Segregation of Tilia cordata and T. platyphyllos (Malvaceae) along environmental gradients

Abstract

Closely related congeneric species living in sympatry raises the question of how they are separated along abiotic and biotic axes. Within northern Europe, Tilia cordata and Tilia platyphyllos are two such species. They are large, long-lived trees, often dominant members of their community, and frequently grow sympatrically. This study measured a series of edaphic and topographic variables across a number of sites and examined these via univariate and multivariate approaches to understand how the two species differed. This showed that T. cordata occupies soil with significantly greater organic carbon content and is present in areas with greater potential incident solar radiation. There was no significant difference between the two species across soil depths, acidity, moisture content or elevation above sea level. T. cordata is the more variable of the two species with regard to soil pH and soil moisture content. This is the first comprehensive account of these characters for the two species. The quantitative values obtained in this study are broadly commensurate with descriptive accounts from the literature. However, contrary to previous descriptions, no difference was observed in pH between the two species and soil nutrient levels were the inverse of those expected. This study presents potentially fruitful areas for examining potential niche separation between the two species alongside potential differences in litter leaf chemistry.

Keywords:

• abiotic
• congeneric
• edaphic
• niche separation

Acknowledgements

Funding for the work undertaken was provided by both the award of a Plant Study Grant by the Botanical Society of Britain and Ireland to the lead author, as well as internal grants from Edge Hill University. The authors wish to thank Clare Bugg, Colin Davies, Emily Simmons and Jon Tomkinson for their assistance in the field and with data collection, as well as the anonymous reviewers whose comments and feedback have been used to improve this manuscript.