A reconstruction of Palaeo-Macaronesia, with particular reference to the long-term biogeography of the Atlantic island laurel forests

Abstract

Macaronesia is a biogeographical region comprising five Atlantic Oceanic archipelagos: the Azores, Madeira, Selvagen (Savage Islands), Canaries and Cape Verde. It has strong affinities with the Atlantic coast of the Iberian Peninsula and the north‐western fringes of Africa. This paper re‐evaluates the biogeographical history and relationships of Macaronesia in the light of geological evidence, which suggests that large and high islands may have been continuously available in the region for very much longer than is indicated by the maximum surface area of the oldest current island (27 Ma) – possibly for as long as 60 million years. We review this literature, attempting a sequential reconstruction of Palaeo‐Macaronesia from 60 Ma to the present. We consider the implications of these geological dynamics for our understanding of the history of colonization of the present islands of Macaronesia. We also evaluate the role of these archipelagos as stepping stones and as both repositories of palaeo‐endemic forms and crucibles of neo‐endemic radiations of plant and animal groups. Our principal focus is on the laurel forest communities, long considered impoverished relicts of the Palaeotropical Tethyan flora. This account is therefore contextualized by reference to the long‐term climatic and biogeographical history of Southern Europe and North Africa and by consideration of the implications of changes in land–sea configuration, climate and ocean circulation for Macaronesian biogeography. We go on to provide a synthesis of the more recent history of Macaronesian forests, which has involved a process of impoverishment of the native elements of the biota that has accelerated since human conquest of the islands. We comment briefly on these processes and on the contemporary status and varied conservation opportunities and threats facing these forests across the Macaronesian biogeographical region.

Tertiary relict laurophyll vegetation in the Madonie mountains (Sicily)

“…The best preserved relict laurophyll vegetation occurs in the Canary Islands (Oberdorfer 1965;Fernández-Palacios et al 2011), in the Lusitanic and Colchidic oristic provinces (Walter 1968) and, mostly as xeromorphic derivatives, in the Mediterranean region (Schmid 1970). In Sicily, like in the Iberian Peninsula (Benito Garzón and Sainz de Ollero 2002), the response of the old tropical ora to the climatic deterioration gave rise to new vegetation types.…”

“…Any substantial or systematic reproduction, redistribution, reselling, loan, sub-licensing, systematic supply, or distribution in any form to anyone is expressly forbidden. (Mai 1989), Colchis (Filibeck, Arrigoni and Blasi 2004), and Macaronesia (Fernández-Palacios et al 2011). These evergreen woods include many remnants of the "palaeotropical geoora" (Engler 1879(Engler -1882, most of which are rare or absent from present-day vegetation in Europe.…”

Morphological and molecular data from Madeira support the persistence of an ancient lineage ofTaxus baccataL. in Macaronesia and call for immediate conservation actions

“…Such Tertiary vegetation would have established under a favourable climatic regime during the Miocene, until its continental erosion in the Pleistocene climatic change. Recent biogeographical and geological studies support the existence of ancient archipelagos, forming a Palaeo-Macaronesia since the Palaeogene (64-25 Ma); despite a degree of uncertainty, the geological dating and morphological analysis of the older seamounts potentially allow reconstruction of their series of emergence and submergence and thus their past availability as stepping stones for colonization by species from mainland communities (Fernandez-Palacios et al 2011). Available plate tectonic scenarios suggest that when these seamounts were still islands, they were located much closer to the Iberian Peninsula (Smith et al 1994;Scotese 2004), and might even acted as Palaeogene refugia during periods of unfavourable climate in the continental areas, having mild maritime climates.…”

Coastal evolution on volcanic oceanic islands: A complex interplay between volcanism, erosion, sedimentation, sea-level change and biogenic production

“…the history of emergence above sea level over space and time) (Fernández-Palacios et al, 2011), the patterns of ocean currents and winds that affect the newly-built edifices (Ávila et al, 2009a), the geographical location, and the distance to other well-established biological communities that may constitute the source of potential colonizers (MacArthur and Wilson, 1967;Fridriksson and Magnússon, 1992;Whittaker et al, 1997Whittaker et al, , 2008Whittaker and Triantis, 2012). In linear, age-progressive island chains with small inter-island spacing -like Hawai'i, Galápagos or the Society Islands -the process of biological colonization of younger volcanoes is typically facilitated by the existence of more solidly established communities in nearby older edifices -geologically "downstream" from the hotspot but biologically "upstream" -that serve as potential sources of colonizers.…”