Pedraza, F. | Search bioRxiv

bioRxiv2020

Determining which mechanisms underlie facilitation by tussocks in tropical high mountains and their relative importance

Facilitation by tussocks is common in high-altitude tropical environments. It is thought that facilitation results from stress amelioration, but it is unclear which of the many stressors acting in these environments is ameliorated. We aimed at determining the relative importance of different stressors as drivers of facilitation by the tussock Festuca tolucensis in Mexico. We manipulated five stressors in the field: minimum temperatures by using electric radiators that kept plants warm; maximum temperatures by means of reflective sand that precluded temperature build-up during the day; UV radiation by using screens opaque to UV; poor soil properties by comparing soils from beneath tussocks and from bare ground; and low water availability by adding vermiculite to the soil. The performance (survival and growth) of Mexerion sarmentosum (a plant usually associated with Festuca) in these treatments was compared to that recorded under tussocks and in bare ground. Amelioration of extreme temperatures had the largest positive effects on Mexerion survival. UV radiation and increased soil humidity did not affect survival, although humidity increased growth rates. Nevertheless, tussocks reduced the growth of Mexerion, which is consistent with observations of competition between plants and soil microorganisms favoured by tussocks. Our results highlight the importance of the extreme daily fluctuations in temperature that characterise tropical mountains as fundamental drivers of their dynamics.

ecology↗

bioRxiv2019

Retrieval of a well-established skill is resistant to distraction: evidence from an implicit probabilistic sequence learning task

The characteristics of acquiring new sequence information under dual-task situations have been extensively studied so far. Such a concurrent task has often been found to affect performance. In real life, however, we mostly perform a secondary task when the primary one is already well-acquired. The effect of a secondary task on the ability to retrieve well-established sequence representations remains elusive. The present study investigates whether accessing a well-acquired probabilistic sequence knowledge is affected by a concurrent task. Participants acquired non-adjacent regularities in a perceptual-motor implicit probabilistic sequence learning task. After a 24-hour offline period, participants were tested on the same sequence learning task under dual-task or single-task conditions. Here we show that although the secondary task significantly prolonged the overall reaction times in the primary task, the access to the previously learned probabilistic representations remained intact. Our results highlight the importance of studying the dual-task effect not only in the learning phase but also during memory access.

neuroscience↗