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BackgroundFungus farming is an unusual life style in insects that has evolved many times in the wood boring weevils named ‘ambrosia beetles’. Multiple occurrences of this behaviour allow for a detailed comparison of the different origins of fungus farming through time, its directionality, and possible ancestral states. We tested these hypotheses with a phylogeny representing the largest data set to date, nearly 4 kb of nucleotides from COI, EF-1α, CAD, ArgK, 28S, and 200 scolytine taxa.ResultsPhylogenetic analyses using Bayesian or parsimony approaches placed the root of Scolytinae close to the tribe Scolytini and Microborus, but otherwise indicated low resolution at older nodes. More recent clades were well resolved, including ten origins of fungus farming. There were no subsequent reversals to bark or phloem feeding in the fungus farming clades. The oldest origin of fungus farming was estimated near 50 Ma, long after the origin of Scolytinae (100-120 Ma). Younger origins included the species rich Xyleborini, dated to 21 Ma. Sister group comparisons and test of independence between traits indicated that neither gregarious larval feeding nor regular inbreeding by sibling mating was strongly correlated with the origin of fungus farming.ConclusionOrigins of fungus farming corresponded mainly with two periods of global warming in the Cenozoic era, which were characterised by broadly distributed tropical forests. Hence, it seems likely that warm climates and expanding tropical angiosperm forests played critical roles in the successful radiation of diverse fungus farming groups. However, further investigation will likely reveal additional biological factors that promote fungus farming.

Cogongrass, Imperata cylindrica (L.) Palisot de Beauvois (Cyperales: Poaceae), is a serious invasive weed in the southeastern USA. Surveys for potential biological control agents of cogongrass were conducted in Asia and East Africa from 2013 to 2016. Several insect herbivores were found that may have restricted host ranges based on field collection data and life histories. Stemborers in the genus Acrapex (Lepidoptera: Noctuidae) were collected from cogongrass in Tanzania, Uganda, and Japan. In the Philippines, larvae of Emmalocera sp. (Lepidoptera: Pyralidae) and Chilo sp. (Lepidoptera: Crambidae) were found boring in cogongrass. Cecidomyiid midges were found in both Japan and Indonesia. A Japanese midge identified as a Contarinia sp. (Diptera: Cecidomyiidae) caused deformation of the stem, whereas the Indonesian midge Orseolia javanica Kieffer & van Leeuwen-Reijinvaan (Diptera: Cecidomyiidae) induced the formation of a basal stem gall. Previous research suggested that the host range of O. javanica was restricted to cogongrass.

The possibility of gene tree incongruence in a species-level phylogenetic analysis of the genus Ips (Coleoptera: Scolytidae) was investigated based on mitochondrial 16S rRNA (16S) and nuclear elongation factor-1 alpha (EF-1 alpha) sequences, and existing cytochrome oxidase I (COI) and nonmolecular data sets. Separate cladistic analyses of the data partitions resulted in partially discordant most-parsimonious trees but revealed only low conflict of the phylogenetic signal. Interactions among data partitions, which differed in the extent of sequence divergence (COI > 16S > EF-1 alpha), base composition, and homoplasy, revealed that much of the branch support emerges only in the simultaneous analysis, particularly for deeper nodes in the tree, which are almost entirely supported through "hidden support" (sensu Gatesy et al., Cladistics 15:271-313, 1999). Apparent incongruence between data partitions is in part due to suboptimal alignments and bias of character transformations, but little evidence supports invoking incongruent phylogenetic histories of genetic loci. There is also no justification for eliminating or downweighting gene partitions on the basis of their apparent homoplasy or incongruence with other partitions, because the signal emerges only in the interaction of all data. In comparison with traditional taxonomy, the pini, plastographus, and perturbatus groups are polyphyletic, whereas the grandicollis group is monophyletic except for inclusion of the (monophyletic) calligraphus group. The latidens group and some European species are distantly related and closer to other genera within Ipini. Our robust cladogram was used to revise the classification of Ips. We provide new diagnoses for Ips and four subgeneric taxa.

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