Jones M.M.,University of Turku |
Jones M.M.,University of Aarhus |
Jones M.M.,CSIRO |
Gibson N.,Conservation Science Center |
And 6 more authors.
Journal of Biogeography | Year: 2016
Aim: Spatial turnover in plant species composition reflects the interplay between species' environmental requirements and their dispersal dynamics. However, its origins are also historical, arising from speciation, extinction and past range dynamics. Here, we test the effects of current environmental gradients and geographical distance on regional species turnover. Using a new approach, we then interpret residual turnover patterns, unexplained by these factors. Location: Native vegetation in the wheatbelt of the Southwest Australian Floristic Region (SWAFR). Methods: We fitted a generalized dissimilarity model of species turnover across 650 floristic inventory plots as a function of current climate, topography, soils and inter-plot distances. We then decomposed the model errors into independent axes of residual variation, representing unexplained species turnover. We mapped the spatial patterns evident on the main residual axes, and interpreted these using ancillary data on the life form and geographical ranges of associated species, the distributions of some major habitat types, and anomalies between recent and Last Glacial Maximum (LGM) climate. Results: Soil and climatic variables (especially phosphorus and wet quarter precipitation) made sizeable independent contributions to explaining deviance in species turnover, whereas deviance explained by inter-plot distances and climate co-varied strongly. Total explained deviance was 34%. Analyses of residual dissimilarity highlighted unexplained floristic similarity among many southern plots. A secondary residual axis highlighted unexplained variation in a broadly westerly to easterly direction. Consistent trends in the life form and geographical ranges of associated species suggest that these patterns are climate-related. LGM climatic anomalies were correlated with patterns on the second residual axis. Main conclusions: Current soil and climatic gradients are important drivers of floristic turnover in the SWAFR. However, residual analyses revealed broad-scale gradients in floristic composition unexplained by these variables. These appear to reflect imperfect modelling of the effects of current and perhaps historical climate on species turnover. © 2016 John Wiley & Sons Ltd.
Roberts D.G.,University of Wollongong |
Ottewell K.M.,University of Wollongong |
Ottewell K.M.,Conservation Science Center |
Whelan R.J.,University of Wollongong |
Ayre D.J.,University of Wollongong
Heredity | Year: 2014
Seedbanks are expected to buffer populations against disturbances, such as fire, that could alter the genetic composition of smaller, ephemeral adult populations. However, seedling genotypes may be influenced by the spatially heterogeneous nature of both the seedbank and the disturbance (for example, germination may vary with local disturbance) and also by selection acting on germination and post-germination performance. We used microsatellite-DNA surveys of seedlings emerging from the soil-stored seedbanks of Grevillea macleayana after wildfire to compare diversity and spatial structure in seedlings and adults, and through resampling of the seedling data set, to determine whether the resultant adult population reflected the effects of selection or random seedling mortality. The large post-fire seedling cohorts captured the full allelic diversity of the pre-fire adult population. However, we found a mismatch in the genotypic structure of adults and seedlings. Seedlings displayed larger heterozygous deficits than adults; however, over the ensuing 11 years, seedling heterozygosity eventually matched values for the pre-fire adults. Increasing heterozygosity among adults has generally been attributed to heterosis and/or reduction in Wahlund effects via self-thinning. Resampling of early post-fire seedlings to generate samples of equivalent size to survivors at 11 years showed that increases in heterozygosity must be driven by selection favouring outcrossed seed. This finding is important in an evolutionary context but also has implications for the restoration of natural or managed populations where a seedbank is a viable source of recruits. © 2014 Macmillan Publishers Limited All rights reserved.
Attiwill P.M.,University of Melbourne |
Ryan M.F.,VicForests |
Burrows N.,Conservation Science Center |
Cheney N.P.,CSIRO |
And 4 more authors.
Conservation Letters | Year: 2014
Lindenmayer et al. proposed that logging makes "some kinds of forests more prone to increased probability of ignition and increased fire severity." The proposition was developed most strongly in relation to the wet eucalypt forests of south-eastern Australia. A key argument was that logging in wet forests results in drier forests that tend to be more fire-prone, and this argument has gained prominence both in the literature and in policy debate. We find no support for that argument from considerations of eucalypt stand development, and from reanalysis of the only Australian study cited by Lindenmayer et al. In addition, there is no evidence from recent megafires in Victoria that younger regrowth (<10 years) burnt with greater severity than older forest (>70 years); furthermore, forests in reserves (with no logging) did not burn with less severity than multiple-use forests (with some logging). The flammability of stands of different ages can be explained in terms of stand structure and fuel accumulation, rather than as a dichotomy of regrowth stands being highly flammable but mature and old-growth stands not highly flammable. Lack of management of fire-adapted ecosystems carries long-term social, economic, and environmental consequences. ©2013 Wiley Periodicals, Inc.