Ecological genetics of habitat-forming plants

O'Reilly Berkeley, Sara-Xaali (2023) Ecological genetics of habitat-forming plants. Doctoral thesis (PhD), Manchester Metropolitan University.

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Abstract

Genetic diversity is an important component of biodiversity. Studying genetic diversity within species has become a key aspect of conservation biology, but is often neglected when studying the interactions among species. Increasingly, community genetics research is revealing relationships between plant genetic diversity and the community composition of associated organisms. However, the majority of these studies have taken place in temperate systems. In this thesis, we explore relationships between plant genotype and wider species diversity in an area of tropical rainforest in the Ecuadorian Amazon, using epiphytic bromeliads and the false-bird-of-paradise plant Heliconia stricta. Using a combined observational and experimental approach, we aimed to establish whether plant genotype influences community composition in these highly diverse tropical systems and their importance relative to environmental variables. We studied natural bromeliad communities of Aechmea hoppii and A. nidularioides in-situ, first establishing what environmental and plant factors affected the composition of their invertebrate and prokaryotic communities (Chapters II and III), and then analysing whether bromeliad genetic distance correlated with community distance (Chapter IV). We established in-situ experimental plots of multiple Heliconia stricta genotypes and analysed the effect of plant genotype on herbivory (Chapter V). Finally, we designed an ex-situ experiment using Neoregelia schultesiana bromeliads in a greenhouse to compare effects of plant genotype in the absence of environmental variation (Chapter VI). In the wild, bromeliad size, forest type, and the height in the tree at which the bromeliad was found to explain small but significant proportions of the variation in invertebrate and prokaryotic communities (Chapter II), depending on what taxonomic level was considered (Chapter III). However, bromeliad genotype did not correlate with prokaryotic or invertebrate community composition (Chapter IV). Contrary to this, Heliconia genotype did affect herbivory and growth rate – some genotypes were consumed or grew consistently more than others (Chapter V). Finally, there were genotypic differences between bromeliads in a greenhouse setting (Chapter VI). Taken together, the results of this thesis suggest that, despite the diversity and complexity of megadiverse tropical systems, plant genotype may affect some interactions with other organisms, but this cannot be assumed to be true for all interactions. It may be that the more organisms are involved and the less direct the interaction, the less likely it is that plant genotype will have an appreciable effect on wider community composition or ecosystem processes. We encourage the exploration of community genetics in a wider range of ecosystems, particularly in ecosystems and geographic regions where such studies have been absent or sparse.