Physiological and morphological growth and hydraulic measures in Asclepias syriaca and A. speciosa under drought

Understanding factors that determine a species’ geographical range is crucial for predicting climate-induced range shifts. Two milkweed species, Asclepias syriaca and Asclepias speciosa, have overlapping ranges along a moisture gradient in North America and are primary food sources for endangered monarch caterpillars. With decreasing moisture, long-lived species often exhibit slower growth and greater drought tolerance while many annual species exhibit faster growth strategies. Using this fast-slow framework, we assessed whether traits of these two sister species differ along a fast-slow growth continuum and could explain their distributions. We measured leaf and root functional traits in common gardens and greenhouse experiments. In key measures indicative of drought tolerance (e.g., growth, transpiration, and water potentials) the species were nearly identical. Contrary to expectations, A. speciosa did not exhibit greater drought tolerance, raising the question of how it survives in t..., The data sets are a combination of greenhouse experiments and field studies.  , , # Asclepias syriaca and speciosa drought tolerance

[https://doi.org/10.5061/dryad.0cfxpnwbx](https://doi.org/10.5061/dryad.0cfxpnwbx)

## Description of the data and file structure

### Files and variables

#### File: 2019\_Milkweed\_Leaf\_width\_data.xlsx

**Description:** Contains plant height and leaf width information for genotypes of *A. speciosa* and *A. syriaca* collected from South Dakota and Minnesota.  Latitude and longitude of collection sites are given.  Leaf width was measured on different leaves for each plant 3x and averaged.  Cells with N/A for plant height or leaf width measures indicate a plant that did not germinate or plants that only had one or two leaves for measurement. 

##### Variables:

* Plant height (cm)
* Leaf width 1 (mm)
* Leaf width 2 (mm)
* Leaf width 3 (mm)
* Leaf width Average (mm)

#### File: Milkweed\_LiCor\_Data.xlsx

**Description:** Gas exchange data using a LiCor 6400 system are given for genotypes of *A. speciosa* and *A. syriaca* measured in ...