38 research outputs found

    Global hotspots in the present-day distribution of ancient animal and plant lineages

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    Variation in plant diversity in mediterranean-climate ecosystems: The role of climatic and topographical stability

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    Aim: Although all five of the major mediterranean-climate ecosystems (MCEs) of the world are recognized as loci of high plant species diversity and endemism, they show considerable variation in regional-scale richness. Here, we assess the role of stable Pleistocene climate and Cenozoic topography in explaining variation in regional richness of the globe's MCEs. We hypothesize that older, more climatically stable MCEs would support more species, because they have had more time for species to accumulate than MCEs that were historically subject to greater topographic upheavals and fluctuating climates. Location: South-western Africa (Cape), south-western Australia, California, central Chile and the eastern (Greece) and western (Spain) Mediterranean Basin. Methods: We estimated plant diversity for each MCE as the intercepts of species-area curves that are homogeneous in slope across all regions. We used two down-scaled global circulation models of the Last Glacial Maximum (LGM) to quantify climate stability by comparing the change in the location of MCEs between the LGM and present. We quantified the Cenozoic topographic stability of each MCE by comparing contemporary topographic profiles with those present in the late Oligocene and the early Pliocene. Results: The most diverse MCEs - Cape and Australia - had the highest Cenozoic environmental stability, and the least diverse - Chile and California - had the lowest stability. Main conclusions: Variation in plant diversity in MCEs is likely to be a consequence not of differences in diversification rates, but rather the persistence of numerous pre-Pliocene clades in the more stable MCEs. The extraordinary plant diversity of the Cape is a consequence of the combined effects of both mature and recent radiations, the latter associated with increased habitat heterogeneity produced by mild tectonic uplift in the Neogene. © 2014 John Wiley & Sons Ltd

    Where we've been and where we're going: the importance of source communities in predicting establishment success from phylogenetic relationships

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    The last two decades have seen growing use of phylogenetic patterns to test hypotheses predicting the success of introduced species. Nearly all of these tests have focused on hypotheses pertaining to phylogenetic relatedness between introduced species and those of the recipient community, largely neglecting hypotheses regarding phylogenetic relationships in the source region. We synthesize hypotheses regarding how phylogenetic relationships of both recipient and source regions together influence establishment success. We also detail how best to account for differences in source communities within phylogenetic frameworks of invasion. Existing studies have predominantly focused on the environmental filtering and competition-relatedness hypotheses, which deal with relatedness to the recipient community. We discuss how these recipient–region hypotheses can be integrated with three hypotheses focused on the relatedness between an introduced species and the source community in which it originated: the evolutionary imbalance, universal tradeoff and competitive constraint hypotheses. We detail important issues that arise when testing alternative hypotheses and interpreting results. We highlight a lack of tests of synthetic phylogenetic hypotheses including both the source and recipient community phylogenetic structure, as well as important covariates such as propagule pressure. Such synthetic tests may be valuable for identifying general phylogenetic patterns in establishment success, predicting future invasions, and for stimulating further exploration of the underlying mechanisms of invasibility. We conclude with recommendations for future studies that use phylogenetic relationships to predict invasions: including source and recipient communities, using complete phylogenies and accounting for phylogenetic uncertainty, considering multiple stages of invasion and conducting analyses across spatial and phylogenetic scales where possible.Open access articleThis item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]

    Potential Futures of Biological Invasions in South Africa

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    Biological invasions are having a moderately negative impact on human livelihoods and the environment in South Africa, but the situation is worsening. Predicting future trends is fraught with many assumptions, so this chapter takes an outcome-orientated approach. We start by envisaging four scenarios for how biological invasions might look like 200–2000 years from now: (1) “Collapse of Civilisation, but no return to Eden”, there is no advanced human civilisation left on Earth and current biological invasions play out in full; (2) “New Pangea”, a combination of the unregulated and rapid movement of species around the world and other global change drivers leads to the biotic homogenisation of areas that were previously distinct biogeographic regions such that the concept of biological invasions no longer has meaning; (3) “Preserve or Use”, while parts of the Earth continue to be utilised, some areas are actively managed and native biodiversity and biogeographic distributions are maintained; and (4) “Conservation Earth”, a highly advanced civilisation restores the Earth to a state prior to the human-mediated movement of organisms (i.e. biological invasions are reversed). Based on various horizon-scanning exercises and our own deliberations, we discuss how technological, socio-political, trade, global change, and ecological-evolutionary processes in South Africa might affect biological invasions by 2070 (i.e. when people born today will be the key decision-makers). Finally, we explore how planning, regulation, funding, public support, and research might affect invasions by 2025 (i.e. over the next planning/management/political cycle). There are many things we can neither predict nor influence, but, in part based on the insights from this book, we highlight some actions that could enable the next generation to decide what they want their future to be. A greater focus on appropriate and innovative training opportunities would increase the efficacy and responsiveness of the management of biological invasions. A shift in regulatory approach from “identify and direct” to a variety of flexible, inclusive, and sophisticated approaches underpinned by evidence might provide more societally acceptable means of addressing the multitude of competing interests. Greater co-operation on biosecurity and implementation with neighbouring countries would assist prevention measures. Finally, monitoring and research aimed at documenting, tracking, and predicting invasions and their impacts would assist with efforts to identify priorities and help us to understand the consequence of different management and policy decisions. While this was a sobering exercise, it was also empowering. If South Africans can agree on a long-term trajectory for how they want to deal with biological invasions, the potential consequences of decision-making over the short-term will become much clearer
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