Flower size correlates with pollinator size, evolved independently among mountains

Flower size correlates with pollinator size, evolved independently among mountains
A Bombus consobrinus queen visiting a L. album var. barbatum flower in the Mitsumata population. Credit: Tsubasa Toji, Shinshu University

The morphological compatibility between flowers and insects was given in the famous textbook example of Darwin's orchids and hawkmoths. As in this example, many studies have shown that geographical variations in flower size match the size of insects in each region. In other words, studies have shown 'flower-sized regional adaptation' in which large flowers evolve in areas pollinated by large insects and small flowers evolve in areas pollinated by small insects.

However, when examining the between populations, are plants in each region more similar, or are plants with large (or small) flower sizes across nearing regions more similar? This has remained unknown until this study led by doctoral candidate Tsubasa Toji of Shinshu University's Professor Takao Itino lab. The team used white nettle to show this classic flower-insect size agreement, and by combining genetic analysis, examined the actual evolution of flower size.

The flower traits of white dead-nettle (Lamium album var. barbatum) were clearly correlated with bee size. On the other hand, the was similar between plants of each region. In other words, the flower size was independently large and small in each area or a parallel evolution of flower size developed independently between mountain areas.

This study was conducted very simply, combining two methods: and population genetic analysis. Field studies showed geographical variation in flower size, showing that flower size was clearly correlated with the bee size visited in the population. Genetic analysis showed that there is an overarching genetic structure or genetic divergence between mountains.

When the two results are combined, the flower size of each population is independent of the genetic structure, and the flower size differs greatly even between genetically similar populations, or groups belonging to the same mountain range. In some cases, flower sizes were similar even between populations that were genetically distant, or species belonging to different mountain areas. This suggests that flower size evolved independently in each mountain area.

The group is in the process of confirming the parallel evolution of flower traits between mountainous areas for other plant species using the same approach. They are also trying to find out about other plant species and are exploring the possibility that the parallel evolution of this flower trait between mountains is a fairly common phenomenon. Ultimately, by extending the trait comparison between mountain areas to organisms of other taxa other than plants and combining it with population , they hope to elucidate the actual state of evolution of various species occurring in mountain regions.


Explore further

Plant provenance influences pollinators

More information: Tsubasa Toji et al, Intraspecific convergence of floral size correlates with pollinator size on different mountains: a case study of a bumblebee-pollinated Lamium (Lamiaceae) flowers in Japan, BMC Ecology and Evolution (2021). DOI: 10.1186/s12862-021-01796-8
Journal information: BMC Ecology and Evolution

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Citation: Flower size correlates with pollinator size, evolved independently among mountains (2021, May 10) retrieved 16 June 2021 from https://phys.org/news/2021-05-size-pollinator-evolved-independently-mountains.html
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