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Hydrocotyle bonariensis
Hydrocotyle bonariensis is a C3 photosynthetic perennial eudicot (Joesting 2011). Its

habitat extends along the eastern United States’ Atlantic seaboard from the Virginia coast,
around the Florida peninsula and gulf coast to Chile (Joesting 2011). Hydrocotyle bonariensis
has unique adaptive strategies that facilitate its survival in the harsh dune environment (Wyatt
unpublished). This peculiar, indigenous dune species is burial tolerant, adjusting to variable sand
deposition rates (Joesting 2011).

While a normal model of growth in a low freshwater environment would be smaller,
curled leaves with a thickened cuticle (Smith 2009), H. bonriensis has a broad, flat, almost
circular leaf that does not curl (Hancock 2009). These leaves, that can grow up to 870 mm in
diameter, contain three layers of adaxial palisade mesophyll and one layer of abaxial spongy
mesophyll (Joesting 2011). The leaves are nearly amphistomatous, yet Hydrocotyle bonariensis
displays the lowest stomatal conductance and transpiration comparatively to other floral species
found in the dune community (Hancock 2009). For a species so seemingly maladapted to the
environment, how could it be a minor, yet important part of the dune habitat (Wyatt
unpublished)?

One adaptive feature utilized by Hydrocotyle bonariensis may be leaf inclination
(Joesting 2012). By orienting almost vertically at midday, leaves maximize morning and
evening PAR while avoiding photoinhibition and thermoinhibition (Joesting 2012). Xylem
water potential remains constant across the shoots even when growing in soils that only contain
3.0% water (Hancock 2009). Another adaptive feature may be translocation of water and
nutrients through the shoots (Evans 1988, 1992, 1992b). Hydrocotyle bonariensis spreads out
into the dune microhabitats though rhizomatous shoots called ramets (Evans 1988). The lateral

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