The influence of Pleistocene glacial refugia on tawny owl genetic diversity and phylogeography in western Europe

The glacial refugia hypothesis indicates that during the height of the Pleistocene glaciations the temperate species that are today widespread in western Europe must have survived in small and climatically favourable areas located in the southern peninsulas of Iberia, Italy and Balkans. One such species is the tawny owl, a relatively sedentary, nonmigratory bird presently distributed throughout Europe. It is a tree-nesting species closely associated with deciduous and mixed coniferous woodlands. In this study I used control region mtDNA sequences from 187 individuals distributed among 14 populations to determine whether current genetic patterns in tawny owl populations were consistent with postglacial expansion from peninsular refugia. European, North African and Asian tawny owls were found to represent three distinct lineages, where North Africa is the sister clade to all European owls. Within Europe, I found three well-supported clades that correspond to each of the three allopatric refugia. Expansion patterns indicate that owls from the Balkan refugium repopulated most of northern Europe, while expansion out of Iberia and Italy had only regional effects leading to admixture in France. Estimates of population divergence times between refugia populations are roughly similar, but one order of magnitude smaller between Greece and northern Europe. Based on a wide range of mutation rates and generation times, divergence between refugia appears to date to the Pleistocene.     

Reassessment of phylogeographical structure in an eastern North American tree using Monmonier’s algorithm and ecological niche modelling

Aim Patterns of phylogeographical diversity in eastern North America have been well documented, with suggestions of Pleistocene refugia in both coastal and interior regions. However, most studies to date have assessed these patterns only qualitatively, largely through visual observation of haplotype networks. Furthermore, many plant studies use only one or two individuals per locality, which probably limits the recovery of haplotype diversity. The aim of this study is to address the issues of sampling strategy and quantitative assessment of phylogeographical patterns in an eastern North American tree, Fagus grandifolia (American beech). Location Eastern North America. Methods Comparing two sampling strategies (more localities with lower sample size within localities versus fewer localities with increased sample size within localities), we analysed chloroplast DNA sequence data from more than 230 individuals across 130 localities using statistical parsimony, maximum parsimony, maximum likelihood and Bayesian analyses. We then assessed support for inferred phylogenetic relationships using Monmonier’s algorithm and analysis of molecular variance. As an additional test of biogeographic hypotheses, we employed ecological niche models (ENMs), which are used to predict the geographic range of a species from occurrence data and environmental records. Here we predict both present and palaeodistributions. Results More haplotypes were recovered when more localities were sampled, but novel haplotypes and haplotype distributions were recovered using both strategies. Phylogeographical patterns suggest possible Pleistocene refugia along the Gulf and Atlantic coasts according to ENMs, as well as a more interior refugium according to Monmonier’s algorithm. Main conclusions Monmonier’s algorithm supports previous findings of an interior refugium in the Lower Mississippi River Valley/Upper Midwest, while ENMs indicate that the Gulf and Atlantic coasts may have provided the most suitable habitat for F. grandifolia during the Pleistocene. Our findings allow us to highlight the strengths and weaknesses of the two approaches. We propose that future phylogeographical studies should follow a step‐wise sampling strategy, balancing cost and expected outcomes.     

Avian distribution patterns in the Guiana Shield: implications for the delimitation of Amazonian areas of endemism

Aim To develop a methodology for defining the boundaries of the Guianan area of endemism using complementary approaches that include GIS tools, multivariate statistics and analyses of physical barriers in the distribution patterns of an entire endemic avifauna. As a case study, I used the distribution patterns of lowland terra firme forest birds. Location Guiana Shield, northern South America. Methods I identified Guianan endemics using the ornithological literature, subsequently gathering distributional data for these taxa using mainly museum collections and my own fieldwork in the region. I used these distributional data to map the spatial patterns of endemicity in the region and to compare distributions across taxa. I employed community composition data from 34 localities from throughout the Guiana Shield to identify spatial patterns of clustering using an ordination analysis (non‐metric multidimensional scaling), and to recognize the region’s main biogeographical barriers for birds using Monmonier’s algorithm. Results At least 88 avian taxa are restricted to the terra firme forests of the Guianan area of endemism, which is roughly delimited by the Amazon, Negro and Branco rivers. These large rivers, however, are not the only boundaries. I identified seven additional barriers, including medium‐sized rivers, non‐forested areas and mountains, which also contribute to delimiting the area of endemism. Within the endemic avifauna, I identified three distinct distribution patterns. The ordination analysis shows the presence of two distinct avifaunas within the Guiana Shield. Main conclusions Although the proposed boundaries of the Guianan area of endemism are consistent with previously postulated configurations, this study reveals a more complex delimitation than formerly recognized, highlighting the importance of several landscape features besides large rivers, and the existence of three distinct distributional patterns within one endemic avifauna. The Branco/Negro interfluvium, often included within this area of endemism, actually represents a transition zone between two distinct avifaunas. The longstanding view of the Amazon Basin as a mosaic of parapatric areas of endemism delimited by major rivers appears to be an oversimplification, at least for the Guiana Shield. This finding suggests the need for more rigorous approaches to re‐evaluate the traditional boundaries of such areas.