Results and Discussion
A total of 8 culture mediums of 18 (44%) produced growth in the treatments tested. One of five culture mediums with A. malouinusfragment samples (20%), three of six with C. picta fragment samples (50%), and four of six with wild moss fragment samples (67%) produced new growth (Table 1) based on the occurrence of light-colored green shoots and moss beds (Figure 1). Five of the nine (56%) fecal fragment inoculations treated to the peat soil treatment (three fromC. picta , one from A. malouinus , and one fromPolytrichum sp. ) and all three (100%) inoculations of fragmented wild mosses in the solid agar-Gamborg medium showed vegetative growth. On the contrary, no growth was observed in the agar-Gamborg for any of the six inoculations tested from the feces of both bird species.
Previous research has attempted to cultivate fragments found in fecesin vitro with some success (Wilkinson et al., 2017; Russo et al., 2020). In this study, we partially followed Russo et al.’s (2020) fragment-processing methods. However, we decided to set two growing conditions for the fragments recovered from the feces to increase the probability of bryophyte growth. These consisted of anex situ growth condition using commercial peat soil, and anin vitro condition using agar-Gamborg medium for both fragments from fecal and wild moss samples taken from the field. We predicted that the fragments from both wild moss and fecal samples would regenerate. Previous research described growth from bryophyte spores after 60 days (Proctor, 1961) and from bryophyte fragments after 11 days (Wilkinson et al., 2017). However, we did not observe signs of regeneration from our cultures until 42 days of growth.
Our reasoning for the chosen treatments was to test which, if any, would allow bryophyte fragment recovery and growth under lab conditions. Although the sample size was small, we observed clear evidence of bryophyte regeneration from feces of both bird species in the peat soil treatment (see Table 1). These results reveal that a small fraction of moss diaspores remains viable following the passage through the intestinal tract of both birds and is capable of regeneration in suitable conditions. Although small, our cases are significant. Given the volume of the feces and the number of feces defecated daily by each bird, if our results were multiplied by the number of birds per area and time, our results would translate into a large absolute number. Additionally, the growth evidence observed in the three wild mosses in the agar-Gamborg confirmed that the bryophytes sampled are totipotent, which is a necessary condition for effective endozoochory mechanisms.
It is plausible that the in vitro (agar-Gamborg) conditions could have yielded false negative results from the fecal sample fragments tested of both bird species (see Table 1), as moss diaspores may take longer to germinate in sterile conditions due to the necessary acclimation to the agar-Gamborg substrate and neutral pH conditions in the medium (Sabovljevic et al., 2014). However, there was evidence of bryophyte regeneration in fragments recovered from feces in the peat soil substrate. On the other hand, wild moss gametophyte growth was observed in samples inoculated both in agar-Gamborg medium and peat soil. Therefore, these results support the hypothesis of bird endozoochory of these bryophytes in the sub-Antarctic environment.