Chinese Hwamei Research Articles

Update: Escaping the trap of low sample size in island biogeography

ISSN 1948‐6596 Hickerson, M. & Meyer, C. (2008) Testing comparative phylogeographic models of marine vicariance and dispersal using a hierarchical Bayesian ap‐ proach. BMC Evolutionary Biology, 8, 322. Kallimanis, A.S., Bergmeier, E., Panitsa, M., Georghiou, K., Delipetrou, P. & Dimopoulos, P. (2010) Bio‐ geographical determinants for total and en‐ demic species richness in a continental archipel‐ ago. Biodiversity and Conservation, 19, 1225‐ Lambeck, K., Esat, T.M. & Potter, E.‐K. (2002) Links be‐ tween climate and sea levels for the past three million years. Nature, 419, 199‐206. Li, J.‐W., Yeung, C.K.L., Tsai, P.‐W., et al. (2010a) Reject‐ ing strictly allopatric speciation on a continental island: prolonged postdivergence gene flow be‐ tween Taiwan (Leucodioptron taewanus, Passeriformes Timaliidae) and Chinese (L. canorum canorum) hwameis. Molecular Ecology, Li, S.‐H., Yeung, C.K.L., Han, L., Manh Hung, L., Wang, C. ‐X., Ding, P. & Yao, C.‐T. (2010b) Genetic intro‐ gression between an introduced babbler, the Chinese hwamei Leucodioptron c. canorum, and the endemic Taiwan hwamei L. taewanus: a multiple marker systems analysis. Journal of Avian Biology, 41, 64‐73. news and update Losos, J.B. & Ricklefs, R.E. (2009) Adaptation and diver‐ sification on islands. Nature, 457, 830‐836. MacArthur, R.H. & Wilson, E.O. (1967) The theory of island biogeography. Princeton University Press, Princeton, New Jersey. Mayr, E. (1942) Systematics and the origin of species, from the viewpoint of a zoologist. Columbia University Press, New York. McDowall, R.M. (2002) Accumulating evidence for a dispersal biogeography of southern cool tem‐ perate freshwater fishes. Journal of Biogeogra‐ phy, 29, 207‐219. Raymo, M.E., Mitrovica, J.X., O'Leary, M.J., DeConto, R.M. & Hearty, P.J. (2011) Departures from eustasy in Pliocene sea‐level records. Nature Geoscience, 4, 328‐332. Whittaker, R.J. & Fernandez‐Palacios, J.M. (2007) Island biogeography. Ecology, evolution and conserva‐ tion. Oxford University Press, Oxford. Edited by Spyros Sfenthourakis update Escaping the trap of low sample size in island biogeography Ecologists and evolutionary biologists have been fascinated by island biodiversity at least since the first travels of 18 th century naturalists. Islands’ sometimes exuberant diversity – full of rare forms and endemic species or varieties – their character of discrete entities and their isolation from the mainland make islands exceptional natural labora‐ tories for the development of ecological and evo‐ lutionary theory. Perhaps unsurprisingly, they have been home to many major theoretical ad‐ vances in these disciplines during the last 50 years (see Whittaker & Fernandez‐Palacios 2007), from which the seminal Equilibrium Theory of Island Biogeography (ETIB, MacArthur and Wilson 1967) is just the most outstanding example. In spite of the importance of islands and archipelagos for the development of bio‐ geographical theory, the stubborn persistence of archipelagos and island groups to come in low island numbers and the tendency of different characteristics to be collinear makes it difficult to evaluate hypotheses and extract conclusions about the processes originating from the diversity and structure of their assemblages. For example, finding a significant relationship (at the 0.05 level) between any two island descriptors for the seven main islands of the Canarian archipelago using simple least‐squares regression models requires percentages of explained variation (adjusted r 2 ) of about 50%. This problem is further aggravated when working with patterns of within‐island diver‐ sification, because many islands may be too small to host speciation processes (see e.g. Losos & Schluter 2000), therefore reducing the number of islands that can be used for these particular analy‐ ses in each archipelago. Needless to say, discrimi‐ nating between three or four non‐mutually exclu‐ sive hypotheses represented by predictors with different degrees of collinearity is typically a diffi‐ cult task in island biogeography. frontiers of biogeography 3.4, 2012 — © 2012 the authors; journal compilation © 2012 The International Biogeography Society

Movement distances enhance validity of predictive models

Including the distance species are able to move in predictive models improves conservation practice. Bird inventory projects carried out from 1993 to 2004 in Taiwan provide an opportunity to investigate the relationships among species distribution, movement distance, and the environment. We compared projected distributions of 17 Taiwanese endemic bird species using what we called the Standard Method ( i.e. movement distance is zero) and what we called the Buffer Method ( i.e. movement distance is longer than zero) in three presence-only models (GARP, MAXENT and LIVES). The Standard Method used species original occurrence records directly while the Buffer Method expanded the occurrence of species to areas 1 km 2 around each recorded location. We first tested the efficacy of the Buffer Method using ten common species of the 17, and then applied the method to two rare species of the 17. For both the common and rare species, the distributions predicted by the two methods showed slight but important differences. The Buffer Method for all species had a higher average predictive probability, while the Standard Method had a higher maximum predictive probability. Most of the values for the area under the curve (AUC) were over 0.8 with the exceptions of Taiwan Barbet ( Megalaima nuchalis) and Taiwan Hwamei ( Garrulax taewanus), which have recently separated from Indochinese Barbet ( Megalaima annamensis) and Chinese Hwamei ( Garrulax canorus), and since 2008 and 2006 have been regarded as species endemic to the study area. Kappa values showed good performance for all species using both methods. The Buffer Method, however, resulted in significantly higher sensitivity and accuracy values for all models of species ( p < 0.05). We conclude that when modeling species distribution including the area where the species was censused along with areas within the minimum movement areas better defines the surrounding areas that might supplement core habitat requirements. Therefore, using the Buffer Method, species surrounding distribution can be obtained which provides a better understanding of the species distributions. Given that distribution size is a key to the conservation of species, we suggest the Buffer Method can be used in conservation planning.

Rejecting strictly allopatric speciation on a continental island: prolonged postdivergence gene flow between Taiwan (Leucodioptron taewanus, Passeriformes Timaliidae) and Chinese (L. canorum canorum) hwameis

Allopatry is conventionally considered the geographical mode of speciation for continental island organisms. However, strictly allopatric speciation models that assume the lack of postdivergence gene flow seem oversimplified given the recurrence of land bridges during glacial periods since the late Pliocene. Here, to evaluate whether a continental island endemic, the Taiwan hwamei (Leucodioptron taewanus, Passeriformes Timaliidae) speciated in strict allopatry, we used weighted-regression-based approximate Bayesian computation (ABC) to analyse the genetic polymorphism of 18 neutral nuclear loci (total length: 8500 bp) in Taiwan hwamei and its continental sister species, the Chinese hwamei (L. canorum canorum). The nonallopatry model was found to fit better with observed genetic polymorphism of the two hwamei species (posterior possibility = 0.82). We also recovered unambiguous signals of nontrivial bidirectional postdivergence gene flow (N(e)m >> 1) between Chinese hwamei and Taiwan hwamei until 0.5 Ma. Divergence time was estimated to be 3.5 to 2 million years earlier than that estimated from mitochondrial cytochrome b sequences. Finally, using the inferred nonallopatry model to simulate genetic variation at 24 nuclear genes examined showed that the adiponectin receptor 1 gene may be under divergent adaptation. Our findings imply that the role of geographical barrier may be less prominent for the speciation of continental island endemics, and suggest a shift in speciation studies from simply correlating geographical barrier and genetic divergence to examining factors that facilitate and maintain divergence, e.g. differential selection and sexual selection, especially in the face of interpopulation gene flow.

Genetic introgression between an introduced babbler, the Chinese hwameiLeucodioptron c. canorum, and the endemic Taiwan hwameiL. taewanus: a multiple marker systems analysis

Identification of interspecific hybrids is often a subject of primary concern in the development of conservation strategies. Here we performed a genetic analysis combining mitochondrial DNA (mtDNA), microsatellites and single nucleotide polymorphic sites (SNPs) to assay the level of hybridization and introgression between an introduced babbler, Chinese hwameiLeucodioptron canorus, and its close relative, the endemic Taiwan hwameiL. taewanusin Taiwan. Fifty‐five Chinese hwameis from the Asian mainland and 69 Taiwan hwameis, including nine morphological hybrids, were sampled and analyzed. Evidences of mitochondrial introgression were found in three hybrids and one Taiwan hwamei. Five unlinked interspecific SNPs were identified at nine anonymous nuclear loci with interspecific differentiation (totalFst=0.77) that was much higher than that at seven highly polymorphic microsatellite loci combined (totalFst=0.1). Bayesian cluster analysis based on five interspecific SNP loci and two highly differentiated microsatellite loci (Fst&gt;0.08) suggested that twelve individuals sampled in Taiwan were likely F2 or backcross hybrids, among which eight were morphological intermediates. A total of 20.3% (14/69) individuals sampled in Taiwan were suggested to be hybrids, suggesting that fitness reduction in hybrids might be negligible. These results imply that without an effective management strategy, the entire Taiwan hwamei population could easily become an admixed with Chinese hwamei and loose its evolutionary integrity. To reduce introgressive hybridization, illegal trade of Chinese hwamei should be strictly regulated and only the expensive male Chinese hwameis should be legally imported to minimize the chance for Chinese hwameis being released into the field. In our study we also found interspecific SNP markers to outperform microsatellite loci in detecting hybridization and introgression between two closely related species, which may be ascribed to the lower level of homoplasy of SNP loci.

Sailing through the Late Pleistocene: unusual historical demography of an East Asian endemic, the Chinese Hwamei (Leucodioptron canorum canorum), during the last glacial period

Pleistocene climate fluctuations shaped the patterns of genetic diversity observed in extant species. In contrast to Europe and North America where the effects of recent glacial cycles on genetic diversity have been well studied, the genetic legacy of the Late Pleistocene for East Asia, a region of great topographical complexity and presumably milder historical climate, remains poorly understood. We analysed 3.86 kb of the mitochondrial genome of 186 Chinese Hwamei birds, Leucodioptron canorum canorum, and found that contrary to the conventional expectation of population decline during cold periods (stadials), the demographic history of this species shows continuous population growth since the penultimate glacial period (about 170,000 years ago). Refugia were identified in the south, coastal regions, and northern inland areas, implying that topographic complexity played a substantial role in providing suitable habitats for the Chinese Hwamei during cold periods. Intermittent gene flow between these refugia during the warmer periods (interstadials) might have resulted in a large effective population of this bird through the last glacial period.