Stress Tolerance and Ecophysiological Ability of an Invader and a Native Species in a Seasonally Dry Tropical Forest

<div><p>Ecophysiological traits of <i>Prosopis juliflora</i> (Sw.) DC. and a phylogenetically and ecologically similar native species, <i>Anadenanthera colubrina</i> (Vell.) Brenan, were studied to understand the invasive species’ success in caatinga, a seasonally dry tropical forest ecosystem of the Brazilian Northeast. To determine if the invader exhibited a superior resource-capture or a resource-conservative strategy, we measured biophysical and biochemical parameters in both species during dry and wet months over the course of two years. The results show that <i>P. juliflora</i> benefits from a flexible strategy in which it frequently outperforms the native species in resource capture traits under favorable conditions (e.g., photosynthesis), while also showing better stress tolerance (e.g., antioxidant activity) and water-use efficiency in unfavorable conditions. In addition, across both seasons the invasive has the advantage over the native with higher chlorophyll/carotenoids and chlorophyll a/b ratios, percent N, and leaf protein. We conclude that <i>Prosopis juliflora</i> utilizes light, water and nutrients more efficiently than <i>Anadenanthera colubrina</i>, and suffers lower intensity oxidative stress in environments with reduced water availability and high light radiation.</p></div

Nutrient content in leaves of native (<i>Anadenanthera colubrina</i>) and invasive (<i>Prosopis juliflora</i>) species in a tropical dry forest in Brazil across seasons.

<p><i>Different letters on the same line denote statistical differences by Newman-Keul test with significance level of 5 percent between variables.</i></p><p>Values represent the average of replicates (n = 5±SE).</p

Leaf biochemistry in native (<i>Anadenanthera colubrina)</i> and invasive (<i>Prosopis juliflora</i>) species in a tropical dry forest in Brazil across seasons: (A) soluble carbohydrates (SC); (B) total proteins (TP), (C) amino acids (AA); (D) starch.

<p>Values represent the average of replicates (n = 20±SE; invasive dry season n = 25±SE). Different letters denote statistical differences by Newman-Keul test with significance level of 5 percent between variables.</p

Changes in gas exchange in native (<i>Anadenanthera colubrina)</i> and invasive (<i>Prosopis juliflora</i>) species in a tropical dry forest in Brazil across seasons: (A) stomatal conductance (g_s), (B) water potential (Ψ_l), (C) CO₂ assimilation (<i>A</i>), (D) water use efficiency (WUE = <i>A</i>/<i>E</i>), (E) transpiration (<i>E</i>).

<p>Values represent the average of replicates (n = 20±SE; invasive dry season n = 25±SE). Different letters denote statistical differences by Newman-Keul test with significance level of 5 percent between variables.</p

Concentration of leaf pigments in native (<i>Anadenanthera colubrina)</i> and invasive (<i>Prosopis juliflora</i>) species in a tropical dry forest in Brazil across seasons: (A) chlorophyll <i>a</i> (Chl <i>a</i>); (B) chlorophyll <i>a</i>/<i>b</i> (Chl <i>a</i>/<i>b</i>); (C) chlorophyll <i>b</i> (Chl <i>b</i>); (D) chlorophyll/carotenoids (Chl/Car); (E) carotenoids (Car).

<p>Values represent the average of replicates (n = 20±SE; invasive dry season n = 25±SE). Different letters denote statistical differences by Newman-Keul test with significance level of 5 percent between variables.</p

Evidence of stress in native (<i>Anadenanthera colubrina)</i> and invasive (<i>Prosopis juliflora</i>) species in a tropical dry forest in Brazil across seasons: (A) Malondialdehyde (MDA); (B) hydrogen peroxide (H₂O₂), (C) proline.

<p>Values represent the average of replicates (n = 20±SE; invasive dry season n = 25±SE). Different letters denote statistical differences by Newman-Keul test with significance level of 5 percent between variables.</p

Environmental variables in Serra Talhada (Pernambuco, Brazil) over two years of measurements: (A) monthly total precipitation, (B) photosynthetic photon flux density (PPFD), (C) vapor pressure deficit (VPD).

<p>Historical precipitation data represent the years 1999–2011 (source: Agritempo, <a href="http://www.agritempo.gov.br" target="_blank">http://www.agritempo.gov.br</a>).</p