The island syndrome in birds
Islands are home to some of the most unique and threatened groups of organisms in the world. The distinctiveness and vulnerability of island species stems from their adaptations to insular environments. Meanwhile, the similarity of different island environments can lead to the repeated evolution of...
| Main Author: | |
|---|---|
| Other Authors: | |
| Format: | Thesis |
| Language: | English |
| Published: |
2024
|
| Subjects: |
| _version_ | 1811141337138855936 |
|---|---|
| author | Jezierski, MT |
| author2 | Saupe, E |
| author_facet | Saupe, E Jezierski, MT |
| author_sort | Jezierski, MT |
| collection | OXFORD |
| description | Islands are home to some of the most unique and threatened groups of organisms in the world. The distinctiveness and vulnerability of island species stems from their adaptations to insular environments. Meanwhile, the similarity of different island environments can lead to the repeated evolution of similar forms on different islands, despite taxonomic differences and distinct community compositions. This pattern of independent acquisition of similar morphological, ecological, and behavioural characteristics in island taxa is known as the ‘island syndrome’. The island syndrome is thought to evolve due to the dual limitations of area and isolation, creating communities with low predation and interspecific competition, leading to the evolution of, among other traits, ‘slow’ life histories, generalist strategies, and intermediate body sizes. Although the island syndrome is considered a global phenomenon, evidence for its taxonomic, morphological, and geographical generality is lacking. Here, I summarise the scope of the island syndrome focusing on a particular taxonomic group – birds (<strong>Chapter 1</strong>). I review the level of support for the island syndrome, and the extent of biological traits involved, showing that, beyond body size, most island adaptations are poorly understood, particularly with respect to behavioural and life history traits. Furthermore, I find that most studies are focused on small sample sizes, and do not utilise phylogenetic comparative methods, which are critical to accurately study trait evolution across hundreds of species. Following these findings, my empirical work focuses on investigating two reproductive traits in birds – clutch size and nest architecture. Clutch size has been at the forefront of avian life history research since David Lack’s studies, and its variation has significant consequences for animal fitness. I explored variation in clutch size for some 4,500 bird species, to examine whether average clutch size differs between island and continental species (<strong>Chapter 2</strong>). I found that clutches on islands tend to be smaller, which is consistent with the ‘slowing down’ of life histories, and that this effect persists across both land birds and seabirds. The latter have traditionally been ignored in island syndrome studies, but my work demonstrates they undergo the same changes as land birds. Nest architecture has also been poorly explored in a macro-evolutionary context. As a result, it is unclear which aspects of the environment shape nest architecture, with a long-standing debate on the importance of abiotic versus biotic factors. I have collected nest architecture data for all bird species in the world, and I show that biotic interactions (approximated by predator diversity) are the predominant drivers of nest variation (<strong>Chapter 3</strong>). Island endemicity is also a significant predictor of nest architecture, resulting in the evolution of ‘simpler’ nests. Finally (<strong>Chapter 4</strong>), I explore the island diversification of Eurasian Wrens (<em>Troglodytes troglodytes</em>) in the British Isles. This study focusses on a particular set of populations to i) characterise the phylogenetic relationships between geographically distinct populations; ii) characterise the evolution of Wrens with respect to morphology and song; and iii) explore the genomic patterns of divergence between island populations. To this end, I have collected morphological, song, and genetic data for the five subspecies of British wrens: <em>Troglodytes troglodytes troglodytes indigenus</em> (most of the British Isles), <em>hebridensis</em> (Outer Hebrides), <em>hirtensis</em> (St Kilda), <em>zetlandicus</em> (Shetland) and <em>fridariensis</em> (Fair Isle). I show that the British Isles contain three distinct lineages of Wrens: one in Shetland, one of the British and Hebridean subspecies, and within that, the strongly divergent St Kilda Wrens. The Shetland and St Kilda Wrens show considerable morphological convergence, despite vocal and genetic divergence. I show they share patterns of genetic evolution, including apparent differentiation in a genomic region containing the same gene. Overall, my work provides a thorough description of the avian island syndrome, and highlights research gaps which will help to delineate its drivers. |
| first_indexed | 2024-09-25T04:36:16Z |
| format | Thesis |
| id | oxford-uuid:869fb206-522c-4380-99e3-1c7bcf5881ae |
| institution | University of Oxford |
| language | English |
| last_indexed | 2024-09-25T04:36:16Z |
| publishDate | 2024 |
| record_format | dspace |
| spelling | oxford-uuid:869fb206-522c-4380-99e3-1c7bcf5881ae2024-09-23T16:28:11ZThe island syndrome in birdsThesishttp://purl.org/coar/resource_type/c_db06uuid:869fb206-522c-4380-99e3-1c7bcf5881aeIsland biogeographyEnglishHyrax Deposit2024Jezierski, MTSaupe, EBenson, RClegg, SIslands are home to some of the most unique and threatened groups of organisms in the world. The distinctiveness and vulnerability of island species stems from their adaptations to insular environments. Meanwhile, the similarity of different island environments can lead to the repeated evolution of similar forms on different islands, despite taxonomic differences and distinct community compositions. This pattern of independent acquisition of similar morphological, ecological, and behavioural characteristics in island taxa is known as the ‘island syndrome’. The island syndrome is thought to evolve due to the dual limitations of area and isolation, creating communities with low predation and interspecific competition, leading to the evolution of, among other traits, ‘slow’ life histories, generalist strategies, and intermediate body sizes. Although the island syndrome is considered a global phenomenon, evidence for its taxonomic, morphological, and geographical generality is lacking. Here, I summarise the scope of the island syndrome focusing on a particular taxonomic group – birds (<strong>Chapter 1</strong>). I review the level of support for the island syndrome, and the extent of biological traits involved, showing that, beyond body size, most island adaptations are poorly understood, particularly with respect to behavioural and life history traits. Furthermore, I find that most studies are focused on small sample sizes, and do not utilise phylogenetic comparative methods, which are critical to accurately study trait evolution across hundreds of species. Following these findings, my empirical work focuses on investigating two reproductive traits in birds – clutch size and nest architecture. Clutch size has been at the forefront of avian life history research since David Lack’s studies, and its variation has significant consequences for animal fitness. I explored variation in clutch size for some 4,500 bird species, to examine whether average clutch size differs between island and continental species (<strong>Chapter 2</strong>). I found that clutches on islands tend to be smaller, which is consistent with the ‘slowing down’ of life histories, and that this effect persists across both land birds and seabirds. The latter have traditionally been ignored in island syndrome studies, but my work demonstrates they undergo the same changes as land birds. Nest architecture has also been poorly explored in a macro-evolutionary context. As a result, it is unclear which aspects of the environment shape nest architecture, with a long-standing debate on the importance of abiotic versus biotic factors. I have collected nest architecture data for all bird species in the world, and I show that biotic interactions (approximated by predator diversity) are the predominant drivers of nest variation (<strong>Chapter 3</strong>). Island endemicity is also a significant predictor of nest architecture, resulting in the evolution of ‘simpler’ nests. Finally (<strong>Chapter 4</strong>), I explore the island diversification of Eurasian Wrens (<em>Troglodytes troglodytes</em>) in the British Isles. This study focusses on a particular set of populations to i) characterise the phylogenetic relationships between geographically distinct populations; ii) characterise the evolution of Wrens with respect to morphology and song; and iii) explore the genomic patterns of divergence between island populations. To this end, I have collected morphological, song, and genetic data for the five subspecies of British wrens: <em>Troglodytes troglodytes troglodytes indigenus</em> (most of the British Isles), <em>hebridensis</em> (Outer Hebrides), <em>hirtensis</em> (St Kilda), <em>zetlandicus</em> (Shetland) and <em>fridariensis</em> (Fair Isle). I show that the British Isles contain three distinct lineages of Wrens: one in Shetland, one of the British and Hebridean subspecies, and within that, the strongly divergent St Kilda Wrens. The Shetland and St Kilda Wrens show considerable morphological convergence, despite vocal and genetic divergence. I show they share patterns of genetic evolution, including apparent differentiation in a genomic region containing the same gene. Overall, my work provides a thorough description of the avian island syndrome, and highlights research gaps which will help to delineate its drivers. |
| spellingShingle | Island biogeography Jezierski, MT The island syndrome in birds |
| title | The island syndrome in birds |
| title_full | The island syndrome in birds |
| title_fullStr | The island syndrome in birds |
| title_full_unstemmed | The island syndrome in birds |
| title_short | The island syndrome in birds |
| title_sort | island syndrome in birds |
| topic | Island biogeography |
| work_keys_str_mv | AT jezierskimt theislandsyndromeinbirds AT jezierskimt islandsyndromeinbirds |