Taxonomic depletions and ecological disruption of the Iberian flora over 65 million years

Vascular plants do not appear to experience mass extinctions (Willis & McElwain, 2002), and, as Traverse (1988) has stressed, ‘Plant evolution dances to a different beat’. This may be because of the ecophysiological and reproductive plasticity of many groups of terrestrial plants, as well as of the high frequency with which alterations in embryo development become evolutionarily fixed. It is probable that some aspects of this model will have to be reconsidered in forthcoming years as progress is made in stratigraphic resolution and as we improve the quality of the fossil record (McElwain & Punyasena, 2007). Nevertheless, it is clear that regional extinction events have occurred in plants and that these were related to changes in biome distribution and floristic composition at a continental level (Willis & McElwain, 2002). As biotic responses to climatic change have not been the same in all regions, it is crucial to gather detailed information concerning how these phenomena have varied geographically and to what extent the sequence of biodiversity loss has affected present-day floristic composition in different parts of the world. It is for this reason that we welcome the study by Postigo et al. (2009), which represents a monumental effort of nomenclatural screening, bibliographic scrutiny, and a broad conceptual consideration of the history of plants in the Iberian Peninsula and the Balearic Islands over the last 65 million years. This review of Cenozoic floras will be of particular use in international palaeontological and neontological contexts because most of the information sources discussed are difficult to find by means of conventional bibliographic and data-search protocols; for example, they include symposium proceedings, conference and unpublished reports, local journals and monographs, which are mostly in Spanish and Portuguese. Postigo et al. (2009) provide a critical review of the floristic composition and ecology of Palaeotropical and Arctotertiary taxa in Cenozoic forest communities and detail the extinctions of a number of families and genera in relation to climate change. Plants have often managed to escape abiotic stress through geographical redistribution, and the Mediterranean region has a number of examples illustrating this (Arroyo et al., 2008). The changes described in Postigo et al. (2009) demonstrate this phenomenon, and it is of particular note that Iberian floras have experienced long periods of persistence compared to floras in the rest of Europe. As Postigo et al. (2009) postulate, this can be reasonably explained using the concept of peninsular refugia (Carrión et al., 2008). However, it is also plausible that complex ecological interactions, including those derived from the enormous faunal diversity of Iberia during the Cenozoic, as well as phylogenetically structured mutualistic networks, provide an environment particularly favourable to climatic resilience. Looking at Postigo et al.’s (2009) database, several examples of the ‘Lazarus effect’ can be detected, that is, cases for which an apparently extinct taxon reappears in younger rocks. Among others, there are Phaleria and Carpodiptera across the Late Eocene– Early Oligocene interval; Gleicheniaceae and Podocarpus from the Palaeocene to the Oligocene; Chloranthaceae, Restionaceae, Nypa, Myrsinaceae, Simaourabaceae and Cycadaceae across the Palaeocene/Eocene up to the Miocene; Bombacaceae during the end of the Palaeogene; Menispermaceae, Hamamelis, Pittosporum and Celastrus from