Floristic changes in the Iberian Peninsula and Balearic Islands (south-west Europe) during the Cenozoic Jose M. Postigo Mijarra , Eduardo Barron , Fernando Gomez Manzaneque and Carlos Morla Unidad de Botdnica, Escuela Tecnica SuperiorABSTRAC T de Ingenieros de Montes, Universidad Aim The aim of this work was to identify the main changes in the flora Politecnica de Madrid, Ciudad Universitaria s/n, Madrid, Spain and Instituto Geologico yan d vegetation of the Iberian Peninsula over the Cenozoic Era, to record the Minero de Espaha, Rios Rosas, Madrid, Spaindisappearanc e of taxa associated with these changes and to determine the influence of climate and human activity on these events. Location The Iberian Peninsula and Balearic Islands. Methods A critical review was made of the palaeobotanical literature with the aims of detecting patterns of floristic change and extracting information on the disappearance of different taxa over the Cenozoic. These data are viewed alongside the most recent data for the climate of this period. A critical analysis is made of the role of Palaeotropical and Arctotertiary taxa in the forest communities of the Iberian Peninsula throughout the Cenozoic. Results Although the Eocene-Oligocene transition was a time when many taxa disappeared, the most outstanding events occurred between the end of the Oligocene and throughout the Miocene. Substantial floristic changes took place over this period, including the disappearance of 177 Palaeotropical taxa. This was probably related to acute cooling and aridification; no evidence exists that the Messinian Salinity Crisis had any important effect in the Iberian Peninsula. The last great disappearance of Palaeotropical taxa (36 in total) ended in the Middle- Late Piacenzian; Arctotertiary taxa were most affected during the Pleistocene. The Lower-Middle Pleistocene transition, best represented by marine isotopic stages (MIS) 36-34 and 20-18 and characterized by a change in glacial cyclicity, was the time of the last notable disappearance of taxa. Main conclusions This work provides the first chronogram of extinctions for the Iberian flora, and records the disappearance of 277 taxa during the Cenozoic. A clear relationship was detected between the main climatic events and the latest appearances of the different taxa. Correspondence: Jose Maria Postigo Mijarra, Keywords Universidad Politecnica de Madrid, ETSI Balearic Islands, Cenozoic, floristic change, historical biogeography, Iberian Montes, Unidad de Botanica, Ciudad Universitaria s/n, 28040 Madrid, Spain. Peninsula, paleobotany, palaeoclimate, palaeoecology, plant geography, E-mail: [email protected] Quaternary. disappearance of taxa during the Cenozoic. Climate, geology INTRODUCTION and ecology must all have had a direct impact on the The palaeobotanical data provided by outcrops from around survival of the different elements. Many studies on changes the Iberian Peninsula (Figs 1-3) suggest its Cenozoic flora to in the Cenozoic climate have been published in recent years, have been highly diverse and composed of taxa very and the main trends have been established at a global level different from those of today. The modern flora of the (Zachos et al, 2001; Lisiecki & Raymo, 2005; Mosbrugger Iberian Peninsula is thus the product of the appearance and et ah, 2005). Determining the influence of these past 0° 44° • '•••v.il C* ' r3S ' 42° <£ 40° 38° : • - # Palaeogene fossil localities 36° Figure 1 Palaeogene sites of the Iberian Peninsula and Balearic Islands. The inner lines mark the main rivers and channels in the Iberian Peninsula. The Palaeogene is represented by a small number of fossil localities. Several of these fossil sites are placed in northern Iberia. Figure 2 Miocene and Pliocene sites of the Iberian Peninsula and Balearic Islands. Note the high number of fossil localities in north-east and south-west Iberia and the general lack of fossil localities in the interior of the Iberian Peninsula. episodes of change on the then existent flora, however, is a although it was Mai (1989, 1991) who proposed that these more complex matter. terms be used to describe ecological units (or geofloras). Numerous studies on the palaeobiogeographical features of According to Mai, a 'Palaeotropical geoflora' was present in the Cenozoic flora of Europe - mainly of the Neogene - have Europe from the Late Cretaceous to the Late Miocene, been undertaken (Mai, 1989, 1991, 1995; Sue, 1989; Sue et ah, consisting of paratropical rain forests, subtropical rain and 1992), although the characteristics of the palaeofloras of laurel forests, temperate laurel forests and laurel-conifer western Eurasia remain largely unknown (Utescher et al., forests (the latter constrained by edaphic factors). At the same 2007). Several different vegetation units have been described time, an 'Arctotertiary geoflora' existed, represented by warm in Europe for these periods. Engler (1879-1882) was the first temperate rain forests, lowland and swamp forests - the to use the terms 'Palaeotropical' and 'Arctotertiary' flora, ancestors of mixed mesophytic forests. Later, for the 1J*W S*W PW 3»W cw 3"E S'E 45 N 45 M 40 N 40 N 35 N 35 N 12° W g° w S°w 3'W S'E Figure 3 Quaternary sites of the Iberian Peninsula and Balearic Islands. Dark grey indicates areas with a high number of fossil localities; these are mainly in northern Iberia and the centre of the peninsula (Spanish Central Range). There is a notable lack of fossil records in the inner basins. Palaeogene, Collinson & Hooker (2003) proposed: a polar, Iberian Peninsula (Hably, 1987; Wolfe, 1992). Neither in broad-leaved deciduous forest for the Palaeocene-Eocene; Spain nor in Portugal have Cenozoic plant fossils enjoyed broad-leaved, paratropical to subtropical evergreen rain forests the traditional interest they have attracted in other European for the Late Palaeocene to the Eocene; and a broad-leaved, countries; the majority of Iberia's Tertiary floras are mixed deciduous and evergreen forest plus vegetation with therefore only incompletely known (Barron et al, 1996). sclerophyllous elements for the Late Eocene and Oligocene. Nonetheless, those studies that have been published are Finally, Utescher & Mosbrugger (2007) and Utescher et al of great palaeogeographical interest and provide very valu­ (2007) describe, through the use of plant functional types, a able data on the flora of south-western Europe and its large number of phytosociological classes for both the Palae­ evolution. ogene and Neogene. The present work involved an exhaustive review of the Different floristic elements coexisted in the Iberian Penin­ palaeobotanical studies of the Cenozoic in the Iberian sula for long periods of time, leading to complex mosaics of Peninsula and the Balearic Islands (for convenience these vegetation (Mai, 1989, 1991; Palamarev, 1989; Costa et al, will be referred to collectively here as the Iberian Peninsula 2005). Indeed, the Iberian Peninsula's fossil record is witness or Iberia) (Figs 1-3), with the aim of describing the floristic to this mixing of plant types. This is further corroborated by changes that occurred during this time. A chronogram was the modern-day existence of a significant group of species of constructed to reflect these data (Fig. 4). This included all Palaeotropical origin, the distribution of which is very the taxa recorded in the different Cenozoic outcrops so far localized and restricted to Iberia (Castroviejo et al, 1986; examined. These taxa were mainly identified from their Costa et al, 2005). pollen, spores and leaf and wood remains; carpological The aims of the present work were to describe the main floral studies of the Iberian Cenozoic are scarce (Alvarez Ramis, changes of the Iberian Peninsula registered in the Cenozoic, in 1975; Menendez Amor, 1975; Gregor & Gimther, 1985; the context of the available palaeoclimatic data, and to Cabrera et al, 1994; Barron, 1996; Barron & Dieguez, 2001; determine the origin of the peninsula's modern-day flora. Martin-Closas et al, 2006), except for those performed on Holocene materials associated with archaeological remains (Ruiz et al, 1997). Similarly, very few studies containing MATERIALS AND METHODS data on flowers or inflorescences have been published Palaeobotanical data for the Cenozoic of other regions of the (Barron, 1996; Barron & Dieguez, 2001; Postigo Mijarra Northern Hemisphere are much more abundant than for the etal, 2003). Palaeogene Neoq ene Palaeocene Eocene Oligocene Miocene Pliocene Pleistocene Dan Se Tha Y Lu Ba Pri Ru Ch Aq Bur Lan Ser Tor Mes Zan Pia Gel L M U H Nothofagidites Aegiceras/Brownlowia/Peiliceria — Aiangium — Loropetalum — Maasa — Sesuvium — Heteromorpha Normapolies Sfaphylea Barringtonia Gossypium/Thespesia ! (ill! Podocarpus Bignoniacaae Ochnaceae Tropical/subtropical Lythraceae Tropical/subtropical Anacardiaceae Balanophora Commelinaceae Dennstaedtiaceae Diphyileia/Nandina/Podophyllum Eustigma Helwingia Leptopteris Lithocarpus/Pasania MasSxia Oligocene tropical group Photinia-type S/aden/a-type Tetracentron Trigonobalanus Chloranthacsae Corylopsis/Fothergilla Mahonia Disanthus/Exbucklandia Tramophyllum Combretaceae \ Malpighiaceae Passifloraceae Grewia/Corchonis Zingiberaceae \ Icacinaceae Theaceae (non Pallkaera} — Restlonaceae > \ \ \ X Agavaceae Neurada Cycadaceae Nypa Myreinaceae \ \ \ \ Sterculiaceae — \ \ Figure 4 Disappearance chronogram for the main plant taxa of the Iberian Peninsula and Balearic Islands during the Cenozoic. Symbols: *, taxa exclusively identified from megaremains; °, taxa