Is foraging innovation lost following colonization of a less variable environment? A case study in surface‐ vs. cave‐dwelling Asellus aquaticus

Behavioral innovation is a key process for successful colonization of new habitat types. However, it is costly due to the necessary cognitive and neural demands and typically connected to ecological generalism. Therefore, loss of behavioral innovativeness is predicted following colonization of new, simple, and invariable environments. We tested this prediction by studying foraging innovativeness in the freshwater isopod Asellus aquaticus. We sampled its populations along the route of colonizing a thermokarstic water‐filled cave (simple, stable habitat with only bacterial mats as food) from surface habitats (variable environment, wide variety of food). The studied cave population separated from the surface populations at least 60,000 years ago. Animals were tested both with familiar and novel food types (cave food: bacterial mats; surface food: decaying leaves). Irrespective of food type, cave individuals were more likely to feed than surface individuals. Further, animals from all populations fed longer on leaves than on bacteria, even though leaves were novel for the cave animals. Our results support that cave A. aquaticus did not lose the ability to use the ancestral (surface) food type after adapting to a simple, stable, and highly specialized habitat.     

Do invasive species show higher phenotypic plasticity than native species and,if so,is it adaptive? A meta‐analysis

Do invasive plant species have greater phenotypic plasticity than non-invasive species? And, if so, how does this affect their fitness relative to native, non-invasive species? What role might this play in plant invasions? To answer these long-standing questions, we conducted a meta-analysis using data from 75 invasive/non-invasive species pairs. Our analysis shows that invasive species demonstrate significantly higher phenotypic plasticity than non-invasive species. To examine the adaptive benefit of this plasticity, we plotted fitness proxies against measures of plasticity in several growth, morphological and physiological traits to test whether greater plasticity is associated with an improvement in estimated fitness. Invasive species were nearly always more plastic in their response to greater resource availability than non-invasives but this plasticity was only sometimes associated with a fitness benefit. Intriguingly, non-invasive species maintained greater fitness homoeostasis when comparing growth between low and average resource availability. Our finding that invasive species are more plastic in a variety of traits but that non-invasive species respond just as well, if not better, when resources are limiting, has interesting implications for predicting responses to global change.     

Do Antarctic lichens modify microclimate and facilitate vascular plants in the maritime Antarctic? A comment to Molina‐Montenegro et al. ()

A recent article published by Molina‐Montenegro et al. (Journal of Vegetation Science24: 463) examines the association of Antarctic native plant and lichen species to the lichen Usnea antarctica on Fildes Peninsula, King George Island, maritime Antarctica. The authors report that on two sites, five out of 13 and four out of 11 species of lichens and mosses were spatially associated with U. antarctica, suggesting positive interactions between them. Although Deschampsia antarctica does not grow naturally associated with U. antarctica, Molina‐Montenegro et al. carried out a transplantation experiment to demonstrate that the macrolichen acts as a nurse plant, improving the survival of the grass. Serious conceptual and methodological discrepancies emerge from a critical evaluation of this study, challenging their conclusions. First, we suspect that the author confused some lichen taxa, and we also disagree with macrolichens being treated as cushion plants, because rootless, poikilohydric and poikilothermic thallophytes such as lichens are unable to create a stable, enclave‐like microhabitat as vascular cushion plants do. Indeed, a critical evaluation of some of the micro‐environmental parameters measured indicates that there are no biologically meaningful differences between the U. antarctica thalli and surrounding open areas. Second, the lack of consideration of the life history of the species under study leads to confusion when (a) referring to the succession sequence of species that colonize the studied area and (b) interpreting the putative distribution patterns promoted by Usnea versus the substrate preferences of associated species. Third, the authors intend to demonstrate experimentally that Usnea can facilitate the survival of D. antarctica plants, transplanting adult plants and not seedlings between the lichen thalli, and it is not clear how the grass was planted – between or within the lichens – as at both experimental sites the lichens grow on stones or rocks. Facilitative interactions are present in the Antarctic and may play a pivotal role in the structure and functioning of the fragile Antarctic ecosystems. However, more rigorous and well‐planned research is needed to assess its presence, importance and involved mechanisms.