Deeper Phylogenetic Levels Research Articles

DNA barcoding of Squamata fauna in Qatar

Background: DNA barcoding allows for species identification and description of genetic diversity. However, in the Middle East, information on genetic diversity is accumulating at a slower pace compared to that of other regions. Methods: The COI sequence of 24 lizard and snake species in Qatar that represent major families within the order Squamata were sampled and amplified via PCR using RepCOI primers (apart from one species). Purified amplicons were then aligned, and high- quality sequences were uploaded to BOLD. Using Sphenodon punctatus as the outgroup, the phylogenetic analysis was conducted using raxmlGUI software following the maximum likelihood method. Results: The COI sequence from each of the species was obtained and the consensus sequences were submitted to GenBank. In the phylogenetic analysis, a close relationship between members of the Agamidae and Serpentes was confirmed. While members of the same genus often showed sister-taxa relationships, and species in the same family were clustered with reasonably high bootstrap supports, the COI-based phylogeny was not able to resolve the relationships among genera within the families or identify relationships with high resolution at deeper lineages. Conclusion: Although ideal for species identification, COI gene sequencing is limited in phylogenetic inference due to high mutation rates that restrict its effectiveness for resolving relationships at deep phylogenetic levels. However, COI gene sequencing can be combined with nuclear markers for a more in-depth analysis.

The use of Anchored Hybrid Enrichment data to resolve higher-level phylogenetic relationships: A proof-of-concept applied to Asterales (Eudicotyledoneae; Angiosperms)

Anchored Hybrid Enrichment (AHE) is a tool for capturing orthologous regions of the nuclear genome shared in low or single copy across lineages. Despite the increasing number of studies using this method, its usefulness to estimate relationships at deeper taxonomic levels in plants has not been fully explored. Here we present a proof of concept about the performance of nuclear loci obtained with AHE to infer phylogenetic relationships and explore the use of gene sampling schemes to estimate divergence times in Asterales. We recovered low-copy nuclear loci using the AHE method from herbarium material and silica-preserved samples. Maximum likelihood, Bayesian inference, and coalescence approaches were used to reconstruct phylogenomic relationships. Dating analyses were conducted under a multispecies coalescent approach by jointly inferring species tree and divergence times with random gene sampling schemes and multiple calibrations. We recovered 403 low-copy nuclear loci for 63 species representing nine out of eleven families of Asterales. Phylogenetic hypotheses were congruent among the applied methods and previously published results. Analyses with concatenated datasets were strongly supported, but coalescence-based analyses showed low support for the phylogenetic position of families Argophyllaceae and Alseuosmiaceae. Estimated family ages were congruent among gene sampling schemes, with the mean age for Asterales around 130 Myr. Our study documents the usefulness of AHE for resolving phylogenetic relationships at deep phylogenetic levels in Asterales. Observed phylogenetic inconsistencies were possibly due to the non-inclusion of families Phellinceae and Pentaphragmataceae. Random gene sampling schemes produced consistent age estimates with coalescence and species tree relaxed clock approaches.

Interstitial Arabidopsis-Type Telomeric Repeats in Asteraceae.

Tandem repeats of telomeric-like motifs at intra-chromosomal regions, known as interstitial telomeric repeats (ITR), have drawn attention as potential markers of structural changes, which might convey information about evolutionary relationships if preserved through time. Building on our previous work that reported outstanding ITR polymorphisms in the genus Anacyclus, we undertook a survey across 132 Asteraceae species, focusing on the six most speciose subfamilies and considering all the ITR data published to date. The goal was to assess whether the presence, site number, and chromosomal location of ITRs convey any phylogenetic signal. We conducted fluorescent in situ hybridization (FISH) using an Arabidopsis-type telomeric sequence as a probe on karyotypes obtained from mitotic chromosomes. FISH signals of ITR sites were detected in species of subfamilies Asteroideae, Carduoideae, Cichorioideae, Gymnarhenoideae, and Mutisioideae, but not in Barnadesioideae. Although six small subfamilies have not yet been sampled, altogether, our results suggest that the dynamics of ITR formation in Asteraceae cannot accurately trace the complex karyological evolution that occurred since the early diversification of this family. Thus, ITRs do not convey a reliable signal at deep or shallow phylogenetic levels and cannot help to delimitate taxonomic categories, a conclusion that might also hold for other important families such as Fabaceae.

Geographical vs. ecological diversification in Carex section Phacocystis (Cyperaceae): Patterns hidden behind a twisted taxonomy

Abstract Carex section Phacocystis (Cyperaceae) is one of the most diverse and taxonomically complex groups of sedges (between 116 and 147 species), with a worldwide distribution in a wide array of biomes. It has a very complicated taxonomic history, with numerous disagreements among different treatments. We studied the biogeography and niche evolution in a phylogenetic framework to unveil the relative contribution of geographical and ecological drivers to diversification of the group. We used a large species sampling of the section (82% of extant species) to build a phylogeny based on four DNA regions, constrained with a phylogenomic HybSeq tree and dated with six fossil calibrations. Our phylogenetic results recovered section Phacocystis s.s. (core Phacocystis) as sister to section Praelongae. Ancestral area reconstruction points toward the N Pacific as the cradle for the crown diversification of section Phacocystis during the Middle Miocene. Wide distributions were recurrently inferred across deep nodes. Large Northern Hemisphere lineages with geographical congruence were retrieved, pointing toward the importance of allopatric divergence at deep phylogenetic levels, whereas within‐area speciation emerges as the predominant pattern at shallow phylogenetic level. The Southern Hemisphere (Neotropics, SW Pacific) was colonized several times from the Northern Hemisphere. The global expansion of Carex section Phacocystis did not entail major ecological changes along the inner branches of the phylogeny. Nevertheless, ecological differentiation seems to gain importance toward recent times.

New alignment-based sequence extraction software (ALiBaSeq) and its utility for deep level phylogenetics.

Despite many bioinformatic solutions for analyzing sequencing data, few options exist for targeted sequence retrieval from whole genomic sequencing (WGS) data with the ultimate goal of generating a phylogeny. Available tools especially struggle at deep phylogenetic levels and necessitate amino-acid space searches, which may increase rates of false positive results. Many tools are also difficult to install and may lack adequate user resources. Here, we describe a program that uses freely available similarity search tools to find homologs in assembled WGS data with unparalleled freedom to modify parameters. We evaluate its performance compared to other commonly used bioinformatics tools on two divergent insect species (>200 My) for which annotated genomes exist, and on one large set each of highly conserved and more variable loci. Our software is capable of retrieving orthologs from well-curated or unannotated, low or high depth shotgun, and target capture assemblies as well or better than other software as assessed by recovering the most genes with maximal coverage and with a low rate of false positives throughout all datasets. When assessing this combination of criteria, ALiBaSeq is frequently the best evaluated tool for gathering the most comprehensive and accurate phylogenetic alignments on all types of data tested. The software (implemented in Python), tutorials, and manual are freely available at https://github.com/AlexKnyshov/alibaseq.

Phylogenetic structure of understorey annual and perennial plant species reveals opposing responses to aridity in a Mediterranean biodiversity hotspot

Aridity is a critical driver of the diversity and composition of plant communities. However, how aridity influences the phylogenetic structure of functional groups (i.e. annual and perennial species) is far less understood than its effects on species richness. As perennials have to endure stressful conditions during the summer drought, as opposed to annuals that avoid it, they may be subjected to stronger environmental filtering. In contrast, annuals may be more susceptible to interannual climatic variability. Here we studied the phylogenetic structure of the annual and perennial components of understorey plant communities, along a regional aridity gradient in Mediterranean drylands. Specifically, we asked: (1) How do species richness (S) and phylogenetic structure (PS) of annuals and perennials in plant communities respond to aridity? (2) What is the contribution of other climatic and topo-edaphic variables in predicting S and PS for both components? (3) How does the taxonomic and phylogenetic turnover of annuals and perennials vary with spatial and environmental distances? We assessed annuals' and perennials' species richness, the phylogenetic structure at deep and shallow phylogenetic levels, and taxonomic and phylogenetic turnover along spatial and environmental distances. We found no relationship between annuals' richness and aridity, whereas perennials' richness showed a unimodal pattern. The phylogenetic structure of annuals and perennials showed contrasting responses to aridity and negatively correlated with topo-edaphic variables. We found phylogenetic clustering at intermediate-to-higher aridity levels for annuals, and at lower aridity levels for perennials. Both taxonomic and phylogenetic turnover in annuals and perennials correlated with the environmental distance rather than with spatial distance between communities, suggesting adaptation to local factors. Overall, our results show a decoupling in the response of the phylogenetic structure of annual and perennial components of plant communities to aridity in Mediterranean drylands. Our findings have significant implications for land management strategies under climate change.

Productivity as the main factor correlating with migratory behaviour in the evolutionary history of warblers

AbstractThe evolution of migration in birds and its causes are still subject of debate. Recent studies tracking current bird migration have identified peaks in net primary productivity (NPP) as a main driver of bird migratory behaviour. However, it is unclear which variables may have played a major role in the evolution of bird migration at deeper phylogenetic levels. Here, we used phylogenetic comparative methods to assess whether the evolutionary patterns of migratory distances, as a proxy for migratory behaviour, are correlated with several biometric, climatic and productivity variables in a phylogenetic context, using Sylvia warblers as a case study. Our results recover NPP in the breeding range and during the breeding season as the variable with stronger positive correlation with migratory distances, being always included in the best models considering all potential variables. Several climatic variables show a correlation with the evolution of migration, but those are also tightly correlated with NPP. Among morphological variables, migratory lineages tend to have longer wings than sedentary ones. Although NPP has been identified as a driver of migratory behaviour in current species, in a phylogenetic scale it is not possible to disentangle if it was a main driver in the evolution of bird migratory behaviour or a consequence of it, yet migration and NPP seem to be tightly related today and along the long evolutionary history of these passerines.

Metagenomic assessment of the interplay between the environment and the genetic diversification of Acinetobacter.

SummaryMost bacteria have poorly characterized environmental reservoirs and unknown closely related species. This hampers the study of bacterial evolutionary ecology because both the environment and the genetic background of ancestral lineages are unknown. We combined metagenomics, comparative genomics and phylogenomics to overcome this limitation, to identify novel taxa and to propose environments where they can be isolated. We applied this method to characterize the ecological distribution of known and novel lineages of Acinetobacter spp. We observed two major environmental transitions at deep phylogenetic levels, splitting the genus into three ecologically differentiated clades. One of these has rapidly shifted towards host‐association by acquiring genes involved in bacteria‐eukaryote interactions. We show that environmental perturbations affect species distribution in predictable ways: bovines have very diverse communities of Acinetobacter, unless they were administered antibiotics, in which case they show highly uniform communities of Acinetobacter spp. that resemble those of humans. Our results uncover the diversity of bacterial lineages, overpassing the limitations of classical cultivation methods and highlight the role of the environment in shaping their evolution.

The new Hispaniolan genus Tainus (Rubiaceae) constitutes an isolated lineage in the Caribbean biodiversity hotspot

The Caribbean islands are a well-known biodiversity hotspot of global importance. Hispaniola (Dominican Republic and Haiti) is a highly diverse island with 42% of its species endemic. Here we describe the new monotypic genus Tainus (Rubiaceae, Rondeletieae), which is endemic to the Sierra de Bahoruco-La Selle. This taxon was originally published as Rondeletia pitreana, but its taxonomic status has been doubtful. We performed phylogenetic analyses with three chloroplast regions (petD, trnK-matK and trnL-F) in order to test the relationships of R. pitreana to other species of Rondeletia and allied genera. Our molecular phylogeny underscores that R. pitreana does not belong to Rondeletia, but has an isolated position within Rondeletieae, whereas Acrosynanthus is sister to an assemblage of Mazaea, Phyllomelia, Rachicallis, Roigella and Rondeletia. The recognition of the genus Tainus is supported by molecular (simple sequence repeats) and morphological characters, among which the most conspicuous is the densely papillate ornamentation of the corolla mouth and lobes. Our findings reveal another case of endemism at a deeper phylogenetic level in flowering plants on Hispaniola. Furthermore, they emphasize the importance of exploring, collecting and performing phylogenetic analyses integrating samples from larger geographical areas across countries as a basis to support nature conservation.

Manifold influences of phylogenetic structure on a plant–herbivore network

Ecologists are increasingly aware of the interplay between evolutionary history and ecological processes in shaping current species interaction patterns. The inclusion of phylogenetic relationships in studies of species interaction networks has shown that closely related species commonly interact with sets of similar species. Notably, the degree of phylogenetic conservatism in antagonistic ecological interactions is frequently stronger among species at lower trophic levels than among those at higher trophic levels. One hypothesis that accounts for this asymmetry is that competition among consumer species promotes resource partitioning and offsets the maintenance of dietary similarity by phylogenetic inertia. Here, we used a regional plant–herbivore network comprised of Asteraceae species and flower‐head endophagous insects to evaluate how the strength of phylogenetic conservatism in species interactions differs between the two trophic levels. We also addressed whether the asymmetry in the strength of the phylogenetic signal between plants and animals depends on the overall degree of relatedness among the herbivores. We show that, beyond the previously reported compositional similarity, closely related species also share a greater proportion of counterpart phylogenetic history, both for resource and consumer species. Comparison of the patterns found in the entire network with those found in subnetworks composed of more phylogenetically restricted groups of herbivores provides evidence that resource partitioning occurs mostly at deeper phylogenetic levels, so that a positive phylogenetic signal in antagonist similarity is detectable even between closely related consumers in monophyletic subnetworks. The asymmetry in signal strength between trophic levels is most apparent in the way network modules reflect resource phylogeny, both for the entire network and for subnetworks. Taken together, these results suggest that evolutionary processes, such as phylogenetic conservatism and independent colonization history of the insect groups may be the main forces generating the phylogenetic structure observed in this particular plant–herbivore network system.

The Evolutionary Ecology of Plant Disease: A Phylogenetic Perspective.

An explicit phylogenetic perspective provides useful tools for phytopathology and plant disease ecology because the traits of both plants and microbes are shaped by their evolutionary histories. We present brief primers on phylogenetic signal and the analytical tools of phylogenetic ecology. We review the literature and find abundant evidence of phylogenetic signal in pathogens and plants for most traits involved in disease interactions. Plant nonhost resistance mechanisms and pathogen housekeeping functions are conserved at deeper phylogenetic levels, whereas molecular traits associated with rapid coevolutionary dynamics are more labile at branch tips. Horizontal gene transfer disrupts the phylogenetic signal for some microbial traits. Emergent traits, such as host range and disease severity, show clear phylogenetic signals. Therefore pathogen spread and disease impact are influenced by the phylogenetic structure of host assemblages. Phylogenetically rare species escape disease pressure. Phylogenetic tools could be used to develop predictive tools for phytosanitary risk analysis and reduce disease pressure in multispecies cropping systems.

Protein change in plant evolution: tracing one thread connecting molecular and phenotypic diversity

Proteins change over the course of evolutionary time. New protein-coding genes and gene families emerge and diversify, ultimately affecting an organism’s phenotype and interactions with its environment. Here we survey the range of structural protein change observed in plants and review the role these changes have had in the evolution of plant form and function. Verified examples tying evolutionary change in protein structure to phenotypic change remain scarce. We will review the existing examples, as well as draw from investigations into domestication, and quantitative trait locus (QTL) cloning studies searching for the molecular underpinnings of natural variation. The evolutionary significance of many cloned QTL has not been assessed, but all the examples identified so far have begun to reveal the extent of protein structural diversity tolerated in natural systems. This molecular (and phenotypic) diversity could come to represent part of natural selection’s source material in the adaptive evolution of novel traits. Protein structure and function can change in many distinct ways, but the changes we identified in studies of natural diversity and protein evolution were predicted to fall primarily into one of six categories: altered active and binding sites; altered protein–protein interactions; altered domain content; altered activity as an activator or repressor; altered protein stability; and hypomorphic and hypermorphic alleles. There was also variability in the evolutionary scale at which particular changes were observed. Some changes were detected at both micro- and macroevolutionary timescales, while others were observed primarily at deep or shallow phylogenetic levels. This variation might be used to determine the trajectory of future investigations in structural molecular evolution.

Extreme mitochondrial population subdivision in southern Appalachian paleoendemic spiders (Araneae: Hypochilidae: Hypochilus), with implications for species delimitation

A prior study of molecular phylogenetic relationships in southern Appalachian Hypochilus taxa revealed unusually high intraspecific mitochondrial sequence divergences, but was limited by small intraspecific sample sizes. A subsequent in-depth population genetic study focused on a single species (H. thorelli Marx 1888), revealing genetic patterns consistent with extremely limited female-based gene flow among rock-outcrop limited populations. Here we extend the study of mitochondrial population genetic structuring to four remaining Appalachian Hypochilus species. Genetic inferences are based on a sample of COI mitochondrial sequences generated for over 250 specimens from 85 sampled locations. This geographic sample comprehensively covers the geographic distributions of all described taxa. Phylogenetic, network-based, and genealogical sorting index analyses reveal ubiquitous genetic structuring in all Hypochilus taxa. A majority of sampled locations possess limited genetic variation, with site-specific haplotypes forming genealogically exclusive ''microclades'', consistent with limited female-based gene flow at the spatial scales sampled. At deeper phylogenetic levels, four of five described species are recovered as monophyletic on mitochondrial gene trees. Hypochilus pococki Platnick 1987 is recovered as paraphyletic, and is fragmented into five genetically divergent, allopatric phylogroups. These phylogroups, and multiple clades within one of the H. pococki phylogroups, are also recovered as distinct clusters in a generalized mixed Yule-coalescent (GMYC) analysis, suggesting the possibility of multiple cryptic species in the Appalachian fauna. However, a qualitative survey of male palpal variation fails to reveal morphological differences that distinguish these highly divergent genetic lineages. We suggest that a nuclear gene tree perspective is ultimately needed to resolve this contrast.

Caryophyllales: Evaluating phylogenetic signal in trnK intron versus matK

Abstract We assess the phylogenetic information in trnK intron at the ordinal level using the Caryophyllales and compare it with that derived from matK. The trnK gene is split into two exons by an intron that includes the matK gene. The plastid trnK is a tRNA gene encoding Lysine(UUU), whereas the matK gene is a putative group II intron maturase. The two regions are usually coamplified, and trnK intron is partially sequenced but its sequences are often excluded from phylogenetic reconstruction at deep historic levels. This study shows that the two regions are comparable in proportion of variable sites, possess a comparable pattern of substitution rates per site, and display similar phylogenetic informativeness profiles and per‐site informativeness. Phylogenetic analyses show strong congruence between phylogenetic trees based on matK and trnK intron partitioned datasets from 45 genera representing 30 of the 34 recognized Caryophyllales families. The trnK intron alone provides a relatively well‐resolved topology for the order. Combining the trnK intron with matK sequence data resulted in six most parsimonious trees, differing only in the placement of Claytonia (Portulacaceae) within the noncore group. A well‐supported major basal split in the order into core and noncore Caryophyllales with Rhabdodendraceae, Simmondsiaceae, and Asteropeiaceae as sister to remaining core lineages is evident in partitioned and combined analyses. The placement of these three families has been disputable, impacting the overall backbone topology of the Caryophyllales. This study demonstrates the cost effectiveness of using the trnK intron along with matK (both substitutions and insertions/deletions) at deeper phylogenetic level.

Plumage patterns are good indicators of taxonomic diversity, but not of phylogenetic affinities, in Australian grasswrens Amytornis (Aves: Maluridae)

The grasswrens (Maluridae: Amytornis) are elusive songbirds from the arid zones of Australia. Although some other Australian bird genera are also largely restricted to arid regions, none show the level of localized taxonomic diversity seen in Amytornis. Furthermore, their cryptic plumage patterns provide excellent camouflage but make it difficult to determine whether shared patterns reflect phylogenetic relationships or adaptations to similar terrain. To resolve the systematics and patterns of ecological diversification within Amytornis, we here present the results of a phylogenetic analysis of mitochondrial and nuclear multi-locus data for all recognized species and most subspecies, using traditional concatenation-based methods as well as a coalescent-based species-tree approach. Phylogenetic patterns retrieved by the species-tree approach were highly congruent with traditional methods, although branch support was generally higher in concatenation-based analysis, suggesting that species-tree methods may furnish more conservative results. In terms of identifying taxonomic diversity there was good concordance between plumage-based assessments and DNA distances. The same concordance was not found when comparing plumage-based and DNA-based predictions of phylogenetic relationships. Four primary lineages were identified: (a) barbatus; (b) merrotsyi; (c) the textilis complex, purnelli, ballarae, goyderi and housei; and (d) woodwardi, dorotheae, and the striatus complex. There was no robust resolution of relationships between lineages. It appears that in Amytornis, plumage differentiation between discrete populations is taxonomically significant, and not greatly influenced by ecophenotypic variation. However, at the deeper phylogenetic level, similar suites of plumage characters may be phylogenetically uninformative because of homoplasy. The study reveals higher levels of taxonomic diversity in Amytornis than previously recognized, with many taxa being highly localized. Such extensive short range endemism is mainly encountered in poorly-dispersing invertebrates and is unique in Australian birds. The identification here of the additional restricted range taxa has important conservation implications.

Nucleotide substitution rates for the full set of mitochondrial protein-coding genes in Coleoptera

The ages of cladogenetic events in Coleoptera are frequently estimated with mitochondrial protein-coding genes (MPCGs) and the “standard” mitochondrial nucleotide substitution rate for arthropods. This rate has been used for different mitochondrial gene combinations and time scales despite it was estimated on short mitochondrial sequences from few comparisons of close related species. These shortcomings may cause greater impact at deep phylogenetic levels as errors in rates and ages increase with branch lengths. We use the full set of MPCGs of 15 species of beetles (two of them newly sequenced here) to estimate the nucleotide evolutionary rates in a reconstructed phylogeny among suborders, paying special attention to the effect of data partitioning and model choices on these estimations. The optimal strategy for nucleotide data, as measured with Bayes factors, was partitioning by codon position. This retrieved Adephaga as a sister group to Myxophaga with strong support (expected-likelihood weights test 0.94–1) and both sisters to Polyphaga, in contradiction with the most currently accepted views. The hypothesis of Archostemata being sister to the remaining Coleoptera, which is in agreement with morphology, was increasingly supported when third codon sites were recoded or completely removed, sequences were analyzed as AA, and heterogeneous models were implemented but the support levels remained low. Nucleotide substitution rates were strongly affected by the choice of data partitioning (codon position versus individual genes), with up to sixfold levels of variation, whereas differences in the molecular clock algorithm produced changes of only about 20%. The global mitochondrial protein coding rate using codon partitioning and an estimated age of 250 million years (MY) for the origin of the Coleoptera was 1.34% per branch per MY, which closely matches the ‘standard’ clock of 1.15% per MY. The estimation of the rates on alternative topologies gave similar results. Using local molecular clocks, the evolutionary rate in the Polyphaga and Archostemata was estimated to be nearly twice as fast as in the Adephaga and Myxophaga (1.03% versus 0.53% per MY). Rates across individual genes varied from 0.55% to 8.61% per MY. Our results suggest that cox1 might not be an optimal gene for implementing molecular clocks in deep phylogenies for beetles because it shows relatively slow rates at first and second codon positions but very fast rates at third ones. In contrast, nad5, nad4 and nad2 perform better, as they exhibit more homogeneous rates among codon positions.

Mitochondrial Insertions into Primate Nuclear Genomes Suggest the Use of numts as a Tool for Phylogeny

Homoplasy-free characters are a valuable and highly desired tool for molecular systematics. Nuclear sequences of mitochondrial origin (numts) are fragments of mitochondrial DNA that have been transferred into the nuclear genome. numts are passively captured into genomes and have no transposition activity, which suggests they may have utility as phylogenetic markers. Here, five fully sequenced primate genomes (human, chimpanzee, orangutan, rhesus macaque, and marmoset) are used to reconstruct the evolutionary dynamics of recent numt accumulation in a phylogenetic context. The status of 367 numt loci is used as categorical data, and a maximum parsimony approach is used to trace numt insertions on different branches of the taxonomically undisputed primate phylogenetic tree. The presence of a given numt in related taxa implies orthologous integration, whereas the absence of a numt indicates the plesiomorphic condition prior to integration. An average rate of 5.65 numts per 1 My is estimated on the tree, but insertion rates vary significantly on different branches. Two instances in which the presence-absence pattern of numts does not agree with the phylogenetic tree were identified. These events may be the result of either lineage sorting or reversal. Using the numts reported here to reconstruct primate phylogeny produces the canonical primate tree topology with high bootstrap support. Moreover, numts identified in gorilla Supercontigs were used to test the human-chimp-gorilla trichotomy, yielding a high level of support for the sister relationship of human and chimpanzee. These analyses suggest that numts are valuable phylogenetic markers that can be used for molecular systematics. It remains to be tested whether numts are useful at deeper phylogenetic levels.

Resource Partitioning and Sympatric Differentiation Among Closely Related Bacterioplankton

Identifying ecologically differentiated populations within complex microbial communities remains challenging, yet is critical for interpreting the evolution and ecology of microbes in the wild. Here we describe spatial and temporal resource partitioning among Vibrionaceae strains coexisting in coastal bacterioplankton. A quantitative model (AdaptML) establishes the evolutionary history of ecological differentiation, thus revealing populations specific for seasons and life-styles (combinations of free-living, particle, or zooplankton associations). These ecological population boundaries frequently occur at deep phylogenetic levels (consistent with named species); however, recent and perhaps ongoing adaptive radiation is evident in Vibrio splendidus, which comprises numerous ecologically distinct populations at different levels of phylogenetic differentiation. Thus, environmental specialization may be an important correlate or even trigger of speciation among sympatric microbes.

Disentangling causes of disjunction on the South Island of New Zealand: the Alpine fault hypothesis of vicariance revisited

Many elements of the flora and fauna of New Zealand’s South Island show disjunct distributions with conspecific populations or closely-related species that occur in the north-west and south separated by a central gap. Three events have been implicated to account for this pattern: Pleistocene glaciations, Pliocene mountain building, or displacement along the Alpine fault, the border of the Pacific and Australian plates stretching diagonally across the South Island from south-west to north-east that formed during the Miocene. Disjunct distributions of species level taxa are probably too young to be due to Alpine fault vicariance. It has therefore been suggested that the biogeographical impact of the Alpine fault, if any, should be apparent on deeper phylogenetic levels. We tested this hypothesis by reconstructing the phylogenetic relationships of the hydrobiid gastropods of New Zealand based on mitochondrial DNA fragments of cytochrome oxidase subunit I (CO I) and 16S rDNA. The creno- and stygobiont species of this family are typically poor dispersers. Therefore, ancient patterns of distribution may be conserved. The phylogenetic reconstructions were in accordance with the Alpine fault hypothesis uniting genera occurring on either side of the fault. Divergence estimates based on a molecular clock of CO I indicated splits predating the Pliocene uplift of the Alps. © 2007 The Linnean Society of London, Biological Journal of the Linnean Society, 2007, 91, 361–374.

Melanin coloration in New World orioles II: ancestral state reconstruction reveals lability in the use of carotenoids and phaeomelanins

Although many animals use carotenoids to produce bright yellow, orange, and red colors, an increasing number of studies have found that other pigments, such as melanins, may also be used to produce bright colors. Yet, almost nothing is known about the evolutionary history of this colorful melanin use. We used reflectance spectrometry to determine whether colors in New World orioles were predominantly due to carotenoids, colorful melanins, or a mixture of both. We then used ancestral state reconstruction to infer the directionality of any pigment changes and to test for phylogenetic signal. We found that three oriole taxa likely switched from carotenoid‐ to melanin‐based colors. Several other oriole taxa apparently gained localized melanin coloration, or had coloration that seemed to be produced by a mixture of carotenoids and melanins. We also found little phylogenetic signal on the use of carotenoids or melanins to produce color. However, all pigment changes occurred within one of three major clades of the oriole genus, suggesting there may be signal at deeper phylogenetic levels. These repeated independent switches between carotenoid and melanin colors are surprising in light of the important signaling role that color pigments (especially carotenoids) are thought to play across a wide range of taxa.