The Patterns And Driving Factors Of Trichomes In Angiosperms In Hengduan Mountains Region

The evolutionary trends among communities,spatiotemporal patterns of functional traits,and potential links between functional traits and environmental factors have been major directions in the study of functional traits.Past research on functional traits has mainly focused on the species level or community level,and few studies have explored the patterns of functional traits at the large-scale level.However,large-scale studies help to quantitatively elaborate the paradigms of functional trait distribution across populations and the paradigms of correlations between functional traits and environmental factors.In this paper,we compiled trichomes data(presence/absence)for 6,262 angiosperm species from the Hengduan Mountains(a global biodiversity hotspot in southwest China).We tested the elevational gradient(800-5,000 m a.s.l.with each 100 m elevation interval)in the occurrence of plant species with trichomes,and its correlations with biotic(herbivorous insects richness)and abiotic factors(mean annual temperature;plant-available water),potentially shaping the elevational gradient in the occurrence of trichomes.The results showed that:The occurrence pattern of trichomes varies significantly among taxa.Woody species had higher proportion with non-glandular trichomes and lower proportion with glandular trichomes than herbaceous species;Deciduous species had higher proportion with trichomes than evergreen species;Tropical species had highest proportion with non-glandular trichomes and lowest proportion with glandular trichomes.The occurrence pattern of trichomes varies significantly among organs.Trichomes occur centrally in leaves and flowers.The proportion of species with trichomes occurred in flowers,regardless of non-glandular trichomes or glandular trichomes,was higher than the proportion of species with trichomes occurred in other organs.Glandular trichomes occur centrally in a few organs,and non-glandular trichomes occur widely in most organs.There was a clear elevation gradient pattern in trichomes,but the elevational pattern was affected by the type of trichomes.The proportion of species with non-glandular trichomes in herbaceous species decreased with increasing altitude,but the proportion of species with non-glandular trichomes in woody species were not significantly correlated with altitude.The proportion of species with glandular trichomes increased with altitude,and the relationship between the proportion of species with glandular trichomes and altitude was not affected by growthform.The occurrence of trichomes is closely related to environmental factors,and the response of different trichomes to environmental factors were significantly different.The predicted incidence of non-glandular trichomes were positively correlated with herbivorous insect richness and mean annual temperature,and negatively correlated with plant available water;The predicted incidence of glandular trichomes were negatively correlated with herbivorous insect richness and mean annual temperature,and positively correlated with plant available water.After considering phylogenetic relationships,the evolution of trichomes among plant species is not random.There was a strong phylogenetic signal for both glandular trichomes and non-glandular trichomes.After considering phylogenetic relationships,the correlations of trichomes,both glandular trichomes and non-glandular trichomes,and environmental factors did not change.In conclusion,the occurrence patterns of trichomes in different populations and types of plants were different;Environmental factors have significant effects on the occurrence of trichomes.Plants living in low altitude with high temperature,drought,and more herbivorous insects are more likely to develop nonglandular hairs.