Differential Gene Profiling of the Heartwood Formation Process in Taiwania cryptomerioides Hayata Xylem Tissues.

Taiwania (Taiwania cryptomerioides) is an important tree species in Taiwan because of the excellent properties of its wood and fascinating color qualities of its heartwood (HW), as well as the bioactive compounds therein. However, limited information is available as to the HW formation of this species. The objective of this research is to analyze the differentially expressed genes (DEGs) during the HW formation process from specific Taiwania xylem tissues, and to obtain genes that might be closely associated with this process. The results indicated that our analyses have captured DEGs representative to the HW formation process of Taiwania. DEGs related to the terpenoid biosynthesis pathway were all up-regulated in the transition zone (TZ) to support the biosynthesis and accumulation of terpenoids. Many DEGs related to lignin biosynthesis, and two DEGs related to pinoresinol reductase (PrR)/pinoresinol lariciresinol reductase (PLR), were up-regulated in TZ. These DEGs together are likely involved in providing the precursors for the subsequent lignan biosynthesis. Several transcription factor-, nuclease-, and protease-encoding DEGs were also highly expressed in TZ, and these DEGs might be involved in the regulation of secondary metabolite biosynthesis and the autolysis of the cellular components of ray parenchyma cells in TZ. These results provide further insights into the process of HW formation in Taiwania.

Historical demography of four gecko species specializing in boulder cave habitat: Implications in the evolutionary dead end hypothesis and conservation.

Specialization in narrow ecological niches may not only help species to survive in competitive or unique environments but also contribute to their extermination over evolutionary time. Although the "evolutionary dead end" hypothesis has long been debated, empirical evidence from species with detailed information on niche specialization and evolutionary history remains rare. Here we use a group of four closely related Cnemaspis gecko species that depend highly on granite boulder caves in the Mekong Delta to investigate the potential impact of ecological specialization on their evolution and population dynamics. Isolated by unsuitable floodplain habitats, these boulder-dwelling geckos are among the most narrowly distributed Squamata in the world. We applied several coalescence-based approaches combined with the RAD-seq technique to estimate their divergence times, gene flow and demographic fluctuations during the speciation and population differentiation processes. Our results reveal long-term population shrinkage in the four geckos and limited gene flow during their divergence. The results suggest that the erosion and fragmentation of the granite boulder hills have greatly impacted population divergence and declines. The habitat specialization of these geckos has led to fine-scaled speciation in these granite rocky hills; in contrast, specialization might also have pushed these species toward the edge of extinction. Our study also emphasizes the conservation urgency of these vulnerable, cave-dependent geckos.

Inferring the geographic mode of speciation by contrasting autosomal and sex-linked genetic diversity.

When geographic isolation drives speciation, concurrent termination of gene flow among genomic regions will occur immediately after the formation of the barrier between diverging populations. Alternatively, if speciation is driven by ecologically divergent selection, gene flow of selectively neutral genomic regions may go on between diverging populations until the completion of reproductive isolation. It may also lead to an unsynchronized termination of gene flow between genomic regions with different roles in the speciation process. Here, we developed a novel Approximate Bayesian Computation pipeline to infer the geographic mode of speciation by testing for a lack of postdivergence gene flow and a concurrent termination of gene flow in autosomal and sex-linked markers jointly. We applied this approach to infer the geographic mode of speciation for two allopatric highland rosefinches, the vinaceous rosefinch Carpodacus vinaceus and the Taiwan rosefinch C. formosanus from DNA polymorphisms of both autosomal and Z-linked loci. Our results suggest that the two rosefinch species diverged allopatrically approximately 0.5 Ma. Our approach allowed us further to infer that female effective population sizes are about five times larger than those of males, an estimate potentially useful when comparing the intensity of sexual selection across species.

The de novo assembly of mitochondrial genomes of the extinct passenger pigeon (Ectopistes migratorius) with next generation sequencing.

The information from ancient DNA (aDNA) provides an unparalleled opportunity to infer phylogenetic relationships and population history of extinct species and to investigate genetic evolution directly. However, the degraded and fragmented nature of aDNA has posed technical challenges for studies based on conventional PCR amplification. In this study, we present an approach based on next generation sequencing to efficiently sequence the complete mitochondrial genome (mitogenome) of two extinct passenger pigeons (Ectopistes migratorius) using de novo assembly of massive short (90 bp), paired-end or single-end reads. Although varying levels of human contamination and low levels of postmortem nucleotide lesion were observed, they did not impact sequencing accuracy. Our results demonstrated that the de novo assembly of shotgun sequence reads could be a potent approach to sequence mitogenomes, and offered an efficient way to infer evolutionary history of extinct species.

Characterization of the transcriptome of an ecologically important avian species, the Vinous-throated Parrotbill Paradoxornis webbianus bulomachus (Paradoxornithidae; Aves).

BACKGROUND: Adaptive divergence driven by environmental heterogeneity has long been a fascinating topic in ecology and evolutionary biology. The study of the genetic basis of adaptive divergence has, however, been greatly hampered by a lack of genomic information. The recent development of transcriptome sequencing provides an unprecedented opportunity to generate large amounts of genomic data for detailed investigations of the genetics of adaptive divergence in non-model organisms. Herein, we used the Illumina sequencing platform to sequence the transcriptome of brain and liver tissues from a single individual of the Vinous-throated Parrotbill, Paradoxornis webbianus bulomachus, an ecologically important avian species in Taiwan with a wide elevational range of sea level to 3100 m. RESULTS: Our 10.1 Gbp of sequences were first assembled based on Zebra Finch (Taeniopygia guttata) and chicken (Gallus gallus) RNA references. The remaining reads were then de novo assembled. After filtering out contigs with low coverage (<10X), we retained 67,791 of 487,336 contigs, which covered approximately 5.3% of the P. w. bulomachus genome. Of 7,779 contigs retained for a top-hit species distribution analysis, the majority (about 86%) were matched to known Zebra Finch and chicken transcripts. We also annotated 6,365 contigs to gene ontology (GO) terms: in total, 122 GO-slim terms were assigned, including biological process (41%), molecular function (32%), and cellular component (27%). Many potential genetic markers for future adaptive genomic studies were also identified: 8,589 single nucleotide polymorphisms, 1,344 simple sequence repeats and 109 candidate genes that might be involved in elevational or climate adaptation. CONCLUSIONS: Our study shows that transcriptome data can serve as a rich genetic resource, even for a single run of short-read sequencing from a single individual of a non-model species. This is the first study providing transcriptomic information for species in the avian superfamily Sylvioidea, which comprises more than 1,000 species. Our data can be used to study adaptive divergence in heterogeneous environments and investigate other important ecological and evolutionary questions in parrotbills from different populations and even in other species in the Sylvioidea.

Evolution and dispersal of three closely related macaque species, Macaca mulatta, M. cyclopis, and M. fuscata, in the eastern Asia.

Macaca mulatta, M. cyclopis and M. fuscata are three closely related species in the fascicularis species group. M. mulatta is wide-spread in Asia, while M. cyclopis and M. fuscata are restricted to Taiwan and Japan, respectively. Both M. cyclopis and M. fuscata are thought to be derived from ancient 'mulatta' populations in the eastern Asia. In this study, we analyzed sequences of mitochondrial DNA control region to provide genetic evidence for the evolution and dispersal scenario of the three species proposed by Fooden and Albrecht [Fooden, J., Albrecht, G.H. 1999. Tail-length evolution in fascicularis-group macaques (Cercopithecidae: Macaca). Int. J. Primatol. 20, 431-440]. Our results indicated that several localities in the southern China and Vietnam harbored multiple divergent mtDNA lineages that may not have evolved sympatrically. These divergent mtDNA lineages may have originated from different ancient northern populations that retreated into southern localities during glacial periods. However, the age of the southward retreat and the northward recolonization may be dated back to a more ancient past during late middle Pleistocene (0.12-0.18 mya) instead of during the LGM (0.018 mya). Times of gene divergence between M. mulatta and the two island species, estimated by mean nucleotide difference, suggest the ancestral populations colonized Taiwan and Japan around 0.38-0.44 mya. In addition, a more recent age of mulatta-cyclopis-fuscata population divergence (when ancient populations were isolated), estimated to be 0.17 mya by net nucleotide divergence, is suggested.