Fundamental links between genes and elements: evolutionary implications of ecological stoichiometry

Abstract

Organisms require elements to live and reproduce. We already know that availability of certain elements [e.g. phosphorus (P)] is highly variable spatiotemporally. In addition, there is variability in demand for various elements ontogenetically, as well as phylogenetically. Nonetheless, we know little about the underlying causes for such variation. In this study, we surveyed the literature to identify genes involved in the homeostasis of one biogenic element, P. Evidence from the literature suggests that variation in the environmental supply of P affects expression of highly conserved genes (e.g. the phosphate transporter system). In addition, we found evidence for genetic variation in the acquisition, assimilation, and allocation of P. Such effects of P supply should impinge on fitness, and drive evolutionary change. Further understanding of the inter-and intraspecific fitness consequences to imbalances in the availability of P in relation to other biogenic elements may be useful to disentangle primary mechanisms driving diversifications. We argue that studying the interactions between stoichiometric constraints and underlying genes is relevant to the majority of organisms, and conclude by furnishing information on designing and interpreting experiments using this approach.

Increased carbon dioxide availability alters phytoplankton stoichiometry and affects carbon cycling and growth of a marine planktonic herbivore

“…Disposing of surplus C by respiration is a common mechanism, reported from a range of aquatic consumers including Daphnia, the copepod A. tonsa and the flagellate Oxyrrhis marina (Hantzsche and Boersma 2010; Malzahn Jensen and Hessen 2007). Among the mechanisms proposed for the increase in respiration rate are increased activity, such as increased appendage beat rate (Jeyasingh and Weider 2007;Plath and Boersma 2001), so-called 'wastage' respiration (Zanotto et al 1997) and respiration decoupled from other metabolism in the form of increased heat production (Trier and Mattson 2003). The increased metabolic activity underlying these mechanisms for the disposal of leftover C appears to come at a cost to the consumer (Hessen and Anderson 2008;Raubenheimer and Simpson 1999), although the exact nature of these costs is still not entirely clear (see Hessen and Anderson 2008).…”

Eco-evolutionary dynamics

“…This signature is expected to be the strongest when populations are not already density limited Kinnison & Hairston 2007). As another example, landscape features can influence the distribution of genetic diversity at the individual and population levels ( Jeyasingh & Weider 2007;Clark et al 2008), thus affecting gene frequencies. If the change in gene frequencies translates into phenotypic trait changes that affect demographic rates (such as reproduction, survival or dispersal), then, ultimately, the genetic change will affect population dynamics ).…”

Can resource costs of polyploidy provide an advantage to sex?

“…This would include (1) estimation of DNA and RNA contributions to biomass (Neiman et al, 2009), (2) mesocosm experiments estimating the sensitivity of growth rate or other fitness correlates to dietary P availability, (3) lab and field experiments examining whether P availability mediates outcomes of competition between sexual vs. asexual taxa and/or taxa of different ploidy, (4) observational and experimental studies examining whether asexual polyploids become more prevalent than diploid relatives in communities under P-rich conditions and (5) laboratory experiments and genetic analyses comparing traits relevant to nutrient demand (for example, genome size, cell size, P-demand, rRNA gene copy number, gene expression patterns, P, and RNA content) in populations from environments with a range of P availability and in established vs. recently derived polyploid lineages. This last approach could provide insight into whether there is local adaptation and acclimation to P availability (Elser et al, 2000a(Elser et al, , 2006DeMott and Pape, 2005;Jeyasingh and Weider, 2007;Jeyasingh et al, 2009) and whether polyploids change predictably over evolutionary time (Leitch and Bennett, 2004). The answers to these questions will provide important steps towards understanding whether and how evolution is mediated by the interaction between P requirements and P availability.…”