Figs are among the most diverse and widespread groups of plants in the world, with more than 850 species in the genus Ficus.
Figs are also ecologically important, providing food and shelter for many animals, including birds, bats, monkeys, and insects.
Figs have a unique pollination system, involving a mutualistic relationship with tiny wasps that enter the fig's hollow inflorescence and lay eggs inside some of the flowers, while also transferring pollen from one fig to another.
The evolution of figs has been a topic of interest and debate for many researchers, who have tried to explain how this plant group achieved such remarkable diversity and adaptation.
A recent study by an international team of researchers, including a Northwestern University plant biologist, has shed new light on the evolutionary history of figs by examining their genetic variation across 520 species.
The study was published earlier this month in the Proceedings of the National Academy of Sciences.
How gene sharing contributed to fig diversity
FETHI BELAID/AFP via Getty Images
One of the hypotheses that previous researchers have proposed to account for fig diversity is that gene sharing across fig species played a major role in their evolution, as per Phys.org.
Gene sharing, also known as introgression or hybridization, is a process in which genes are transferred from one species to another through interbreeding. Gene sharing can increase genetic variation and facilitate adaptation to new environments or niches.
The researchers tested this hypothesis by analyzing 1,858 genes from 520 fig species, representing all major lineages of the genus.
They used statistical methods to detect signals of gene sharing and to estimate its extent and frequency across the fig tree of life.
The researchers found that gene sharing did occur among some fig species, but it was not widespread or frequent enough to explain their diversity.
Gene sharing only accounted for about 6% of the genetic variation among fig species, and it mostly occurred within closely related groups or geographic regions.
Gene sharing did not significantly affect the phylogenetic relationships or divergence times among fig lineages.
The researchers suggested that gene sharing may have been limited by several factors, such as the specificity of the fig-wasp pollination system, the rarity of hybridization events, and the low fitness or fertility of hybrid offspring.
The researchers concluded that gene sharing was not a major driver of fig diversity and that other factors must have played a more important role in their evolution. They proposed that figs diversified mainly through speciation, which is the process by which new species arise from existing ones due to reproductive isolation or ecological divergence.
The researchers suggested that speciation in figs may have been influenced by various factors, such as geographic isolation, climate change, habitat fragmentation, host-plant shifts, pollinator shifts, and coevolution with other organisms.
These factors may have created opportunities for figs to adapt to different environments and niches, resulting in their remarkable diversity.
The researchers also highlighted the role of coevolution between figs and their pollinating wasps in shaping their evolution.
Figs and wasps have a long and intricate history of coevolution, involving reciprocal adaptations and mutual dependence.
The researchers found that the diversification patterns of figs and wasps were largely congruent, indicating that they diversified together in response to similar factors.
The researchers emphasized that their study provides a comprehensive and robust framework for understanding the evolution of figs and their pollinators.
They also recommended that future studies should explore the genomic and functional aspects of gene sharing and speciation in figs, as well as the ecological and biogeographical factors that affect their diversity.
