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• 1. [Article] Reproductive Output of Mosses Under Experimental Warming on Fildes Peninsula, King George Island, Maritime Antarctica

  Background: Mosses dominate much of the vegetation in the Antarctic, but the effect of climatic change on moss growth and sexual reproduction has scarcely been studied. In Antarctica, mosses infrequently ...

  Citation × Citation Citation Abstract Copy Title: Reproductive Output of Mosses Under Experimental Warming on Fildes Peninsula, King George Island, Maritime Antarctica Author: Casanova-Katny, Angélica, Torres-Mellado, G. A., Eppley, Sarah M. Year: 2016 Background: Mosses dominate much of the vegetation in the Antarctic, but the effect of climatic change on moss growth and sexual reproduction has scarcely been studied. In Antarctica, mosses infrequently produce sporophytes; whether this is due to physiological limitation or an adaptive response is unknown. We studied the effect of experimental warming (with Open Top Chambers, OTCs) on sporophyte production on Fildes Peninsula, King George Island for four moss species (Bartramia patens, Hennediella antarctica, Polytrichastrum alpinum, and Sanionia georgicouncinata). To determine whether reducing cold stress increases sexual reproduction as would be predicted if sex is being constrained due to physiological limitations, we counted sporophytes for these four moss species in OTC and control plots during two years. Also, we measured sporophyte size for a smaller sample of sporophytes of two species, B. patens and H. antarctica, in the OTC and control plots. Results: After 2 years of the experimental treatment, maximum daily air temperature, but not daily mean air temperature, was significantly higher inside OTCs than outside. We found a significant species by treatment effect for sporophyte production, with more sporophytes produced in OTCs compared with controls for B. patens and P. alpinum. Also, sporophytes of B. patens and H. antarctica were significantly larger in the OTCs compared with the control plots. Conclusions: Our results suggest that the lack of sexual reproduction in these Antarctic mosses is not adaptive but is constrained by current environmental conditions and that ameliorating conditions, such as increased temperature may affect sexual reproduction in many Antarctic mosses, altering moss population genetics and dispersal patterns. Title: Reproductive Output of Mosses Under Experimental Warming on Fildes Peninsula, King George Island, Maritime Antarctica Author: Casanova-Katny, Angélica, Torres-Mellado, G. A., Eppley, Sarah M. Year: 2016 Background: Mosses dominate much of the vegetation in the Antarctic, but the effect of climatic change on moss growth and sexual reproduction has scarcely been studied. In Antarctica, mosses infrequently produce sporophytes; whether this is due to physiological limitation or an adaptive response is unknown. We studied the effect of experimental warming (with Open Top Chambers, OTCs) on sporophyte production on Fildes Peninsula, King George Island for four moss species (Bartramia patens, Hennediella antarctica, Polytrichastrum alpinum, and Sanionia georgicouncinata). To determine whether reducing cold stress increases sexual reproduction as would be predicted if sex is being constrained due to physiological limitations, we counted sporophytes for these four moss species in OTC and control plots during two years. Also, we measured sporophyte size for a smaller sample of sporophytes of two species, B. patens and H. antarctica, in the OTC and control plots. Results: After 2 years of the experimental treatment, maximum daily air temperature, but not daily mean air temperature, was significantly higher inside OTCs than outside. We found a significant species by treatment effect for sporophyte production, with more sporophytes produced in OTCs compared with controls for B. patens and P. alpinum. Also, sporophytes of B. patens and H. antarctica were significantly larger in the OTCs compared with the control plots. Conclusions: Our results suggest that the lack of sexual reproduction in these Antarctic mosses is not adaptive but is constrained by current environmental conditions and that ameliorating conditions, such as increased temperature may affect sexual reproduction in many Antarctic mosses, altering moss population genetics and dispersal patterns. Close

• 2. [Article] Bayesian Methods for Comparing Species Physiological and Ecological Response Curves

  Many ecological questions require information on species' optimal conditions or critical limits along environmental gradients. These attributes can be compared to answer questions on niche partitioning, ...

  Citation × Citation Citation Abstract Copy Title: Bayesian Methods for Comparing Species Physiological and Ecological Response Curves Author: Ashcroft, Michael B., Casanova-Katny, Angélica, Mengersen, Kerrie, Rosenstiel, Todd N., Turnbull, Johanna D., Wasley, Jane, Waterman, Melinda J., Zúñiga, Gustavo E., Robinson, Sharon A. Year: 2016 Many ecological questions require information on species' optimal conditions or critical limits along environmental gradients. These attributes can be compared to answer questions on niche partitioning, species coexistence and niche conservatism. However, these comparisons are unconvincing when existing methods do not quantify the uncertainty in the attributes or rely on assumptions about the shape of species' responses to the environmental gradient. The aim of this study was to develop a model to quantify the uncertainty in the attributes of species response curves and allow them to be tested for substantive differences without making assumptions about the shape of the responses. We developed a model that used Bayesian penalised splines to produce and compare response curves for any two given species. These splines allow the data to determine the shape of the response curves rather than making a priori assumptions. The models were implemented using the R2OpenBUGS package for R, which uses Markov Chain Monte Carlo simulation to repetitively fit alternative response curves to the data. As each iteration produces a different curve that varies in optima, niche breadth and limits, the model estimates the uncertainty in each of these attributes and the probability that the two curves are different. The models were tested using two datasets of mosses from Antarctica. Both datasets had a high degree of scatter, which is typical of ecological research. This noise resulted in considerable uncertainty in the optima and limits of species response curves, but substantive differences were found. Schistidium antarcticiwas found to inhabit wetter habitats than Ceratodon purpureus, and Polytrichastrum alpinum had a lower optimal temperature for photosynthesis than Chorisodontium aciphyllum under high light conditions. Our study highlights the importance of considering uncertainty in physiological optima and other attributes of species response curves. We found that apparent differences in optima of 7.5 °C were not necessarily substantive when dealing with noisy ecological data, and it is necessary to consider the uncertainty in attributes when comparing the curves for different species. The model introduced here could increase the robustness of research on niche partitioning, species coexistence and niche conservatism. Title: Bayesian Methods for Comparing Species Physiological and Ecological Response Curves Author: Ashcroft, Michael B., Casanova-Katny, Angélica, Mengersen, Kerrie, Rosenstiel, Todd N., Turnbull, Johanna D., Wasley, Jane, Waterman, Melinda J., Zúñiga, Gustavo E., Robinson, Sharon A. Year: 2016 Many ecological questions require information on species' optimal conditions or critical limits along environmental gradients. These attributes can be compared to answer questions on niche partitioning, species coexistence and niche conservatism. However, these comparisons are unconvincing when existing methods do not quantify the uncertainty in the attributes or rely on assumptions about the shape of species' responses to the environmental gradient. The aim of this study was to develop a model to quantify the uncertainty in the attributes of species response curves and allow them to be tested for substantive differences without making assumptions about the shape of the responses. We developed a model that used Bayesian penalised splines to produce and compare response curves for any two given species. These splines allow the data to determine the shape of the response curves rather than making a priori assumptions. The models were implemented using the R2OpenBUGS package for R, which uses Markov Chain Monte Carlo simulation to repetitively fit alternative response curves to the data. As each iteration produces a different curve that varies in optima, niche breadth and limits, the model estimates the uncertainty in each of these attributes and the probability that the two curves are different. The models were tested using two datasets of mosses from Antarctica. Both datasets had a high degree of scatter, which is typical of ecological research. This noise resulted in considerable uncertainty in the optima and limits of species response curves, but substantive differences were found. Schistidium antarcticiwas found to inhabit wetter habitats than Ceratodon purpureus, and Polytrichastrum alpinum had a lower optimal temperature for photosynthesis than Chorisodontium aciphyllum under high light conditions. Our study highlights the importance of considering uncertainty in physiological optima and other attributes of species response curves. We found that apparent differences in optima of 7.5 °C were not necessarily substantive when dealing with noisy ecological data, and it is necessary to consider the uncertainty in attributes when comparing the curves for different species. The model introduced here could increase the robustness of research on niche partitioning, species coexistence and niche conservatism. Close