Poster

         Tropical Biology

Quantifying and Testing for Leaf Venation Patterns Within Araceae.

Presenting Author
Malinda Barberio
Description
Leaf venation patterns have been used as an important resource for reading the leaf fossil record of angiosperms. Leaf trait evolution, climate reconstruction, and community construction have been derived from dicot venation patterns. However, monocots exhibit very different venation patterns and whose diversity is largely understudied, which obscures our understanding of their evolutionary history. Araceae, a very diverse family of monocots in the order Alismatales, diverged in the early Cretaceous. Their diverse leaf shapes, vein architectures, and growth habits may help provide more information on monocot venation that can be used to read the fossil record. Araceae leaves include both reticulate patterns with higher-order venation similar to dicots, as well as monocot typical parallel (costadromous, pinnacostadromous) patterns. Previous research hypothesized that there are significant differences between venation patterns in Araceae at the subfamily level that can be used for leaf material identification, however, no standardized vein classification or statistical models have been applied. This study used cleared leaves to analyze the vein density (vein length per area; VLA) of the total, parallel, cross, and higher-order veins and morphological traits (e.g., leaf perimeter, area, and shape) among Araceae to determine if there are morphological or phylogenetic patterns that can be applied to material identification and explain the evolutionary history of Araceae venation. The species-rich and morphologically diverse genera Anthurium (with dicot-like reticulate venation) and Philodendron (with parallel venation) were used to specifically test if there is a relationship between leaf shape and size with venation. Linear regression and MANOVA tests between all vein types determined significant differences between subfamilies, and between Anthurium and Philodendron. Ternary plots demonstrated clear separation of each subfamily based on the parallel, cross, and higher-order VLA. Although vein patterns are significantly different among Anthurium and Philodendron, they are not correlated with leaf shape, size, or perimeter. These patterns are likely a result of transport and mechanical support due to different Anthurium and Philodendron growth habits. The results support previous hypotheses that fossilized and extant Araceae exhibit clear venation patterns among subfamilies and can be used for sample identification.  Further studies can incorporate additional genera to expand on these relationships and consider Araceae diversity, growth habits, and geographic range.