In situ radiation explains the frequency of dioecious palms on islands
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2021
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• Background and Aims Dioecy has evolved up to 5000 times in angiosperms, despite the potentially high intrinsic
costs to unisexuality. Dioecy prevents inbreeding, which is especially relevant on isolated islands when
gene pools are small. Dioecy is also associated with certain dispersal traits, such as fruit size and type. However,
the influence of dioecy on other life history traits and island distribution remains poorly understood. Here, we test
the effect of dioecy on palm (Arecaceae) speciation rates, fruit size and frequency on islands.
• Methods We used phylogenetic comparative methods to estimate the ancestral state of the sexual system and
its impact on speciation rates and fruit size. Frequency of sexual systems, effect of insularity on the probability of
being dioecious, and phylogenetic clustering of island dioecious vs. mainland species were inferred. Lastly, we
determined the interplay of insularity and sexual system on speciation rates.
• Key Results Palms repeatedly evolved different sexual systems (dioecy, monoecy and polygamy) from a hermaphrodite
origin. Differences in speciation rates and fruit size among the different sexual systems were not identified. An effect
of islands on the probability of the palms being dioecious was also not found. However, we found a high frequency and
phylogenetic clustering of dioecious palms on islands, which were not correlated with higher speciation rates.
• Conclusions The high frequency and phylogenetic clustering may be the result of in situ radiation and suggest
an ‘island effect’ for dioecious palms, which was not explained by differential speciation rates. This island effect
also cannot be attributed to long-distance dispersal due to the lack of fruit size difference among sexual systems,
and particularly because palm dispersal to islands is highly constrained by the interaction between the sizes of fruit
and frugivores. Taken together, we suggest that trait flexibility in sexual system evolution and the in situ radiation
of dioecious lineages are the underlying causes of the outstanding distribution of palms on islands.
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Arecaceae, Sexual system evolution, Dioecy, Macroevolution, Monoecy, Fruit size, Hermaphroditism, Island rule
Citação
CÁSSIA-SILVA, Cibele; FREITAS, Cíntia G.; JARDIM, Lucas; BACON, Christine D.; COLLEVATTI, Rosane G. In suti radiation explains the frequency of dioecious palms on islands. Annals of Botany, Oxford, v. 128, n. 2, p. 205-215, 2021. DOI: 10.1093/aob/mcab056. Disponível em: https://academic.oup.com/aob/article/128/2/205/6265262. Aceso em: 9 mar. 2023.