Sandra Díaz

Chemistry and toughness predict leaf litter decomposition rates over a wide spectrum of functional types and taxa in central Argentina.

Litter decomposition, a major determinant of ecosystem functioning, is strongly influenced by the litter quality of different species. We aimed at (1) relating interspecific variation in leaf litter decomposition rate to the functional types different species belong to; and (2) understanding the chemical and/or physical basis for such variation and its robustness to environmental factors. We selected 52 Angiosperms from a climatic gradient in central-western Argentina, representing the widest range of functional types and habitats published so far. Ten litter samples of each species were simultaneously buried for 9 weeks during the 1996 summer in an experimental decomposition bed. Decomposition rate was defined as the percentage of dry mass loss after incubation. Chemical litter quality was measured as carbon (C) content, nitrogen (N) content, and C-to-N ratio. Since tensile strength of litter and living leaves were strongly correlated, the latter was chosen as an indicator of physical litter quality. A subset of 15 species representing different functional types was also incubated in England for 15 weeks, following a similar experimental procedure. Litter C-to-N and leaf tensile strength of the leaves showed the strongest negative associations with decomposition rate, both at the species and at the functional-type level. Decomposition rates of the same species in Argentina and in England were strongly correlated. This reinforces previous evidence that species rankings in terms of litter decomposition rates are robust to methodological and environmental factors. This paper has shown new evidence of plant control over the turnover of organic matter through litter quality, and confirms, over a broad spectrum of functional types, general models of resource allocation. The strong correlations between leaf tensile strength – a trait that is easy and quick to measure in a large number of species – decomposition rate, and C-to-N ratio indicate that leaf tensile strength can be useful in linking plant quality to decomposition patterns at the ecosystem level.

Response to Vergara et al. (2015)—Fruiting phenology as a “triggering attribute” of invasion process: Do invasive species take advantage of seed dispersal service provided by native birds?

In a recent article, Vergara et al. (2015) present the results of a study aimed at testing our triggering attribute model (TA, Gurvich et al. 2005) in a woodland ecosystem in central Argentina. To that end, they compared the bird assemblage that consumes fruits of three woody species, a native tree (Celtis ehrenbergiana) and two congeneric invasive shrubs (Pyracantha angustifolia and P. coccinea). C. ehrenbergiana disperses its fruit in summer, P. angustifolia does so in winter, and P. coccinea shows some overlap in the dispersal period with the native tree [see Fig. 2 in Vergara et al. (2015)]. The authors predicted that, according to the TA approach, the diversity and abundance of frugivorous birds, and their fruit consumption, should be greater for P. angustifolia than for the other two species. They found no difference among the three species and conclude that the TA theory is not at play in the system. While the study provides valuable insight into the frugivorous bird assemblage, we disagree on the main conclusion, in particular regarding the logic behind the testing of the TA approach. According to Gurvich et al. (2005), a TA is defined as a vegetative or regenerative attribute of an exotic species that is discontinuously distributed in comparison to those of the resident community. This attribute allows the exotic species to benefit from a resource that is permanently or temporarily unused by the resident community, triggering its spread over the landscape. The winter fruit phenology of two fleshyfruited invaders (P. angustifolia and Ligustrum lucidum) was proposed as an example of TA that would allow these two species to take advantage of a resource (bird dispersal) that resident fleshy-fruited species—whose fruits are ripe in summer and autumn—cannot tap during the winter. Therefore, the empirical prediction under the TA model is that P. angustifolia should show dispersal rates similar to those of the dominant fleshy-fruited resident of the invaded system. Indeed, the data provided by Vergara et al. (2015) support this prediction, showing that P. angustifolia has the same assemblage of bird dispersers as C. ehrenbergiana, but operating during a different seasonal period. Unlike what Vergara et al. (2015) have done, to test whether P. coccinea benefits from bird dispersal (compared to native fleshy-fruited species) would require the assessment of bird assemblages in both the coupled and uncoupled dispersal periods [see Fig. 2 in Vergara et al. (2015)]. The release from bird predators in the overlapping period is quite interesting and remains to be tested in the unfavorable (cold) season. However, we agree with the authors that dispersal would probably not be the TA that underlies the success of P. coccinea in the D. E. Gurvich (&) P. A. Tecco S. Dı́az Instituto Multidisciplinario de Biologı́a Vegetal (FCEFyN, CONICET-UNC), Av. Vélez Sarsfield 1611, CC495, CP5000, Córdoba, Argentina e-mail: degurvich@gmail.com

A novel meta‐analytical approach to improve systematic review of rates and patterns of microevolution

Abstract A classic topic in ecology and evolution, phenotypic microevolution of quantitative traits has received renewed attention in the face of rapid global environmental change. However, for plants, synthesis has been hampered by the limited use of standard metrics, which makes it difficult to systematize empirical information. Here we demonstrate the advantages of incorporating meta‐analysis tools to the review of microevolutionary rates. We perform a systematic survey of the plant literature on microevolution of quantitative traits over known periods of time, based on the scopus database. We quantify the amount of change by standard mean difference and develop a set of effect sizes to analyze such data. We show that applying meta‐analysis tools to a systematic literature review allows the extraction of a much larger volume of information than directly calculating microevolutionary rates. We also propose derived meta‐analysis effect sizes (h, LG and LR) which are appropriate for the study of evolutionary patterns, the first being similar to haldanes, the second and third allowing the application of a preexisting analytical framework for the inference of evolutionary mechanisms. This novel methodological development is applicable to the study of microevolution in any taxa. To pilot test it, we built an open‐access database of 1,711 microevolutionary rates of 152 angiosperm species from 128 studies documenting population changes in quantitative traits following an environmental novelty with a known elapsed time (<260 years). The performance of the metrics proposed (h, LG and LR) is similar to that of preexisting ones, and at the same time they bring the advantages of lower estimation bias and higher number of usable observations typical of meta‐analysis.