Landscape moderation of biodiversity patterns and processes - eight hypotheses
Tscharntke, T. ; Tylianakis, J.M. ; Rand, T.A. ; Didham, R.K. ; Fahrig, L. ; Batary, P. ; Bengtsson, J. ; Clough, Y. ; Crist, T.O. ; Dormann, C. ; Ewers, R.M. ; Frund, J. ; Holt, R.D. ; Holzschuh, A. ; Klein, A.M. ; Kleijn, D. ; Kremen, C. ; Landis, D.A. ; Laurance, W.F. ; Lindenmayer, D.B. ; Scherber, C. ; Sodhi, N. ; Steffan-Dewenter, I. ; Thies, C. ; Putten, W.H. van der; Westphal, C. - \ 2012
Biological Reviews 87 (2012)3. - ISSN 1464-7931 - p. 661 - 685.
different spatial scales - agri-environment schemes - land-use intensity - experimentally fragmented landscape - species-area relationships - tropical habitat gradient - soil decomposer community - biological-control agents - natural enemy diversity - food-web str
Understanding how landscape characteristics affect biodiversity patterns and ecological processes at local and landscape scales is critical for mitigating effects of global environmental change. In this review, we use knowledge gained from human-modified landscapes to suggest eight hypotheses, which we hope will encourage more systematic research on the role of landscape composition and configuration in determining the structure of ecological communities, ecosystem functioning and services. We organize the eight hypotheses under four overarching themes. Section A: ‘landscape moderation of biodiversity patterns' includes (1) the landscape species pool hypothesis—the size of the landscape-wide species pool moderates local (alpha) biodiversity, and (2) the dominance of beta diversity hypothesis—landscape-moderated dissimilarity of local communities determines landscape-wide biodiversity and overrides negative local effects of habitat fragmentation on biodiversity. Section B: ‘landscape moderation of population dynamics' includes (3) the cross-habitat spillover hypothesis—landscape-moderated spillover of energy, resources and organisms across habitats, including between managed and natural ecosystems, influences landscape-wide community structure and associated processes and (4) the landscape-moderated concentration and dilution hypothesis—spatial and temporal changes in landscape composition can cause transient concentration or dilution of populations with functional consequences. Section C: ‘landscape moderation of functional trait selection’ includes (5) the landscape-moderated functional trait selection hypothesis—landscape moderation of species trait selection shapes the functional role and trajectory of community assembly, and (6) the landscape-moderated insurance hypothesis—landscape complexity provides spatial and temporal insurance, i.e. high resilience and stability of ecological processes in changing environments. Section D: ‘landscape constraints on conservation management' includes (7) the intermediate landscape-complexity hypothesis—landscape-moderated effectiveness of local conservation management is highest in structurally simple, rather than in cleared (i.e. extremely simplified) or in complex landscapes, and (8) the landscape-moderated biodiversity versus ecosystem service management hypothesis—landscape-moderated biodiversity conservation to optimize functional diversity and related ecosystem services will not protect endangered species. Shifting our research focus from local to landscape-moderated effects on biodiversity will be critical to developing solutions for future biodiversity and ecosystem service management.
Age structure in neutral theory resolves inconsistencies related to reproductive size threshold
Rosindell, J. ; Jansen, P.A. ; Etienne, R.S. - \ 2012
Journal of Plant Ecology 5 (2012)1. - ISSN 1752-9921 - p. 64 - 71.
species-area relationships - biodiversity - speciation - model - biogeography - limitation - dispersal - diversity - abundance - forests
Neutral theory consists of a suite of models that assume ecological equivalence among individual organisms. They have been most commonly applied to tropical forest tree communities either as null models or as approximations. Neutral models typically only include reproductive adults; therefore, fitting to empirical tree community data requires defining a reproductive-size threshold, which for trees is usually set arbitrarily to a diameter at breast height (DBH) of 100 mm. The inevitable exclusion of some reproductive adults and inclusion of some saplings cause a non-random sampling bias in neutral model fits. Here, we investigate this problem and resolve it by introducing simple age structure into a neutral model.