4000 YEARS OF PHENOTYPIC CHANGE IN AN ISLAND BIRD: HETEROGENEITY OF SELECTION OVER THREE MICROEVOLUTIONARY TIMESCALES

摘要: Pronounced phenotypic shifts in island populations are typically attributed to natural selection, but reconstructing heterogeneity long-term selective regimes remains a challenge. We examined scenario of divergence proposed for species colonizing new environment, involving directional selection with rapid shift optimum and subsequent stabilization. provide some the first empirical evidence this model evolution using morphological data from three timescales an bird, Zosterops lateralis chlorocephalus. In less than four millennia since separation its mainland counterpart, substantial increase body size has occurred was probably achieved fewer 500 generations after colonization. Over recent decades, traits have fluctuated showed no significant trends, suggesting maintenance relatively stable phenotype. Finally, estimates contemporary gradients indicated generally weak selection. These results rare description regimes, caution that observations current may be limited value inferring mechanisms past adaptation due lack constancy even over short time-frames.