Tribe Xyleborini Research Articles

Phylogeny of haplo–diploid, fungus‐growing ambrosia beetles (Curculionidae: Scolytinae: Xyleborini) inferred from molecular and morphological data

Cognato, A. I., Hulcr, J., Dole, S. A. & Jordal, B. H. (2010). Phylogeny of haplo‐diploid, fungus‐growing ambrosia beetles (Curculionidae: Scolytinae: Xyleborini) inferred from molecular and morphological data. —Zoologica Scripta, 40, 174–186.The ambrosia beetle tribe Xyleborini currently contains 30 genera and approximately 1200 species which are distributed throughout worldwide forests with most diversity located in the tropics. They also represent the most invasive scolytines in North America. Despite economic concerns and biological curiosity with this group, a comprehensive understanding of generic boundaries and the evolutionary relationship among species is lacking. In this study, we include 155 xyleborine species representing 23 genera in parsimony and Bayesian analyses using 3925 nucleotides from mitochondrial (COI) and nuclear genomes (28S, ArgK, CAD, EF‐1α) and 39 morphological characters. The phylogenies resulting from the parsimony analyses, which treated gap positions either as missing or fifth character states, and the Bayesian analysis were generally similar. Clades with high support or posterior probabilities were found in all trees, while those with low support were not recovered by all analyses. Fourteen of the 23 genera were monophyletic although not all relationships among the genera were resolved. We show monophyly of several species groups associated with particular morphological and biological characters and suggest recognition of these groups as genera. Most interesting was the monophyly of South and Central American species representing several genera. This finding suggests recent and fast radiation of xyleborines in the New World accompanied by morphological and biological diversification.

A Review of the Ambrosia Beetle Genus Cryptoxyleborus Schedl (Coleoptera: Curculionidae: Scolytinae)

Abstract The species of the Oriental and Papuasian genus Cryptoxyleborus Schedl in the Scolytine tribe Xyleborini are reviewed. Two new species, C. cuneatus and C. mawdsleyi are described from Brunei Darussalam. The following new synonymy is proposed: Cryptoxyleborus oxyurus Schedl ( = Cryptoxyleborus shoreae Browne syn.n.), Cryptoxyleborus vestigator (Schedl) ( = Platypus goilalae Schedl syn.n.). The following new combinations are given: Cryptoxyleborus acutus (Schedl) comb.n., Cryptoxyleborus percuneolus (Schedl) comb.n., both from Xyleborus; Microperus nanus (Browne) comb.n. from Cryptoxyleborus. A lectotype is designated for C. percuneolus, and the previously unknown male is described. A key is given to 18 species currently included in the genus, and new distributional records for many species. All species of Cryptoxyleborus are ambrosia beetles associated with dead or dying trees of the family Dipterocarpaceae, but are not of significant economic importance.

Elongation Factor 1 α resolves the monophyly of the haplodiploid ambrosia beetles Xyleborini (Coleoptera: Curculionidae)

Elongation Factor 1-alpha was used to test the monophyly of the wood boring beetle tribe Xyleborini, where all species are haplodiploid and perform regular inbreeding by brother-sister mating. Due to their feeding requirements, being highly dependent on ophiostomatoid fungi which they cultivate in wood tunnels, monophyly may be expected due to nutritional constraints. During the course of analyses, two copies of EF-1alpha were amplified in these beetles, differing in intron structure. The high similarity between paralogous amino acid sequences (93-94%) indicates a rather recent duplication in beetles, but phylogenetic analyses of different copies in insects rejected this hypothesis. Subsequent phylogenetic analyses of eighty orthologous sequences from Xyleborini and allied taxa, using the single-intron bearing copy, were greatly improved in resolution and node support by including the intron sequences (c. 60 bp). Most analyses resulted in a monophyletic Xyleborini, implying one origin of fungus feeding in this tribe. However, clear evidence for a polyphyletic Xyleborus and three more xyleborine genera calls for further revision of xyleborine classification.

Degradação da Madeira de Seis Essências Arbóreas Disposta Perpendicularmente ao Solo Causada por Scolytidae (Coleoptera)

Avaliou-se a degradacao causada por Scolytidae (Coleoptera) em madeira de seis essencias arboreas, Clitoria fairchildiana Howard, Samanea saman (Jacq.) Merr, Mimosa caesalpiniaefolia Benth, Eucalyptus citriodora Hook, Lophantera lactescens Ducke e Gmelina arborea Roxb. O ensaio de campo foi realizado no sub-bosque de um fragmento florestal no campus da Universidade Federal Rural do Rio de Janeiro, de setembro de 1998 a abril de 1999. Cinco amostras de cada essencia foram expostas a acao de Scolytidae, dispondo-as em posicao perpendicular em relacao ao solo. Seis observacoes preliminares semanais foram feitas nas 30 amostras e a infestacao ocorrida foi avaliada. Posteriormente, uma subamostra de cada essencia foi retirada quinzenalmente para avaliacao em laboratorio das perfuracoes e galerias feitas por adultos da familia Scolytidae, alem do numero de larvas. Vinte especies foram coletadas, distribuidas em dez generos: Ambrosiodmus ,Coccotrypes, Coptoborus, Cryptocarenus, Hypothenemus, Premnobius.Theoborus, Xyleborinus, Xyleborus e Xylosandrus. As madeiras das essencias C. fairchildiana e S. saman foram as mais atacadas, principalmente por Hypothenemus eruditus Westwood e por especies da tribo Xyleborini, sendo apropriadas para o desenvolvimento de Scolytidae pelo numero significativo de larvas encontrado. A reducao do numero de adultos e larvas de Scolytidae coletados foi diretamente proporcional ao tempo de exposicao dos toletes. As madeiras com menor reacao fisiologica da casca ao corte foram mais rapidamente degradadas pelas coleobrocas. Estudos futuros sao necessarios para determinar a natureza dos compostos emitidos por estas madeiras que as tornam mais atrativas que outras, quando expostas em iguais condicoes.

Origin of a haplodiploid beetle lineage

The beetle family Scolytidae includes several groups having regular sib–mating and extremely female–biased sex ratios. Two such groups are known to include haplodiploid species: (i) the tribe Xyleborini and (ii) Coccotrypes and related genera within the tribe Dryocoetini. Relationships of these groups have been controversial. We analysed elongation factor 1–α (852 bp) and cytochrome oxidase 1 (1179 bp) sequences for 40 species. The most–parsimonious trees imply a single origin of haplodiploidy uniting Xyleborini (approximately 1200 species) and sib–mating Dryocoetini (approximately 160 species). The sister–group of the haplodiploid clade is the outcrossing genus Dryocoetes . The controversial genus Premnobius is outside the haplodiploid clade. Most haplodiploid scolytids exploit novel resources, ambrosia fungi or seeds, but a few have the ancestral habit of feeding on phloem. Thus, scolytids provide the clearest example of W. D. Hamilton9s scenario for the evolution of haplodiploidy (life under bark leading to inbreeding and hence to female–biased sex ratios through haplodiploidy) and now constitute a unique opportunity to study diplodiploid and haplodiploid sister–lineages in a shared ancestral habitat. There is some evidence of sex determination by maternally inherited endosymbiotic bacteria, which may explain the consistency with which female–biased sex ratios and close inbreeding have been maintained.

REVIEW OF THE TRIBE XYLEBORINI IN AMERICA NORTH OF MEXICO (COLEOPTERA: SCOLYTIDAE)

AbstractThis review of the tribe Xyleborini (Coleoptera: Scolytidae) includes two genera,XyleborusEichhoff, with 17 species, andXylosandrusReitter, containing 3 species. All species are described and most are illustrated. Keys for the separation of the genera and species are provided. Distributional and biological data are given. New combinations are:Xyleborus obliquus(Leconte) (=Pityophthorus obliquusLeconte);X.lecontei(Hopkins) (=Ambrosiodmus leconteiHopkins), andX.sayi(Hopkins) (=Anisandrus sayiHopkins). New synonymies are:Xyleborus obliquus(Leconte) (=Ambrosiodmus linderaeHopkins);X.obesusLeconte (=Anisandrus populiSwaine);X.ferrugineus(Fabricius) (=X.retusicollisZimmerman andX.soltauiHopkins);X.xylographus(Say) (=X.inermisEichhoff andX.planicollisZimmerman);X.volvulus(Fabricius) (=X.schwarziHopkins andX.rileyiHopkins), andX.howardiHopkins (=X.fitchiHopkins). A Japanese species,X.rubricollisEichhoff, is reported from the United States for the first time. A neotype is designated forX.xylographus(Say).