Tuesday, August 4, 2009
Exhibit Hall NE & SE, Albuquerque Convention Center
Background/Question/Methods
When considering the impact of biological invasion on amphibian species, researchers have traditionally focused upon competition for resources, novel predators, and disease. Very little is known about the impact of plant community composition on amphibian fitness, and even less is known about the consequences of plant species introduction. In wetland systems, where over ninety percent of the energy and materials that support aquatic food webs are derived from plant detritus, larval amphibians are captives of their surroundings— yet few studies have considered the impact of plant detrital traits such as N, P- stoichiometry, lignin, and secondary compounds on larval amphibian growth and survival. In order to better understand this interaction, we are exploring the ecological consequences of intraspecific variation in plant detrital traits on Ambystoma maculatum (spotted salamander) and Rana sylvatica (wood frog) growth and survival.
Results/Conclusions
In this study we move beyond simply focusing on the dichotomy between native and nonnative status to mechanistically linking variation in native and nonnative plant traits to amphibian performance. In a preliminary outdoor mesocosm experiment, we reared A. maculatum and R. sylvatica in native and non-native Phragmites australis (common reed) detritus. We observed a significant difference in percent R. sylvatica metamorphosed between native and non-native P. australis treatments (20% versus 70% respectively), as well as mean percent survival of A. maculatum (50% versus 85% respectively). P. australis detritus exhibits surprisingly broad intraspecific variation in aspects such as C:N:P ratio, lignin levels, and specific secondary compounds. We hypothesize that variation in these aspects explains differential amphibian survival. In order to capture the full range of variation in leaf traits within native and non-native P. australis, in fall 2008 we collected leaf detritus from 20 native and 20 non-native populations from across the North American range. We found strongly significant differences in mean N and P levels between the native and non-native subtypes, with higher mean N (p = <0.0001) and mean P (p = 0.0007) in the non-native subtype. Significant differences also exist in N,P, lignin, and specific secondary compounds between populations within a subtype. In spring of 2009, we will rear A. maculatum and R. sylvatica larvae in outdoor mesocosms containing litter from each population. Based on initial results, we predict that intra-subspecific variation in both C:N:P ratio and levels of water-soluble secondary compounds will explain differential amphibian fitness between treatments.
When considering the impact of biological invasion on amphibian species, researchers have traditionally focused upon competition for resources, novel predators, and disease. Very little is known about the impact of plant community composition on amphibian fitness, and even less is known about the consequences of plant species introduction. In wetland systems, where over ninety percent of the energy and materials that support aquatic food webs are derived from plant detritus, larval amphibians are captives of their surroundings— yet few studies have considered the impact of plant detrital traits such as N, P- stoichiometry, lignin, and secondary compounds on larval amphibian growth and survival. In order to better understand this interaction, we are exploring the ecological consequences of intraspecific variation in plant detrital traits on Ambystoma maculatum (spotted salamander) and Rana sylvatica (wood frog) growth and survival.
Results/Conclusions
In this study we move beyond simply focusing on the dichotomy between native and nonnative status to mechanistically linking variation in native and nonnative plant traits to amphibian performance. In a preliminary outdoor mesocosm experiment, we reared A. maculatum and R. sylvatica in native and non-native Phragmites australis (common reed) detritus. We observed a significant difference in percent R. sylvatica metamorphosed between native and non-native P. australis treatments (20% versus 70% respectively), as well as mean percent survival of A. maculatum (50% versus 85% respectively). P. australis detritus exhibits surprisingly broad intraspecific variation in aspects such as C:N:P ratio, lignin levels, and specific secondary compounds. We hypothesize that variation in these aspects explains differential amphibian survival. In order to capture the full range of variation in leaf traits within native and non-native P. australis, in fall 2008 we collected leaf detritus from 20 native and 20 non-native populations from across the North American range. We found strongly significant differences in mean N and P levels between the native and non-native subtypes, with higher mean N (p = <0.0001) and mean P (p = 0.0007) in the non-native subtype. Significant differences also exist in N,P, lignin, and specific secondary compounds between populations within a subtype. In spring of 2009, we will rear A. maculatum and R. sylvatica larvae in outdoor mesocosms containing litter from each population. Based on initial results, we predict that intra-subspecific variation in both C:N:P ratio and levels of water-soluble secondary compounds will explain differential amphibian fitness between treatments.
