Harald Meimberg

Multiple origins promote the ecological amplitude of allopolyploid Aegilops (Poaceae)

Polyploidy has been ubiquitous in plant evolution and is thought to be an important engine of biodiversity that facilitates speciation, adaptation, and range expansion. Polyploid species can exhibit higher ecological tolerance than their progenitor species. For allotetraploid species, this higher tolerance is often attributed to the existence of heterosis resulting from entire genome duplication. However, multiple origins of allopolyploid species may further promote their ecological success by providing genetic variability in ecological traits underlying local adaptation and range expansion. Here we show in a group of allopolyploid species in the genus Aegilops that range size and abundance are correlated with the number of inferred origins. We found that allopolyploid Aegilops spp. contain multiple chloroplast haplotypes, each identical to haplotypes of the diploid progenitor species, indicating multiple origins as the major source of variation. The number of inferred origins in each allopolyploid species was correlated to the total area occupied by the allopolyploid and the tendency for the species to be common. Additionally, we found differences in ecological tolerance among independent origins in Aegilops triuncialis. These results strongly support the hypothesis that the introduction of genetic variability by multiple origins can increase the ecological amplitude and evolutionary success of allopolyploid species.

Molecular phylogeny of the genera Digitalis L. and Isoplexis (Lindley) Loudon (Veronicaceae) based on ITS- and trnL-F sequences

Abstract.To investigate phylogenetic and biogeographic relationships all species of Digitalis and Isoplexis and one species of the outgroup genera Antirrhinum and Globularia each were analyzed using nuclear ITS and plastid trnL-F sequences. Phylogenetic trees resulting from separate analyses were highly congruent. Combined analysis revealed two major lineages, which mark an early split in the genus Digitalis. While sections Digitalis, Frutescentes and Globiflorae appear monophyletic, sect. Tubiflorae is polyphyletic and sect. Macranthae should be expanded due to paraphyly. Our results provide evidence that all species of the genus Isoplexis have a common origin and are embedded in Digitalis. Isoplexis therefore should be reduced to sectional rank. The phylogenetic placement combined with ecomorphological characters indicates that Isoplexis may be a bird-pollinated Tertiary relict. Results are discussed in the context of biogeography, chemotaxonomy and morphology.

Patterns of genetic diversity in Hepatozoon spp. infecting snakes from North Africa and the Mediterranean Basin

Species of Hepatozoon Miller, 1908 are blood parasites most commonly found in snakes but some have been described from all tetrapod groups and a wide variety of hematophagous invertebrates. Previous studies have suggested possible associations between Hepatozoon spp. found in predators and prey. Particularly, some saurophagous snakes from North Africa and the Mediterranean region have been found to be infected with Hepatozoon spp. similar to those of various sympatric lizard hosts. In this study, we have screened tissue samples of 111 North African and Mediterranean snakes, using specific primers for the 18S rRNA gene. In the phylogenetic analysis, the newly-generated Hepatozoon spp. sequences grouped separately into five main clusters. Three of these clusters were composed by Hepatozoon spp. also found in snakes and other reptiles from the Mediterranean Basin and North Africa. In the other two clusters, the new sequences were not closely related to geographically proximate known sequences. The phylogeny of Hepatozoon spp. inferred here was not associated with intermediate host taxonomy or geographical distribution. From the other factors that could explain these evolutionary patterns, the most likely seems series of intermediate hosts providing similar ribotypes of Hepatozoon and a high prevalence of host shifts for Hepatozoon spp. This is indicated by ribotypes of high similarity found in different reptile families, as well as by divergent ribotypes found in the same host species. This potentially low host specificity has profound implications for the systematics of Hepatozoon spp.

Molecular phylogenetics of Micromeria (Lamiaceae) in the Canary Islands, diversification and inter-island colonization patterns inferred from nuclear genes☆

Here we reconstruct the evolutionary history of Micromeria in the Canary Islands using eight nuclear markers. Our results show two centers of diversification for Micromeria, one in the eastern islands Gran Canaria and Lanzarote, the other in the western islands, Tenerife, La Palma and El Hierro. Suggested directions of inter-island colonization are the following: Gran Canaria to Lanzarote and La Gomera; Tenerife to La Palma (from the paleoisland of Teno), to El Hierro (from the younger, central part), and to La Gomera and Madeira (from the paleoislands). Colonization of La Gomera probably occurred several times from Gran Canaria and Tenerife. The taxonomic implications of these results are discussed. Incongruence among the different markers was evaluated and, using next generation sequencing, we investigated if this incongruence is due to gene duplication.

A new amplicon based approach of whole mitogenome sequencing for phylogenetic and phylogeographic analysis: An example of East African white-eyes (Aves, Zosteropidae)

Classical Sanger sequencing is still frequently used to generate sequence data for phylogenetic and phylogeographic inference. In this contribution we present a novel approach to genotype whole mitogenomic haplotypes using Illumina MiSeq reads from indexed amplicons. Our new approach reduces preparation time by multiplexing loci within a single or few PCR reactions and by plate format library construction. The use of paired-end reads allows covering amplicons of about 0.5kb and thus no nebulisation and assembly are necessary. We tested the power and effectiveness of this technique by analysing the mitogenomic diversity of East African white-eye bird species (Zosteropidae), a taxonomically highly diverse and complex species flock found in various ecosystems spread across major parts of Africa. We compare the newly generated mitogenomic data set with published data of three mitochondrial genes for a similar set of populations and taxa. The comparison demonstrates that our new procedure represents a cost effective use of NGS for medium throughput phylogenetic analyses. Using this method, we were able to increase the amount of phylogenetic information significantly, while reducing the costs and effort in the laboratory. The mitogenomic data show a higher resolution than previous studies providing higher support and new insights in the relationships of Zosterops species. Our data suggest to split Z. poliogaster into four distinct species, three of which had previously been proposed: Z. silvanus, Z. mbulensis, Z. kikyuensis and Z. kulalensis. Our approach allows the genotyping of whole mitogenomes for a large number of individuals and thus allows more reliable reconstruction of phylogenetic and phylogeographic relationships - also for non-model organisms.

Climate structures genetic variation across a species' elevation range: a test of range limits hypotheses

Gene flow may influence the formation of species range limits, and yet little is known about the patterns of gene flow with respect to environmental gradients or proximity to range limits. With rapid environmental change, it is especially important to understand patterns of gene flow to inform conservation efforts. Here we investigate the species range of the selfing, annual plant, Mimulus laciniatus, in the California Sierra Nevada. We assessed genetic variation, gene flow, and population abundance across the entire elevation‐based climate range. Contrary to expectations, within‐population plant density increased towards both climate limits. Mean genetic diversity of edge populations was equivalent to central populations; however, all edge populations exhibited less genetic diversity than neighbouring interior populations. Genetic differentiation was fairly consistent and moderate among all populations, and no directional signals of contemporary gene flow were detected between central and peripheral elevations. Elevation‐driven gene flow (isolation by environment), but not isolation by distance, was found across the species range. These findings were the same towards high‐ and low‐elevation range limits and were inconsistent with two common centre‐edge hypotheses invoked for the formation of species range limits: (i) decreasing habitat quality and population size; (ii) swamping gene flow from large, central populations. This pattern demonstrates that climate, but not centre‐edge dynamics, is an important range‐wide factor structuring M. laciniatus populations. To our knowledge, this is the first empirical study to relate environmental patterns of gene flow to range limits hypotheses. Similar investigations across a wide variety of taxa and life histories are needed.

Genetic structure of Micromeria (Lamiaceae) in Tenerife, the imprint of geological history and hybridization on within-island diversification

Abstract Geological history of oceanic islands can have a profound effect on the evolutionary history of insular flora, especially in complex islands such as Tenerife in the Canary Islands. Tenerife results from the secondary connection of three paleo‐islands by a central volcano, and other geological events that further shaped it. This geological history has been shown to influence the phylogenetic history of several taxa, including genus Micromeria (Lamiaceae). Screening 15 microsatellite markers in 289 individuals representing the eight species of Micromeria present in Tenerife, this study aims to assess the genetic diversity and structure of these species and its relation with the geological events on the island. In addition, we evaluate the extent of hybridization among species and discuss its influence on the speciation process. We found that the species restricted to the paleo‐islands present lower levels of genetic diversity but the highest levels of genetic differentiation suggesting that their ranges might have contracted over time. The two most widespread species in the island, M. hyssopifolia and M. varia, present the highest genetic diversity levels and a genetic structure that seems correlated with the geological composition of the island. Samples from M. hyssopifolia from the oldest paleo‐island, Adeje, appear as distinct while samples from M. varia segregate into two main clusters corresponding to the paleo‐islands of Anaga and Teno. Evidence of hybridization and intraspecific migration between species was found. We argue that species boundaries would be retained despite hybridization in response to the habitats specific conditions causing postzygotic isolation and preserving morphological differentiation.

Taxonomic confusion permits the unchecked invasion of vernal pools in California by low mannagrass (Glyceria declinata).

Abstract Chloroplast DNA sequences and recently established morphological characters were used to confirm the widespread invasion of Californias vernal pools by European low mannagrass. Morphological similarities between low mannagrass and western mannagrass have led to different taxonomic treatments, depending on the geographical extent of a particular flora. When Californias flora was last revised, the two species were combined as western mannagrass, which was then considered to be a native species. Unfortunately, the revised flora was published just as low mannagrass began to rapidly expand its range within the state and, because it was considered to be a native species in the new flora, no actions were initiated to limit the invasion. Our data show that low mannagrass was present at all localities in the Central Valley of California that were investigated, indicating a widespread and undetected invasion. The invasion has led to a degradation of the vernal pool ecosystems, which are the habitat of many federal and state protected endangered and threatened species. Nomenclature: Low mannagrass, Glyceria declinata Bréb.; western mannagrass Glyceria occidentalis (Piper) J. C. Nelson.

Genetic diversity and differentiation patterns in Micromeria from the Canary Islands are congruent with multiple colonization dynamics and the establishment of species syngameons

BackgroundEspecially on islands closer to the mainland, such as the Canary Islands, different lineages that originated by multiple colonization events could have merged by hybridization, which then could have promoted radiation events (Herben et al., J Ecol 93: 572–575, 2005; Saunders and Gibson, J Ecol 93: 649–652, 2005; Caujapé-Castells, Jesters, red queens, boomerangs and surfers: a molecular outlook on the diversity of the Canarian endemic flora, 2011). This is an alternative to the scenario where evolution is mostly driven by drift (Silvertown, J Ecol 92: 168–173, 2004; Silvertown et al., J Ecol 93: 653–657, 2005). In the former case hybridization should be reflected in the genetic structure and diversity patterns of island species. In the present work we investigate Micromeria from the Canary Islands by extensively studying their phylogeographic pattern based on 15 microsatellite loci and 945 samples. These results are interpreted according to the hypotheses outlined above.ResultsGenetic structure assessment allowed us to genetically differentiate most Micromeria species and supported their current classification. We found that populations on younger islands were significantly more genetically diverse and less differentiated than those on older islands. Moreover, we found that genetic distance on younger islands was in accordance with an isolation-by-distance pattern, while on the older islands this was not the case. We also found evidence of introgression among species and islands.ConclusionsThese results are congruent with a scenario of multiple colonizations during the expansion onto new islands. Hybridization contributes to the grouping of multiple lineages into highly diverse populations. Thus, in our case, islands receive several colonization events from different sources, which are combined into sink populations. This mechanism is in accordance with the surfing syngameon hypothesis. Contrary to the surfing syngameon current form, our results may reflect a slightly different effect: hybridization might always be related to colonization within the archipelago as well, making initial genetic diversity to be high to begin with. Thus the emergence of new islands promotes multiple colonization events, contributing to the establishment of hybrid swarms that may enhance adaptive ability and radiation events. With time, population sizes grow and niches start to fill. Consequently, gene-flow is not as effective at maintaining the species syngameon, which allows genetic differentiation and reproductive isolation to be established between species. This process contributes to an even further decrease in gene-flow between species.

New microsatellite markers for two sympatric tinamou species, the Ornate Tinamou (Nothoprocta ornata) and Darwin's Nothura (Nothura darwinii)

Tinamous (Tinamidae) represent one of the most ancient living avian lineages but their life history traits are relatively unstudied. Here we identified microsatellite loci for two sympatric tinamou species, the Ornate Tinamou (Nothoprocta ornata) and the Darwins Nothura (Nothura darwinii) from low coverage Illumina sequencing of genomic DNA. The experiment yielded a large number of candidate loci. We designed primers and tested them for successful amplification in 1 to 2 populations of the target species, tested for deviation from the Hardy–Weinberg equilibrium and the presence of null alleles, the levels of polymorphism and potential cross-amplification. All 30 and 24 loci amplified consistently, in the Ornate Tinamou and in Darwins Nothura, respectively. In the Ornate Tinamou, 25 loci were polymorphic and in the Darwins Nothura 12, with 2 to 14 alleles per locus in both species. The expected heterozygosity ranged from 0.054 to 0.917 in the Ornate Tinamou and from 0.044 to 0.908 in the Darwins Nothura. 23 (40%) of 54 loci were successfully cross-amplified. These newly discovered, polymorphic microsatellite loci represent a valuable tool for future studies on social behaviour, parentage and genetic population structure in tinamous.