Abstract Detail

Biogeography

Soper Gorden, Nicole L [1], Etterson, Julie [2], Maddaus, Peter [3], McClanahan, Gina [4].

Floral and leaf defenses both vary with latitude.

Leaf defenses have been the focus of ecological, evolutionary, and biogeographical studies for decades. For example, several studies have found higher levels of leaf defenses at low latitudes, perhaps due to a combination of increased resource availability and increased herbivore pressure. However, other forms of defense, such as floral defenses, have only gained interest more recently, despite the fact that floral defenses can be just as common as leaf defenses and frequently occur at much higher levels. While several studies have started to look at the presence of floral defenses, their effects on potential floral antagonists, and their ability to be induced, the field of floral defense ecology is still fairly new. In this study, we investigated patterns in floral defenses across geographical clines and compared them to leaf defenses to test for tradeoffs in various plant defense strategies across latitude. We collected leaves and flowers from Chamaecrista fasciculata plants at nine sites across latitudes from Minnesota to Texas and extracted their condensed tannin defenses. We found that plants had higher levels of condensed tannins in their leaves at lower latitudes, which agrees with previous studies looking at leaf defenses across latitude in other species. Additionally, we found that floral condensed tannins were also higher at low latitudes. This suggests that there may not be a tradeoff between chemical defenses in leaves and flowers across space, and that both may be responding to the same conditions. Frequently, both defenses were also correlated with some measure of plant size, suggesting condensed tannins may be more common in plants with higher resource availability. However, extra floral nectaries (EFNs), which are used to attract ant defenders that protect both flowers and leaves, were larger at higher latitudes, suggesting there may be a tradeoff between chemical defenses and indirect defenses in Chamaecrista fasciculata. This may mean that EFNs are cheaper to maintain in relatively resource poor northern climes, or that plants have responded to local variation in ant presence or other environmental characters when adapting their defense strategies. To our knowledge, this is the first study looking at floral defenses or EFNs across latitudinal clines. Such studies may become increasingly important to understand how plants interact with their antagonists across geographic space as climate change alters plant and animal phenologies and ranges.

1 - Mars Hill University, Natural Sciences, 100 Athletic St, Campus Box 6671, Mars Hill, NC, 28754, USA
2 - University Of Minnesota Duluth, 207 Swenson Science Building, 1035 Kirby Drive, Duluth, MN, 55812, USA
3 - University of Minnesota Duluth, 1035 Kirby Dr, SSB 207, Duluth, Minnesota, 55812, United States
4 - University of Minnesota Duluth, 1035 Kirby Dr., SSB 207, Duluth, Minnesota, 55812, United States

Keywords:
Latitude
Indirect defenses
Chemical defenses
tradeoffs
Chemical Ecology
Longitude.

Presentation Type: Oral Paper
Session: 43, Biogeography III
Location: 205/Savannah International Trade and Convention Center
Date: Wednesday, August 3rd, 2016
Time: 1:30 PM
Number: 43001
Abstract ID:856
Candidate for Awards:None