Seed dispersal is crucial for plants to colonize new habitats and facilitate gene flow between populations. However, Pleistocene extinctions of large-bodied fruit-eating and seed-dispersing animals, known as ‘megafrugivores’, may have hindered the dispersal of plants with large fruits (> 4cm fruit length – ‘megafruits’). Plants with megafruits are common across the flora of Madagascar, especially within the palm (Arecaceae) family. This dissertation investigates the macro-ecological and micro-evolutionary consequences of dispersal limitation on palms with megafruits in Madagascar.
Specifically, I investigated three key aspects: (i) turnover or beta-diversity of palms on Madagascar and the distribution of their dispersal-related traits, (ii) the genetic diversity and genetic structure of three palms with megafruits compared to one palm with small fruits, and (iii) population size and migration rate changes over time of several Malagasy palm species with different ecological characteristics. To address these questions, historical ranges of extinct megafrugivores were reconstructed based on fossil sites, and data on extant frugivores, human activities, and climate were collected. Fieldwork in Madagascar provided genetic data for 12 palm species across 46 populations, from which I generated double digest restriction-site associated DNA sequencing data. Various interdisciplinary methods were employed, including redundancy analyses, variation partitioning, linear mixed effect models, species distribution models, and demographic modelling.
The findings indicate that the current turnover of palms in Madagascar is primarily influenced by extant frugivores and climate, with limited impact from extinct frugivores. Surprisingly, there is no evidence of decreased genetic diversity or increased genetic differentiation in megafruited palms due to the loss of their megafrugivore dispersers. Genetic diversity is positively associated with human population density but negatively influenced by road densities, possibly reflecting habitat fragmentation by humans. Connectivity between populations is linked to the number of shared extinct and extant (mega)frugivore species, for megafruited and small-fruited palm populations, respectively. This highlights the importance of past long-distance dispersal events by megafrugivores and human-mediated dispersal possibly maintaining connectivity for megafruited palms. Population declines are observed across palms since the Last Glacial Maximum, particularly in humid forest species rarely used by humans, while humid forest species with megafruits show recent migration disruption. In contrast, palm species with smaller fruits that are highly used by humans show less pronounced declines and more stable historical migration rates.
Overall, this dissertation illustrates that while the role of megafrugivores as seed dispersers is still evident in the genome of megafruited palms, other factors such as human-mediated dispersal and climate have an influence over the distribution, genetics and demographic histories of palms in Madagascar. It further shows how integrating genetic data with ecological data on species distributions, climate, human activities, can provide novel insights into the drivers of different facets of biodiversity of such a diverse group of plants such as palms.:Chapter 1 - General introduction ....................................................................................... 7
Background and problem statement...................................................................................... 7
Plant seed dispersal, fleshy fruits and frugivory ............................................................ 7
Megafauna and megafruits ............................................................................................ 9
Thesis scope .......................................................................................................................... 12
Madagascar as a model system .................................................................................... 12
Palms as a model system .............................................................................................. 16
Thesis aims and importance ................................................................................................. 19
Overview of methodologies used ......................................................................................... 19
Field data collection ..................................................................................................... 19
Double digest restriction-site associated DNA (ddRAD) .............................................. 21
Outline of the thesis ............................................................................................................. 22
Chapter 2 - Megafrugivores as fading shadows of the past: extant frugivores and the abiotic environment as the most important determinants of the distribution of palms in Madagascar .................................................................................................................... 25
Chapter 3 - Genomic signatures of past megafrugivore-mediated dispersal in Malagasy palms ............................................................................................................................. 39
Chapter 4 - Insights into the demographic history of Malagasy palms: exploring the role of global change and species-specific characteristics ........................................................... 57
Chapter 5 – General discussion ....................................................................................... 73
Summary and key findings.................................................................................................... 73
The fate of megafruited plants in the post-megafrugivore era ........................................... 74
Vulnerability and resilience in megafruited plants .............................................................. 76
Understanding the complex role of humans in the distribution and genetics of megafruited plants ……………………………………………………………………………………………………………………………..77
The influence of abiotic factors over the distribution and genetics of Malagasy palms ..... 78
Outlook ................................................................................................................................. 79
References ...................................................................................................................... 83
Appendix ...................................................................................................................... 101
Appendix Chapter 2 ............................................................................................................ 101
Appendix Chapter 3 ............................................................................................................ 123
6
Appendix Chapter 4 ............................................................................................................ 145
Summary ...................................................................................................................... 159
Zusammenfassung ........................................................................................................ 163
Acknowledgments ........................................................................................................ 169
Curriculum Vitae ..................................................................................................................... 171
List of publications and scientific presentations .................................................................... 171
Selbstständigkeitserklärung……………………………………………………………………………………….……..168
| Identifer | oai:union.ndltd.org:DRESDEN/oai:qucosa:de:qucosa:90769 |
| Date | 05 April 2024 |
| Creators | Méndez Cuéllar, Laura |
| Contributors | Universität Leipzig |
| Source Sets | Hochschulschriftenserver (HSSS) der SLUB Dresden |
| Language | English |
| Detected Language | English |
| Type | info:eu-repo/semantics/acceptedVersion, doc-type:doctoralThesis, info:eu-repo/semantics/doctoralThesis, doc-type:Text |
| Rights | info:eu-repo/semantics/openAccess |
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