radiation and abundance of CORE-SINEs in marsupial genomes indicates that they may be a major player in the evolution of marsupials. It is evident that the early phases of evolution of the carnivorous marsupial order Dasyuromorphia was characterized by a burst of SINE activity. A correlation between a speciation event and a major burst of retroposon activity is for the first time shown in a marsupial genome.
