Angela

McDonnell

Research

Pages

Bucknell University

Department of Biology

1 Dent Drive

Lewisburg, PA 17837

 

 

ajm050@bucknell.edu

fig

About my research

I have specialized on studying milkweed vines that are found exclusively in the New World (subtribe Gonolobinae, ~500 species). Gonolobinae has a likely origin in the wetter areas of the Neotropics but have radiated throughout temperate North America. I'm especially interested in species that occur in seasonally dry regions because most of the more arid habitats (savannas, grasslands) are often characterized by having low plant biomass due to limited resources, especially precipitation. Despite this, these regions can house amazing levels of plant diversity. While some plant lineages have been well studied in such habitats (e.g., cacti) we know relatively little about patterns of diversification in most plant groups present in drier habitats. My dissertation included systematic study of some pretty fascinating milkweeds and will make an important contribution to our knowledge of plant evolution and diversification in grasslands, savannas, and scrublands of the American subtropic and temperate regions.

 

Gonoloboid milkweeds are arguably the most common milkweeds in American subtropics, but they are little known due to an abundance of uncommon taxa and their confused classification, particularly with respect to the large "trashcan genus" Matelea (~ 300 species). Using molecular resources and methods developed in the related milkweed genus, Asclepias, I'm continuing to study evolution and systmatics in this diverse milkweed group. The most significant revision of North American Gonolobinae species reduced the number of genera to three and expanded Matelea by merging it with 20+ other genera. In doing so, the rank of taxonomic problems was shifted and poorly distinguished subgenera were created. Chloroplast data (Krings, et al. 2008; McDonnell, et al. 2018) have shown Matelea sensu Woodson

to be paraphyletic.

 

Subgenus Chthamalia (I say it as though the Ch were silent) includes many unusual non-twining species that are

heterogeneous in corolla size and shape and exhibits putative adaptations to aridity (loss of twining habit, tubular flowers,

and extreme hairiness). This lineage is a candidate for segregation from Matelea as a distinct genus and a group I focused on

during my dissertation research. I conducted phylogenetic analyses of 3 single copy nuclear (COSII) and 4 chloroplast loci

sampled across major clades of Gonolobinae as well as phylogenomic analyses using 768 single copy nuclear loci and complete

plastomes for sugenus Chthamalia. The resulting phylogenetic hypotheses have served as framewokrs for downstream analyses

to test hypotheses about adaptive ecological shifts in growth form and floral morphology as well as biogeography.

 

 

 

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Figures modified from McDonnell, A., Parks, M., & Fishbein, M. (2018). Multilocus Phylogenetics of New World Milkweed Vines (Apocynaceae, Asclepiadoideae, Gonolobinae). Systematic Botany, 43(1), 77-96.