Search

A recent publication (Pedreschi et al., 2014, Journal of Biogeography, 41, 548-560) casts doubt over the status of pike (Esox lucius) as a non-native species in Ireland by reporting two distinct genetic groups of pike present: one a human introduction in the Middle Ages, the other hypothesized to result from natural colonization after the Last Glacial Maximum (LGM). While the existence of two groups is not disputed, the hypothesized natural colonization scenario conflicts with the sequence in which the islands of Britain and Ireland became isolated from Europe after the LGM. An alternative natural colonization scenario raised herein was rejected, leaving an earlier, two-phase, human introduction of pike from Britain or Europe to Ireland as a realistic alternative hypothesis explaining the results of Pedreschi et al. (2014). This leaves the debates on human introduction versus natural colonization, introduced versus native species status, and pike management in Ireland wide open. [ABSTRACT FROM AUTHOR]

Aim One prominent explanation for the latitudinal gradient in biodiversity proposes that its prime cause is the greater age and/or higher origination rates of tropical clades, and the infrequent or delayed dispersal of their component species into temperate regions. An alternative is that species' carrying capacities vary regionally, which influences rates of time-averaged diversification via ecological opportunity. We contrast these hypotheses, in order to assess potential historical influences upon the latitudinal gradient of New World passerine birds (order Passeriformes), comparing patterns among the two suborders present (oscines and suboscines), which are known to have had different routes of dispersal across the region. Location New World. Methods We examine diversity patterns, their abiotic and biotic correlates, and the distributions of phylogenetically old and young species. Results Strong latitudinal gradients are present within both oscine and suboscine birds, with maximum diversity towards the equator, but their overall shapes differ. Among the oscines, older lineages are found towards the north, with progressively younger lineages present further south. Regional variation in oscine richness is statistically well explained by a combination of productivity and elevation ( R2 = 0.76). In contrast, few suboscine groups have colonized the north, so their current diversity is well correlated with temperature seasonality ( R2 = 0.74). Main conclusions Because the oscines colonized the Americas from the north, their latitudinal gradient must reflect regional differences in time-averaged diversification rates, and not the time present within a region. The richness patterns derived from phylogenetic data and the strong predictive power of the normalized difference vegetation index (NDVI) suggest that the radiation of the oscines is consistent with the idea that entry into a new region stimulates a burst of diversification, which is higher and/or continues for longer in areas with greater carrying capacity. Conversely, the suboscine distributions potentially reflect a large historical barrier to dispersal and niche conservatism of climatic tolerances, possibly coupled with competition from the oscines. Although contemporary conditions can explain much of the passerine diversity patterns, history has had an important influence on the taxonomic composition of this gradient. [ABSTRACT FROM AUTHOR]

Aim We investigated genetic variation of Irish pike populations and their relationship with European outgroups, in order to elucidate the origin of this species to the island, which is largely assumed to have occurred as a human-mediated introduction over the past few hundred years. We aimed thereby to provide new insights into population structure to improve fisheries and biodiversity management in Irish freshwaters. Location Ireland, Britain and continental Europe. Methods A total of 752 pike ( Esox lucius) were sampled from 15 locations around Ireland, and 9 continental European sites, and genotyped at six polymorphic microsatellite loci. Patterns and mechanisms of population genetic structure were assessed through a diverse array of methods, including Bayesian clustering, hierarchical analysis of molecular variance, and approximate Bayesian computation. Results Varying levels of genetic diversity and a high degree of population genetic differentiation were detected. Clear substructure within Ireland was identified, with two main groups being evident. One of the Irish populations showed high similarity with British populations. The other, more widespread, Irish strain did not group with any European population examined. Approximate Bayesian computation suggested that this widespread Irish strain is older, and may have colonized Ireland independently of humans. Main conclusions Population genetic substructure in Irish pike is high and comparable to the levels observed elsewhere in Europe. A comparison of evolutionary scenarios upholds the possibility that pike may have colonized Ireland in two 'waves', the first of which, being independent of human colonization, would represent the first evidence for natural colonization of a non-anadromous freshwater fish to the island of Ireland. Although further investigations using comprehensive genomic techniques will be necessary to confirm this, the present results warrant a reappraisal of current management strategies for this species. [ABSTRACT FROM AUTHOR]

Aim The challenge for phylogeography, like other observational sciences, is to extract general relationships representing causes and effects from complex natural data. I describe comparisons of synchronously diverging co-distributed ( SDC) taxa, including sympatric sister species, to help meet this challenge. Location Global. Methods As an example, using narrative and best evidence synthesis, I re-evaluate ad hoc aggregate analyses relating population genetic structure ( FST) to dispersal potential. I deconstruct an aggregate global analysis to generate a regional subset of data which I compare with datasets describing co-distributed taxa, SDC species and sympatric sister species. Results A weak negative relationship between FST and dispersal potential is implied by aggregate global analysis (0.1 ≤ R2 ≤ 0.29). In contrast, regional datasets of co-distributed species show strong correlation between FST and dispersal potential (0.78 ≤ R2 ≤ 0.85). Comparisons between SDC and sympatric sister species consistently evince higher gene flow in species with higher dispersal potential. Main conclusions Ad hoc aggregate analyses can be compromised by multiple sources of error. Comparisons of SDC taxa, including sympatric sister species, adapt the experimental scientific method to natural situations, providing robust and repeatable tests of phylogeographic hypotheses and accurate estimates of effect sizes. To make strong inferences about phylogeography we should seek out the hidden wealth of natural experiments that provide particularly clear opportunities to study the factors that influence patterns of biodiversity. The SDC framework enables independent tests of existing hypotheses, integration of independent studies in meta-analyses across taxa and regions, and identification of general trends versus location- or taxon-specific phenomena. Coupled with advances in statistical phylogeography, species distribution modelling and palaeoecology, the SDC framework bridges the long-standing gap between observational and experimental sciences. [ABSTRACT FROM AUTHOR]

Aim We still have limited understanding of the contingent and deterministic factors that have fostered the evolutionary success of some species lineages over others. We investigated how the interplay of intercontinental migration and key innovations promoted diversification of the genus Androsace. Location Mountain ranges and cold steppes of the Northern Hemisphere. Methods We reconstructed ancestral biogeographical ranges at regional and continental scales by means of a dispersal-extinction-cladogenesis analysis using dated Bayesian phylogenies and contrasting two migration scenarios. Based on diversification analyses under two frameworks, we tested the influence of life form on speciation rates and whether diversification has been diversity-dependent. Results We found that three radiations occurred in this genus, at different periods and on different continents, and that life form played a critical role in the history of Androsace. Short-lived ancestors first facilitated the expansion of the genus' range from Asia to Europe, while cushions, which appeared independently in Asia and Europe, enhanced species diversification in alpine regions. One long-distance dispersal event from Europe to North America led to the diversification of the nested genus Douglasia. We found support for a model in which speciation of the North American- European clade is diversity-dependent and close to its carrying capacity, and that the diversification dynamics of the North American subclade are uncoupled from this and follow a pure birth process. Main conclusions The contingency of past biogeographical connections combined with the evolutionary determinism of convergent key innovations may have led to replicated radiations of Androsace in three mountain regions of the world. The repeated emergence of the cushion life form was a convergent key innovation that fostered radiation into alpine habitats. Given the large ecological similarity of Androsace species, allopatry may have been the main mode of speciation. [ABSTRACT FROM AUTHOR]

Aim Macroecological patterns have mainly been depicted as atemporal, with existing research covering only short time periods. One fundamental pattern in macroecology is the interspecific relationship between local abundance and regional range size, which is generally considered to be positively linear. Here, we examine structural details of the relationship between abundance and range size in cyclic populations of small mammals and its long-term temporal variation. Location Finland. Methods We analysed 39 years of trapping data of Rodentia and Soricomorpha collected in field and forest habitats across Finland. Abundance was measured as the mean population density of individuals, and range size as the number of grid cells occupied and sample occupancy. Data were analysed using linear mixed models. Results The relationship between mean local density and sample occupancy was generally linear, whereas the relationship between density and the number of grid cells occupied was generally curvilinear (U-shaped) for both habitats, being negative for species with small range sizes and positive for species with larger ranges. The curvilinearity was temporally consistent in both habitats. Main conclusions The interspecific relationship between abundance and range size varies depending on how range size is measured. Interestingly, the curvilinear relationship between density and range size was found in an assemblage in which many of the species have fluctuating (cyclic) populations. Future research on abundance-range size relationships should focus on long-term temporal variation to better understand the underlying mechanisms and to develop macroecological theory. [ABSTRACT FROM AUTHOR]

Aim Using sequences of complete mitochondrial genomes, our aims were: (1) to investigate the matrilineal phylogeographical structure, migration patterns and lineage coalescence times in a large, continuous population of brown bears ( Ursus arctos); and (2) to develop a novel spatial genetic method to identify migration corridors and barriers. Location North-western Eurasia: from eastern European Russia to the Baltic Sea. Methods We sequenced the complete mitochondrial genomes of 95 brown bears. The phylogeographical resolution of complete genomes was compared to that derived from subsets of the genome, including the most commonly used shorter sequences. We conducted network and Bayesian phylogeographical analyses and developed a novel, spatially explicit, individual-based approach (called DResD) for identifying migration corridors and barriers. Results Analysis of mitogenome sequences revealed five haplogroups, specific to particular geographical areas, exhibiting far greater resolving power than shorter sequences. Estimated coalescence times for the haplogroups ranged from 7.7 to 15.2 ka, suggesting that their divergence took place after the last glaciation. We found several migration trends, including a large westward migration from eastern European Russia towards Finland. We also found evidence of a potential barrier and a migration corridor in the south-west of the study area. Main conclusions The use of complete mitochondrial genomes from a brown bear population in north-western Eurasia allowed us to identify phylogeographical structure, signatures of demographic history and spatial processes that had not previously been detected using shorter sequences. These findings have implications for studies on other species and populations, especially those exhibiting low mt DNA diversity. The relatively recent divergence estimates for haplogroups highlight the significance not only of the last glaciation but also of climatic fluctuations during the post-glacial period for the divergence of mammal populations in Europe. Our spatial genetic method represents a new tool for the analysis of genetic data in a geographical context and is applicable to any data that yield genetic distance matrices, including microsatellites, amplified fragment length polymorphisms ( AFLPs) and single-nucleotide polymorphisms ( SNPs). [ABSTRACT FROM AUTHOR]