Marion Island bryophytes: evidence for functional types based on traits related to photosynthesis and desiccation tolerance

Tonkie, Jacqueline Nicole (2016-03)

Thesis (MSc)--Stellenbosch University, 2016.

Thesis

ENGLISH ABSTRACT: There is currently a worldwide interest in grouping species on the basis of their functional characteristics into plant functional types (PFTs). This reduces the complexity of models that predict the effects of global change on vegetation and ecosystem processes. Marion Island has vegetation dominated by bryophytes and is experiencing intense climate change. However, there is no accepted scheme and no consensus on the most useful traits for a bryophyte PFT classification. This study aimed at grouping 38 of the island bryophyte species into functional groups. A suite of 14 photosynthetic traits related to light or desiccation response were obtained from chlorophyll fluorescence quenching analysis and water relations. The characteristics were subjected to analysis of variance, box plot rankings, principal component and clustering analyses to group the species into functional types. Seven light response groups and nine desiccation response groups were recognized. Six groups were recognized in the combined analysis of light and desiccation traits. The species with the highest photosynthetic capacity and lowest photoinhibition had low or moderate saturated moisture content, dried out slowly, low or moderate photoprotection capability in high light and when desiccated and moderate recovery of photochemistry upon rehydration. The species with the lowest photosynthetic capacity and highest photoinhibition had the highest saturated moisture content, dried out very fast, had low photoprotective capability in high light and when desiccated and showed very low to moderate recovery. The group of species with low photosynthetic capacity was distinguished from the group with the lowest photosynthetic capacity by having a higher quantum yield of electron transport at the optimal photosynthetically active radiation (PAR). The two groups consisting of moderate or high photosynthetic capacity species were distinguished by the fraction of open reaction centres in high light and the ability to recover photochemistry upon rehydration. The group consisting of species with moderate photosynthetic capacity had a moderate fraction of open reaction centres in high light, moderate photoprotective capability when desiccated and high recovery of photochemistry upon rehydration. Correspondence analysis shows that the groupings are related to phylogeny, especially at the phylum level, and the species belonging to the same genus mostly had similar light and desiccation response characteristics. There is a strong correspondence between functional groupings, light regime and habitat moisture. The light response traits, particularly photoinhibition, are strongly associated with light regime. Photosynthetic capacity, moisture content and ability to recover photochemistry upon rehydration, correspond to habitat moisture. Life form was also strongly associated with functional groupings, particularly with the desiccation response traits.

AFRIKAANSE OPSOMMING: Daar is tans 'n wêreldwye belangstelling in die groepering van spesies in Plantfunksie Tipes (PFTs) volgens hul funksionele karaktereienskappe. Dit verminder die kompleksiteit van modelle wat die uitwerkings van aardverandering op plantegroei en ekosisteemprosesse voorspel. Marioneiland se plantegroei word oorheers deur briofiete, en ervaar intense klimaatverandering. Daar is egter geen aanvaarde skema en geen konsensus wat die mees nuttige eienskappe vir 'n briofiet PFT klassifikasie betref nie. Hierdie studie is daarop gemik om 38 van die eiland se briofietspesies in funksionele groepe te groepeer. 'n Suite van 14 fotosintetiese eienskappe water verband hou met lig- of uitdrogingreaksies is verkry vanaf chorofilflouressensie blus-ontleding en water-verwantskappe. Die karaktereienskappe is aan die ontleding van variansie, boksgrafiek-ranglyste en hoofkomponent- en groeperings-ontledings onderwerp om die spesies in funksionele tipes te groepeer. Sewe ligreaksie- en nege uitdrogingsreaksie-groepe is bevestig. Ses groepe is bevestig in die gesamentlike ontleding van lig- en uitdrogings-eienskappe. Die spesie met die hoogste fotosintetiese kapasiteit en die laagste fotoinhibisie (photoinhibition) het ‘n lae of matige versadigde voginhoud. Hierdie spesie het ook stadig uitgedroog, het lae of matige fotobeskermingsvermoë in skerp lig (high light) en wanneer dit uitgedroog is, en het matige herstel van fotochemie getoon wanneer dit gerehidreer is. Die spesie met die laagste fotosintetiese kapasiteit en hoogste fotoinhibisie het die hoogste versadigde voginhoud gehad en het baie vinnig uitgedroog. Hierdie spesie het ook ‘n lae fotobeskermingsvermoë in skerp lig wanneer dit uitgedroog is en het baie lae tot matige herstel getoon. Die groep wat bestaan uit spesies met lae fotosintetiese kapasiteit is onderskei van die groep met die laagste fotosintetiese kapasiteit deur 'n hoë kwantumopbrengs van elektronvervoer by die optimale Fotositeties Aktiewe Bestraling (FAB). Die twee groepe wat bestaan uit spesies met 'n matige of hoë fotositetiese kapasiteit was onderskei deur die breukdeel van oop reaksie-sentrums in skerp lig en die vermoë om fotochemie te herstel met rehidrasie. Die groep wat bestaan uit spesies met matige fotosintetiese kapasiteit het 'n matige breukdeel van oop reaksie-sentrums in skerp lig, matige fotobeskermingsvermoë en 'n hoë herstel van fotochemie met rehidrasie gehad. Ooreenkomsontleding het gewys dat die groeperings wel ooreenstem met filogenie, veral op die filumvlak, en die spesies wat aan dieselfde genus behoort het meestal soortgelyke lig- en uitdrogings-reaksie karaktereienskappe gehad. Daar is 'n sterk ooreenstemming tussen funksionele groeperings, ligtoestande en habitat vogtigheid. Die ligreaksie-eienskappe, veral fotoinhibisie, hou sterk verband met lig regime (light regime). Fotosintetiese kapasiteit, voginhoud en die vermoë om fotochemie te herstel met rehidrasie stem ooreen met habitat vogtigheid. Lewensvorm het ook sterk ooreengestem met funksionele groeperings, veral met die uitdrogingsreaksie-eienskappe.

Please refer to this item in SUNScholar by using the following persistent URL: http://hdl.handle.net/10019.1/98851
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