A Quaternary perspective on the conservation prospects of the Tertiary relict tree Prunus lusitanica L.

Abstract

Aim To assess the importance of climate and human pressure as factors limiting the past, present and future distribution of Prunus lusitanica L. (the Portuguese laurel), a relict of Europe’s ancient subtropical laurel‐forest flora. Location The Iberian Peninsula. Methods A census was taken of the current populations of P. lusitanica in the Iberian Peninsula and the threats they face. The potential distribution of the species was modelled under current climatic conditions and under simulations of the climate for the Last Glacial Maximum (LGM), the mid‐Holocene and the year 2080. Results The present total population of 31,000 individuals is largely distributed as small, fragmented subpopulations, often threatened by agriculture or forestry. The species’ current range is much smaller than its potentially suitable range. During the LGM, P. lusitanica would have been constrained to a limited number of sites along the Atlantic coast. In the mid‐Holocene, its potential range was much wider than during the LGM and similar to that of the present day. Under the 2080 climate scenario its potential range is reduced by almost 40% compared to that of the present. This reduction includes the loss of territories currently home to three‐quarters of its Iberian population. Main conclusions Drastic climatic changes and the existence of refugia are usually invoked to explain the rarity and fragmented distribution – yet persistence – of a subtropical flora in southern Europe. The availability of climatically suitable habitats is, however, not necessarily the main factor limiting its distribution. Human impact would appear to have been – and continues to be – of fundamental importance in the current population sizes and potential range of P. lusitanica in the Iberian Peninsula.

The complex history of the olive tree: from Late Quaternary diversification of Mediterranean lineages to primary domestication in the northern Levant

“…The present oleaster distribution was relatively well predicted (figure 2a), but overflowed in some areas where oleaster populations have never been observed, such as Galicia/País Vasco (Spain) and Vendée (France). Several factors that are not accounted for by the SDM (including postglacial dispersal limitations, human impact and interspecific competition) may explain the current absence of oleasters in these climatically suitable areas [31,37]. Distribution models fitted to current climatic conditions were then projected to the past.…”

Warm-Temperate Deciduous Forests around the Northern Hemisphere

“…Finally, the presence of the relict laurophyll species increases the conservation value of all the communities studied, particularly in the present days as climate change poses new challenges to the conservation of these species (see Calleja et al 2009 Forests dominated by marcescent oak species represent the transition between deciduous forests adapted to rainy summers and cold winters, on the one hand, and evergreen sclerophyllous Mediterranean forests. In the Iberian Peninsula marcescence is shown by some oak species, including Quercus pubescens, Q. pyrenaica, Q. faginea and Q. canariensis; it suggests an old evergreen habit forced to become deciduous by the cold winters.…”

“…Nevertheless, continental Europe has preserved some remains of the laurophyll vegetation (mesophytic palaeoclimatic relicts, in the sense of Honrado et al 2001), which is generally recognized based on living populations of Rhododendron ponticum ssp. baeticum or Prunus lusitanica (Calleja et al 2009). Even the more widespread bay laurel (Laurus nobilis) can be related to this group Arroyo 2008, 2011;Rodríguez-Sánchez et al 2010).…”

Human impact – the last nail in the coffin for ancient plants?

“…Or are they? The past, present and future of a Palaeotropical Tertiary relict, Portuguese laurel ( Prunus lusitanica ), is the subject of a detailed analysis by Juan Calleja et al . (2008).…”

“…Calleja et al (2008) predict that the species’ future distribution, under climatic conditions simulated for the year 2080, will differ substantially from today’s. Laurel’s main population in Portugal is expected to decline, leaving behind a sprinkling of suitable habitats in the mountains of central and northern Spain.…”