Natural experiments indicate that geomagnetic variations cause spatial and temporal variations in coconut palm asymmetry.

摘要

A study conducted by Davis [Math. Model. (1987) 8, 730-733] suggested that the foliar spiral direction (FSD) of coconut palms varies with latitude (R trees predominating in the northern hemisphere and L trees in the southern hemisphere). A reanalysis of Davis's data indicated that these hemispheric asymmetries in FSD are significantly better correlated with magnetic (dip) latitude than with geographic or geomagnetic (centred dipole) latitude, suggesting that latitudinal asymmetries in FSD might be associated with the temporally varying component of the earth's magnetic field. This paper reports that asymmetries in FSD are also evident in populations of coconut palms on opposite sides of islands, and that asymmetries between cohorts vary with an 11-year periodicity, two novel discoveries consistent with the hypothesis that geomagnetic variations underlie asymmetries in coconut palm FSD. To examine whether coconut palm FSD varies around the circumferences of islands, data were collected on two Caribbean islands (Puerto Rico, n=4850; Antigua, n=2038), two Hawaiian islands (Hawaii, n=3552; Maui, n=2175) and two French Polynesian islands (Tahiti, n=1635; Moorea, n=2116). For each population, the degree of asymmetry for trees with easily distinguishable leaf scars was determined by calculating an asymmetry quotient (AQ) based on AQ=(L-R)/Total. Asymmetries in FSD were evident on opposite sides of all five islands studied (since Tahiti and Moorea behaved as a single island). AQs were maximum at the following bearings (from geographic N): -20 degrees in the Caribbean islands; 125 degrees in the Hawaiian islands; and -165 degrees in Tahiti/Moorea. No correspondence was found to exist between the cross-island asymmetries of AQ and the directions of the trade winds. The effects were observed most strongly in natural populations. The highest X2 value (assuming L=R) for any population (n=710; X2=18.95; P<0.001) was from a natural grove in Puerto Rico. Analysis of data published in 1963 by Davis [J. Genet. (1963) 58, 186-215], from a coconut palm population growing in Kerala, India, showed that there was a strong positive correlation between the AQs of the nine cohorts weighted for population size and the total average monthly sunspot numbers 4 years prior to their respective years of planting. It is impossible to prove by natural experiments a role for geomagnetic variations in establishing asymmetries in coconut palm FSD, but by eliminating rival hypotheses, the induced current hypothesis gains in stature..