Passive warming reduces stress and shifts reproductive effort in the Antarctic moss,Polytrichastrum alpinum

Abstract

Background and Aims The Western Antarctic Peninsula is one of the most rapidly warming regions on Earth, and many biotic communities inhabiting this dynamic region are responding to these well-documented climatic shifts. Yet some of the most prevalent organisms of terrestrial Antarctica, the mosses, and their responses to warming have been relatively overlooked and understudied. In this research, the impacts of 6 years of passive warming were investigated using open top chambers (OTCs), on moss communities of Fildes Peninsula, King George Island, Antarctica.Methods The effects of experimental passive warming on the morphology, sexual reproductive effort and stress physiology of a common dioicous Antarctic moss, Polytrichastrum alpinum, were tested, gaining the first speciesspecific mechanistic insight into moss responses to warming in the Antarctic. Additionally community analyses were conducted examining the impact of warming on overall moss percentage cover and sporophyte production in intact Antarctic moss communities.Key Results Our results show a generally greater percentage moss cover under warming conditions as well as increased gametangia production in P. alpinum. Distinct morphological and physiological shifts in P. alpinum were found under passive warming compared with those without warming: warmed mosses reduced investment in cellular stress defences, but invested more towards primary productivity and gametangia development.Conclusions Taken together, results from this study of mosses under passive warming imply that in ice-free moss-dominated regions, continued climate warming will probably have profound impacts on moss biology and colonization along the Western Antarctic Peninsula. Such findings highlight the fundamental role that mosses will play in influencing the terrestrialization of a warming Antarctica.

Passive warming effect on soil microbial community and humic substance degradation in maritime Antarctic region

“…Each panel has five holes of 1 cm in diameter to allow for improved airflow and avoid excessive warming. The OTCs were previously tested for 2 years for resistance to Antarctic climatic conditions and are similar in design to others used in Signy and Anchorage Islands, Antarctica . Each corresponding control was demarcated region of the same size and shape as the OTC footprint within ∼3.0 m of each OTC.…”

Examination of Human Impacts on the Biodiversity and Ecology of Lichen and Moss Communities

“…Casanova-Katny et al (2016) found significant increases in sporophyte production in P. alpinum under passive warming OTC treatments after seven years of experimental warming, however we found no sporophytes in P. alpinum during our study. Our results are similar to those of Shortlidge et al (2016), who found increases in individual female and male gametangia production, but no increase in sporophyte production, in P. alpinum which suggests that warming may relieve environmental constraints on reproductive effort. Sexual reproduction in mosses may be limited by many factors such as spermlimitation (Rydgren et al 2006), resource limitation (Stark et al 2000(Stark et al , 2009 , and abiotic stress (Bowker et al 2000, Eppley et al 2011.…”

“…Our study is one of only two other studies to our knowledge that explores the effects of warming on moss reproductive output (Casanova-Katny et al 2016, Shortlidge et al 2016. We found that P. alpinum in warmed (OTC) plots exhibited significantly more female sex expression than control plots (Table 4.2 & Figure 4.8), similar to findings in two other Antarctic bryophyte studies (Casanova-Katny et al 2016, Shortlidge et al 2016). Casanova-Katny et al (2016) found significant increases in sporophyte production in P. alpinum under passive warming OTC treatments after seven years of experimental warming, however we found no sporophytes in P. alpinum during our study.…”

“…After eight years of passive warming, we observed no distinguishable effects on cryptogam community composition or species richness, a finding consistent with other Antarctic passive warming studies (Bokhorst et al 2007(Bokhorst et al , 2015 (Figure 4.3 & Figure 4.4b). However, we did find Bartramia patens occurred only in warmed (OTC) plots (Table 4.1), a common species recorded in other Antarctic studies Smith 1993a, Marshall andConvey 1997) and within OTC experiments (Casanova-Katny et al 2016, Shortlidge et al 2016) that found experimental warming has a positive effect on B.…”

“…Yet, increasing climate warming on the western Antarctic peninsula is anticipated to encourage the growth and spreading of moss vegetation in Antarctica, which will further influence terrestrial ecosystem succession (Turetsky 2003, Convey et al 2009 and hold implications for the microorganism and invertebrate communities they sustain (Convey et al 2009). Moreover, few studies on Antarctica mosses have examined the effects of warming on sexual reproduction (Casanova-Katny et al 2016, Shortlidge et al 2016 which is key to understanding dynamics of developing moss communities, and to our knowledge, no studies to date have examined both reproductive output and associated invertebrate communities of the dominant moss species, despite the important ecological connection of invertebrates and moss fertilization (Cronberg et al 2006, Rosenstiel et al 2012). Given the magnitude of terrestrial vegetative cover comprised of mosses in maritime Antarctica, the study of species-specific moss responses to warming is critical to better provide insight into specific organism's responses to warming and the links to larger ecosystem processes of terrestrialization in Antarctica.…”