Pollen biology and landscape ecology of Juniperus: An integrative study using quantitave molecular approaches, ultrastructure and habitat modeling

Juniperus (Cupressaceae) is regarded as a major source of airborne allergens due to its wide distribution and heavy pollen production. Juniperus species have invaded millions of acres of rangelands, abandoned farms, fields and grasslands. Under favorable conditions, a considerable amount of the Juniperus pollen can be transported and deposited far from its place of origin. Monitoring pollen is based on conventional air sampling and microscopic counting techniques that are labor-intensive and may be limited to identification at the genus or family level.;Juniperus ashei, J. pinchotii and J. virginiana were chosen as our target organisms as they are abundant in Southern United States. Transmission electron microscopy, PCR and sequencing studies were used to confirm the presence of plastids in pollen grains and, thus, to develop plastid primers for the amplification of DNA from Juniperus pollen. These species-specific plastid primers were utilized to verify the long-distance transport of J. ashei. Our studies also aimed at using an alternative method known as quantitative polymerase chain reaction (qPCR) technique in place of microscopy to differentiate between three species of Juniperus in their overlapping pollination seasons. The general absence of genomic data available for these pollen types, however, has resulted in the dependence on transcriptome-mining in search of single-copy nuclear markers. The nuclear markers and the plastid markers were utilized in qPCR experiments to evaluate the pollen concentration in air samples and to test hypotheses regarding overlapping pollination seasons in Juniperus. The qPCR approach was also used to analyze archived air-samples. To determine suitable habitats in the future (2070), species distribution modelling was used to predict the range shift, areas susceptible to encroachment through 2070 for J. monosperma along with the other three Juniperus species.;The results from TEM studies confirmed the presence of plastids in Juniperus pollen. Plastid genes rbcL and matK were successfully amplified from J. ashei, J. pinchotii and J. virginiana pollen DNA. The PCR results with species-specific J. ashei primers provided absolute evidence of long-distance transport of mountain cedar pollen to London, Ontario, Canada, approximately 2400 km from the source. The transcriptome-mining studies yielded two single-copy nuclear markers that were used in the molecular identification and quantification of J. pinchotii and J. virginiana pollen grains. Pollen concentrations from the qPCR data were significantly correlated with light microscopy data. Evidence of overlapping pollination seasons was detected in both current and archived air samples. Species distribution modeling studies indicated that the centroid of the habitats are shifting northward for all four Juniperus species.