The effect of sampling height on dendroclimatic analysis

The radial growth response to climate of white spruce in open grown conditions was examined at two measurement heights [breast height (1.3 m aboveground) versus stump height (0.3 m aboveground)] in order to examine the role of sampling height in dendroclimatic analysis. Twenty-four white spruce [Picea glauca (Moench) Voss] islands were sampled within Epinette prairie in the Spruce Woods Provincial Park (SWPP) located in south-western Manitoba. The structure of breast height and stump height residual chronologies were essentially the same after standardization and autoregressive (AR) modeling to stabilize growth variability, and AR modeling to remove temporal autocorrelation and thereby reduce low-frequency variation and enhance high-frequency variation. Correlation and response function analysis indicated that white spruce at the two sampling heights responded similarly to total precipitation, moisture index (precipitation subtract potential evapotranspiration), and minimum, mean, and maximum temperature. Both sampling heights also responded strongly to the cumulative effects of precipitation during the period of August of the previous year (t−1) to July of the current year (t). Regardless of the sampling heights considered, the results indicate that white spruce at its southern distribution limit responded strongly to moisture stress intensified by high temperatures. The results support the recommendation, at least for samples of white spruce at its southern distribution limit, that samples taken at stump height can be safely incorporated into tree-ring chronologies without the risk of diminishing the strength of chronologies in detecting climatic signals.     

Drosophila chibby is required for basal body formation and ciliogenesis but not for Wg signaling

Centriole-to-basal body conversion, a complex process essential for ciliogenesis, involves the progressive addition of specific proteins to centrioles. CHIBBY (CBY) is a coiled-coil domain protein first described as interacting with β-catenin and involved in Wg-Int (WNT) signaling. We found that, in Drosophila melanogaster, CBY was exclusively expressed in cells that require functional basal bodies, i.e., sensory neurons and male germ cells. CBY was associated with the basal body transition zone (TZ) in these two cell types. Inactivation of cby led to defects in sensory transduction and in spermatogenesis. Loss of CBY resulted in altered ciliary trafficking into neuronal cilia, irregular deposition of proteins on spermatocyte basal bodies, and, consequently, distorted axonemal assembly. Importantly, cby(1/1) flies did not show Wingless signaling defects. Hence, CBY is essential for normal basal body structure and function in Drosophila, potentially through effects on the TZ. The function of CBY in WNT signaling in vertebrates has either been acquired during vertebrate evolution or lost in Drosophila.