Ecophysiological traits of terrestrial and aquatic carnivorous plants: are the costs and benefits the same?

Abstract

Identification of tradeoffs among physiological and morphological traits and their use in cost–benefit models and ecological or evolutionary optimization arguments have been hallmarks of ecological analysis for at least 50 years. Carnivorous plants are model systems for studying a wide range of ecophysiological and ecological processes and the application of a cost–benefit model for the evolution of carnivory by plants has provided many novel insights into trait‐based cost–benefit models. Central to the cost–benefit model for the evolution of botanical carnivory is the relationship between nutrients and photosynthesis; of primary interest is how carnivorous plants efficiently obtain scarce nutrients that are supplied primarily in organic form as prey, digest and mineralize them so that they can be readily used, and allocate them to immediate versus future needs. Most carnivorous plants are terrestrial – they are rooted in sandy or peaty wetland soils – and most studies of cost–benefit tradeoffs in carnivorous plants are based on terrestrial carnivorous plants. However approximately 10% of carnivorous plants are unrooted aquatic plants. Here we ask whether the cost–benefit model applies equally well to aquatic carnivorous plants and what general insights into tradeoff models are gained by this comparison. Nutrient limitation is more pronounced in terrestrial carnivorous plants, which also have much lower growth rates and much higher ratios of dark respiration to photosynthetic rates than aquatic carnivorous plants. Phylogenetic constraints on ecophysiological tradeoffs among carnivorous plants remain unexplored. Despite differences in detail, the general cost–benefit framework continues to be of great utility in understanding the evolutionary ecology of carnivorous plants. We provide a research agenda that if implemented would further our understanding of ecophysiological tradeoffs in carnivorous plants and also would provide broader insights into similarities and differences between aquatic and terrestrial plants of all types.

Surf and Turf: Toward better synthesis by cross‐system understanding

“…‘Surf and Turf’ approaches can also identify important similarities where ecological theory can transcend system. Ellison and Adamec (2011) examined a cost‐benefit model for the evolution of carnivory, comparing the ecophysiological traits of terrestrial and aquatic carnivorous plants. The relationship between scarce nutrients and abundant photosynthesis may be central to the evolution of carnivory in plants; as marine ecologists, we also immediately recognized the similarity to heterotrophic marine invertebrates that also harbor photosynthetic symbionts in oligotrophic seawater.…”

The fitness of the environments of air and water for photosynthesis, growth, reproduction and dispersal of photoautotrophs: An evolutionary and biogeochemical perspective

“…Some unrooted freshwater macrophytes, such as species within the genera Utricularia (Lentibulariaceae) and Aldrovanda vesiculosa (Droseraceae), supplement their mineral requirements by trapping small animals within bladders on the shoots (Adamec, 1997). Aquatic plants represent about 10% of all known carnivorous plants (Ellison and Adamec, 2011). Consortia within the bladders may provide as much advantage to the plant by nutrient recycling as by the trapping of animals (Richards, 2001).…”

Darwin-Inspired Learning

“…In part, this reflects the fact that strong selection in nutrient-poor environments has led repeatedly to the evolution of carnivory in a wide range of plant lineages (Albert, Williams & Chase, 1992;Adamec, 1997). Ellison & Farnsworth, 2005;Ellison & Adamec, 2011). But perhaps more importantly (in the context of this chapter), it was impossible for Darwin in the nineteenth century, just as it is for us today, to use controlled experiments to distinguish among hypotheses for the origin of different species, genera and higher taxa.…”