Fig tree breeding reveals surprising genetic exchange between different habitats

Jenn Hoskins
27th December, 2025

Fig tree breeding reveals surprising genetic exchange between different habitats

The ecologically distinct parent species, the riparian shrub Ficus squamosa (a–c) and the generalist tree Ficus hispida (d–f), produce morphologically intermediate hybrid offspring (g–i) in locations where they grow sympatrically (j).

Image adapted from: Kohkaew et al. / CC BY (Source)

Key Findings

  • In Thailand, fig trees Ficus hispida and F. squamosa can interbreed, creating hybrid offspring despite differing habitats
  • Genetic analysis confirms hybrids exist, showing a mix of genes from both parent species and evidence of ongoing backcrossing, primarily with F. hispida
  • Hybrids are found in areas with intermediate conditions, suggesting they adapt to environments between the drier F. hispida and wetter F. squamosa habitats
Hybridization, the interbreeding of different species, is a complex process with a significant but often poorly understood role in the formation of new species and the maintenance of boundaries between existing ones[2]. While hybridization is known to occur in plants, particularly due to their diverse pollination strategies, the extent to which it shapes the evolution of ecologically important groups like fig trees has remained unclear. A recent study by researchers at the Chinese Academy of Sciences[1] investigated hybridization between two fig tree species, Ficus hispida and Ficus squamosa, to better understand the mechanisms governing species boundaries and the potential for gene flow between them. Ficus hispida and Ficus squamosa are both dioecious, meaning individual trees are either male or female, and they occupy different habitats. F. hispida favors drier, more open environments, while F. squamosa thrives in riparian areas – habitats along rivers and streams. A key difference between the species is their seed dispersal method: F. squamosa seeds are adapted for water dispersal, while F. hispida relies on vertebrates. Fig trees have a highly specialized pollination system, relying on fig wasps that typically co-evolve with a single fig species, but some level of host switching is known to occur. The researchers hypothesized that overlapping fruiting periods during the rainy season could allow for cross-pollination between the two species. To test this, they combined multiple lines of evidence: detailed observations of flowering and fruiting times (phenology), measurements of physical characteristics (morphology), and analysis of genetic data. They identified individuals that appeared to be hybrids based on intermediate morphological traits – specifically, larger leaves compared to either parent species. Genomic analysis, focusing on variations in single nucleotide polymorphisms (SNPs) – differences in individual DNA building blocks – confirmed the hybrid status of these individuals. The genetic data showed a mixture of genetic material from both parent species, indicating successful interbreeding. Further analysis of chloroplast DNA, which is inherited maternally, revealed evidence of historical introgression – the transfer of genetic material from one species into the gene pool of another[2]. Interestingly, the hybrids were primarily found in riparian habitats, suggesting a preference for conditions intermediate between those favored by the two parent species. The hybrids also exhibited a reduced ability to disperse seeds via water, indicating a reliance on animal dispersal, similar to F. hispida. This suggests that the hybrids may be adapting to a different dispersal strategy than either parent species. The study provides strong evidence that hybridization does occur between F. hispida and F. squamosa. However, the long-term evolutionary consequences of this gene flow remain uncertain.[2] highlights that hybridization can either strengthen species boundaries through selection against unfit hybrids or lead to the breakdown of those boundaries through the creation of new, viable hybrid lineages. The observed pattern of hybrid distribution – in intermediate habitats – aligns with theoretical expectations and empirical evidence suggesting that hybridization is more likely to be successful when environmental conditions favor intermediate forms[2]. The limited aquatic dispersal ability of the hybrids is also noteworthy, potentially representing a constraint on their ability to colonize habitats suitable for F. squamosa. While the number of reported hybrid zones in plants is surprisingly low given their propensity to hybridize[3], this study demonstrates that hybridization can occur even in the absence of a clearly defined hybrid zone. The researchers acknowledge the need for further investigation to determine whether these hybrids are reproductively isolated from both parent species, which would indicate the potential for the formation of a new species. Furthermore, understanding the specific genetic mechanisms underlying hybrid compatibility and the fitness of hybrid offspring is crucial for unraveling the evolutionary significance of hybridization in fig trees and other plant groups. The research on Glochidion trees and their associated moths[4] illustrates that even in highly coevolved systems, host shifts and hybridization can occur, adding complexity to the process of speciation.

EcologyPlant ScienceEvolution

References

Main Study

1) Hybridization and introgression between two fig trees with contrasting ecological preferences

Published 24th December, 2025

https://doi.org/10.1186/s12862-025-02476-7

Related Studies

2) Hybridization and speciation.

https://doi.org/10.1111/j.1420-9101.2012.02599.x

3) The puzzle of plant hybridisation: a high propensity to hybridise but few hybrid zones reported.

https://doi.org/10.1038/s41437-023-00654-1

4) Cospeciation analysis of an obligate pollination mutualism: have Glochidion trees (Euphorbiaceae) and pollinating Epicephala moths (Gracillariidae) diversified in parallel?

Journal: Evolution; international journal of organic evolution, Issue: Vol 58, Issue 10, Oct 2004


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