Environmental heterogeneity is likely a significant factor in maintaining morphologic variation within and among plant populations. However, the specific environmental factors affecting the evolution of morphologic traits are often difficult to establish. Herein, we examine the role of environmental factors in influencing the distribution of trichome-producing and glabrous populations of Arabidopsis kamchatica. A. kamchatica is an allotetraploid, self-compatible perennial herb typically found growing in fairly well-drained soils in eastern Asia and western North America. Using herbarium records of A. kamchatica from eastern Asia, Alaska, and western Canada, we employed ecological niche modeling to examine the role of elevation and climatic variables in the differentiation of trichome-producing and glabrous populations. Specifically we addressed the following questions: (1) Are the distributions of trichome-producing and glabrous populations different? (2) What environmental factors drive differentiation among trichome-producing vs. glabrous populations? (3) How do observed differences in ecological niches relate to potential functionality of trichomes?
Results/Conclusions
Trichome-producing and glabrous A. kamchatica populations are distributed differently, corresponding to different ecological niches. Occurrence of trichome-producing populations is controlled primarily by (1) elevation, (2) isothermality, (3) mean diurnal temperature range, (4) temperature seasonality, and (5) annual temperature range (in order of decreasing significance); occurrence of glabrous populations is controlled primarily by (1) total precipitation of the coldest quarter, (2) minimum temperature of the coldest month, (3) annual mean temperature, (4) total precipitation of the wettest quarter, and (5) elevation. 55.1% of variation in trichome-producing population distribution is related to temperature effects, whereas only 9.8% is related to precipitation effects (35.1% is related to elevation and coupled temperature-precipitation effects). 46.4% of variation in the glabrous population distribution is related to temperature effects and 22.6% is related to precipitation effects (31.0% is related to elevation and coupled temperature-precipitation effects). The lower contribution of precipitation effects and overall drier climate of the ecological niche associated with trichome-producing plants suggest that trichome production in A. kamchatica may serve as an adaptation to low water availability. The lower contribution of temperature effects for glabrous plants is consistent with previous results finding the morphology associated with a wider temperature range than the trichome-producing plants.