Monophyletic Species Groups Research Articles

The probability of monophyly of a sample of gene lineages on a species tree

Monophyletic groups—groups that consist of all of the descendants of a most recent common ancestor—arise naturally as a consequence of descent processes that result in meaningful distinctions between organisms. Aspects of monophyly are therefore central to fields that examine and use genealogical descent. In particular, studies in conservation genetics, phylogeography, population genetics, species delimitation, and systematics can all make use of mathematical predictions under evolutionary models about features of monophyly. One important calculation, the probability that a set of gene lineages is monophyletic under a two-species neutral coalescent model, has been used in many studies. Here, we extend this calculation for a species tree model that contains arbitrarily many species. We study the effects of species tree topology and branch lengths on the monophyly probability. These analyses reveal new behavior, including the maintenance of nontrivial monophyly probabilities for gene lineage samples that span multiple species and even for lineages that do not derive from a monophyletic species group. We illustrate the mathematical results using an example application to data from maize and teosinte.

A remarkable new Veturius (Veturius) of the Brazilian Central Amazonas, with an inventory of the genus in Brazil (Coleoptera: Passalidae)

SummaryA new species of Veturius (Veturius) Kaup, of Brazil, Central Amazonas, lower basin of Urucu, Tefé and Coari, is described and illustrated. V. urucuensis n. sp. belongs to the “cephalotes” species group, and has an external autapomorphy for the family Passalidae: a large tuft of setae on the medioposterior area of the metasternum. The species is closely allied to V. jolyi Boucher, 2006, from the Brazil-Venezuela-Guyana border. The peculiar endemism of the new species suggests an intra-continental island vicariance into the Amazon Basin. No similar process was known in the large genus Veturius. A complete inventory of the 22 Veturius species in Brazil is given, with their distribution, and following the previously established monophyletic species groups. From Brazil, two species are newly reported, V. (Ouayana) guyanensis Boucher, 2006 (Pará) and V. (O.) dominicae Boucher, 2006 (Roraima), and one species is confirmed, V. (O.) unicornis Gravely, 1918 (Amazonas). New details are given on some other Brazilian Veturius.

A Revision of the Didelphid Marsupial Genus Marmosops, Part 1. Species of the Subgenus Sciophanes

ABSTRACT In this report, the first installment of a comprehensive revision of the didelphid marsupial genus Marmosops, we revise the species of the subgenus Sciophanes. Based on morphological character variation among almost 300 examined specimens—which we interpret in the context of a previously published analysis of molecular sequence data—this revision recognizes 12 valid species in three monophyletic species groups: the Parvidens Group (including M. pakaraimae, M. parvidens, and M. pinheiroi), the Fuscatus Group (M. carri, M. fuscatus, M. handleyi, and M. invictus), and the Bishopi Group (M. bishopi, M. juninensis, M. ojastii, and two new species). For each species we summarize information about type material, ecogeographic distribution, and diagnostic morphological characters. Despite our diligent search for relevant material in North and South American museums, the absence of any specimens of Sciophanes from vast Amazonian and Andean landscapes with seemingly suitable habitat suggests that significa...

Three New Species of theTropidurus spinulosusGroup (Squamata: Tropiduridae) from Eastern Paraguay

ABSTRACT Tropidurus Wied, 1825, is one of the most ubiquitous lizard genera endemic to South America. Herpetologists from different regions of the continent have progressively mapped new populations, including undescribed species hidden under widely distributed nominal taxa. Currently, four monophyletic species groups are recognized in Tropidurus (T. bogerti group [monotypic], T. semitaeniatus group [four species], T. spinulosus group [five species], and T. torquatus group [16 species]), but none have been comprehensively revised taxonomically. During a collection expedition carried out in Paraguay in 2013, I recognized three new, distinct morphotypes among populations of the Tropidurus spinulosus group formerly assigned to T. guarani Alvarez et al., 1994. To delimit these new taxa, I analyzed coloration patterns, and quantified meristic and morphometric variables, comparing freshly collected samples with specimens housed in five museum collections. In this paper, I describe and illustrate the allopatric ...

Systematics of Ariantinae (Gastropoda, Pulmonata, Helicidae), a new approach to an old problem

A new starting-point in Ariantinae systematics is presented by combining data on traditional shell morphology and genital anatomy, with phylogeny reconstructions based on DNA sequence data. For nearly all genera and subgenera one or more shells are depicted and drawings of the proximal part of the genital organs are shown to illustrate the morphological diversification within the subfamily. For as much as our material allowed it, partial sequences are presented for Histone H3 (H3), Cytochrome c oxidase subunit I (COI), Cytochrome B (CytB) and 16S ribosomal RNA (16S). Some of the allegedly speciose genera like Chilostoma and Campylaea (Zilch, 1960) do not represent monophyletic groups of species, whereas most of the remaining nominal taxa (e.g. Causa, Dinarica, Josephinella, Faustina, Liburnica, Kosicia and Thiessea) warrant a separate taxonomic status indeed. Sequence data from individual markers were informative at the species-level, but not for higherlevel phylogenetics. Insight in genus-level relationships was obtained after concatenation of the individual datasets. The Ariantinae are estimated to have originated during the late Cretaceous (Campanian), not later than ca. 80 million years ago. The enigmatic and morphologically aberrant, monotypic genus Cylindrus is shown as the sister-group of Arianta, a genus including A. arbustorum, which is also unusual in shell-shape and habitat. Ariantopsis and Wladislawia are classified as subgenera of neither Campylaea nor Chilostoma, but Cattania. Sabljaria is considered a subgenus of Dinarica. The nominal genus Superba is shown to be paraphyletic; additional data should demonstrate whether Superba has to be synonymised with Liburnica. The Ariantinae are here divided in 21 genera (2 new) and 13 subgenera (3 new).

Where do the Neotropical Empidini lineages (Diptera: Empididae: Empidinae) fit in a worldwide context?

The tribe Empidini (Diptera: Empididae: Empidinae) is a diverse group with fourteen genera, seven of which are exclusive to the Neotropical region: Bolrhamphomyia Rafael, Chilerhamphomyia Rafael, Hystrichonotus Collin, Lamprempis Wheeler and Melander, Macrostomus Wiedemann, Opeatocerata Melander and Porphyrochroa Melander. Although Empidini itself is likely paraphyletic, many presumably monophyletic genera and species groups are recognized. Here, we apply DNA sequences from multiple genes to infer the phylogeny of Empidini, focusing on placing the Neotropical lineages within the entire tribe and identifying monophyletic groups. We included 98 Empidini taxa along with 18 outgrous terminals, spanning the diversity within the group. The results from the analyses performed are largely similar, with major groupings of genera in common. Specifically, the analyses recovered a monophyletic Hilarini and a paraphyletic Empidini. Most species from Chile and Argentina (Andean region) are found to belong to an early branching lineage within Empidinae, and are not monophyletic with other Empidini. A large portion of the remaining Neotropical Empidini (not Andean) comprises a single clade that includes four endemic genera and a number of Neotropical Empis Linneaus species. Macrostomus and Porphyrochroa each recovered as monophyletic and sister to one another, although generic placement of a few taxa remains uncertain due to conflicting morphological features. Lamprempis+Opeatocerata are also found to be sister-taxa in most analyses. Several large genera were found to be polyphyletic or paraphyletic including Empis and Rhamphomyia Meigen. We evaluate our findings and discuss them in light of current Empidinae taxonomy.

Molecular phylogeny of the diverse parasitoid wasp genus Ophion Fabricius (Hymenoptera: Ichneumonidae: Ophioninae)

AbstractOphion Fabricius is a diverse genus of nocturnal ichneumonid wasps (Insecta: Hymenoptera) that is particularly species‐rich in temperate areas, yet has received little taxonomic attention in the Holarctic region, where most species occur. While there have been some attempts to divide Ophion into monophyletic species groups, the vast majority of species have been lumped into a single, paraphyletic group, the O. luteus species group, which is defined only by the lack of characters specific to the other groups. The challenging morphology of this large catch‐all group has limited attempts to subdivide it, and no phylogenetic hypothesis has been proposed for the genus as a whole. In this study, we use DNA sequence data [28S ribosomal RNA (28S), cytochrome oxidase 1 (COI) and internal transcribed spacer 2 (ITS2)] to present the first molecular phylogeny of Ophion. We also describe the secondary structure of ITS2 for the first time in Ichneumonidae, and explore its implications for phylogeny estimation. We define 13 species groups, nine of which were previously considered part of the O. luteus species group s.l. The included species groups are the O. minutus, O. areolaris, O. scutellaris, O. flavidus, O. parvulus, O. slossonae, O. nigrovarius, O. pteridis, O. luteus s.s., and O. obscuratus species groups, along with three groups lacking described species (Species group 1, New Zealand group, Madagascar group). This study provides a framework for future studies of this diverse and morphologically challenging genus.

Making Mosquito Taxonomy Useful: A Stable Classification of Tribe Aedini that Balances Utility with Current Knowledge of Evolutionary Relationships.

The tribe Aedini (Family Culicidae) contains approximately one-quarter of the known species of mosquitoes, including vectors of deadly or debilitating disease agents. This tribe contains the genus Aedes, which is one of the three most familiar genera of mosquitoes. During the past decade, Aedini has been the focus of a series of extensive morphology-based phylogenetic studies published by Reinert, Harbach, and Kitching (RH&K). Those authors created 74 new, elevated or resurrected genera from what had been the single genus Aedes, almost tripling the number of genera in the entire family Culicidae. The proposed classification is based on subjective assessments of the “number and nature of the characters that support the branches” subtending particular monophyletic groups in the results of cladistic analyses of a large set of morphological characters of representative species. To gauge the stability of RH&K’s generic groupings we reanalyzed their data with unweighted parsimony jackknife and maximum-parsimony analyses, with and without ordering 14 of the characters as in RH&K. We found that their phylogeny was largely weakly supported and their taxonomic rankings failed priority and other useful taxon-naming criteria. Consequently, we propose simplified aedine generic designations that 1) restore a classification system that is useful for the operational community; 2) enhance the ability of taxonomists to accurately place new species into genera; 3) maintain the progress toward a natural classification based on monophyletic groups of species; and 4) correct the current classification system that is subject to instability as new species are described and existing species more thoroughly defined. We do not challenge the phylogenetic hypotheses generated by the above-mentioned series of morphological studies. However, we reduce the ranks of the genera and subgenera of RH&K to subgenera or informal species groups, respectively, to preserve stability as new data become available.

Una visión filogenética de <i>Frankliniella</i> (Tbysanoptera: Tbripidae)

The pbylogeny of the species groups of Franldiniella and the position of Exophtalmothirps and Bolbothrips are discussed with reference to recent literature and analysis with the cladistic software PAUP 3.0 in its heuristic option, the matrix has 24 taxa and 25 cbaracteristics for each; 1) the intonsa group is nOl a well defined taxon and may include groups of species, but there are no good morphological traits fot its recognition, 2) the pulchella and cephaUca groups are consistent monophyletic groups of species, 3) the minuta group is rnonophyletic with a few roorphological constraints, 4) Exophtalmothrips and Bolbothíips seem to he segregated, and notsynonymous of Franlcliniella.

Stable isotope evidence for trophic overlap of sympatric Mexican Lake Chapala silversides (Teleostei: Atherinopsidae: Chirostoma spp.)

We explore the trophic role that a diverse sympatric group of fishes in the genus Chirostoma play in a large, shallow lake in central Mexico, Lake Chapala. We use δ13C and δ15N stable isotope - based food web analyses to explore how they relate to other components of the Lake Chapala ecosystem. We find five Chirostoma species in top trophic levels of the Chapala food web compared to other fishes, relying on a combination of zooplankton, fish and benthic resources as energy sources. Food web metric analyses showed generally overlapping trophic niches for members of Chirostoma, especially in terms of δ13C. However, C. jordani had lower mean δ15N isotopic values than C. promelas. As a group, "pescados blancos" (C. sphyraena and C. promelas) also had higher δ15N signatures than "charales" (C. consocium, C. jordani and C. labarcae) reflecting greater piscivory, but these differences were not strong for all food web metrics used. Trophic overlap among species of Chirostoma in Lake Chapala raises questions about the forces that might have led to a morphologically diverse but functionally similar and monophyletic group of species.

Histiostoma ovalis (Histiostomatidae, Acari) associated with Ips sexdentatus (Scolytinae, Curculionidae, Coleoptera): ecology and mite redescription on the basis of formerly unknown adults and nymphs

Histiostomatidae represent a clade within the Astigmata and disperse phoretically by the highly modified deutonymph. A monophyletic species group within the Histiostomatidae, the bark-beetle-clade, includes mites associated with bark beetles (Scolytinae). Histiostoma ovalis Müller, 1860, only known by the morphology of its deutonymph, is a member of this clade. Since almost 150 years other developmental stages of the mite were never described. Thus we hereby present adults and nymphal instars of H. ovalis for the first time and designate a neotype. Mites were reared starting from phoretic deutonymphs, collected from adults of Ips sexdentatus and from its original galleries, found in Southern Italy and Germany. Additional deutonymphs were examined from the Slovak Republic and Croatia. During the last 60 years there has been confusion about the identity of two species, Histiostoma ovalis Müller, 1860 and H. gladiger Vitzthum, 1926, which were assumed by some authors to be synonymous. We do not contribute new findings about H. gladiger, but in this paper we define the mite, which is usually associated with Ips sexdentatus, as H. ovalis. Almost 100% of adult beetle individuals collected from their galleries in the bark of pine trees were covered with deutonymphs. The average number of deutonymphs per beetle and information of the preferred areas for mite-attachment on the beetle body are presented. Fungal spores were discovered sticking to the cuticle of deutonymphs and other mite instars. Hyperphoresy with deutonymphs of H. ovalis, riding on gamasid mites, which represent also phoretic passengers of I. sexdentatus, was additionally observed.For a better description of H. ovalis, mite specimens from Germany were used to achieve DNA barcoding-sequences. A Baltic amber fossil of an extinct bark beetle, which has four phoretic histiostomatid mite deutonymphs attached to its body, is presented. There is morphological evidence that those deutonymphs could be phylogenetically closely related to H. ovalis.

A global phylogeny of leafmining Ectoedemia moths (Lepidoptera: Nepticulidae): exploring host plant family shifts and allopatry as drivers of speciation.

BackgroundHost association patterns in Ectoedemia (Lepidoptera: Nepticulidae) are also encountered in other insect groups with intimate plant relationships, including a high degree of monophagy, a preference for ecologically dominant plant families (e.g. Fagaceae, Rosaceae, Salicaceae, and Betulaceae) and a tendency for related insect species to feed on related host plant species. The evolutionary processes underlying these patterns are only partly understood, we therefore assessed the role of allopatry and host plant family shifts in speciation within Ectoedemia.MethodologySix nuclear and mitochondrial DNA markers with a total aligned length of 3692 base pairs were used to infer phylogenetic relationships among 92 species belonging to the subgenus Ectoedemia of the genus Ectoedemia, representing a thorough taxon sampling with a global coverage. The results support monophyletic species groups that are congruent with published findings based on morphology. We used the obtained phylogeny to explore host plant family association and geographical distribution to investigate if host shifts and allopatry have been instrumental in the speciation of these leafmining insects.SignificanceWe found that, even though most species within species groups commonly feed on plants from one family, shifts to a distantly related host family have occasionally occurred throughout the phylogeny and such shifts are most commonly observed towards Betulaceae. The largest radiations have occurred within species groups that feed on Fagaceae, Rosaceae, and Salicaceae. Most species are restricted to one of the seven global biogeographic regions, but within species groups representatives are commonly found in different biogeographic regions. Although we find general patterns with regard to host use and biogeography, there are differences between clades that suggest that different drivers of speciation, and perhaps drivers that we did not examine, have shaped diversity patterns in different clades.

Genetic structure in theGenista ephedroidescomplex (Fabaceae) and implications for its present distribution

The present investigation investigated the genetic structure of a monophyletic group of endemic species belonging to the Genista ephedroides species group: G. bocchierii, G. cilentina, G. demarcoi, G. dorycnifolia, G. ephedroides, G. gasparrinii, G. insularis, G. numidica, G. tyrrhena subsp. tyrrhena, G. tyrrhena subsp. pontiana and G. valsecchiae, all distributed in the western Mediterranean. Using seven plastid microsatellites, 16 populations (288 individuals) were screened. Haplotype fixation was observed in particular for most of the Tyrrhenian taxa (i.e. G. bocchierii, G. cilentina, G. demarcoi, G. ephedroides, G. gasparrinii, G. insularis, G. tyrrhena subsp. tyrrhena and G. valsecchiae). However, although genetic diversity within populations was low [(hS = 0.132 (± 0.056)], a high level of total plastid DNA diversity [hT = 0.866 (± 0.042)] was detected, and analysis of molecular variance indicated that variation is almost exclusively expressed among populations (95.25%). The plastid microsatellites identify two groups of taxa, one including Sardinian taxa and populations of G. tyrrhena subsp. pontiana and the other including two subgroups, one of which includes Sicilian/Aeolian elements and the other with G. numidica/G. cilentina and G. dorycnifolia. Results allow us to consider G. cilentina as originating by recent anthropogenic dispersal and G. tyrrhena subsp. pontiana as a possible stabilized hybrid between local plants and members of the Sardinian group contributing the maternal lineage. The evolutionary history of the group possibly results from the effects of ancient events fostering geodispersal and range contraction, followed by more recent long-range dispersal or geodispersion over Pleistocenic land bridges. © 2015 The Linnean Society of London, Botanical Journal of the Linnean Society, 2015, 177, 607–618.

Crooked Anthos: proposed subgeneric status of Jia (Porifera, Poecilosclerida), with descriptions of four new species

Jia De Laubenfels, 1930 was erected to accommodate Californian Jia jia, a microcionid sponge possessing a unique J-shaped microsclere, subsequently named croca (crook, shepherd's staff). In later revisions, the genus was assigned to the synonymy of Antho Gray, 1867 because of similarity in skeletal and spicular characters with that large worldwide genus. Over the years, two additional species, one Atlantic, one from the Tropical East Pacific, were found to possess the crocae, and here four additional species with these intriguing spicules are described from Indo-West and East Pacific localities. It appears that now seven species, all Antho-like, are known to possess crocae, together distributed over all three oceans. This leads us to hypothesize that crocae are a shared character of a monophyletic group of Antho species and accordingly we propose to revive Jia as a subgenus of Antho. The four new species are Antho (Jia) galapagosensis sp. nov., Antho (Jia) lithisticola sp. nov., Antho (Jia) wunschorum sp. nov. and Antho (Jia) ramosa sp. nov.

Phylogenetic analysis of rhodolith formation in the Corallinales (Rhodophyta)

Although the ecological importance of rhodolith (maerl, free-living coralline algae) beds is well-known, rhodolith-forming species have been neglected in molecular phylogenetic studies. This is the first molecular systematic study aimed at understanding whether the rhodolith habit is a fixed feature in lineages and determining the relationship (phylogenetic vs. environmental) between rhodolith and crustose habits. Phylogenetic relationships of rhodolith-forming species and encrusting coralline algae at generic and species levels were analysed using SSU rDNA and psbA sequences. Extensive sampling in the European North Atlantic, Pacific and Caribbean Mexico of Phymatolithon, Lithothamnion, Lithophyllum and Neogoniolithon taxa forming rhodoliths and crusts was accompanied by examination of type or topotype material. Phylogenetic reconstruction showed that Neogoniolithon contained a monophyletic group of rhodolith-forming species whereas other rhodolith-formers were closely related to encrusting forms in the genera Phymatolithon, Lithothamnion, Mesophyllum, Hydrolithon, Spongites and Sporolithon. DNA analysis showed that the crust-forming Lithophyllum cf. incrustans/dentatum also forms rhodoliths with a stone nucleus that occur on rocky shores. In contrast, species that form beds of non-nucleate rhodoliths (e.g. Neogoniolithon spectabile, N. strictum, Lithophyllum cf. incrustans/dentatum or sp. 1 and Phymatolithon calcareum) rarely form crusts. The rhodolith habit cannot be used to delimit species for taxonomic or identification purposes. Extensive taxonomic revision will be required to deal with problems such as the position of specimens identified as Lithophyllum margaritae in two unrelated lineages.

Description of a new species of Offneria (Hippuritida, Caprinidae) from the lower Aptian of southeast Spain. Stratigraphic, evolutionary, palaeobiogeographic and palaeoenvironmental implications

A new species of Offneria (Caprinidae) Offneria prebetica nov. sp., is described from the Murcia region (Prebetic zone, SE Spain). Its type level is the upper Bedoulian. The key diagnostic character of the new species is the presence on the ventral side of the left valve of an inner row, or double row, of polygonal canals flanked by outer piriform canals with one or two orders of bifurcations. Offneria prebetica nov. sp. is the most advanced species of the genus. Cluster analysis shows the placement of the new species in the monophyletic group of European species, in agreement with its geographic location. Offneria appears to be the most prolific genus of the Caprinidae with species having contrasting ages and palaeobiogeographic distributions. Stratigraphic data from SE Spain indicate that the Offneria lineage was resilient to the environmental perturbations recorded during the late Bedoulian, Offneria prebetica nov. sp. may be used as a time marker for this interval, and its last occurrence was coeval with the “Mid-Aptian extinction event”.

Variation in body size and degree of melanism within a lizards clade: is it driven by latitudinal and climatic gradients?

AbstractBody size (BS) varies in response to several selective pressures. In ectotherms, thermal inertia may affect thermoregulation, since larger BSs increase heat conservation as Bergmann originally stipulated for endotherms. However, Bergmann's rule is controversial in ectotherms. The heat balance hypothesis states that ectotherms' thermoregulatory capability is relevant for trends in BS. In cold climates, larger BSs would be advantageous for small thermoregulating ectotherms, by increasing heat conservation. However, BS implies a delaying effect on heating too; therefore, ectotherms may need another trait to compensate the later effect. Thermal melanism hypothesis posits that melanism increases heat gain, and may be adaptive for animals inhabiting cold climates. We propose that the higher solar radiation absorption from increased melanism may be such a compensatory trait. We expect BS and melanism to increase with latitude in response to seasonal temperatures and solar radiation. To test this, we studied the monophyletic Liolaemus goetschi group of lizard species across its 2200 km (32–48° S latitude) range. We used phylogenetically informed analyses to study geographic variation of BS and melanism (dorsal, ventral and total) in relation to temperatures, thermal amplitude, cloudiness and net solar radiation. Our results show that lizards' BS increases latitudinally in relation to thermal amplitude and temperature. Only ventral melanism varied latitudinally, but all melanism variables varied in response to cloudiness and net radiation. The relationship between BS and melanism was significant and positive in all cases. We suggest thermal inertia may be a fair candidate mechanism explaining geographic variation in BS (heat balance hypothesis), while melanism may influence heat gain according to the thermal melanism hypothesis. However, it remains unclear why latitudinal variation is related to ventral instead of dorsal melanism, and further investigation is needed to clarify the relationship between BS and melanism in light of cold climates.

Phylogenetic Analysis of the African Genus Gilbertiodendron J. Léonard and Related Genera (Leguminosae-Caesalpinioideae-Detarieae)

Premise of research. Gilbertiodendron is a genus endemic to Africa with ∼30 species made up of trees of primary dry-land, riverine, and gallery forests. Recently, the west and central African monotypic genus Pellegriniodendron was merged into Gilbertiodendron. Gilbertiodendron is one of 17 genera that form the exclusively African Berlinia clade, and this study presents the findings of a phylogenetic analysis designed to evaluate the generic limits of Gilbertiodendron and its relationships within the Berlinia clade.Methodology. To test the monophyly of Gilbertiodendron and its relationships with other genera, we analyzed nucleotide sequence data from the nuclear ribosomal internal transcribed spacer and the plastid trnL intron and trnL-F intergenic spacer, using parsimony and Bayesian analyses.Pivotal results. Gilbertiodendron is recovered as monophyletic, including all the samples previously recognized as Pellegriniodendron diphyllum.Conclusions. The placement of Pellegriniodendron in synonymy with Gilbertiodendron is supported by our results. Our analyses suggest that G. diphyllum is the same taxon on both sides of the Dahomey Gap. The G. ogoouense complex is a monophyletic group of species that needs a new taxonomic framework and within which several new species will be described. The phylogenetic framework presented here and the ongoing taxonomic revision should provide the baseline data required for adequate assessment of this group of tree species, of which only eight have been assessed under the International Union for Conservation of Nature’s Red List criteria.

Evolutionary diversification of new Caledonian Araucaria.

New Caledonia is a global biodiversity hotspot. Hypotheses for its biotic richness suggest either that the island is a ‘museum’ for an old Gondwana biota or alternatively it has developed following relatively recent long distance dispersal and in situ radiation. The conifer genus Araucaria (Araucariaceae) comprises 19 species globally with 13 endemic to this island. With a typically Gondwanan distribution, Araucaria is particularly well suited to testing alternative biogeographic hypotheses concerning the origins of New Caledonian biota. We derived phylogenetic estimates using 11 plastid and rDNA ITS2 sequence data for a complete sampling of Araucaria (including multiple accessions of each of the 13 New Caledonian Araucaria species). In addition, we developed a dataset comprising 4 plastid regions for a wider taxon sample to facilitate fossil based molecular dating. Following statistical analyses to identify a credible and internally consistent set of fossil constraints, divergence times estimated using a Bayesian relaxed clock approach were contrasted with geological scenarios to explore the biogeographic history of Araucaria. The phylogenetic data resolve relationships within Araucariaceae and among the main lineages in Araucaria, but provide limited resolution within the monophyletic New Caledonian species group. Divergence time estimates suggest a Late Cretaceous-Cenozoic radiation of extant Araucaria and a Neogene radiation of the New Caledonian lineage. A molecular timescale for the evolution of Araucariaceae supports a relatively recent radiation, and suggests that earlier (pre-Cenozoic) fossil types assigned to Araucaria may have affinities elsewhere in Araucariaceae. While additional data will be required to adequately resolve relationships among the New Caledonian species, their recent origin is consistent with overwater dispersal following Eocene emersion of New Caledonia but is too old to support a single dispersal from Australia to Norfolk Island for the radiation of the Pacific Araucaria sect. Eutacta clade.

Phylogenetic signal in growth and reproductive traits and in their plasticity: theDescurainiaradiation in the Canary Islands

Despite the extensive use of phylogenetic methods in comparative plant biology, there is little information on how traits and their plastic responses can be affected by phylogenetic constraints (i.e. limitations in phenotypic expression resulting from the phylogenetic history of a lineage), particularly in plant radiations that may have occurred over a relatively short time period. In this study, we examined phylogenetic constraints in a monophyletic group of species of Descurainia (Brassicaceae) endemic to the Canary Islands. We measured growth and reproductive traits in a glasshouse experiment representing 17 populations of eight taxa previously analysed in a phylogenetic context. Two water availability treatments were used to assess the plasticity of the examined traits. Most of the traits did not show strong phylogenetic signal; only weak evidence for phylogenetic constraint was found in traits related to reproduction (total number of flowers, onset of flowering) and biomass allocation to roots. Substantial levels of plasticity were observed in all the examined traits, but plasticity showed little interaction between treatment and taxon, suggesting little divergence among taxa. Our study provides evidence that phylogenetic constraints in these quantitative traits, including their plastic expression, have not played a significant role in the pattern of phenotypic diversification of this island plant group. Phenotypic plasticity may thus have favoured adjustment to the habitats occupied by each species during the radiation process. © 2014 The Linnean Society of London, Botanical Journal of the Linnean Society, 2014, 174, 384–398.