Plants residing at the boundaries of their preferred climatic zones often struggle to thrive when transplanted to different environments, a phenomenon ascribed to extreme conditions and genetic factors. While the detrimental effects of these factors on growth have been acknowledged, the precise mechanisms remain unclear.
A recent study conducted by researchers from the University of Tsukuba delves into this issue, focusing on Betula ermanii, a tree species inhabiting the alpine regions of Japan. Saplings were collected from 11 sites across the country, and site-specific examinations were conducted at eight locations to analyze growth and explore the correlation between climatic conditions and genetic characteristics. The findings have been published in the journal Heredity.
The results unveiled distinct challenges faced by populations at different edges of the distribution range. Saplings from the Central Alps’ tree line exhibited lower survival rates and population sizes, potentially linked to their adaptation to the low-temperature environment and selection for smaller individual sizes. Conversely, saplings from the Kii Peninsula, the southern limit of the distribution, displayed genetic distinctiveness and lower growth rates, accompanied by low genetic diversity, indicative of inbreeding.
The study suggests that saplings from the Central Alps struggle in diverse environments due to their specialized adaptation and smaller size selection. In contrast, the Kii Peninsula population faces challenges rooted in genetic drift and inbreeding, resulting in diminished survival and growth rates. The research emphasizes that plant populations at the distribution edge are vulnerable, with the potential for disappearance as global warming advances.
These findings underscore the urgency of implementing immediate conservation measures to safeguard plant species growing at the edges of their natural distribution ranges in the face of climate change.