Fruit type in the genus Lithocarpus (Fagaceae) includes both classic oak acorns and novel modifications. Bornean taxa with modified fruits can be separated into two sections (Synaedrys and Lithocarpus) based on subtle shape differences. By following strict criteria for homology and representation, this variation in shape can be captured and the sections distinguished by using elliptic Fourier or eigenshape analysis. Phenograms of fruit shape, constructed by using restricted maximum likelihood techniques and these morphometric descriptors, were incorporated into combined and comparative analyses with molecular sequence data from the internal transcribed spacer (ITS) region of the nuclear rDNA, using branch-weighted matrix representation. The combined analysis strongly suggested independent derivation of the novel fruit type in the two sections from different acornlike ancestors, while the comparative analysis indicated frequent decoupling between the molecular and morphological changes as inferred at well-supported nodes. The acorn fruit type has undergone little modification between ingroup and outgroup, despite large molecular distance. Greater morphological than molecular change was inferred at critical transitions between acorn and novel fruit types, particularly for section Lithocarpus. The combination of these two different types of data improved our understanding of the macroevolution of fruit type in this difficult group, and the comparative analysis highlighted the significant incongruities in evolutionary pattern between the two datasets.
The genetic variation of Trigonobalanus verticillata, the most recently described genus of Fagaceae, was studied using chloroplast DNA sequences and AFLP fingerprinting. This species has a restricted distribution that is known to include seven localities in tropical lower montane forests in Malaysia and Indonesia. A total of 75 individuals were collected from Bario, Kinabalu, and Fraser's Hill in Malaysia. The sequences of rbcL, matK, and three non-coding regions (atpB-rbcL spacer, trnL intron, and trnL-trnF spacer) were determined for 19 individuals from these populations. We found a total of 30 nucleotide substitutions and four length variations, which allowed identification of three haplotypes characterizing each population. No substitutions were detected within populations, while the tandem repeats in the trnL -trnF spacer had a variable repeat number of a 20-bp motif only in Kinabalu. The differentiation of the populations inferred from the cpDNA molecular clock calibrated with paleontological data was estimated to be 8.3 MYA between Bario and Kinabalu, and 16.7 MYA between Fraser's Hill and the other populations. In AFLP analysis, four selective primer pairs yielded a total of 431 loci, of which 340 (78.9%) were polymorphic. The results showed relatively high gene diversity (H(S) = 0.153 and H(T) = 0.198) and nucleotide diversity (pi(S) = 0.0132 and pi(T) = 0.0168) both within and among the populations. Although the cpDNA data suggest that little or no gene flow occurred between the populations via seeds, the fixation index estimated from AFLP data (F(ST) = 0.153 and N(ST) = 0.214) implies that some gene flow occurs between populations, possibly through pollen transfer.
Natural history collections and tropical tree diversity are both treasure troves of biological and evolutionary information, but their accessibility for scientific study is impeded by a number of properties. DNA in historical specimens is generally highly fragmented, complicating the recovery of high-grade genetic material. Furthermore, our understanding of hyperdiverse, wide-spread tree assemblages is obstructed by extensive species ranges, fragmented knowledge of tropical tree diversity and phenology, and a widespread lack of species-level diagnostic characters, prohibiting the collecting of readily identifiable specimens which can be used to build, revise or strengthen taxonomic frameworks. This, in turn, delays the application of downstream conservation action. A sizable component of botanical collections are sterile-thus eluding identification and are slowing down progress in systematic treatments of tropical biodiversity. With rapid advances in genomics and bioinformatic approaches to biodiversity research, museomics is emerging as a new field breathing life into natural collections that have been built up over centuries. Using MIGseq (multiplexed ISSR genotyping by sequencing), we generated 10,000s of short loci, for both freshly collected materials and museum specimens (aged >100 years) of Lithocarpus-a widespread tropical tree genus endemic to the Asian tropics. Loci recovery from historical and recently collected samples was not affected by sample age and preservation history of the study material, underscoring the reliability and flexibility of the MIGseq approach. Phylogenomic inference and biogeographic reconstruction across insular Asia, highlights repeated migration and diversification patterns between continental regions and islands. Results indicate that co-occurring insular species at the extremity of the distribution range are not monophyletic, raising the possibility of multiple independent dispersals along the outer edge of Wallacea. This suggests that dispersal of large seeded tree genera throughout Malesia and across Wallacea may have been less affected by large geographic distances and the presence of marine barriers than generally assumed. We demonstrate the utility of MIGseq in museomic studies using non-model taxa, presenting the first range-wide genomic assessment of Lithocarpus and tropical Fagaceae as a proof-of-concept. Our study shows the potential for developing innovative genomic approaches to improve the capture of novel evolutionary signals using valuable natural history collections of hyperdiverse taxa.
The amended diagnosis of the genus Pratylenchoides and list of its valid species with synonyms are given. All the efficient diagnostic characters are listed. Modern taxonomic standard for the description of Pratylenchoides species is proposed; it may be used also in taxonomic databases. Tabular and text keys for all species of the genus are given. Five following groups are considered within the genus Pratylenchoides. The group arenicola differs from other groups in the primitive adanal bursa type; the groups magnicauda, crenicauda, ritteri, and megalobatus differ from each other in the position of cardium along the body axis in relation to the pharyngeal gland nuclei, pharynx types are named according to the stages of its evolution from the primitive tylenchoid pharynx (cardium situated posteriorly) to the advanced hoplolaimoid one (cardium situated anteriorly). Diagnoses and species compositions of the groups are given. Basing on the matrix of species characters, the dendrogram has been generated for all species of Pratylenchoides and for all characters (UPGMA, distance, mean character difference, random, characters ordered). Taking in view that the PAUP software gives equal weights to all characters, including the most important ones which define the prognostic species groups, the separate dendrograms for each prognostic species group were generated using the same above mentioned tree parameters. On the base of the records of Pratylenchoides species the matrices of plant host ranges, geographic distribution, and preferred soil-climatic conditions were developed. The dendrograms of the faunal similarities were generated using these matrices, with conclusions on a possible origin and evolution of the genus. The genus evolved from the flood lands with swampy soils and prevalence of dicotyledons (herbaceous Lamiaceae and woody Salicaceae families) to the forest mainland communities with balanced humidity and predominance of herbaceous Poaceae and Fabaceae with woody Fagaceae, Betulaceae, and Oleaceae. The leading factor of the evolutional adaptation to soil-climatic conditions was the factor of humidity, but its significance gradually decreased with the host change to more advanced plant taxa adapted to the communities with more dry balanced humidity. The genus took its origin on the south shores of Laurasia in the Cainozoe. Later, when Hindistant and Arabian Peninsula joined with Laurasia creating the Himalayas barrier, the Pratylenchoides spp. distributed by two branches: the northern one moved into Central Asia, East Europe and North America, and the south branch came into Indo-Malaya, West Asia and the north of Africa. The remnants of the ancient species groups remain in West Europe and East Asia. In the North America the genus gave an origin to its sister genus Apratylenchoides, which spread to the south up to Antarctica; another advanced branch spread in the North America reaching Alaska.