Article

Introduction and synthesis: Plant phylogeny and the origin of major biomes.

Royal Botanic Garden Edinburgh, 20a Inverleith Row, Edinburgh EH3 5LR, UK.
Philosophical Transactions of The Royal Society B Biological Sciences (Impact Factor: 6.23). 11/2004; 359(1450):1455-64. DOI: 10.1098/rstb.2004.1539
Source: PubMed

ABSTRACT Phylogenetic trees based upon DNA sequence data, when calibrated with a dimension of time, allow inference of: (i) the pattern of accumulation of lineages through time; (ii) the time of origin of monophyletic groups; (iii) when lineages arrived in different geographical areas; (iv) the time of origin of biome-specific morphologies. This gives a powerful new view of the history of biomes that in many cases is not provided by the incomplete plant fossil record. Dated plant phylogenies for angiosperm families such as Leguminoaceae (Fabaceae), Melastomataceae sensu stricto, Annonaceae and Rhamnaceae indicate that long-distance, transoceanic dispersal has played an important role in shaping their distributions, and that this can obscure any effect of tectonic history, previously assumed to have been the major cause of their biogeographic patterns. Dispersal from other continents has also been important in the assembly of the Amazonian rainforest flora and the Australian flora. Comparison of dated biogeographic patterns of plants and animals suggests that recent long-distance dispersal might be more prevalent in plants, which has major implications for community assembly and coevolution. Dated plant phylogenies also reveal the role of past environmental changes on the evolution of lineages in species-rich biomes, and show that recent Plio-Pleistocene diversification has contributed substantially to their current species richness. Because of the critical role of fossils and morphological characters in assigning ages to nodes in phylogenetic trees, future studies must include careful morphological consideration of fossils and their extant relatives in a phylogenetic context. Ideal study systems will be based upon DNA sequence data from multiple loci and multiple fossil calibrations. This allows cross-validation both of age estimates from different loci, and from different fossil calibrations. For a more complete view of biome history, future studies should emphasize full taxon sampling in ecologically important groups, and should focus on geographical areas for which few species-level phylogenies are available, such as tropical Africa and Asia. These studies are urgent because understanding the history of biomes can both inform conservation decisions, and help predict the effects of future environmental changes at a time when biodiversity is being impacted on an unprecedented scale.

1 Bookmark
 · 
136 Views
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: The crucial step in Bayesian dating of phylogenies is the selection of prior probability curves for clade ages. In studies on regions derived from Gondwana, many authors have used steep priors, stipulating that clades can only be a little older than their oldest known fossil. These studies have ruled out vicariance associated with Gondwana breakup, but only because of the particular priors that were adopted. The use of non-flat priors for fossil-based ages is not justified and is unnecessary. Tectonic calibrations can be integrated with fossil calibrations that are used to give minimum clade ages only.
    Journal of Biogeography 10/2012; 39(10):1749-1756. · 4.86 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: The problems facing workers trying to produce phylogenetic hypotheses of large genera are usually surmountable if the group in question is well studied previously. The major problems faced in plants are caused by hybridisation between species and low levels of variability in the standard phylogenetic markers. Many researchers use plastid DNA and the internal transcribed spacers of nuclear ribosomal DNA (nrDNA), neither of which alone is suitable for the detection of hybrids, the former because it is inherited through the maternal lineage and the latter because it is subject to concerted evolution via gene conversion. Sequencing low copy, protein coding, regions is a good alternative, but these are often neither easily amplified nor suitable for other reasons. Low levels of variability in the standard markers can alternatively be dealt with by using markers such as amplified fragment length polymorphisms (AFLPs). Some prospects, problems and solutions will be discussed and exemplified with work on figs ( Ficus, Moraceae) and tobacco ( Nicotiana, Solanaceae).
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Species are generally regarded as a fundamental unit of biodiversity. By contrast, higher taxa such as genera and families, while widely used as biodiversity metrics and for classification and communication, are generally not believed to be shaped by shared evolutionary processes in the same way as species. We use simulations to show that processes which are important for emergence of evolutionarily significant units (ESUs) at the species level, namely geographical isolation and ecological divergence, can generate evolutionary independence above the species level and thereby lead to emergence of discrete phylogenetic clusters (higher ESUs). Extending phylogenetic approaches for delimiting evolutionarily significant species to broader phylogenetic scales, we find evidence for the existence of higher ESUs in mammals. In carnivores, euungulates and lagomorphs the hierarchical level of units detected correspond, on average, to the level of family or genus in traditional taxonomy. The units in euungulates are associated with divergent patterns of body mass, consistent with occupation of distinct ecological zones. Our findings demonstrate a new framework for studying biodiversity that unifies approaches at species and higher levels, thus potentially restoring higher taxa to their historical status as natural entities.
    Proceedings of the Royal Society B: Biological Sciences 01/2014; 281(1783):20132750. · 5.68 Impact Factor

Full-text

Download
1 Download