Meta-analysis reveals microevolution in grassland plant species under contrasting management

Abstract

Grassland species might be under differential selection pressure due to management regimes by man or unmanaged grazers. To investigate microevolutionary changes in plants, I used a meta-analysis and a comparative approach. This analysis incorporates 28 studies on 19 species in 3 paired management regimes with a total of 152 reported trait values resulting in 40 pooled Hedge's d effect sizes on genetic, vegetative and reproductive traits as well as 83 Hedge's ds of 14 specific traits. Of the pooled and specific traits, 60 and 72 % indicated divergent selection pressures within a management regime. The pooled Hedge's ds did not differ among the management regimes. Within mown versus grazed sites, trait groups were affected differently with increased reproductive traits in plants originating from grazed sites. In the other management regimes, the trait groups were affected similarly, except of some specific traits. Longevity, palatability, clonality and biome origin did not explain differences in pooled effect sizes, but tended to explain differences in some specific traits. Overall, general selection patterns were rare probably due to a high heterogeneity of among and within species responses, which might level each other out. Moreover, the number of data points per group of interest is often low and thus, for a final conclusion more studies are needed. Nonetheless, the divergent plant reactions indicate that selection pressures within paired management regimes might be large enough to induce microevolutionary changes in grasslands. Subsequently, the increased variation within species under different management techniques might buffer species persistence in the long term.

Evolutionary responses to land use in eight common grassland plants

“…Like the studies mentioned above, we also found that although all of the studied species showed significant genetic differentiation in relation to land‐use intensity, these patterns were generally rather species‐specific and were not even consistent within the functional groups of grasses ( Arrhenatherum , Bromus , Festuca , Poa ) or herbs (C erastium , Heracleum , Medicago , Veronica ), not even between species with very similar life histories such as Cerastium and Veronica . Our study thus corroborates previous findings that genetic differentiation in response to land use is frequent but also very variable across species (Pluess ). The same environmental factors that constitute strong selection pressures on some species, may be irrelevant to others (Bradshaw ; Futuyma ).…”

Transgenerational effects of land use on offspring performance and growth in Trifolium repens

“…However, there were no general patterns in the direction of the differences, and it was not clear whether the differences that were found are adaptive (Pluess 2013). This lack of a general pattern could be partly due to the low number of studies for each comparison or to variation in growth conditions among studies.…”

“…One possible adaptive explanation for this pattern is that spread through vegetative reproduction is only beneficial for plants in sites where plants and their stolons are less likely to get damaged by mowing and grazing. Another explanation could be that a small clone size might help plants to avoid detection by herbivores (Pluess 2013).…”

“…A recent meta-analysis showed that 60 % of commongarden studies testing for evolutionary effects (or maternal carryover effects) of land use on plants in grasslands found differences between plants from sites with different landuse regimes (Pluess 2013). However, there were no general patterns in the direction of the differences, and it was not clear whether the differences that were found are adaptive (Pluess 2013).…”

Mind the gaps when using science to address conservation concerns

“…This special issue on biodiversity of European grasslands (see Habel et al 2013) combines contributions both on fundamental biodiversity research and biodiversity conservation. These papers can be classified into four main topics: (1) effects of abiotic and biotic factors on species assemblages and richness (Horváth et al 2013;Moeslund et al 2013;Morris et al 2013;Weiss et al 2013;Zelnik and Carni 2013); (2) natural and anthropogenically induced gradients along temporal and spatial scales (Albrecht and Haider 2013;Bieringer et al 2013;Filz et al 2013;Pipenbaher et al 2013); (3) the effect of man-made modifications of habitats on species composition, in particular eutrophication and abandonment versus habitat restoration (Bonanomi et al 2013;Lauterbach et al 2013;Rácz et al 2013;Weiss et al 2013;Wiezik et al 2013); and (4) genetics and physiology within single species or species groups (Habel et al 2013;Pluess 2013;Wellstein et al 2013). While these papers touch on several important aspects of conservation science, they mostly focus on single model taxa and/or are mostly restricted to investigating relationships among only a few factors.…”