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Examining the Maternal Investment of the Calyptra and Its Influence on the Sporophyte Offspring University of Tennessee, Knoxville TRACE: Tennessee Research and Creative Exchange Masters Theses Graduate School 5-2021 Examining the maternal investment of the calyptra and its influence on the sporophyte offspring Alessandra Marie Cabrera Aromin [email protected] Follow this and additional works at: https://trace.tennessee.edu/utk_gradthes Part of the Bryology Commons Recommended Citation Aromin, Alessandra Marie Cabrera, "Examining the maternal investment of the calyptra and its influence on the sporophyte offspring. " Master's Thesis, University of Tennessee, 2021. https://trace.tennessee.edu/utk_gradthes/6204 This Thesis is brought to you for free and open access by the Graduate School at TRACE: Tennessee Research and Creative Exchange. It has been accepted for inclusion in Masters Theses by an authorized administrator of TRACE: Tennessee Research and Creative Exchange. For more information, please contact [email protected]. To the Graduate Council: I am submitting herewith a thesis written by Alessandra Marie Cabrera Aromin entitled "Examining the maternal investment of the calyptra and its influence on the sporophyte offspring." I have examined the final electronic copy of this thesis for form and content and recommend that it be accepted in partial fulfillment of the equirr ements for the degree of Master of Science, with a major in Ecology and Evolutionary Biology. Jessica M. Budke, Major Professor We have read this thesis and recommend its acceptance: Xingli Giam, Joseph H. Williams Accepted for the Council: Dixie L. Thompson Vice Provost and Dean of the Graduate School (Original signatures are on file with official studentecor r ds.) Examining the influence of calyptra size on sporophyte morphology in Funariaceae mosses A Thesis Presented for the Master of Science Degree The University of Tennessee, Knoxville Alessandra Marie Cabrera Aromin May 2021 ACKNOWLEDGEMENTS Thank you to my committee (alphabetical order) Dr. Jessica Budke, Dr. Xingli Giam, and Dr. Joe Williams for their guidance and expertise. ii ABSTRACT Maternal care is a critical component of offspring survival, development, and fitness in many organisms. In bryophytes (mosses, liverworts, and hornworts), offspring sporophytes are physically attached to and nutritionally dependent on the maternal gametophyte throughout their lifespan. Mosses have a structure called the calyptra, which is a maternal cap of gametophyte tissue that covers the sporophyte apex during critical developmental stages. The calyptra has shown to positively impact sporophyte survival and fitness. However, the influence of calyptra size on sporophyte development, survival, and fitness have not been tested. We hypothesize that sporophytes with larger calyptra experimentally placed on their apex will be taller and produce more spores. To test our predictions, we conducted a removal replacement experiment. We found that larger calyptra influenced sporophyte growth and produced longer capsules, but sporophyte fitness was not impacted. Maternal investment in larger calyptra and its positive effect on sporophyte height may also directly impact spore dispersal and in relation to species distributions and fitness. iii TABLE OF CONTENTS Section 1: Introduction ........................................................................................... 1 Section 2: Materials and Methods ......................................................................... 2 Species ........................................................................................................... 2 Laboratory populations ................................................................................... 2 Experiment ..................................................................................................... 3 Statistical analyses ......................................................................................... 4 Survival analyses ............................................................................................ 5 Section 3: Results .................................................................................................. 6 Reproductive output and sporophyte development ........................................ 6 Survival analyses ............................................................................................ 6 Developmental stage analyses ....................................................................... 7 Section 4: Discussion ............................................................................................ 7 Section 5: Conclusion ........................................................................................ 9 List of References ................................................................................................ 10 Appendix .............................................................................................................. 13 Vita ....................................................................................................................... 25 iv LIST OF FIGURES Figure 1: Moss Diagram (modified from Haig, 2013). .......................................... 14 Figure 2: Developmental Stages Funaria hygrometrica (modified from Budke et al., 2012). ...................................................................................................... 15 Figure 3: Treatment 2 and Treatment 3. .............................................................. 16 Figure 4: Treatment 2 and Treatment 4. .............................................................. 18 Figure 5: Physcomitrium pyriforme Capsule Weight. ........................................... 20 Figure 6: Survival Analysis Funaria hygrometrica. .............................................. 21 Figure 7: Survival Analysis Physcomitrium pyriforme. ......................................... 22 Figure 8: Developmental Stages Funaria hygrometrica. ..................................... 23 Figure 9: Developmental Stage Physcomitrium pyriforme. .................................. 24 SECTION 1: INTRODUCTION Bryophytes include three morphologically distinct clades: Anthocerotophyta (hornworts), Bryophyta (mosses), Marchantiophyta (liverworts; Renzaglia et al., 2000, 2018; Puttick et al., 2018). All land plants have life cycles that undergo an alternation of phases between haploid gametophytes and diploid sporophytes. Bryophytes are the only terrestrial plants that are gametophyte dominant. The gametophyte is the main photosynthetic phase that is observed on the landscape, while the bryophyte sporophytes are smaller, physically attached to, and nutritionally dependent on the gametophyte throughout their lifespan (Vanderpoorten and Goffinet, 2009). The sporophytes arise within the female sex organ, the archegonium, and develops to produce the sporangia (capsule) in which meiosis occurs and spores are produced. The sporophytes and sporangia differ morphologically across the three lineages. Liverwort sporangia are elevated above the substrate by an ephemeral seta that generally increases in length through cell elongation rather than cell division. The hornwort sporangium is highly elongated and the sporophyte and lacks a seta (Vanderpoorten and Goffinet, 2009). In mosses, terminal sporangium is elevated by a seta that persists until long after spore dispersal and increases in length via both cell division and elongation (Figure 1 in Appendix). Mosses have a maternal gametophytic structure, known as the calyptra. The calyptra is covered in relatively thick and layered cuticle (Budke et al., 2011), which impacts the overall survival and fitness of the sporophyte; it protects the developing sporophyte from desiccation and increases sporophyte survival and reproductive output (Budke et al., 2013). The calyptra is formed from tissues of the archegonium and the gametophyte stem below and surrounds the sporophyte during early development (Budke, 2019). As the sporophyte develops and increases in height, the calyptra detaches from the rest of the maternal gametophyte and remains on the sporophyte apex. During development, the sporophyte apex moves beyond the still boundary layer of the substrate and is exposed to increasing dehydration stress (Rice and Schneider, 2004). This makes the calyptra especially critical for taller sporophytes. It is important to study structural maternal investments, which could be interpreted as maternal care, comparatively in order to understand on how different moss species have evolved to protect their offspring. As previous observations and studies have pointed out, the calyptra plays an important role in sporophyte development (Paolillo, 1968; French and Paolillo, 1975a, 1975b; Haig, 2013; Budke et al., 2011, 2012, 2013; Budke and Goffinet, 2016). However, the influence of maternal calyptra size on sporophyte survival, development, and fitness have not been explored. 1 To examine the impact of calyptra size on sporophyte survival, development, and fitness, a removal-replacement experiment was conducted. Funaria hygrometrica Hedw. and Physcomitrium pyriforme (Hedw.) Hampe, two species with contrasting sizes of calyptrae, were used. Both species are readily cultured in the laboratory and have been used for similar removal-replacement experiments; French and Paolillo, 1975a examined the role of the calyptra in capsule formation while Budke et al. 2013 investigated calyptra cuticles. Using species with different sizes of calyptrae will enable us to test the impact of calyptra size on sporophyte survival, development, and fitness. We hypothesize that
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