Distribution pattern and driving factors of genetic diversity of passerine birds in the Mountains of Southwest China

Genetic diversity is one of the three dimensions of biodiversity and fundamental to various life forms on the Earth.Understanding the distribution pattern of genetic diversity and its driving forces has been an important topic in ecology,biogeography and conservation biology since the last decade.We investigated the genetic diversity pattern of passerine birds in the Mountains of Southwest China,a global biodiversity hotspot with the highest species richness of birds in the entire Eurasia,and explored the influencing forces of environmental variables on genetic diversity.We compiled 1189 Cytochrome b sequences of 27 passerine species from 152 geographic sites,covering the range of Mountains of Southwest China and its adjoining areas.We generated genetic diversity distribution maps using a grid-cell method based on nucleotide diversity and haplotype diversity indices.We further analyzed the variation pattern of the two indices along latitudinal,longitudinal,and elevational gradients.The correlations between the two indices and environmental variables were also evaluated.The nucleotide diversity hotspots were mostly located in the southern Hengduan Mountains,while for haplotype diversity,three hotspots were detected:the southeast edge of the Qinghai-Tibetan Plateau,the southern Hengduan Mountains and the Qinling Mountains.There was no monotonic increasing or decreasing pattern in nucleotide diversity or haplotype diversity along latitudinal,longitudinal or elevational gradients except for altitudinal range.Correlation and model selection analyses detected multiple environmental variables in driving genetic diversity patterns,including temperature,precipitation,vegetation,human influence,longitude and altitude range.Similar to the pattern of species richness,the nucleotide diversity pattern of passerine birds in the Mountains of Southwest China presents a decreasing trend from southwest to northeast,while the haplotype diversity pattern is more likely decreased from west to east.Our results indicate that the distribution pattern of genetic diversity may be derived from the complex topography and diverse microclimates in the Mountains of Southwest China.

Optimal analysis conditions for sperm motility parameters with a CASA system in a passerine bird, Passer montanus

Background:Sperm motility parameters,which can be measured objectively and repeatedly by a computer-assisted sperm analysis(CASA)system,are important indicators of sperm quality.However,the sperm motility parameters assessed by a CASA system can be affected by various factors,including instrument components and settings,sperm preparation or analysis procedures.To date,no standardized protocol is available that would permit to assess sperm kinetic characteristics in passerine birds and this lack precludes any comparison of sperm swimming ability and sperm quality across species.Methods:In this study,we chose the Tree Sparrow(Passer montanus)as the object to evaluate sperm motility parameters,including sperm motility,sperm velocity and sperm movement trajectory,at different analysis time,temperatures and pH using the WLJY-9000 CASA system.Results:Sperm motility parameters remained statistically unchanged at 1‒9 min.Progressive motility was similar at 38℃ and 40℃,but a greater percentage of slow progressive sperm was detected at 38℃ compared to 40℃ and 42℃.Additionally,progressive motility was lower and immotility was higher at 42℃than 38℃and/or 40℃(close to the body temperature of the Tree Sparrow).The percentages of rapid progressive sperm,progressive sperm and immotile sperm were statistically similar at pH 7.0,7.5 and 8.0 with the exception of lower percentage of progressive sperm at pH 7.0 compared to pH 7.5.In addition,slower sperm velocity and worse sperm movement trajectory were found at pH 6.0 and 9.0 than those at pH 8.0,7.5 or 7.0.Conclusions:Our study indicates that the ideal conditions for sperm motility parameters assessment in Tree Sparrow are obtained between 1 and 9 min after dilution,an environment at body temperature(40℃)and a pH around 7.5-8.0.The results of this study provide a reference for the evaluation of sperm characteristics and sperm quality using a CASA system in passerine birds.

Floristic, Structural, and Conservation Analysis of the Habitats Occupied by Dupont’s Lark, Chersophilus duponti, in the Northwest Edge of Its Distributional Range

This paper describes and analyzes floristic, structural and conservation features of the shrubland occupied by Chersophilus duponti in the northwest corner of its world distribution range. This study relates the coverage, floristic composition with estimated lark density in the area. We identified four types of shrublands, three of them varied significantly in floristic composition for the habitats of this species in contrast with those of their world distribution: Cistus ladanifer scrubs;heaths dominated by Ericaceae, and scrubs dominated by the genera Lavandula, Thymus and Cytisus. The fourth type, dominated by aromatic chamaephytes and grass, fits descriptions of the bird’s typical habitat. The areas sampled are subject to different categories of threats, the most significant being the natural succession process due to the cessation of grazing, reforestation measures and the use of flat areas for farmlands or other uses. The density of larks in this area was directly related to coverage-composition of plant community.