The Iberian Peninsula was one of the most important Pleistocene glacial refugia in Europe. A number of recent studies have documented the phylogeography of Iberian taxa and their relationship to more widely distributed species that expanded from this southern European refugium. We use a comparative approach to review the literature that challenges the paradigm of Iberia as a single refuge during Pleistocene glacial maxima and instead supports the occurrence of several Iberian refugia for a range of flora and fauna. Some patterns of phylogeo-graphic concordance were found between the refugial areas identified by different case studies and these broadly overlapped with previously recognized areas of high endemism in the Iberian Peninsula. Such patterns help to illustrate the internal complexity of the Iberian Peninsula as a glacial refugium, and show that for many species, populations with a high degree of genetic structure have existed throughout the Pleistocene. Importantly, the occurrence of these ‘refugia-within-refugia’ may confound the interpretation of phylogeographic patterns of European species, and can misleadingly support the occurrence of northern refugia. We discuss these and other consequences, especially when a limited number of samples from the southern Euro-pean refugia are used.

/pdf/refugia-within-refugia-patterns-of-phylogeographic-f9xqeaxf2y.pdf

Refugia within Refugia: Patterns of Phylogeographic Concordance in the Iberian Peninsula

Aim To detect centres of vascular plant endemism at a continental scale by analysis of specimen-based distributional data and to relate any pattern to environmental factors and history. Location Australia. Methods Presence of 8468 seed plant species-level taxa throughout continental Australia and Tasmania was mapped on a 1∞ grid to visualize the pattern of species richness. This sample comprises half the known flora. Three indices of endemism were calculated but we preferred one that is unrelated to species richness, so that these two concepts could be distinguished in practice. Centres of endemism were detected by simple mapping and by spatial autocorrelation analysis (SAC). Linear regression was used to examine the relationship of the patterns of species richness and endemism to latitude, topography and climate. Results Both species richness and endemism vary greatly across the continent but in most cases the same centres were high in both richness and endemism. Twelve distinct centres were identified. The major centres of both diversity and endemism are south-west western Australia, the Border Ranges between New South Wales and Queensland, the Wet Tropics near Cairns, Tasmania and the Iron-McIlwraith Range of eastern Cape York Peninsula. The last centre appears to be more significant than recognized by past authors. Whether this is a true Australian centre of endemism, or is largely an outlier of the flora of Papua New Guinea, is explored. Another centre, in the Adelaide‐Kangaroo Island region, has been overlooked altogether by previous authors. Regression analysis did not find a simple climatic explanation of the observed patterns. There was a suggestion that topographic variation within the 1∞ cells may be positively correlated with endemism, which is consistent with mountainous regions functioning as refugia. One clear result is that all the major centres of endemism are near-coastal. A likely explanation is that Pleistocene expansions of the central desert have been a powerful limitation on the viability of refugia for narrowly endemic species. All the centres of endemism lie outside the estimated limits of the expanded arid zone at the last glacial maximum (18,000 yr BP). In particular, the ‘Central Australian Mountain Ranges centre of plant diversity and endemism’ of Boden & Given (1995) is detected as a strong centre of species richness, but not at all as a centre of endemism. This is despite good sampling of this region. Main conclusions Endemism can be distinguished from species richness by using an appropriate index and mapping of such indices can detect centres of endemism. This study demonstrates the value of specimen based distributional data, such as is held in state herbaria and museums.

/pdf/endemism-in-the-australian-flora-53lchiw1kj.pdf

Endemism in the Australian flora

Predicting past distributions of species climatic niches, hindcasting, by using climate envelope models (CEMs) is emerging as an exciting research area. CEMs are used to examine veiled evolutionary questions about extinctions, locations of past refugia and migration pathways, or to propose hypotheses concerning the past population structure of species in phylogeographical studies. CEMs are sensitive to theoretical assumptions, to model classes and to projections in non-analogous climates, among other issues. Studies hindcasting the climatic niches of species often make reference to these limitations. However, to obtain strong scientific inferences, we must not only be aware of these potential limitations but we must also overcome them. Here, I review the literature on hindcasting CEMs. I discuss the theoretical assumptions behind niche modelling, i.e. the stability of climatic niches through time and the equilibrium of species with climate. I also summarize a set of ‘recommended practices’ to improve hindcasting. The studies reviewed: (1) rarely test the theoretical assumptions behind niche modelling such as the stability of species climatic niches through time and the equilibrium of species with climate; (2) they only use one model class (72% of the studies) and one palaeoclimatic reconstruction (62.5%) to calibrate their models; (3) they do not check for the occurrence of non-analogous climates (97%); and (4) they do not use independent data to validate the models (72%). Ignoring the theoretical assumptions behind niche modelling and using inadequate methods for hindcasting CEMs may well entail a cascade of errors and naive ecological and evolutionary inferences. We should also push integrative research lines linking macroecology, physiology, population biology, palaeontology, evolutionary biology and CEMs for a better understanding of niche dynamics across space and time.

https://onlinelibrary.wiley.com/doi/pdf/10.1111/j.1466-8238.2009.00476.x

Predicting the past distribution of species climatic niches.

Patterns and processes of Late Quaternary environmental change in a montane region of southwestern Europe

Populations left behind during climate-driven range shifts can persist in enclaves of benign environmental conditions within an inhospitable regional climate. Such climate relicts exist in numerous plant and animal species worldwide, yet our knowledge of them is fragmented and lacks a general framework. Here we synthesize the empirical evidence considering (a) relict habitats, (b) abiotic and biotic constraints on population dynamics, (c) mechanisms promoting population persistence, and (d ) uncertainties concerning their future prospects. We identify three major types of climate relicts: (a) those constrained primarily by climate-driven abiotic factors, (b )t hose restricted to areas that are inaccessible to antagonistic species for climatic reasons, and (c) those requiring a host or mutualistic species that is itself limited by climate. Understanding the formation and functioning of climate relicts is essential for their conservation and for our understanding of the response of species and populations to climate change.

/pdf/climate-relicts-past-present-future-v3wpw8cs6u.pdf

Climate Relicts: Past, Present, Future

Analyses of pollen, non-pollen microfossils and carbonaceous particles from a valley mire in the Lozoya Valley in the Sierra de Guadarrama, which forms part of the Spanish Central System, are presented. The sedimentary sequence, which covers the last 8500 years, provides one of the oldest records in the central sector of this mountain chain. The core displays evidence of well developed Pinus sylvestris forests coupled with the presence of taxa such as Castanea or Olea in the early Holocene, highlighting the value of near-tree-line montane enclaves in the reconstruction of vegetation dynamics. The results show that the Lozoya Valley was an important refugial area for thermophilous taxa and that taxa like Olea and Castanea were present in pre-Roman times in this part of the Central System. In contrast to other areas of Spain and elsewhere in Europe where Quercus replaces Pinus in the early Holocene, evidence is presented of a natural pine belt in the Iberian continental montane system throughout the Holocen...

Vegetation dynamics and human impact in the Sierra de Guadarrama, Central System, Spain

Threatened plants in Peninsular and Balearic Spain: A report based on the EU Habitats Directive

A pollen study of a peat-bog sited in the pinewood of Lillo (Le6n, Spain) is presented. The diagram shows an initial phase where a well-developed pinewood was dominant with deciduous species, followed by a selective clearance process of Pinus. Finally, the pinewood recovers again towards a similar state to that described at the beginning of the profile. Radiocarbon dates point that the timing of peat formation took place around 1720 + 60 years BP and the deforestation on 780+80 years BP. The results have allowed to explain the autochthonous character of Lillo pinewood, which remains as one of the few relics of the southern slopes of the Cantabrian Range.

http://www2.montes.upm.es/dptos/dsrn/botanica/archivos/papers/garcia anton et al. 1997- evolution of the vegetation in lillo pinewood.pdf

New data concerning the evolution of the vegetation in Lillo pinewood (Leon, Spain)

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.

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

Chorological information concerning 182 taxa of monocotyledons endemic to the Iberian Peninsula and Balearic Islands was compiled and related to the 1OOx1OOkm, 5Ox5Okm and 10xlOkm UTM grids. Distributions were analysed using multivariate methods (two-way indicator species analysis and detrended correspondence analysis) for each scale. Comparison of results allows recognition of several floristic elements and sectors (i.e. Balearic, Murcian-Almerian, south western) common to all three scales, whereas other regions are assigned to different sectors depending on the grid size considered. As a consequence of the increase in detail, characteristics such as number of sectors, the outline of boundaries and continuity or fragmentation of the areas also change. These factors are discussed.

H. Sainz Ollero

Papers

Vegetation dynamics and human impact in the Sierra de Guadarrama, Central System, Spain

Threatened plants in Peninsular and Balearic Spain: A report based on the EU Habitats Directive

New data concerning the evolution of the vegetation in Lillo pinewood (Leon, Spain)

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

Numerical analyses of distributions of Iberian and Balearic endemic monocotyledons