Regional distributions of plant sexual systems in temperate forests and the differential effects of climate change

Abstract. Variation in plant sexual systems is an important component of biodiversity. However, how the plants of different sexual systems are distributed in landscapes and how habitat conditions, particularly climates, affect the distribution is not well understood. In this study, we investigated the biogeographic distribution of species richness, biomass and productivity of three sexual systems (monoecy, dioecy and hermaphroditism) for 69 tree species in 20 families in the temperate forest of Northeast China and quantified the relative contributions of different environmental factors to these patterns. We also projected the effect of climate change on the distribution of the three sexual systems in 2100. The results showed that the majority of monoecies were originated from temperate zones and had the highest biomass, productivity and distribution in the region. This dominance of monoecies was due to that they were temperate-originated and niche-conserved. The species richness and productivity of hermaphrodites had a similar set of influencing factors as the other two sexual systems. The proportions of species richness, biomass and productivity of monoecious species were predicted to decrease by up to 43.4 %, 29.0 %, 25.4 %, respectively, under future climate change, while the proportions of the other two sexual systems increased. Our study supports the biogeographical conservatism hypothesis under the scenario of no change of climate but predicted that temperate-originated monoecies would yield to other sexual systems under future climate change scenarios. This study contributes to understanding the regional distribution of different sexual systems in temperate forests and shows the necessity of considering geographical origins of plant sexual systems in assessing impacts of climate change on the diversity of forest flora.