Analía A. Lanteri

Are flightless Galapaganus weevils older than the Galápagos Islands they inhabit

The 15 species in the weevil genus Galapaganus Lanteri 1992 (Entiminae: Curculionidae: Coleoptera) are distributed on coastal Perú and Ecuador and include 10 flightless species endemic to the Galápagos islands. These beetles thus provide a promising system through which to investigate the patterns and processes of evolution on Darwin’s archipelago. Sequences of the mtDNA locus encoding cytochrome oxidase subunit I (COI) were obtained from samples of seven species occurring in different ecological zones of the oldest south-eastern islands: San Cristóbal, Española and Floreana, and the central island Santa Cruz. The single most parsimonious tree obtained shows two well-supported clades that correspond to the species groups previously defined by morphological characters. Based on a mtDNA clock calibrated for arthropods, the initial speciation separating the oldest species, G. galapagoensis (Linell) on the oldest island, San Cristóbal, from the remaining species in the Galápagos occurred about 7.2 Ma. This estimate exceeds geological ages of the extant emerged islands, although it agrees well with molecular dating of endemic Galápagos iguanas, geckos and lizards. An apparent explanation for the disagreement between geological and molecular time-frames is that about 7 Ma there were emerged islands which subsequently disappeared under ocean waters. This hypothesis has gained support from the recent findings of 11-Myr-old submarine seamounts (sunken islands), south-east of the present location of the archipelago. Some species within the darwini group may have differentiated on the extant islands, 1–5 Ma.

Colonization history, ecological shifts and diversification in the evolution of endemic Galápagos weevils

Mitochondrial DNA sequence data were obtained for eight species of flightless Galapaganus endemic weevils and one winged close relative in order to study their colonization history and modes of diversification in the Galápagos Archipelago. Contrary to most other insular radiations, the phylogeny estimates we recovered for Galapaganus do not follow the progression rule of island biogeography. The penalized likelihood age estimates of colonization of the archipelago exceed the age of the emerged islands and underscore the potential role of now sunken seamounts for the early evolution of Galapaganus. The phylogeny proposes one intra‐island origin for Galapaganus endemics, but monophyly tests suggest a larger contribution of in‐situ speciation on older islands. Generalist habitat preferences were reconstructed as ancestral while shifts to highland habitats were reconstructed as having evolved independently on different islands. Magnitudes and patterns of diversification rate were found to differ between older and younger islands. Our analyses reveal that the colonization sequence of islands and timing of colonization of Galapaganus could be linked with the geological and volcanic history of the islands in a rather complex scenario. Even though most islands appear to have been colonized soon after their emergence, there are notable deviations from the pattern of sequential colonization expected under the progression rule when considering only the extant emerged islands. Patterns of diversification rate variation on older and younger islands correspond to the volcanic activity or remnants of such activity, while the pattern of independent evolution of restricted habitat preferences in different islands suggests that habitat shifts could also have contributed to species diversity in Galapaganus.

Incongruence Between Morphological and Mitochondrial-DNA Characters Suggests Hybrid Origins of Parthenogenetic Weevil Lineages (Genus Aramigus)

An expanded matrix of morphological characters for the genus Aramigus (Coleoptera: Curculionidae), which includes numerous polyploid parthenogenetic lineages, was compared and combined with a published matrix of mitochondrial DNA (mtDNA) characters. The matrix of morphological characters provides little resolution of the A. tessellatus and A. uruguayensis species complexes but does resolve previously unresolved relationships among other morphologically defined species (A. globoculus + A. intermedius, A. curtulus + A. planioculus). The morphological and mtDNA characters are significantly incongruent (0.435 < or = IM < or = 0.463; IMF = 0.0735), according to the tests of Farris et al. (P = 0.010) and Templeton (P < 0.005), probably because of hybrid origins of polyploid parthenogenetic lineages. For the few sexual lineages included in both matrices, morphology and mtDNA provide congruent estimates of phylogeny. In spite of recent injunctions against combining data sets that are incongruent because of differing histories, the results of the combined analyses were used to select one of the most-parsimonious mtDNA trees as the best estimate of maternal-lineage genealogy and to reconstruct the evolution of parthenogenesis under the assumption that transitions from sexuality to parthenogenesis are irreversible. Where cytogenetically justified, as in weevils, the irreversibility assumption is useful for producing conservative estimates of the age of parthenogenetic lineages in spite of potential sampling bias against sexuals.

Diversity of Boll Weevil Populations in South America: A Phylogeographic Approach

A phylogeographic approach was conducted to assess the geographic structure and genetic variation in populations of the boll weevil Anthonomus grandis, which is the most harmful insect pest of cotton in the Americas. COI and COII mitochondrial gene sequences were analyzed to test a former hypothesis on the origin of the boll weevil in Argentina, Brazil and Paraguay, using samples from Mexico and USA as putative source populations. The analysis of variability suggests that populations from South American cotton fields and nearby disturbed areas form a phylogroup with a central haplotype herein called A, which is the most common and widespread in USA and South America. The population from Texas has the A haplotype as the most frequent and gathers in the same group as the South American populations associated with cotton. The sample from Tecomán (México) shows high values of within-nucleotide divergence, shares no haplotype in common with the South American samples, and forms a phylogroup separated by several mutational steps. The sample from Iguazú National Park (Misiones Province, Argentina) has similar characteristics, with highly divergent haplotypes forming a phylogroup closer to the samples from cotton fields, than to the Mexican group. We propose that in South America there are: populations with characteristics of recent invaders, which would be remnants of “bottlenecks” that occurred after single or multiple colonization events, probably from the United States, and ancient populations associated with native forests, partially isolated by events of historical fragmentation.

Weevils Injurious for Roots of Citrus in São Paulo State, Brazil

Ten species of broad nosed weevils belonging to Entiminae, Naupactini, are recorded as harmful for roots of citrus in Sao Paulo state, Brazil. Most species belong to Naupactus Dejean, N. rivulosus (Olivier), N. tarsalis Boheman, N. curtus Boheman, N. navicularis Boheman, N. versatilis Hustache, N. ambiguus Boheman, and N. cervinus Boheman; one species was assigned to Teratopactus Heller, T. nodicollis (Boheman); one to Parapantomorus, P. fluctuosus Schoenherr (Boheman) and one to Symmathetes Schoenherr (a genus herein reinstated), S. kollari Schoenherr. Larvae live in soil and bore on roots of the trees, causing more damages than adults, that feed on leaves. The main goal of this paper is to provide a key, diagnosis and habitus photographs of the species, in order to facilitate their identification. We also provide information on their geographic range in Brazil and previous plant associations, and we discuss some relevant biological features, especially those related to oviposition habits.

Wolbachia infection in the tribe Naupactini (Coleoptera, Curculionidae): association between thelytokous parthenogenesis and infection status.

Several parthenogenetic species of broad‐nosed weevils exist, some of them of economic importance because of their pest status. Screening of the maternally inherited Wolbachia bacterium in 29 weevils of the tribe Naupactini, using multilocus sequence typing allowed us to assess a significant correlation between asexuality and infection, and suggests an involvement of Wolbachia in the origin of this reproductive mode. The nine Wolbachia strains retrieved from the Naupactini belong to the B supergroup. Phylogenetic analysis of these strains, along with other 23 strains obtained from arthropods and nematodes, supports previous hypotheses that horizontal transfer of Wolbachia amongst species from unrelated taxa has been pervasive.

Phylogeny of the Pantomorus–Naupactus complex based on morphological and molecular data (Coleoptera: Curculionidae)

The Pantomorus–Naupactus complex is a Neotropical group of broad‐nosed weevils (Coleoptera: Curculionidae) including several parthenogenetic species usually assigned to the genera Naupactus Dejean, Pantomorus Schoenherr, Asynonychus Crotch, Aramigus Horn, Eurymetopus Schoenherr and Graphognathus Buchanan. Sixteen species were studied to test hypotheses on the monophyly of these genera, and on the origin of the parthenogenetic lineages. A matrix of 30 morphological characters and 999 positions of the Cytochrome Oxidase I gene, was analyzed with separate partitions and simultaneously, under equal and implied weights, and with different transversion/transitions costs. The ILD test indicates that the incongruence between the molecular and morphological data is not significant. Under equal weights, the molecular data resulted in a single tree and morphology in 34 trees; under implied weights morphology gave a different tree, and under TV:TS ≥ 4:1 molecular and combined analyses resulted in the same optimal tree. According to the latter, Naupactus includes Graphognathus, and is thus paraphyletic and basal regarding remaining genera, Pantomorus is polyphyletic and includes Aramigus and Asynonychus, and Eurymetopus is monophyletic. The species in which apomictic parthenogenesis has been verified (Aramigus tessellatus, Asynonychus cervinus and Graphognathus lecuoloma), belong to different clades of the Pantomorus‐Naupactus complex, with basal sexual relatives.

Key to higher taxa of South American weevils based on adult characters (Coleoptera, Curculionoidea)

Los gorgojos (Coleoptera: Curculionoidea) de America del Sur se clasifican actualmente en las siguientes familias y subfamilias: Nemonychidae (Rhinorhynchinae), Anthribidae (Anthribinae), Belidae (Belinae y Oxycoryninae), Attelabidae (Attelabinae y Rhynchitinae), Brentidae (Apioninae y Brentinae), Caridae (Carinae) y Curculionidae (Erirhininae, Dryophthorinae, Entiminae, Aterpinae, Gonipterinae, Rhythirrininae, Thecesterninae, Eugnominae, Hyperinae, Curculioninae, Cryptorhynchinae, Mesoptiliinae (= Magdalidinae), Molytinae, Baridinae, Lixinae, Conoderinae (= Zygopinae), Cossoninae, Scolytinae y Platypodinae). En la presente contribucion se brinda una clave dicotomica para la identificacion de las siete familias y 28 subfamilias de Curculionoidea sudamericanos, y para varias (21) tribus de Curculioninae y Molytinae. Estas tribus son Curculionini, Anthonomini, Ceutorhynchini, Derelomini, Otidocephalini, Erodiscini, Camarotini, Piazorhinini, Prionobrachiini, Smicronychini, Rhamphini y Tychiini, dentro de Curculioninae, e Hylobiini, Pissodini, Conotrachelini, Cleogonini, Sternechini, Pacholenini, Cholini, Petalochilini y Amalactini, dentro de Molytinae. La mayoria de estas tribus han sido clasificadas como subfamilias en los esquemas tradicionales. La clave se basa principalmente en caracteres morfologicos externos, e incluye ademas datos de la genitalia, piezas bucales, y rasgos biologicos de las especies. El trabajo provee definiciones e ilustraciones de los caracteres diagnosticos utilizados en la clave

Mito-nuclear genetic comparison in a Wolbachia infected weevil: insights on reproductive mode, infection age and evolutionary forces shaping genetic variation.

BackgroundMaternally inherited endosymbionts like Wolbachia pipientis are in linkage disequilibrium with the mtDNA of their hosts. Therefore, they can induce selective sweeps, decreasing genetic diversity over many generations. This sex ratio distorter, that is involved in the origin of parthenogenesis and other reproductive alterations, infects the parthenogenetic weevil Naupactus cervinus, a serious pest of ornamental and fruit plants.ResultsMolecular evolution analyses of mitochondrial (COI) and nuclear (ITS1) sequences from 309 individuals of Naupactus cervinus sampled over a broad range of its geographical distribution were carried out. Our results demonstrate lack of recombination in the nuclear fragment, non-random association between nuclear and mitochondrial genomes and the consequent coevolution of both genomes, being an indirect evidence of apomixis. This weevil is infected by a single Wolbachia strain, which could have caused a moderate bottleneck in the invaded population which survived the initial infection.ConclusionsClonal reproduction and Wolbachia infection induce the coevolution of bacterial, mitochondrial and nuclear genomes. The time elapsed since the Wolbachia invasion would have erased the traces of the demographic crash in the mtDNA, being the nuclear genome the only one that retained the signal of the bottleneck. The amount of genetic change accumulated in the mtDNA and the high prevalence of Wolbachia in all populations of N. cervinus agree with the hypothesis of an ancient infection. Wolbachia probably had great influence in shaping the genetic diversity of N. cervinus. However, it would have not caused the extinction of males, since sexual and asexual infected lineages coexisted until recent times.

Nuclear and mitochondrial sequences confirm complex colonization patterns and clear species boundaries for flightless weevils in the Galapagos archipelago

Nuclear sequence data were collected from endemic Galápagos species and an introduced close relative, and contrasted with mitochondrial DNA sequences, continuing investigation into the colonization history and modes of diversification in the weevil genus Galapaganus. The current combined phylogeny together with previously published penalized likelihood age estimates builds a complex picture of the archipelagos colonization history. The present reconstruction relies on submerged platforms to explain the early divergence of the young southern Isabela endemics or the Española or San Cristobal populations. Diversity is later built through inter-island divergence starting on older islands and continuing on two simultaneous tracks towards younger islands. The amount of diversity generated through intra-island processes is skewed towards older islands, suggesting that island age significantly influences diversity. Phylogenetic concordance between nuclear and mitochondrial datasets and well-supported monophyletic species in mitochondrial derived topologies appear to reject the possibility of inter-species hybridization. These clear species boundaries might be related to the tight host associations of adult weevils in discrete ecological zones. If shared hosts facilitate hybridization, then host- or habitat-promoted divergences could prevent it, even in the case of species that share islands, since the altitudinal partitioning of habitats minimizes range overlap.