Data from: Ancestral state reconstruction sheds new light on the loss of divarication hypothesis on New Zealand’s outlying islands
Data files
Mar 25, 2025 version files 1.74 MB
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README.md
1.30 KB
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Supplementary_2_Data.xlsx
1.74 MB
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Supplementary_3_Supplementary_tables.csv
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Abstract
The New Zealand flora is remarkable in many respects, but one of its most notable features is the convergent evolution of many plant lineages toward a divaricate habit. The adaptive significance of divarication remains controversial, but it has usually been considered a response to harsh climates or a defence mechanism against the diverse array of Ratites (large browsing birds) that once populated New Zealand. The loss of divarication hypothesis posits that divaricate-related traits should be lost on New Zealand’s outlying islands, as these islands were never reached by Ratites. Like most evolutionary components of the island syndrome, this hypothesis was tested through the pairwise comparison method, i.e. by comparing traits of island endemics to those of their closest relative(s) on the mainland, assuming that the most recent common ancestor (MRCA) was divaricate. This assumption was challenged by recent results but has never been tested. Here, we test this assumption. We collated data for all but one genus comprising at least one divaricate species and one island endemic in the New Zealand region. We used ancestral range reconstruction to determine which endemics colonized the islands from New Zealand. We then used ancestral state reconstruction to test whether each MRCA was divaricate and to quantify the degree of morphological evolution in leaf size and branching angle (i.e. significant divaricate traits) on islands. 21 out of 29 MRCAs were estimated as most likely non-divaricate, meaning that in most cases divarication evolved on the mainland and was never present on New Zealand’s outlying islands. Island endemics also evolved larger leaves and smaller branching angles regardless of whether the MRCA was divaricate or not.
Synthesis. These findings show how most island lineages were never divaricate, and advance our understanding of the evolution of divarication in the New Zealand region. In addition, they have broader implications for the field of island biogeography, as they highlight the limits of the pairwise comparison method and provide a way to overcome them.
https://doi.org/10.5061/dryad.ncjsxkt6p
Description of the data and file structure
Data collected and supplemental information produced to test the loss of divarication hypothesis on New Zealand’s outlying islands
Data and supplemental information
File: Supplementary_1_Supplemental_information.docx
Description: Supplementary figures and Trees showing the results of ancestral area reconstruction
File: Supplementary_2_Data.xlsx
Description: Data used for the analysis. Species list and traits data, along with a list of herbarium specimens from which the traits were measured. Trait data could not be obtained for species absent from the herbaria. Missing values are indicated with n/a
File: Supplementary_3_Supplementary_tables.csv
Description: Supplementary tables
Variables present in supplementary 2
- Divaricate habit: whether a species is divaricate or not
- Insular endemics: which species are endemic to one of New Zealand’s outlying islands
- Leaf size: average leaf area measured in mm2
- Branching angle: average branching angle measured in decimal degrees